亲水作用色谱柱与阳离子交换树脂柱结合分离无机离子(英文)

A combination of hydrophilic interaction chromatographic(HILIC) column and a weakly acidic cation-exchange resin(WCX) column was used for simultaneous separation of inorganic anions and cations by ion chromatography(IC).Firstly,the capability of HILIC column for the separation of analyte ions was evaluated under acidic eluent conditions.The columns used were SeQuant ZIC-HILIC(ZIC-HILIC) with a sulfobetaine-zwitterion stationary phase(ZIC-HILIC) and Acclaim HILIC-10 with a diol stationary phase(HILIC-10).When using tartaric acid as the eluent,the HILIC columns indicated strong retentions for anions,based on ion-pair interaction.Especially,HILIC-10 could strongly retain anions compared with ZIC-HILIC.The selectivity for analyte anions of HILIC-10 with 5 mmol/L tartaric acid eluent was in the order of I-> NO-3 > Br-> Cl-> H2PO-4.However,since HILIC-10 could not separate analyte cations,a WCX column(TSKgel Super IC-A/C) was connected after the HILIC column in series.The combination column system of HILIC and WCX columns could successfully separate ten ions(Na+,NH+4,K+,Mg2+,Ca2+,H2PO-4,Cl-,Br-,NO-3 and I-) with elution of 4 mmol/L tartaric acid plus 8 mmol/L 18-crown-6.The relative standard deviations(RSDs) of analyte ions by the system were in the ranges of 0.02%-0.05% in retention times and 0.18%-5.3% in peak areas through three-time successive injections.The limits of detection at signal-to-noise ratio of 3 were 0.24-0.30 μmol/L for the cations and 0.31-1.2 μmol/L for the anions.This system was applied for the simultaneous determination of the cations and the anions in a vegetable juice sample with satisfactory results.

Benefitting from Geoinformatics: Estimating Floristic Diversity of Warwan Valley in Northwestern Himalaya,India

The Himalaya harbor rich floristic diversity which is of immense scientific interest and socio-economic importance.In this study, floristic diversity of a remote alpine valley has been studied based on information extracted from remotely sensed satellite data along with field surveys undertaken during 2008-2014.Analysis of vegetation information from satellite data revealed that ~75% of the area is covered with natural vegetation which comprises lush green coniferous forests, alpine pastures and alpine scrub lands.With inputs from vegetation information extracted from satellite data, comprehensive field surveys were planned to document the floristic diversity of the region.Analysis of species composition showed a total of 285 plant species,belonging to 191 genera in 60 families.Of these, 250 species are herbs, 14 shrubs, 2 sub-shrubs and 19 trees.The dicotyledons are represented by 240 species, monocotyledons 30, gymnosperms 04, andpteriodophytes 11 species.Asteraceae is the largest family with 35 species.During the present study, 5species（Corydalis cashmeriana, Hippophae rhamnoides, Primula minutissima, Saussurea sacra and Inula orientalis） have been recorded for the first time from this Himalayan region.The study demonstrates the benefits of geo-informatics in floristic studies, particularly the robustness of remotely sensed data in identifying areas with potentially high species richness, which would be otherwise difficult in a complex mountainous terrain using traditional floristic surveys alone.The present study is expected to provide baseline scientific data for cutting edge studies relating to long term ecological research, bioprospecting, possible impacts of changing climate on vegetation and sustainable use of plant resources in this Himalayan region.

Determination of Pesticide Ethion by Linear Sweep Stripping Voltammetry

The presence of the pesticide ethion was determined using an electroanalytical method, i. e. , linear sweep stripping voltammetry at a hanging mercury drop electrode in the Britton-Robbinson buffer with pH = 8. 36, based on its reduction peak observed at - 690 mV following its alkaline hydrolysis. The experimental parameters, namely, the preconcentration potential, the preconcentration time, and the scan rate were investigated and - 300 mV （vs. Ag/ AgCl）, 270 s, and 100 mV/s were selected as the optimal values, respectively. The linear relationship between the peak current and the concentration was found to be in the range of 0.02-0. 16 mg/L, with a detection limit of 0.0087 mg/L. The proposed method was applied to the determination of ethion in spiked vegetable and fruit samples via a preextraction with anhydrous ethanol.

Determination of Some Trace Metals in Environmental Samples by Flame AAS Following Solid Phase Extraction with Amberlite XAD-2000 Resin after Complexing with 8-Hydroxyquinoline

A procedure for preconcentration of Mn（Ⅱ）, Fe（Ⅱ）, Co（H）, Cu（Ⅱ）, Cd（Ⅱ）, Zn（Ⅱ）, Pb（Ⅱ） and Ni（Ⅱ） based on retention of their complexes with 8-hydroxyquinoline （HQ） on Amberlite XAD-2000 resin in a column was proposed for the analysis of environmental samples by flame AAS. Various parameters such as pH, eluent type, volume, concentration, flow rate and volume of sample solution, and matrix interference effect on the retention of the metal ions were investigated. The optimum pHs for the retention of metal complexes in question were about 6 except for Mn^2＋ for whose value is 8. The loading capacity of the adsorbent for these metals and their recoveries from the resin under the optimum conditions were in the range 6.82-9.26 mg·g^-1 and 95%-101%, respectively. The enrichment factor was calculated as 100 and the limit of detection was in the range 0.3-2.2 μg·L^-1 （n=20, blank＋ 3s）. The proposed enrichment method was applied to tap water, stream water and vegetable samples. The validation of the procedure was carried out by analysis of certified reference material and standard addition. The analytes were determined with a relative standard deviation lower than 6% in all samples.

Observer error in vegetation surveys:a review

Aims Vegetation sampling employing observers is prone to both inter-observer and intra-observer error.Three types of errors are common:(i)overlooking error(i.e.not observing species actually present),(ii)misidentification error(i.e.not correctly identifying species)and(iii)estimation error(i.e.not accurately estimating abundance).I conducted a literature review of 59 articles that provided quantitative estimates or statistical inferences regarding observer error in vegetation studies.Important FindingsAlmost all studies(92%)that tested for a statistically significant effect of observer error found at least one significant comparison.In surveys of species composition,mean pseudoturnover(the percentage of species overlooked by one observer but not another)was 10-30%.Species misidentification rates were on the order of 5-10%.The mean coefficient of variation(CV)among observers in surveys of vegetation cover was often several hundred%for species with low cover,although CVs of 25-50%were more representative of species with mean covers of>50%.A variety of metrics and indices(including commonly used diversity indices)and multivariate data analysis techniques(including ordinations and classifications)were found to be sensitive to observer error.Sources of error commonly include both characteristics of the vegetation(e.g.small size of populations,rarity,morphology,phenology)and attributes of the observers(e.g.mental fatigue,personal biases,differences in experience,physical stress).The use of multiple observers,additional training including active feedback approaches,and continual evaluation and calibration among observers are recommended as strategies to reduce observer error in vegetation surveys.