2.3. HS-SPME procedure
HS-SPME extraction was performed using a Supelco (Bellefonte,USA) manual holder containing a fiber assembly with a 100 μmpolydimethylsiloxane(PDMS) coating. The fiber was conditioned in the injection port of a gas chromatograph at 250 °C for 30 min prior to use and blank desorption was performed. 2 mL of aqueous sample (standard
or real) was placed in 4 mL glass vial with PTFE/silicone septa, which contained 10% (w/v) sodium chloride salt. The fiber was exposed to the headspace of a sample, kept at a selected temperature for a set time, retracted into a needle, and introduced into the injection port of gas chromatograph. Extraction was supported by magnetic stirring at
the highest possible level. A fiber blank experiment was performed to ensure that there were no contaminants on the fiber. For optimization of HS-SPME process, the factors affecting extraction efficiency (headspace volume, extraction time, temperature, sample ionic strength and agitation speed) were investigated.