A Validated Method for the Determination of Neonicotinoid, Pyrethroid and Organochlorine Residues in Human Milk

Exposure to pesticides in the environment is sensitively indicated by the concentration of these chemicals in human milk. However, to the best of our knowledge, detection methods in human milk for the relatively new class of pesticides, neonicotinoids, are yet to be validated. We developed a method of detection of neonicotinoids in human milk, together with two other classes of pesticides, pyrethroids and organochlorines. Neonicotinoids and pyrethroids are emerging pesticides that are replacing older and more persistent chemicals such as organochlorines. We optimized a procedure for extraction of these chemicals from whole milk and report our solutions to the problems of interference by co-extracted substances. The clean-up method was optimized using a minimum amount of PSA (50 mg) and MgSO4 (150 mg). This was followed by GC-MS/MS analysis (for organochlorines and pyrethroids) and LC-MS/MS (for neonicotinoids). The method was validated following SANTE/11945/2015 guidelines at concentrations 10, 20 and 100 ng g(-1). Limits of quantification were obtained at <= 2 ng g(-1) for all pesticides and lowest validated level were 10 ng g(-1), with measurement uncertainty between 0.47 and 2.6 ng g(-1). Average recovery ranged from 84 to 102% and for most compounds was found to be more satisfactory than the original QuEChERS, AOAC 2007.01 acetate buffer method and modified QuEChERS methods. The relative standard deviation was less than 16%. The method was successfully utilized for the analysis of human milk samples from Nadia, West Bengal and was found positive for organochlorines and negative for neonicotinoids and pyrethroids.