Research article Received: 10 March 2014,
Revised: 25 August 2014,
Accepted: 30 November 2014
Published online in Wiley Online Library
(wileyonlinelibrary.com) DOI 10.1002/bio.2842
Rapid method for the quantification of hydroquinone concentration: chemiluminescent analysis Tung-Sheng Chen,a,b* Show-Yih Liou,c Wei-Wen Kuo,d Hsi-Chin Wu,e Gwo-Ping Jong,f Hsueh-Fang Wang,g Chia-Yao Shen,h V. Vijaya Padma,i Chih-Yang Huanga,j,k* and Yen-Lin Changl* ABSTRACT: Topical hydroquinone serves as a skin whitener and is usually available in cosmetics or on prescription based on the hydroquinone concentration. Quantification of hydroquinone content therefore becomes an important issue in topical agents. High-performance liquid chromatography (HPLC) is the commonest method for determining hydroquinone content in topical agents, but this method is time-consuming and uses many solvents that can become an environmental issue. We report a rapid method for quantifying hydroquinone content by chemiluminescent analysis. Hydroquinone induces the production of hydrogen peroxide in the presence of basic compounds. Hydrogen peroxide induced by hydroquinone oxidized light-emitting materials such as lucigenin, resulted in the production of ultra-weak chemiluminescence that was detected by a chemiluminescence analyzer. The intensity of the chemiluminescence was found to be proportional to the hydroquinone concentration. We suggest that the rapid (measurement time, 60 s) and virtually solvent-free (solvent volume, 10 (strongly basic). Intense chemiluminescence was not observed when HQ reacted with amino acids not containing side chains (glutamine, glycine, proline, serine, tryptophan) or with side chains in which the pKa values were acidic or weakly basic (cysteine, glutamic acid, histidine). Therefore we suggest that intense chemiluminescence can be detected if HQ reacts with a strong base or with amino acids with a side chain with a high pKa. The pKa values were referred from the website of the Department of Chemistry, Michigan State University, USA. The data for chemiluminescence intensity were expressed as mean ± standard deviation (n = 3). The concentration of amino acid used in this study was 1 mg/ml.
Conclusion Conventional HPLC quantification of HQ is time consuming, and the mobile phases (organic solvents) may cause environmental
Luminescence 2015
problems. We report a convenient and rapid chemiluminescent method for investigating HQ content. The principle of this chemiluminescent method was based on the observation of intense chemiluminescence induced by mixing HQ and basic amino acids with side chains with a high pKa. The production of hydrogen peroxide plays a central role in this chemiluminescent method. Although many articles report chemiluminescent methods regarding hydrogen peroxide determination (7,8), to our knowledge no article had described the relationship between hydroquinone and chemiluminescent analysis. We suggest that the described rapid (measurement time, 60 s) and virtually solvent-free (solvent volume,
Revised: 25 August 2014,
Accepted: 30 November 2014
Published online in Wiley Online Library
(wileyonlinelibrary.com) DOI 10.1002/bio.2842
Rapid method for the quantification of hydroquinone concentration: chemiluminescent analysis Tung-Sheng Chen,a,b* Show-Yih Liou,c Wei-Wen Kuo,d Hsi-Chin Wu,e Gwo-Ping Jong,f Hsueh-Fang Wang,g Chia-Yao Shen,h V. Vijaya Padma,i Chih-Yang Huanga,j,k* and Yen-Lin Changl* ABSTRACT: Topical hydroquinone serves as a skin whitener and is usually available in cosmetics or on prescription based on the hydroquinone concentration. Quantification of hydroquinone content therefore becomes an important issue in topical agents. High-performance liquid chromatography (HPLC) is the commonest method for determining hydroquinone content in topical agents, but this method is time-consuming and uses many solvents that can become an environmental issue. We report a rapid method for quantifying hydroquinone content by chemiluminescent analysis. Hydroquinone induces the production of hydrogen peroxide in the presence of basic compounds. Hydrogen peroxide induced by hydroquinone oxidized light-emitting materials such as lucigenin, resulted in the production of ultra-weak chemiluminescence that was detected by a chemiluminescence analyzer. The intensity of the chemiluminescence was found to be proportional to the hydroquinone concentration. We suggest that the rapid (measurement time, 60 s) and virtually solvent-free (solvent volume, 10 (strongly basic). Intense chemiluminescence was not observed when HQ reacted with amino acids not containing side chains (glutamine, glycine, proline, serine, tryptophan) or with side chains in which the pKa values were acidic or weakly basic (cysteine, glutamic acid, histidine). Therefore we suggest that intense chemiluminescence can be detected if HQ reacts with a strong base or with amino acids with a side chain with a high pKa. The pKa values were referred from the website of the Department of Chemistry, Michigan State University, USA. The data for chemiluminescence intensity were expressed as mean ± standard deviation (n = 3). The concentration of amino acid used in this study was 1 mg/ml.
Conclusion Conventional HPLC quantification of HQ is time consuming, and the mobile phases (organic solvents) may cause environmental
Luminescence 2015
problems. We report a convenient and rapid chemiluminescent method for investigating HQ content. The principle of this chemiluminescent method was based on the observation of intense chemiluminescence induced by mixing HQ and basic amino acids with side chains with a high pKa. The production of hydrogen peroxide plays a central role in this chemiluminescent method. Although many articles report chemiluminescent methods regarding hydrogen peroxide determination (7,8), to our knowledge no article had described the relationship between hydroquinone and chemiluminescent analysis. We suggest that the described rapid (measurement time, 60 s) and virtually solvent-free (solvent volume,
