Development of polydimethylsiloxane-microdiamond composite materials for application as sorptive devices

The development and application of non-porous and porous sorptive rods, comprised of polydimethylsiloxane-microdiamond (PDMS-MD) composites, is reported. The PDMS-MD composites were made porous using inorganic salt (NaCl and NaHCO₃) particles as dissolvable templates. Materials with pore size of ~40 µm down to ~5 µm were produced. The advantages of incorporating up to ~60%microdiamond (2-4 µm) into PDMS included: (1) significant increase in the density, which saw the rods sink within the aqueous sample without addition of secondary metal or glass materials, (2) significant improvement in mechanical stability (the porous composite rods could be thermally treated multiple times before application, unlike porous PDMS), (3) increased thermal stability up to 450-500 °C with only 6% weight loss of volatile components, and (4) higher thermal conductivity, estimated to be 108% higher than for PDMS. The PDMS-MD investigated as a sorbent for extraction, followed by liquid desorption and GC-FID analysis. Recovery of the sorbent for test solutes, isoamyl acetate, ethyl hexanoate, ethyl octanoate, ethyl decanoate, and phenethyl acetate, was found to range from ~87% to >100, with RSD of 2.10-12.50% in synthetic wine samples. Non-porous composite rods provided similar % recoveries to a commercial sorptive device (PDMS Twister), whereas porous rods showed improved % recovery for most of the test solutes (>10-20%) when applied under similar conditions. The limits of detection (LOD) for the above solutes within the developed method ranged from 0.60 to 27.30 µg L^-1). Application of the PDMS-MD-LD-GC-FID method to white wine samples demonstrated how the PDMS-MD composite material can be applied as a robust and an efficient sorptive phase for trace chemical analysis.