1、 Reference number ISO 29441:2010(E) ISO 2010INTERNATIONAL STANDARD ISO 29441 First edition 2010-04-01 Water quality Determination of total nitrogen after UV digestion Method using flow analysis (CFA and FIA) and spectrometric detection Qualit de leau Dosage de lazote total aprs digestion UV Mthode p
2、ar analyse en flux (CFA et FIA) et dtection spectromtrique ISO 29441:2010(E) PDF disclaimer This PDF file may contain embedded typefaces. In accordance with Adobes licensing policy, this file may be printed or viewed but shall not be edited unless the typefaces which are embedded are licensed to and
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7、 2010 All rights reservedISO 29441:2010(E) ISO 2010 All rights reserved iiiContents Page Foreword iv Introduction.v 1 Scope1 2 Normative references1 3 Interferences 2 4 Principle2 5 Reagents.2 6 Apparatus.6 7 Sampling and sample preparation.7 8 Procedure.8 9 Evaluation.10 10 Expression of results10
8、11 Test report11 Annex A (informative) Examples of flow systems (6.1 or 6.2) for the determination of total nitrogen after inline UV digestion (2 mg/l to 20 mg/l) 12 Annex B (informative) Precision data .14 Bibliography16 ISO 29441:2010(E) iv ISO 2010 All rights reservedForeword ISO (the Internation
9、al Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been e
10、stablished has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standard
11、ization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for vo
12、ting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all su
13、ch patent rights. ISO 29441 was prepared by Technical Committee ISO/TC 147, Water quality, Subcommittee SC 2, Physical, chemical and biochemical methods. ISO 29441:2010(E) ISO 2010 All rights reserved vIntroduction Methods using flow analysis enable wet chemistry procedures to be automated and are p
14、articularly suitable for the processing of many analytes in water in large series of samples at a high analysis frequency (up to 100 samples per hour). A differentiation is made between flow injection analysis (FIA, References 12) and continuous flow analysis (CFA, Reference 3). Both methods share t
15、he feature of an automatic dosage of the sample into a flow system (manifold) where the analytes in the sample react with the reagent solutions on their way through the manifold. The sample preparation can be integrated into the manifold. The reaction product is measured in a flow detector (e.g. a f
16、low photometer). INTERNATIONAL STANDARD ISO 29441:2010(E) ISO 2010 All rights reserved 1Water quality Determination of total nitrogen after UV digestion Method using flow analysis (CFA and FIA) and spectrometric detection WARNING Persons using this International Standard should be familiar with norm
17、al laboratory practice. This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user to establish appropriate safety and health practices and to ensure compliance with any national regulatory conditions. Waste containing
18、cadmium in liquid or solid form shall be disposed of appropriately. IMPORTANT It is absolutely essential that tests conducted according to this International Standard be carried out by suitably trained staff. 1 Scope This International Standard specifies a method for the determination of total nitro
19、gen after inline UV digestion, in various types of waters, such as ground, drinking, surface, and waste waters, in mass concentrations ranging from 2 mg/l to 20 mg/l for total nitrogen, all in the undiluted sample. Other mass concentration ranges are possible, provided the upper limit of the concent
20、ration range is exactly 10 times the lower limit (e.g. 0,2 mg/l to 2,0 mg/l). The range of application can be changed by varying the operating conditions. NOTE Sea water can be analysed with changes in respect to sensitivity and adaptation of the carrier solution and calibration solutions to the sal
21、inity of the samples. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO
22、3696:1987, Water for analytical laboratory use Specification and test methods ISO 5667-3, Water quality Sampling Part 3: Guidance on the preservation and handling of water samples ISO 8466-1, Water quality Calibration and evaluation of analytical methods and estimation of performance characteristics
23、 Part 1: Statistical evaluation of the linear calibration function ISO 8466-2, Water quality Calibration and evaluation of analytical methods and estimation of performance characteristics Part 2: Calibration strategy for non-linear second-order calibration functions ISO 13395, Water quality Determin
24、ation of nitrite nitrogen and nitrate nitrogen and the sum of both by flow analysis (CFA and FIA) and spectrometric detection ISO 29441:2010(E) 2 ISO 2010 All rights reserved3 Interferences Samples with extreme pH values and samples with a high buffering capacity are prone to interferences. It is ad
25、visable to analyse several dilutions of the sample and to check the results for consistency. High concentrations of organic substances can cause problems as the oxidation capacity may not be sufficient. For samples containing more than 100 mg/l of total organic carbon (TOC), reduced yields in the de
26、termination of nitrogen may arise. If the presence of more than 100 mg/l of TOC is suspected, the sample should be run with several dilutions in order to check for consistency, or standard addition techniques should be applied. If the sample comprises larger particles (diameter, d 50 m), a homogenis
27、ation device (6.3.3) is necessary. In sea water samples, high concentrations of calcium and magnesium may occur. In an alkaline medium, magnesium hydroxide or other hydroxides or calcium carbonate may be formed which interfere with the UV digestion. 4 Principle The sample is pretreated with a buffer
28、ed peroxodisulfate solution and thermal UV radiation. Nitrate is formed and determined either by flow injection analysis (FIA) or by continuous flow analysis (CFA). With FIA, the sample is fed into a continuously flowing buffer solution (carrier stream) by means of an injection valve, or, when apply
29、ing CFA, it is continuously mixed with this buffer solution. Nitrate in the sample is reduced with metallic cadmium to nitrite (Reference 4). Subsequently a phosphoric acid reagent solution also flowing continuously is admixed. Nitrite resulting from the reduction of nitrate diazotises sulfanilamide
30、 in acidic solution to the diazonium salt which is then coupled with N-(1-naphthyl)ethylenediamine to form a red soluble dye(see ISO 13395 and Reference 5). 5 Reagents During the analysis, unless otherwise stated, use only reagents of recognised analytical grade. Check the blank value of the reagent
31、s regularly (see 8.4). 5.1 General reagents 5.1.1 Water, complying with ISO 3696:1987, grade 1. 5.1.2 Phosphoric acid, (H 3 PO 4 ) = 1,71 g/ml. 5.1.3 Potassium peroxodisulfate, K 2 S 2 O 8 . 5.1.4 Sodium hydroxide, NaOH. 5.1.5 Titanium tetrachloride, TiCl 4 , liquid, commercially available. 5.1.6 Su
32、lfanilamide, 4-aminobenzenesulfonamide, C 6 H 8 N 2 O 2 S. 5.1.7 N-(1-Naphthyl)ethylenediamine dihydrochloride, N-(1naphthyl)-1,2-diaminoethane dihydrochloride, C 12 H 14 N 2 2HCl. 5.1.8 Sodium nitrite, NaNO 2 , dried to constant mass at 150 C. 5.1.9 Potassium nitrate, KNO 3 , dried to constant mass
33、 at 150 C. 5.1.10 Imidazole, C 3 H 4 N 2 . ISO 29441:2010(E) ISO 2010 All rights reserved 35.1.11 Hydrochloric acids. 5.1.11.1 Hydrochloric acid I, concentrated, w(HCI)= 37 %. 5.1.11.2 Hydrochloric acid II, c(HCl) = 4 mol/l. 5.1.11.3 Hydrochloric acid III, c(HCI) 0,1 mol/l. 5.1.12 Dichloromethane, C
34、H 2 Cl 2 . 5.1.13 Copper(II) sulfate solution I, (CuSO 4 5H 2 O) = 2,5 g/l. 5.1.14 Copper(II) sulfate solution II, (CuSO 4 5H 2 O) = 20 g/l. 5.1.15 Boric acid, H 3 BO 3 . 5.1.16 Sulfuric acid I, (H 2 SO 4 ) = 1,84 g/ml. 5.1.17 Sulfuric acid II, c(H 2 SO 4 ) = 1 mol/l. 5.1.18 Urea, CO(NH 2 ) 2 . 5.1.
35、19 Cadmium (Cd) granulate, grain size e.g. 0,3 mm to 1,5 mm (for FIA preferably 0,3 mm to 0,8 mm). A minimum reduction capacity of 90 % shall be reached (see 6.1.4 and 6.2.4). 5.1.20 Imidazole stock solution, c(C 3 H 4 N 2 ) = 1 mol/l (Figure A.1, R1). Dissolve 68,1 g of imidazole (5.1.10) in approx
36、imately 800 ml of water (5.1.1) in a 1 l beaker. While stirring with a magnetic stirrer, add hydrochloric acid I (5.1.11.1) and adjust the pH to 7,5 using a pH electrode (6.3.2). Transfer to a 1 000 ml one-mark volumetric flask. Make up to the mark with water (5.1.1). The solution is stable for 4 we
37、eks if kept in a brown glass bottle at room temperature. 5.1.21 Urea stock solution, (N) = 1 000 mg/l. In a 500 ml one-mark volumetric flask, dissolve 1,071 7 g of urea (5.1.18) in water (5.1.1). Add 0,5 ml of dichloromethane (5.1.12) for preservation. Make up to the mark with water. The solution is
38、 stable for 1 year if kept at (4 2) C. 5.1.22 Urea working solution, (N) = 20 mg/l. Dilute 5 ml of urea stock solution (5.1.21) in a 250 ml one-mark volumetric flask with water (5.1.1). Acidify the solution with sulfuric acid II (5.1.17) to pH u 2. The solution is stable for 1 month if kept at (4 2)
39、 C. 5.1.23 Buffered copper(II) sulfate solution. Mix 20 ml of the copper(II) sulfate solution II (5.1.14) and 20 ml of the imidazole stock solution (5.1.20) in a 50 ml beaker. Prepare the solution freshly before use. ISO 29441:2010(E) 4 ISO 2010 All rights reserved5.1.24 Reagent solution, (Figure A.
40、1, R2 and Figure A.2, R1; see also ISO 13395). In a 500 ml one-mark volumetric flask, dissolve 5 g of sulfanilamide (5.1.6) and 0,5 g of N-(1-naphthyl)ethylenediamine dihydrochloride (5.1.7) in water (5.1.1), add 75 ml of phosphoric acid (5.1.2). Make up to the mark with water (5.1.1). Stored in a b
41、rown glass bottle, the solution is stable for 1 month. NOTE The solutions of sulfanilamide (5.1.6) and N-(1-naphthyl)ethylenediamine dihydrochloride (5.1.7) can also be prepared separately and dosed into the manifold by different lines. Prior to use, degas solution R2 for FIA, e.g. by membrane filtr
42、ation (vacuum). 5.1.25 Nitrite(N) stock solution, (N) = 100 mg/l. In a 1 000 ml one-mark volumetric flask, dissolve 492,6 mg of sodium nitrite (5.1.8) in water (5.1.1). Make up to the mark with water (5.1.1). This solution is stable for at least 2 weeks if kept in a stoppered glass bottle at (4 2) C
43、. 5.1.26 Nitrite(N) solution, (N) = 20 mg/l. Pipette 20 ml of the nitrite stock solution (5.1.25) into a 100 ml one-mark volumetric flask. Make up to the mark with water (5.1.1). Prepare the solution freshly before use. 5.1.27 Nitrate(N) solution, (N) = 200 mg/l. In a 100 ml one-mark volumetric flas
44、k, dissolve 144,4 mg of potassium nitrate (5.1.9) in water (5.1.1). Make up to the mark with water (5.1.1). Acidify the standard solutions with sulfuric acid II (5.1.17) to pH 2. The solution is stable for at least 1 month. 5.1.28 Calibration solutions. Prepare calibration solutions by diluting the
45、nitrate(N) solution (5.1.27). At least five calibration solutions are recommended. For example, proceed according to Table 1 for the preparation of 10 calibration solutions. Prepare all calibration solutions immediately before measurement. 5.1.29 Blank solution, for diluting the samples and measurin
46、g the blanks (Clauses 7 and 8). Acidify water to pH 2 with sulfuric acid II (5.1.17). 5.2 Additional reagents for FIA (see 6.1) 5.2.1 FIA oxidising reagent I (Figure A.1, R3). In a 250 ml one-mark volumetric flask, dilute 6,8 ml of sulfuric acid II (5.1.17) in about 200 ml of water (5.1.1). Dissolve
47、 7,2 g of boric acid (5.1.15) and 10,1 g of potassium peroxodisulfate (5.1.3) and make up to the mark with water (5.1.1). The solution is stable for 1 day if kept at 2 C to 8 C. Do not hermetically close the reagent container. ISO 29441:2010(E) ISO 2010 All rights reserved 5Table 1 Preparation of th
48、e calibration solutions for total nitrogen(N) Nitrate(N) concentration Volume of nitrate(N) solution (5.1.27) diluted with water (5.1.1) to 100 ml mg/l ml 2 1 4 2 6 3 8 4 10 5 12 6 14 7 16 8 18 9 20 10 5.2.2 FIA oxidising reagent II (Figure A.1, R4). In a 250 ml one-mark volumetric flask, dissolve 6
49、,0 g of sodium hydroxide (5.1.4) and 10,1 g of potassium peroxodisulfate (5.1.3) in about 200 ml of water (5.1.1). Make up to the mark with water (5.1.1). The solution is stable for 1 week if kept at 2 C to 8 C. Do not hermetically close the reagent container. 5.2.3 FIA carrier solution (Figure A.1, C). Mix 1 000 ml of water (5.1.1) with 100 l of copper(II) sulfate solution I (5.1.13). Prepare the solution freshly before use. Prior to use, degas the solution, e.g.
