Jin Young Kim

Measurement of 19-nortestosterone and its esters in equine plasma by high-performance liquid chromatography with tandem mass spectrometry

A high-performance liquid chromatographic-tandem mass spectrometric (HPLC/MS/MS) method for the determination of 19-nortestosterone and its esters (cyclopentanepropionate, phenylpropionate, and decanoate) in equine plasma is achieved using an atmospheric pressure chemical ionization (APCI) interface in selected reaction monitoring (SRM) mode. The two internal standards used were 16,16, 17-(2)H(3)-19-nortestosterone for 19-nortestosterone and methenolone acetate for its esters. The steroids studied were extracted from plasma samples with a mixture of diethyl ether/n-hexane (9:1, v/v). The quantification limits for 19-nortestosterone, 19-nortestosterone cyclopentanepropionate, 19-nortestosterone phenylpropionate, and 19-nortestosterone decanoate were 0.16, 5.0, 0.1, and 2.0 ng/mL, respectively, when 2 mL of plasma were used. The recoveries of most of the steroids were 71.6-101.0% except for the decanoate, which could be recovered to about 39.8%. The responses were linear, with correlation coefficients varying from 0.9897 to 0.9999 in the concentration range of 0.1 to 50.0 ng/mL for the steroids studied. When applied to equine (mare) plasma samples, the present method allowed detection of 19-nortestosterone up to 23 days after an intra-muscular injection of 400 mg as the decanoate.

Determination of testosterone : epitestosterone ratio after pentafluorophenyldimethylsilyl-trimethylsilyl derivatisation using gas chromatography-mass spectrometry in equine urine

A highly specific method is described for measuring the testosterone:epitestosterone ratio in equine urine by gas chromatography-mass spectrometry (GC-MS) with stable isotope internal standards. The procedure was based on Serdolit Pad-1 resin extraction, enzymatic hydrolysis, and chemical derivatisation prior to instrumental analysis. The mixed derivatives, 3-trimethylsilyl-17-pentafluorophenyldimethylsilyl ether (3-TMS-17-flophemesyl) testosterone and epitestosterone, were found to have excellent analytical properties. The specificity of the derivatisation method exploits a unique feature of steroids: the selective exchange of the alcoholic flophemesyl ether for the trimethylsilyl ether. The sensitivity and specificity of the mixed 3-TMS-17-flophemesyl derivatives allow adequate determinations of testosterone and epitestosterone, even in urine from mares, in 5 ml samples. The repeatability of testosterone and epitestosterone was 6.2 and 5.7%, respectively, and their reproducibility was in the range of 6.4-8.7%.

Comparison of GC/MS and LC/MS methods for the analysis of propofol and its metabolites in urine.

Gas chromatography-mass spectrometry (GC/MS) and liquid chromatography-mass spectrometry (LC/MS) were compared for their capacity to metabolite identification, sensitivity, and speed of analysis for propofol and its metabolites in urine samples. Acidic hydrolysis, liquid-liquid extraction (LLE), and trimethylsilyl (TMS) derivatization procedures were applied for GC/MS analysis. The LC/MS analysis used a simple sample pretreatment based on centrifugation and dilution. Propofol and four metabolites were successfully analyzed by GC/MS following TMS derivatization. One compound, di-isopropanolphenol was tentatively characterized as a new metabolite observed for the first time in human urine. The TMS derivatization greatly improved the chromatographic properties and detection sensitivity, especially for hydroxylated metabolites. The lower limits of quantitation (LLOQ) of propofol were about 325 and 0.51 ng/mL for the GC/MS scan mode and selected ion monitoring (SIM) mode, respectively. In addition, five conjugated propofol metabolites were successfully analyzed by LC-MS/MS in negative ion mode. The detection sensitivity for these conjugated metabolites could be greatly enhanced by the addition of triethylamine to the mobile phase without any loss of LC resolution capacity. The LLOQs of propofol-glucuronide (PG) were about 1.17 and 2.01 ng/mL for the LC-MS-selected ion monitoring (SIM) and multiple reaction monitoring (MRM) mode, respectively. Both GC/MS and LC/MS methods sensitively detected nine metabolites of propofol and could be used to provide complementary data for the reasonable propofol metabolism study. Urinary excretion profiles for propofol and its metabolites following administration to human were suggested based on the total ion chromatograms obtained by GC/MS and LC/MS methods, respectively.

Simultaneous determination of cannabidiol, cannabinol, and \gD9-tetrahydrocannabinol in human hair by gas chromatography-mass spectrometryin human hair by gas chromatography-mass spectrometry

An analytical method was developed for evaluating the cannabidiol (CBD), cannabinol, (CBN), and gD9-tetrahydrocannabinol (gD9-THC) level in human hair using gas chromatography-mass spectrometry (GC-MS). hair samples (50 mg) were washed with isopropyl alcohol and cut into small fragments (<1 mm). After adding a deuterated internal standard, the hair, samples were incubated in 1.0 M NaOH for 10 min at 95°C. The analytes from the resulting hydrolyzed samples were extracted using a mixture ofn-hexane-ethyl acetate (75:25,v/v). The extracts were then evaporated, derivatized, and injected into the GC-MS. The recovery ranges of CBD, CBN and gD9-THC at three concentration levels were 37.9–94.5% with good correlation coefficients (r2>0.9989). The intra-day precision and accuracy ranged from −9.4% to 17.7%, and the inter-day precision and accuracy ranged from −15.5% to 14.5%, respectively. The limits of detection (LOD) for CBD, CBN, and gD9-THC were 0.005, 0.002, and 0.006 ng/mg, respectively. The applicability of this method of analyzing the hair samples from cannabis abusers was demonstrated.

Detection of Anabolic Steroids By Gc/Sim/Ms With Trifluoroacetylation in Equine Plasma and Urine

ABSTRACT A method to detect three anabolic steroids (boldenone, nandrolone and mesterolone) is presented. The anabolic steroids are isolated from equine plasma and urine by extraction with diethyl ether and C18 Sep-Pak cartridge adsorption, respectively. The extracts obtained were derivatized with trifluoroacetyl anhydride and analyzed by GC/SIM/MS. The selected ion monitoring (SIM) mode was applied to increase the sensitivity and, when possible, the higher m/z ions were selected to improve identification. Stability of derivatives was good and compounds having hydroxy and conjugated ketone groups produced trifluoroacetyl ester derivatives that were also stable. Repeatability of the chromatographic analysis was evaluated on the basis of area repeatability, and the coefficient of variation obtained was lower than 4.4. The detection limit was 1 and 5 ng/ml for all the anabolic steroids studied in equine plasma and urine, respectively.