Squalene in hair—a natural reference substance for the improved interpretation of fatty acid ethyl ester concentrations with respect to alcohol misuse

Abstract

Fatty acid ethyl esters (FAEE) are incorporated into hair mainly from sebum. For this reason, the use of their concentration C FAEE as marker of excessive alcohol consumption is complicated by interindividual differences of the activity of the sebum glands and of elimination by hair care and hair cosmetics. Furthermore, an influence of the investigated hair length due to increasing accumulation from proximal to distal was found. Therefore, it was examined whether these sources of error can be avoided if in addition to C FAEE the relative FAEE concentrationa C FAEE/ C SQ related to squalene SQ as a natural reference compound were used for interpretation. Sebum containes about 10–20% SQ. A sensitive and reliable method for the determination of SQ in addition to FAEE from the same hair extracts by high performance liquid chromatography with photo diode array detector (HPLC-DAD) was developed. The concentrations of ethyl myristate, ethyl palmitate, ethyl oleate, ethyl stearate and squalene were determined and C FAEE/ C SQ was calculated for 13 teetotallers, 16 social drinkers, 12 fatalities with excessive alcohol abuse at life time and 9 cases with unclear alcohol anamnesis. C SQ ranged from 0.02 to 1.97 μg/mg (mean 0.67 μg/mg). From the results follows that squalene enables a control of the lipid content of hair and a correction of C FAEE in cases with deviations from the usual lipid content in a similar way as creatinine in urine. Preliminary values of C FAEE/ C SQ were suggested for the upper limit for teetotallers (< 0.6 ng/μg) and the lower limit for excessive alcohol abuse (> 1.5 ng/μg). However, the relative concentration C FAEE/ C SQ cannot completely replace the absolute concentration C FAEE, and both should regularly be used for an improved interpretation with respect to alcohol abuse.