| Nonylphenol ethoxylates(NPEOs)and nonylphenol(NP)are commonly used nonionic surfactants in pesticide production.They accumulate in farmland environment with application of pesticides,and they not only affect ecological environment but also endanger human health through the food chain.In this study,NPEOs and NP were taken as the research object and a liquid chromatography-fluorescence detection method was established.Content distribution characteristics of NPEOs and NP in 43 insecticide preparations of 4 dosage forms that emulsion(EC),water emulsion(EW),suspension agent(SC)and microemulsion(ME)were analyzed.The dissolution,migration and contrubition of NPEOs and NP in outer package were also analyzed.And according to the recommended application method,mode and rate of adsorption-desorption and influence factors of NPEO and NP entering soil were explored.The main results of experiments are as follows:(1)Establishment of detection method:By using a gradient elution procedure,NPEOs and NP separation and detection response were improved with optimizing the excitation and emission wavelengths,changing mobile phase ratio and flow rate.The detection conditions were obtained as followed:excitation wavelength was 260 nm and emission wavelength was 308 nm;gradient elution was at 0～6～8min,85%～25%～90%of methanol;flow rate was 1 m L/min.The linear relationship of NPEOs and NP was both well in the range of 0.01～10 mg/L(r>0.999),The detection limit(LOD)was 0.01 mg/L and the limit of quantification(LOQ)was 0.05 mg/L.(2)Detection and content distribution:Detection rate of NPEOs was 60.47%and the rate of NP was62.79%in the 43 preparations,and the detection rate of both was 51.16%.NPEOs and NP were detected in all formulations,in which the detection rate was high in EW and EC but low in SC.Detection rate of NPEOs and NP in compound preparations was higher than that in single preparations.The mean and median levels of NPEOs and NP detected in the four formulations were in descending order:EC>EW>ME>SC.The highest contents of NPEOs and NP were found in EC as 6.83%and 8.41%,respectively.There are more NPEOs in EC formulations than NP while in EW,the levels were similar.(3)Migration contrubition of outer packaging:At the beginning of experiment,dissolution migration of NPEOs was easier than NP as the migration amounts of NPEOs and NP in 2h were 0.16-49.34 and 0.19-18.05μg/cm~2,respectively.Migration of NPEOs and NP was similar in 15d and becoming stable as the migration were 46.64%～100.82%and 46.89%～102.03%of the values in 30d samples.Contribution rate of NP in outer packaging plastic was high to 2.568%while the maximum contribution rate of NPEOs was 0.241%.The contribution rate of NP in 30d was 1.66～107.51 times to NPEOs and the contribution of NP in plastic bags was larger than bottles.(4)Adsorption in soil:Adsorption and desorption experiments were carried out with NPEO10 and NP which were mainly used in pesticide preparations.Process of the adsorption of NPEO10 and NP in soil was divided into two stages:fast reaction and slow reaction.Adsorption equilibrium was reached at 240min while the adsorption rates of NPEO10 and NP were 21.44%and 14.58%.Adsorption isotherm tests showed that adsorption of NPEO10 and NP in soil reached adsorption saturation as the adsorption rates were 29.79%and 23.16%when the initial addition amount was 120μg/g.The isotherm adsorption test of NPEO10 and NP from preparation showed that adsorption amount of NP increased with the increase of initial concentration.When adsorption capacity reached the largest,the adsorption rates of NP were 7.39%and 22.35%and the adsorption rate of NPEO10 was 37.04%and 6.25%.(5)Conditions and results of desorption:NPEO10 and NP adsorbed in soil can be desorbed in both acetic acid and phosphate buffer solutions.The maximum desorption rates of NPEO10 and NP in acetate buffer solution and phosphate buffer solution were 17.06%,32.74%and 10.20%,26.40%,respectively.Adsorption soil samples of NPEO10 and NP from preparations have higher desorption rates in the solution of p H=8.In the desorption test of EC sample(A18),the maximum desorption rates of NPEO10 and NP were 18.24%and 23.24%,respectively. |
