ASTM D1783-01(R2020) pdf free download

ASTM D1783-01(R2020) pdf free download.Standard Test Methods for Phenolic Compounds in Water
6. Interferences
6.1 Common interferences that may occur in waters are phenol-decomposing bacteria, reducing substances, and strongly alkaline conditions of the sample. Provisions incorpo- rated in these test methods will minimize the effects of such interferences. 6.2 Treatment procedures required prior to the analysis for removal of interfering compounds may result in the unavoid- able elimination or loss of certain types of phenolic com- pounds. It is beyond the scope ofthese test methods to describe procedures for overcoming all ofthe possible interferences that may be encountered in the test methods, particularly with highly contaminated water and industrial waste water. The procedures used must be revised to meet the specific require- ments. 6.3 A few methods for eliminating certain interferences are suggested. (See Section 8 for descriptions of reagents re- quired.) 6.3.1 Oxidizing Agents—If the sample smells of chlorine, or if iodine is liberated from potassium iodide on acidification of the sample, remove the oxidizing agents so indicated immedi- ately after sampling. The presence of oxidizing agents in the sample may oxidize some or all of the phenols in a short time. Ferrous sulfate or sodium arsenite solution may be added to destroy all of the oxidizing substances. Excess ferrous sulfate or sodium arsenite do not interfere since they are removed in the distillation procedure. 6.3.2 Sulfur Compounds—Compounds that liberate hydro- gen sulfide (H 2 S) or sulfur dioxide (SO 2 ) on acidification may interfere with the phenol determination. Treatment of the acidified sample with copper sulfate usually eliminates such interferences. Acidify the sample with sulfuric acid (H 2 SO 4 ) or hydrochloric acid (HCl) until just acid to methyl orange. Then add a sufficient quantity of copper sulfate (CuSO 4 ) solution to give a light blue color to the sample or until no more copper sulfide (CuS) precipitate is formed. Excessive amounts of H 2 S or SO 2 may be removed from the acidified sample by a brief aeration treatment or stirring before the addition of the CuSO 4 solution or both. (Warning—Acidification of certain samples may produce vigorous evolution ofcarbon dioxide (CO 2 ), SO 2 , H 2 S, or other gases. Therefore, perform the acidification cautiously and stir the samples during the process. Complete the evolution of gases before the sample is stoppered.) 6.3.3 Oils and Tars—If the sample contains oil or tar, some phenolic compounds may be dissolved in these materials. An alkaline extraction, in the absence of CuSO 4 , may be used to eliminate the tar and oil. Adjust the pH of the sample between 12 and 12.5 with sodium hydroxide (NaOH) pellets to avoid extraction of the phenols. Extract the mixture with carbon tetrachloride (CCl 4 ). Discard the oil- or tar-containing layer. Remove any CCl 4 remaining in the aqueous portion of the sample by gentle heating. N OTE 1—The presence of CuSO 4 is detrimental since it is converted to cupric hydroxide (Cu(OH) 2 ) by the NaOH. The Cu(OH) 2 acts as an oxidizing agent on phenols.
7. Apparatus
7.1 Buchner-Type Funnel with Coarse Fritted Disk—At least three funnels are needed for determination of phenolic compounds by Test Method A. Alternatively, standard glass funnels and pre-fluted filter paper may be used. The funnel paper must be large enough to hold 5 g of sodium sulfate. These funnels are not used in Test Method B. 7.2 Photometer—A spectrophotometer or filter photometer, suitable for use at 460 nm (Test Method A) or at 510 nm (Test Method B), and accommodating a cell that gives a light path of 1.0 to 10 cm shall be used. The size ofthe cell used will depend on the absorbance of the colored solutions being measured and the characteristics of the photometer. In general, if the absor- bances are greater than 1.0 with a larger cell, the next smaller size cell should be used.