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- El-Beqqali, Aziza, 1966-, et al.
(author)
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Determination of dopamine and serotonin in human urine samples utilizing microextraction online with liquid chromatography/electrospray tandem mas spectrometry
- 2007
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In: Journal of Separation Science. - : Wiley. - 1615-9306 .- 1615-9314. ; 30:3, s. 421-424
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Journal article (peer-reviewed)abstract
- A specific LC-MS-MS method for the determination of dopamine and serotonin (5-hydroxytryptamine; 5HT) in human urine is described. The analytes were extracted from urine and preconcentrated by microextraction in a packed syringe (MEPS). The new method is very promising, very easy to use, fully automated, of low cost, and rapid in comparison to previously used methods. The method was validated and the standard curves were evaluated by means of quadratic regression and weighted by the inverse of the concentration: 1/x for the calibration range 50–4000 μg/L. The MEPS applied polymer (silica-C8) could be used more than 300 times. The extraction recovery was about 50%. The results showed close correlation coefficients (r2 A0.999) for all analytes in the calibration range studied. The accuracy of MEPS-LC-MS-MS was 100–101% for dopamine and 99–100% for 5HT. The interday precision (n = 3 days), expressed as the RSD%, was 6.0–7.7% for dopamine and 6.1–11% for 5HT. MEPS reduced the handling time by 12 times compared to a published method.
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- El-Beqqali, Aziza, et al.
(author)
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Fast and sensitive environmental analysis utilizing microextraction in packed syringe online with gas chromatography-mass spectrometry - Determination of polycyclic aromatic hydrocarbons in water
- 2006
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In: Journal of Chromatography A. - : Elsevier BV. - 0021-9673 .- 1873-3778. ; 1114:2, s. 234-238
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Journal article (peer-reviewed)abstract
- A new sensitive, selective, fast and accurate technique for online sample preparation was developed. Microextraction in a packed syringe (MEPS) is a new miniaturised, solid-phase extraction (SPE) technique that can be connected online to GC or LC without any modifications. In MEPS approximately 1 mg of the solid packing material is inserted into a syringe (100-250 ml) as a plug. Sample preparation takes place on the packed bed. The bed can be coated to provide selective and suitable sampling conditions. The new method is very promising. It is very easy to use, fully automated, of low cost and rapid in comparison with previously used methods. The determination of polycyclic hydrocarbons (PAHs) in water was performed using MEPS as sample preparation method online with gas chromatography and mass spectrometry (MEPS-GC-MS). The results from MEPS as sample preparation were compared with other techniques such as stir bar sorptive extraction (SBSE) and solid-phase microextraction (SPME). The method was validated and the standard curves were evaluated by the means of quadratic regression and weighted by inverse of the concentration: 1/x for the calibration range 5-1000 ng/L. The MEPS applied polymer (silica-C8) could be used more than 400 times before the syringe was discarded. The extraction recovery was about 70%. The results showed close correlation coefficients (R > 0.998) for all analytes in the calibration range studied. The accuracy of MEPS-GC-MS was between 90 and 113% and the inter-day precision (n = 3 days), expressed as the relative standard deviation (RSD%), was 8-16%. MEPS reduced the handling time by 30 and 100 times compared to SPME and SBSE, respectively.
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- El-Beqqali, Aziza, et al.
(author)
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Microextraction in packed syringe/liquid chromatography/electrospray tandem mass spectrometry for quantification of acebutolol and metoprolol in human plasma and urine samples
- 2007
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In: Journal of Liquid Chromatography & Related Technologies. - : Informa UK Limited. - 1082-6076 .- 1520-572X. ; 30:4, s. 575-586
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Journal article (peer-reviewed)abstract
- The aim of the present investigation was to develop a simple, fast, and sensitive method for the determination of acebutolol and metoprolol in human plasma and urine samples. The determination of acebutolol and metoprolol in plasma and urine was performed using micro extraction in packed syringe (MEPS) as a sample preparation method, online with high performance liquid chromatography and tandem mass spectrometry (LC-MS/MS). In MEPS the sampling sorbent was 1 mg polystyrene polymer, which was inserted in a 250 mu L syringe. The lower limits of quantification (LLOQ) for acebutolol and metoprolol were set to 1.0 ng/mL. The accuracy of quality control samples (QC) varied by +/- 10%, and precision (R.S.D.) had a deviation of 1.4-12% for plasma and urine samples. The calibration curve was obtained within the concentration range 1.0-100 ng/mL in both plasma and urine. The regression correlation coefficients (R-2) for plasma and urine samples were >= 0.999 for all runs. The present method is miniaturized, fully automated, robust, and can be easily used for pharmacokinetic and pharmacodynamic studies of acebutolol and metoprolol.
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- Kussak, Anders, 1964-
(author)
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Development of methods for determining aflatoxins in biological material
- 1995
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Doctoral thesis (other academic/artistic)abstract
- In this thesis, it is shown how aflatoxins can be determined in biological material. The thesis is a summary of five papers.Aflatoxins are carcinogenic mycotoxins produced by Aspergillus moulds. Methods were developed for the determination of aflatoxins in samples of airborne dust and human urine collected at feed factories. For the dust samples from such agricultural products as copra, cotton seed and maize, methods were developed for the determination of aflatoxins B1, B2, G1 and G2. For urine samples, methods were developed for analysing the four aflatoxins above that naturally occur in dust, and the metabolites aflatoxins M1 and Q1.Sample preparation of dust samples included solvent extraction, filtration and immunoaffinity column extraction. Urine samples were cleaned up using immunoaffinity column extraction or solid-phase extraction using ethyl bonded-phase columns. All extractions with these columns were automated by means of a laboratory robot.Reversed-phase liquid chromatography was used to separate the aflatoxins in the cleaned-up extracts. Detection was performed by fluorescence after post-column derivatization by addition of bromine. Parameters for the derivatization were studied using factorial designs. To confirm the identity of aflatoxins in naturally contaminated airborne dust samples and spiked urine, liquid chromatography was combined with electrospray mass spectrometry.The detection limits of the aflatoxins in dust samples were in the range 1.8-3.1 ng/g in 10-mg dust samples using fluorescence detection. Aflatoxins were determined in spiked urine down to the 6.8-18 pg/ml level. In naturally contaminated dust of copra and cotton seed, aflatoxins were detected with a content of 9-50 pg/mg of aflatoxin Bi. No aflatoxins could be detected in any urine sample obtained from feed factory workers that were less than 6.8 pg/ml of aflatoxins B1, B2, G1 and G2 and less than 18 pg/ml of aflatoxins M1 and Q1.
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| 8. |
- Kussak, Anders, et al.
(author)
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Quadrupole ion-trap mass spectrometry to locate fatty acids on lipid A from Gram-negative bacteria
- 2002
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In: Analytical Biochemistry. - 0003-2697 .- 1096-0309. ; 307:1, s. 131-137
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Journal article (peer-reviewed)abstract
- The structure of lipid A released by mild acid hydrolysis from lipopolysaccharide from two strains of Shigella flexneri with different degrees of acylation was characterized using electrospray ionization (ESI) and ion-trap mass spectrometry. The lipid A was analyzed underivatized with ESI in negative-ion mode. With multiple stages of fragmentation (MSn), both the degree of acylation and the positions of the fatty acids on the disaccharide backbone could be determined. It was possible to determine the degree of acylation by the MSn technique, where in each MS stage the parent ion was an ion where one fatty acid had been eliminated. One way to determine the location of the fatty acids was by identifying cross-ring fragments of the reducing sugar from parent ions containing different numbers of fatty acids. Another was by identifying a possible charge-driven release of fatty acids situated close to a phosphate group. The fatty acids were otherwise eliminated by a charge-remote fragmentation mechanism. The combined data show the usefulness of ion-trap mass spectrometers for this type of analysis.
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| 9. |
- Liu, J., et al.
(author)
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Anti-pig antibody adsorption efficacy of {alpha}-Gal carrying recombinant P-selectin glycoprotein ligand-1/immunoglobulin chimeras increases with core 2 {beta}1, 6-N-acetylglucosaminyltransferase expression
- 2005
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In: Glycobiology. - : Oxford University Press (OUP). - 0959-6658 .- 1460-2423. ; 15:6, s. 571-83
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Journal article (peer-reviewed)abstract
- We have previously described the construction of a P-selectin glycoprotein ligand-1-mouse immunoglobulin Fc fusion protein, which when transiently coexpressed with the porcine alpha1,3 galactosyltransferase in COS cells becomes a very efficient adsorber of xenoreactive, anti-pig antibodies. To relate the adsorption capacity with the glycan expression of individual fusion proteins produced in different cell lines, stable CHO-K1, COS, and 293T cells producing this fusion protein have been engineered. On alpha1,3 galactosyltransferase coexpression, high-affinity adsorbers were produced by both COS and 293T cells, whereas an adsorber of lower affinity was derived from CHO-K1 cells. Stable coexpression of a core 2 beta1,6 N-acetylglucosaminyltransferase in CHO-K1 cells led to increased alpha-Gal epitope density and improved anti-pig antibody adsorption efficacy. ESI-MS/MS of O-glycans released from PSGL-1/mIgG(2b) produced in an alpha1,3 galactosyl- and core 2 beta1,6 N-acetylglucosaminyltransferase expressing CHO-K1 cell clone revealed a number of structures with carbohydrate sequences consistent with terminal Gal-Gal. In contrast, no O-glycan structures with terminal Gal-Gal were identified on the fusion protein when expressed alone or in combination with the alpha1,3 galactosyltransferase in CHO-K1 cells. In conclusion, the density of alpha-Gal epitopes on PSGL-1/mIgG(2b) was dependent on the expression of O-linked glycans with core 2 structures and lactosamine extensions. The structural complexity of the terminal Gal-Gal expressing O-glycans with both neutral as well as sialic acid-containing structures is likely to contribute to the high adsorption efficacy.
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