| 1. |
- Appelblad, Patrik, et al.
(författare)
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Determination of C-21 ketosteroids in serum using trifluoromethanesulfonic acid catalyzed precolumn dansylation and 1,1’-oxalyldiimidazole postcolumn peroxyoxalate chemiluminescence detection
- 1998
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Ingår i: Analytical Chemistry. - Washington : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 70:23, s. 5002-5009
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Tidskriftsartikel (refereegranskat)abstract
- A new procedure for the quantitation of C-21 ketosteroids using trifluoromethanesulfonic acid-catalyzed precolumn dansylation and coupled column liquid chromatographic separation, followed by postcolumn 1,1‘-oxalyldiimidazole peroxyoxalate chemiluminescence detection is presented. In the simultaneous optimization of chromatographic resolution and chemiluminescence intensity, a coupled column chromatographic system and a stopped-flow system were used. An eluent containing 20 mM phosphate buffer at pH 6.7 accomplished an efficient separation of 3α-hydroxy-5β-pregnan-20-one from a mixture containing 10 C-21 ketosteroids. Phosphate buffer also proved to be the most advantageous, among the six buffers tested, for sensitive detection. Experimental design and multivariate data analysis were used to characterize and optimize the postcolumn reaction chemistry in the chromatographic system. A valid full factorial design with excellent predictability showed that the flow rates for both 1,1‘-oxalyldiimidazole and hydrogen peroxide were the factors most strongly affecting the sensitivity of the system. The theoretical plate numbers were above 11 000 for all 10 dansylated ketosteroids. The 3σ detection limit estimated from 3α-hydroxy-5β-pregnan-20-one calibration curve data was 1.6 pmol (n = 4, 125 μL injected) and spiked serum containing 0−74 pmol of this compound showed overall recoveries of 73 ± 9% (n = 12). Quantitation of 3α-hydroxy-5β-pregnan-20-one was finally carried out on 45 serum samples and the results compared to those from a radioimmunoassay (RIA) method. The data acquired with the procedure described in this work compare well with the results from RIA, which confirms the reliability of the new analytical procedure.
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| 2. |
- Appelblad, Patrik, et al.
(författare)
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Fast hydrophilic interaction liquid chromatographic separations on bonded zwitterionic stationary phase
- 2008
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Ingår i: Journal of Separation Science. - : Wiley-VCH Verlagsgesellschaft. - 1615-9306 .- 1615-9314. ; 31:9, s. 1529-1536
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Tidskriftsartikel (refereegranskat)abstract
- Separation science is an art of obtaining adequate resolution of the desired compounds in minimum time, and with minimum effort in terms of sample preparation and data evaluation. In LC, where selectivity is a main driving force for separation, the availability of different separation modes capable of operating at high flow rates is a way to make combined optimal use of selectivity, efficiency, and speed. The separation of polar and hydrophilic compounds is problematic in RP LC due to the poor retention. Hydrophilic interaction liquid chromatography (HILIC) is a more straightforward separation mode to address this problem. Herein, it is shown that separations in HILIC mode are equally efficient as for RP, providing a potential for very fast separations on short columns. This is not only facilitated by the low viscosity of the mobile phase compositions used, compared to typical RP eluents, but also due to higher column permeability. To exemplify this, baseline separations of uracil and cytosine are shown in less than 4 s and of Tamiflu® and its main metabolite in less than 40 s, both under isocratic conditions. HILIC must therefore be considered having potential for high throughput purposes, and being an attractive candidate as the second separation dimension in 2-D HPLC.
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| 3. |
- Appelblad, Patrik, et al.
(författare)
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Perfluorosulfonated Ionomer-Modified Polyethylene. A Material for Simultaneous Solid-Phase Enrichment and Enhanced Precolumn Dansylation of C-21 Ketosteroids in Human Serum
- 2001
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 73:15, s. 3701-8
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Tidskriftsartikel (refereegranskat)abstract
- A new derivatization procedure has been developed where solid-phase catalysis is utilized to facilitate the formation of hydrazones in precolumn labeling of keto-containing compounds. This procedure has been implemented on a solid-phase enrichment and enhanced derivatization (SPEED) device, prepared from porous polyethylene that has been coated with Nafion and dansylhydrazine. The SPEED devices have been optimized using experimental design and characterized for dansylation of C-21 ketosteroids by multivariate data analysis, using progesterone as the model compound. The reaction temperature and the molar ratio between the steroid and the derivatization reagent were found to be the factors most strongly affecting the reaction. Faster reaction kinetics were achieved when the molar ratio between dansylhydrazine and the steroid was increased. Mass spectroscopic analysis showed that the four derivative peaks eluting when derivatized progesterone was separated on an octadecyl silica stationary phase were due to the syn and anti mono- and bis(hydrazones) formed in the reaction. Using optimal reaction conditions, the derivatives mainly constitute the syn and anti conformers of bis-derivatives. In contrast to solution-based acid catalysis, the SPEED device was remarkably insensitive to water in the reaction mixture. A sample volume of 400 L was found to be the maximum, enabling sample enrichment prior derivatization. Using optimal experimental conditions, picomole amounts of ketosteroids could be derivatized in 10 min at room temperature. Analysis of spiked serum samples containing 0.4-2.0 nmol of progesterone showed overall recoveries of 52-63%. The corresponding 3 detection limit was 1.3 pmol (n = 4, 100 L injected), as estimated from calibration curve data.
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| 4. |
- Appelblad, Patrik, et al.
(författare)
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Separation and detection of neuroactive steroids from biological matrices
- 2002
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Ingår i: Journal of Chromatography A. ; 955:2, s. 151-82
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Tidskriftsartikel (refereegranskat)abstract
- This review is based on a selection of research papers published mainly in the last decade and it describes various analytical aspects of separation and detection of neuroactive steroids in biological matrices.
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| 5. |
- Hellberg, Emma, et al.
(författare)
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Evaluation of dissolution techniques for orally disintegrating mini-tablets
- 2021
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Ingår i: Journal of Drug Delivery Science and Technology. - : Elsevier. - 1773-2247. ; 61
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Tidskriftsartikel (refereegranskat)abstract
- Mini-tablets are suitable for paediatric as well as geriatric use since they may provide flexible and accurate dosing and administration. Due to the minute tablet size, there is a need for new standardized quality evaluation procedures and conventional techniques may have to be adopted. The main objective of the study was to evaluate different dissolution techniques for orally disintegrating mini-tablets. Dissolution tests using mini-paddle apparatus were compared with standard size paddle apparatus, and the effect of paddle rotation speed was evaluated. Also, the filter choice, and its impact on dissolution, was considered. Sodium salicylate was used as a model drug substance and was mixed with different size fractions of mannitol. The powder mixtures were compacted into 2 mm flat faced tablets. The mini-tablets were characterized regarding weight and content uniformity, tensile strength, friability, disintegration and dissolution. Similar dissolution profiles were obtained with both mini and standard equipment. The paddle rotation speed affected the dissolution profiles; a low paddle speed resulted in a slower dissolution. Furthermore, choosing a chemically inert filter will increase the likelihood of obtaining reliable and accurate results. An appropriately designed dissolution test using mini-paddle apparatus is required prior to further implementation in quality control procedures.
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| 6. |
- Kong, Ziqing, et al.
(författare)
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Simultaneous determination of ribonucleoside and deoxyribonucleoside triphosphates in biological samples by hydrophilic interaction liquid chromatography coupled with tandem mass spectrometry
- 2018
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Ingår i: Nucleic Acids Research. - : Oxford University Press. - 0305-1048 .- 1362-4962. ; 46:11
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Tidskriftsartikel (refereegranskat)abstract
- Information about the intracellular concentration of dNTPs and NTPs is important for studies of the mechanisms of DNA replication and repair, but the low concentration of dNTPs and their chemical similarity to NTPs present a challenge for their measurement. Here, we describe a new rapid and sensitive method utilizing hydrophilic interaction liquid chromatography coupled with tandem mass spectrometry for the simultaneous determination of dNTPs and NTPs in biological samples. The developed method showed linearity (R2 > 0.99) in wide concentration ranges and could accurately quantify dNTPs and NTPs at low pmol levels. The intra-day and inter-day precision were below 13%, and the relative recovery was between 92% and 108%. In comparison with other chromatographic methods, the current method has shorter analysis times and simpler sample pre-treatment steps, and it utilizes an ion-pair-free mobile phase that enhances mass-spectrometric detection. Using this method, we determined dNTP and NTP concentrations in actively dividing and quiescent mouse fibroblasts.
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| 7. |
- Lakso, Hans-Ake, et al.
(författare)
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Quantification of methylmalonic acid in human plasma with hydrophilic interaction liquid chromatography separation and mass spectrometric detection
- 2008
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Ingår i: Clinical Chemistry. - Washington, DC : American Association for Clinical Chemistry. - 0009-9147 .- 1530-8561. ; 54:12, s. 2028-2035
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Tidskriftsartikel (refereegranskat)abstract
- Background: Measurement of methylmalonic acid (MMA) in serum or plasma is useful for diagnosing cobalamin deficiency. We developed a method for quantifying MMA in plasma based on hydrophilic interaction liquid chromatography (HILIC) and single-stage negative electrospray ionization (ESI) mass spectrometry. Methods: We deproteinized plasma samples (200 microL) with 800 microL acidified acetonitrile containing 0.17 micromol/L deuterated MMA (D(3)-MMA) internal standard, centrifuged the samples, and injected 4 microL of the supernatant into the LC-MS instrument. Separation was achieved within 3 min on a Merck SeQuant ZIC-HILIC column with a mobile phase consisting of 4 volumes acetonitrile plus 1 volume 100 mmol/L ammonium acetate buffer, pH 4.5, at a flow rate of 400 microL/min. Subsequent column washing and reconditioning contributed to a total run time of 10 min. MMA and D(3)-MMA were quantified by single-ion monitoring (m/z 117.2 and 120.2, respectively) in negative ESI mode at a drying-gas flow rate of 10 L/min, 300 degrees C, and a capillary voltage of 3.0 kV. Results: The estimated limits of MMA quantification and detection were 0.09 micromol/L and 0.03 micromol/L, respectively, in plasma. The assay was linear to 200 micromol/L. Interassay and intraassay CVs were < or = 5% at all tested concentrations. Recoveries were 90%-93%. Conclusions: This robust assay allows analysis of MMA in human plasma without derivatization. Sample preparation is simple and suitable for automation.
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| 8. |
- Lindberg, Richard H., et al.
(författare)
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Online solid phase extraction liquid chromatography using bonded zwitterionic stationary phases and tandem mass spectrometry for rapid environmental trace analysis of highly polar hydrophilic compounds – Application for the antiviral drug Zanamivir
- 2015
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Ingår i: Talanta. - : Elsevier. - 0039-9140 .- 1873-3573. ; 141, s. 164-169
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Tidskriftsartikel (refereegranskat)abstract
- Abstract Zanamivir (Za) is a highly polar and hydrophilic antiviral drug used for the treatment of influenza A viruses. Za has been detected in rivers of Japan and it's environmental occurrence has the risk of inducing antiviral resistant avian influenza viruses. In this study, a rapid automated online solid phase extraction liquid chromatography method using bonded zwitterionic stationary phases and tandem mass spectrometry (SPE/LC–MS/MS) for trace analysis of Za was developed. Furthermore, an internal standard (IS) calibration method capable of quantifying Za in Milli-Q, surface water, sewage effluent and sewage influent was evaluated. Optimum pre-extraction sample composition was found to be 95/5 v/v acetonitrile/water sample and 1% formic acid. The developed method showed acceptable linearities (r2≥0.994), filtration recovery (≥91%), and intra-day precisions (RSD≤16%), and acceptable and environmentally relevant LOQs (≤20 ng L−1). Storage tests showed no significant losses of Za during 20 days and +4/−20 °C (≤12%) with the exception of influent samples, which should be kept at −20 °C to avoid significant Za losses. The applicability of the method was demonstrated in a study on phototransformation of Za in unfiltered and filtered surface water during 28 days of artificial UV irradiation exposure. No significant (≤12%) phototransformation was found in surface water after 28 days suggesting a relatively high photostability of Za and that Za should be of environmental concern.
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| 9. |
- Marrubini, Giorgio, et al.
(författare)
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Experimental designs for solid-phase microextraction method development in bioanalysis : A review
- 2020
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Ingår i: Analytica Chimica Acta. - : Elsevier. - 0003-2670 .- 1873-4324. ; 1119, s. 77-100
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Forskningsöversikt (refereegranskat)abstract
- This review is an update of a previous review in 2009 and covers publications from 2009 to 2019. The review focuses on experimental design, referred to as the design of experiments (DoE), used in developing bioanalytical solid-phase microextraction (SPME) methods. Characteristics of different SPME approaches are illustrated and critically discussed. The literature selection evidences that two-level full factorial designs, with a limited number of factors (<5), are most frequently used for preliminary factors screening. When applying the response surface methodology for the quantitative assessment of factorial effects, few quadratic models were used. The most popular were the rotatable central composite and Box-Benkhen designs. Models including more than four factors, such as fractional factorial designs (including the Plackett-Burman and Taguchi designs), were rarely used. Definitive screening and D-Optimal designs were not reported anywhere in the literature selection. When examining the diagnostic criteria used to evaluate different model's quality and validity, it was apparent the researchers relied heavily on commercial software for experimental design, analysis, and reporting of the results.
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