Simultaneous quantification of urea and allantoin in cosmetic products by nano-HPLC using a highly hydrophilic monolith

Abstract

Urea and allantoin are two important additives in cosmetic products for the treatment of dry skin as well as for skin protection and regeneration. In this research, a highly hydrophilic monolith prepared by co-polymerization of N,N-dimethyl-N-acryloyloxyethyl-N-(3-sulfopropyl)ammonium betaine (SPDA) and N,N’-methylenebisacrylamide (MBA) was first exploited for the simultaneous quantification of urea and allantoin in cosmetic products by nano-HPLC in the HILIC mode. The whole separation process could be completed within six minutes using isocratic elution. Due to the extremely high hydrophilicity of this monolithic column, a relatively low content (80%) of ACN in the mobile phase was required to achieve satisfactory separation, and therefore the solubility problems for polar compounds was also avoided in comparison with previously reported results on the commercial columns. Method validation was also accomplished with respect to linearity, reproducibility, selectivity, recovery, stability, LOD and LOQ. The recoveries of urea and allantoin from spiked cosmetic samples were 95.6%-100% and 94.1%-99.9%, respectively. Validation results indicate that this HILIC method based on the miniaturized poly(SPDA-co-MBA) monolith can be applied successfully to the fast and efficient determination of urea and allantoin in cosmetic samples. The miniaturized column format, the low sample consumption (20 nL), and excellent separation efficiency could make this highly hydrophilic monolith an attractive choice for the detection of trace polar analytes from complex samples in future.