Material and Methods

January 15, 2014

In the absence of comprehensive studies in India, Delhi non-profit Centre for Science and Environment analysed lipsticks and fairness creams for heavy metals. Here are the details of the methodology adopted for the study

Sampling Methodology
Thirty samples of lipsticks, 32 samples of fairness creams, 8 samples of lip-balm and 3 samples of anti-ageing creams were purchased from local market of Delhi. The details of the samples are presented in Table 2 Table and 3.

Equipment: Atomic Absorption Spectrometer (Thermo) Solar M-6 Series, equipped with Flame and Flameless techniques was used for analysis.

Glassware: All the glassware were cleaned with detergent and 10% nitric acid and rinsed thoroughly with distilled water before use.

Chemicals: All the chemicals used were purchased from E Merck. The water used in all the experiments was ultrapure water obtained from Elga water purification system.

Sample preparation for Lead, Cadmium, Chromium and Nickel Determination
Lipstick, lip-balm and anti-ageing creams were analyzed for lead, cadmium, chromium and nickel. Sample preparation for the determination of Lead, Cadmium, Chromium and Nickel was done following the method of Chauhan et al . About 1.0 g of each sample was digested in 5.0 mL mixture of concentrated acid HNO3:HCLO4 (3:1) for 2-3 hours on a hot plate at 900C. Then 3.0 mL of acid mixture was again added and then again heated for 2-3 hours to complete the digestion. The above digested samples were cooled and about 5.0 mL ultra pure water was added mixed well and volume made upto 25 mL in volumetric flask. The solution was then finally filtered through Whatman filter paper (Number 41). The clear solution was used for metal quantification.

Sample preparation for Mercury Determination
Fairness creams were analyzed for mercury. Application note provided by Clark et. al. of CETAC Technologies of USA was used for the sample preparation for mercury estimation . The samples were weighed (~0.2g) into the beaker. The samples were predigested with 2 mL of H2SO4 and 2 mL HNO3 for 1.5 hours at 800C. This initial predigest step dissolved/dispersed the samples and then allowed to cool to room temperature. Then 7.0 mL of 5% KMnO4 and 5 mL 3% HCl were added to each beaker and then heated at 950C for 2 hours. After again cooling to room temperature, 3.0 mL of 12% hydroxylamine solution was added to reduce the KMnO4. The beakers were swirled to assure complete reaction with the excess KMnO4. They were then brought up to a final volume of 25 mL with 3% HCl with thorough mixing prior to instrument analysis of the samples.

Sample analysis for Lead, Cadmium, Chromium and Nickel Determination:
Lead, Cadmium, Chromium and Nickel were determined using flame atomic absorption spectrometry. Air-acetylene flame was used for Lead, Cadmium and Nickel while air-acetylene-nitrous oxide flame was used for Chromium determination. Standard solutions were prepared in five different concentrations for each metal separately to obtain calibration curve for quantitative analysis. All the measurements were run in triplicate for the samples and standard solutions. Deuterium lamp was used for background correction.

Sample analysis for Mercury Determination:
Digested samples were analyzed for Mercury using flameless atomic absorption spectrometry. Standard solutions were prepared in five different concentrations to obtain calibration curve for quantitative analysis. All the measurements were run in triplicate for the samples and standard solutions. Deuterium lamp was used for background correction.

Recovery test was performed for all the metals. Recovery was found to be more than 90% in all the cases.

 Chauhan AS, Bhadauria R, Singh AK, Lodhi SS, Chaturvedi DK, Tomar VS. Determination of Lead and Cadmium in cosmetic products. J. Chem. Pharm. Res., 2010, 2(6):92-97