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.