The purpose of this study was to develop a method to analyse the concentration of multiple illegal narcotics present in dietary supplements. To this end, we established and optimised a procedure using LC-MS/MS simultaneously to analyse 28 narcotic compounds in various forms of dietary supplements, including powders, tablets, liquids and capsules. In addition, candy and cookies that have also had detected cases of adulteration were also analysed. The specificity, linearity, accuracy, precision, limit of detection (LOD), limit of quantitation (LOQ), stability and recovery for these methods were validated accordingly. The LOD and LOQ of the LC-MS/MS ranged from 0.01-50.0 to 0.03-100 ng g(-1), respectively. The linearity of these results was good (r(2) > 0.99), with intra- and inter-day precision values of 0.2-5.2% and 0.2-4.8%, respectively. Further, the intra- and inter-day accuracies of this method were 97.0-103.4% and 94.6-103.1%, respectively. The stability RSD was less than 7.8%. The mean recovery for this LC-MS/MS procedure was 81.1-117.4%, with an RSD less than 9.8%. Following the validation of our method, we analysed 47 commercially available dietary supplements obtained in Korea. Whilst none of these samples had detectable amounts of the 28 specified narcotic adulterants, our novel LC-MS/MS procedure can be utilised comprehensively and continually to monitor illegal drug adulteration in various forms of dietary supplements.
Keywords: LC-MS/MS; adulterants; dietary supplements; method validation; narcotics.