DIN 38405-35-2004 German standard methods for the examination of water waste water and sludge - Anions (group D) - Part 35 Determination of arsenic - Method by graphite furnace ato.pdf

1、September 2004DEUTSCHE NORM English price group 9No part of this translation may be reproduced without prior permission ofDIN Deutsches Institut fr Normung e. V., Berlin. Beuth Verlag GmbH, 10772 Berlin, Germany,has the exclusive right of sale for German Standards (DIN-Normen).ICS 13.060.50!$LV)“141

2、5106www.din.deDDIN 38405-35German standard methods for the examination of water, waste waterand sludge Anions (group D) Part 35: Determination of arsenic by graphite furnace atomic absorptionspectrometry (GF-AAS) (D 35)Deutsche Einheitsverfahren zur Wasser-, Abwasser- und Schlammuntersuchung Anionen

3、 (Gruppe D) Teil 35: Bestimmung von Arsen Verfahren mittelsGraphitrohrofen-Atomabsorptionsspektrometrie (GF-AAS) (D 35)www.beuth.deIn case of doubt, the German-language original should be consulted as the authoritative text.Translation by DIN-Sprachendienst.Document comprises 18 pagesDIN 38405-35:20

4、04-09 2 Contents Page Foreword3 1 Scope 3 2 Normative references 3 3 Terms and definitions .4 4 Principle4 5 Interferences 4 6 Designation 5 7 Reagents.5 7.1 General5 8 Apparatus .7 8.1 General7 9 Sampling.8 10 Sample pretreatment .8 10.1 Pretreatment for determining dissolved arsenic content8 10.2

5、Pretreatment for determining total arsenic content.8 10.2.1 General8 10.2.2 Open-system digestion .8 10.2.3 Digestion in a closed, microwave-assisted heating system .8 11 Procedure .9 11.1 General9 11.2 Standard calibration method. 10 11.3 Standard addition method . 10 12 Evaluation 11 12.1 Standard

6、 calibration method. 11 12.2 Standard addition method . 11 13 Expression of result . 11 14 Test report . 12 15 Results of interlaboratory testing . 12 Annex A (informative) Trade names of suitable materials for pressure digestion vessels as in subclause 10.2.3 . 14 Annex B (informative) Wavelength a

7、nd modifier for determining arsenic by graphite furnace atomic absorption spectrometry in the presence of aluminium contents exceeding 50 mg/l (see Table 1) . 15 Annex C (informative) Explanatory notes 16 DIN 38405-35:2004-09 3 Foreword This standard has been prepared jointly with the Wasserchemisch

8、e Gesellschaft (Water Chemistry Society), a specialist group of the Gesellschaft Deutscher Chemiker (German Chemists Society) (see Annex C). Expert assistance and specialized laboratories will be required to perform the analyses specified in this standard. Existing safety instructions shall be obser

9、ved. When using the standard, a check shall be made on a case-by-case basis as to whether and to what extent additional boundary conditions have to be specified. See Annex C for a list of other parts of DIN 38405 and of groups A to T of the German standard methods. Annexes A to C are informative. In

10、troduction Arsenic can have valencies of 3, 0, +3 and +5. It occurs in water in organic and inorganic compounds. CAUTION Users of this standard should be familiar with standard laboratory practice. It is not claimed that all the safety problems associated with the use of the standard have been dealt

11、 with exhaustively here. It is therefore the responsibility of the user to take appropriate safety precautions and to ensure that these comply with national regulations. 1 Scope The method specified in this standard serves to determine arsenic in water in concentrations by mass ranging from 2 g/l to

12、 100 g/l if a volume of 20 l is injected. The limit of determination is often lower and shall be determined in each laboratory by calibration experiments. The method is also suitable for higher concentrations if the sample is diluted or a smaller volume of the test solution is taken. Arsenic in slud

13、ge and sediments can be determined using suitable digestion methods (see DIN EN 13346). 2 Normative references This standard incorporates, by dated or undated reference, provisions from other publications. These normative references are cited at the appropriate places in the text, and the titles of

14、the publications are listed below. For dated references, subsequent amendments to or revisions of any of these publications apply to this standard only when incorporated in it by amendment or revision. For undated references, the latest edition of the publication referred to applies (including amend

15、ments). DIN 12691, Class AS fast delivery one-mark bulb pipettes, with a waiting time of 15 seconds, for laboratory use DIN 38402-11, German standard methods for the examination of water, waste water and sludge General information (group A) Sampling of wastewater (A 11) DIN 38402-12, German standard

16、 methods for the examination of water, waste water and sludge General information (group A) Sampling from stagnant waters (A 12) DIN 38402-13, German standard methods for the examination of water, waste water and sludge General information (group A) Sampling from aquifers (A 13) DIN 38405-35:2004-09

17、 4 DIN 38402-14, German standard methods for the examination of water, waste water and sludge General information (group A) Sampling of untreated water and drinking water (A 14) DIN 38402-15, German standard methods for the examination of water, waste water and sludge General information (group A) S

18、ampling from flowing waters (A 15) DIN 38402-51, German standard methods for the examination of water, waste water and sludge General information (group A) Calibration of analytical methods, evaluation of analytical results and linear calibration functions used to determine the performance character

19、istics of analytical methods (A 51) DIN 51401-1, Atomic absorption spectrometry (AAS) Terminology Supplement 1 to DIN 51401-1, Atomic absorption spectrometry (AAS) Terminology, explanatory notes DIN EN 13346, Characterization of sludges Determination of trace elements and phosphorus Aqua regia extra

20、ction methods DIN EN ISO 1042, Laboratory glassware One-mark volumetric flasks (ISO 1042:1998) DIN EN ISO 5667-3, Water quality Sampling Part 3: Guidance on the preservation and handling of water samples (ISO 5667-3:2003) DIN EN ISO 5667-13, Water quality Sampling Part 13: Guidance on sampling of sl

21、udges from sewage and water treatment works (ISO 5667-13:1997) DIN ISO 3696, Water for analytical laboratory use Specification and test methods (ISO 3696:1987) DIN ISO 8466-2, Water quality Calibration and evaluation of analytical methods and estimation of performance characteristics Part 2: Calibra

22、tion strategy for non-linear second order calibration functions (ISO 8466-2:2001) 3 Terms and definitions See DIN 51401-1 and Supplement 1 to DIN 51401 for concepts associated with atomic absorption spectrometry. 4 Principle The test solution and a modifier (7.7) are injected into the electrically h

23、eated graphite furnace of an atomic absorption spectrometer, thermally pretreated and atomized. The time-integrated absorbance (peak area) is measured at a wavelength of 193,7 nm with a slit width of less than 1 nm. 5 Interferences Interferences due to non-specific absorption can largely be avoided

24、by using a background correction that employs the Zeeman effect or by using a continuum source. Depending on the type of background correction, the following ions do not interfere with the determination provided their concentrations by mass do not exceed those given in Table 1. DIN 38405-35:2004-09

25、5 Table 1 Maximum concentrations of interfering ions Interfering ion Zeeman background correction mg/l Continuum source/background correction mg/l Calcium 1 000 1 000 Chloride 1 000 1 000 Potassium 1 000 1 000 Copper 1 000 1 000 Magnesium 1 000 1 000 Sodium 1 000 1 000 Sulfate 1 000 1 000 Zinc 1 000

26、 1 000 Chromium 500 100 Cobalt 500 Iron 500 100 Nickel 500 Phosphate 500 100 Aluminium 50 10 However, combinations of the above ions may result in interferences even at lower concentrations. If the matrix effect of the water sample is not known, the standard addition method described in subclause 11

27、.3 shall be used. NOTE Spectral interferences due, for example, to chromium, cobalt, iron, nickel, phosphate and aluminium cannot be eliminated even by the addition method if a continuum source is used for background correction. Interference due to aluminium can be avoided by using a different wavel

28、ength and a different modifier (see Annex B). 6 Designation Designation of the method of determining arsenic by graphite furnace atomic absorption spectrometry (D 35): Method DIN 38405 D 35 7 Reagents 7.1 General Only analytical grade reagents shall be used for sample preparation and for making up s

29、olutions and the water used shall be grade 1 water as in DIN ISO 3696. The arsenic content of the water and of the reagents shall be negligible compared with the lowest concentration to be determined. The following reagents shall be used. 7.2 Hydrochloric acid, HCl, of density 1,16 g/ml. DIN 38405-3

30、5:2004-09 6 7.3 Nitric acid, HNO3, of density 1,40 g/ml. 7.4 0,2 mol/l nitric acid, HNO3. 7.5 30 % (m/m) hydrogen peroxide (dihydrogen dioxide), H2O2. 7.6 Sodium hydroxide, NaOH. 7.7 Modifier 7.7.1 Palladium nitrate solution, prepared by dissolving 300 mg of palladium, Pd, metal powder in 1 ml of ni

31、tric acid (7.3) and 10 l of hydrochloric acid (7.2) while carefully heating, and making up to 100 ml with water (7.1). 7.7.2 Magnesium nitrate solution, prepared by dissolving 200 mg of anhydrous magnesium nitrate, Mg(NO3)2, in water and making up to 100 ml with water (7.1). 7.7.3 Ready-to-use modif

32、ier, prepared by mixing equal volumes of the palladium nitrate solution (7.7.1) and magnesium nitrate solution (7.7.2). 10 l of this solution contain 15 g of palladium nitrate and 10 g of magnesium nitrate. The modifier may also be prepared from commercial concentrates. NOTE For some types of graphi

33、te furnace, much smaller amounts of modifier reagents may be used. 7.8 Arsenic stock solution no. 1, of density 1 000 mg/l, prepared by quantitatively transferring enough of the contents of an ampoule of a commercial arsenic standard to give a final concentration of (1,000 0,002) g/l to a 1 000 ml v

34、olumetric flask, adding 5 ml of hydrochloric acid (7.2), making up to the mark with water (7.1) and then transferring the solution to a polyethylene or borosilicate bottle for storage. This solution will be stable for at least one year. Commercial ready-to-use arsenic standards containing (1,000 0,0

35、02) g/l of arsenic may also be used. In both cases the manufacturers information on the shelf life of the solutions shall be taken into account. The arsenic stock solution may also be prepared by transferring 1,534 g of diarsenic pentoxide (As2O5) or 1,320 g of diarsenic trioxide (As2O3) to a 1 000

36、ml volumetric flask, adding 2 g of sodium hydroxide (7.6), dissolving in water (7.1), making up to the mark with water and transferring the solution to a polyethylene or borosilicate bottle for storage. This solution will be stable for at least one year. 7.9 Arsenic stock solution no. 2, of density

37、100 mg/l, prepared by pipetting 10 ml of arsenic stock solution no. 1 (7.8) into a 100 ml volumetric flask, adding 1 ml of hydrochloric acid (7.2) and making up to the mark with water (7.1). Smaller volumes may also be used. The solution will be stable for a few weeks. 7.10 Standard arsenic solution

38、 no. 1, of density 1 000 g/l, prepared by pipetting 1 ml of arsenic stock solution no. 2 (7.9) into a 100 ml volumetric flask, adding 1 ml of hydrochloric acid (7.2) and making up to the mark with water (7.1). Smaller volumes may also be used. The solution will be stable for a few weeks. 7.11 Standa

39、rd arsenic solution no. 2, of density 200 g/l, prepared by pipetting 20 ml of standard arsenic solution no. 1 (7.10) into a 100 ml volumetric flask, adding 1 ml of hydrochloric acid (7.2) and making up to the mark with water (7.1). Smaller volumes may also be used. The solution will only be stable f

40、or a few days. 7.12 Arsenic reference solutions Prepare at least five reference solutions from standard arsenic solution no. 1 (7.10) to suit the expected working range. For example, if the expected range is 10 g/l to 50 g/l, adopt the following procedure. Pipette standard arsenic solution no. 1 (7.

41、10) into a series of five 100 ml volumetric flasks so that they contain 1 ml, DIN 38405-35:2004-09 7 2 ml, 3 ml, 4 ml and 5 ml, respectively, of the solution, add 1 ml of nitric acid (7.3), make the solutions up to the mark with water (7.1) and mix thoroughly. The concentrations of the reference sol

42、utions thus obtained will be 10 g/l, 20 g/l, 30 g/l, 40 g/l and 50 g/l of arsenic, respectively. Make them up immediately before use. 7.13 Blank solution, prepared by pipetting 1 ml of nitric acid (7.3) into a 100 ml volumetric flask and making up to the mark with water (7.1). If the sample is diges

43、ted, pretreat the blank solution in the same way (see clause 10). 8 Apparatus 8.1 General Immediately before use, clean the glassware with hot, dilute nitric acid (7.4) and then rinse it with water (7.1). The following equipment shall be used. 8.2 Atomic absorption spectrometer, with background corr

44、ection and radiation source for arsenic determination. NOTE The use of background correction employing the Zeeman effect is recommended. 8.3 Graphite furnace, with control unit. 8.4 Pyrolytically coated graphite tube, with platform. 8.5 Argon supply system. 8.6 Volumetric flasks, of nominal capaciti

45、es 10 ml, 100 ml and 1 000 ml (e.g. DIN EN ISO 1042 A 100 C volumetric flasks). 8.7 One-mark bulb pipettes, of nominal capacities 1 ml, 2 ml, 3 ml, 4 ml, 5 ml, 10 ml, 20 ml and 50 ml (e.g. DIN 12691 VPAS 1 pipettes). 8.8 Microlitre pipettes or automatic diluters, for volumes in the range from 100 l

46、to 10 ml. 8.9 Reaction containers, made of inert material (e.g. perfluoroalkanes), suitable for open or closed digestion, of nominal capacity 250 ml or 100 ml, suitable for safe use in the temperature range. 8.10 Magnetic followers, boiling stones, PTFE-coated (PTFE: polytetrafluoroethylene). 8.11 H

47、eating device (e.g. electrical hotplate, sandbath). 8.12 Microwave-assisted heating system as an alternative to the above, either temperature- or power-controlled, equipped with a pressure gauge. The pressure and temperature measurements shall be precise enough for the system to be used reliably in

48、the specified range. This shall also include traceability of the measurement values to national or international standards for pressure or temperature. The microwave unit shall provide uniform energy distribution throughout the samples. The microwave unit shall be well ventilated and protected from

49、corrosion. Additionally, the air circulation in pressure-controlled systems shall be high enough for ambient temperature to be maintained in the unit. DIN 38405-35:2004-09 8 9 Sampling Follow the instructions given in DIN 38402-11 to DIN 38402-15 and DIN EN ISO 5667-3 when sampling. Collect the samples in glass, silica or plastic containers. Follow the instructions given in DIN EN ISO 5667-13 when collecting sludge and sediment samples. 10 Sample pretreatment 10.1 Pretreatment for determining dissolved