[Simultaneous determination of 6 neonicotinoid residues in soil using DLLME-HPLC and UV].

A simple, cheap and rugged method was developed for simultaneous deter mination of 6 neonicotinoid residues in soil, including imidacloprid, acetamiprid, thiamethoxam, thiacloprid, clothianidin and nitenpyram. The soil sample was produced by dispersive liquid-liquid micro-extraction (DLLME) after extracted by the mixed solution of acetonitrile and CH2Cl2 (2:1, phi). The analytes were separated by HPLC with Alltima C18 column (4.6 mm x 250 mm, 5 microm) and detected by PDA at 260 nm. External standard method was used for quantification. The results showed that good linearity was obtained with correlation coefficients between 0.9982 and 0.9999 in the range of 0.5-200 microg x L(-1). The limits of detection (LODs) were in the range between 0.0005 and 0.003 microg x mL(-1) (S/N = 3). The method was validated with five soil samples spiked at three fortification levels (0.05, 0.1, 1.0 mg x kg(-1)) and recoveries were in the range of 55.3%-95.6% with RSD of 1.4%-7.0%. The effect of clean-up was evaluated by UV spectra and demonstrated that the method established is effective. In conclusion, this method is competent for the simultaneous analysis of 6 neonicotinoid residues in soil.

[Determination of soil quality from Chinese apple plant area by NIR spectroscopy].

In the present work, 111 soil samples from 11 different Chinese apple plant areas were used to take the diffuse reflection spectra from 12 500 to 4 000 cm(-1) by FT-NIR. The models of organic substance and pH value of soil samples were built by using partial least square regression (PLSR). The calibration model gave the correlation coefficients of 0.818 and 0.836 for the two values respectively, with the root mean square error of prediction (RMSEP) of 0.377 (%) and 0.251, respectively. In order to improve the robustness and performance of calibration, several spectra preprocessing methods were employed, including standard normalized variate (SNV), multiplicative scatter correction (MSC) and direct orthogonal signal correction (DOSC). Finally, the performance of DOSC was found to be the best for organic substance and pH value with RMSEP of 0.258 (%) an 0.248, respectively. The results showed that the technology of NIR spectroscopy was useful to nondestructive determination of the organic substance and pH value of soil. These research findings provide theoretic base for fertilization and pomiculture by means of NIR diffuse reflection.