Determination of Cyanide in Water and Urine by Solid Phase Extraction-Solid Phase Assisted Derivatization-Gas Chromatography-Tandem Mass Spectrometry

A solid phase extraction-solid phase assisted derivatization (SPE-SPAD) method combined with gas chromatography-tandem mass spectrometry analysis was established for qualitative and quantitative detection of trace cyanide in environmental samples and biological samples. The cyanide ion was transformed to cyanogen chloride via chloramine T. Next, the process of enrichment, purification and derivatization for reactants were simultaneously archived on the C8 solid phase extraction (SPE) column. The types of SPE column and the solvent of reaction were optimized for the derivatization. The structure of derivative was identified as n-butyl thiocyanate by gas chromatography-mass spectrometry and nuclear magnetic resonance. The qualitative and quantitative detection method for cyanide in water and urine samples was established by gas chromatography-selective reaction monitoring (SRM) mode via isopropyl disulfide as internal standard. The established method had high sensitivity, good specificity and shorter time of sample preparation. The linear ranges for detection of cyanide in water and urine samples were 10 - 1000 ng/mL and 10 - 800 ng/mL, with detection limits of 7.0 and 8.0 ng/mL (S/N=3), respectively. The intra- and inter-day precisions were 4.2%-7.8% (n=3) and 5.2%-7.9% (n=6), respectively. The method was successfully applied to determine the cyanide in urine samples from the 2nd Biological Proficiency Test, which was organized by the Organization for the Prohibition of Chemical Weapons (OPCW), and the average recovery was 97.7%. The wastewater from the Tianjin port after the explosion was detected and the concentration of cyanide was about 1.9 mg/mL. The established method was effective for screening and identification of trace cyanide, and had great potential in chemical accident rescue and chemical weapons verification.

Automated summary

A SPE-SPAD method combined with GC-tandem MS analysis was established for qualitative and quantitative detection of trace cyanide in environmental and biological samples. The method involved the transformation of cyanide ion to cyanogen chloride, and the enrichment, purification, and derivatization of reagents on a C8 SPE column. The structure of the derivative was identified as n-butyl thiocyanate. The established method showed high sensitivity, good specificity, and shorter sample preparation time.