Determination of Lipstick Authenticity Parameters
353
Presented by: Milica Stevic
Introduction
Online marketplaces have not only enabled cosmetic brands to reach out to consumers, but also to counterfeiters. Fake cosmetic products not only infringe upon intellectual property of brands and disrupt the beauty markets, but may also pose a serious threat to consumers’ health. Current cosmetic regulations have failed to eliminate counterfeit products, despite the joint effort of corporations, e-commerce platforms, and the enforcing authorities. This could be due to the lack of quick and reliable analytical methods for identifying counterfeit products. The most reliable way to detect counterfeit cosmetic products is by applying analytical techniques that provide their physicochemical characterisation such as Fourier Transform Infrared Spectroscopy (FT-IR), Thermogravimetric Analysis (TGA), and Differential Scanning Calorimetry (DSC). However, the application of these techniques is costly, time-consuming, and requires experienced operators. Thus, a more efficient approach to the determination of counterfeit cosmetics is required. In this study, ten lipstick products sold under the same brand name and type were purchased from eight different shopping channels, online and in-store, including the original brand store. Analytical characterisation was applied to determine whether the lipstick was genuine (GL) or counterfeit (CL), while physical characterisation was applied to determine physical parameters. The aim of the study was to determine whether rheological parameter, yield stress, and texture parameter, hardness, could be used as potential authenticity parameters.
Methods
DSC and TGA were performed by scanning at 10oC/min using Q2000 DSC and Discovery TGA (TA Instruments, USA), respectively. FT-IR analysis was carried out using Spectrum 100 (PerkinElmer, USA). Rheological characterisation was performed using MARS iQ Air (Thermo Fisher, UK) in oscillatory amplitude sweep mode with a constant frequency of 1 Hz. Texture analysis was carried out by a TA.XT Plus Texture Analyser (Stable Micro System, UK) with a 2-mm diameter needle probe. Statistical analysis was performed using SPSS software.
Results
A significant difference in FT-IR spectra and thermograms of GL and CL was identified. As such, the method was applied to authenticate lipsticks, that is, to distinguish between GL and CL samples. Rheological and texture data for yield stress and hardness of GL and CL was collected. The data obtained in the physical characterisation was processed using statistical analysis. Three statistical parameters (SP) were studied: (1) minimum and maximum (min–max), (2) the range or the difference between minimum and maximum (R), and (3) standard deviation (SD). Ten replicas were analysed for each individual channel. Average values for SPs are given here: Yield stress - GL: min—max=222.00–243.84 Pa; R=21.84 Pa; SD=8.92; CL; min—max=58.33–216.68 Pa; R=146.98 Pa; SD=48.55. Hardness - GL at 2.5 mm: min—max=276.26–371.92 g; R=95.66 g; SD=28.50; CL at 2.5 mm: min—max=108.43-245.26 g; R=136.83 g; SD=46.29.
Discussion
Statistical analysis found that the min and max absolute values for overall yield stress and hardness are higher for GL, whereas CL has higher R and SD. The difference in hardness between GL and CL samples indicates the difference in lipstick composition. Some CLs were proven by FT-IR to have ingredients different from the INCI list shown on the packaging. When using yield stress as potential authenticity parameter, it is important to analyse all three statistical parameters. This is because softer CL can be smoother, resulting in low R and SD (similar to the average GL), and harder ones can be grainier, resulting in high R and SD (similar to the average CL). The average R and SD for hardness are high because the GLs are hard and brittle. Hence, in terms of hardness it is more reliable to only investigate the min-max parameter.
Conclusion
This study explored the application of physical parameters, yield stress and hardness, for authentication of lipsticks. The authenticity of the lipsticks was determined using analytical techniques for physicochemical characterisation. It was found that for the texture parameter hardness only the absolute minimum and maximum values can reliably be used, whereas in the case of the yield stress the range and standard deviation must be defined, as well. The proposed authenticity parameters approach could be used to quickly and reliably detect counterfeit lipstick products.
Online marketplaces have not only enabled cosmetic brands to reach out to consumers, but also to counterfeiters. Fake cosmetic products not only infringe upon intellectual property of brands and disrupt the beauty markets, but may also pose a serious threat to consumers’ health. Current cosmetic regulations have failed to eliminate counterfeit products, despite the joint effort of corporations, e-commerce platforms, and the enforcing authorities. This could be due to the lack of quick and reliable analytical methods for identifying counterfeit products. The most reliable way to detect counterfeit cosmetic products is by applying analytical techniques that provide their physicochemical characterisation such as Fourier Transform Infrared Spectroscopy (FT-IR), Thermogravimetric Analysis (TGA), and Differential Scanning Calorimetry (DSC). However, the application of these techniques is costly, time-consuming, and requires experienced operators. Thus, a more efficient approach to the determination of counterfeit cosmetics is required. In this study, ten lipstick products sold under the same brand name and type were purchased from eight different shopping channels, online and in-store, including the original brand store. Analytical characterisation was applied to determine whether the lipstick was genuine (GL) or counterfeit (CL), while physical characterisation was applied to determine physical parameters. The aim of the study was to determine whether rheological parameter, yield stress, and texture parameter, hardness, could be used as potential authenticity parameters.
Methods
DSC and TGA were performed by scanning at 10oC/min using Q2000 DSC and Discovery TGA (TA Instruments, USA), respectively. FT-IR analysis was carried out using Spectrum 100 (PerkinElmer, USA). Rheological characterisation was performed using MARS iQ Air (Thermo Fisher, UK) in oscillatory amplitude sweep mode with a constant frequency of 1 Hz. Texture analysis was carried out by a TA.XT Plus Texture Analyser (Stable Micro System, UK) with a 2-mm diameter needle probe. Statistical analysis was performed using SPSS software.
Results
A significant difference in FT-IR spectra and thermograms of GL and CL was identified. As such, the method was applied to authenticate lipsticks, that is, to distinguish between GL and CL samples. Rheological and texture data for yield stress and hardness of GL and CL was collected. The data obtained in the physical characterisation was processed using statistical analysis. Three statistical parameters (SP) were studied: (1) minimum and maximum (min–max), (2) the range or the difference between minimum and maximum (R), and (3) standard deviation (SD). Ten replicas were analysed for each individual channel. Average values for SPs are given here: Yield stress - GL: min—max=222.00–243.84 Pa; R=21.84 Pa; SD=8.92; CL; min—max=58.33–216.68 Pa; R=146.98 Pa; SD=48.55. Hardness - GL at 2.5 mm: min—max=276.26–371.92 g; R=95.66 g; SD=28.50; CL at 2.5 mm: min—max=108.43-245.26 g; R=136.83 g; SD=46.29.
Discussion
Statistical analysis found that the min and max absolute values for overall yield stress and hardness are higher for GL, whereas CL has higher R and SD. The difference in hardness between GL and CL samples indicates the difference in lipstick composition. Some CLs were proven by FT-IR to have ingredients different from the INCI list shown on the packaging. When using yield stress as potential authenticity parameter, it is important to analyse all three statistical parameters. This is because softer CL can be smoother, resulting in low R and SD (similar to the average GL), and harder ones can be grainier, resulting in high R and SD (similar to the average CL). The average R and SD for hardness are high because the GLs are hard and brittle. Hence, in terms of hardness it is more reliable to only investigate the min-max parameter.
Conclusion
This study explored the application of physical parameters, yield stress and hardness, for authentication of lipsticks. The authenticity of the lipsticks was determined using analytical techniques for physicochemical characterisation. It was found that for the texture parameter hardness only the absolute minimum and maximum values can reliably be used, whereas in the case of the yield stress the range and standard deviation must be defined, as well. The proposed authenticity parameters approach could be used to quickly and reliably detect counterfeit lipstick products.