293 METHOD FOR SIMULTANEOUS QUANTITATION OF RESORCINOL The flow rate was changed from 1.5 mL min−1 to 1.3 and 1.7 mL min−1, and the obtained %RSD of theoretical plates for all the analytes were calculated and found to be 0.76, 0.52, and 0.09 for flow minus and 0.38, 0.51, and 0.25 for flow plus, respectively for resorcinol, p-phenylenediamine, and m-aminophenol they were within the acceptance criteria. The optimized detector response of 225 nm was changed to ±5 nm and %RSD of theoretical plates of the λ plus and 1.61, 1.37, and 1.48 λ minus, respectively, and they were within the acceptance criteria. Table III Forced Degradation (%)Studies on Commercial Samples of GR and GG Parameter Resorcinol p-phenylenediamine m-aminophenol GR GG GR GG GR GG Control 0.1 –0.2 –0.6 –0.5 –0.9 –0.8 Acid 20.3 21.6 23.6 28.5 24.3 23.2 Alkali 21.1 22.1 25.9 22.5 20.9 19.9 Peroxide 20.2 20.0 29.5 25.9 22.0 23.4 Reduction 20.0 28.4 24.3 24.5 27.4 23.3 Thermal 23.5 25.1 22.0 20.6 23.2 21.5 Photo 27.6 26.5 29.3 24.4 19.9 24.3 Humidity 21.1 23.0 20.8 23.0 23.4 20.9 Heat 20.1 20.5 20.3 21.4 23.3 22.0 Hydrolysis 20.4 27.6 22.6 23.2 21.5 27.4 GG: Godrej Expert (Godrej Consumer Products, India) GR: Garnier Color Naturals (L’Oreal, India). Table V Assay of Commercial Samples Compound Label claim, mg Calculated value, (mg ± SD) Assay, %GR GG GR GG GR GG Resorcinol 50.0 57.0 50.89 ± 0.58 57.3 ± 0.36 101.2 100.2 p-phenylenediamine 72.0 81.0 71.24 ± 0.61 80.9 ± 0.55 100.1 99.8 m-aminophenol 68.2 71.0 68.24 ± 0.43 71.2 ± 0.51 100.3 100.5 GG: Godrej Expert (Godrej Consumer Products, India) GR: Garnier Color Naturals (L’Oreal, India) SD: standard deviation. Table IV Parameters Studied for Standard and Commercial Samples Parameter RES PPD MAP Standard area 740,355 981,352 62,587 Sample area GR 1,123,920 133,443 117,108 Sample area GG 518,353 870,906 88,744 Sample purity, %101.1 100.6 100.1 Label claim, %25 1 2 Standard weight, mg 50 70 7 Sample weight GR, mg 453 453 453 Sample weight GG, mg 368 368 368 GG: Godrej Expert (Godrej Consumer Products, India) GR: Garnier Color Naturals (L’Oreal, India) MAP: m-aminophenol PPD: p-phenylenediamine RES: resorcinol.

294 JOURNAL OF COSMETIC SCIENCE ACN was used as an organic modifier of the mobile phase. Methanol had played the vital role in the study especially in separating p-phenylenediamine and m-aminophenol by ion paring between the amine groups of these compounds. The effect of variation in mobile phase ratio was studied by varying the ratios of hexane-1-sulfonic acid by ±5 mL, and the results are summarized in Table II. The mobile phase compositions were adjusted as 2.5:2.5:95 v/v/v (mobile phase minus, 0.0094 M of ion pair agent), 5.0:5.0:90 v/v/v (optimized, 0.01 M), and 7.5:7.5:85 v/v/v (mobile phase plus, 0.0105 M of ion pair agent). The %RSD values of t R for resorcinol, p-phenylenediamine, and m-aminophenol at mobile phase ratio plus were found to be 0.18, 0.13, and 0.10, and those at mobile phase ratio minus were found to be 0.21, 0.07, and 0.14, respectively, which were in acceptable limits per ICH guidelines (27). The retention of resorcinol, p-phenylenediamine, and m-aminophenol is usually dependent on the pH of the mobile phase because of partial dissociation of the OH groups and protonation of NH 2 groups in acidic media. In accordance with the pKa values and owing to protonation of NH 2 ,the study of resorcinol, p-phenylenediamine, and m-aminophenol was conducted by changing pH from 2.8 to 2.5 and 3.1 by preparing standard solutions and injecting into the HPLC system. The results are given in Table II. The %RSD values of t R for resorcinol, p-phenylenediamine, and m-aminophenol at pH plus were found to be 0.01, 0.06, and 0.02, and those at pH minus were found to be 0.04, 0.11, and 0.16, respectively, which were within acceptance limits per ICH guidelines (27). The forced degradation studies were indicative of the compliance of method development as per ICH guidelines (32). Stability of sample solution was established, which indicated that the samples could be stored up to 24 hours at 25oC. The assay of commercial samples was consistent with the developed method. CONCLUSIONS The stability-indicating HPLC method optimized by chemometrics and validated per ICH guidelines could be employed for the determination of resorcinol, p-phenylenediamine, and m-aminophenol in hair-coloring products. It used a minimal amount of organic solvents in the mobile phase and thus could be considered more eco-friendly than existing methods. This method could facilitate as a reliable source of routine quality control analysis of the labeled compounds in combined hair dye formulations. ACKNOWLEDGMENTS The authors are thankful to Cystron Laboratories, Vijayawada, Andhra Pradesh, India for providing the necessary facilities to carry out the research work. REFERENCES (1) B. G. Chiari, M. G. J. de Almeida, M. A. Correa and V. L. B. Issac, VLB, “Cosmetics’ quality control,” in Latest Research in to Quality Control, I. Akyar. Ed. (IntechOpen Limited, London, 2012), pp. 337–364. (2) EUR-Lex, Regulation (EC) No 1223/2009 of the European Parliament and of the Council of 30 November 2009 on Cosmetic Products, accessed February 2, 2021, http://eur-lex.europa.eu/legal-content/EN/ ALL/?uri=CELEX%3A32009R1223.