Abstract: A high performance liquid chromatography (HPLC) method was established to detect lawsone and p-phenylenediamine in henna hair-coloring powder.The samples were dissolved by 50% methanol and analyzed by Waters C₁₈ column (150 mm×4.6 mm,5 μm).Mobile phase is methanol and 0.1 mol/L acetic acid aqueous solution (volume ratio of 33.5∶66.5) at a flow rate of 1.0 mL/min.Operating temperature is 30 ℃.Detection wavelength is 280 nm.The detection limit (S/N=3) for lawsone and p-phenylenediamine is 0.018 and 0.014 mg/L respectively,and the limit of quantification (S/N=10) is 0.055 and 0.042 mg/L respectively.A good linear relation displays when lawsone is in the mass concentration range of 0.515-51.50 mg/L (r=0.999 8) and p-phenylenediamine is in the range of 21.50-430.00 mg/L (r=0.999 4).The spiked recoveries (n=3) are within the range of 102.20%-105.42% for p-phenylenediamine and 96.74%-107.30% for lawsone.The relative standard deviations (RSD) of p-phenylenediamine and lawsone are 0.36%-1.34% and 0.99%-2.30% respectively.Among test results of 53 henna hair-coloring powder samples from market,lawsone appears alone in 30 samples;both lawsone and p-phenylenediamine appear in 12 samples;p-phenylenediamine appears alone in seven samples and neither lawsone nor p-phenylenediamine appears in four samples.

Key words: henna hair-coloring powder, high performance liquid chromatography, lawsone, p-phenylenediamine