Non-destructive plasticizer screening using a direct inlet probe-atmospheric pressure chemical ionization source and ion trap mass spectrometry.

Abstract

In recent years, several ambient ionization techniques, where solid and/or liquid samples are brought directly into the ion source without any sample preparation and chromatographic separation, have been introduced for mass spectrometric (MS) analyses. Using the direct inlet probe-atmospheric pressure chemical ionization (DIP-APCI)-MS and DIP-APCI-MS(n) methods presented here, a non-destructive screening analysis for plasticizers directly from plastic articles can be performed. The DIP-APCI ion source developed in our laboratory uses a temperature-programmed push rod to introduce solid or liquid samples into a homemade APCI ion source. The DIP-APCI ion source was coupled to an ion trap (IT) mass spectrometer and selected source parameters were optimized. To enable a screening analysis for plasticizers, standards substances of several phthalates and other plasticizers were analyzed and their fragmentation behavior during collision-induced dissociation (CID) was studied. Using DIP-APCI-ITMS, plasticizers can be detected directly from plastic articles and identification is possible through MS(n) experiments. For example, the isomeric phthalates di(2-ethylhexyl) phthalate and di-n-octyl phthalate can be differentiated according to their fragmentation behavior. There are several advantages of the DIP-APCI source in comparison to many other ambient desorption ion sources: (i) well-defined gas phase matrix, (ii) precisely adjustable reagent gases (e.g. O2 for negative APCI), (iii) well-defined probe temperature, and (iv) fully automated operation.