Introduction: For centuries, henna with its active substance lawsone has been used in
the Arab and Hindu cultures as a hair dye or as expression of body art by applying it on
the hands, feet, and body. This form of pure or red henna with lawsone as active ingredient
is potentially genotoxic whereas the temporary black henna tattoo has been reported to
cause allergic skin reactions due to the presence of the skin sensitizer
paraphenylenediamine (PPD).
Aim: To develop and validate a fast UPLC-PDA method to simultaneously determine
lawsone and PPD in henna tattoos and hair dyes with the purpose to evaluate their potential
risk for the consumers.
Material and methods: Extraction of the target molecules is performed by adding the
extraction solvent MeOH to the henna sample. Hereafter, the sample undergoes ultrasonification,
centrifugation and filtration before analysis with the UPLC-PDA device. A
simple C18-column is used and reverse phase chromatography with a final flow of 0,3
mL/min is performed. The conducted methods are standard calibration, standard addition,
Youden calibration and combining two SAC with different sample weights.
Results: Applying a standard calibration method resulted in low recovery for lawsone (74,2
%). Various attempts such as an additional ultra-sonification step, extraction in three steps
or extraction solvent change over resulted in optimal conditions for the method to undergo
method validation. Unfortunately, due to the occurrence of peak splitting and shoulder
formation and the reoccurrence of low recoveries for lawsone and PPD, no method
validation could be conducted. Due to the occurrence of matrix adsorption effect, a
standard addition method was performed whereby the matrix effect was, however, not
eliminated. Therefore, another method to determine the sample composition was
approached, namely combining SAC and YC or combining two SAC with different sample
weights. When comparing the calibration lines of SAC and SAC’, two non parallel lines were
obtained, indicating that the matrix effect was not constant and can be considered as an
incorrigible error.
Conclusion: Due to the matrix interference that is considered as an incorrigible error, the
method is not developed or validated. In the future, the analyst should try to identify the
interferent and develop a method that results in separate signals for the interferent and
the analyte.
