Analysis for GHB, GBL and 1,4BD

Biological specimen extraction can be accomplished by liquid-liquid, solid-phase or solid-phase microextraction with subsequent detection of GHB or GBL by gas chromatography-mass spectrometry (GC-MS) using electron ionization (El), positive or negative chemical ionization (CI) or gas chromatography with flame ionization detection (GC-FID). LeBeau et al. (1999) describes a method that employs two ahquots of specimen. The first is converted to GBL with concentrated sulfuric acid while the second is extracted without conversion. A simple liquid-liquid methylene chloride extraction was utilized, and the ahquots were then screened by GC-FID without derivatization. Specimens that screened positive by this method were then re-aliquoted and subjected to the same extraction with the addition of the deuterated analog of GBL. The extract was then analyzed by headspace GC-MS in the full-scan mode. Quantitation was performed by comparison of the area of the 

This method displayed linearity in both blood and urine from 5 to 1000pgmL recoveries that ranged between 75 and 87%. 

A liquid-liquid extraction method employed by the toxicology laboratory in the Department of the Coroner of Los Angeles County Califomia (Anderson and Kuwahara, 1997) first converts GHB to the lactone followed by chloroform extraction. Both blood and urine were analyzed using this method with y-valerolactone as the internal standard. Detection was by GC-MS using the selected-ion monitoring (SIM) mode. The ions monitored were GBL m/z 42, 56 and 86 with miz 41, 56 and 85 for the internal standard. The method was linear from 5 to 300 pg mL with a lower limit of detection of 5 pg mL. However, owing to the introduction of commercial products containing GVL, a different internal standard is recommended. 

There are three different solid-phase extraction (SPE) methods that differ with respect to the column used, pre-extraction sample treatment, post-extraction sample treatment and internal standard. All three SPE methods extract GHB from urine and blood, derivatize with BSTEA with 1% TMCS, and detect analytes by GC-MS in the El mode with either SIM or the full-scan mode. The ions monitored for the GHB di-TMS derivative are miz 233, 234 and 235 with care being taken to avoid the ions that are common between di-TMS GHB and di-TMS urea, at m/z 147, 148 and 149. Urea is a naturally occurring compound in urine and care must be taken that its derivative does not interfere. 

The SPE method used by the Miami-Dade County Medical Examiner s Office, Toxicology Laboratory, in Miami, Florida (Andollo and Hearn, 1998) uses Chem-Elute - SPE columns, p-hydroxybutyric acid internal standard, pretreatment of urine with sulfuric acid and pretreatment of blood with sodium tungstate and sulfuric acid. The Dade County method gave an absolute recovery of 30% with a limit of detection of 2 pg mL and a limit of quantitation of 10 pgmL  

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