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  • 1. El-Beqqali, Aziza
    et al.
    Kussak, Anders
    Södertörn University, School of Life Sciences.
    Abdel-Rehim, Mohamed
    Determination of dopamine and serotonin in human urine samples utilizing microextraction online with liquid chromatography/electrospray tandem mass spectrometry2007In: Journal of Separation Science, ISSN 1615-9306, E-ISSN 1615-9314, Vol. 30, no 3, 421-424 p.Article in journal (Refereed)
    Abstract [en]

    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 inverse of the concentration: 1/x for the calibration range 50-4000 mu g/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 (r(2) >0.999) 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.

  • 2. El-Beqqali, Aziza
    et al.
    Kussak, Anders
    Södertörn University, School of Life Sciences.
    Abdel-Rehim, Mohamed
    Fast and sensitive environmental analysis utilizing microextraction in packed syringe online with gas chromatography-mass spectrometry - Determination of polycyclic aromatic hydrocarbons in water2006In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1114, no 2, 234-238 p.Article in journal (Refereed)
    Abstract [en]

    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.

  • 3. El-Beqqali, Aziza
    et al.
    Kussak, Anders
    Södertörn University, School of Life Sciences.
    Blomberg, Lars
    Abdel-Rehim, Mohamed
    Microextraction in packed syringe/liquid chromatography/electrospray tandem mass spectrometry for quantification of acebutolol and metoprolol in human plasma and urine samples2007In: Journal of Liquid Chromatography & Related Technologies, ISSN 1082-6076, E-ISSN 1520-572X, Vol. 30, no 4, 575-586 p.Article in journal (Refereed)
    Abstract [en]

    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.

  • 4. Li, Jianjun
    et al.
    Dzieciatkowska, Monika
    Hood, Derek W.
    Cox, Andrew D.
    Schweda, Elke K. H.
    Södertörn University, School of Life Sciences.
    Moxon, E. Richard
    Richards, James C.
    Structural characterization of sialylated glycoforms of H-influenzae by electrospray mass spectrometry: fragmentation of protonated and sodiated O-deacylated lipopolysaccharides2007In: Rapid Communications in Mass Spectrometry, ISSN 0951-4198, E-ISSN 1097-0231, Vol. 21, no 6, 952-960 p.Article in journal (Refereed)
    Abstract [en]

    Sialylated lipopolysaccharide (LPS) glycoforms from Haemophilus influenzae were characterized by tandem mass spectrometry using a new generation hyphenated mass spectrometer which combines a triple quadrupole and a linear ion trap (Q-Trap). The fragmentation of both protonated and sodiated molecular ions from O-deacylated LPS (LPS-OH) obtained in MS2 experiments in the positive mode was studied. The MS2 spectra of protonated ions provided unambiguous evidence for the presence and sequence of sialylated lactosamine present in lacto-N-neotetraose oligosaccharide extensions but not for sialyl-lactose structures whilst fragmentation of sodiated adducts, [M+Na](+), afforded information diagnostic of mono- and disialylated lactose extensions. To study this we used a highly sialylated LPS from a H. influenzae strain capable of sialyl-lactose expression only. We then applied the method to the H. influenzae genome strain, Rd, in which glycoforms containing both sialyl-lactose and sialyl-lacto-N-neotetraose were detected from diagnostic B-ions at m/z 638.2 ([Neu5Ac(1) Hex(2)+ Na](+)) and 657.2 ([Neu5Ac(1) Hex(1) HexNAc(1)+H](+)). Unique fragmentation patterns provided the locations and sequences of these oligosaccharide extensions. This is the first time both sialylated lactose and sialylated lacto-N-neotetraose units have been detected and characterized by tandem mass spectrometry in the same molecule. This methodology is of general applicability for determination of common sialylated oligosaccharide extension in bacterial LPS.

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