ISO-11423-2-1997.pdf
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1、INTERNATIONAL STANDARD IS0 11423-2 First edition 1997-06-01 Water quality - Determination of benzene and some derivatives - Part 2: Method using extraction and gas chromatography Qua/it6 de I eau - DBtermination du benz a46Onet; p=iso; oisocs; s=centrai Printed in Switzerland ii Copyright Internatio
2、nal Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/18/2007 21:22:33 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 IS0 11423-2:1997(E) Introduction This part of IS0 11423 describ
3、es an extraction method of sample treatment followed by the gas chromatography for the determination of benzene and derivatives in water. For a head-space procedure see IS0 11423-l. Which of these methods is applicable in a given case depends for instance on the type of sample to be analysed and the
4、 instruments available to the analyst. The method used is then described in the test report. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/18/2007 21:22:33 MDTNo reproduction or networ
5、king permitted without license from IHS -,-,- INTERNATIONAL STANDARD 0 IS0 IS0 11423-2:1997(E) Water quality - Determination of benzene and some derivatives - Part 2: Method using extraction and gas chromatography 1 Scope The method described is applicable to the determination of benzene, methylbenz
6、ene (toluene), dimethylbenzenes (xylenes) and ethylbenzene (abbreviated hereafter to BTX) in water and waste water in concentrations above 5 pg/I. High concentrations may be determined by diluting the extract. A number of further derivatives and nonpolar compounds with similar boiling points may als
7、o be determined by this method. The applicability of the methods should be verified in these cases for the particular water sample. 2 Principle The unfiltered sample is extracted with a nonpolar solvent (e.g pentane) and the extract is analysed by gas chromatography. Benzene and its derivatives are
8、separated by injection on two capillary columns with stationary phases of different polarity (e.g. by simultaneous splitting) and determined using a suitable detector (for identification of compounds see 7.4). 3 Interferences Loss of BTX may occur during sampling, transport, storage and preparation
9、of samples due to evaporation and stripping. Other volatile compounds in the ambient air may contaminate water samples and water used for btank tests, leading to high limits of detection and high blank values, respectively. To avoid errors due to sorption or desorption of constituents, samples shoul
10、d not come into contact with plastics materials. Surfactants, emulsifiers and higher contents of polar solvents such as propanone or methanol will impair the extraction procedure. Suspended solids affect extraction and recovery. The presence of a second liquid phase (e.g. mineral oil, volatile organ
11、ic halogenated hydrocarbons, emulsified grease and waxes) will affect sampling, sample preparation and extraction. Only the content of the aqueous phase would be determined; it is possible, however, to determine the content of the second liquid phase separately. If this is done, it shall be stated i
12、n the test report. Specific problems in the gas chromatographic system shall be handled according to the manufacturer s instructions. The determination may be hindered by superposition of other hydrocarbons, for instance mineral oil constituents, which may also result in column overload. Copyright I
13、nternational Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/18/2007 21:22:33 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 1.1423-2: 1997(E) 0 IS0 If the results from the two di
14、fferent columns differ significantly, repeat the analysis with another separating phase or a specific detector. 4 Apparatus Keep all precleaned bottles and vials in an upside-down position for 1 h at 150 “C in a ventilated drying oven before use. After this procedure, protect them from contamination
15、, for instance by covering them with aluminium foil while they cool and closing them as soon as they are cool. 4.1 Conical-shoulder bottles, nominal capacity e.g. 2 I, of non-actinic glass with tight stopper or PTFE- or aluminium-lined cap. 4.2 Magnetic stirrer with PTFE-coated bars. 4.3 Pipettes, c
16、apacity e.g. 1 ml, 2 ml, 5 ml, 10 ml, 25 ml and 50 ml, made of glass. 4.4 Gas washing-bottle attachment with ground glass cone and sintered disc. 4.5 One-mark pipette. 4.6 Graduated flasks, capacity 100 ml, 250 ml and 1 000 ml. 4.7 Gas chromatograph with glass insert assembly and flame ionization de
17、tector (FlD) supplied with gases as specified by the manufacturer. 4.8 Capillary columns for gas chromatography (see annex B). NOTE - If alkanes with retention times identical with BTX are expected, the Kovacs indices are useful for the choice of the columns used. 4.9 Injection syringes, capacity 10
18、 pl, 50 pl and 100 pl. 4.10 Microseparator (see figure 1). 4.11 Quartz wool, cleaned with pentane and dried. 5 Reagents Use only reagents of recognized analytical grade and only water complying with 5.1. 5.1 Water for dilutions and the reagent blank. The BTX content of the water shall be as low as p
19、ossible. In case of contamination, the water may be treated as follows: Fill the water into conical-shoulder bottles (4.1), place a glass filter near the bottom of the flask, heat the water to approximately 60 “C. Pass a stream of nitrogen (approximately 160 ml/min) through the water for 1 h, then a
20、llow the water to cool to room temperature while still passing nitrogen through it. Close the bottle tightly and store in the dark. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/18/200
21、7 21:22:33 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 11423-2:1997(E) Dimensions in millimetres /Socket -Quartz wool y Cone and socket Figure 1 - Microseparator If necessary, pass nitrogen through the water immediately before use. Check the quality of the water bef
22、ore and after treatment. If contamination is still detected, use another gas for purification, or purify the gas used. 5.2 Operating gases for the gas chromatography system (nitrogen, helium, hydrogen, synthetic air) according to the manufacturer s instructions. 5.3 Pentane, C5H12, checked for absen
23、ce of BTX by gas chromatography. Distill contaminated pentane on a high performance column, with the purity of the distillate fractions being checked; it may be necessary to repeat distillation. 5.4 Calibration standard substances, each of highest purity. Benzene C6H6 Methylbenzene (toluene) C7H8 1,
24、2-Dimethylbenzene (o-xylene) C8H10 1,3-Dimethylbenzene (m-xylene) C8H10 1,4-Dimethylbenzene (p-xylene) C8H10 Ethylbenzene C8H10 3 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/18/2007
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- ISO 11423 1997
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