Methodical evaluation and improvement of matrix compatible PDMS-overcoated coating for direct immersion solid phase microextraction gas chromatography (DI-SPME-GC)-based applications.
The main quest for the implementation of direct SPME to complex matrices has been the development of matrix compatible coatings that provide sufficient sensitivity towards the target analytes. In this context, we present here a thorough evaluation of PDMS-overcoated fibers suitable for simultaneous extraction of different polarities analytes, while maintaining adequate matrix compatibility. For this, eleven analytes were selected, from various application classes (pesticides, industrial chemicals and pharmaceuticals) and with a wide range of log P values (ranging from 1.43 to 6). The model matrix chosen was commercial Concord grape juice, which is rich in pigments such as anthocyanins, and contains approximately 20% of sugar (w/w). Two types of PDMS, as well as other intrinsic factors associated with the PDMS-overcoated fiber fabrication are studied. The evaluation showed that the PDMS-overcoated fibers considerably slowed down the coating fouling process during direct immersion in complex matrices of high sugar content. Longevity differences could be seen between the two types of PDMS tested, with a proprietary Sylgard(®) giving superior performance because of lesser amount of reactive groups and enhanced hydrophobicity. Conversely, the thickness of the outer layer did not seem to have a significant effect on the fiber lifetime. We also demonstrate that the uniformity of the overcoated PDMS layer is paramount to the achievement of reliable data and extended fiber lifetime. Employing the optimum overcoated fiber, limits of detection (LOD) in the range of 0.2-1.3 ng/g could be achieved. Additional improvement is attainable by introducing washing of the coatings after desorption, so that any carbon build-up (fouling) left on the coating surface after thermal desorption can be removed.
Department of Chemistry, University of Waterloo, 200 University Avenue West, Waterloo, Ontario, Canada N2L 3G1. Electronic address: ericachemistry@gmail.com.
Érica A
ÉA
Souza-Silva
Department of Chemistry, University of Waterloo, 200 University Avenue West, Waterloo, Ontario, Canada N2L 3G1.
Emanuela
E
Gionfriddo
Supelco Inc., 595 North Harrison Road, Bellefonte, PA 16823, USA.
Robert
R
Shirey
Supelco Inc., 595 North Harrison Road, Bellefonte, PA 16823, USA.
Len
L
Sidisky
Department of Chemistry, University of Waterloo, 200 University Avenue West, Waterloo, Ontario, Canada N2L 3G1. Electronic address: janusz@sciborg.uwaterloo.ca.
Janusz
J
Pawliszyn
D002849:Chromatography, Gas / Q000379:methods*; D004129:Dimethylpolysiloxanes / Q000737:chemistry*; D005504:Food Analysis / Q000379:methods*; D000067030:Fruit and Vegetable Juices / Q000032:analysis*; D057230:Limit of Detection; D010575:Pesticides / Q000032:analysis* / Q000302:isolation & purification; D052617:Solid Phase Microextraction / Q000379:methods*
D004129:Dimethylpolysiloxanes; D010575:Pesticides
Coatings; Food analysis; Gas chromatography (GC); Matrix-compatible; Pesticides residues; Solid-phase microextraction (SPME)