N-(Trifluoroacetyl)-l-prolyl- (N-TFA-l-prolyl-) d- and l-amphetamine diastereoisomers were separa... more N-(Trifluoroacetyl)-l-prolyl- (N-TFA-l-prolyl-) d- and l-amphetamine diastereoisomers were separated by high-performance liquid chromatography and confirmed by an interfaced mass spectrometer system, using the commercially available N-3,5-(dinitrobenzoyl)phenylglycine chiral column. A separation factor of 1.52 and resolution of 3.8 were observed. N-TFA-l-prolyl-d- and -l-methamphetamine diastereoisomers were only partially resolved. The chiral stationary phase-solute interactions were studied by varying the mobile phase (2-propanol in hexane). Results indicate the separation mechanism proceeds via dipolar and hydrogen-bond interactions between the chiral stationary phase and the solute. A modified "dipole-stacking" model takes into account these interactions and explains the difference in separability observed for N-TFA-l-prolyl-d- and -l-amphetamine and N-TFA-l-prolyl-d- and -l-methamphetamine.
Screening and confirming the presence of drugs and toxic compounds in various matrices are import... more Screening and confirming the presence of drugs and toxic compounds in various matrices are important and challenging tasks routinely faced by forensic and clinical laboratories. Recent advances in the liquid chromatographic and mass spectrometric technologies have provided an opportunity for the development of more specific and effective approaches to achieve the "screening" and "confirmation" goals in a single analytical step. The objectives of this study are: (i) the establishment of an ultra-high performance liquid chromatographic, quadrupole time-of-flight mass spectrometric mass spectrometric and MS-MS spectral database, including 1,200 compounds of interest; and (ii) the development of an effective protocol, using this database and three searching algorithms, for general unknown screening of these compounds. The established database and protocol were evaluated through the analysis of 30 external proficiency test and 100 postmortem samples and found to be si...
Isotopic analogs of the analytes are currently preferred internal standards (IS) for quantitative... more Isotopic analogs of the analytes are currently preferred internal standards (IS) for quantitative analyses of drugs and their metabolites in biological matrices by GC/MS procedures. Contributions of the analyte and the IS to the intensities of ions designated for the IS and the analyte, respectively--an undesirable phenomenon termed "cross-contribution"--greatly weakens the effectiveness of this approach. The cross-contribution phenomenon has been, in the past, evaluated by a "direct measurement" approach, in which intensities of interested ions were measured in two separate experiments using equal quantities of the analyte and the IS. Alternate procedures that may generate improved results are hereby studied. For the "improved direct measurement" approach, ion intensity data derived from the previously reported direct measurement procedure are first normalized before being used to calculate the extent of cross-contribution. An "internal standard" approach is also developed, in which a set amount of a third compound is incorporated into these two separate experiments, thus allowing corrections of ion intensity data that are imbedded with variations inherent to separate experiments. Finally, a "standard addition" approach, involving a series "addition" of "standards", generates multiple data points; thus, providing a mechanism to validate the resulting cross-contribution data. Secobarbital/(2)H(5)-secobarbital and secobarbital/(13)C(4)-secobarbital pairs are adapted as the exemplar systems for this study.
Recent implementation of urine drug-screening policies in the workplace has resulted in an increa... more Recent implementation of urine drug-screening policies in the workplace has resulted in an increase in the submission of substituted urine specimens. Donor verification of urine specimens often becomes necessary when the origin of a specimen is in question or when a positive drug test is contested. Methods reported for the identification of the urine donor include the analysis of blood group antigenic substances (ABH and Lewis systems), polymorphic proteins (group-specific component, haptoglobin, and orosomucoid), and deoxyribonucleic acid (DNA). Since the concentrations of the antigenic substances and polymorphic proteins in urine are typically low, most serological procedures adapt a concentration step enhancing the presence of these substances in the resulting residue by a factor ranging from 100 to 3,000. Conventional (and a two-dimensional) absorption-inhibition and electrophoresis procedures can then be applied to characterize the antigenic substances and polymorphic proteins....
A simple and selective HPLC method for simultaneous determination and quantification of anthraqui... more A simple and selective HPLC method for simultaneous determination and quantification of anthraquinones, lignans and flavonoids in Xiao-Cheng-Qi Tang (XCQT), Hou-Po-San-Wu Tang (HPSWT) and Hou-Po-Da-Huang Tang (HPDHT) was developed and validated. An Agilent Zorbax SB-C 18 (4.6 mm x 250 mm, 5 µm) column with the mobile phase of acetonitrile and 0.5% acetic acid aqueous solution in gradient elution mode was used. The flow rate was 1.0 mL · min(-1) at 30 °C, and injection volume was 10 µL. The detection wavelength was set at 254 nm and 294 nm simultaneously for the quantitative analysis. The current HPLC assay was validated for linearity, intra-day and inter-day precisions, accuracy, recovery and stability. The method was applied to the content comparison of the gallic acid, cinnamic acid, sennoside A, sennoside B, rhein, emodin, aloe-emodin, chrysophanol, physcion, magnolol, honokiol, narirutin, naringin, hesperidin, neohesperidin, hesperetin, naringenin and nobiletin in XCQT, HPSWT an...
N-(Trifluoroacetyl)-l-prolyl- (N-TFA-l-prolyl-) d- and l-amphetamine diastereoisomers were separa... more N-(Trifluoroacetyl)-l-prolyl- (N-TFA-l-prolyl-) d- and l-amphetamine diastereoisomers were separated by high-performance liquid chromatography and confirmed by an interfaced mass spectrometer system, using the commercially available N-3,5-(dinitrobenzoyl)phenylglycine chiral column. A separation factor of 1.52 and resolution of 3.8 were observed. N-TFA-l-prolyl-d- and -l-methamphetamine diastereoisomers were only partially resolved. The chiral stationary phase-solute interactions were studied by varying the mobile phase (2-propanol in hexane). Results indicate the separation mechanism proceeds via dipolar and hydrogen-bond interactions between the chiral stationary phase and the solute. A modified "dipole-stacking" model takes into account these interactions and explains the difference in separability observed for N-TFA-l-prolyl-d- and -l-amphetamine and N-TFA-l-prolyl-d- and -l-methamphetamine.
Screening and confirming the presence of drugs and toxic compounds in various matrices are import... more Screening and confirming the presence of drugs and toxic compounds in various matrices are important and challenging tasks routinely faced by forensic and clinical laboratories. Recent advances in the liquid chromatographic and mass spectrometric technologies have provided an opportunity for the development of more specific and effective approaches to achieve the "screening" and "confirmation" goals in a single analytical step. The objectives of this study are: (i) the establishment of an ultra-high performance liquid chromatographic, quadrupole time-of-flight mass spectrometric mass spectrometric and MS-MS spectral database, including 1,200 compounds of interest; and (ii) the development of an effective protocol, using this database and three searching algorithms, for general unknown screening of these compounds. The established database and protocol were evaluated through the analysis of 30 external proficiency test and 100 postmortem samples and found to be si...
Isotopic analogs of the analytes are currently preferred internal standards (IS) for quantitative... more Isotopic analogs of the analytes are currently preferred internal standards (IS) for quantitative analyses of drugs and their metabolites in biological matrices by GC/MS procedures. Contributions of the analyte and the IS to the intensities of ions designated for the IS and the analyte, respectively--an undesirable phenomenon termed "cross-contribution"--greatly weakens the effectiveness of this approach. The cross-contribution phenomenon has been, in the past, evaluated by a "direct measurement" approach, in which intensities of interested ions were measured in two separate experiments using equal quantities of the analyte and the IS. Alternate procedures that may generate improved results are hereby studied. For the "improved direct measurement" approach, ion intensity data derived from the previously reported direct measurement procedure are first normalized before being used to calculate the extent of cross-contribution. An "internal standard" approach is also developed, in which a set amount of a third compound is incorporated into these two separate experiments, thus allowing corrections of ion intensity data that are imbedded with variations inherent to separate experiments. Finally, a "standard addition" approach, involving a series "addition" of "standards", generates multiple data points; thus, providing a mechanism to validate the resulting cross-contribution data. Secobarbital/(2)H(5)-secobarbital and secobarbital/(13)C(4)-secobarbital pairs are adapted as the exemplar systems for this study.
Recent implementation of urine drug-screening policies in the workplace has resulted in an increa... more Recent implementation of urine drug-screening policies in the workplace has resulted in an increase in the submission of substituted urine specimens. Donor verification of urine specimens often becomes necessary when the origin of a specimen is in question or when a positive drug test is contested. Methods reported for the identification of the urine donor include the analysis of blood group antigenic substances (ABH and Lewis systems), polymorphic proteins (group-specific component, haptoglobin, and orosomucoid), and deoxyribonucleic acid (DNA). Since the concentrations of the antigenic substances and polymorphic proteins in urine are typically low, most serological procedures adapt a concentration step enhancing the presence of these substances in the resulting residue by a factor ranging from 100 to 3,000. Conventional (and a two-dimensional) absorption-inhibition and electrophoresis procedures can then be applied to characterize the antigenic substances and polymorphic proteins....
A simple and selective HPLC method for simultaneous determination and quantification of anthraqui... more A simple and selective HPLC method for simultaneous determination and quantification of anthraquinones, lignans and flavonoids in Xiao-Cheng-Qi Tang (XCQT), Hou-Po-San-Wu Tang (HPSWT) and Hou-Po-Da-Huang Tang (HPDHT) was developed and validated. An Agilent Zorbax SB-C 18 (4.6 mm x 250 mm, 5 µm) column with the mobile phase of acetonitrile and 0.5% acetic acid aqueous solution in gradient elution mode was used. The flow rate was 1.0 mL · min(-1) at 30 °C, and injection volume was 10 µL. The detection wavelength was set at 254 nm and 294 nm simultaneously for the quantitative analysis. The current HPLC assay was validated for linearity, intra-day and inter-day precisions, accuracy, recovery and stability. The method was applied to the content comparison of the gallic acid, cinnamic acid, sennoside A, sennoside B, rhein, emodin, aloe-emodin, chrysophanol, physcion, magnolol, honokiol, narirutin, naringin, hesperidin, neohesperidin, hesperetin, naringenin and nobiletin in XCQT, HPSWT an...
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