Sulfate analysis

The precision of the technique indicates its suitability for sulfate analysis. The technique appears not to be subject to any interference normally present in seawater samples. 

Volpi, N. (2006). Advances in chondroitin sulfate analysis Application in physiological and pathological states of connective tissue, and during pharmacological treatment of osteoarthritis. Curr. Pharm. Des. 12, 639-658. 

Some difficulty was experienced in establishing a strict correlation between liberation of amino group and sulfate release. For example, Wolfrom and McNeely, and Jorpes, Bostrom and Mutt, did not obtain correspondence between these when heparin was treated with hot, dilute acid. It was suggested that retention of the barium sulfate in the colloidal state (peptization) by the heparin might be responsible for inaccurate results in sulfate analysis. If, however, heparin was first treated with hot, dilute alkali, then, on subsequent acid treatment, correspondence between release... 

Attempts to increase pyrite removal by increasing the reaction time met with limited success under our standard conditions because reaction of the ferric ion with the coal matrix depleted the ferric ion that was needed for extraction of the pyrite. Thus, for example, increasing the coal reaction time from 2 to 12 hrs only increased pyritic sulfur removal from 60 to 80% for Pittsburgh coal. Similar results were obtained for the other three coals. The only alternatives were to increase the amount of leach solution or to use a continuous or semi-continuous (multiple-batch) reactor. A multiple-batch mode was chosen because it was a simple laboratory procedure and at the same time it could approximate conditions encountered in a commercial plant. A 1-hr-per-batch leach time was used because our 2 hr results indicated that in the early stages of removal the rate begins to decrease after 1 hr, and six leaches (or batches) per run were used to assure that any pyrite that could be removed in a reasonable amount of time was removed. The progress of removal was monitored by analyzing the sulfate content in each spent leach solution elemental sulfur was not removed until all the leaches were completed. Table VII shows pyrite extraction as a function of successive leaches as followed by sulfate analysis of the leach solution. Note that the major portion of pyritic sulfur is removed in the first two leaches or 2 hrs, followed by lesser amounts in... 

Table 8.6. Comparison of ion chromatography and wet-chemical methods for sulfate analysis.

Our consultant is Professor Barry M. Preesip at the Department of Chemistry, Bear Creek University. He has a special interest in water analysis and is an analytical chemist. He is very familiar with similar methods for sulfate analysis. 

This is a very well-known reaction and has been used in sulfate analysis methods in the past. What is new and different here is that spectrophotometry is used to monitor the reaction as it progresses. In that way, one can tell when the reaction is complete (when all the sulfate is consumed), how much barium chloride solution has been added to that point, and then the amount of sulfate that was present calculated via stoichiometry. The graphical picture of the progress of the reaction suggested in the procedure is useful because you can visually observe the point at which the reaction is complete and then know the mL of the barium chloride solution used at that point. This is then the starting point for the stoichiometry calculation. 

Sulfate analysis. It is recommended that 50 ml of the water sample is introduced into a pre-cleaned and rinsed polyethylene container with a polypropylene cap, or into a glass bottle. In both cases, store the sample at 4°C, either in a cool box on-site and during transportation, and then in a fridge in the laboratory. Ensure that the container is completely full of the sample. In this situation, the sample can be held for up to 28 days for the analysis of sulfate. 

The data obtained at 1000 Torr pressure (5 ppm SO2/N2) suggests a significant dependence on eomposition with regards to the extent of sulfation (Figure 2). Specifically, the 90 at.% system demonstrated a substantial quantity of chemisorbed surface sulfur species. This observation is consistent with the observations noted with the sulfation analysis of ceria-only model catalysts. However, the intermediate compositional range was relatively insensitive to sulfur adsorption, while high zirconium concentrations indicated the... 

To measure the validity of the EPM technique coals were chosen in which sulfate sulfur as determined by ASTM methods equaled zero and in which pyritic sulfur was minimal as determined by ASTM methods and as observed by optical microscopy. Since inorganic sulfur contents are small, any discrepancies between EPM and ASTM organic sulfur contents due to inaccurate pyrite or sulfate analysis also should be small. As can be seen in Table II the EPM analyses very closely approach those of the ASTM. 

There are two accepted methods for determining the sulfur dioxide (SO2) concentration in the atmosphere of interest. Both employ the affinity of lead oxide for sulfur dioxide. The most common technique uses sulfation plates. This procedure is covered in dqtail in ASTM G 91, Test Method for Monitoring Atmo heric SO2 Using the Sulfation Plate Technique. These devices are no longer available for purchsise, but must be prepared in the laboratory. The second method is the peroxide candle, similar in its function to the chloride candle. The procedure suggests a 30-day exposure, followed by a standard sulfate analysis. This procedure is covered by ASTM D 2010, Test Methods for Evaluation of Total Sulfation Activity in the Atmosphere by the Lead Dioxide Technique. In both cases, the results are calculated as the capture rate of SO2 per unit area, normally per m. ... 

Native polysaccharides with acid groups other than the uronic type are not very common except for the sulfate esters. Total acidity may be estimated by direct titration, but erroneous results are obtained if the polysaccharide is alkali-labile as is the case with many oxidized polysaccharides. Addition of calcium acetate (7, 8) or sodium bromide 8, 9) to the polysaccharide solution increases the accuracy of the titration. Other methods for the estimation of carboxyl and other acidic groups involve determination of the amount of methylene blue absorbed, or determination of the amount of silver salt formed by exchange from a solution which contains silver in combination with a very weak acid. The sulfate content of polysaccharide sulfates, such as agar, is obtained by ordinary sulfate analysis of the completely hydrolyzed or ashed polysaccharide. 

The disk surface is thus exposed only to gaseous SO, not particulates. The American Society for Testing of Materials (ASTM) procedure suggests a 30-day exposure, followed by a standard sulfate analysis [16]. The other method sometimes used is the peroxide candle, similar in its function to the chloride candle, but again using lead peroxide to capture SOy In this procedure, a lead peroxide paste is applied to a paper thimble in the laboratory, and allowed to dry thoroughly before exposure. The thimble is then exposed in an instrument shelter to the test yard environment. In both cases, the SOj deposited results are appropriately reported in terms of deposition rate on the surface in units of mg/m /day. 

In addition to analyses for CAA, other analyses that require different preservation steps may be desired. Listed below are the most common analyses and the preservation steps that they require also, see lists in Lico et al. (1982). Samples for chemical oxygen demand and total organic carbon should be treated with 2 ml of concentrated H2SO4 per liter of sample. Samples for phenols should have Ig of copper sulfate added per liter of sample, and then should be acidified to pH 4 with phosphoric acid. Samples for dissolved metals should have 3 ml of 1 1 nitric acid added per liter of sample. Samples for sulfide analysis should have 2ml of zinc acetate added per liter of sample. Samples for nonmetal anions and sulfate analysis need no treatment. 

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