Persulfate oxidation method

Williams [81,84] found that a high-energy ultraviolet oxidation method gave dissolved organic carbon results for seawater samples that were higher than those obtained by the wet persulfate oxidation method described by Menzel and Vaccaro [46]. Other variations on the method have been published. 

The versions of the persulfate oxidation methods used at present yield results that are lower than those obtained using the dry combustion or photooxidation techniques (Table 11.2). Close agreement between the persulfate and other methods is obtained when the analyses are carried out on freshwater rather than seawater samples. If the persulfate oxidation procedure is to be retained as a method for seawater analysis, serious consideration should be given to abandoning the present batchwise procedure in favour of an automated procedure. 

Organo-Mercury Associations. Experimentally, the mercury measurements in seawater have been divided into two fractions— reactive and total mercury. The reactive fraction represents the amount of mercury measured in pre-acidified raw seawater samples at approximately pH 1. The total mercury measurement is carried out on aliquots of the preacidified seawater samples in which the organic matter has been destroyed by ultraviolet photooxidation (31). This irradiation procedure is as effective as the persulfate oxidation method (32) commonly used to destroy organic matter in seawater. A complete discussion of our photooxidation methodology can be found in Fitzgerald (33). The amount of mercury determined as the difference between the reactive and total mercury measurements represents a very stable organo-mercury association. 

The methods which have been described for measurement of the organic content of water are based on oxidation of organic matter and measurement of the products. Another direct method for determining the organic content of natural waters based on measurement of ultraviolet absorbance of water (Mattson et al., 1974). This method can only be successfully employed when the composition of oi anic matter remains similar over the area sampled and as such may find only limited application. Correlation of results of the ultraviolet absorbance method with those of the persulfate oxidation method for samples of coastal and marsh waters was very poor (Wheeler, 1977). 

Cornell S.E. and Jickells T.D. 1999. Water-soluble organic nitrogen in atmospheric aerosol a comparison of UV and persulfate oxidation methods. Atmos. Environ. 33 833-840. 

Kaplan, L.A. (1992). Comparison of high-temperature and persulfate oxidation methods for determination of dissolved organic carbon in freshwaters. Limnol. Oceanogr., 37(5), 1119-1125. 

Photo-oxidation was seen as a possible route to a total phosphorus method. Again, early work on the method was done by Armstrong et al. [15] and Armstrong and Tibbitts [36]. Grasshoff [37] adapted the method to continuous automatic analysis a variation on this method is considered the standard method for automatic analysis today [18]. Bikbulatov [38], on the other hand, feels that such important phosphorus compounds as ATP and DI are not completely decomposed by ultraviolet irradiation and that persulfate oxidation gives better results. 

Both the persulfate and ultraviolet oxidation methods have much to recommend them. Ultraviolet photo-oxidation methods have an advantage in that they are easily automated. 

Wet chemical oxidation methods, using oxidants such as persulfate, are widely used in oceanographic and limnologic work [46,47]. The main drawbacks of these methods are their manual and cumbersome techniques and incomplete oxidation of some organic compounds [48]. 

Initially, results reported for dry-combustion methods were found to be higher than wet-oxidation methods based on persulfate by factors of 2 or more. This discrepancy has steadily decreased as methodologies have improved. Contamination problems of dry methods have been reduced and the oxidation efficiency of the wet methods has been improved. While the differences between approaches have been discussed [94,95], there is still uncertainty whether the remaining difference between the two techniques is real - a result of incomplete oxidation, incorrect estimation of blanks, or a combination of both. 

Oxidation methods utilized for measurement include combustion-IR (infrared) and persulfate-UV (ultraviolet). 

Bronk, D.A., M.W. Lomas, P.M. Glibert, K.J. Schukert, and M.P. Sanderson. 2000. Total dissolved nitrogen analysis Comparisons between the persulfate, UV and high temperature oxidation methods. Mar. Chem. 69 163-178. 

A two-step mediated oxidation method can be proposed that separates the persulfate production step from its activation and organic pollutants oxidation. In this way, the optimum conditions of temperature and concentration can be adopted in order to reach the maximum efficiency of mediated oxidation. 

An improvement in mediated oxidation can be expected by increasing the efficiency of persulfate production and the oxidation rate of organic pollutants. These objectives can be reached with a new two-step mediated oxidation method that separates... 

Entries labeled this study are from the Chesapeake Bay Water Quality Monitoring Program (2004). Measurement methods included PO, persulfate oxidation UV, ultraviolet oxidation NG, not given. 

There are other problems in the wet oxidation method. For one, the precision of the method is far from good. Customarily, three replicates are taken from each water sample. After acidification, bubbling, and the addition of persulfate (not necessarily in diat order), the sample ampoules are sealed with a torch. They are then held until it is convenient to heat them, usually for 1 hr at 140 °C, break the ampoule, and measure the carbon dioxide evolved. Since there is often a considerable delay between sampling and analysis, sometimes as much as a month, there is no opportunity to retrieve mistakes or accidents. Our own experience has been that wild values, perhaps caused by contamination, occur in about 20% of the samples. The use of either subjective judgment or some empirical rule-of-thumb not far removed from subjective judgment, for the elimination of these wild values is widespread. 

Reactions with persulfate and pyrosulfate. The persulfate (peroxy-dlsulfate Ion, S2O8 ) reaction, also known as the Elba persulfate oxidation, has been Important In synthesis of hydroxylated phenols. The method has occasionally been used for synthesis of 0-sulfate conjugates. For example, 4-hydroxy-2-nltrophenyl sulfate was obtained when 3-nltrophenolate was stirred with potassium peroxydlsulfate at room temperature for 2 days (91,). The persulfate reaction has been used for the sulfation of various phenols and aromatic amines however the yields are usually low to moderate (77 ). The sulfate group Is preferentially Introduced In the 4-posltlon of phenols and In the 2-posltlon of aromatic amines but If these positions are blocked substitution at the 2- and... 

Fig. 6. Indirect comparison of depth-averaged TOC concentrations measured in the northwestern Atlantic with different oxidation methods (MacKinnon, 1978). A, Menzel (1970), persulfate oxidation a, MacKinnon (1978), dry oxidation A, Sharp (1973b), direct injection o, Skopintsev et al. (1966), dry oxidation , Gordon and Sutcliffe (1973), dry oxidation.

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