Simultaneous determination of alpha-, beta- and gamma-hydroxybutyric acids in micro-pulverized human hair by GC-MS: Method development, validation and application

Measurement of 7-dehydrocholesterol and cholesterol in hair can be used in the diagnosis of Smith-Lemli-Opitz syndrome

7-dehydrocholesterol (7-DHC) and cholesterol (CHOL) are biomarkers of Smith-Lemli-Opitz Syndrome (SLOS), a congenital autosomal recessive disorder characterized by elevated 7-DHC level in patients. Hair samples have been shown to have great diagnostic and research value, which has long been neglected in the SLOS field. In this study, we sought to investigate the feasibility of using hair for SLOS diagnosis. In the presence of antioxidants (2,6-ditert-butyl-4-methylphenol and triphenylphosphine), hair samples were completely pulverized and extracted by micro-pulverized extraction in alkaline solution or in n-hexane. After microwave-assisted derivatization with N,O-Bis(trimethylsilyl)trifluoroacetamide, the analytes were measured by GC-MS. We found that the limits of determination for 7-DHC and CHOL were 10 ng/mg and 8 ng/mg, respectively. In addition, good linearity was obtained in the range of 50-4000 ng/mg and 30-6000 ng/mg for 7-DHC and CHOL, respectively, which fully meets the requirement for SLOS diagnosis and related research. Finally, by applying the proposed method to real hair samples collected from 14 healthy infants and two suspected SLOS patients, we confirmed the feasibility of hair analysis as a diagnostic tool for SLOS. In conclusion, we present an optimized and validated analytical method for the simultaneous determination of two SLOS biomarkers using human hair.

A proper and systematic qualitative method validation procedure and its application to gas chromatography-mass spectrometry analysis of Chemical Weapons Convention related chemicals

Performing a detailed qualitative validation, which is carried out by many laboratories in the forensic community, has been the main goal of this study. In this study, a proper and systematic qualitative method validation procedure was proposed, and its application was shown on the analysis of Chemical Weapon Convention (CWC) related compounds in organic samples. All validation steps were described in detail. The study was carried out in pump oil and dichloromethane (DCM). The limit of detection values were determined for each compound and were found in the range of 0.5-2.0 µg mL^-1 in pump oil and 0.08-1.5 µg mL^-1 in DCM. The validation parameters were calculated, such as the rates of sensitivity, selectivity, false-negative, false-positive, also accordance and concordance. The predicted and obtained results were compared by using Cohen's Kappa Coefficient Test, and the compatibility of the results was found as "very good". After the validation procedure, all of the validation results were evaluated, and the proposed method was confirmed as appropriate for the analysis of CWC-related compounds in organic samples. The applicability of the validated method was proved by determining the CWC-related compounds in organic samples provided by the Organization for the Prohibition of Chemical Weapons during proficiency tests.

Zwitterionic HILIC stationary phase as a valuable alternative in separative techniques: Application to the analysis of gamma-hydroxybutyric acid and its metabolite in hair

In this work, the physical and chemical properties of a novel zwitterionic LC stationary phase are applied to the development, validation and application of a new fast and reliable method devoted to the analysis of GHB (gamma-hydroxybutyric acid) and its relatively new discovered glucuronide metabolite in hair. The obtained sensitivity, expressed as limit of detection (LOD) and quantification (LOQ), were 0.033 and 0.10 ng/mg for GHB and 0.11 and 0.37 ng/mg, for GHB-glucuronide respectively. Linearity was assessed between LOQ and 50 ng/mg for both compounds. GHB and GHB-glucuronide extraction from hair matrix was maintained simple and consisted in an acidified-solvent incubation. No samples purification was required before LC-MS/MS analysis. The method was finally applied to 65 real hair sample, 60 adults and 5 children below 2 years old. The obtained results highlighted that GHB concentrations were in the range 0.11-0.96 ng/mg (average 0.38 ± 0.25 ng/mg) in 44 cases (68%) while in 21 samples GHB concentrations were in the range between LOD and LOQ (0.033-0.1 ng/mg). GHB-glucuronide was detected in few samples (n. 3) at levels below LOQ. The interest on these molecules relies on the fact that GHB is both a naturally occurring inhibitory neurotransmitter in the central nervous system and an illicit drug often experienced by victims of drug-facilitated sexual assault. GHB-glucuronide was firstly identified in urine by the group of Petersen in 2013 and, as per analogy to ethyl glucuronide, it was proposed as a longer biomarker for GHB intoxication.