Preconcentration/separation and determination of mercury using microcrystalline phenolphthalein modified by ethyl violet

A novel method was developed for enrichment and separation of trace mercury using phenolphthalein modified by ethyl violet （EV）. The effects of different parameters, such as stirring time, various metal ions and salts, and the amounts of phenolphthalein, NH4SCN, and EV on the extraction rate of mercury were studied, to select the experimental conditions. Under optimum conditions, mercury can be adsorbed on the surface of microcrystalline phenolphthalein by the intermolecular acdon strength. The possible reaction mechanism for the enrichment of mercury was discussed in detail. Hg（Ⅱ） could be completely separated from Fe（Ⅱ）, Co（Ⅱ）, Ni（Ⅱ）, Mn（Ⅱ）, Cd（Ⅱ）, Cr（Ⅲ）, and Al（Ⅲ） in the solution. The proposed method has been successfully applied to the determination of trace mercury in industrial wastewater with the recoveries above 99%. The relative standard deviation for five replicate determinations of 0.04 μg·mL^-1 of Hg（Ⅱ） was found to be 1.4%, 1.1%, and 1.2%, respectively. The analytical results were very satisfactory.

Recovery Properties of Polysulfone Hollow Fiber Chelating Membrane Modified with Thiourea for Mercury (Ⅱ)

The adsorption isotherms of the polysulfone hollow fiber chelating membrane modified with thionrea as chelating groups for Hg^2＋ were determined. The effects of mobile phase conditions and the operating parameters on removal performance of the chelating membrane for Hg^2＋ were also investigated. The recovery of Hg^2＋ decreased at low pH and the optimum range of pH was from 6 to 7. The feed concentration effected on recovery of Hg^2＋ at the specified loading amount of Hg^2＋. The Hg^2＋ could be removed from different concentration feed solution by chelating membrane. The increase of feed flow rate led to slight decrease of recovery of Hg^2＋ at the specified loading amount of Hg^2＋. The chelating membrane could be operated at height feed flow rate and a large-scale removal of H^2＋ could be realized. With the increase of load amount, Hg^2＋ recovery decreased, but the saturation degree of chelating membrane increased. According to required recovery of H^2＋ and the saturation degree of chelating membrane, the optimum loading amount of Hg^2＋ should be selected in the actual removal of H^2＋.

Mitoxantrone Determination by 1,5-order Differential Stripping Voltammetry

A rapid and sensitive 1.5 order adsorptive stripping voltammetric method fordetendnation of trace mitoxantrone (MXT) is described. The accumulation behavior of MXT on amercury film ndcroelectrode was studied and the possibility of carrying out 1.5 order differentialadsorptive stripping analysis using mercury-coated carbon fiber ndcroelectrode was demonstrated.Optimal conditions for 1.5 order differential voltammetry monitoring are described. The strippingpeak current is linearly proportional to the concentration of MAT in the range of 1.0×10-6 mol/L 1.0×10-9 and detection licit is 1.5×10-10 mol/L. The relative standard deviation (RSD) is 3.0% at5.0×10-8 (n=8). MXT can be detendned directly in biological samples at physiological levelswithout any separation procedure.

Fish from a polluted lake(Lake Chivero,Zimbabwe):a food safety issue of concern

Objectives:A study to determine food safety hazard status of fish products from Lake Chivero was conducted in selected high density suburbs of Harare.Lake water and fish were tested for E.coli O157:H7,total bacterial,fungal counts,mercury(Hg)and aflatoxin B1(AFB1)to determine contamination levels and assessing human health hazard exposure.Materials and Methods:Membrane filtration method was used to determine E.coli O157:H7 viable counts using CHROM agar.Plate count and Potato dextrose agar were used for determination of total viable bacterial and fungal counts.Concentrations of Hg and AFB1 in fish and water were determined by Atomic Absorption Spectrophotometer and High Performance Liquid Chromatography-Mass Spectrometry.A questionnaire survey was conducted on 136 adult fish consumers to determine the fish consumption patterns to assess hazard exposure against international standards.Results:Significant levels of microbial contamination above international standards in both fish and water were recorded.Mean E.coli O157:H7 counts were 106±10(cfu/cm^(2))in fish and 52±14(cfu/100ml)in water.Mean Log10 TBC were 8.98±0.26(cfu/cm^(2))in fish and 9.05±0.05(cfu/ml)in water.Mean Log10 TFC were 4.83±0.02(cfu/cm^(2))in fish and 4.56±0.03(cfu/ml)in water.Hg and AFB1 were 0.018(μg/kg)and 0.025(μg/kg)in fish and 0.008(μg/kg)and 0.005(μg/kg)in water,both with a hazard quotient(HQ)<1 using CODEX STAN 193-1995 of 2015.Conclusion:Fish and water are contaminated with E.coli O157:H7,contain bacterial and fungal loads above international food safety guidance levels.Fish were caught already contaminated with pathogens together with toxigenic Hg and carcinogenic AFB1 although their concentration levels are within international food safety toxicological levels.Levels of Hg and AFB1 in water were almost double that of fish,implying bio-accumulation occurred in fish.Thus,fish consumers are exposed to food safety hazards and are at risk of contracting foodborne illnesses from consuming contaminated fish.