GHB analysis

It should be noted that hemoglobinopathies may interfere with glycated hemoglobin (GHb) analysis, as results may be falsely increased or decreased, depending on the particular method and the hemoglobinopathy. Hemoglobin variants that cannot be separated from Hb A or Hb A,c will produce spuriously increased or decreased results by ion-exchange HPLC. 

Prison et al. (1998) describes a method using sohd-phase microextraction of GHB in plasma and urine. This is a new approach for GHB analysis that shows promise in that it is simple, sensitive and requires only 0.5 mL of specimen. The linearity range was from 1 to 100 pg mL in plasma and from 5 to 150 pg mL in urine with a Emit of detection of 0.05 and 0.1 pg mL for plasma and urine, respectively. The limit of detection was calculated based on aqueous solutions because the blank plasma and urine specimens had endogenous GHB concentrations of 0.1-0.2 and 0.5-L5pgmL, respectively. The method required conversion of GHB to GBL with GBL-de as the internal standard and detection by headspace GC-MS with spectra from both CI and El ionization modes. Many methods are available for GHB and GBL analyses depending on the equipment and resources available to the laboratory. 

In recent years, the abuse of y-hydroxybutyrate (GHB) has risen dramatically (LeBeau et al., 2000). This metabolite of GABA can be difficult to analyze because of its short half-life and endogenous presence. However, a simple and fast head space analysis using GC-FID with MS confirmation has been published (LeBeau et al., 2000). 

Le Beau MA, Montgomery MA, Miller ML, Burmeister SG. 2000. Analysis of biofluids for gamma-hydroxybutyrate (GHB) and gamma-butyrolactone (GBL) by headspace GC-FID and GC-MS. J Anal Toxicol 24 421. 

Although the method detects all GHbs, seyeral commercially available systems are calibrated to also report an Hb Ale standardized value. The latter are derived from an equation obtained from correlation between total GHb and Hb Ale analysis by HPLC. " A linear relationship has been demonstrated, and standardized Hb Aie values are thus comparable with the values obtained by methods specific for Hb Ale. Columns and reagents are readily available from a number of manufacturers, several of whom have automated the procedure. 

McCusker RR, Paget-Wilkes H, Chronister CW, Goldberger BA, ElSohly MA. Analysis of gamma-, hydroxybutyrate (GHB) in urine by gas chromatography-mass spectrometry. J Anal Toxicol 1999 23 ... 

The United Chemical Technologies GHB SPE column method has been modified to include GHB and 1,4BD analysis in blood, eye fluid and tissue homogenate samples. The sample size is only 200 pL and requires a sample preparation step of extraction with... 

However, the same is not true for 1,4BD analysis. Concern over detecting and quantifying 1,4BD is just becoming an issue in the forensic community. As discussed previously, the pharmacologically active form of 1,4BD is GHB. However, determination of the concentration of 1,4BD may be useful in documenting acute intoxication. McCutcheon et al. (2000) utilized a simple one-step extraction at physiological pH into... 

Quantitation of 1,4BD by high-performance liquid chromatography (HPLC) with photo-diode-array detection was described by Duer et al. (2001). The 1,4BD was extracted from the biological matrix with acetonitrile and derivatized with 3.5-dinitrobenzoyl chloride. This method has a linear range from 3 to 250 rng L with a limit of quantitation of 10 rng L . Also, as was mentioned previously, the United Chemical Technologies GHB SPE column method has been modified to include 1,4BD analysis (Kraner et al., 2000). 

Let us consider the analysis of gamma hydroxbutyrate (GHB see Figure 6.8), which has a pKa of 4.72 (see Figure 6.9). In order to maintain the analyte in a non-ionised state, the system would need to be operated below pH 2, which is outside the range for conventional silica-based columns. With a low carbon load column, operating at this pH level would not be possible however, the high carbon loading on some columns allows for pH operation at values as low as pH 1. Several manufacturers offer columns of this nature that can be accessed via their Web sites. 

Saudan, C., Augsburger, M., Mangin, E, Saugy, M. (2007) Carbon isotope ratio analysis by gas chromatography/ combustion/isotope ratio mass spectrometry for the detection of gamma-hydroxybutyric acid (GHB) administration to humans. Rapid Commun. Mass Spectrom.,21, 3956-3962. 

Goulle JP, Cheze M, Pepin G. Determination of endogenous levels of GHB in human hair. Are there possibilities for the identification of GHB administration through hair analysis in cases of drug-facilitated sexual assault J Anal Toxicol 2003 27 574—80. 

Biological Applications Analysis of microorganisms detecting anti-bacterial agent, y-hydroxybutyric acid (GHB) treating cancer, pain °... 

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