The Experts below are selected from a list of 249 Experts worldwide ranked by ideXlab platform
Emily P Chang - One of the best experts on this subject based on the ideXlab platform.
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analysis of aldehydes in excipients used in liquid semi solid formulations by gas chromatography Negative Chemical Ionization mass spectrometry
Journal of Chromatography A, 2007Co-Authors: Zhong Li, Brian M Kozlowski, Emily P ChangAbstract:Abstract Monitoring of low-molecular-weight aldehyde levels in excipients used in liquid/semi-solid based capsule (LFC) dosage forms plays a critical role in the development of these pharmaceutical products. A simple, sensitive and specific method based on gas chromatography coupled with mass spectrometry (GC–MS) utilizing an Rtx-5MS capillary column was developed and validated for the detection and quantification of C1–C8 aliphatic aldehydes in LFC excipients at sub-μg/g levels. The proposed procedure is based on the derivatization of aldehydes in 10:1 (v/v) acetonitrile:water with O-2,3,4,5,6-(pentafluorobenzyl) hydroxylamine hydrochloride (PFBHA), followed by direct GC analysis of aldehyde-PFBHA-oxime derivatives with Negative Chemical Ionization (NCI) MS detection. The method developed was successfully applied to the analysis of short chain aldehydes in 30 typical LFC excipients. An example case study on the formation and growth of aldehydes in these excipients under accelerated storage conditions is also reported.
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Analysis of aldehydes in excipients used in liquid/semi-solid formulations by gas chromatography–Negative Chemical Ionization mass spectrometry
Journal of Chromatography A, 2007Co-Authors: Zhong Li, Brian M Kozlowski, Emily P ChangAbstract:Abstract Monitoring of low-molecular-weight aldehyde levels in excipients used in liquid/semi-solid based capsule (LFC) dosage forms plays a critical role in the development of these pharmaceutical products. A simple, sensitive and specific method based on gas chromatography coupled with mass spectrometry (GC–MS) utilizing an Rtx-5MS capillary column was developed and validated for the detection and quantification of C1–C8 aliphatic aldehydes in LFC excipients at sub-μg/g levels. The proposed procedure is based on the derivatization of aldehydes in 10:1 (v/v) acetonitrile:water with O-2,3,4,5,6-(pentafluorobenzyl) hydroxylamine hydrochloride (PFBHA), followed by direct GC analysis of aldehyde-PFBHA-oxime derivatives with Negative Chemical Ionization (NCI) MS detection. The method developed was successfully applied to the analysis of short chain aldehydes in 30 typical LFC excipients. An example case study on the formation and growth of aldehydes in these excipients under accelerated storage conditions is also reported.
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Analysis of aldehydes in excipients used in liquid/semi-solid formulations by gas chromatography-Negative Chemical Ionization mass spectrometry.
Journal of chromatography. A, 2007Co-Authors: Zhong Li, Brian M Kozlowski, Emily P ChangAbstract:Monitoring of low-molecular-weight aldehyde levels in excipients used in liquid/semi-solid based capsule (LFC) dosage forms plays a critical role in the development of these pharmaceutical products. A simple, sensitive and specific method based on gas chromatography coupled with mass spectrometry (GC-MS) utilizing an Rtx-5MS capillary column was developed and validated for the detection and quantification of C1-C8 aliphatic aldehydes in LFC excipients at sub-microg/g levels. The proposed procedure is based on the derivatization of aldehydes in 10:1 (v/v) acetonitrile:water with O-2,3,4,5,6-(pentafluorobenzyl) hydroxylamine hydrochloride (PFBHA), followed by direct GC analysis of aldehyde-PFBHA-oxime derivatives with Negative Chemical Ionization (NCI) MS detection. The method developed was successfully applied to the analysis of short chain aldehydes in 30 typical LFC excipients. An example case study on the formation and growth of aldehydes in these excipients under accelerated storage conditions is also reported.
David A Herold - One of the best experts on this subject based on the ideXlab platform.
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serum total testosterone immunoassay compared with Negative Chemical Ionization gas chromatography mass spectrometry
Clinical Chemistry, 1996Co-Authors: Robert L Fitzgerald, David A HeroldAbstract:We have developed an electron capture Negative Chemical Ionization gas chromatography-mass spectrometry (GC-MS) procedure to quantify serum testosterone in the clinically relevant range 0.69-69.3 nmol/L and used this procedure to assess Ciba Corning Diagnostics ACS:180 testosterone immunoassay. The GC-MS method involves liquid-liquid extraction of serum samples and synthesis of a pentafluorobenzyloxime/silyl ether derivative of testosterone with excellent chromatographic and electron capturing properties. The ACS testosterone assay is the first fully automated nonradioactive testosterone immunoassay approved by the US Food and Drug Administration. Patients' specimens (101, 57 males, 44 females) were analyzed by both techniques. A plot of the GC-MS (x) vs ACS (y) testosterone concentrations for men was linear (y = 1.07x + 0.19 nmol/L), showing excellent correlation (r2 = 0.98) between the two assays. Agreement of the two assays for female specimens was poor (y = 0.72x + 1.2 nmol/L), with a poor correlation (r2 = 0.31).
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Determination of blood lead by electron-capture Negative Chemical Ionization gas chromatography-mass spectrometry
Clinical Chemistry, 1996Co-Authors: Geoffrey S. Baird, Robert L Fitzgerald, Suresh K. Aggarwal, David A HeroldAbstract:An electron-capture Negative Chemical Ionization (NCI) gas chromatography-mass spectrometry (GC-MS) method for determination of lead (Pb) in blood samples is described. Extraction of Pb from the sample does not involve hot digestion but is based on treatment at ambient temperature. The blood sample is supplemented with a known amount of internal standard (204Pb) for isotope dilution and is treated with concentrated nitric acid. After adjusting the pH to 7, the Pb is extracted into toluene as the pyrrolidine-dithiocarbamate chelate. Samples are then derivatized with 4- fluorophenylmagnesium bromide to form Pb(FC6H4)4. The use of NCI offers enhanced sensitivity (by 75-fold better than previously used electron Ionization), gives good precision and accuracy, and has no observable memory effect. The isotope dilution GCoff methodology typically agreed within 2-3% of expected values for the College of American Pathologists blood Pb specimens and the National Institute of Standards and Technology Standard Reference Material 955a.
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detecting benzodiazepines immunoassays compared with Negative Chemical Ionization gas chromatography mass spectrometry
Clinical Chemistry, 1994Co-Authors: Robert L Fitzgerald, Douglas A Rexin, David A HeroldAbstract:We tested 231 urine samples by six immunoassay methods--EMIT d.a.u., EMIT II, Roche Abuscreen Online, Abbott TDx, Diagnostic Products Corp. (DPC) double-antibody radioimmunoassay (RIA), and Biosite Triage--and by Negative Chemical Ionization gas chromatography/mass spectrometry to determine how the immunoassays performed on samples selected for suspected benzodiazepine use (n = 100) and in random urine drug screening (n = 131). In general, all of the assays were successful in detecting oxazepam and related metabolites, even at concentrations below the stated cutoffs. However, the Negative predictive value of benzodiazepine immunoassays for samples selected for suspected benzodiazepine use ranged from 86% to 96%. A primary difference between the test kits was the ability of DPC RIA and Triage to detect lorazepam when other assays did not. Contrary to previous reports, pretreatment of specimens with glucuronidase was not necessary to detect oxazepam-related metabolites with these immunoassays.
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Detecting benzodiazepines: immunoassays compared with Negative Chemical Ionization gas chromatography/mass spectrometry.
Clinical Chemistry, 1994Co-Authors: Robert L Fitzgerald, Douglas A Rexin, David A HeroldAbstract:We tested 231 urine samples by six immunoassay methods--EMIT d.a.u., EMIT II, Roche Abuscreen Online, Abbott TDx, Diagnostic Products Corp. (DPC) double-antibody radioimmunoassay (RIA), and Biosite Triage--and by Negative Chemical Ionization gas chromatography/mass spectrometry to determine how the immunoassays performed on samples selected for suspected benzodiazepine use (n = 100) and in random urine drug screening (n = 131). In general, all of the assays were successful in detecting oxazepam and related metabolites, even at concentrations below the stated cutoffs. However, the Negative predictive value of benzodiazepine immunoassays for samples selected for suspected benzodiazepine use ranged from 86% to 96%. A primary difference between the test kits was the ability of DPC RIA and Triage to detect lorazepam when other assays did not. Contrary to previous reports, pretreatment of specimens with glucuronidase was not necessary to detect oxazepam-related metabolites with these immunoassays.
Zhong Li - One of the best experts on this subject based on the ideXlab platform.
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analysis of aldehydes in excipients used in liquid semi solid formulations by gas chromatography Negative Chemical Ionization mass spectrometry
Journal of Chromatography A, 2007Co-Authors: Zhong Li, Brian M Kozlowski, Emily P ChangAbstract:Abstract Monitoring of low-molecular-weight aldehyde levels in excipients used in liquid/semi-solid based capsule (LFC) dosage forms plays a critical role in the development of these pharmaceutical products. A simple, sensitive and specific method based on gas chromatography coupled with mass spectrometry (GC–MS) utilizing an Rtx-5MS capillary column was developed and validated for the detection and quantification of C1–C8 aliphatic aldehydes in LFC excipients at sub-μg/g levels. The proposed procedure is based on the derivatization of aldehydes in 10:1 (v/v) acetonitrile:water with O-2,3,4,5,6-(pentafluorobenzyl) hydroxylamine hydrochloride (PFBHA), followed by direct GC analysis of aldehyde-PFBHA-oxime derivatives with Negative Chemical Ionization (NCI) MS detection. The method developed was successfully applied to the analysis of short chain aldehydes in 30 typical LFC excipients. An example case study on the formation and growth of aldehydes in these excipients under accelerated storage conditions is also reported.
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Analysis of aldehydes in excipients used in liquid/semi-solid formulations by gas chromatography–Negative Chemical Ionization mass spectrometry
Journal of Chromatography A, 2007Co-Authors: Zhong Li, Brian M Kozlowski, Emily P ChangAbstract:Abstract Monitoring of low-molecular-weight aldehyde levels in excipients used in liquid/semi-solid based capsule (LFC) dosage forms plays a critical role in the development of these pharmaceutical products. A simple, sensitive and specific method based on gas chromatography coupled with mass spectrometry (GC–MS) utilizing an Rtx-5MS capillary column was developed and validated for the detection and quantification of C1–C8 aliphatic aldehydes in LFC excipients at sub-μg/g levels. The proposed procedure is based on the derivatization of aldehydes in 10:1 (v/v) acetonitrile:water with O-2,3,4,5,6-(pentafluorobenzyl) hydroxylamine hydrochloride (PFBHA), followed by direct GC analysis of aldehyde-PFBHA-oxime derivatives with Negative Chemical Ionization (NCI) MS detection. The method developed was successfully applied to the analysis of short chain aldehydes in 30 typical LFC excipients. An example case study on the formation and growth of aldehydes in these excipients under accelerated storage conditions is also reported.
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Analysis of aldehydes in excipients used in liquid/semi-solid formulations by gas chromatography-Negative Chemical Ionization mass spectrometry.
Journal of chromatography. A, 2007Co-Authors: Zhong Li, Brian M Kozlowski, Emily P ChangAbstract:Monitoring of low-molecular-weight aldehyde levels in excipients used in liquid/semi-solid based capsule (LFC) dosage forms plays a critical role in the development of these pharmaceutical products. A simple, sensitive and specific method based on gas chromatography coupled with mass spectrometry (GC-MS) utilizing an Rtx-5MS capillary column was developed and validated for the detection and quantification of C1-C8 aliphatic aldehydes in LFC excipients at sub-microg/g levels. The proposed procedure is based on the derivatization of aldehydes in 10:1 (v/v) acetonitrile:water with O-2,3,4,5,6-(pentafluorobenzyl) hydroxylamine hydrochloride (PFBHA), followed by direct GC analysis of aldehyde-PFBHA-oxime derivatives with Negative Chemical Ionization (NCI) MS detection. The method developed was successfully applied to the analysis of short chain aldehydes in 30 typical LFC excipients. An example case study on the formation and growth of aldehydes in these excipients under accelerated storage conditions is also reported.
Weijian Shen - One of the best experts on this subject based on the ideXlab platform.
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Determination of fipronil and its metabolites in eggs and egg products with gas chromatography-Negative Chemical Ionization-mass spectrometry
Chinese Journal of Chromatography, 2017Co-Authors: Weijian Shen, Rui Zhang, Keyao Yu, Hong WangAbstract:A method was established for the determination of fipronil and its metabolites in eggs and egg products with gas chromatography-Negative Chemical Ionization-mass spectrometry (GC-NCI-MS). The targets were extracted from samples with acetonitrile, and followed by a simple cleanup step known as dispersive solid-phase extraction QuEChERS. The extracts were determined by GC-NCI-MS, and quantified by external standard method with matrix correction standard curves. The recoveries were in the range of 87.0% to 99.3% at four spiked levels (0.1, 2.0, 4.0 and 20.0 μg/kg), and all RSDs were not more than 12.7% for the four analytes. The linearity of the method was good between 0.005 and 0.10 mg/L, and all LOQs were less than 0.10 μg/kg. So this method can be used to determine the residues of fipronil and its metabolites in eggs and egg products.
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Determination of trifluralin residue in aquatic products and edible oils by gas chromatography-Negative Chemical Ionization mass spectrometry
Chinese Journal of Chromatography, 2014Co-Authors: Wang L, Weijian Shen, Shen C, Wu B, Rui Zhang, Xia G, Lu H, Zhao ZAbstract:A confirmatory method was established for the determination of trifluralin residue in aquatic products and edible oils with the technique of offline disperse solid phase extraction and gas chromato g ra p h y-Negative Chemical Ionization mass spectrometry(DSPE-GC-MS/NCI).Trifluralin was extracted from aquatic products and edible oils with acetonitrile,and liquid-liquid partitioning formed by adding anhydrous magnesium sulfate followed by a simple cleanup step known as dispersive solid-phase extraction.The aliquot was analyzed by GC-MS/NCI using isotope internal standard method.The method was reliable and stable.The recoveries of trifluralin were in the range from80%to 100% at three spiked levels of 1.0,2.0,and 3.0μg/k g,and the RSDs were not more than 10.3%.The linearity of method was good from1 to 40μg/L,and the LOD was 0.02μg/k g.This method can be used as a conclusive evidence method for the determination of trifluralin residue in aquatic products and edible oils.
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Determination of 17 pyrethroid pesticide residues in vegetables by gas chromatography-mass spectrometry with Negative Chemical Ionization
Chinese Journal of Chromatography, 2013Co-Authors: Weijian Shen, Zhao Z, Shen C, Cao X, Rui Zhang, Fan X, Wu BAbstract:A method was established for the determination of 17 pyrethroid pesticide residues in vegetables using QuEChERS(quick,easy,cheap,effective,rugged and safe) clean-up method and gas chromatography-mass spectrometry(GC-MS) with Negative Chemical Ionization(NCI).The pyrethroid pesticides in the sample were extracted with acetonitrile.After QuEChERS clean-up with a mixture of primary secondary amine and graphitized carbon black packings,the extract was analyzed by GC-NCI-MS in selected ion monitoring(SIM) mode.An isotope internal standard of cypermethrin was employed to the quantification.The limits of quantification ranged from 0.02 to 5 μg/kg.The recoveries of the pyrethroid pesticides spiked in three different matrixes(peas,broccoli and Chinese onion green) at four spiked levels of 10,20,30 and 100 μg/kg were from 71.0% to 139.0%,and the relative standard deviations were less than 12.8%.This method can be used as a conclusive evidence method of the 17 pyrethroid pesticide residues in vegetables.
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Determination of triadimenol residue in foods with dispersive solid phase extraction cleanup by gas chromatography-Negative Chemical Ionization mass spectrometry
Chinese Journal of Chromatography, 2008Co-Authors: Weijian Shen, Lin H, Zhao Z, Ding T, Xu J, Shen CAbstract:A confirmatory method is presented for the determination of triadimenol residue in foods by dispersive solid phase extraction-gas chromatography-Negative Chemical Ionization mass spectrometry(SPE-GC-NCI/MS).Triadimenol residue was extracted from different food samples,such as snow pea,carrot,orange,bean,spinach,oolong tea,rice,beef,longsnout catfish,royel jelly,red swamp crayfish,bee honey etc with acetonitrile containing 1% acetic acid and simultaneous liquid-liquid partitioning formed by adding anhydrous magnesium sulfate plus sodium acetate,followed by a simple clean-up step known by dispersive solid-phase extraction.The aliquot was determined and confirmed by gas chromatography-Negative Chemical Ionization mass spectrometry using external standard method.The average recoveries at the three spiked levels(0.005,0.010 and 0.020 mg/kg) in different samples ranged from 70% to 110%,and the relative standard deviations were lower than 12.0%.The linearity of detection ranged from 0.050 to 0.750 mg/L.The detection limit of the method was 0.001 mg/kg and the limit of quantification was 0.003 mg/kg.The method is selective with no interference and suitable for confirmatory of triadimenol residue in 12 categories of foods.
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Determination of cyflufenamid residue in carrots by gas chromatography-Negative Chemical Ionization mass spectrometry
Chinese Journal of Chromatography, 2008Co-Authors: Yang W, Weijian Shen, Zhao Z, Xu J, Shen C, Wu BAbstract:A method was developed for the determination of cyflufenamid residue in carrots by solid phase extraction-gas chromatography-Negative Chemical Ionization mass spectrometry (SPE-GC-NCI/MS). Cyflufenamid residue was extracted with ethyl acetate from carrots. The extract was cleaned-up by an active carbon SPE column connected to a neutral alumina SPE column. The analysis was carried out by the GC-NCI/MS with selected ion monitoring mode. The recoveries of cyflufenamid in carrot samples were in the range from 74.9% to 94.6% at four spiked levels, 0.005, 0.01, 0.02, 0.04 mg/kg, and the relative standard deviations (RSD) were less than 9.7% for inter-days. The linearity of the method was good in the range from 10 to 1000 ng/mL, and the limit of detection (LOD) was 0.001 mg/kg, and the limit of quantitation (LOQ) was 0.005 mg/kg. The method is selective without interference and is suitable for the determination and confirmation of cyflufenamid residue in carrots.
Robert L Fitzgerald - One of the best experts on this subject based on the ideXlab platform.
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serum total testosterone immunoassay compared with Negative Chemical Ionization gas chromatography mass spectrometry
Clinical Chemistry, 1996Co-Authors: Robert L Fitzgerald, David A HeroldAbstract:We have developed an electron capture Negative Chemical Ionization gas chromatography-mass spectrometry (GC-MS) procedure to quantify serum testosterone in the clinically relevant range 0.69-69.3 nmol/L and used this procedure to assess Ciba Corning Diagnostics ACS:180 testosterone immunoassay. The GC-MS method involves liquid-liquid extraction of serum samples and synthesis of a pentafluorobenzyloxime/silyl ether derivative of testosterone with excellent chromatographic and electron capturing properties. The ACS testosterone assay is the first fully automated nonradioactive testosterone immunoassay approved by the US Food and Drug Administration. Patients' specimens (101, 57 males, 44 females) were analyzed by both techniques. A plot of the GC-MS (x) vs ACS (y) testosterone concentrations for men was linear (y = 1.07x + 0.19 nmol/L), showing excellent correlation (r2 = 0.98) between the two assays. Agreement of the two assays for female specimens was poor (y = 0.72x + 1.2 nmol/L), with a poor correlation (r2 = 0.31).
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Determination of blood lead by electron-capture Negative Chemical Ionization gas chromatography-mass spectrometry
Clinical Chemistry, 1996Co-Authors: Geoffrey S. Baird, Robert L Fitzgerald, Suresh K. Aggarwal, David A HeroldAbstract:An electron-capture Negative Chemical Ionization (NCI) gas chromatography-mass spectrometry (GC-MS) method for determination of lead (Pb) in blood samples is described. Extraction of Pb from the sample does not involve hot digestion but is based on treatment at ambient temperature. The blood sample is supplemented with a known amount of internal standard (204Pb) for isotope dilution and is treated with concentrated nitric acid. After adjusting the pH to 7, the Pb is extracted into toluene as the pyrrolidine-dithiocarbamate chelate. Samples are then derivatized with 4- fluorophenylmagnesium bromide to form Pb(FC6H4)4. The use of NCI offers enhanced sensitivity (by 75-fold better than previously used electron Ionization), gives good precision and accuracy, and has no observable memory effect. The isotope dilution GCoff methodology typically agreed within 2-3% of expected values for the College of American Pathologists blood Pb specimens and the National Institute of Standards and Technology Standard Reference Material 955a.
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detecting benzodiazepines immunoassays compared with Negative Chemical Ionization gas chromatography mass spectrometry
Clinical Chemistry, 1994Co-Authors: Robert L Fitzgerald, Douglas A Rexin, David A HeroldAbstract:We tested 231 urine samples by six immunoassay methods--EMIT d.a.u., EMIT II, Roche Abuscreen Online, Abbott TDx, Diagnostic Products Corp. (DPC) double-antibody radioimmunoassay (RIA), and Biosite Triage--and by Negative Chemical Ionization gas chromatography/mass spectrometry to determine how the immunoassays performed on samples selected for suspected benzodiazepine use (n = 100) and in random urine drug screening (n = 131). In general, all of the assays were successful in detecting oxazepam and related metabolites, even at concentrations below the stated cutoffs. However, the Negative predictive value of benzodiazepine immunoassays for samples selected for suspected benzodiazepine use ranged from 86% to 96%. A primary difference between the test kits was the ability of DPC RIA and Triage to detect lorazepam when other assays did not. Contrary to previous reports, pretreatment of specimens with glucuronidase was not necessary to detect oxazepam-related metabolites with these immunoassays.
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Detecting benzodiazepines: immunoassays compared with Negative Chemical Ionization gas chromatography/mass spectrometry.
Clinical Chemistry, 1994Co-Authors: Robert L Fitzgerald, Douglas A Rexin, David A HeroldAbstract:We tested 231 urine samples by six immunoassay methods--EMIT d.a.u., EMIT II, Roche Abuscreen Online, Abbott TDx, Diagnostic Products Corp. (DPC) double-antibody radioimmunoassay (RIA), and Biosite Triage--and by Negative Chemical Ionization gas chromatography/mass spectrometry to determine how the immunoassays performed on samples selected for suspected benzodiazepine use (n = 100) and in random urine drug screening (n = 131). In general, all of the assays were successful in detecting oxazepam and related metabolites, even at concentrations below the stated cutoffs. However, the Negative predictive value of benzodiazepine immunoassays for samples selected for suspected benzodiazepine use ranged from 86% to 96%. A primary difference between the test kits was the ability of DPC RIA and Triage to detect lorazepam when other assays did not. Contrary to previous reports, pretreatment of specimens with glucuronidase was not necessary to detect oxazepam-related metabolites with these immunoassays.
