Simultaneous quantitative estimation of oxybenzone and 2-ethylhexyl-4-methoxycinnamate in sunscreen formulations by second order derivative spectrophotometry

Simultaneous determination of 2-ethylhexyl-4-methoxycinnamate (OMC) and oxybenzone (OB) in commercial sunscreen formulations has been achieved by using second order derivative spectrophotometry. The analytical methodology described does not require elaborate pretreatment of samples. The results obtained could be validated by reverse phase HPLC assay by using isocratic methanol: water (88: 12) solvent system. The sensitivity of the developed derivative spectrophotometry method was determined to be 9.0 × 10−3 L/mg for OB and 9.56 × 10−3 L/mg for OMC. The limit of instrumental detection (LOD) was determined to be 0.6 mg/L for OB and 1.38 mg/L for OMC with relative standard deviation of 0.001 and 0.004 for OB and OMC respectively. The method developed can be used for quick assay of commercial sunscreens.