SANS 6168-2010 Water - Pretreatment for metal analysis《水 金属分析的预处理》.pdf

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3、damage whatsoever than may result from the use of this material or the information contain therein, irrespective of the cause and quantum thereof. ISBN 978-0-626-24443-9 SANS 6168:2010Edition 1.2SOUTH AFRICAN NATIONAL STANDARD Water Pretreatment for metal analysis Published by SABS Standards Divisio

4、n 1 Dr Lategan Road Groenkloof Private Bag X191 Pretoria 0001Tel: +27 12 428 7911 Fax: +27 12 344 1568 www.sabs.co.za SABS SANS 6168:2010 Edition 1.2 Table of changes Change No. Date Scope Amdt 1 2004 Amended to change the designation of SABS standards to SANS standards and to update referenced stan

5、dards. Amdt 2 2010 Amended to update referenced standards. Foreword This South African standard was approved by National Committee SABS SC 147A, Water Water sampling and analysis, in accordance with procedures of the SABS Standards Division, in compliance with annex 3 of the WTO/TBT agreement. This

6、document was published in April 2010. This document supersedes SANS 6168:2004 (edition 1.1). A vertical line in the margin shows where the text has been technically modified by amendment No. 2. SANS 6168:2010 Edition 1.2 1 Water Pretreatment for metal analysis 1 Scope and field of application This s

7、tandard specifies a method of preparing water and wastewater samples for analysis for the constituent forms of metals. The method is only applicable to the preparation of samples for analysis in accordance with test methods that specifically identify this method for pretreatment purposes. 2 Normativ

8、e 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. Information on currently valid natio

9、nal and international standards can be obtained from the SABS Standards Division. Amdt 1 SANS 111/ISO 835, Laboratory glassware Graduated pipettes. Amdt 1; amdt 2 SANS 112/ISO 648, Laboratory glassware Single volume pipettes. Amdt 1 SANS 115/ISO 385, Laboratory glassware Burettes. Amdt 1; amdt 2 SAN

10、S 128/ISO 1042, Laboratory glassware One-mark volumetric flasks. Amdt 1 SANS 3696/ISO 3696, Water for analytical laboratory use Specification and test methods. 3 Definitions The constituent forms of metals are defined as follows: 3.1 total metal concentration of metal in both the soluble and the ins

11、oluble state as determined after vigorous digestion of the sample or as determined by the summation of the suspended and the dissolved metal concentrations 3.2 suspended metal concentration of metal in the insoluble state as determined after vigorous digestion of the retained residue on a 0,45 m mem

12、brane filter after filtration of the sample, or as determined by difference between the total and dissolved metal concentrations SANS 6168:2010 Edition 1.2 2 3.3 dissolved metal concentration of metal in the soluble state as determined on the acidified filtrate, acidification being performed only af

13、ter the sample is filtered through a membrane filter of pore size 0,45 m, or as determined by difference between the total and suspended metal concentrations 4 Reagents NOTE Unless otherwise specified, only use reagents of analytical reagent grade. 4.1 Nitric acid (HNO3) Concentrated (d at 25 /25 C

14、= 1,42). 4.2 Dilute nitric acid 1+1 HNO3. 4.3 Dilute hydrochloric acid 1+1 HCl. 5 Apparatus 5.1 Membrane filter, of pore size 0,45 m. 5.2 Filter apparatus, consisting of a detachable funnel and a base unit between which the filter is seated on a sintered glass frit or stainless steel mesh. 5.3 Buchn

15、er flask. 5.4 Heating mantle, hotplate and steam bath. 5.5 Fume hood. 5.6 Kjeldahl flask, 300 mL capacity. 5.7 Glassware. Where applicable, only use burettes, pipettes and volumetric flasks that comply with the requirements for class A items as specified in SANS 111, SANS 112, SANS 115 and SANS 128,

16、 as relevant. Amdt 1; amdt 2 5.8 Acid-washed glassware. Wash all glassware used during the digestion procedures with the dilute nitric acid (see 4.2). 6 Procedure NOTE 1 Preserve or analyse the unpreserved sample within 48 h of sampling. NOTE 2 Unless otherwise specified, only use water that complie

17、s with the requirements of SANS 3696. SANS 6168:2010 Edition 1.2 3 6.1 Preservation 6.1.1 If suspended or dissolved metal is required, pretreat the sample by filtration and acidification of the residue or filtrate as described in 6.3 or 6.4. NOTE If the sample is not filtered prior to acidification,

18、 it will not be possible to determine the suspended or dissolved metal forms. 6.1.2 If total metal is required, preserve the sample by acidifying it to a pH value 2, using 1,5 mL of HNO3 (see 4.1) per litre of sample. If the sample has a high buffering capacity, it may be necessary to add more HNO3(

19、see 4.1) until a pH value 2 is achieved. Note the volume of HNO3added for preservation, and correct the analytical result if the potential analytical error due to dilution exceeds 0,5 %. 6.2 Pretreatment for total metal Use one of the following digestion procedures: 6.2.1 Nitric acid single stage di

20、gestion If the sample is a water or clear wastewater sample, a single stage nitric acid digestion should suffice. 6.2.1.1 Transfer 100 mL of sample to a 250 mL conical flask. Add a few anti-bump beads. 6.2.1.2 Using a safety pipette, slowly add, while stirring, 5,0 mL of the HNO3 (see 4.1). 6.2.1.3

21、Place on the hotplate, bring to a slow boil and continue to boil until the volume has reduced to approximately 20 mL. 6.2.1.4 If the digest is a clear solution, transfer it quantitatively, after cooling, to a 100 mL volumetric flask and dilute to the mark with water. 6.2.1.5 If the digest is not a c

22、lear solution, continue as in 6.2.2. 6.2.2 Nitric acid reflux digestion This digestion procedure is suitable for most water and wastewater samples that contain material that is easily oxidized. 6.2.2.1 Quantitatively transfer the digest and anti-bump beads (see 6.2.1) to a 250 mL beaker by rinsing w

23、ith approximately 20 mL of water. 6.2.2.2 Using a safety pipette, slowly add, while stirring, 5,0 mL of the HNO3(see 4.1). 6.2.2.3 Place on the hotplate and slowly evaporate to approximately 20 mL. 6.2.2.4 Cover with a watch glass and heat to obtain a gentle reflux action. 6.2.2.5 Continue refluxing

24、 and adding two further 5,0 mL aliquots of HNO3(see 4.1) if and when necessary. Do not allow to evaporate to dryness. 6.2.2.6 If the digest is a light coloured, clear solution, transfer it quantitatively, after cooling, to a 100 mL volumetric flask and dilute to the mark with water. SANS 6168:2010 E

25、dition 1.2 4 6.2.2.7 If the digestion is incomplete, continue as in 6.2.3. 6.2.3 Nitric acid/hydrochloric acid digestion Use this digestion procedure for samples with visible suspended solids or for digests that have not achieved complete dissolution after the nitric acid digestion (see 6.2.2). 6.2.

26、3.1 Remove the watch glass from the beaker (see 6.2.2), slowly evaporate the digest to less than 5 mL and allow to cool. 6.2.3.2 Using a safety pipette, slowly add, while stirring, 10,0 mL of the dilute hydrochloric acid (see 4.3). 6.2.3.2 Add approximately 15 mL of water and heat for 15 min. (Do no

27、t boil.) 6.2.3.3 Allow to cool and quantitatively transfer the digest to a 100 mL volumetric flask with the washings from the beaker and the watch glass. 6.2.3.4 Dilute to the mark with water. 6.3 Pretreatment for suspended metal 6.3.1 Filter preparation Soak the filter in water for 1 h and then pla

28、ce it on the base unit of the filtration apparatus. Assemble the apparatus, and filter approximately 50 mL of water over a vacuum to wash. Discard the washings and continue suction to remove excess water. 6.3.2 Sample filtration Transfer 100 mL of sample (or a larger aliquot if preconcentration is r

29、equired) to the funnel, and filter over a vacuum. Wash the funnel and filter by using no more than 50 mL of water. NOTE Excessive washing may result in dissolution of retained metals. 6.3.3 Sample dissolution Remove the filter and wash the residue into a 250 mL conical flask using approximately 50 m

30、L of water. Repeat the washing, using 10,0 mL of the dilute nitric acid (see 4.2) and then discard the filter. Add a few anti-bump beads and bring to a slow boil on the hotplate. Continue boiling until the digest volume is approximately 10 mL to 20 mL. If the digest is not a clear solution, continue

31、 digestion as set out in 6.2.2 and 6.2.3, as appropriate. After cooling, transfer the clear digest quantitatively to a 100 mL volumetric flask and dilute to the mark with water. NOTE Some residues may be difficult to remove from the filter, in which case digest the filter and residue together, but a

32、lso carry a blank through the digestion procedure, which includes a washed membrane filter. SANS 6168:2010 Edition 1.2 5 6.4 Pretreatment for dissolved metal 6.4.1 Filter preparation and sample filtration Proceed as set out in 6.3.1 and 6.3.2, using a 100 mL sample aliquot, and collect the filtrate

33、and washings. 6.4.2 Sample acidification Transfer the filtrate and washings to a 250 mL beaker. Add 0,3 mL of the dilute nitric acid (see 4.2) and evaporate down to a volume of between 10 mL and 50 mL. Transfer to a 100 mL volumetric flask (or to a volumetric flask of a smaller capacity if pre-conce

34、ntration is required) and dilute to the mark with water. 7 Expression of results Perform the metal analysis in accordance with the appropriate test method and so express the result as to indicate the form of metal analysed and the concentration units used. If the result is expressed as total or susp

35、ended metal, indicate in the report the method of digestion used. SABS This page has been left blank intentionally SABS Standards Division The objective of the SABS Standards Division is to develop, promote and maintain South African National Standards. This objective is incorporated in the Standard

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