Variability on ethyl glucuronide concentrations in hair depending on sample pretreatment, using a new developed...

Quantitative determination of ethyl glucuronide in keratin matrix, particularly in hair samples, provides a significant contribution to the evaluation of the extent of ethanol intake. The first-choice method to carry out this analysis is LC-MS/MS, but other techniques may be used. The aim of this work is: a) to develop and validate a GC-MS/MS method for ethyl glucuronide determination in hair; b) to compare GC-MS/MS and LC-MS/MS in analysis of real samples; c) to compare EtG concentration obtained after hair cutting and pulverization. About 30 mg hair samples were washed, pulverized and soaked in 1 ml deionized water. After incubation, the solution was purified through a SPE anion exchange cartridge; the eluate was dried under nitrogen stream, derivatized with PFPA and reconstituted in n-hexane. Then, the sample was injected in the GC-MS/MS system, operating in negative chemical ionization mode and in selected reaction monitoring. The two most intense transitions were used to monitor ethyl glucuronide and deuterated internal standard. All the validation parameters fulfilled the international acceptance criteria. LOD and LOQ were set at 2.0 and 3.0 pg/mg respectively. This method was applied to 194 hair samples collected from teetotallers and alcohol consumers and represents a suitable alternative to LC-MS/MS for the determination of EtG in hair samples, in particular when scarce quantity of hair is available. This study confirmed that pulverization of hair increases the concentration of EtG, but some variability of EtG levels remains probably due to the presence of non-homogeneous material even though pulverization.