The behavior of some pesticide residues in stored medicinal plants samples

It is well known that there are many contaminants and residues that may cause harm to the consumers of herbal medicines. It is, therefore, essential to establish a convenient quality control method to assure the safety of herbal products (1). Knowing the behavior of residues in dried plants is a benefit for the direct consumer, for the processor, and for the analyst who must know the stability of samples during analytical methods validation and rutine sample testing. The purpose of testing was to evaluate the stability of 41 pesticides included in dried medicinal plants, at four time periods: one week, one month, 2 years and 4 years. The behaviour of residues was assessed by repeated analysis by comparing an initial fortified sample, properly stored, with a freshly prepared fortified sample. The quantitative analysis of samples was performed by QuEChERS methodology by a validated GC-MS method (2). Of each variant six repetitions were analyzed at each time. Statistical analysis was based on the comparison of the two averages obtained on each analysis time, by checking the significance of differences, calculating test statistic and comparing with the critical value (confidence level 95%, N1+N2 – 2 degrees of freedom).The rate of pesticide movement has been evaluated for three calculated percent of remaining thresholds: below 20%: for some organophosphorous and organochlorine pesticides, between 20 – 80% interval: for some organophosphorous, organochlorine and acetamide pesticides and more than 80%: for some organochlorine and pyrethroid pesticides.

[1] Pérez-Parada A, Colazzo1 M, Besil N, Dellacassa E, Cesio V, Heinzen H. and Fernández-Alba R, Pesticides in the Modern World – Pesticide Residues in Natural Products with Pharmaceutical Use: Occurrence, Analytical Advances and Perspectives, Intech Open Sciences 2011: 357 – 390

[2] Łozowicka B, Jankowska M, Rutkowska E, Hrynko I, Kaczyński P, and Miciński J.: Journal of Natural Medicine 2014; 95 – 111.