Determination of 7 Minor Elements in Hot Melt Adhesives by ICP-MS after Digestion Assisted with Ammonium Fluoride

A method was established for the determination of 7 minor elements (Cr, Ni, As, Se, Cd, Hg and Pb) in hot melt adhesives by inductively coupled plasma mass spectrometry (ICP-MS) after digestion assisted with ammonium fluoride. 0.300 0 g of samples of hot melt adhesive were digested by microwave with a selected acid mixture of 6 mL of 60% (volume fraction) HNO₃ solution and 0.50 mL of 12.66 mol·L^-1 NH₄F solution at 185℃ for 20 min. The digested solution was removed to a flat temperature control heater and heated for acid removal at 120℃ for 3 h. After cooling, the solution was diluted with water and its volume was made up to 50 mL, which was analyzed under the optimized ICP-MS conditions. Internal standard element of ¹¹⁵In was used for qualification. The results showed that linearity relationships between values of mass concentration of the 7 elements and ratios of signal intensity of these 7 elements to interral standard element of indium were kept in the definite ranges, with detection limits (3s) ranging from 0.005 mg·kg^-1 to 0.029 mg·kg^-1. Recovery test was made by standard addition method, giving results of recovery in the range from 86.3% to 106%, and RSDs (n=5) of the determined values ranged from 1.8% to 11%. Five actual samples were analyzed by the proposed method, Cr, Ni were found in all the 5 samples, and Pb was found in the 3 samples, with the contents of the 3 elements below the limit specified by YC/T 187-2004. The proposed method was compared with YC/T 316-2014 by t-test, t values of Cr and Ni were less than t_0.05,4, t value of Pb was less than t_0.05,2, and p values of the 3 elements were all above 0.05 under the 95% confidence level. There was no significant difference between the two methods.