Inorganic disinfection-by-products

Hautman DP, Bolyard M. 1992b. Using ion chromatography to analyze inorganic disinfection by-products. J Am Waterworks Assoc 84(ll) 88-93. 

Pfaff JD, Brockhoff CA. 1990. Determining inorganic disinfection by-products by ion chromatography. 

In an effort to protect the public from potentially hazardous microorganisms, drinking water supplies are routinely disinfected with a variety of treatment regimes. This entry describes some ion chromatography (IC) methods for the determination of inorganic disinfection by-products such as bromate, chlorite, and chlorate. 

FORMATION, TOXICITY, AND REGULATION OF INORGANIC DISINFECTION BY-PRODUCTS IN DRINKING WATER... 

Modern IC is faster, more convenient, and has a greater separating ability than classical wet methods. The IC methods for determination of inorganic disinfection by-products can be divided into three groups. All of them are based on IC separation, but their detection methods are different. The first one, which is the most popular, uses conductivity detection the second is based on UV/Vis detection afto- postcolumn derivatization and the third is based on mass spectrometric detection. 

Initially, application of IC for the analysis of inorganic disinfection by-products using conductivity detection was based on low-capacity ion exchangers. Therefore, injection volume and ionic strength of the sample were strictly limited to avoid column overloading. Also, the removal of interfering ions, such as chloride and sulfate, was necessary. Unfortunately, these methods are not well suited for routine analysis at levels below 1 jxg/L because of the high cost of sample pretreatment, as well as the time spent on preconcentration and cleanup steps. 

In 1993, the USEPA published Method 300.0—the first USEPA method widely accepted as the standard for common inorganic anions.Soon, this method was updated to include part B for the determination of bromate and other inorganic disinfection by-products using a modem high-capacity anion exchange column with carbonate/ bicarbonate eluent. 

The determination of traces of inorganic disinfection by-products (IDBPs) in drinking water samples needs improved lower limit of detection. In order to achieve this, a new electrochemically regenerating continuously operating suppressor (DS-Plus suppressor. Model 335 suppressor module. Alltech Associates (Deer-field, IL)) has been tested and was foimd well applicable by Bose et al. [96]. 

Determination of Inorganic Oxyhalide Disinfection By-products in Drinking Water using Ion Chromatography with the Addition of a Postcolumn Reagent for Trace Bromate Analysis... 

Chlorine dioxide is an unstable gas that rapidly decomposes in air. In water, chlorine dioxide is a strong oxidizer 50-70% of the chlorine dioxide that reacts with organic and inorganic compounds will immediately appear as chlorite (CIO2 ) and chloride (Cl ) ions. Chlorine dioxide does not form trihalo-methanes as disinfection by-products (DBFs). However, chlorine dioxide does result in the formation of... 

Chlorine is applied as chlorine gas, powdered calcium hypochlorite (Ca(OCl)2), or liquid sodium hypochlorite (NaOCl bleach). Chlorine reacts with the organic (natural organic matter, NOM) or inorganic (bromide ion, Br ) precursors in the water to form chlorine disinfection by-products (CBPs), including trihalomethanes (THMs), haloacetic acids (HAAs), haloacetonitriles (HANs), haloketones, chloral hydrate, and chloropicrin. Humic and fulvic acids are the predominant NOMs. When bromine exists, the chlorine oxidizes it to hypobromous acid/ hypobromite ion (HOBr/OBr ) to form bromo THMs (bromodichloromethane, BDCM, and di-bromochloromethane, DBCM), HAAs, and HANs. 

Determination of inorganic oxyhalide disinfection by-products in drinking water using 1C with the addition of a postcolumn reagent for trace bromate analysis... 

Disinfection agents, such as chlorine and chloramine, should be analyzed immediately. Addition of a quenching agent is required for disinfection by-products analysis. For inorganic disinfection... 

In this connection, many drinking water utilities are changing their primary disinfectants from chlorine to alternative disinfectants, such as ozone, chlorine dioxide, and chloroamines, which reduce regulated trihalomethanes and some organochlorine compound levels but, at the same time, often increase levels of other potentially toxicologi-cally important compounds, such as inorganic oxyhalide by-products (bromate, chlorite, and chlorate). Some of them have been classified as probable human carcinogens. 

Bromate is a disinfection by-product that is produced from the ozonation of source water that contains naturally occurring bromide, whereas chlorite and chlorate are produced as a result of using chlorine dioxide as a disinfectant. Recently, bromate has become the most important inorganic oxyhalide by-product, and its concentration in drinking water has to be controUed. Another chaUenge is seawater, which represents a vay difficult matrix for the analysis of trace ionic constituents, because chloride, sulfate, and sodium are the primary ions and they are presort at extremely high concentrations. " ... 

AU IC methods used for bromate, chlorite, and chlorate analyses have some advantages and disadvantages. Nevertheless, at present IC is the only accepted standard method for the analysis of inorganic oxyhalide disinfection by-products. The choice of the most convenient and the best method for the determination of specific oxyhahdes depends on many factors, such as expected concentration of analyte, sample matrix, limit of determination obtainable by the method used, and its availability. 

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