ISO 7875-1:1996 pdf download – Water quality -Determination of surfactantsPart 1: Determination of anionic surfactants by measurement of themethylene blue index (MBAS).
This solution is stable (or at least 2 weeks.
The absorbance of the chloroform phase of the blank test (see 72). measured against chloroform, shaft not exceed 0.2 per 10 mm of opticS path length at 650 nm In the case of higher absorbances during the blank test, use other batches of meihyfene blue andlor purify the methylene blue solution by extraction as follows
Place the methylene blue solution in a suitably large separating funnel. For each 100 ml of methylene blue solution, add 200 ml of buffer solution (410) and 200 ml of chloroform (4.3). Shake for 30 a and allow to separate Run off the chloroform layer as completely as possible and rinse the aqueous layer without shaking with 60 ml of chloroform for each 100 ml of rnethylene blue solution Repeat the extraction and rinse as before Discard the chloroform extracts: collect for reuse after treatment.
4.9 Methylen. blue, acidic solution.
Dissolve 0.3509 of methylene blue in 500 ml of water end add 6.50 ml of sulfuric acid (p 1,84 g/ml). Odute with water to 1 000 ml after mixing
Prepare the Solution at least 24 h before use.
The absortiance of the chloroform phase of the blank test (see 7.2). measured against chloroform, shall not exceed 0,02 per 10 mm of optical path length at 650 nm In the case of higher blank absorbances. e4ther wash the methylene blue solution twice with chloroform for punfication (see 4.8) or use other batches of methylene blue.
4.10 Butter solution, of pH 10
4.10.1 Dissolve 24 g of sodium hydrogencarbonate (NaCO3), and 27 g of anhydru5 sodium carbonate (Na2CO3) wi water and dilute to 1 000 rid,
4.10.2 Alternatively, especially for very hard water, the buffer solution prepared in may be used. Disodlum t.traborate (Na2640710H20). 0,05 mo1 solution.
Dissolve 19 g of disodium tetraborate decahydrate in 1 000 ml of water
This solution is stable for at least 2 weeks if stored in a stoppered glass bottle
4102.2 Sodium hydroxide (NaOH’l, 0,1 molil solution.
Dissolve 4g of sodium hydroxide pellets in 1 000 ml of water.
This solution is stable for at least 2 weeks if stored in a glass bottle with a polyethylene stopper. Borat., alkaline solution.
Mix equal volumes of disodium tetraborate solution (4 10,2,1) and sodium hydroxide solution (4 102.2(.
This solution is stable for at least 1 week if stored in a glass bottle with a polyethylene stopper
4.11 sulfonic acId m.thyl .st (tetrapropylene type) 1C19H3203S), stock standard Solution.
dodecylbenzene sutforric acid methyl ester, into a round-bottomed flask, and add 50 ml of ethanol sodium hydroxide solution 14.7) and some anti-bumping granules. Attach the ref lux condenser and boil for 1 h. After cooling, rinse the condenser and the ground-glass o.rrt with about 30 ml of ethanol (4.4) and add the nnsings to the contents of the flask Neutralize the solution with sulfuric acid 14.61 agetnat ph,noiphtalein 14 12) until it becomes colourless. Transfer the SOlution 10 a 1 000 ml one-mark volia’netric flask, dilute to the mark with water and mix.
This standard solution is stable for at least 6 months.
NOTE — Although the dodecylbenze sultonic acid methyl ester is preferable as it is a guaranteed nonhygrosoopic standard, the calioration graph see 7.3) may alt.rnativehr be •stabhshsd with the aid of commercially available sodium sal of dodecane1 sutfonic acid fC12HNaO,S). dodecane-1 sulfuric acid (C*lNa0aS) or dioctyl sutfosuccinic acid (Cf’$NaO7S)
4.12 Phertolphialein. indicator solution.
Disso’ve 1,09 of phenophtalein in 50 ml of ethanol (441 arid add, while stirring continuously. 50 ml of water Filter off any precipitate that forms.
5 Apparatus
Ordinary Laboratocy equipment arid the 1o(lowg.
5.1 pH-meter, with suitable electrodes made from glass.
52 Spectrometer with selectors for discontinuous variation, capable of measurement at 650 rim, equipped
with ceft of optional path lengths 10 mm and 50 mm
5.3 Gas-stripping apparatus (see figure 1). which is corrrnercialty available of capacity 1 litre
The diameter of the sintered disc shell be the same as the internal diameter of the cylinder.
1 To make cleaning easier, the apparatus should preferabty be equipped with a spherical connection under the stripping
luiwneL The fixing member should also be divisle
2 During prelinwiary cleaning, all glassware Should be washed thoroughly with walê arid then with ethandic hyckodilont acid about 10 % (aiim I and subsequently rinsed with water
6 Samphng and samples
Instructions for sampling are given in ISO 5667-2 and ISO 5667-3
Do not wrth&aw samples through a foam layer. Use clean glass bottles, previously washed with methanol (4.5) for sampling and storage Cooling to 4 C is recommended for preservation over short periods. Consider the eddition of a preservative if the sample is to be kept for more than 24 h. The addition of 1 $ (VIV) of a 40 $ (VIV)
formaldehyde solution is suitable for periods up to 4 d while saturating with chloroform is suitable for periods up to 8 d.
NOTE — Test samples should normnaly be free ol suspended matleer ,ich can be separated by centrifugation. however, it should be appreciated that, as a result of such a separation. surlactant adsorbed on suspended matter wil not be determined.