Determination of Cyanide in Nuts and Plum Food by Headspace Gas Chromatography-Mass Spectrometry with Pre-Column Derivatization

A method for determination of cyanide (calculated in CN^-, the same below) in nuts and plum food by headspace gas chromatography-mass spectrometry with pre-column derivatization was proposed. The sample (2.000 0 g) was taken and mixed well with about 60 mL of 1.0 g·L^-1 sodium hydroxide solution. The solution was extracted by ultrasonic for 20 min. After cooling to room temperature, the extract was made its volume up to 100 mL with 1.0 g·L^-1 sodium hydroxide solution and filtered. 5 mL of the subsequent filtrate was put into the headspace bottle, and 200 μL of 17% (volume fraction) phosphoric acid solution was added. After mixing, 200 μL of 10 g·L^-1 chloramine T solution was added and the solution was derivatized at 55 ℃ for 30 min. Cyanide in the obtained solution was determined by gas chromatography-mass spectrometry, with DB-624 UI capillary column as the stationary phase. As shown by the results, linear relationship between mass concentration of CN^- and the corresponding peak area of cyanide derivative was found within 200 μg·L^-1, with detection limit (3S/N) of 0.01 mg·kg^-1. Test for recovery was made by the standard addition method, giving results in the range of 96.8%-103%, with RSDs (n=6) of the determined values less than 4.0%. This method was compared with the spectrophotometry according to the national standard method GB 5009.36-2016, and the determined results obtained by the two methods were basically consistent without significant difference. This method was used for analysis of the actual samples, and it was shown that cyanide was detected in all nuts and plum food, and it was recommended that cyanide should be added to the list of contaminant limits in the food of GB 2762-2022 for strict control.