This article proposes a new method in solid-phase microextraction (SPME) that quantifies extracted analytes without the need to consider their mass distribution.
Solid-phase microextraction (SPME) is a widely used sampling technique to enable efficient extraction of a broad range of analytes. Generally, SPME achieves non-exhaustive extraction, and therefore the analyte mass transfer distribution in the sampled multiphase system should be considered while developing a calibration method. The method proposed in the current article relies on the generation of mass response curves by loading a known analyte mass onto the absorbent phase of a SPME fiber, and then conducting analysis by the preferred technique. Precise and accurate deposition of analyte over the restricted dimension of a fiber is demonstrated for the first time by using a drop-on-demand microdrop printer. This system enables direct, non-contact deposition of micron-sized drops that contain negligible solvent volumes (<1 nL), on the center of the extraction phase of the fiber, which enables immediate analysis. Printed fiber response curves were determined herein, with three model compounds of different volatility—2,4-dinitrotoluene (2,4-DNT), diphenylamine (DPA), and 1,3 diethyl-1,3-diphenylurea (ethyl centralite, EC), using two analytical techniques, gas chromatography–mass spectrometry (GC–MS) and ion mobility spectrometry (IMS). Quantification of the absolute amounts extracted by headspace SPME yielded comparable results between the two methods of analysis with only less than 10 percent variation for 2,4-DNT and EC and less than 30 percent for DPA. In comparison, quantification by the traditional liquid injection/spike response curves determined by each technique led to mass estimates that were significantly greater by hundreds of percent. 39 references (publisher abstract modified)