The serum and urine from 44 consecutive patients that tested positive for the cocaine metabolite benzoylecgonine (BE) were examined for free cocaine, ecgonine methyl ester (EME), and other metabolites by gas chromatography/ion trap mass spectrometry (GC/MS). In 13 of these patients, unique ethanol-related cocaine metabolites, cocaethylene and ecognine ethyl ester (EEE), were detected in urine and serum. One was from a newborn baby whose mother's blood was positive for cocaine and negative for cocaethylene. In two other patients, isopropanol was also consumed with cocaine and ethanol. In one of these two, cocaisopropylene and ecognine isopropyl ester (EPE) were identified in urine. The urine ethanol concentration in 7 of the 13 cocaethylene-positive patients ranged from 19 to 322 mg/dL. In the other six, ethanol was not detected in the urine. However, each of these latter patients had either prior serum results that were positive for ethanol or admitted to recent alcohol abuse. In the remaining 31 of 44 cocaine-positive patients, ethanol and the alcohol-specific cocaine metabolites were absent. The detection of alcohol-related cocaine metabolites is fairly common in a cocaine-positive patient population.
Analytical methods developed for the Finnigan MAT ITS40 gas chromatograph-ion trap mass spectrometer (GC/MS) were evaluated for the confirmation of drugs-of-abuse in urine. The specific drugs evaluated are those listed by the National Institute on Drug Abuse (NIDA): 11-nor-9-carboxy-delta 9-tetrahydrocannabinol (9-carboxy-THC), benzoylecgonine (BE), codeine and morphine, phencyclidine (PCP), amphetamine, and methamphetamine. Drugs were extracted from urine using solid-phase columns, separated by capillary gas chromatography, and analyzed by ion trap mass spectrometry following electron impact ionization. All drugs except PCP were derivatized prior to analysis. The full scan limits of detection (LOD), quantitation (LOQ), and linearity were 2.5, 5.0, and 1000 ng/mL, respectively, for 9-carboxy-THC; 37, 75, and 5000 ng/mL for BE; 50, 100, and 2500 ng/mL for the opiates; 0.25, 0.50, and 500 ng/mL for PCP; and 50, 100, and 5000 ng/mL for the amphetamines. The limits of detection (LOD) and limits of quantitation (LOQ) met the minimum criteria for the signal-to-noise (S/N) ratio and spectral match criteria for drug identification. Absolute LODs and LOQs (in ng/mL) for the ITS40 based on single ion monitoring of blank urines were: 0.8 and 2.0 for 9-carboxy-THC; 8.9 and 25 for BE; 3.3 and 9.6 for codeine; 6.2 and 16.7 for morphine; 0.25 and 0.32 for PCP; 0.7 and 2.0 for amphetamine; and 2.4 and 5.7, for methamphetamine, respectively. The coefficient of variation ranged from 5 to 10%, and analytical recoveries were in the range of 90-114%. The ion trap mass spectrometer permits full scan identification of drugs while maintaining analytical LOQ that are below NIDA guidelines, and has equivalent or better detection limits to quadrupole analyzers for high sensitivity applications.
An underivatized methane chemical ionization (CI) assay for measuring amphetamines in urine was evaluated against derivatized electron impact (EI) assays using a gas chromatograph-ion trap mass spectrometer. The full-scan CI mass spectra of methamphetamine, ephedrine/pseudoephedrine, and phentermine were compared with the full scan and three-ion EI mass spectra of heptafluorobutyric anhydride (HFBA) and 4-carbethoxyhexafluorobutyryl chloride (CB) derivatives. The fragmentation patterns for these compounds were nearly identical for the three major high molecular weight ions (m/z 254, 210, and 169 for EI-HFBA derivatives, and m/z 308, 262, and 280 for EI-CB derivatives). The CI mass spectra of the underivatized drugs contained more discernible differences at the higher molecular weights, including m/z 119, 148, and 150 for methamphetamine, 148, 166, and 176 for ephedrine/pseudoephedrine, and 91, 133, and 150 for phentermine. The within-run precision ranged from 7-9% for CI versus 5-6% for EI with HFBA derivatization (mean 500 ng/mL, n = 5). The limits of detection (LOD) for amphetamine and methamphetamine were 2.4 and 8.6 ng/mL, respectively, for CI versus 0.7 and 1.4 ng/mL for EI. The limits of quantitation (LOQ) were 4.5 and 19.1 ng/mL for CI versus 1.4 and 5.7 ng/mL for EI. The use of full-scan mass spectral analysis with either electron impact or chemical ionization provides additional qualitative data that may be helpful for measuring methamphetamine in the presence of other sympathomimetic amines.
We evaluated an automated assay for lactate dehydrogenase (LD; EC 1.1.1.27) isoenzymes, supplied by Boehringer Mannheim Diagnostics (BMD) and based on selective chemical inhibition of non-LD-1 isoenzymes by guanidine thiocyanate. Results were compared with the Roche Isomune LD-1 method. The Hitachi 717 analyzer was used to measure enzyme activity for both procedures in 229 serum samples. One hundred specimens were also analyzed by the Helena rapid electrophoresis (REP) method. We determined the limit of linearity of the BMD method to be about 1200 U of LD-1 per liter. The analytical correlation of BMD (y) with Isomune (x) yielded y = 1.0x + 0.5 U/L, r = 0.997, Sy/x = 16.9 (range 20-1397 U/L). The regression equation for BMD vs REP was y = 1.1x + 7.2% (r = 0.800, Sy/x = 7.4, range 14-83%). Average values for within-run precision for low (38 U/L), medium (180 U/L), and high (865 U/L) controls were 4.1%, 1.0%, and 0.5%, respectively (16 trials of six each). The average values for run-to-run precision were 4.1%, 1.7%, and 1.1%, respectively, for these controls (n = 16). We used receiver-operating characteristic curves to determine optimum decision limits. Using an LD-1 cutoff of 40% of total LD, we obtained a clinical sensitivity of 97-100% and a specificity of 95% when blood was collected during the optimum interval, 24-48 h after the onset of chest pain. We conclude that the BMD LD-1 assay is equivalent to the immunochemical and electrophoretic assays for measuring the LD-1 isoenzyme.
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