Simultaneous determination of cyanide and thiocyanate in milk by GC-MS/MS using cetyltrimethylammonium bromide as both phase transfer catalyst and protein precipitant

A method was developed for simultaneous determination of cyanide and thiocyanate in milk by gas chromatography-tandem quadrupole mass spectrometry (GC-MS/MS). Cyanide and thiocyanate were derivatized with pentafluorobenzyl bromide (PFBBr) as PFB-CN and PFB-SCN, respectively. Cetyltrimethylammonium bromide (CTAB) was employed both as a phase transfer catalyst and a protein precipitant in the sample pretreatment, which facilitates the separation of the organic and aqueous phases, and greatly simplifies the pretreatment procedures to achieve simultaneous and rapid determination of cyanide and thiocyanate. Under the optimized conditions, the limits of detection (LODs) of cyanide and thiocyanate in milk were 0.006 mg/kg and 0.015 mg/kg, and the spiked recoveries ranged from 90.1% to 98.2% and from 91.8% to 98.9% with relative standard deviations (RSDs) less than 18.9% and 15.2%, respectively. The proposed method was validated as a simple, fast and highly sensitive method for the determination of cyanide and thiocyanate in milk.

Automated summary

A method using GC-MS/MS was developed to simultaneously determine cyanide and thiocyanate in milk. Derivatization of cyanide and thiocyanate with PFB-CN and PFB-SCN was achieved with Pentafluorobenzyl bromide (PFBBr). CTAB was used as a phase transfer catalyst and protein precipitant, enabling the separation of organic and aqueous phases and simplifying the pretreatment procedures. The method showed low LODs (0.006 mg/kg and 0.015 mg/kg) and good spiked recoveries (90.1% to 98.2% and 91.8% to 98.9%) with low RSDs (less than 18.9% and 15.2%) for cyanide and thiocyanate in milk, making it a simple, fast, and highly sensitive method.