Objective To establish an analytical method of LC-MS/MS based on micro-segmentation analysis of multiple hairs,verify the detection of 20 benzodiazepines in 1mm hair,and finally use it for case detection analysis.Methods 5 hairs were cut into 1mm long segments each,and the corresponding segments were immersed and sonicated in an extract containing dithiothreitol,methanol,etc.Mobile phase A was 0.1%formic acid in water,and mobile phase B was acetonitrile.Data were collected using electrospray ion source positive ion mode in multiple reaction monitoring mode.Results The 20 benzodiazepines in multiple hairs had a good linear relationship(r>0.99),detection limit of 0.2～5 pg/mm,minimum quantification limit of 0.5 to 20 pg/mm,the intro-day and inter-day precisions of 2.03%to 13.81%,the intro-day and inter-day accuracies of 87.98%～111.29%,matrix effect of 71.15%～110.43%,and extraction recovery of 69.34%to 99.94%.Using this method,hair samples were analyzed in volunteers taking a single dose of clonazepam for 20 days,and the detected location of clonazepam in 15 hairs was located in segment 6～11 from the hair root,with the concentration range of 1.06～3.45 pg/mm.By this method,the hair of the victims suspected of having taken sleeping pills in the case was analyzed.In 15 hairs,clonazepam was detected in segments 9～13 of the hair root.The quantitative results were 1.07～19.06 pg/mm.The experimental results were basically consistent with the medication time of the victim.Conclusion The micro-segmentation analysis technique of multiple hairs can be applied to the investigation of drug-assisted crime cases,and can roughly estimate the medication time.

Objective To establish an analytical method of LC-MS/MS based on micro-segmentation analysis of multiple hairs,verify the detection of 20 benzodiazepines in 1mm hair,and finally use it for case detection analysis.Methods 5 hairs were cut into 1mm long segments each,and the corresponding segments were immersed and sonicated in an extract containing dithiothreitol,methanol,etc.Mobile phase A was 0.1%formic acid in water,and mobile phase B was acetonitrile.Data were collected using electrospray ion source positive ion mode in multiple reaction monitoring mode.Results The 20 benzodiazepines in multiple hairs had a good linear relationship(r>0.99),detection limit of 0.2～5 pg/mm,minimum quantification limit of 0.5 to 20 pg/mm,the intro-day and inter-day precisions of 2.03%to 13.81%,the intro-day and inter-day accuracies of 87.98%～111.29%,matrix effect of 71.15%～110.43%,and extraction recovery of 69.34%to 99.94%.Using this method,hair samples were analyzed in volunteers taking a single dose of clonazepam for 20 days,and the detected location of clonazepam in 15 hairs was located in segment 6～11 from the hair root,with the concentration range of 1.06～3.45 pg/mm.By this method,the hair of the victims suspected of having taken sleeping pills in the case was analyzed.In 15 hairs,clonazepam was detected in segments 9～13 of the hair root.The quantitative results were 1.07～19.06 pg/mm.The experimental results were basically consistent with the medication time of the victim.Conclusion The micro-segmentation analysis technique of multiple hairs can be applied to the investigation of drug-assisted crime cases,and can roughly estimate the medication time.