Accelerating semivolatile extraction kinetics: Determination of organophosphorus pesticides by vacuum assisted...

Accelerating mass transfer kinetics is a key objective in the extraction of semivolatile compounds by headspace solid-phase microextraction (HS-SPME) to reduce their extraction time. Vacuum-assisted HS-SPME (Vac-HS-SPME) has emerged as a promising approach to enhance extraction kinetics by reducing headspace pressure and promoting faster equilibration. Although some applications have been addressed previously, the extent to which vacuum conditions improve extraction rates has not been extensively evaluated. In this work, the effect of reduced pressure on the extraction kinetics of a set of organophosphorus pesticides with different volatilities was systematically investigated.

Ten organophosphorus pesticides with a wide range of Henry's constants were selected to evaluate the effect of vacuum conditions on extraction kinetics. Key extraction parameters, including temperature, equilibration time, fiber exposure time, and fiber coating type, were optimized. Comparison of extraction time profiles under atmospheric and reduced pressure conditions showed that vacuum increased extraction rates by up to 9.6-fold, with the greatest enhancement observed for compounds with lower Henry's constants. Consequently, equilibration times were reduced from ≥ 90 min to 30 min, compared with conventional HS-SPME. The optimized Vac-HS-SPME method showed good linearity, satisfactory precision, low limits of detection and quantification, and was successfully applied to the determination of organophosphorus pesticides from surface water.

This work provides evidence that reduced pressure is an effective strategy to accelerate extraction kinetics in HS-SPME, particularly for low-volatility compounds, which otherwise cannot be analyzed via gas-phase extractions due to practical time limitations. The findings suggest a clear relationship between analyte properties and kinetic enhancement, providing a useful guide for rational method development. This contribution supports the use of Vac-HS-SPME as an efficient and reliable approach for the determination of semivolatile organophosphorus pesticides in environmental samples.