ISO-6439-1990.pdf

INTERNATIONAL STANDARD IS0 6439 Second edition 1990-05-15 Water quality - Determination of phenol index - 4-Aminoantipyrine spectrometric methods after distillation method B (chloroform extraction method) : this method is capable of measuring the phenol index without dilution from about O,OO2mg/l to about 0,lO mg/l when the coloured end-product is extracted and concentrated in chloroform phase, using phenol as a standard. NOTES 1 The limits of detection achievable with both methods are insuffi- cient for checking compliance with the limits given in the Directive 80/778/EEC for drinking water. 21 According to the results of a German interlaboratory trial using a method almost identical to method 6, the lower limit of detection is 0,Ol mg/l. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and IS0 maintain registers of currently valid International Standards. IS0 5667-l : 1980, Water quality - Sampling - Part 7: Guidance on the design of sampling programmes. IS0 5667-2 : 1982, Water quality - Sampling - Part 2: Guidance on sampling techniques. IS0 W-3 : 1985, Water quality - Sampling - Part 3: Guidance on the preservation and handling of samples. 3 Definitions For the purpose of this International Standard, the following definitions apply: 3.1 phenolic compounds: Hydroxy derivatives of benzene and its analogues. 3.2 phenol index: A number giving a concentration, ex- pressed in milligrams of phenol per litre, of different phenolic compounds based on the degree of colour they produce with 4-aminoantipyrine according to the procedure given. 4 Method A - Direct calorimetric method 4.1 Principle Separation of phenolic compounds from impurities and preser- vative agents by distillation. The rate of volatilization of the phenolic compounds is gradual, so that the volume of the distillate must equal that of the test sample being distilled. Reaction of the steam-distillable phenolic compounds with 4-aminoantipyrine at a pH of 10,O + 0,2 in the presence of potassium hexacyanoferrate(lll) to form a coloured antipyrine dye. Measurement of the absorbance of the dye at 510 nm. The phenol index is expressed as milligrams of phenol (C6HsOH) per litre. The minimum detectable quantity is equivalent to 0,Ol mg of phenol when a 50 mm cell is used in the spectrometric measurement and 100 ml of distillate are used in the determi- nation. 4.2 Reagents During the analysis, use only reagents of recognized analytical grade and only distilled water or water of equivalent purity. 4.2.7 4-aminoantipyrine, 20 g/l solution. Dissolve 2,0 g of 4-aminoantipyrine (CllH13N30) in water and dilute to 100 ml. Prepare this reagent just before use. If red particles remain, the solution cannot be used again, 1 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=Defense Supply Ctr/9960866100 Not for Resale, 04/24/2007 10:24:48 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 6439 : I!390 (EI 4.2.2 Ammonium chloride, 20 g/l solution. Dissolve 20 g of ammonium chloride (NH b) inhibit biochemical oxidation of phenolic compounds in the sample by adding I,0 g of copper(h) sulfate (4.2.5) per litre of the sample; cl store the sample in the cold (5 X to 10 W, and analyse the preserved samples within 24 h of collection. 4.5 Preliminary distillation The use of copper(h) sulfate, as described in 4.5.1 during distillation of an acidic sample, permits the formation of cop- per(ll) sulfide without subsequent decomposition to hydrogen sulfide. The acidic solution also prevents the precipitation of copper(h) hydroxide, which acts as an oxidizing agent towards phenolic compounds. 4.5.1 Measure 500 ml of the sample into a beaker. If the sample was not preserved with copper sulfate 14.4.2 611, add 5 ml of copper(h) sulfate solution (4.2.61, and adjust the pH of the solution to between 1 and 2 with phosphoric acid (4.2.13). Transfer the mixture to the distillation apparatus (4.3.1). Use a 500 ml graduated cylinder as receiver. Distil400 ml of the sample. Stop the distillation and, when boil- ing ceases, add 100 ml of water to the distillation flask. Con- tinue the distillation until a total of 500 ml has been collected. NOTE - It is also possible to distil smaller quantities. 4.52 If the distillate is turbid, a second distillation may prove helpful. Acidify the turbid distillate with phosphoric acid (4.2.131, add 5 ml of copper(ll1 sulfate solution (4.2.61 and then repeat the distillation described in 4.5.1. The second distillation usually eliminates the turbidity. However, if the second distillate is also turbid, extract another sample as described in 4.5.3. 4.5.3 Extract as quickly as possible a 560 ml aliquot of the laboratory sample as follows. Add 4 drops of methyl orange (4.2.8) and sufficient sulfuric acid (4.2.16.1) to make the solution acidic. Transfer to a separating funnel and add 150 g of sodium chloride (4.2.16.2). Shake with five separate portions of chloroform, starting with a volume of 40 ml, and then with four volumes of 25 ml. Separate the chloroform layer after each extraction and com- bine the chloroform extracts in a second separating funnel. Shake with three separate portions of sodium hydroxide solu- tion (4.2.16.31, starting with a volume of 4,0 ml and then with two volumes of 3,0 ml. Separate the sodium hydroxide solution after each extraction. Combine the alkaline extracts, heat on a water-bath until the chloroform has been removed, then cool and dilute to 500 ml with water. Proceed with the distillation as described in 4.51. NOTE - In some cases, in waste waters with high concentrations of phenolic compounds, a rise in temperature occurs during extraction. 4.6 Procedure 4.6.1 Test portion Place 100 ml of the distillate, or a suitable aliquot which con- tains not more than the equivalent of 0,5 mg of phenol diluted to 100 ml, in a 250 ml beaker. If the sample is known to contain more than the equivalent of 0,5 mg of phenol, a smaller aliquot shall be used. Trial and error tests may be necessary to deter- mine the volume of a suitable aliquot. Practically, the smallest aliquot that contains not more than the equivalent of 0,5 mg of phenol should be 10 ml. The distillate and all solutions used shall be at room temperature. 4.6.2 Blank test Carry out a blank test in parallel with the determination, replac- ing the test portion with 106 ml of water. 4.6.3 Preparation of the calibration graph 4.6.3.1 Preparation of the set of calibration solutions Prepare a set of calibration solutions, in seven 506 ml one-mark volumetric flasks, containing 0 ml; 25 ml; 50 ml; 100 ml; 150 ml; 200 ml; and 250 ml of phenol standard solution (4.2.10). Make up to the mark with water. All solutions used shall be at room temperature. The set of calibration solutions shall be treated according to 4.5.1. 4.6.3.2 Formation of the absorbing compound Allow the absorbing compound to form in the set of calibration solutions according to the procedure described in 4.6.4. 4.6.3.3 Spectrometric measurements After 15 min, transfer the solutions to absorption cells and measure the absorbance of each calibration solution at 510 nm using water in the reference cell. 3 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=Defense Supply Ctr/9960866100 Not for Resale, 04/24/2007 10:24:48 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 6439 : 1990 (E) 4.6.1 Oxidizing agents If the sample smells of chlorine, or if iodine is liberated from potassium iodide on acidification of the sample, the oxidizing agents so indicated should be removed immediately after sampling. Ascorbic acid solution should be added immediately after sampling to destroy all of the oxidizing substances. Excess ascorbic acid does not interfere since it is removed in the distillation procedure. 4.6.3.4 Plotting the graph Plot the absorbances against the corresponding masses, in milligrams, of phenol. 4.6.4 Determination Add 5 ml of buffer solution (4.2.4) to each test portion (4.6.11, or add 5 ml of ammonium chloride solution (4.2.2) to each and adjust the pH to 10 I!I 6,2 with ammonium hydroxide (4.2.3). Add 2,0 ml of 4-aminoantipyrine solution (4.2.11, mix im- mediately, then add 2,0 ml of potassium hexacyanoferrate(lll1 solution (4.2.14) and again mix immediately. After 15 min, measure the absorbance of each solution in a cell (see 4.3.3) at the wavelength of maximum absorbance (approx- imately 510 nm) using water in the reference cell. By reference to the calibration graph (4.6.3.4) calculate the mass, in milligrams, of phenol equivalent to the phenolic compounds in the test portion, after making allowance for the blank (4.6.2). Estimate the phenol index of the test portion by reference to the calibration graph and to the absorbance obtained with the solution of sample. 4.7 Expression of results The phenol index, expressed in milligrams per litre, is given by the formula Estimate the phenol index of the test portion by reference to the calibration graph and to the absorbance obtained with the solution of sample. -5dOOO v, where m is the mass, in milligrams, of phenol equivalent to the phenolic compounds in the test portion; V. is the volume, in millilitres, of the test portion. 4.6 Interferences Common interferences that may occur in waters are phenol- decomposing bacteria, oxidizing and reducing substances, and strongly alkaline conditions of the sample. Biological degradation is inhibited by the addition of copper sulfate 14.4 b) to the sample. Acidification with phosphoric acid L4.4 all assures the presence of the copper ion and eliminates any chemical changes resulting from the presence of strong alkaline condi- tions. Treatment procedures required prior to the analysis for removal of interfering compounds may result in the unavoidable elimination or loss of certain types of phenolic compound. Consequently, some highly contaminated waste waters may re- quire specialized techniques for elimination of interferences and for quantitative recovery of the phenolic compounds. A few methods for eliminating certain interferences are sug- gested as follows. 4.8.2 Oils and tar If the sample contains oil or tar, some phenolic compounds may be dissolved in these materials. An alkaline extraction, in the absence of copper sulfate, may be used to eliminate the tar or oil. Adjust the pH of the sample to between 12 and 12,5 with sodium hydroxide (4.2.16.3) to avoid extraction of phenolic compounds. Extract the mixture with carbon tetrachloride as quickly as possible. Discard the carbon tetrachloride layer. Remove any carbon tetrachloride remaining in the aqueous portion of the sample, for example by gentle heating, and adjust the pH to 4,0 (see 4.4). 4.6.3 Sulfur compounds Compounds that liberate hydrogen sulfide on acidification may interfere with the determination of the phenol index. Treatment of the acidified sample with copper sulfate usually eliminates such interference. Add a sufficient quantity of copper sulfate solution (4.2.6) to give a light blue colour to the sample or until no more copper(h) sulfide precipitate is formed, then acidify the sample with phosphoric acid (4.2.12) until just acid to methyl orange (4.2.8). 4.8.4 Reducing agents In the presence of reducing agents, add an excess of potassium hexacyanoferrate(lllj. 4.6.5 Amines Under the specified reaction conditions some amines will be determined as phenols, thus resulting in values which are too high. This interference may be minimized by distillation at below pH 0,5. 5 Method B - Chloroform extraction method 5.1 Principle Separation of phenolic compounds from impurities and preser- vative agents by distillation. The rate of volatilization of the phenolic compounds is gradual, so that the volume of the distillate must equal that of the test sample being distilled. Reaction of the steam-distillable phenolic compounds with 4-aminoantipyrine at a pH of IO,0 + 0,2 in the presence of potassium hexacyanoferrate(lll) to form a coloured antipyrine dye. Extraction of this dye from aqueous solution with chloroform and measurement of the absorbance at 460 nm. The phenol index is expressed as milligrams of phenol per litre. 4 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=Defense Supply Ctr/9960866100 Not for Resale, 04/24/2007 10:24:48 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 5439 :I990 (El For the spectrometric measurement, the minimum detectable quantity is equivalent to 0,005 mg of phenol when the test por- tion is extracted with 25 ml of chloroform and measured in a 50 mm cell, or extracted with 50 ml of chloroform and measured in a 166 mm cell. The minimum detectable phenol in- dex is 0,002 mg/l in 500 ml of distillate.tr 5.2 Reagents 20 ml; 30 ml; 40 ml; and 50 ml of phenol standard solution (4.2.11). Make up to the mark with water. All solutions used shall be at room temperature. The set of calibration solutions shall be treated according to 4.5.1. 5.5.3.2 Formation of the absorbing compound Allow the absorbing compound to form in the set of calibration solutions according to the procedure described in 5.5.4. See 4.2. 5.5.3.3 Spectrometric measurements 5.3 Apparatus See 4.3, with the following modification and addition. 6.3.1 Spectrometer, as in 4.3.3, but suitable for use at 460 nm. 5.3.2 Biichner funnel, with coarse fritted disc or phase separator filter. 5.4 Sampling and samples see 4.4. 5.5 Procedure 5.5.1 Test portion Place 500 ml of the distillate, or a suitable aliquot which con- tains not more than the equivalent of 0,05 mg of phenol diluted to 500 ml, in a 1 litre beaker. Trial and error tests may be necessary to determine the volume of a suitable aliquot. Prac- tically, the smallest aliquot that contains not more than the equivalent of 0,05 mg of phenol should be 50 ml. The distillate and all solutions used shall be at room temperature. 5.5.2 Blank test Carry out a blank test in parallel with the determination, replac- ing the test portion with 506 ml of water. 5.5.3 Preparation of the calibration graph 5.5.3.1 Preparation of the set of calibration solutions Prepare a set of calibration solutions, in nine 500 ml one-mark volumetric flasks, containing 0 ml; 1 ml; 2 ml; 5 ml; 10 ml; Measure the absorbance of each calibration solution at 460 nm using chloroform in the reference cell. 5.5.3.4 P