An improved automatic analyzer for organic compounds in water based on headspace solid-phase microextraction (SPME) coupled to gas chromatography

An automated analyzer based on solid-phase microextraction (SPME) coupled to gas chromatography (GC) for monitoring organic compounds in water is presented. The instrumental setup, which was tested previously with direct SPME, is now tested in the headspace mode. Memory effects observed in the earlier design were reduced by using glass instead of plastic tubing. Parameters that potentially influence the extraction yield were studied in the laboratory with the use of spiked water samples. These parameters were temperature, salt content, methanol content, pH value, and excess components. The extraction efficiency as a function of the extraction time (absorption profiles) was determined for 24 standard compounds. The method was validated in the laboratory. Good precision (in general <5%) and linearity were observed. With the use of flame ionization, detection limits of quantitation were in the low-ppb range, sufficient for wastewater monitoring. The instrument was tested continuously for 6 days at the wastewater plant of a chemical company in northern Germany. Better stability and robustness were observed in the headspace SPME compared to the direct SPME.