Qualitative and quantitative analysis of a group of volatile organic compounds in biological samples by HS-GC/FID: application in practical cases

• A procedure for HS-GC/FID was developed for the analysis of 11 VOCs.
• The method was validated in whole blood, urine and vitreous humor.
• The method proved to be selective and sensitive for small sample volumes (100 μL).
• It is not necessary to apply any extraction procedure (HS injection technique).
• The method developed has been applied to forensic cases.

A simple and sensitive procedure, using n-propanol as internal standard (IS), was developed and validated for the qualitative and quantitative analysis of a group of 11 volatile organic substances with different physicochemical properties (1-butanol, 2-propanol, acetaldehyde, ethyl acetate, acetone, acetonitrile, chloroform, diethyl ether, methanol, toluene and p-xylene) in whole blood, urine and vitreous humor. Samples were prepared by dilution with an aqueous solution of internal standard followed by Headspace Gas Chromatography with a Flame-ionization Detector (HS GC-FID) analysis. Chromatographic separation was performed using two capillary columns with different polarities (DB-ALC2: 30 m × 0.320 mm × 1.2 μm and DB-ALC1: 30 m × 0.320 mm × 1.8 μm), thus providing a change in the retention and elution order of volatiles. This dual column confirmation increases the specificity, since the risk of another substance co-eluting at the same time in both columns is very small. The method was linear from 5 to 1000 mg/L for toluene and p-xylene, 50–1000 mg/L for chloroform, and 50–2000 mg/L for the remaining substances, with correlation coefficients of over 0.99 for all compounds. The limits of detection (LOD) ranged 1 to 10 mg/L, while the limits of quantification (LOQ) ranged from 2 to 31 mg/L. The intra-day precision (CV < 6.4%), intermediate precision (CV < 7.0%) and accuracy (relative error ±10%) of the method were in conformity with the criteria normally accepted in bioanalytical method validation. The method developed has been applied to forensic cases, with the advantages that it uses a small sample volume and does not require any extraction procedure as it makes use of a headspace injection technique.