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  • 1.
    Abuzooda, Thana
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Amini, Ahmad
    Abdel-Rehim, Mohamed
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Graphite-based microextraction by packed sorbent for online extraction of beta-blockers from human plasma samples2015In: Journal of chromatography. B, ISSN 1570-0232, E-ISSN 1873-376X, Vol. 992, p. 86-90Article in journal (Refereed)
    Abstract [en]

    In the present work a new graphitic material (Carbon-XCOS) was used as a sorbent for microextraction by packed sorbent (MEPS).The beta-blockers metoprolol and acebutolol in plasma samples were extracted and detected online using Carbon-MEPS syringe and liquid chromatography and tandem mass spectrometry (LC-MS/MS). Factors affecting the MEPS performance such as conditioning, washing and elution solutions were investigated. The validation of the bioanalytical method was performed using human plasma. The standard curve ranged from 10 to 2000 nM and the lower limit of quantification (LLOQ) was set to 10 nM. The method validation showed good accuracy and precision for the quality control (QC) samples at three concentration levels (30, 800 and 1600 nM). The accuracy values of the QC samples were in the range of 86-108% (n = 18). The precision values of intra- and inter-day for QC samples ranged from 4.4% to 14.4% (RSD) for the both studied analytes. The coefficient of determination (R-2) values were >= 0.999 (n = 3).

  • 2.
    Amelina, Hanna
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Sjodin, Marcus O. D.
    Bergquist, Jonas
    Cristobal, Susana
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Quantitative subproteomic analysis of age-related changes in mouse liver peroxisomes by iTRAQ LC-MS/MS2011In: Journal of chromatography. B, ISSN 1570-0232, E-ISSN 1873-376X, Vol. 879, no 30, p. 3393-3400Article in journal (Refereed)
    Abstract [en]

    Aging is a complex multifactorial phenomenon, which is believed to result from the accumulation of cellular damage to biological macromolecules. Peroxisomes recently emerged as another important source of reactive oxygen species (ROS) production in addition to mitochondria. However, the role of these organelles in the process of aging is still not clear. The aim of this study was to characterize the changes in protein expression profiles of young (10 weeks old) versus old (18 months old) mouse liver peroxisome-enriched fractions. We have applied shotgun proteomic approach based on liquid chromatography and tandem mass spectrometry (LC-MS/MS) combined with iTRAQ (isobaric tags for relative and absolute quantitation) labeling that allows comparative quantitative multiplex analysis. Our analysis led to identification and quantification of 150 proteins, 8 out of which were differentially expressed between two age groups at a statistically significant level (p < 0.05), with folds ranging from 1.2 to 4.1. These proteins involved in peroxisornal beta-oxidation, detoxification of xenobiotics and production of ROS. Noteworthy, differences in liver proteome have been observed between as well as within different age groups. In conclusion, our subproteomic quantitative study suggests that mouse liver proteome is sufficiently maintained until certain age.

  • 3.
    Amelina, Hanna
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Sjödin, Marcus O. D.
    Bergquist, Jonas
    Cristobal, Susana
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Quantitative subproteomic analysis of age-related changes in mouse liver peroxisomes by iTRAQ LC-MS/MSIn: Journal of chromatography. B, ISSN 1570-0232, E-ISSN 1873-376XArticle in journal (Refereed)
  • 4.
    Amini, Nahid
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Crescenzi, Carlo
    Feasibility of an on-line restricted access material/liquidchromatography/tandem mass spectrometry method in the rapid and sensitive determination of organophosphorustriesters in human blood plasma2003In: Journal of chromatography. B, ISSN 1570-0232, E-ISSN 1873-376X, Vol. 795, no 2, p. 245-256Article in journal (Refereed)
    Abstract [en]

    A rapid on-line solid phase extraction/liquid chromatography/tandem mass spectrometry (SPE/LC/MS/MS) method usingrestricted access material (RAM) was developed for the simultaneous determination of eight organophosphorus triesters inuntreated human blood plasma. In a process involving column-switching techniques, the analytes were enriched on the RAMcolumn, separated using a C-18 analytical column and detected with LC/MS. Tandem mass spectrometrywas used to characterizeand quantify the analytes. To elucidate the fragmentation pathway of a number of the analytes, MS3 experiments using an iontrap mass spectrometer were performed. The matrix effects associated with using APCI and ESI interfaces were investigated.The recoveries obtained were in the range 60–92% (R.S.D. < 6%), with estimated detection limits between 0.2 and 1.8 ng/mlof plasma, and the total analysis time was 27 min.

  • 5. Chadt, J
    et al.
    Sykora, D
    Nilsson, Robert
    Stockholm University, Faculty of Science, Department of Genetics, Microbiology and Toxicology.
    Monitoring of dimethyl sulphate-induced N3-methyladenine, N7-methylguanine and O6-methylguanine DNA adducts using reversed-phase high performance liquid chromatography and mass spectrometry 2008In: Journal of chromatography. B, ISSN 1570-0232, E-ISSN 1873-376X, Vol. 867, p. 43-48Article in journal (Refereed)
    Abstract [en]

    This work describes the determination of N3-methyladenine, N7-methylguanine and O6-methylguanine adducts in dimethyl sulphate-treated salmon-testes DNA employing reversed-phase high performance liquid chromatography (RP-HPLC) with UV–vis detection, followed by mass-spectrometric verification using electrospray ionisation in positive mode ESI(+). Within validation parameters, accuracy, precision, calibration parameters, limit of detection (LOD) and quantitation (LOQ) as well as stability of standard stock solutions were tested and presented for UV/vis detection. The limit of detection (LOD) was found to be 0.1 ng/mL for N3-methyladenine and 0.2 ng/mL for both N7-methylguanine and O6-methylguanine (S/N = 3). The limit of quantitation (LOQ) was found to be 0.5 ng/mL for all measured compounds, (S/N = 10). Quantitative results were obtained for each substance based on eight-point calibration. Intra- and inter-day precisions were within 1.73–6.96 and 2.26–7.58%, respectively, and correlation coefficients of calibration curves (R2) ranged from 0.9992 to 0.9997. Relative proportion of N7-methylguanine was accounted for 61.53 ± 2.97% (R.S.D. = 4.8), N3-methyladenine for 38.19 ± 2.99% (R.S.D. = 9.6) and O6-methylguanine for 0.29 ± 0.02% (R.S.D. = 5.1), respectively. The application of the above-mentioned techniques provides a valuable contribution for simultaneous determination of methylated DNA adducts, and may represent a suitable approach for similar monitoring/screening studies.

  • 6.
    Claeson Bohnstedt, Kristina
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Karlberg, Bo
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Basun, Hans
    Schmidt, Staffan
    Porous graphitic carbon chromatography-tandem mass spectrometry for the detection of isoprostanes in human cerebrospinal fluid2005In: Journal of chromatography. B, ISSN 1570-0232, E-ISSN 1873-376X, Vol. 827, no 1, p. 39-43Article in journal (Refereed)
    Abstract [en]

    F2-isoprostanes are produced by the non-enzymatic peroxidation of arachidonic acid in membrane phospholipids. This paper describes a new method for the determination of all four classes of F2-isoprostanes in human cerebrospinal fluid (CSF) involving separation on a 1 mm × 150 mm porous graphitic carbon (PGC) column and detection by triple quadrupole mass spectrometry in negative-ion electrospray mode. The sample pre-treatment consisted of an ultrafiltration step, following which 300 μl of CSF sample could be injected directly onto a 1 mm × 10 mm PGC guard column functioning as a trap for the analytes. The loading solvent was Milli-Q water at 125 μl/min. After 3 min, the sample was switched into the separation column. The F2-isoprostanes were separated in 20 min using a linear solvent gradient comprising water, methanol, acetonitrile and ammonium hydroxide at a pH of 9.5 and a flow of 50 μl/min The limit of detection (calculated as 3S/N) was approximately 40 pM (14 pg/ml). The assay was linear within the examined range (18–450 pg/ml), using CSF spiked with iPF2α-III standard (r2 > 0.995). Repeatability data were calculated for CSF spiked to 90 pg/ml and the relative standard deviation (RSD) obtained was 3% (n = 6).

  • 7.
    El Beqqali, Aziza
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Ahmadi, Mazaher
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Abdel-Rehim, Mohamed
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Determination of AZD6118 in dog plasma samples utilizing microextraction by packed sorbent and liquid chromatography-electrospray ionization tandem mass spectrometry2017In: Journal of chromatography. B, ISSN 1570-0232, E-ISSN 1873-376X, Vol. 1043, p. 20-24Article in journal (Refereed)
    Abstract [en]

    In this work, for the first time, a method has been developed for the determination of AZD6118, a candidate drug, in dog plasma samples. The method is based on microextraction by packed sorbent (MEPS) of the drug prior to liquid chromatography-electrospray ionization tandem mass spectrometry assay. Various important factors affecting MEPS performance were optimized, and under the optimized condition, a linear calibration curve in the concentration range of 20-25,000 nmol L-1 with a coefficient of determination over 0.99 was obtained. The back-calculated values of the calibration points showed good agreement with the theoretical concentrations (coefficients of variation percent between 0.3-3.8). The lower limit of quantification and limit of detection were 20.0 and 2.9 nmol L-1, respectively. The repeatability and accuracy of the method was evaluated by determination of quality control samples at three concentration levels (low, medium and high) using the developed method, and the results (coefficients of variation values were between 1.9% and 3.2%, relative recoveries ranged between 93.5-102.1%) confirm that a powerful method has been developed for the extraction and determination of the investigated drug in dog plasma.

  • 8.
    El-Beqqali, Aziza
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Andersson, Lars I.
    Jeppsson, Amin Dadoun
    Abdel-Rehim, Mohamed
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Molecularly imprinted polymer-sol-gel tablet toward micro-solid phase extraction: II. Determination of amphetamine in human urine samples by liquid chromatography tandem mass spectrometry2017In: Journal of chromatography. B, ISSN 1570-0232, E-ISSN 1873-376X, Vol. 1063, p. 130-135Article in journal (Refereed)
    Abstract [en]

    Amphetamine selective molecularly imprinted sol-gel polymer tablets, MIP-tablets, for solid-phase micro extraction of biofluid samples were prepared. An acetonitrile solution of deuterated amphetamine template and silane precursor, 3-(propylmethacrylate) trimethoxysilane, was soaked into the pores of polyethylene tablet substrates and polymerized by an acid-catalysed sol-gel process. Application of the resultant MIP-tablets to extract amphetamine from human urine samples followed by LC-MS/MS analysis was investigated. The extraction protocol was optimised with respect to pH of sample, addition of sodium chloride, extraction time, desorption solvent and desorption time. The final analysis method determined amphetamine in human urine with a limit of detection (LOD) of 1.0 ng/mL and a lower limit of quantification (LLOQ) of 5 ng/mL. Validation demonstrated accuracy of the method was 91.0-104.0% and inter-assay precision was 4.8-8.5% (RSD). Extraction recovery was 80%. The MIP-tablets could be re-used and the same tablet could be employed for more than twenty extractions.

  • 9. Grey, Carl
    et al.
    Edebrink, Per
    Krook, Maria
    Jacobsson, Sven P.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Development of a high performance anion exchange chromatography analysis for mapping of oligosaccharides2009In: Journal of chromatography. B, ISSN 1570-0232, E-ISSN 1873-376X, Vol. 877, no 20-21, p. 1827-1832Article in journal (Refereed)
    Abstract [en]

    In the present study a HPAEC-PAD method is described that was developed for monitoring the consistency of N-glycosylation during the production and purification of recombinant proteins and monoclonal antibodies. The method successfully separated 18 neutral and sialylated oligosaccharides. Results obtained were compared with MALDI-TOF MS and it was shown that both methods gave similar results. in addition, a method validation was performed showing that the HPAEC-PAD analysis was well suited for the mapping and characterization of oligosaccharides. The method was found to be robust and additionally the precision was significantly better compared to the MALDI-TOF MS method. 

  • 10.
    Idborg, Helena
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Zamani, Leila
    Edlund, Per-Olof
    Schuppe-Koistinen, Ina
    Jacobsson, Sven P.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Metabolic fingerprinting of rat urine by LC/MS. Part 1. Analysis by hydrophilic interaction liquid chromatography-electrospray ionization mass spectrometry2005In: Journal of chromatography. B, ISSN 1570-0232, E-ISSN 1873-376X, Vol. 828, no 1-2, p. 9-13Article in journal (Refereed)
  • 11.
    Javanbakht, Mehran
    et al.
    Amirkabir University of Technology, Tehran, Iran.
    Moein, Mohammad Mahdi
    Amirkabir University of Technology, Tehran, Iran.
    Akbari-adergani, Behrouz
    Ministry of Health and Medical Education, Tehran, Iran.
    On-line clean-up and determination of tramadol in human plasma and urine samples using molecularly imprinted monolithic column coupling with HPLC2012In: Journal of chromatography. B, ISSN 1570-0232, E-ISSN 1873-376X, Vol. 911, no 12, p. 49-54Article in journal (Refereed)
    Abstract [en]

    The applicability of an on-line solid phase extraction method using molecularly imprinted monolithic column was developed for the assay of tramadol (TRD) in urine and plasma samples. The monolithic column was prepared by using TRD as the template, methacrylic acid (MAA) as the functional monomer, ethylene glycol dimethacrylate (EGDMA) as the cross-linker and chloroform as the porogen with in situ molecular imprinting polymerization technique. Various parameters affecting the extraction efficiency of the monolithic column were evaluated. Chromatographic analysis of TRD after on-line clean-up of samples was performed by reversed-phase HPLC on an ACE column with ultraviolet detection at 218 nm. The present work was successfully applied for automated simple analysis of TRD in urine and plasma samples with high recoveries between 90.5–93.1% and 93.3–96.0%, respectively. The results revealed that in concentration up to 500 ng/mL of dextromethorphan (DEX), timolol (TMO) and O-desmethyltramadol (M1), the recoveries were not reduced more than 4.3% and 4.0% for plasma and urine samples, respectively. The limit of detection (S/N = 3) and limit of quantification (S/N = 10) for TRD in urine samples were 0.03 ng/mL and 0.10 ng/mL, and in plasma samples were 0.3 and 1.0 ng/mL, respectively. Inter-column precision of the assays (n = 3) for urine and plasma samples at the 100 ng/mL TRD level were 4.0% and 4.2%, respectively.

  • 12.
    Moein, Mohammad Mahdi
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    El-Beqqali, Aziza
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Abdel-Rehim, Abbi
    Jeppsson-Dadoun, Amin
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Abdel-Rehim, Mohamed
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Preparation of monolithic molecularly imprinted polymer sol-gel packed tips for high-throughput bioanalysis: Extraction and quantification of L-tyrosine in human plasma and urine samples utilizing liquid chromatography and tandem mass spectrometry2014In: Journal of chromatography. B, ISSN 1570-0232, E-ISSN 1873-376X, Vol. 967, p. 168-173Article in journal (Refereed)
    Abstract [en]

    In situ monolithic molecularly imprinted polymer sol-gel packed tips (MMSTs) were prepared and evaluated for the extraction of lung cancer biomarker L-tyrosine (Tyr) from human plasma and urine samples. Several extraction parameters such as the conditioning, washing and elution solutions, pH and time were investigated. The enrichment factor (EF) and extraction recovery (ER) were studied. MMST showed good selectivity and a high extraction recovery, and MMST as a sorbent showed good stability and repeatability. The method validation showed good regression correlation coefficients for plasma and urine samples (R-2 >= 0.996) within the concentration range of 5-1000 and 1-1000 nmol L-1 in plasma and urine samples, respectively. The lower limits of quantification (LLOQ) in the plasma and urine samples were 5 and 1 nmol L-1, respectively. The between-batch precision for Tyr in plasma ranged from 1.0 to 6.0%, and in urine it was from 1.0 to 7.0%. The results show that the developed method has more facility, stability, durability and repeatability compared with previous similar methods. To the best of our knowledge, this is the first study aimed at the selective separation of Tyr as a lung cancer biomarker by MMSTs from biological matrixes and detection by LC/MS/MS.

  • 13.
    Moein, Mohammad Mahdi
    et al.
    Amirkabir University of Technology, Hafez, Tehran, Iran.
    Javanbakht, Mehran
    Amirkabir University of Technology, Hafez, Tehran, Iran.
    Akbari-aderganib, Behrouz
    Ministry of Health and Medical Education, Tehran, Iran.
    Molecularly imprinted polymer cartridges coupled on-line with high performance liquid cheomatography for simple and rapid analysis of dextromethorphan in human plasma samples2011In: Journal of chromatography. B, ISSN 1570-0232, E-ISSN 1873-376X, Vol. 879, no 11-12, p. 777-782Article in journal (Refereed)
    Abstract [en]

    In this paper, a novel method is described for automated determination of dextromethorphan in biological fluids using molecularly imprinted solid-phase extraction (MISPE) as a sample clean-up technique combined with high performance liquid chromatography (HPLC). The water-compatible molecularly imprinted polymers (MIPs) were prepared using methacrylic acid as functional monomer, ethylene glycol dimethacrylate as cross-linker, chloroform as porogen and dextromethorphan as template molecule. These imprinted polymers were used as solid-phase extraction sorbent for the extraction of dextromethorphan from human plasma samples. Various parameters affecting the extraction efficiency of the MIP cartridges were evaluated. The high selectivity of the sorbent coupled to the high performance liquid chromatographic system permitted a simple and rapid analysis of this drug in plasma samples with limits of detection (LOD) and quantification (LOQ) of 0.12 ng/mL and 0.35 ng/mL, respectively. The MIP selectivity was evaluated by analyzing of the dextromethorphan in presence of several substances with similar molecular structures and properties. Results from the HPLC analyses showed that the recoveries of dextromethorphan using MIP cartridges from human plasma samples in the range of 1–50 ng/mL were higher than 87%.

  • 14. Moein, Mohammad Mandi
    et al.
    El Beqqali, Aziza
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Abdel-Rehim, Mohamed
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Bioanalytical method development and validation: Critical concepts and strategies2017In: Journal of chromatography. B, ISSN 1570-0232, E-ISSN 1873-376X, Vol. 1043, p. 3-11Article in journal (Refereed)
    Abstract [en]

    Bioanalysis is an essential part in drug discovery and development. Bioanalysis is related to the analysis of analytes (drugs, metabolites, biomarkers) in biological samples and it involves several steps from sample collection to sample analysis and data reporting. The first step is sample collection from clinical or preclinical studies; then sending the samples to laboratory for analysis. Second step is sample clean-up (sample preparation) and it is very important step in bioanalysis. In order to reach reliable results, a robust and stable sample preparation method should be applied. The role of sample preparation is to remove interferences from sample matrix and improve analytical system performance. Sample preparation is often labor intensive and timeconsuming. Last step is the sample analysis and detection. For separation and detection, liquid chromatography-tandem mass spectrometry (LC MS/MS) is method of choice in bioanalytical laboratories. This is due to high selectivity and high sensitivity of the LC MS/MS technique. In addition the information about the analyte chemical structure and chemical properties is important to be known before the start of bioanalytical work. This review provides an overview of bioanalytical method development and validation. The main principles of method validation will be discussed. In this review GLP and regulated bioanalysis are described. Commonly used sample preparation techniques will be presented. In addition the role of LC MS/MS in modern bioanalysis will be discussed. In the present review we have our focus on bioanalysis of small molecules.

  • 15. Moein, Mohammad Mandi
    et al.
    Javanbakht, Mehran
    Karimi, Mohammad
    Akbari-Adergani, Behrouz
    Abdel-Rehim, Mohamed
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. National Research Center, Cairo, Egypt.
    Three-phase molecularly imprinted sol-gel based hollow fiber liquid-phase microextraction combined with liquid chromatography-tandem mass spectrometry for enrichment and selective determination of a tentative lung cancer biomarker2015In: Journal of chromatography. B, ISSN 1570-0232, E-ISSN 1873-376X, Vol. 995, p. 38-45Article in journal (Refereed)
    Abstract [en]

    In the present study, the modification of a polysulfone hollow fiber membrane with in situ molecularly imprinted sol-gel process (as a novel and one-step method) was prepared and investigated. 3-(propylmethaaylate)trimethoxysilane (3PMTMOS) as an inorganic precursor was used for preparation of molecularly imprinted sol-gel. The modified molecularly imprinted sol-gel hollow fiber membrane (MSHM) was used for the liquid-phase microextraction (LPME) of hippuric acid (HA) in human plasma and urine samples. MSHM as a selective, robust, and durable tool was used for at least 50 extractions without significant decrease in the extraction efficiency. The non-molecularly imprinted sol-gel hollow fiber membrane (NSHM) as blank hollow fiber membrane was prepared by the same process, only without HA. To achieve the best condition, influential parameters on the extraction efficiency were thoroughly investigated. The capability of this robust, green, and simple method for extraction of HA was successfully accomplished with LC/MS/MS. The limits of detection (LOD) and quantification (LOQ) in human plasma and urine samples were 0.3 and 1.0 nmol L-1, respectively. The standard calibration curves were obtained within the concentration range 1-2000 nmol L-1 for HA in human plasma and urine. The coefficients of determination (r(2)) were >= 0.998. The obtained data exhibited recoveries were higher than 89% for the extraction of HA in human plasma and urine samples.

  • 16. Möller, Kristina
    et al.
    Davies, Ronnie
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Fred, Charlotta
    Törnqvist, Margareta
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Evaluation of molecularly imprinted solid-phase extraction for a 1,2:3,4-diepoxybutane adduct to valine in haemoglobin2010In: Journal of chromatography. B, ISSN 1570-0232, E-ISSN 1873-376X, Vol. 878, no 27, p. 2497-2501Article in journal (Refereed)
    Abstract [en]

    A molecularly imprinted polymer, MIP, was prepared and evaluated as SPE sorbent for a cyclicized adduct formed to N-terminal valine (Pyr-Val) in hemoglobin from 1,2:3,4-diepoxybutane (DEB). This metabolite plays an important role in the carcinogenesis of 1,3-butadiene. The hydrazide of Pyr-Val, formed after hydrazinolysis of hemoglobin, as well as necessary standards was synthesized. The MIP was prepared from methacrylic acid with a structure analogue to the investigated adduct as template and the method was developed for aqueous conditions. Selective desorption was achieved when the sample was washed with water after loading in 10% acetonitrile. The primary interaction with the binding sites in the imprints was most likely of ionic character. Quantification of the Pyr-Val adduct was performed with LC/ESI-MS/MS, yielding an instrumental LOD of 150 pg injected amount.

  • 17. Said, Rana
    et al.
    Pohanka, Anton
    Abdel-Rehim, Mohamed
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Beck, Olof
    Determination of four immunosuppressive drugs in whole blood using meps and lc ms/ms allowing automated sample work up and analysis2012In: Journal of chromatography. B, ISSN 1570-0232, E-ISSN 1873-376X, Vol. 897, p. 42-49Article in journal (Refereed)
    Abstract [en]

    In treatment with immunosuppressive drugs, monitoring of blood drug concentration is needed. The aim of this work was to explore micro extraction by packed sorbent (MEPS) as a possible on-line sample preparation method in combination with liquid chromatography-tandem mass spectrometry (LC-MS/MS) for quantification of cyclosporine, everolimus, sirolimus and tacrolimus in whole blood. An automated on-line MEPS system connected with a LC-MS/MS instrument was set up. A C-8 sorbent was used for the MEPS extraction. Subsequent analysis was performed with a gradient LC system. The adduct ions [M + NH4](+) of the analytes were monitored in SRM mode for quantification. Ascomycin and cyclosporine D were used as internal standards. The chromatographic run time 2.5 min and the quantification ranges were 3-1500 ng/mL (r(2) >= 0.999, n = 6) for cyclosporine and 0.5-50 ng/mL for everolimus, sirolimus and tacrolimus (r(2) >= 0.998. 0.994 and 0.993, respectively, n = 6). Precision and accuracy were documented at three levels. Accuracy results were between 102% and 109% with precision between 2% and 13% and carry over < 0.02%. Matrix effects were characterized and found to be below 20%. The quantifications obtained were in agreement with a reference LC-MS/MS method based on protein precipitation, and results obtained from external proficiency test samples compared with the mean of all other LC-mass spectrometry methods showed good agreement. This method provides an accurate, precise and automated procedure that can be applied for therapeutic drug monitoring of immunosuppressive drugs in clinical laboratories equipped with LC-MS/MS.

  • 18.
    Saleh, Aljona
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Stephanson, Niclas Nicolai
    Granelli, Ingrid
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Villen, Tomas
    Beck, Olof
    Evaluation of a direct high-capacity target screening approach for urine drug testing using liquid chromatography-time-of-flight mass spectrometry2012In: Journal of chromatography. B, ISSN 1570-0232, E-ISSN 1873-376X, no 909, p. 6-13Article in journal (Refereed)
    Abstract [en]

    In this study a rapid liquid chromatography-time-of-flight mass spectrometry method was developed, validated and applied in order to evaluate the potential of this technique for routine urine drug testing. Approximately 800 authentic patient samples were analyzed for amphetamines (amphetamine and methamphetamine), opiates (morphine, morphine-3-glucuronide, morphine-6-glucuronide, codeine and codeine-6-glucuronide) and buprenorphines (buprenorphine and buprenorphine-glucuronide) using immunochemical screening assays and mass spectrometry confirmation methods for comparison. The chromatographic application utilized a rapid gradient with high flow and a reversed phase column with 1.8 mu m particles. Total analysis time was 4 min. The mass spectrometer operated with an electrospray interface in positive mode with a resolution power of >10,000 at m/z 956. The applied reporting limits were 100 ng/mL for amphetamines and opiates, and 5 ng/mL for buprenorphines, with lower limits of quantification were 2.8-41 ng/mL. Calibration curves showed a linear response with coefficients of correlation of 0.97-0.99. The intra- and interday imprecision in quantification at the reporting limits were <10% for all analytes but for buprenorphines <20%. Method validation data met performance criteria for a qualitative and quantitative method. The liquid chromatography-time-of-flight mass spectrometry method was found to be more selective than the immunochemical method by producing lower rates of false positives (0% for amphetamines and opiates; 3.2% for buprenorphines) and negatives (1.8% for amphetamines; 0.6% for opiates; 0% for buprenorphines). The overall agreement between the two screening methods was between 94.2 and 97.4%. Comparison of data with the confirmation (LC-MS) results for all individual 9 analytes showed that most deviating results were produced in samples with low levels of analytes. False negatives were mainly related to failure of detected peak to meet mass accuracy criteria (+/- 20 mDa). False positives was related to presence of interfering peaks meeting mass accuracy and retention time criteria and occurred mainly at low levels. It is concluded that liquid chromatography-time-of-flight mass spectrometry has potential both as a complement and as replacement of immunochemical screening assays.

  • 19.
    Thuy, Tran Thi
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Inganas, Mats
    Ekstrand, Gunnar
    Thorsén, Gunnar
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Parallel sample preparation of proteins, from crude samples to crystals ready for MALDI-MS, in an integrated microfluidic system2010In: Journal of chromatography. B, ISSN 1570-0232, E-ISSN 1873-376X, Vol. 878, no 28, p. 2803-2810Article in journal (Refereed)
    Abstract [en]

    A microfluidic structure is presented where selective capture of proteins in complex samples, followed by clean-up, enzymatic processing, and MALDI-MS sample preparation of peptides generated, can be performed. The structure uses an affinity column to capture the protein while all other components in the sample are disposed of. The protein of interest is then eluted from the affinity column and captured on a second column on which the enzymatic processing is performed. Salts and hydrophilic contaminants are then removed before the products from the enzymatic reaction are eluted together with a suitable MALDI matrix and the solvent evaporated in a designated MALDI target structure. All steps can be performed automatically in 54 parallel microstructures on a microfluidic compact disc. The process is demonstrated by the selective capture and tryptic digest of recombinant IgG molecules from samples containing other proteins: an excess of bovine serum albumin or spent cell culture media.

  • 20.
    von Stedingk, Hans
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Davies, Ronnie
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Rydberg, Per
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Törnqvist, Margareta
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Methyl vinyl ketone – identification and quantification of adduct to N-terminal valine in human haemoglobin2010In: Journal of chromatography. B, ISSN 1570-0232, E-ISSN 1873-376X, Vol. 878, no 27, p. 2491-2496Article in journal (Refereed)
    Abstract [en]

    Adducts to N-terminal valines in Hb have been shown useful as biomarkers of exposure to electrophilic compounds. Adducts from many compounds have earlier been measured with a modified Edman degradation method using a GC–MS/MS method. A recently developed method, the adduct FIRE procedure™, adopted for analysis by LC–MS/MS, has been applied in this study. With this method a fluorescein isothiocyanate (FITC) reagent is used to measure adducts (R) from electrophiles with a modified Edman procedure. By using LC–MS/MS in product ion scan mode, a new peak was identified and the obtained MS data indicated that this adduct could originate from methyl vinyl ketone (MVK). Incubation of human-, sheep- and bovine blood with MVK increased the signal of the identified peak. By comparing the LC–MS/MS data from the unknown background peak with data obtained from synthesized fluorescein thiohydantoin (FTH) standards of the MVK adduct to valine and d8-valine, the identity of this adduct was confirmed. The MVK adduct was shown present in human blood (35 pmol/g globin, n = 3) and only just above LOD in bovine blood, n = 1 (LOD = 2 pmol/g globin). MVK reacts, in similarity with acrylamide, via Michael addition. MVK is known to occur in the environment and has earlier been observed in biological samples, which means that there are possible natural and anthropogenic exposure sources. Analysis of an Hb adduct from MVK in humans has to our knowledge not been described before.

  • 21.
    von Stedingk, Hans
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Rydberg, Per
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Törnqvist, Margareta
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    A new modified Edman procedure for analysis of N-terminal valine adducts in hemoglobin by LC-MS/MS2010In: Journal of chromatography. B, ISSN 1570-0232, E-ISSN 1873-376X, Vol. 878, no 27, p. 2483-2490Article in journal (Refereed)
    Abstract [en]

    A rapid and sensitive method using liquid chromatography-tandem mass spectrometry (LC-MS/MS) for simultaneous determination of adducts from acrylamide, glycidamide and ethylene oxide to N-terminal valines in hemoglobin (Hb) was developed. This new procedure is based on the same principles as the N-alkyl Edman procedure for analysis of adducts from electrophilic agents to N-terminal valines in Hb. The N-substituted valines can be detached, enriched and measured selectively as thiohydantoins by the use of an Edman reagent, in this case fluorescein isothiocyanate (FITC). This procedure is denoted as the "adduct FIRE procedure" as the FITC reagent is used for measurement of adducts ((R) under bar) formed from electrophilic compounds with a modified Edman procedure. In this study, fluorescein thiohydantoin (FTH) analytes of N-substituted valines from acrylamicle, glycidamide and ethylene oxide, as well as their corresponding hepta- and tri-deuterium-substituted analogues, were synthesized. These analytes (n = 8) were then characterized by LC-MS/MS (ESI, positive ion mode) and obtained product ions were interpreted. A considerable work with optimization of the FIRE procedure (TM), resulted in a procedure in which low background levels of the studied adducts could be measured from 250 mu L lyzed whole blood samples (human non-smokers). The analytes were enriched and purified with solid phase extraction columns and analyzed by LC-MS/MS with LOQ clown to 1 pmol adduct/g Hb. Compared to other procedures for determination of N-terminal Hb adducts, the introduction of FITC has led to a simplified procedure, where whole blood also can be used, giving new opportunities and reduced hand on time with increased sample throughput.

  • 22. Yang, Liu
    et al.
    Said, Rana
    Abdel-Rehim, Mohamed
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Sorbent, device, matrix and application in microextraction by packed sorbent (MEPS): A review2017In: Journal of chromatography. B, ISSN 1570-0232, E-ISSN 1873-376X, Vol. 1043, p. 33-43Article, review/survey (Refereed)
    Abstract [en]

    Microextraction by packed sorbent (MEPS) is a new miniaturized form of solid-phase extraction and it is a green sample pretreatment technology. MEPS has been widely accepted and used by several research groups online or offline as a sample preparation technique before instrument analysis. MEPS reduces the sample handling time and organic solvent consumption. MEPS is suitable for small sample volumes and can easily be connected with different chromatographic techniques without modification. The sorbent bed in MEPS is integrated into a liquid handling syringe that allows for low void volume sample manipulations either manually or in combination with laboratory robotics. MEPS is a simple, fast and robust sample preparation technique with several advantages, miniaturization, automation, fast operation course, on-line coupling with analytical instruments and low-cost operation with less solvent and low sample consumption. Sorbent type, device, and matrix are important factors in MEPS research and applications. The performance of MEPS has recently been illustrated by online with liquid chromatography-mass spectrometry and gas chromatography-mass spectrometry assays for pharmaceutical, environmental, and food analyses. This paper deals with MEPS device-optimized sorbent, sample matrix, and application. The progress and potential development of the technique are also discussed.

1 - 22 of 22
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