Determination of Cyanide in Biological and Non-biological Matrices by Headspace Gas Chromatography coupled to Flame- Ionization Detector

Abstract

A simple, rapid and reliable method for quantitation of cyanide was developed on a headspace gas chromatograph coupled to a flame ionization detector using a HP-Innovax (Polyethylene glycol bonded) column on an Agilent 7890A GC. Cyanide in blood or other matrices was liberated by conversion of potassium cyanide to the volatile hydrogen cyanide (HCN) through addition of 5N sulfuric acid in a headspace vial and analyzed using an Agilent G1888 headspace auto-sampler. HCN gas diffuses into the headspace above the specimen in a sealed vial based on Henry’s Law of partial pressure. This method showed good linearity (r2= 0.9996) in the range of 8.0-60.0 μg/mL with 1.0 μg/mL of HCN as the limit of detection. The accuracy of the method at three different concentrations (8.0, 16.0, 50.0 μg/ mL of HCN) was in the range of 95.0% to 101.9% and inter-day precision (%CV) ranged from 1.3% to 3.8%. Identical calibration curves with a coefficient of correlation above 0.990 were obtained when blood, gastric contents, liver tissue homogenate, urine and water were used as calibration standard matrices. Therefore, a single calibration curve is sufficient for diverse matrices and preparation of matrix-matched standards is not required. The method showed successful quantitation of Hydrogen cyanide in gastric contents, which is one of the most variable matrices in forensic toxicology. The method is well adopted for postmortem specimens because of its wide linear range, adaptability to various matrices, ease and rapidity of use.

Keywords

• cyanide
• headspace
• flame ionization detection