Evaluation of headspace Solid Phase Micro-extraction method for analysis of phosphine residues in wheat

  • Y. L. Ren Cooperative Research Centre for National Plant Biosecurity, Australia, Email: y.ren@murdoch.edu.au; School of Biological Science and Biotechnology, Murdoch University, South Street, Murdoch, WA, 6150 Australia; Department of Agriculture and Food, Western
  • B. Padovan CSIRO Entomology, GPO Box 1700, Canberra ACT 2601, Australia


This new method utilizes headspace-solid-phase micro extraction (HS-SPME) for pre-concentration of PH3. Phosphine was determined with gas chromatography/pulsed flame photometric detector (PFPD). Spiked samples were used for calculation of phosphine residue in grain. Four types of fibres (100μm-PDMS, 85μm- CAR/PDMS, 75μm-CAR/PDMS and 65μm-PDMS/DVB) were tested. The bipolar fibres (CAR/PDMS and PDMS/DVB) can extract PH3, but the non-polar fibre (PDMS) did not. Larger size fibres extracted PH3 more efficiently than the smaller size fibres (e.g., 85 μm > 75 μm > 65 μm). The 85μm CAR/PDMS fibre was used to optimize the different parameters that affect the SPME extraction efficiency of PH3. In the validation study, 50 grams of wheat in a 250 mL glass flask and capped with an open-top screw cap and PTFE/Silicon septa were spiked at 0.02 ng PH3/g of wheat. The flask was then heated to 45°C in an oil bath for 45 min, after which time the 85 μm CAR/PDMS fibre was exposed for 20 min and then exposed in the heated injection port of a GC/PFPD and desorbed for 2 min. Under conditions of the validation study, the limit of detection (LOD) or level of quantification (LOQ) was in the range of 0.005–0.01 ng PH3/g of wheat.

Keywords: Fumigant, Phosphine, Residue, SPME, HS-SPME
Section: Fumigation, Modified Atmospheres and Hermetic Storage