ISO 7875-1:1996 pdf free download

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ISO 7875-1:1996 pdf free download.Water quality — Determination of surfactants — Part 1: Determination of anionic surfactants by measurement of the methylene blue index (MBAS).
1 Scope
This part of ISO 7875 specifies a spectrometnc method for the determination of anionic surfactants by measurement of the methytene blue index (MBASI in aqueous media.
The method is applicable to drinking water, sisface water as well as waste water, for example for the determination of the primary degradation of suifactants under investigation in test systems corntairng natural or synthetic waste water II applies for both laboratory scale and technical waste-water treatment plants.
In the case of effluents originating from municipal waste-water treatment plants, the MBAS index comprises not only synthetic but also, to a considerable extent, natural anionic surface active substances
This method is applicable to a range of concentrations from 0.1 mgI to 5.0 mgd( and the limit of detection is about 0,05 mgI for solutions of standard surfactants in stilled water.
Under the experirnenl& conditions, sulfonates and sulfates are the compounds chiefly measured, but some positive and negativ, interfer,nce may occur (see c+,ause 9).
2 Normative references
The following standards contain provisions which, through reference m this text, constitute provisons of this pert of ISO 7875. At the twne of publication, the editions indicated were valid. All standards are subØct to revision, end parties to agreen,ents based on this pert of ISO 7875 at. encouraged to investigate the possibility of applying the most recent editions of the standards indicated below Members of IEC and ISO maintain registers of currently valid International Standards.
ISO 5667-21991, Water quakty — Sampling — Part 2: &udpnce on wripling techniques
ISO 5667-3:1994, Water quality — San’puig — Part 3. Gwdarice on the preservarnon and herding of samples
3 PrInciple
Foirnatior, of salts from methylene blue and anionic sialactants in an alkaline medium. Extraction of thes salts with chloroform end ecid treetm•nt of the chloroform solution. Elimination of any interferences by extraction of the anionic surf actant-methylene blue complex from alkaline solutions and shaking with acidic methytene blue solution.
Measurement of th. absorbance ol th. separated organic phase at the maximum absorption wavelength of 650 nm. Evaluation by means of a ca1iIrabon curve.
For reasons of purity and stability, the preferred standard dodecyl benzene sulfonic aced methyl ester Itetrapropylene type, of relative rnotecutai mass 340). althougi, other cahbrat’on standards may be used tse. the note to 4.1 U. The calibratcn standard * prepared from the standard dodacyl benzene sulfonic aced ester after ,apon*ficatson to the sodium salt Calculation ol the MBAS index as sodium dodecyl benzene sulfonate (see 8 1).
During the analysis, unless otherwe stated, use only reagents of recognized analytcal grade and only distilled water or water of equralorit purity
4.1 SodIum chloride (NeCI).
4.2 Ethyl ac.tate (C4HaO2I. freshly distilled
CAUTiON — Ethyl acetate Is flammable and toxic.
4.3 Chloroform ICHCI,)
CAUTiON — Chloroform Is a suspected carclnog.n.
If necessary 11cr eicarnple if it gives rise to hegi’ results in blank tests (7.211 purify the cNoroform by filtration Through AlO3 (neutral grade, W 200).
NOTE — Due to the loxecily of chloroform. it would be reIeratile to replace ii by another sotvei. Research work ts continuing
4.4 Ethanol IC H5OH), 95 $ (V/V)
4.5 Methanol ICH3OH), freshly destibd.
In order to avoid high results in blank tests (7.2) store ii a glass bottle.
4.6 Sulfuric acid 2°4• 0,5 moM solulion.
4.7 Ethanollc sodium hydroxide NaOH), 0,1 moldl solution en ethanol.
Dissolve 4 gal sodium hydroxide peflets in ethanol (4.4) and dilute to 1 000 ml with the same ethanol
4.8 Methylen. blue, neutral solutiofl
NOTE — The sotd methylene blue used should be the purest available
Dissolve 0,350g of methylene blue in water and dilute to 1 000 ml.
Prepare the solution at least 24 h before use
This soluton is stable for at least 2 weeks.
The absortiance of the chloroform phase of the blank test (See 7.2), measured against chloroform. shal not exceed 0,2 per 1mm of optical patti length at 650 rim In the case of higher absorbances during the blank test. usa other batches of rnettiylane blue and,tor purity the methylene blue solution by extraction as follows,
Place the methylene blue solution na suitably large separating funnel. For each 100 ml of rnelhylene blue solution. add 200 nil of buffer solution (4.1w and 200 nil of chloroform (431 Shake for 30s and allow to separate Run off the chloroform layer as completely as possible and rinse the aqueous layer without shaking with 60 ml of chioroforn for each 100 ml of mnetl’iylene blu solution Repeat the extraction and rinse as before. Discard the chloroform extracts; collect for reuse alter treatment.
4.9 Metttylene blUe. acidic solution.
Dissolve 0.3509 of methylene blue in 500 ml of water and add 6,50 ml of sulfuric acid (p – 1.84 gnl). Dilute with water to 000 ml after mixing
Prepare the solution at least 24 h before use.
The ebsoibence of the chloroform ptias. of the blank test (see 7.2). measured against chloroform, shall not exceed 0.02 per 10mm of optical path length at 650 rim ri the case of higher blar* absorbances, either wash the methylene blue solution twice with ctiloiof arm (or purification (see 4.81 or use other batches of rnethy4ene blue.
4.10 Buffer solution, of pH 10,
4.10.1 Cissolve 249 of sodium hydrogencarbonate (NaCO), and 27 g of anhydrous sodium carbonate (Na2COl in water and dilute to 1 000 ml.
4.10.2 Memetively. especially for very hard waler, the buffer solution prepared in may be used Disodlum tetraborato Nal34O, 10H70), 0.05 molIl solution.
Dissolve 199 of disodium tetraborate decatrydrate in 1 000 ml of water.
This solution is stable for at least 2 weeks it stored in a stoppered glass bottle.
4.1022 Sodium hydroxide (kaOH 0.1 moldt solution.
Dissolve 4g of sodium hydroxide petlets in 1 000 ml of waler.
This so&sfion is stable for at least 2 weSks it stored in a glass bottle with a polVethy(en. stopper. Borate, alkeline solution.
Mix equal volumes of disodium tetraborate solution (4,10.2,1) arid sodium hydroxide solution (4.10,2.2).
This solution is stable for at least 1 week if stored in a glass bottle with a polyethylene stopper
4.11 suRonlc acid methyl ester Itetrapropylena lypel (CgHO3S, stock standard solution
Weigh, preferably from a weighing pipette, to the nearest 0.1 mg. 400 mg to 450mg of dodeeytenzene sulfonc acid methyl ester, into a rourid-bottorred flask, and odd SO ml of ethenol sodium hydroxide solution (4.7) and some anti-burrpng granules. Attach th reflux condenser and boil for 1 Ii. After cooling, rinse the condenser and the ground-glass joint with about 30 ml of ethanol (4.4) and add the nrrslngs to the contents of the flask Neutralize the
solution with sulfunc acid (4.61 against phenolphtalein (4 12) until it becomes colourless Transfer the solution to a 1 000 ml one-mark volumetric flask, dilute to the mrk with water and mat.
This standard solution a stable (or at least 5 months.
NOTE — Although the dodecyiberise suMonic acid m.thyl ester is preferable as it ii a guaranteed nothygroecoplc slanclerd, the cation graph (see 73 may alternatively be established with the aid of commercially available sodllum san of dodecane1 sulfonic acid lC1l’iNeOSi. dod.can.’l suMuric acid (C1HNaO.Sl or dioclyl sullosuccinic acid ICl-l3,NaO,Si
4.12 Pti.nolphtaleln. nc5cator solution
Dissolve 1,0 g of phenoptitaloin in 50 ml of ethanol 444) and add, while stirring continuously. 50 ml of water Filter oft any precipitate that forms.
5 Apparatus
Ordinary laboratory equipment and th, following
5.1 pH-meter. with suitable electrodes made from glass.
52 Sp.ctrom.1.r with sel.ctors for discontinuous variation, capable of rneasurernem at 650 nm, equipped with cells of optional path lengths 10mm and 50mm,
5,3 Gas-stripping apparatus (see figure 1), which is commercially available of capacity 1 litre. The diameter of the sintered disc shall be the same as the internal diameter of the cybnder.
1 To make cleaning easier, the apparatus should preferably be equed with a spherical connection under the stripping
tunneL The fixing member shoiid aleo be divisibl
2 During piewiery cleaning, all glassware should be washed thoroughly with water arid then with elhenol,c hydroddonc
acid about 10 % beilel and aiAsequsntly rinsed with waler
6 Sampling and samples
instructions for sampling are given in ISO 5667-2 and ISO 56673
Do not withdraw samples through a foam layer Use clean glass bottles. previously washed with methanol 445) for sampling and storage Cooling to 4 C is recommended for preservation over stioit periods. Consider the addition of a preservabve if the sample m to be kept for more than 24h The addition of 1% (YN) of a 40% (YN)
formaldehyd. solution is suitable for periods up to 4 ci while saturating with chiorofomi is suitable for periods up to8d.
NOTE — Test sancies shoijd normally be tree of suspended meteor which can be separated by cenirifugalion, however, it should be aperec,ated that, as a resiit of such a sepera(’i. aurtectant adsorbed on suspended matter will not be determined
7 Procedure
7.1 ConcentratIon and s.paratlon of the surfactant
For eli types for water with known matrices endlor tree of interferences, proceed according to 7.4. For determination of the total amount of MBAS in th. presence of solids, also proceed according to 7.4. although quantitative recovery is not guaranteed due to sorption effects. For analysis of the amount of dissolved MBAS, use the following concentration end separation procedure.
Measote the absorbance of each of the set of the calibration solutions. induding th. zero member. at a wavelength of 650 rwn in cells of optical path lengths 10mm toSO mat. Proper. a calibration graph by plotting the aboorbance egeinat the mess. in micrograms, of si,afeC(aflt contained in the calibration solution and si.tract th interpolated absorbances (intersection with the ordinate) of the tlar* from the absoibenc.,. A1, of sad cekbration solution
Calibrate once or twice a month or wrienever new belches of aiernicala are used
lithe calibration is carried out with one of the alternative surf actants see 4 ilL use the conversion factors Ii shown in table 1
7.4 Detrmination
Transfer a measured volume of the test sample, rt necessary treated according to 7.1 into a separating funnel This test portion should contain between 20 llQ and 200 rg of MBAS In the lower MBAS range. a test portion of up to 100 ml may be used, if th. volume of the test portion is less than 100 ml, dilute with water to 100 ml Add 5.0 ml of neutral rneihytene blue solution 44.81. 1Dm) of buffer solution (4.101 (not necessary if a pre’extracted n’iethylene blue solution is used). and 15 nil of chloroform 1434. Shak. evenly arid gently about twice a second for 1 mlii. preferably in a horizontal plane. Allow the layers to separate as Completely as possible arid swirl the funnel to dislodge droplets from the sides of the funnel
Allow to settle for 2 mm. then riai as much poss4,le of the chloroform layer into a second separating funnel. containing 110 ml of water and 5.0 ml of acidic methytene blue solution 1491 Shake wvformly but not too vmgorouly for I mm as previously described Filter the Chloroform layer through a cotton or glass woof lifter wetted with chloroform 44 3) into a 50 ml voltxnetnc flask. IOn cotton wool, some absorption of surfactarits may take place: on glass wool, water may not be absorbed completely)
Repeat the extraction of the alk,lan and acid solutions using a 10 ml portion of ctiloeofornn 44,31 for the extraction. Separate the chloroform layer and filter it. through the same lifter, into the volumetric flask, Repeat the extraction using a further 10 ml portion of chloroform and filter that into the 50 ml vclurrmetnc flask. Dilute to the mark with chloroform and mix
Fe each batch of test samples, carry out the complete extiection for a blank determination on 100 ml of water and on on of the calibration solutions Isee 731.
Before eacn determination, shake the contents of the volumetric flask, rinse me optical cell of the soectromete’ (5.2) three times with the goltiQn a, thls flask, and then fill the Cal.
Moasijre the absorbances 1pm test samrçles. calibration solutions and the blank test with a spectrometer at a wavelength of 650 rim in cells of optical path lengThs 10mm to 50 mm against chloroform Comparison measurements on standards shall have been made in the same size of cells Wash out the calls with Chloroform after each readag.

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