LC-MS/MS (QTRAP 5500 mass spectrometer) was done in multiple reaction monitoring (MRM), enhanced product ion (EPI) and MS3 mode. The lower limit of quantitation was 0.05 mg/L for EtG and the cut-off for the detection of EtS 0.01 mg/L.
Altogether 11 hair tonics from 8 manufacturers were tested, with 1 product in 3 different lots. EtG ranged between 0.07 and 1.06 mg/L (7 products from 4 manufacturers) and was almost identical in the 3 lots of 1 product (1.01-1.06 mg/L). EtS was found in 3 out of the 11 hair tonics.
EtG is quite frequently present in commercially available herbal hair tonics. Using EtG in hair as a marker of alcohol (ab)use, one has to consider external sources of EtG and has to assess the use of hair care products, esp. if the patient denies any ethanol intake. Whether EtS is a more reliable alcohol (ab)use marker, as sometimes discussed, should be critically assessed against the background of its broad use in large amounts in industrial chemistry.