No abstract

Ethanol is the most frequently identified compound in forensic toxicology. Although confirmation involving mass spectrometry is desirable, relatively few methods have been published to date. A novel technique utilizing a Dean's Switch to simultaneously quantitate and confirm ethyl alcohol by flame-ionization (FID) and mass spectrometric (MS) detection after headspace sampling and gas chromatographic separation is presented. Using 100 μL of sample, the limits of detection and quantitation were 0.005 and 0.010 g/dL, respectively. The zero-order linear range (r(2) > 0.990) was determined to span the concentrations of 0.010 to 1.000 g/dL. The coefficient of variation of replicate analyses was less than 3.1%. Quantitative accuracy was within ±8%, ±6%, ±3%, and ±1.5% at concentrations of 0.010, 0.025, 0.080, and 0.300 g/dL, respectively. In addition, 1,1-difluoroethane was validated for qualitative identification by this method. The validated FID-MS method provides a procedure for the quantitation of ethyl alcohol in blood by FID with simultaneous confirmation by MS and can also be utilized as an identification method for inhalants such as 1,1-difluoroethane.

In recent years, the use of gamma-hydroxybutyrate (GHB), as a recreational drug has prompted forensic toxicology laboratories to incorporate the analysis for GHB into their routine screening procedures. GHB, being a natural occurring constituent of the human body, presents a challenge for forensic toxicologists in that endogenous levels and exogenous levels of GHB need to be differentiated in case samples. This study was designed to determine typical urinary endogenous levels of GHB in humans based on the analysis of urine samples voluntarily provided by 55 male and female subjects ranging in age from 6 to 59 years. All samples were initially screened for the presence of GHB utilizing a hydrolysis method designed to quantitatively convert the GHB in urine samples to gamma-butyrolactone (GBL) followed by the liquid-liquid extraction and analysis of any GBL present by gas chromatography-mass spectrometry (GC-MS). As a confirmation test, samples were then extracted by a solid-phase extraction technique, derivatized to GHB di-TMS, and analyzed by GC-MS. The median concentration determined for the 55 subjects was 1.3 mg/mL (mean = 1.65 microg/mL, range 0.9 microg/mL to 3.5 microg/mL, standard deviation 0.68 microg/mL). The results of this study confirm the previously suggested cutoff of 10 microg/mL for routine forensic analyses.

The effect of long-term room temperature storage on the stability of ethanol in whole blood specimens was investigated. One hundred and seventeen preserved whole blood case samples (110 of 117 with two tubes of blood in each case) were used for this study. One tube from each case was initially tested for blood alcohol concentration (BAC) for criminal driving under the influence proceedings. Cases positive for ethanol ranged in BAC from 0.023 to 0.281 g/dL. The second tube, if present, remained sealed. All blood samples were then stored at room temperature. After 5.4-10.3 years, the opened tubes were reanalyzed for BAC by the same laboratory that performed the initial testing using the same method and same instrumentation. After the same storage period, the unopened tubes were sent to a different laboratory, using a different method and different instrumentation, and reanalyzed for BAC after a total of 5.6-10.5 years of room temperature storage. Seven samples initially negative for alcohol remained negative. All samples initially positive for ethanol demonstrated a decrease in BAC over time with a statistically significant difference in loss observed based on blood sample volume and whether or not the tube had been previously opened. The decrease in BAC ranged from 0.005 to 0.234 g/dL. Tubes that were not previously opened and were more than half full demonstrated better BAC stability with 89% of these tubes demonstrating a loss of BAC between 0.01 and 0.05 g/dL.

Due to the high prevalence of cannabinoids in forensic toxicology casework, it is desirable to have an efficient method that uses a small volume of blood and requires a minimal sample preparation. Although many methods have been reported, they are often labor intensive, require special sample preparation materials, use 1 mL or more of specimen or are difficult to replicate. The liquid chromatography with tandem mass spectrometry (LC-MS-MS) method presented herein employs a rapid and simple liquid-liquid extraction, has been successfully applied in two different laboratories, uses 0.5 mL of specimen and was extensively validated. The validated limit of detection and limit of quantitation were 1 ng/mL for delta-9-tetrahydrocannabinol (THC) and 11-hydroxy-delta-9-tetrahydrocannabinol (OH-THC) and 5 ng/mL for 11-nor-9-carboxy-delta-9-tetrahydrocannabinol (THCA). Each analyte demonstrated a zero-order linear range (r > 0.990) with 1/x weighting of 1-40 ng/mL for THC and OH-THC and 5-200 ng/mL for THCA. The coefficient of variation of replicate analyses was within 14%. Bias was within ±13% of the prepared concentration. The validated method provides a sensitive, efficient and robust procedure for the quantitation of cannabinoids in blood using LC-MS-MS and a sample volume of 0.5 mL.