METHODS: An Agilent 1200 series high-performance liquid chromatography (HPLC) unit using a diode-array detector (DAD) has been employed and optimized to detect IPTS in cosmetic products. For the separation, a reverse-phase Hypersil Gold C8 column (5 μm, 4.6 mm i.d. 250 mm) 5 mM tetrabutylammonium phosphate buffer 50 : 50, (v/v) solution in acetonitrile as mobile phase, in isocratic mode and a flow rate of 0.8 mL min(-1) were used. A second method using a gas chromatography/mass selective detector GC-MSD was also developed to confirm the IPTS identity in the cosmetic products.
RESULTS: Recoveries of IPTS from cosmetic matrices such as a lotion, cleansing milk and a cream ranged from 94.0% to 101.1% with <5% relative standard deviation (%RSD) showing good accuracy and repeatability of the method. The six-point calibration curves (determined over the range 0.5-50 μg mL(-1) ) have a correlation coefficient of 0.9999 (based on HPLC peak area) and 0.9998 (based on HPLC peak height). The intra- and interday precisions (measured by the %RSD) of the method were <2% and <5%, respectively, indicating that the developed method is reliable, precise and reproducible. The detection and quantification limit of the method were found to be 0.5 μg mL(-1) and 1.6 μg mL(-1) , respectively. Analyses of 83 commercial cosmetics showed no presence of IPTS.
CONCLUSIONS: The validation data indicated that this method was suitable for the quantitative analysis of IPTS in commercial cosmetics. This method is applicable for analyses of trace levels of IPTS in cosmetics and has the advantage of using only simple sample preparation steps.
OBJECTIVE: It was hypothesised that RL congeners will be distributed differently at different temperature, which caused the produced RL to have different properties. This brought about the idea of a tailored production of RL for specific application through temperature control. Thus, this study aimed to investigate the distribution of RLs congeners by B. thailandensis E264 in response to different temperatures.
METHODOLOGY: B. thailandensis E264 was grown at three different temperatures (25 °C, 30 °C, and 37 °C) for nine days and subjected to metabolomic analysis using liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QToF-MS).
RESULTS: The findings indicated that temperature significantly affected the metabolomic distribution of B. thailandensis E264, with mono-rhamno-mono-lipid and mono-rhamno-di-lipid being the predominant metabolites at 37 °C and 30 °C, with relative abundances of 64.1% and 65.3%, respectively. In comparison, di-rhamno-di-lipid was detected at 25 °C with an overall relative abundance of 77.7%.
CONCLUSION: This investigation showed that changing the cultivation temperature of the non-pathogenic B. thailandensis E264 produces diverse rhamnolipid congeners, which could enable the targeted synthesis of specific RLs for various applications and increase the market value of biosurfactants.