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Shanghai, China

Zhang H.,Shanghai JiaoTong University | Zhang H.,Key Laboratory of Urban Agriculture | Zhao Z.,Key Laboratory of Urban Agriculture | Yi X.,Technical Center for Food | And 2 more authors.
Plant, Soil and Environment | Year: 2012

Dissolved organic nitrogen (DON) has high bioavailability and is an important source of soil nutrients. In order to determine the concentrations and the composition of DON in different depths (0-30 cm), and provide a theoretical basis for further deep research into the paddy soil nitrogen supply, experiments based on the lysimeter method were carried out to investigate the effect of fertilization on composition and spatial distribution of DON in paddy soil. Paddy soil was treated under chemical fertilization treatment (CT) and mixed fertilization treatment (MT). With methods of PCR-DGGE and HPLC-MS, the results of the experiments suggested that the samples in 10-20 cm and 20-30 cm under MT had significantly higher bacterial diversity than those under CT except in 0-10 cm. DON had a high percentage (63.1-79.9%) in N tot of soil solution. The results of the correlation analysis revealed that DON had a significant positive correlation with organic matter content, Shannon-Wiener diversity index (H') and a significant negative correlation with pH. The possible results of HPLC-MS identification of DON from paddy soil solution were that (a) 3-(4-thiazolyl)-l-alanine; (b) 2-phenylbenzimidazole-5-sulfonic acid; (c) 4-(2, 4-difluorophenyl)-3-nitrobenzene carbaldehyde; (d) fendizoic acid.

Yi X.,Technical Center for Food | Guo D.,Technical Center for Food | Deng X.,Technical Center for Food | Li B.,Technical Center for Food | And 2 more authors.
Journal of AOAC International | Year: 2011

A novel, reliable, and robust analytical method using headspace and multidimensional GC coupled to MS was successfully developed for determining the methanol content in cosmetics. The methanol was quantitatively analyzed and confrmed by heart-cutting multidimensional GC and mass selective detection in full scan mode. The average recovery was 99.8% with an RSD of 4.3%; the LOQ was 5 mg/kg. The proposed method showed good accuracy and precision while minimizing erroneous results due to false positives compared with conventional single-column GC analysis.

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