ISO-13395-1996.pdf
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1、INTERNATIONAL STANDARD IS0 13395 First edition 1996-07-I 5 Water quality - Determination of nitrite nitrogen and nitrate nitrogen and the sum of both by flow analysis (CFA and FIA) and spectrometric detection Qua/it see 5.1 and 5.2). 4.13 lmidazole stock solution, c = 0,25 mol/l. 4 Reagents If not s
2、tated otherwise, only reagents of recognized analytical grade and water according to grade 1 of IS0 3696 shall be used. The blank value of the re- agents shall be checked regularly (see 9.3). 4.1 Phosphoric acid (HsPO,), p = 1.71 g/ml. 4.2 Sulfanilamide (4-aminobenzenesulfonamide, C,H,N,O,S). Dissol
3、ve, in a beaker of nominal capacity 1 litre, 17,0 g of imidazole (4.6) in approximately 900 ml of water. While stirring with a magnetic stirrer, add hydrochloric acid I (4.7) and adjust, with the help of a pH electrode, the pH to 7.5. Transfer to a volumetric flask, of nominal capacity 1 000 ml, and
4、 dilute to volume with water. The solution is stable for 4 weeks if kept in a brown glass bottle at room temperature. 4.3 /V-(1-naphthyl)ethylenediaminedihydrochloride N-(1 -naphthyl)-1,2-diaminoethanedihydrochloride), W, this solution is stable. 4.10 Copper sulfate solution II, p(CuSO,.5H,O) = 20 g
5、/l; this solution is stable. Prepare the solutions, containing the surfactant (4.111, freshly before use. Prior to use, solutions C and B for FIA shall be degassed, for example by membrane filtration (vac- uum). Copyright International Organization for Standardization Provided by IHS under license w
6、ith ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/19/2007 05:51:17 MDTNo reproduction or networking permitted without license from IHS -,-,- Q IS0 IS0 13395:1996(E) 1 rable 1 - Options for preparing the solutions C and B in figures A.l, B.l and C.l Method Parameter Content of
7、 Content of solution C solution B isee figures (see figures A.l, B.l and A.1, B.l and C.1) C.1) FIA Nitrite Water WaterI) Buffer (4.14) ) No solution Bl) CFA Nitritelnitratc Buffer (4.14) Buffer (4.14) Nitrite “C” is not Waterl),2) necessary Buffer (4.14) ),2) No solution Bl),Z) Nitrite/ this interf
8、erence can be pre- vented by a dialysis of the sample, if need be in the online process. (See 9 in annex D.) 9 Procedure 9.1 Preparation, activation and checking of the cadmium reductor 9.1.1 Cadmium column with granulate Place a sufficient quantity of the cadmium granulate (4.12) to fill the column
9、 (see 5.1) in a beaker (5.5) of nominal capacity 25 ml. Stir with hydrochloric acid II (4.8) until the surface of the granulates shows a met- allic shine. Remove the acid by washing with water. Decant the water and stir the granulate twice for ap- proximately 2 min with copper sulfate solution II (4
10、.10). The surface of the granulate will turn black. Decant and carefully wash with water. Fill the column with the granulate, avoiding air bubbles and large cavities, and stopper the ends of the column (e.g. with glass wool). Copyright International Organization for Standardization Provided by IHS u
11、nder license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/19/2007 05:51:17 MDTNo reproduction or networking permitted without license from IHS -,-,- 0 IS0 IS0 13395:1996(E) Assemble the column in the flow system, and activate the reductor by applying nitrate(N) solution
12、 I (4.21) or II (4.22) three times. Repeatedly measure the calibration solution (4.23) which has, for the respective working range, the highest permissible nitrite/nitrate(N) concentration (2 mg/l or 20 mg/l, respectively), until stable results are obtained. NOTE 8 The cadmium column can be stored,
13、free from air bubbles, in the imidazole stock solution (4.13). Prior to re-use, the column should be stabilized and activated as described above. 9.1.2 Cadmium tube Using the syringe (5.61, aspirate approximately 5 ml of the buffered copper sulfate solution (4.16) into the cadmium tube (see 5.2) and
14、 allow to react for 5 min. Repeat the procedure, avoiding air bubbles. Using the syringe, aspirate approximately 20 ml of imidazole stock solution (4.13) through the tube and allow to react, avoiding air bubbles. Assemble the column in the flow system, activate and stabilize as described in 9.1 .I.
15、NOTE 9 The cadmium tube can be stored, free from air bubbles, in the imidazole stock solution (4.13). Prior to measurement, stabilize or treat, if required, (see 9.1.3) with buffered copper sulfate solution (4.16). 9.1.3 Checking the reduction capacity applies to the nitrate(N) or the nitrite/nitrat
16、e(N) determination only1 Sequentially analyse a nitrate(N) and a nitrite(N) sol- ution with a nitrogen mass concentration of 2 mg/l each for the nitrite/nitrate(N) working range II, or of 20 mg/l each for the nitrite/nitrate(N) working range I, and compare the measured values obtained. Transport rea
17、gent solutions (4.17) through the flow system with a built-in cadmium reductor and allow the baseline to stabilize. For example, to check the nitrite/nitrate(N) working range I, use the nitrite(N) solution I (4.19) and the nitrate(N) solution II (4.22). If the measured value for nitrate(N) is less t
18、han 90 % of the measured nitrite(N) value, appropriate meas- ures according to 9.1 .I and 9.1.2 shall be taken to obtain a reduction capacity of at least 90 %. Check the reduction capacity again, prior to the analysis of each series of samples. 9.2 Preparation for measurement Assemble the flow syste
19、m according to the method of determination desired (FIA or CFA, determination of nitrite/nitrate(N) or nitrite(N); see figures A.l, B.l and Cl). Prior to measurement of nitrite, continuously run the reagent solutions for approximately 10 min through the flow system. For the determination of nitrite/
20、nitrate(N), run the reagent solutions through the system for approximately 10 min without the Cd reductor and after that for approximately 10 min with the Cd reductor. Record and zero the base absorbance. The system is ready when the baseline no longer shows any drift. A satisfactory signal-noise re
21、lation should be obtained. Then perform the reaction steps in the sequence of 9.3 to 9.5. 9.3 Monitoring the blank of the reagents Allow the baseline to stabilize Instead of the buffer solution B (4.15) and the reagent solution R1 (4.17) transport water for 2 min and record changes in the measuring
22、signal. If the absorbance changes by more than 0,015 per 10 mm path length, either the water being used or the reagent solutions may be contamined. Take ap- propriate measures to eliminate the interference. Then transport the reagent solutions again. 9.4 Calibration Select the respective working ran
23、ge for nitrite(N) or nitrite/nitrate(N) and prepare the calibration solutions (4.23) for the selected working range. Each working range requires its own calibration. Calibrate by sequentially adding the calibration sol- utions and the blank solution. Prior to the calibration, zero the instrument, if
24、 necessary following the manufacturer s instructions. Determine the measured values from the calibration solutions used while following the manufacturer s in- structions, as long as they do not contradict the specifications of this International Standard. The test conditions for the calibration and
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