1、BRITISH STANDARD BS6068-2.31: 1987 ISO6333:1986 Water quality Part2: Physical, chemical and biochemical methods Section2.31 Method for determination of manganese: formaldoxime spectrometric method ISO title Water quality Determination of manganese Formaldoxime spectrometric method UDC556.11+614.777+
2、628.1/.3+663.63:53/54BS6068-2.31:1987 This British Standard, having been prepared under the directionof the Environment andPollution Standards Committee, was published underthe authority of the BoardofBSI and comes intoeffect on 30 June1987 BSI07-1999 The following BSI references relate to the work
3、on this standard: Committee reference EPC/44 Draft for comment85/50075DC ISBN 0 580 16017 3 Amendments issued since publication Amd. No. Date of issue CommentsBS6068-2.31:1987 BSI 07-1999 i Contents Page National foreword ii 0 Introduction 1 1 Scope and field of application 1 2 Principle 1 3 Reagent
4、s 1 4 Apparatus 2 5 Sampling and samples 2 6 Procedure 2 7 Expression of results 3 8 Interferences 3 9 Test report 4 Table Reproducibility of the method 4BS6068-2.31:1987 ii BSI 07-1999 National foreword This Section of this British Standard has been prepared under the direction of the Environment a
5、nd Pollution Standards Committee and is identical with ISO6333-1986 “Water quality Determination of manganese Formaldoxime spectrometric method”. The international standard was prepared by subcommittee2, Physical, chemical and biochemical methods, of Technical Committee147, Water quality, of the Int
6、ernational Organization for Standardization (ISO) with the active participation and approval of the UK. This British Standard is being published in a series of Parts subdivided into Sections that will generally correspond to particular international standards. Sections are being, or will be, publish
7、ed in Parts1 to6, which together with Part0, are listed below. Part0: Introduction; Part1: Glossary; Part2: Physical, chemical and biochemical methods; Part3: Radiological methods; Part4: Microbiological methods; Part5: Biological methods; Part6: Sampling. Terminology and conventions. The text of th
8、e international standard has been approved as suitable for publication as a British Standard without deviation. Some terminology and certain conventions are not identical with those used in British Standards; attention is especially drawn to the following. The comma has been used as a decimal marker
9、. In British Standards it is current practice to use a full point on the baseline as the decimal marker. In British Standards it is current practice to use the symbol “L” for litre (and in its submultiples) rather than “l”, and to use the spelling “sulphur”, etc.,instead of “sulfur”, etc. Wherever t
10、he words “this International Standard” appear, referring to this standard, they should be read as “this Section of BS6068”. The tests described in this British Standard should only be carried out in laboratories with suitable facilities and by suitably qualified persons with an appropriate level of
11、chemical expertise and knowledge of the necessary safety precautions. Standard chemical procedures should be followed throughout. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compl
12、iance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, pages1 to4 and a back cover. This standard has been updated (see copyright date) and may have had amendments incorpora
13、ted. This will be indicated in the amendment table on the inside front cover.BS6068-2.31:1987 BSI 07-1999 1 0 Introduction In water containing oxygen, most of the manganese will be present as undissolved forms, often associated with micro-organisms and as complexes with, for example, humic acid. If
14、the water is free of oxygen or strongly acidic, all manganese will be present in dissolved forms. 1 Scope and field of application This International Standard specifies a formaldoxime spectrometric method for the determination of total manganese (including dissolved, suspended and organically bound
15、manganese) in surface and drinking water. The method is applicable to the determination of manganese concentrations between0,01mg/l and5mg/l. Manganese concentrations above5mg/l may be determined after suitable dilution of the sample. For known possible interferences, see clause8. NOTEThis method is
16、 not applicable to highly contaminated waters such as industrial waste water. 2 Principle Addition of a formaldoxime solution to a test portion and spectrometric measurement of the orange-red complex at a wavelength of about450nm. If suspended or organically bound manganese is present, pretreatment
17、is required to convert manganese to forms capable of reacting with formaldoxime. The manganese formaldoxime complex is stable between pH values of9,5 and10,5, and the intensity of the colour produced is proportional to the amount of manganese present. The relationship between concentration and absor
18、bance is linear up to a concentration of5mg/l. Maximum absorbance occurs at about450nm (specific molar absorbance coefficient of11 10 3l/molcm). 3 Reagents WARNING The reagents described in3.4, 3.5.1 and3.5.3 should be regarded as special hazards. Hazardous operations should be carried out in a fume
19、 cupboard. Care must be taken to avoid ingestion or inhalation of vapours and to protect the hands, eyes and face. Gloves and goggles must be worn and any suspected skin contamination washed off immediately. Inhalation of the vapours of formaldehyde and formaldoxime will result in severe irritation
20、and oedema of the upper respiratory tract. During the analysis, use only reagents of recognized analytical grade, and only deionized water or water distilled from an all glass apparatus with a manganese content that is as low as possible. 3.1 Oxidizing reagent Either potassium peroxodisulfate (K 2 S
21、 2 O 8 ) or sodium peroxodisulfate (Na 2 S 2 O 8 ). 3.2 Sodium sulfite (Na 2 SO 3 ), anhydrous. 3.3 EDTA, tetrasodium salt, solution, c(EDTA)=0,24mol/l. Dissolve90g of disodium ethylenedinitrilotetraacetic acid (Na 2 EDTA) dihydrate (C 10 H 14 N 2 Na 2 O 8 2H 2 O) and19g of sodium hydroxide (NaOH) i
22、n water and dilute to1000ml. Alternatively, dissolve109g of tetrasodium ethylenedinitrilotetraacetic acid (Na 4 EDTA) tetrahydrate (C 10 H 12 N 2 Na 4 O 8 4H 2 O) or100g of tetrasodium ethylenedinitrilotetraacetic acid dihydrate (C 10 H 12 N 2 Na 4 O 8 2H 2 O) in water and dilute to1000ml. 3.4 Forma
23、ldoxime solution. Dissolve10g of hydroxylammonium chloride (NH 3 OHCl) in about50ml of water. Add5ml of35% (m/m) methanal (HCHO) (formaldehyde) solution (A =1,08g/ml) and dilute with water to100ml. Keep the bottle in a dark and cool place. The solution has a shelf-life of at least1month. 3.5 Hydroxy
24、lammonium chloride/ammonia solution. 3.5.1 Hydroxylammonium chloride solution, c(NH 3 OHCI)=6mol/l. Dissolve42g of hydroxylammonium chloride in water and dilute to100ml. 3.5.2 Ammonia solution, c(NH 3 )=4,7mol/l. Dilute70ml of concentrated ammonia (A=0,91g/ml) with water to200ml. 3.5.3 Preparation M
25、ix equal volumes of the ammonia solution(3.5.2) and the hydroxylammonium chloride solution(3.5.1). 3.6 Ammonium iron(II) sulfate hexahydrate solution, (NH 4 ) 2 Fe(SO 4 ) 2 6H 2 O, 700mg/l. 3.6.1 Sulfuric acid, c(H 2 SO 4 ) . 3mol/l. Carefully add170ml of concentrated sulfuric acid (A=1,84g/ml) to75
26、0ml of water. Allow to cool and dilute to1000ml. This solution is commercially available (H 2 SO 4 , A =1,19g/ml).BS6068-2.31:1987 2 BSI 07-1999 3.6.2 Preparation Dissolve700mg of ammonium iron(II) sulfate hexahydrate in water, add1ml of sulfuric acid(3.6.1) and dilute to1000ml. 3.7 Sodium hydroxide
27、 solution, c(NaOH)=4mol/l. Dissolve160g of sodium hydroxide in water and dilute to1000ml. 3.8 Manganese, standard solution, corresponding to100mg of Mn per litre. Dissolve308mg of manganese sulfate monohydrate (MnSO 4 H 2 O) in water in a1000ml one-mark volumetric flask. Add10ml of sulfuric acid(3.6
28、.1), make up to the mark with water and mix. 1ml of this standard solution contains0,1mg of Mn. Commercially available standard solutions can also be used. 4 Apparatus Usual laboratory equipment and 4.1 Spectrometer, with selectors for continuous variation (prism or grating type) or discontinuous va
29、riation (narrow band pass optical filter) capable of measuring absorbance at approximately450nm, equipped with cells of optical path lengths up to100mm (for manganese concentrations of less than0,3mg/l) and10mm (for manganese concentrations above0,3mg/l). 4.2 Glass bottles, of capacity100ml, provide
30、d with ground glass stoppers and metal clamps or with screw-caps of non-coloured plastic, suitable for autoclaving. 4.3 Autoclave or pressure cooker, capable of maintaining a temperature of120C and a pressure of200kPa. NOTE ON PREPARATION OF GLASSWARE, ETC. All glassware and sampling containers shal
31、l be washed with approximately1mol/l hydrochloric acid (HCl) and rinsed with water before use. 5 Sampling and samples WARNING Take appropriate safety precautions when acidifying samples, owing to the possibility of release of toxic gases. Collect the sample in a polyethylene, polyvinyl chloride or g
32、lass container and acidify the sample with sulfuric acid(3.6.1) until the pH is approximately, but not less than,1. This acidification minimizes adsorption of manganese on the walls of the container and also assists in the dissolution of colloidal and particulate forms of manganese. 6 Procedure 6.1
33、Test portion Take as the test portion50ml, or an accurately measured aliquot diluted to50ml, of the acidified test sample containing less than0,25mg of manganese(5mg/l). 6.2 Preparation of test solution If organically bound or suspended manganese is present, add225 25mg of oxidizing reagent(3.1) to
34、the test portion(6.1). The oxidation can be performed in one of two ways: a) autoclave the mixture for30min in a bottle(4.2); cool and add approximately0,5g of sodium sulfite(3.2) to reduce oxidizing substances; b) boil the mixture in a100ml conical flask or beaker for about40min; cool and transfer
35、the mixture to a50ml one-mark volumetric flask, make up to the mark with water and add approximately0,5g of sodium sulfite(3.2) to reduce oxidizing substances. Autoclaving is preferable in the case of samples containing humic acids. If the procedure is not to be continued immediately, the pretreated
36、 sample may be kept overnight. NOTEAny turbidity and colour is destroyed during the pretreatment. If experience has shown that this pretreatment stage is not required, for example in most cases for drinking water, it may be omitted. 6.3 Blank test Carry out a blank test in parallel with the determin
37、ation, replacing the test portion by50ml of water. If the absorbance of the blank test differs significantly from the extrapolated absorbance of the zero member(6.4.4), the reasons for this difference shall be investigated. 6.4 Calibration 6.4.1 Preparation of the set of calibration solutions Range
38、A: 0 to0,5mg/l manganese Dilute5 0,05ml of standard manganese solution(3.8) to1000ml with water in a1000ml one-mark volumetric flask. To a series of five50ml one-mark volumetric flasks add0,10,20,30 and40ml of this diluted manganese solution and dilute to the mark with water. This gives calibration
39、standard solutions of0;0,1;0,2;0,3 and0,4mg/l of manganese.BS6068-2.31:1987 BSI 07-1999 3 Range B: 0 to5 mg/l manganese Dilute50 0,5ml of standard manganese solution(3.8) to1000ml with water in a1000ml one-mark volumetric flask. To a series of five50ml one-mark volumetric flasks add0,10,20,30 and40m
40、l of this diluted manganese solution and dilute to the mark with water. This gives calibration standard solutions of0,1,2,3 and4mg/l manganese. 6.4.2 Colour development Add1ml of ammonium iron(II) sulfate solution(3.6) and2ml of EDTA solution(3.3) to each of the solutions. After mixing, add1ml of th
41、e formaldoxime solution(3.4) and immediately add2ml of sodium hydroxide solution(3.7). Thoroughly mix the solutions and allow to stand for5 to10 min, then add, whilst mixing,3ml of hydroxylammonium chloride/ammonia solution(3.5) and leave to stand for at least1h. 6.4.3 Spectrometric measurements Bet
42、ween1 and4h after colour development, measure the absorbances of the solutions using the spectrometer at a wavelength of450nm against water as reference. For calibration solutions in range A(0 to0,5mg/l manganese) use cells of100mm optical path length, and for range B(0to5mg/l manganese) use cells o
43、f10mm optical path length. 6.4.4 Plotting the calibration graph For each set of calibration solutions, prepare a calibration graph by plotting the manganese concentration, expressed in milligrams per litre, of the solution as abscissa against the corresponding absorbance as ordinate. It is essential
44、 that a linear calibration graph be achieved. The calibration factor, f, is the reciprocal of the slope of the calibration graph. The intercept of the calibration graph on the ordinate gives the extrapolated absorbance of the zero member of the set of calibration solutions. The calibration factor ca
45、n also be calculated by regression analysis. 6.4.5 Frequency of calibration Each graph shall be checked periodically, and especially when new reagents are used, to ensure repeatability. 6.5 Determination 6.5.1 Colour development Proceed in accordance with6.4.2, but using the test solution(6.2) inste
46、ad of the calibration solutions. If the test solution has been pretreated (see6.2), increase the amount of sodium hydroxide solution(3.7) from2 to2,5ml. 6.5.2 Spectrometric measurements See6.4.3. 7 Expression of results 7.1 Calculation The manganese concentration, A Mn , expressed in milligrams per
47、litre, is given by the formula: A Mn = f (A 1 A 0 )g where f is the calibration factor appropriate to the particular calibration graph chosen and derived as stated in6.4.4, expressed in milligrams per litre; A 1is the absorbance of the test solution(6.5.2); A 0is the extrapolated absorbance of the z
48、ero member(6.4.4); g is a factor given by the formula: V 1being the maximum volume, in millilitres, of the test portion (here50ml); V 2being the volume, in millilitres, of the test portion if an aliquot was taken. NOTEThe volume of acid added (clause5) to the sample shall be taken into consideration
49、 in the calculation. Report the results a) to the nearest0,01mg/l for manganese concentrations from0,01to1mg/l; b) to the nearest0,1mg/l for manganese concentrations greater than1mg/l. 7.2 Precision See the table. 8 Interferences 8.1 Iron(II) ions form a violet complex with formaldoxime which interferes with manganese determination. The addition of EDTA(3.3) and hydroxylammonium chloride/ammonia(3.5) reduces the interference; however, it has been shown that the best method of overcoming this effect is to add a constant known amoun
