A comparative analysis of different hair matrixes and matrix reference materials for quantitative hair analysis in drug tests

The proposal of the concept of Precision Science and the rapid development of technology have raised expectations for a higher demand for accurate quantitative analysis, including hair analysis in drug tests. Many details are presently constraining improvements in precision, so there is a greater need for standardized methods to control and improve the analytical process in the laboratory. Hair matrix reference materials may become a feasible option. In the present study, 34 drug-free hair samples from healthy volunteers were collected and compared with 2 certified standard hair samples. It was observed that the hair matrix of different origins did have a significant impact on hair analysis. Three reference materials were prepared using spiking and two soaking methods, and one natural reference material was collected from real cases. A total of 57 authentic hair samples were measured from March to August 2022 using these 4 reference materials. Differences in the origins of samples were found to have a significant impact on the hair analysis results. The reference material soaked in water and methanol at a 1:1 ratio (v/v) appeared to be an excellent tool for daily quality control, as it gave results closest to those of the natural matrix reference material in all aspects and supported the law principle of the Presumption of Innocence.