| Optimization on the determination of bromide in water has important meaningfor economy, environment and scientific research. With the development of analyticalinstruments, the determination methods of bromide are also increasingly enriched andexpanded. But every method has its own drawback and the surveys both at home andabroad are restricted to a single measurement method, have not optimized andevaluated the various methods systematically, then formed a uniform selectionstandard. Therefore, the paper first optimizes four conventional methods, includingPhenol Red Spectrophotometric method, Ion Selective Electrode method, IonChromatography method and Iodometric method. Then, the study values thesemethods from different perspective, such as the linear relation, sensitivity,anti-interference ability, precision, accuracy, advantages, disadvantages and adaptivesystem. This research can provide useful data for selecting the correct method and isalso of great importance to the resources utilization, the control of bromide infreshwater and project research of recycling. The main contents are as following:（1） A new approach for diminishing interference of chloride is proposed and theoptimum determination condition of Phenol Red Spectrophotometric method isdetermined. The maximum absorption wavelength is at595nm, the pH of solutionranges from4.6to4.7, the volume of phenol red (0.24g L-1) is0.40mL, the volumeof chloramine T (2g L-1) and sodium hyposulfite (25g L-1) are both1.00mL, theoxidation reaction time is2.0min, and the color reaction time is15.0min. Bromidecan be determined in the range from0.2to1.2mg L-1, the linear regression equationis that y=0.1804x-0.0011, the correlation coefficient is0.9993, the detection limit is0.14mg L-1, the relative standard deviation （n=6） is0.79％, the relative error is lessthan0.9％, and the average recovery ranges from97%to103%. There are nosignificant chemical interferences.（2）1mol L-1potassium nitrate solution as ionic strength adjustment buffer，themeasure of bromide in water by ion selectivity electrode is improved and the best analysis condition is defined. The volume ratio between ionic strength adjustmentbuffer and the sample solution is1:4, the pH of solution ranges from3.0to10.0,consistent temperature, mixing with uniform velocity, and the response time is0.51.0min. Bromide can be determined in the range from0.0004to7.9904mg L-1,the linear regression equation is that y=54.9317x-153.0282, the correlation coefficientis0.9988, the detection limit is3.01×10-5mg L-1, the relative standard deviation （n=6）is2.18％, the relative error is less than4％, and the average recovery ranges from95%to109%. High level of chloride has significant interference on the determination.（3） Dealing with IonPac AS11-HC separation column and IonPac AG11-HCguard column, the measure of bromide in freshwater by ion chromatography isimproved and the best analysis condition is defined.18mmol·L-1potassiumhydroxide solution generated by eluent generator is used at a flow rate of1.0mL·min-1, the temperature of conductivity cell is35℃, the column temperature is30℃, and the suppressor current is45mA. The wide linear calibration range of thismethod is achieved, the linear regression equation is that y=0.0199x+0.0002, thecorrelation coefficient is0.9995, the detection limit is0.026mg L-1, the relativestandard deviation （n=6） is2.42％, the relative error is less than4％, and the averagerecovery ranges from98%to102%. There are no significant chemical interferences.（4） The improvements are made on the Iodometric method for bromide inseawater and brines. These improvements include simplification of the preparation ofsodium hypochlorite solution and use of boiling water bath for heater to heat thesample. The best analysis condition is as following: when the volume of samplesolution is25.00milliliters, the volume of sodium hypochlorite （1:1） is5.00mL, themass of boric acid is3.5g, the volume of sodium format solution （20％） is3.00mL,and the volume of starch-iodide indicator （0.5％） is2.00mL. The pH of solution isless than0.6when the iodide is oxidized, the oxidation temperature of bromide is80℃, the decomposition temperature of sodium hypochlorite is100℃, and the timeof constant temperature is5.0min. The relative standard deviation （n=6） of thismethod is1.32％, the relative error is less than3％, and the average recovery rangesfrom97%to105%. There are no significant chemical interferences. （5） The four methods are valued from different perspective and find the properanalysis field of every measure. The Phenol Red Spectrophotometric method issatisfactorily applied to determination of bromide in both freshwater and seawater.The anti-interference ability of the Ion Selective Electrode method is poor and it isavailable for project research with the highest sensitivity. The Ion Chromatographymethod is available for analyzing several anions at the same time in freshwater. TheIodometric method can be used for the examination of bromide in the mineral waterwith high salt concentration or complicated system. All of the methods with suitablesystem can overcome its own limitations, and have a high accuracy and precision. |
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