[Combined Effect of Weathered Coal Based Amendments and Soil Water Management on Methylmercury Accumulation in Paddy Soil and Rice Grains].

A pot experiment and field experiment were designed to study the changes in the grain methyl mercury content in paddy soil and rice yield by sowing soil amendments that contained weathered coal, CaCO3, and Na2SeO3 as the main raw materials, combined with water management in a paddy field (80% field capacity after the heading and flowering periods). The results showed that:① In pot experiment, the content of methylmercury in rice rhizosphere soil decreased by 86.6% and the content of methylmercury in the rice grains decreased by 65.2% compared with that of the control. In field experiment, the content of methylmercury in rice rhizosphere soil decreased by 77.4% and the content of methylmercury in rice grains decreased by 60.6% upon adding the amendment+water management compared with that of CK. ② The soil pH increased by more than 0.3 in the pot experiment and 0.2 in the field experiment compared with that of the control. Furthermore, rice yield and plant biomass did not decrease in the two parts of the experiment. It can be inferred that the soil amendment and agronomic regulation measures (water management) used in this study have the advantages of quick effects, convenient use, and remarkable control effects and without secondary pollution. More, they can effectively reduce the risk of rice methylmercury exposure.

Semiautomated Alignment of High-Throughput Metabolite Profiles with Chemometric Tools.

The rapid increase in the use of metabolite profiling/fingerprinting techniques to resolve complicated issues in metabolomics has stimulated demand for data processing techniques, such as alignment, to extract detailed information. In this study, a new and automated method was developed to correct the retention time shift of high-dimensional and high-throughput data sets. Information from the target chromatographic profiles was used to determine the standard profile as a reference for alignment. A novel, piecewise data partition strategy was applied for the determination of the target components in the standard profile as markers for alignment. An automated target search (ATS) method was proposed to find the exact retention times of the selected targets in other profiles for alignment. The linear interpolation technique (LIT) was employed to align the profiles prior to pattern recognition, comprehensive comparison analysis, and other data processing steps. In total, 94 metabolite profiles of ginseng were studied, including the most volatile secondary metabolites. The method used in this article could be an essential step in the extraction of information from high-throughput data acquired in the study of systems biology, metabolomics, and biomarker discovery.

[Influence of Arsenate and Phenanthrene on Carbon-groups of Pteris vittata L. Roots].

To ascertain absorption of arsenate and phenanthrene as well as their influence on carbon groups in excised roots of Pteris vittata L., the chemical structure of the carbon groups in excised roots was characterized by solid state13C-Nuclear Magnetic Resonance (13C-NMR). The results showed that the excised roots could effectively absorb As and PHE without transpiration, and PHE promoted As accumulation in the roots. Similarly, arsenate increased the adsorption of PHE by the excised roots, the concentration of PHE was increased by 15%-53% compared with CK. The carbon groups of the excised roots were dominated by O-alkyl C, the percentage of carboxyl C was the lowest, mainly composed of carboxylic acids, esters and amides. With the addition of As and PHE, the percentage of carboxyl C increased significantly. The more stable and complex aromatic organic matter was formed to improve the resistance and adaptability in excised roots of Pteris vittata L. under As and PHE stress.

The retention behaviour of amino acids in hydrophilic interaction liquid chromatography on zwitterionic stationary phases.

The retention behaviour of amino acids was studied in hydrophilic LC on zwitterionic stationary phases. Evaluation of the influences of acetonitrile/water content, ammonium acetate (NH4Ac) concentration and mobile phase pH values was performed. Fourteen amino acids were tested and they were all retained to varying extents, with poorer retention in high water content eluents. The linear relationship between the logarithm of retention factor and log(water content) indicated that adsorption dominated or at least was partly involved in the separation mechanism. Electrostatic and hydrophilic interactions also contributed to the retention of these amino acids under different separation conditions with various mobile phase pH values and NH4Ac concentrations. Thus, the overall retention mechanism could be explained as a combination of adsorption, electrostatic and hydrophilic interactions. The magnitude and contribution of each mechanism is dependent on the nature of the analyte and the separation conditions applied.

One- and comprehensive two-dimensional high-performance liquid chromatography analysis of alkylphenol polyethoxylates.

High-performance liquid chromatography (HPLC) analysis of alkylphenol polyethoxylates (APnEOs) in one-dimensional (1-D) mode usually separates either the ethoxy or alkyl moiety distribution and requires different modes for adequate resolution. Simultaneous complete separation of variable ethoxymer chain lengths and variable alkyl end groups using 1-D-HPLC has not been reported and suggests that multidimensional (MDLC) or comprehensive two-dimensional liquid chromatography (LC×LC) might offer a suitable separation approach for this goal. This study compares different separation modes--normal phase LC (NPLC), reversed-phase LC (RPLC) and hydrophilic interaction chromatography (HILIC)--in terms of separation for alkyl and ethoxy distributions. RPLC provided adequate separation of octyl and nonyl APnEOs using an isocratic elution program and was selected as second dimension ((2)D) for LC×LC. NPLC offered better resolution than HILIC; however, non-polar NPLC solvent immiscibility with RPLC mobile phases leads to HILIC being chosen as first dimension ((1)D). The HILIC×RPLC system was evaluated by analysis of four APnEO mixtures. Complete simultaneous separation of APnEOs into individual oligomers, with each alkyl end group resolved, demonstrated the capability of the LC×LC method. Different descriptors and metrics for assessing system orthogonality were investigated to evaluate HILIC×RPLC performance. A relatively high dimensionality of 1.76 was demonstrated.

Liquid chromatography fractionation with gas chromatography/mass spectrometry and preparative gas chromatography-nuclear magnetic resonance analysis of selected nonylphenol polyethoxylates.

Commercial nonylphenol polyethoxylates, designated as NPnEOs, where n is the number of ethoxy groups, comprise a range of ethoxylate groups. According to the starting material nonylphenol, they may also be composed of a complex mix of isomeric nonyl substituents. In order to study more fully the heterogeneity arising from both the ethoxylate and nonyl groups, a mixture of NPnEOs is first fractionated by normal phase liquid chromatography (NPLC) into separate fractions comprising individual ethoxymers, n. Preparative collection of each early elution ethoxymer fraction allows further separation of different isomeric nonyl group components by using analytical gas chromatography/mass spectrometry (GC/MS). The nonyl isomers are not resolved in the NPLC method. The distribution of the isomeric nonyl side chain of different ethoxymers bears close resemblance with each other, and also with the original nonylphenol starting material, although separation efficiency of the nonyl isomers for each ethoxymer decreases with increasing ethoxymer number. Mass spectrometry of the separated isomers display close similarity for presumed equivalent isomers in each fraction, based on elution order of the nonyl isomers. This suggests that each corresponding peak has the same isomer structure. Mass spectra are interpreted based on branching within the nonyl side chain. Preparative GC coupled with MS and nuclear magnetic resonance spectroscopy elucidated the molecular structure of one of the resolved isomers as 4-(1,3-dimethyl-1-propyl-butyl)-phenol diethoxylate.

Comparative qualitative analysis of nonylphenol isomers by gas chromatography-mass spectrometry combined with chemometric resolution.

The relationship between nonylphenol (NP) isomers' structures and their estrogenic potencies has been evaluated previously. However, due to their similarities in both chemical and physical properties, complete separation and identification remain strikingly difficult. In the present study, gas chromatography-mass spectrometry (GC-MS) is employed to separate commercial NP isomers. Both extracted ion chromatograms (EIC) based on selected ions known to be definitive for the suite of isomers, and the heuristic evolving latent projection (HELP) chemometric resolution method have been applied for the analysis and identification of the NP isomers. This method corrected the wrong identification of one isomer which was suspected based on the EIC data, and also was able to be applied for the determination of an additional isomer with low abundance. Overall, 15 NP isomers have been proposed by the HELP interpretation method. Pure component chromatograms and mass spectra have been extracted with the aid of chemometric resolution. The applicability of the commercial deconvolution software package automated mass spectral deconvolution and identification system (AMDIS) has also been tested against the HELP method for comparative presentation of pure component mass spectra.