Comparison of silica-based materials for organophosphorus pesticides sampling and occupational risk assessment

A novel air sampler has been designed containing a sorbent based on UVM-7 mesoporous silica doped with Ti. The sorbent has been applied for the determination of organophosphorus pesticides in occupational air, followed by gas chromatography with mass spectrometry detection. Thus, several silica materials with different structures (mesoporous UVM-7 and microporous xerogels) were synthesized, and modified with the addition of Ti and Fe. The structure of these materials was proved by transmission electronic microscopy, energy-dispersive X-ray, X-ray diffraction, nitrogen adsorption-desorption and UV-Vis and Raman spectroscopy. The potential of these materials for the retention of pesticides was evaluated and Ti25-UVM-7 was selected as the best solid phase for analyte sorption. Then, several sampling parameters were optimized and analytical features such as breakthrough volume were determined. Using the designed samplers, quantitative retentions were achieved with recoveries in the range 93-107% for all analytes except for diazinon (82%). RSD values below 13% were obtained. Likewise, the sensitivity of the method was studied, and limits of quantification below 0.5 μg m^-3 were obtained for all pesticides. The reusability of the material was also proved. The developed procedure has been applied to the air sampling and occupational risk assessment, during and after methyl-chlorpyrifos application in orange plantations. High concentrations and exposure rates above the limit value for ensure safe work conditions were obtained. At the same time, the air was sampled with XAD-2 samplers as a reference method, and results obtained with both devices were statistically comparable.