| 1. |
- Adeyemi, David, et al.
(författare)
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Electrospun Nanofibers Sorbents for Pre-Concentration of 1,1-dichloro-2,2 bis-(4-chlorophenyl)ethylene with Subsequent Desorption by Pressurized Hot Water Extraction
- 2011
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Ingår i: Chromatographia. - : Springer Science and Business Media LLC. - 0009-5893 .- 1612-1112. ; 73:9-10, s. 1015-1020
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Tidskriftsartikel (refereegranskat)abstract
- Electrospun polystyrene (PS) nanofibers (130-500 nm) incorporating a potassium salt of imidazole-1-carbodithioate were evaluated as potential sorbents for the pre-concentration of a model organochlorine pesticide; 1,1-dichloro-2,2bis-(4-chlorophenyl)ethylene (DDE). The efficiencies of DDE (0.25-1.0 mu g L-1) adsorption by the nanofiber sorbent followed by desorption employing pressurized hot water extraction (PHWE) were investigated and monitored using gas chromatography with electron capture detection (GC-ECD). Parameters such as time, temperature and pressure of extraction, sample volume, DDE concentration and sorbent mass were optimized. The maximum adsorption of DDE (0.50 mu g L-1) on electrospun PS and carbodithioate incorporated PS nanofibers was at 43.7 and 94.6%, respectively, in 20 min. Incorporation of carbodithiote doubled the adsorption efficiency of PS and achieved LOD of 0.000234 mu g L-1 for DDE. The optimal DDE desorption on the PHWE system was 93.8% in 10 min. It would seem that the use of electrospun nanofibers as sorbent material with subsequent desorption by PHWE has great potential and thus warrants further investigations. This approach as it uses water as an extraction solvent for an organochlorine pesticide provides an opportunity to eliminate organic solvents, especially for procedures aimed at monitoring organic pollutants in the environment.
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| 2. |
- Amini, A., et al.
(författare)
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Determination of Ephedrine, Pseudo-Ephedrine and Caffeine in a Dietary Product by Capillary Electrophoresis
- 2006
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Ingår i: Chromatographia. - : Springer Science and Business Media LLC. - 0009-5893 .- 1612-1112. ; 63:3/4, s. 143-148
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Tidskriftsartikel (refereegranskat)abstract
- This paper reports the determination of caffeine, ephedrine and pseudo-ephedrine in a dietary product by two rapid and simple methods utilising capillary electrophoresis (CE). The solutes were extracted from the product using 0.2 M HCl and determined by CE with background electrolytes containing 7.5% highly sulfated-β-cyclodextrin (7–11 sulfate groups per β-CD molecule) at pH 2.5 and pH 7.6. Determination of ephedrine and pseudo-ephedrine was accomplished at pH 2.5 with the anode at the detection side of the capillary whereas caffeine was quantified at pH 7.6 with a normal electrophoresis polarity mode. Triethanolamine was added to the running buffer at pH 2.5 in order to reverse the electroosmotic flow (EOF) and thereby speed up the separation of ephedrine and pseudo-ephedrine.
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| 3. |
- Andersson, LI, et al.
(författare)
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Towards molecular-imprint based SPE of local anaesthetics
- 2002
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Ingår i: Chromatographia. - 0009-5893. ; 55, s. 65-69
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Tidskriftsartikel (refereegranskat)abstract
- The use of imprinted polymers for selective solid-phase extraction of local anaesthetics from human plasma was investigated. Methacrylic acid-ethylene glycol dimethacrylate based MIPs were developed by the alternative template approach using a structural analogue, pentycaine, as the template. The influence of the type and concentration of detergent in the buffer on selective and non-specific binding was investigated. Tween 20, Triton X-100 and Brij 35 were found to eliminate non-specific adsorption and leave selective imprint-onalyte binding essentially unaffected. Efficient pre-concert ration of ropivacaine and bupivacaine from plasma samples, both off-line prior to GC and in-line with LC-MS-MS, was demonstrated.
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| 4. |
- Barri, Thaer, et al.
(författare)
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Supported liquid membrane work-up of blood plasma samples coupled on-line to liquid chromatographic determination of basic antidepressant drugs
- 2004
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Ingår i: Chromatographia. - 0009-5893. ; 59:3-4, s. 161-165
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Tidskriftsartikel (refereegranskat)abstract
- An automated sample pretreatment of human blood plasma for liquid chromatographic determination of three antidepressant drugs, dibenzepine; a tricyclic antidepressant (TCA), reboxetine; a selective noradrenaline reuptake inhibitor (SNRI) and fluvoxamine; a selective serotonin reuptake inhibitor (SSRI), based on supported liquid membrane (SLM) for unsurpassed sample clean-up and analyte enrichment, has been developed. The chromatograms after enrichment of plasma blank and aqueous blank are virtually indistinguishable. The entire analytical procedure revealed good linearity and low detection limits of 5, 15 and 20 ng mL(-1) for dibenzepine, reboxetine and fluvoxamine, respectively. No carry-over effects were noted. The repeatability of extraction at three concentrations in the range 40-150 ng mL(-1) for the three drugs was between ca. 3% and 7% as relative standard deviation. The reproducibility relative standard deviation during three different days (replacing the membrane each day) was not significantly higher.
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| 5. |
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| 6. |
- Burestedt, E., et al.
(författare)
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Optimisation and validation of an automated solid phase extraction technique coupled on-line to enzyme-based biosensor detection for the determination of phenolic compounds in surface water samples
- 1995
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Ingår i: Chromatographia. - Heidelberg : Springer Berlin/Heidelberg. - 0009-5893 .- 1612-1112. ; 41:3-4, s. 207-215
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Tidskriftsartikel (refereegranskat)abstract
- A fully integrated screening system for phenolic compounds was developed incorporating on-line solid phase extraction, fractionation and biosensor detection. Two different types of biosensors, solid graphite and carbon paste electrodes incorporating the enzyme tyrosinase, were compared and used in the screening system. Interfacing of the solid phase extraction and fractionation with the biosensor detection was given special attention since the biosensors were not compatible with the organic modifier used for desorption of phenols from the solid phase extraction step. The system was validated with conventional analytical techniques. Surface water samples from the Ebro river were spiked with 1,10, and 25μg L−1 of catechol, phenol,p-cresol, respectively. Three out of seven samples were spiked and the correct samples were identified, containing phenols equivalent to the spiked concentrations. © 1995 Friedr. Vieweg & Sohn Verlagsgesellschaft mbH.
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| 7. |
- Bylund, Dan, et al.
(författare)
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Optimisation of chromatographic separations by use of a chromatographic response function, empirical modelling and multivariate analysis
- 1997
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Ingår i: Chromatographia. - 0009-5893. ; 44:1/2, s. 74-80
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Tidskriftsartikel (refereegranskat)abstract
- The chiral separation of the drug substance R,S-oxybutynin chloride on a reversed phase HPLC system has been optimised by use of empirical modelling and multivariate analysis. The separation was characterised by a new chromatographic response function developed to modulate both quality of separation and retention time. The study includes a comparison between three different multivariate techniques (multi-layer feed-forward neural networks, multiple linear regression and partial least squares regression) of their capabilities to model the new chromatographic response function and predict its value for new experiments. It was indicated that the most accurate models were achieved with neural networks, although partial least squares regression could also be used to solve the problem since it gives the major directions for the optimal settings of the variables.
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| 8. |
- Bång, Joakim, et al.
(författare)
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Blue Chitin columns for the extraction of heterocyclic amines from urine samples
- 2004
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Ingår i: Chromatographia. - : Springer Science and Business Media LLC. - 0009-5893 .- 1612-1112. ; 60:11-12, s. 651-655
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Tidskriftsartikel (refereegranskat)abstract
- During normal cooking of meat, a class of mutagenic/carcinogenic compounds called heterocyclic amines is formed. Heterocyclic amines are rapidly absorbed and metabolised in the human body, and for estimation of the intake of heterocyclic amines, it is useful to determinate their levels in the urine. Blue Chitin columns were used for the extraction and purification of heterocyclic amines from urine samples spiked with 14 different heterocyclic amines. The samples were analysed using LC-MS. The results show that Blue Chitin columns provide a straightforward and rapid means of extracting heterocyclic amines from urine samples, and that Blue Chitin column are also useful in the purification of urinary metabolites.
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| 9. |
- Carlsson, Björn, et al.
(författare)
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Optimization and Characterization of the Chiral Separation of Citalopram and its Demethylated Metabolites by Response Surface Methodology
- 2001
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Ingår i: Chromatographia. - 0009-5893. ; 53:5/6, s. 266-272
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Tidskriftsartikel (refereegranskat)abstract
- Response-surface modelling and sequential optimization have been used for optimization and characterization of the separation of the enantiomers of citalopram, desmethylcitalopram, and didesmethylcitalopram on an acetylated ▀-cyclodextrin column. In the model chosen the separation conditions mobile phase methanol content, buffer concentration, column temperature, and pH were varied to investigate their influence on the chromatography. It was found that what is good for selectivity within an enantiomer pair is bad for selectivity between enantiomer pairs. Because within-pair and between-pair selectivity does not reach its optimum at the same conditions, a middle course approach has to be followed. Use of an experimental design for this investigation enabled understanding of the mechanisms of within- and between-pair separation for citalopram, desmethylcitalopram, and didesmethylcitalopram. Sequential optimization can be a quicker means of optimizing a chromatographic separation, response-surface modelling, in addition to enabling optimization of the chromatographic process, also serves as a tool for learning more about the separation mechanism.
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| 10. |
- Cohen, Arieh, et al.
(författare)
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Automated solid-phase extraction and liquid chromatography tandem mass spectrometry determination of N-methyl-2-pyrrolidone and its metabolites in urine and plasma
- 2007
-
Ingår i: Chromatographia. - : Springer Science and Business Media LLC. - 0009-5893 .- 1612-1112. ; 65:7-8, s. 407-412
-
Tidskriftsartikel (refereegranskat)abstract
- A method for the simultaneous determination of N-methyl-2-pyrrolidone (NMP) and its metabolites 5-hydroxyl-N-pyrrolidone (5HNMP), N-methylsuccinimide (MSI) and 2-hydroxy-N-methylsuccinimide (2HMSI) in plasma and urine has been developed. Samples were purified by SPE using an ASPEC XL4. Analysis was performed using LC-MS equipped with an APCI interface. The analysis provided linear responses in the range of 0.125-12 mu g mL(-1) for all of the analytes and up to 150 mu g mL(-1) for 5HNMP and 2HMS1. The within day precision was in the range of 0.9-19.1% for plasma samples and 1.9-10.4% for urine samples whereas the between day precisions were 4.5-11.9% and 1.2-17.5%, respectively. The method was deemed to be suitable for monitoring the levels of NMP and its metabolites in the plasma and urine of occupationally exposed persons.
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| 11. |
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| 12. |
- Farajzadeh, M. A., et al.
(författare)
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Liquid-gas-liquid microextraction as a simple technique for the extraction of 2,4-di-tert-butyl phenol from aqueous samples
- 2007
-
Ingår i: Chromatographia. - : Springer Science and Business Media LLC. - 0009-5893 .- 1612-1112. ; 66:5-6, s. 415-419
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Tidskriftsartikel (refereegranskat)abstract
- A solvent-free microextraction technique based on liquid-gas-liquid microextraction was investigated for the extraction and preconcentration of 2,4-di-tert-butyl phenol from aqueous samples. In this study 16 mu L NaOH 1 M as acceptor phase was introduced in the lumen of a polypropylene hollow fiber, with one of its ends heat-sealed. A small piece (about 2 cm) of metallic wire was used to seal the other end of hollow fiber after introducing acceptor phase and before immersing of hollow fiber into the analyte solution. This configuration eliminated the need for a holder. The extraction procedure is simple and there is no necessity to adjust pH, salt content, temperature, etc. After extraction the acceptor phase was transferred to a 1-mL vial, 50 mu L. 0.5 M phosphoric acid was added and the sample was injected into the HPLC-DAD system. Detection was performed at 280 nm. Limit of detection is 30 ng mL(-1) and the relative standard derivation (n = 6) is 5.0%. An enrichment factor (EF) of about 30 is achievable.
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| 13. |
- Farajzadeh, Mir Ali, et al.
(författare)
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Saponification then GC for determination of Irganox 1010 and Irganox 1076 in a polymer matrix
- 2007
-
Ingår i: Chromatographia. - : Springer Science and Business Media LLC. - 0009-5893 .- 1612-1112. ; 65:3-4, s. 223-227
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Tidskriftsartikel (refereegranskat)abstract
- A gas chromatographic method has been established for determination of Irganox 10 10 and 1076 after saponification. The analytes were saponified with methanolic potassium hydroxide, acidified with hydrochloric acid, and the solvent was removed by rotary evaporation. The dry residue was dissolved in xylene and analyzed by GC with flame-ionization detector (FID). Compounds were separated on a polar (Carbowax 20 M) capillary column and nitrogen was used as carrier gas and make-up gas. This method has a relatively large linear dynamic range, 50-3,000 and 100-1,600 mg L-1 for Irganox 1010 and 1076, respectively, and limits of detection (LOD) were 20 and 40 mg L-1, respectively. The effect of conditions such as saponification temperature, and concentration and volume of potassium hydroxide were studied.
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| 14. |
- Fiedler, Heidelore, 1953-, et al.
(författare)
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Separation and determination of neuraminic acids in nanogram quantities by liquid chromatography : A comparative study with different amino phases
- 1985
-
Ingår i: Chromatographia. - : Springer. - 0009-5893 .- 1612-1112. ; 20:4, s. 231-234
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Tidskriftsartikel (refereegranskat)abstract
- Neuraminic acid derivatives were separated easily by liquid chromatography on amino phases and using acetonitrile/15 mM phosphate buffer, pH 5.2 as mobile phase. Detection at 200 nm allowed determination of substances in the nanomole range. All solvent systems were used isocratically at room temperature. The separation did not depend on ion-exchange but on a partition mechanism, the solutes being separated according to their polarity. Thus, it was possible to optimize the resolution by varying the stationary phase and the composition of the eluent.
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| 15. |
- FRIDSTROM, A, et al.
(författare)
-
MICELLAR ELECTROKINETIC CAPILLARY CHROMATOGRAPHY USING POLYMERIC HOLLOW FIBERS
- 1995
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Ingår i: CHROMATOGRAPHIA. - : FRIEDR VIEWEG SOHN VERLAG GMBH. - 0009-5893. ; 41:5-6, s. 295-300
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- In this paper, polymeric hollow fibers prepared from pH-stable polypropylene were used as columns for micellar electrokinetic capillary chromatography (MECC). The electroosmotic flow (EOF) for polypropylene hollow fibers was evaluated in the pH range of 5
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| 16. |
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| 17. |
- Grimm, C. H., et al.
(författare)
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Selective extraction of small proteins from biological samples using a novel restricted access column with cation exchange properties
- 2000
-
Ingår i: Chromatographia. - 0009-5893. ; 52:11-12, s. 703-709
-
Tidskriftsartikel (refereegranskat)abstract
- The determination of proteins utilising a polymer-based restricted access support material with ion exchange properties (IERAM) is outlined. Solid phase extraction coupled on-line with a microbore reversed phase HPLC system for the quantitation of small marker proteins is demonstrated. The cation-exchange restricted access packings were characterised with respect to their adsorption and desorption kinetics. The IERAM material was also investigated by capacity, selectivity, and biocompatibility determinations when applied to the quantification of small molecular weight proteins such as cytochrome C, Lysozyme, Ribonuclease A, Myoglobin, Insulin, human serum albumin, and a Tryptic inhibitor. The integrated system was coupled to mass identity of selected proteins by MALDI-TOF mass spectrometry. The chromatographic outlet was interfaced to an "Interplate" fractionation collecter that sampled 1 μL volumes directly onto the MALDI target plate. The fully automated coupled column system was run unattended overnight and applied to protein quantitations in human plasma samples. Recovery data for a selected number of proteins varied between 90-96% (n = 10) with a limit of quantification around 2 μM with an injection volume of 100 μL. The RSD data were typically less than 8% at a 50 μM protein level (n = 7).
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| 18. |
- Gu, M., et al.
(författare)
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One-step purification of resveratrol and polydatin from Polygonum cuspidatum (Sieb. & Zucc.) by isocratic hydrogen bond adsorption chromatography on cross-linked 12% agarose
- 2006
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Ingår i: Chromatographia. - : Springer Science and Business Media LLC. - 0009-5893 .- 1612-1112. ; 64:11-12, s. 701-704
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Tidskriftsartikel (refereegranskat)abstract
- Resveratrol and polydatin (piceid), the major active components of the traditional Chinese medicinal herb Polygonum cuspidatum (Sieb. & Zucc.), have been separated and purified from crude root extracts in one step by isocratic hydrogen bond adsorption chromatography on cross-linked 12% agarose (Superose™ 12 HR 10/30). Separation was achieved by step-wise elution with mobile phases composed of mixtures of ethanol and acetic acid: 0–75 mL, 10% ethanol, 10% acetic acid; 75–150 mL, 20% ethanol, 20% acetic acid; 150–250 mL, 30% ethanol, 30% acetic acid. At a sample load of 40 mg crude extract dissolved in 0.5 mL mobile phase (corresponding to a load of 1.7 mg mL−1 gel) a resveratrol purity of about 96% with a recovery of 61% was obtained by proper peak cutting.
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| 19. |
- Gu, M., et al.
(författare)
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The Separation of Polyphenols by Isocratic Hydrogen Bond Adsorption Chromatography on a Cross-Linked 12% Agarose Gel
- 2006
-
Ingår i: Chromatographia. - : Springer Science and Business Media LLC. - 0009-5893 .- 1612-1112. ; 64:5-6, s. 247-253
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Tidskriftsartikel (refereegranskat)abstract
- The highly cross-linked 12% agarose gel, Superose™ 12 HR 10/30 is shown to possess hydrogen bond acceptor properties suitable for the separation of polyphenolic solutes such as phenolic acids, flavonols and flavonoids. The separation is achieved isocratically in the presence of solvent mixtures of acetic acid and ethanol. The extent of hydrogen bond adsorption is reviewed based on data obtained from the elution behaviour of a variety of simple polyphenolic solutes including dihydroxybenzoic acids.
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| 20. |
- Gyllenhaal, Olle, et al.
(författare)
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Evaluation Conditions for SFC of Metoprolol and Related Amino Alcohols on Hypercarb (Porous Graphitic Carbon) with Respect to Structure–Selectivity Relations
- 2010
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Ingår i: Chromatographia. - : Springer Science and Business Media LLC. - 0009-5893 .- 1612-1112. ; 71:1-2, s. 7-13
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Tidskriftsartikel (refereegranskat)abstract
- Mobile phase chromatographic conditions for the selective separation of metoprolol from related amino alcohols have been evaluated using Hypercarb as support and carbon dioxide with addition of methanol as mobile phase. The objective for the presented study was to show the unique ability of the porous graphitized carbon surface to separate closely structurally related substances. Experimental results, using Hypercarb and “chromatographic normal phase conditions” (SFC), are presented with focus on how to control retention and to improve peak performance. A high concentration of basic aliphatic amine additive was required in order to elute the amine analytes as symmetrical peaks. N,N-Dimethyloctylamine was preferred over triethylamine since the retention was markedly shorter though the selectivity and resolution were virtually the same. The selectivity can be optimized by altering the temperature of the column. A high selectivity was demonstrated between metoprolol and two homologues with one and two extra methylene groups inserted between the secondary nitrogen atom and the carbon atom with a hydroxyl group attached. The mobile phase flow rate effect the column efficiency only to a minor extent as the steepness of the van Deemter curve for metoprolol was virtually flat in the range studied: 0.5–3.0 mL min−1.
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| 21. |
- Hagberg, Jessika, et al.
(författare)
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Determination of dissociation constants of low molecular weight organic acids by capillary zone electrophoresis and indirect UV detection
- 2002
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Ingår i: Chromatographia. - 0009-5893 .- 1612-1112. ; 56:9-10, s. 641-644
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Tidskriftsartikel (refereegranskat)abstract
- A capillary zone electrophoretic (CZE) method has been developed to determine dissociation constants (pK(a)) for anionic, non-UV absorbing species in the range 3.3-4.3. The procedure was evaluated by determining the ply, for two well-characterised low molecular weight organic acids: formic and lactic acids. The results correspond well with literature values (in parentheses): formic acid 3.71 (3.75) and lactic acid 3.84 (3.85). The pK(a) of two polyhydroxycarboxylic acids were also determined, namely 3.64 for gluconic acid and 3.87 for isosaccharinic acid (only poorly described in the literature).
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| 22. |
- Héberger, K., et al.
(författare)
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Partial least squares modeling of retention data of oxo compounds in gas chromatography
- 2000
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Ingår i: Chromatographia. - 0009-5893 .- 1612-1112. ; 51:9-10, s. 595-600
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Tidskriftsartikel (refereegranskat)abstract
- Partial least squares modeling of latent structures were carried out on a data matrix consisting of Kováts retention indices of 35 aliphatic ketones and aldehydes and their physical characteristics. The retention indices were determined on capillary columns with 4 different stationary phases, namely bonded methyl-{HP-1}, methyl-phenyl- {HP-50} and trifluoropropyl-methyl siloxane {DB-210}, as well as polyethylene glycol {HP-Innovax} at four different temperatures. It was found that ketones and aldehydes cannot be classified on the basis of retention data solely, whereas the physical characteristics (boiling point, molar volume, molecular mass, molar refraction, octanol-water partition coefficient) contain the necessary information for differentiation of the two classes of compounds. The retention index of but-2-enal does not fit into the general trend of aliphatic aldyhydes and ketones. A predictive PLS model was built to estimate retention data of oxo compounds at different temperatures and various stationary phases of different polarity. Cross-validation suggests a good reliability of the results. Characteristic plots (PLS weights, scores) show the similar retention behavior of oxo compounds (Figures 3 and 4).
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| 23. |
- Hjerten, S, et al.
(författare)
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Gels mimicking antibodies in their selective recognition of proteins
- 1997
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Ingår i: CHROMATOGRAPHIA. - : VIEWEG. - 0009-5893. ; 44:5-6, s. 227-234
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- In a previous paper we presented preliminary experiments aimed at the preparation of gel particles with the property to recognize selectively some particular protein (hemoglobin, cytochrome C, transferrin) [1]. Using the same method we show in this articl
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| 24. |
- Hummert, Christian, et al.
(författare)
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Rapid clean-up and effective sample preparation procedure for unambiguous determination of the cyclic peptides microcystin and nodularin
- 1999
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Ingår i: Chromatographia. - 0009-5893 .- 1612-1112. ; 50:3-4, s. 173-180
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Tidskriftsartikel (refereegranskat)abstract
- A new sample preparation strategy has been established to improve the identification and determination of nodularin and microcystins. The sample preparation consisted of enrichment of the analytes by solid phase extraction with C18 cartridges followed by clean-up of the enriched raw extracts by high performance size exclusion gel permeation chromatography. In contrast to established clean-up procedures based on polarity, related distribution of microcystins and nodularin in non-miscible phases (e.g. a C18 cartridge as stationary phase and a water-containing eluent as mobile phase) this strategy separates microcystins from interfering compounds by molecular size differences.The sample preparation procedure can be automated easily and was validated for both water samples as well as raw extracts of algal cells. The method was successfully applied during an experiment with natural algae communities from the Baltic Sea to investigate the influence of different nutrient limitations on toxicity of Nodularia sp..
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| 25. |
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| 26. |
- Jarmeus, Alf, et al.
(författare)
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CE determination of monosaccharides in pulp using indirect detection and curve-fitting
- 2008
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Ingår i: Chromatographia. - : Springer Science and Business Media LLC. - 0009-5893 .- 1612-1112. ; 67:1-2, s. 151-155
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Tidskriftsartikel (refereegranskat)abstract
- In the present work a capillary electrophoretic method for the analysis of monosaccharides utilizing indirect UV-detection has been developed. Different probes for indirect detection have been assessed using model carbohydrate samples. Background electrolytes with or without addition of cetyltrimethylammonium bromide have also been evaluated regarding the separation power. Furthermore, a curve-fitting algorithm has been introduced to increase the separation resolution. The optimized method has been used for analysis of monosaccharides from an acidically hydrolyzed pulp sample.
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| 27. |
- Jastrebova, Jelena, et al.
(författare)
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Comparison of UPLC and HPLC for Analysis of Dietary Folates
- 2011
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Ingår i: Chromatographia. - : Springer Science and Business Media LLC. - 0009-5893 .- 1612-1112. ; 73, s. 219-225
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Tidskriftsartikel (refereegranskat)abstract
- Ultra performance liquid chromatography (UPLC) using small sub-2 mu m particles and high performance liquid chromatography (HPLC) were compared for separation and determination of the most common dietary folates; 5-methyltetrahydrofolate, tetrahydrofolate, 5-formyltetrahydrofolate, 10-formylfolic acid and folic acid. Two UPLC columns-Acquity BEH C(18) and Acquity HSS T3, and two HPLC columns with similar surface chemistry-Xbridge C(18) and Atlantis d18 were tested. When using UPLC, the signal-to-noise ratio could be improved by a factor of 2-50 for different folate derivatives and the run time could be reduced fourfold without sacrificing separation efficiency. The applicability of UPLC to real food samples was demonstrated
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| 28. |
- Jonsson, B A G, et al.
(författare)
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Analysis of 5-hydroxy-N-methyl-2-pyrrolidone and 2-hydroxy-N-methylsuccinimide in plasma
- 1997
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Ingår i: Chromatographia. - 0009-5893. ; 46:3-4, s. 141-144
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Tidskriftsartikel (refereegranskat)abstract
- A method for the determination of 5-hydroxy-N-methyl-2-pyrrolidone (5-HNMP) and 2-hydroxy-N-methylsuccinimide (2-HMSI) in plasma was developed. 5-HNMP and 2-HMSI are metabolites to the widely used organic solvent N-methyl-2pyrrolidone (NMP). The 5-HNMP and 2-HMSI were purified from plasma by C8 solid phase extraction, derivatised by bistrimethylsilyl trifluoroacetamid, and analysed by gas chromatography with mass spectrometric detection. For 5-HNMP, the precision was 2–7 % (120 and 780 ng mL−1) and the detection limit was 6 ng mL−1 (m/z 98). For 2-HMSI, the precision was 2–9 % (160 and 1000 ng mL−1) and the detection limit was 4 ng mL−1 (m/z 144). The method is applicable for analysis of plasma samples from workers exposed to NMP.
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| 29. |
- Jönsson, Bo A, et al.
(författare)
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Determination of hexahydrophthalic and methylhexahydrophthalic acids in urine by gas chromatography-negative-ion chemical-ionisation mass spectrometry
- 1996
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Ingår i: Chromatographia. - 0009-5893. ; 42:11-12, s. 647-652
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Tidskriftsartikel (refereegranskat)abstract
- A method for determining hexahydrophthalic (HHP acid) and methylhexahydrophthalic acids (MHHP acid) from human urine was developed. These acids are metabolites of the highly sensitising hexahydrophthalic anhydride and methylhexahydrophthalic anhydride. The acids were purified from urine by liquid-solid extraction and derivatised with pentafluorobenzyl bromide to the corresponding esters. These were analysed by GC-MS in the negative-ion chemical-ionisation mode with ammonia moderating gas. Deuterium labelled HHP acid and MHHP acid were internal standards. The precision for HHP acid was 3–6% in the range 70–620 ng mL–1 and that for MHHP acid was 2–8% in the range 60–680 ng mL–1. Overall recovery of HHP acid from urine was 74–88% and that for MHHP acid 98–101%. Detection limits were 11 ng HHP acid mL–1 urine and 17 ng MHHP acid mL–1 urine. There were no significant differences between determinations of HHP acid by a previous method and the present method. Some instability of the acids in urine were found after extended storage at –20°C. The method was applicable for determination of HHP acid and MHHP acid from exposed workers.
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| 30. |
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| 31. |
- Karlsson, Anders, et al.
(författare)
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Reversal of Enantiomeric Retention Order by Using a Single N-Derivatized Dipeptide as Chiral Mobile Phase Additive and Porous Graphitised Carbon as Stationary Phase
- 2007
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Ingår i: Chromatographia. - : Springer Science and Business Media LLC. - 0009-5893 .- 1612-1112. ; 66:5-6, s. 349-356
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Tidskriftsartikel (refereegranskat)abstract
- In this work the three dipeptides, Z-l-alanyl-l-glutaric acid (Z-l-ala-l-glu), Z-l-phenylanyl-l-glutaric acid (Z-l-phe-l-glu) and Z-glycyl-l-glutaric acid (Z-gly-l-glu) were tested as chiral counter ions for enantiomeric resolution of amino alcohols. The influence of solute and counter ion structure upon retention and enantioselectivity was evaluated. The chiral counter ions were dissolved in a mixture of polar solvents, i.e., ethyl acetate, methanol and acetonitrile and the achiral solid phase used was porous graphitic carbon, marketed as Hypercarb. The enantioselectivities observed for the tested solutes were highly influenced by the used chiral counter ion structure. For example no enantioselectivity was observed for (R,S)-alprenolol using Z-l-ala-l-glu while a separation factor (α) of 1.59 was obtained using Z-l-phe-l-glu as chiral counter ion. High selectivity factors (α > 2.7) were observed between enantiomers of tertiary amines using Z-l-phe-l-glu as counter ion. Interestingly, the structure of the counter ion, as well as the charge on Z-l-phe-l-glu and the mobile phase solvent composition, influenced the retention order of the enantiomers.
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| 32. |
- Karlsson, Marie, et al.
(författare)
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Solid-phase extraction of polybrominated diphenyl ethers in human plasma : comparison with an open column extraction method
- 2005
-
Ingår i: Chromatographia. - : Springer Science and Business Media LLC. - 0009-5893 .- 1612-1112. ; 61:1-2, s. 67-73
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Tidskriftsartikel (refereegranskat)abstract
- A solid phase extraction (SPE) method in combination with silica gel cleanup to analyse tri-to heptabrominated diphenyl ethers in human plasma was validated. All congeners showed recoveries over 70% except for BDE #183, which showed recoveries around 45%. The method was tested on 21 individual plasma samples which were extracted with both the SPE method and an open column extraction method using Hydromatrix. Method detection limits were of the same order of magnitude for both methods, ranging from 0.0076 to 0.13 ng g−1 (l.w.) depending on the congener. The SPE extraction method meets the demand for a faster, less solvent-and sample-demanding method with lower contamination risk due to fewer steps compared to the open column extraction.
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| 33. |
- Koivisto, P., et al.
(författare)
-
Separation of L-DOPA and four metabolites in plasma using a porous graphitic carbon column in capillary liquid chromatography
- 2002
-
Ingår i: Chromatographia. - 0009-5893 .- 1612-1112. ; 55:1-2, s. 39-42
-
Tidskriftsartikel (refereegranskat)abstract
- Porous graphitic carbon has been successfully used for the separation of L-DOPA and four metabolites (dopamine, 3,4-dihydroxy-phenyl-acetic acid, homovanillic acid and 3-O-methyl-L-DOPA) and with a volatile mobile phase of relatively high percentage organic modifier (methanol-ammonium formate pH 2.9, 60∶40, v/v). The substances were analysed in plasma. Ultrafiltration was used to remove the proteins from the sample and a coupled column system to enrich and perform on-line sample clean up. Both precolumn and separation column of i. d. 0.2 mm were packed with porous graphitic carbon.
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| 34. |
- Lagesson, Verner, et al.
(författare)
-
Qualitative determination of compounds adsorbed on indoor dust particles using GC-UV and GC-MS after thermal desorption
- 2000
-
Ingår i: Chromatographia. - 0009-5893 .- 1612-1112. ; 52:9-10, s. 621-630
-
Tidskriftsartikel (refereegranskat)abstract
- Fifteen indoor dust samples were analysed qualitatively to determine the compounds adsorbed on the surfaces of the particles. The analyses were performed by GC-MS and GC-UV after thermal desorption at 150°C. A total of 192 different compounds with boiling points from about 50°C to 250°C were identified or classified. The results from the two methods, which were carried out under similar conditions of thermal desorption and gas chromatographic separation, were complementary. GC-MS clearly showed better results for non-aromatic compounds such as alkanes, chlorinated hydrocarbons, acids, esters and alcohols, but for aldehydes and compounds containing unconjugated double bonds the two methods were about equally successful. However, for aromatic or conjugated compounds, the GC-UV method had a clear advantage. Also two iodonated compounds were determined only by the GC-UV technique. These findings indicate that the combined use of GC-UV and GC-MS is appropiate for the analysis of chemical compounds adsorbed on indoor dust particles.
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| 35. |
- Larsson, Anders, et al.
(författare)
-
Pseudoparaproteinemia Detected by CE due to Omnipaque™ Infusion : A Case Report
- 2007
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Ingår i: Chromatographia. - : Springer Science and Business Media LLC. - 0009-5893 .- 1612-1112. ; 65:11-12, s. 775-777
-
Tidskriftsartikel (refereegranskat)abstract
- Serum or plasma protein electrophoresis is often performed in clinical laboratories to detect and monitor M-components. During the last decade, capillary electrophoresis (CE) has emerged as an interesting alternative to traditional analysis of serum, plasma and urine proteins by agarose gel electrophoresis. We here report a case of pseudoparaproteinemia detected by capillary electrophoresis after Omnipaque™ (iohexol) infusion in a patient with normal kidney function. It is important for the laboratories to be aware of this source of erroneous results and not misclassify it as monoclonal gammopathies.
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| 36. |
- Lesko, Marek, et al.
(författare)
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Choice of Model for Estimation of Adsorption Isotherm Parameters in Gradient Elution Preparative Liquid Chromatography
- 2015
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Ingår i: Chromatographia. - : Springer Berlin/Heidelberg. - 0009-5893 .- 1612-1112. ; 78:19-20, s. 1293-1297
-
Tidskriftsartikel (refereegranskat)abstract
- The inverse method is a numerical method for fast estimation of adsorption isotherm parameters directly from a few overloaded elution profiles and it was recently extended to adsorption isotherm acquisition in gradient elution conditions. However, the inverse method in gradient elution is cumbersome due to the complex adsorption isotherm models found in gradient elution. In this case, physicochemically correct adsorption models have very long calculation times. The aim of this study is to investigate the possibility of using a less complex adsorption isotherm model, with fewer adjustable parameters, but with preserved/acceptable predictive abilities. We found that equal or better agreement between experimental and predicted elution profiles could be achieved with less complex models. By being able to select a model with fewer adjustable parameters, the calculation times can be reduced by at least a factor of 10.
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| 37. |
- Lestremau, F, et al.
(författare)
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Investigation of artefact formation during analysis of volatile sulphur compounds using solid phase microextraction (SPME)
- 2004
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Ingår i: Chromatographia. - : Springer Science and Business Media LLC. - 0009-5893 .- 1612-1112. ; 59:09-Oct, s. 607-613
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Tidskriftsartikel (refereegranskat)abstract
- The occurrence and origin of artefact formation during the analysis of volatile sulphur compounds in air by PDMS/Carboxen fibre were investigated. Among the studied compounds (hydrogen sulphide, carbon disulphide, diethyl sulphide, methyl ethyl sulphide, isopropanethiol, methanethiol, dimethyl sulphide, dimethyl disulphide, carbonyl sulphide), essentially mercaptans were shown to react to form the corresponding dimers. However, in the presence of several oxygenated and amines compounds which are common components of industrial effluents, no further artefact formation or reaction was noticed. Artefact formation was therefore considered to be independent of the sample matrix. Thermal oxidation occurring during the desorption step in the GC injection port was assessed. As metallic elements were previously suspected to catalyse the reaction, a specially deactivated SPME needle was tested, but no significant difference was noticed compared to the original needle. It was therefore assumed that metallic elements naturally present on Carboxen may act as catalysts. Similar results were obtained by using Carboxen in adsorbent tubes, as artefacts were increased by comparison with Tenax TA and molecular sieve 5A.
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| 38. |
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| 39. |
- Lindh, Christian, et al.
(författare)
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Analysis of methylhexahydrophthalic acid in human urine
- 1996
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Ingår i: Chromatographia. - 0009-5893. ; 43:11-12, s. 668-670
-
Tidskriftsartikel (refereegranskat)abstract
- A method for analysis of urinary methylhexahydrophthalic acid (MHHP acid), a metabolite of the highly sensitising methylhexahydrophthalic anhydride, is described. The method is based on a double liquid-solid extraction of the MHHP acid from urine, esterification with methanol and boron trifluoride catalysis, and analysis with gas chromatography-mass spectrometry in the electron impact mode. The detection limit was 3 ng mL–1 and the precision between 2 and 5% in the range 34 to 340 ng mL–1. The method gave similar results compared to another method. Urine stored for five years at –20°C lost between 38 and 86% of the MHHP acid (range 16–85 ng mL–1).
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| 40. |
- Lutz, Mareike, 1967-, et al.
(författare)
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On-Line Microdialysis-Electrospray Mass Spectrometry for Automated Desalting of Small-Volume Peptide Samples
- 1999
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Ingår i: Chromatographia. - Wiesbaden : Vieweg. - 0009-5893 .- 1612-1112. ; 49:Suppl. 1, s. S28-S34
-
Tidskriftsartikel (refereegranskat)abstract
- Electrospray ionization mass spectrometry (ESI-MS) is an important tool for biomolecule analysis. Because the salt content of small-volume peptide samples can hamper analyte ionization, such samples require treatment before ESI-MS.The approach described here consists in interfacing ESI-MS with on-line microdialysis which affords rapid desalting and buffer-exchange. On-line microdialysis was performed by means of a hollow fiber (i.d. 200 μm) coupled to fused silica capillaries. Peptide samples were introduced into the capillary flow system as plugs and transferred to the dialysis cell and the electrospray by means of hydrodynamic pressure. As a result, the ionization efficiency of peptidic analytes was increased and adduct formation with, e.g., sodium, was reduced owing to reduced levels of nonvolatile salts. The feasibility of on-line microdialysis-ESI-MS is shown with a proteolytic digest originating from two-dimensional gel electrophoresis.
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| 41. |
- Matos, Tiago, et al.
(författare)
-
Capto™ Resins for Chromatography of DNA : A Minor Difference in Ligand Composition Greatly Influences the Separation of Guanidyl-Containing Fragments
- 2016
-
Ingår i: Chromatographia. - : Springer Science and Business Media LLC. - 0009-5893 .- 1612-1112. ; 79:19-20, s. 1277-1282
-
Tidskriftsartikel (refereegranskat)abstract
- The differences in chromatographic behaviour of individual deoxynucleotides as well as small single-stranded and double-stranded DNA molecules have been examined for two resins from the Capto family: Capto Adhere and Capto Q ImpRes. Capto Adhere carries a multimodal ligand which combines strong anion with aromatic recognition, while Capto Q ImpRes is a strong anion exchanger with a chemically similar ligand, but without a phenyl group. The intrinsic differences between single- and double-stranded DNAs are related to charge, hydrophobicity, size and three-dimensional structure. These variations in biophysical properties have been utilized for comparative separations on these two resins. All deoxynucleotides and DNAs tested bound strongly to the chromatographic materials and could be eluted by a linear gradient of increasing NaCl concentration. Capto Q ImpRes provided a recognition for guanylate bases when samples of deoxynucleotides or poly(dG) were examined. This recognition was not observed for Capto Adhere. Another pronounced difference between the resins was observed in the inverted elution of ss- and dsDNA, where ssDNA eluted at 2.88 M NaCl on Capto Adhere, while on Capto Q ImpRes ssDNA eluted already at 1.47 M NaCl. This behaviour can be linked to the presence of the more hydrophobic phenyl group in Capto Adhere, leading to stronger retention of ssDNA molecules, which have a more hydrophobic character due to a higher degree of base exposure.
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| 42. |
- Odham, G., et al.
(författare)
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Mass spectrometric determination of selected microbial constituents using fused silica and chiral glass capillary gas chromatography
- 1982
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Ingår i: Chromatographia. - 0009-5893. ; 16:1, s. 83-86
-
Tidskriftsartikel (refereegranskat)abstract
- Applications of quantitative gas chromatography/mass spectrometry (selected ion monitoring) to clinical and ecological microbiology are described. The technique permits determination of selected microbial metabolites and can be used for the rapid diagnosis of, for example, tuberculosis by ion-focusing of specific branch-chain fatty acids. The technique is also used to determine diaminopimelic and muramic acids, and D- and L-amino acids separated by chiral gas chromatography, in the low picogram range. The latter method has the potential to detect and quantitate microbial populations.
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| 43. |
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| 44. |
- Palm, A, et al.
(författare)
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Microcolumn chromatofocusing using slurry-packed Mono P anion-exchanger beads as chromatographic matrix
- 2003
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Ingår i: Chromatographia. - 0009-5893. ; 58:11-12, s. 707-712
-
Tidskriftsartikel (refereegranskat)abstract
- Chromatofocusing of proteins in a microcolumn format (750 mum i.d.) was evaluated with slurry-packed Mono P anion-exchanger beads (10 pin bead size) as chromatographic matrix. Evaluation was performed with three standard proteins in terms of flow rate, Polybuffer 96-acetic acid, pH 6.0, concentration (eluent buffer strength), and detection limit. A column with the dimension 750 pin i.d. x 50 mm length, a flow rate of 20 muL min(-1),and a 1:10-1:20 Polybuffer 96-acetic acid aqueous dilution showed the best resolution between the proteins. Detection limits were 3 mug mL(-1) for carbonic anhydrase 1 and 6 mug mL(-1) for myoglobin A employing UV-defection at 280 nm.
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| 45. |
- Paul, Prasanta, et al.
(författare)
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Development and Validation of a CE Method for the Determination of Tetracyclines with Capacitively Coupled Contactless Conductivity Detection
- 2019
-
Ingår i: Chromatographia. - : SPRINGER HEIDELBERG. - 0009-5893 .- 1612-1112. ; 82:9, s. 1395-1403
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, a simple and robust capillary electrophoresis method with capacitively coupled contactless conductivity detection ((CD)-D-4) is developed for the determination of the tetracycline antibiotics (1) tetracycline, (2) chlortetracycline and (3) oxytetracycline. An uncoated, fused silica capillary (60.2 cm long, 75 mu m i.d.) and a solution of 50 mM tris(hydroxymethyl) aminomethane, 50 mM l-histidine and 5 mM methyl-beta-cyclodextrin, without pH adjustment (pH 8.76), was used as background electrolyte. Electrophoresis at + 25 kV showed a rapid analysis with sufficient resolution among the three antibiotics in the order of tetracycline, chlortetracycline and oxytetracycline. Successive inter-injection rinsing (20 psi) of the capillary ensured intra- and inter-day repeatability (0.9-2.2% RSD and 2.0-4.5% RSD, respectively, for relative peak areas). The method showed satisfactory performance in terms of selectivity, accuracy (99.3-101.4%) and linearity (R-2 = 0.999). Finally, the method was applied to commercial samples of tetracycline, oxytetracycline and chlortetracycline. This method can be applied for rapid quality control in developing countries in particular, and across the globe in general.
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| 46. |
- Pedehontaa-Hiaa, Guillaume, et al.
(författare)
-
Layer‑by‑Layer Assemblies Based on a Cationic β‑Cyclodextrin Polymer: Chiral Stationary Phases for Open‑Tubular Electrochromatography
- 2015
-
Ingår i: Chromatographia. - : Springer Science and Business Media LLC. - 0009-5893 .- 1612-1112. ; 78:7-8, s. 533-541
-
Tidskriftsartikel (refereegranskat)abstract
- Non-covalent chiral stationary phases for open-tubular capillary electrochromatography (OT-CEC) were developed using polyelectrolyte multilayer (PEM) coatings. These chiral coatings were made by alternately flushing the separation capillary with cationic and anionic polymers using a polymer of trimethylammonium-β-CD (pCD+) as a chiral selector. The layer-by-layer construction was monitored by EOF measurements. To our knowledge, it is the first OT-CEC chiral stationary phase based on a layer-by-layer assembly including an ionic cyclodextrin polymer. The composition of PEM coating was optimized as regards chiral separation. Thus, the influence of the nature of the first adsorbed cationic polymer (pCD+, polyethyleneimine or poly(diallyldimethyl ammonium chloride)) and the influence of the anionic polymer (poly(sodium 4-styrenesulfonate), polycarboxymethyl-β-CD or chondroitin sulfate) were studied with regard to the apparent surface charge and the enantioselective properties of the coatings. Interactions between the studied enantiomers and the internal layers of the stationary phase were pointed out. We found that the optimal stationary phase was based on a pCD+/poly(sodium 4-styrenesulfonate)/pCD+ three-layer coating. This optimal coating was found to be stable as evidenced by the RSD of 2.2 % for the EOF values calculated from five independent analyses. It was effective for the chiral separation of both neutral and anionic solutes.
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| 47. |
- Quan, Can, et al.
(författare)
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Extraction of Astaxanthin from Shrimp Waste Using Pressurized Hot Ethanol
- 2009
-
Ingår i: Chromatographia. - : Vieweg Teubner. - 0009-5893 .- 1612-1112. ; 70:1-2, s. 247-251
-
Tidskriftsartikel (refereegranskat)abstract
- An efficient and environmentally sustainable extraction method is proposed for the enrichment of a high-value pigment, astaxanthin, from a low-value raw material, shrimp waste. Ethanol at elevated temperature and pressure was used as a "green" extraction solvent. An experimental design approach based on central composite design was used to investigate the dependence of pressurized liquid extraction (PLE) operating variables (pressure, temperature, extraction time) on the recovered astaxanthin concentration from shrimp waste. The results show that at a 95% confidence level, the most significant PLE operating variables were extraction temperature and time. Extraction pressure had only a minor effect on the astaxanthin recovery in the studied experimental conditions. The maximum astaxanthin recovery obtainable by PLE was calculated from the chemometrics results and then appraised by experiments. Our results show astaxanthin yields of around 24 mg kg(-1) shrimp waste. The reproducibility of the developed PLE method is good, showing a relative standard deviation of 3.5% (n = 6) for astaxanthin.
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| 48. |
- Ramström, O., et al.
(författare)
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Applications of molecularly imprinted materials as selective adsorbents : Emphasis on enzymatic equilibrium shifting and library screening
- 1998
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Ingår i: Chromatographia. - 0009-5893. ; 47:7-8, s. 465-469
-
Tidskriftsartikel (refereegranskat)abstract
- Molecular imprinting is an attractive method for producing highly selective adsorbents, and several new and potentially useful applications based on molecularly imprinted polymers (MIPs) have been described in recent years. In this article, we highlight some of the areas where these materials have found application, and also describe some new fields of application where the selectivities of imprinted materials can be gainfully employed, for example as binding matrices in the screening of combinatorial libraries, and as auxiliary agents in enzymatic syntheses.
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| 49. |
- Ramström, O., et al.
(författare)
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Chiral recognition by molecularly imprinted polymers in aqueous media
- 1998
-
Ingår i: Chromatographia. - 0009-5893. ; 48:3-4, s. 197-202
-
Tidskriftsartikel (refereegranskat)abstract
- Molecularly imprinted polymers were prepared using 2-vinylpyridine and/or methacrylic acid as functional monomers in a self-assembly imprinting protocol. The resulting polymers were analyzed in aqueous media, and the effects from the pH of the mobile phase and the degree of added organic solvent were investigated. The results are indicative of the importance of ionic bonds in conjunction with hydrophobic interactions in the formation of the complexes between the analyte and the polymers.
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| 50. |
- Saleh, Aljona, et al.
(författare)
-
A Bioanalytical Method for Quantification of Thioredoxins in Bacillus anthracis by Digestion with Immobilized Pepsin and LC-MS/MS and On-line LC/LC-MS/MS
- 2016
-
Ingår i: Chromatographia. - : Springer Science and Business Media LLC. - 0009-5893 .- 1612-1112. ; 79:7-8, s. 383-393
-
Tidskriftsartikel (refereegranskat)abstract
- We describe a method for the quantification of proteins in a biological matrix through digestion with pepsin. Pepsin is a gastric protease that efficiently cleaves proteins in an acidic environment. In this study, it has been used to generate peptides used for the quantification of physiologically relevant thioredoxin proteins in a lysate of Bacillus anthracis-the causative agent of anthrax. Carefully selected signature peptides for proteins that were digested with pepsin were immobilized on agarose gel. Filtered samples were analyzed by liquid chromatography tandem mass spectrometry (LC-MS/MS) and by two-dimensional liquid chromatography tandem mass spectrometry (LC/LC-MS/MS) when additional selectivity was needed. Some important incubation parameters were adjusted to get the highest possible peptide yield. Escherichia coli was used as a surrogate matrix for the method development. The method was validated at a low nM range for selectivity, accuracy and precision. Validation showed that signature peptides were selective for the proteins, and that the method accuracy varied between 89 and 115 % with a precision of less than 12 %. The results from using pepsin in analyzing samples from Bacillus anthracis were similar to those previously obtained using western blot, and they validate pepsin as a suitable protease to generate signature peptides in a complex biological matrix as an alternative to trypsin.
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