Microwave induced plasma desorption ionization (MIPDI) mass spectrometry for qualitative and quantitative analysis of preservatives in cosmetics

Abstract

Ambient ion sources for mass spectrometry have been frequently reported in the past 10 years. The most attractive features of these ion sources are that they are fast and an easy way to analyze various samples. The microwave induced plasma desorption ionization source, the MIPDI source, is one among them. In this study, the qualitative and quantitative behavior of the MIPDI source has been demonstrated by analyzing the preservatives in cosmetics for the first time. The detection limit for the preservatives is as low as pg mm⁻². The relative standard deviation of continuous analysis is 5.25%. Preservatives in commercial cosmetics samples were successfully detected including those in facial cream, sunscreen and moisturizer. The fast screening capability of the MIPDI source is proved. Five commercial samples were successfully classified into two groups within 5 minutes according to the added preservatives. The ability to quantitatively analyze the preservatives in commercial cosmetics was also investigated. The standard adding and calibration curve methods were used in the quantitation process. The results showed that the quantitative analysis accuracy of MIPDI-MS is −49% and −66% for a liquid state sample and solid state sample respectively, i.e. semi-quantitation is possible. A conceptual experiment was also conducted to validate the accurate quantitative analysis capability of MIPDI-MS. The concentration of caffeine in cosmetic matrices was quantified satisfactorily with no sample pretreatment, with an RSD value of 5.5% and accuracy of 3.6%. The approaches established in this work indicate that the MIPDI source is a promising tool in future applications where rapid qualitative and quantitative analysis is needed.