Rapid On-Site Screening of Prohibited Substances in Spray Cosmetics Using Dielectric Barrier Discharge Ionization and a Miniature Mass Spectrometer

Abstract

The development and application of ambient ionization and miniature mass spectrometry have become the current research hotpot, which is capable of rapid, sensitive, on-site and real-time analysis of samples without complex sample pretreatment. In this study, a rapid on-site method using dielectric barrier discharge ionization (DBDI) and a miniature mass spectrometer was developed for the screening of prohibited substances in spray cosmetics. Helium gas was used as the discharge gas and 1 mm thick quartz glass was used as the dielectric barrier in a custom-made DBDI ion source. The two brass electrodes were 10 mm apart, both mounted outside the quartz glass. The inner diameter of the glass tube at the gas inlet and outlet was 1 mm. When the experiment was carried out, the DBDI ion source was placed 3 cm in front of the discontinuous atmospheric pressure interface (DAPI) of the miniature mass spectrometer. The spray cosmetic sample was placed 8 cm directly above the plasma beam generated by the DBDI. Without any sample pretreatment, once the sample spray valve was pressed, the sample microdroplets generated in the vertical direction collided with the plasma beam generated in the horizontal direction. In the region between the DBDI and the miniature mass spectrometer, the target substances were ionized by energy and charge transfer with the plasma beam, and then detected by the miniature mass spectrometer. The helium flow rate was set at an optimum value of 220 mL/min by a gas mass flow controller. Coupled with the miniature mass spectrometer, four prohibited colorants in disposable hair dye spray and four prohibited fragrances in spray lotion were screened. Based on the observed signal-to-noise ratio (S/N) of the most intense MS/MS fragment peaks and using S/N=3 as a criterion, the limits of detection (LODs) were estimated between 10 and 50 μg/kg for the eight prohibited substances. The entire analysis procedure could be completed within 1 min. The simplified analytical protocol can effectively solve the disadvantages of traditional analytical methods that are cumbersome and time-consuming. The proposed method is simple, rapid, sensitive, efficient, and suitable for rapid on-site screening of prohibited substances in spray cosmetics.

Keywords

• dielectric barrier discharge ionization (dbdi)
• miniature mass spectrometry
• rapid screening
• prohibited substances
• spray cosmetics