Solid-phase microextraction (SPME) calibration using inkjet microdrop printing for direct loading of known analyte mass on to SPME fibers |
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Authors: | Sigalit Gura Monica Joshi Jose R Almirall |
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Institution: | (1) Department of Chemistry and Biochemistry and International Forensic Research Institute, Florida International University, 11200 SW 8th St. OE 116A, Miami, FL 33199, USA; |
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Abstract: | Solid-phase microextraction (SPME) is a widely used sampling technique that has been proved 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. Here, a new method,
aimed at quantifying the extracted analytes without the need to consider their mass distribution, is proposed. This method
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 utilizing a drop-on-demand microdrop printer. This system enables direct,
non-contact deposition of micron-sized drops containing 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% variation for 2,4-DNT and EC and less than 30% 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. |
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