A comprehensive procedure to develop water quality index: A case study to the Huong river in Thua Thien Hue province, Central Vietnam.

This work proposed a novel procedure of Water Quality Index (WQI) development that could be used for practical applications on a local or regional scale, based on available monitoring data. Principal component analysis (PCA) was applied to the monthly data of 11 water quality parameters (pH, conductivity (EC), total suspended solid (TSS), dissolved oxygen (DO), five -day biological oxygen demand (BOD), chemical oxygen demand (COD), ammonia (N-NH4), nitrate (N-NO3), phosphate (P-PO4), total coliform, and total dissolved iron monitored at 11 sites at Huong river in the years 2014-2016. From the PCA, the three extracted principal components explained 67% of the total variance of original variables.

Assessment of pesticide use and pesticide residues in vegetables from two provinces in Central Vietnam.

Pesticide residue in food, especially in vegetables, is one of the important parameters to assess food safety. This study evaluates the pesticide use in vegetables from two provinces in Central Vietnamand and present data on pesticides detected in vegetables sampled from the sites. The potential health risk associated with the contamination of four commonly used pesticides in different vegetables is also discussed.

Simultaneous Determination of Hydrochlorothiazide and Losartan Potassium in Pharmaceutical Product by UV-Vis Spectrophotometric Method with Kalman Filter Algorithm.

In this paper, hydrochlorothiazide (HCT) and losartan potassium (LSP) in tablets are simultaneously determined with UV-Vis spectrophotometry and chemometrics without separation. The spectra of standard and sample solutions were recorded in the wavelength from 220 to 300 nm at 1.0 nm intervals.

Dissipation of the pesticides fipronil, cypermethrin, and tebuconazole in vegetables: A case study in Thua Thien-Hue province, Central Vietnam.

This study was designed to understand the dissipation of fipronil, cypermethrin, and tebuconazole in green onions and mustard greens grown in Central Vietnam. A field trial on 400 m was implemented for two months with three different cropping regimes (natural plot-fully exposed to natural conditions; bed plot-fenced in by plastic sheets with an open roof; and protected plot-fully covered by plastic sheets) for each vegetable. A first-order kinetic model was successfully employed to interpret the dissipation data of each studied pesticide.

Determination of Chromium in Natural Water by Adsorptive Stripping Voltammetry Using Bismuth Film Electrode.

Development of adsorptive stripping voltammetry (AdSV) combined with prepared bismuth film electrode ( BiFE) on glassy carbon disk surface using diethylenetriamine pentaacetic acid (DTPA) as a complexing agent and NO as a catalyst to determine the trace amount of chromium (VI) is demonstrated. According to this method, in the preconcentration step at  = -800 mV, the bismuth film is coated on the surface of glassy carbon electrodes simultaneously with the adsorption of complexes Cr(III)-DTPA. In addition to the influencing factors, the stripping voltammetry performance factors such as deposition potential, deposition time, equilibration time, cleaning potential, cleaning time, and technical parameters of differential pulse and square wave voltammetries have been investigated, and the influence of Cr(III), Co(II), Ni(II), Ca(II), Fe(III), SO , Cl, and Triton X has also been investigated.

Multi-residue analytical method for trace detection of new-generation pesticides in vegetables using gas chromatography-tandem mass spectrometry.

A GC-MS/MS method with low solvent consumption and easy operation was developed to simultaneously determine ten new-generation pesticides, namely fenobucarb, acetochlor, pretilachlor, fipronil, trifloxystrobin, fluazifop-p-butyl, isoprothiolane, tebuconazole, cypermethrin and difenoconazole in leafy vegetables. Influences from ultrasonic sample extraction and the clean-up steps to reduce matrix effects were investigated. Under suitable conditions, good linearity (deviation of back calculated concentration from true concentration lower than 20%) was achieved for all studied pesticides; the method detection limits (MDLs) ranged from 1.

Voltammetry Determination of Pb(II), Cd(II), and Zn(II) at Bismuth Film Electrode Combined with 8-Hydroxyquinoline as a Complexing Agent.

A novel method was developed for the simultaneous determination of Pb(II), Cd(II), and Zn(II) based on the cathodic stripping response at a bismuth film electrode associated with oxine as a chelating agent. The developed method provided a high and sharp electrochemical response compared with the method without oxine. A linear response of peak currents was observed for Pb(II), Cd(II), and Zn(II) concentration in the range from 2 ppb to 110 ppb.

Effects of nutrient supply and nutrient ratio on diversity-productivity relationships of phytoplankton in the Cau Hai lagoon, Vietnam.

Diversity and productivity of primary producers are known to be influenced simultaneously by resource availability and resource ratio, but the relative importance of these two factors differed among studies and so far only entire phytoplankton communities were investigated which might ignore specific nutrient requirements and stoichiometric plasticity of different functional groups. We measured nutrient availability (DIN, total N [TN], total P [TP]), nutrient imbalance (TN:TP, DIN:TP, N:P), species richness, and abundance of the whole phytoplankton community, as well as those specific for cyanobacteria, diatoms, and dinoflagellates in Cau Hai lagoon in Vietnam. We determined the correlation among these variables, using structural equation modeling.

Occurrence of organochlorine pesticides and polychlorinated biphenyls in sediment and fish in Cau Hai lagoon of Central Vietnam: Human health risk assessment.

This is the first study on polychlorinated biphenyls (PCBs) in fish from the Cau Hai lagoon, a part of the largest coastal lagoon in Southeast Asia. Seven selected PCB congeners and organochlorine pesticides in sediments and edible fish tissues were quantified by GC-MS. The sum of ICES-7 PCB and DDTs concentrations in fish species consumed regularly and of economic value were in ranges 26-43 ng g lw and 182-277 ng g lw, respectively.

Metals and arsenic in sediment and fish from Cau Hai lagoon in Vietnam: Ecological and human health risks.

Concentrations of Al, As, Bi, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, U, V and Zn were quantified in surface sediments collected from 13 different sampling sites from Cau Hai lagoon in Central Vietnam, and in 8 wild and farmed-fishes involving both pelagic and benthic species. Multivariate analysis shows that these trace elements are mainly associated with lithogenic matter, and are most likely the result of alteration and erosion processes in the lagoon. Enrichment factors and geo-accumulation indices reveal substantial sediment enrichments for both As and Bi with respect to the mean composition in the upper continental crust.

Metal speciation in sediment and bioaccumulation in Meretrix lyrata in the Tien Estuary in Vietnam.

The concentrations of seven toxic metals (cadmium (Cd), nickel (Ni), chromium (Cr), arsenic (As), lead (Pb), copper (Cu), and zinc (Zn)) were determined in sediments and the soft tissues of a bivalve species (Meretrix lyrata) collected from the Tien Estuary in Tien Giang Province, South Vietnam. The total metal concentrations in sediments (mg/kg dry weight) increased as Cd (0.06) < Cu (5.

A new fluorescent chemosensor for Hg2+ in aqueous solution.

We prepared an aminothiourea-derived Schiff base (DA) as a fluorescent chemosensor for Hg(2+) ions. Addition of 1 equiv of Hg(2+) ions to the aqueous solution of DA gave rise to an obvious fluorescence enhancement and the subsequent addition of more Hg(2+) induced gradual fluorescence quenching. Other competing ions, including Pb(2+), Cd(2+), Cr(3+), Zn(2+), Fe(2+), Co(3+), Ni(2+), Ca(2+), Mg(2+), K(+) and Na(+) , did not induce any distinct fluorescence changes, indicating that DA can selectively detect Hg(2+) ions in aqueous solution.