Objective　To simplify the National Standard Method for determination of sulfate in drinking water.Methods　A series of improved experiments on barium chromate spectrophotometry without heating and the experiments of precision and accuracy,as well as comparison of experimental data between the improved method and the National Standard Method were carried out.Results　 The detection limit,detectable range,recovery rate,coefficient of variation of the improved method were 5.0 mg/L,5～200 mg/L,97.3%～101.8% ,1.09%～4.18% respectively,which revealed no significant differences compared with those of the National Standard Method (P＞0.05).Conclusion　The improved method for determination of sulfate in drinking water was simple,rapid and presented high sensitivity,accurate and reliable results and good practicality.

Turbidities of water samples were determined by Hach 2100-N scattering turbidimeter in this assay.This method showed a good linearship at range of 0～100 NTU with r=0.9999 for water samples,and also revealed good precision compared with the transmissometry.The data obtained by this method showed no significant differences in the standard series at the range of 0～6.5 NTU and the water samples at the range of 0～5 NTU.

The conditions of color-reaction of boric acid with 1-(2-hydroxy-3-methoxybenzylidence-amino)-8-hydroxynaphalene-3-6-disulfonic acid in buffer medium of ethamine at pH 6.5 were studied in the assy.The maximum absorption wavelength of this coordination compound was 420 nm.The coordination reaction showed a good linear relationship at the concentrations of boric acid of 0.4～0.6 mg/L.The detection limit and molar absorptivity (ε) was 0.08 mg/L and 4.6×104 L/(mol·cm) respectively.This method presented perfect selectivity under the existence of EDTA solution,had been successfully applied in the determination of boric acid in natural mineral water for drinking.

In recent years,the potential impairments of organic pollutants in water on human health and the removal of organic pollutants in drinking water have become a worldwide concern.Some subjects from the impairments of the genotoxicity of organic pollutants to the prevention of water pollution,had been assessed widely by researchers and schoolars.The results showed that,the impairments of the organic pollutants in water on human health were preventable,and its preventive methods presented a good prospect for extensive use.

To establish a spectrophotometric method for detecting selenium in drinking water,some subjects,such as the features of absorption spectrum of the reacting product of selenium and diaminonaphthalene,disturbance of other coexisting ions,detection range,detection limit,precision and accuracy were studied.The results showed that:the maximum absorption wavelength of the reacting product of Se4+and 2,3-diaminonaphthalene was 377 nm,the detection limit,molar absorptivity (ε377) and linear range of this method was 0.018 μg/50 ml,2.7×104 L/(mol·cm)and 0.2～10 μg/50ml respectively.The regressive equation was A＝0.077C＋0.014 with a correlation coefficient r value of 0.9999.The relative standard deviation (RSD) and recovery rate were ＜54.7% and 96.5%～106% respectively.This method was simple,sensitive and accurate,could meet the requirement of the routine monitoring of selenium in drinking water.

Objective　To explore the effects of chemical reaction of aluminum salt in water solution on developmental toxicity.Methods　Inhibiting actions on embryo growth and development,and organ morphogenetic differentiation in rats induced by newly prepared and 11.5-month stored aluminum sulfate solution were observed and compared using whole embryo culture method in rats.Results　Both of the two observed solutions showed a certain embryo toxicity and teratogenicity.The toxicity of stored solution decreased significantly compared with that of newly prepared solution.At the same concentration of aluminum,the total Brown's morphogenetic score reflecting the every index of embryo growth and development and organ morphogenetic differentiation,the incidence rates of terata and the number of dead embryos were significant lower in rats exposed to stored solution compared with those exposed to newly prepared solution,especially the morbidity of embryos.Conclusion　The complexation reaction between aluminum ions (Al3+) and water molecules in stored aluminum sulfate solution resulted in the changes of existing state of Al3+ and its decreasing developmental toxicity to rats.

The levels of selenium in hair were determined by hydride generation atomic absorption spectropho-tometryin this assay. The working conditions of the determination were controlled as follows,wavelength: 196.00 nm,working current of lamp:6 mA,wide of filtered spectrum:4.0 A, flow rate of gaseous argon: 120 ml/min. The averagecontents of selenium in hair samples reached 0. 0498±0. 031 mg/kg. The detection limit and coefficient of variation were0. 5 ng/ml and 5.8％ respectively. The recovery rates were 92.0％～ 104. 0％ with an average of 99. 5％. This methodshowed advantages ,such as simple operation,rapid,low cost and high accuracy. The obtained data were reliable.

Objective To explore the application of naphthyl ethylenediamine method for determination of nitrite in cosmetics. Methods The concentrations of nitrite in cosmetics were determined by hydrochloric acid-naphthylethylenediamine method. The experiments on working curve, precision and recovery rate were carried out. Results In the range of 0～12. 5 μg/50 ml nitrite,the correlation coefficient r value,recovery rate and relative standard deviation was 0. 9996,97. 7％～100. 2％ and 2.35％～4. 51％ respectively. Conclusion This method for determination of nitrite by hydrochloric acid and naphthyl ethylenediamine was simple,quick and accurate.

To determine fluoride in toothpaste samples by ion chromatography,the solution of NaHCO3 and the solution of Na2B4O7-NaOH were selected as eluents respectively to optimize chromatographic detection conditions. Either the 0. 45～1.0 mmol/L NaHCO3 solution or the 5.0～20. 0 mmol/L NaB4O7-1. 0～2.0 mmol/L NaOH solution as eluents could effectively separate the chromatographic peak of fluoride in toothpaste samples from acetate and formate and accurately quantify the contents of fluoride in toothpaste samples. The recovery rates,precision(relative standard deviation) and detection limit were 92.5％～100. 2％ ,＜0. 6％ and 0. 208 mg/kg respectively. The data obtained by ion chromatography using NaHCO3 solution as eluent more approached to that by selective-fluoride-ion-electrode.

Objective To study the mechanism of toxicity of hexane. Methods SD rats inhaled 15 g/ma n-hexane statically for 8 hours. Results The levels of GSH in whole blood of rats declined significantly (t-test,P＜0. 01). The levels of MDA in serum of rats revealed increasing trend but without statistical significance (t-test,P＞0. 05). The activities of SOD and GSH-Px in liver of rats decreased significantly (t-test,P＜0.01). Conclusion n-Hexane could induce or enhance the reaction of oxygen free radical in organism,and result in damages of lipid peroxidation,which might be one of the mechanisms of the toxicity of alkane.