SANS 5201-2010 Water - Cadmium content《水 镉含量》.pdf

1、 Collection of SANS standards in electronic format (PDF) 1. Copyright This standard is available to staff members of companies that have subscribed to the complete collection of SANS standards in accordance with a formal copyright agreement. This document may reside on a CENTRAL FILE SERVER or INTRA

2、NET SYSTEM only. Unless specific permission has been granted, this document MAY NOT be sent or given to staff members from other companies or organizations. Doing so would constitute a VIOLATION of SABS copyright rules. 2. Indemnity The South African Bureau of Standards accepts no liability for any

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 978-0-626-23633-5 SANS 5201:2010Edition 3.2SOUTH AFRICAN NATIONAL STANDARD Water Cadmium content Published by SABS Standards Division 1 Dr Lategan R

4、oad Groenkloof Private Bag X191 Pretoria 0001Tel: +27 12 428 7911 Fax: +27 12 344 1568 www.sabs.co.za SABS SANS 5201:2010 Edition 3.2 Table of changes Change No. Date Scope Amdt 1 2005 Amended to change the designation of SABS standards to SANS standards, to update referenced standards, and to delet

5、e reference to specific clauses in SANS 6168. 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

6、annex 3 of the WTO/TBT agreement. This document was published in March 2010. This document supersedes SANS 5201:2005 (edition 3.1). A vertical line in the margin shows where the text has been technically modified by amendment No 2. SANS 5201:2010 Edition 3.2 1 Water Cadmium content 1 Scope and field

7、 of application This standard specifies a method of determining the cadmium content of water and wastewater, using an air-acetylene flame and direct flame atomic absorption. The method is applicable to the determination of cadmium in the concentration range 0,05 mg/L to 2,0 mg/L, but the detection l

8、imit can be reduced to less than 0,01 mg/L by concentration of the sample through evaporation. When the sample has a high dissolved solid content, background correction may be required to eliminate non-specific or continuous absorption. 2 Normative references The following referenced documents are i

9、ndispensable 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 national and international standards can be obtained from

10、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 SANS 128/ISO 1042, Laboratory glassware One-mark volumet

11、ric flasks. Amdt 1 SANS 3696/ISO 3696, Water for analytical laboratory use Specification and test methods. SANS 6168, Water Pretreatment for metal analysis. 3 Principle The pretreated sample is aspirated into an air-acetylene flame under oxidizing conditions and the absorbance measured at 228,8 nm i

12、s compared with the absorbances of cadmium standards measured under the same conditions. 4 Reagents NOTE Unless otherwise specified, only use water that complies with the requirements of SANS 3696 and reagents of analytical reagent grade. SANS 5201:2010 Edition 3.2 2 4.1 Nitric acid (HNO3) Concentra

13、ted (d at 25 /25 C = 1,42). 4.2 Dilute nitric acid 1+1 HNO3. 4.3 Acidified water Containing 1,5 mL of HNO3(see 4.1) per litre. 4.4 Cadmium stock solution (1 000 mg/L) 4.4.1 Obtain a commercially available stock solution of cadmium (1 000 mg/L) of guaranteed quality, or prepare the stock solution as

14、described in 4.4.2. 4.4.2 Dissolve 1 000 g of cadmium metal in a minimum volume of the dilute HNO3(see 4.2) and dilute with water to 1 000 mL in a volumetric flask. 4.5 Cadmium working stock solution (100 mg/L) Pipette 10,0 mL of the stock solution (see 4.4) into a 100 mL volumetric flask and dilute

15、 to the mark with the acidified water (see 4.3). 4.6 Cadmium standard solutions (0,05 mg/L to 2,0 mg/L) Prepare at least three cadmium standard solutions that will bracket the expected concentration of the sample by dilution of the working stock solution (see 4.5), using the acidified water (see 4.3

16、) as the diluent. 5 Apparatus 5.1 Atomic absorption spectrophotometer, for use at 228,8 nm. 5.2 Air-acetylene burner, suitable for attachment to the spectrophotometer (see 5.1). 5.3 Cadmium hollow-cathode lamp. 5.4 Oxidant, air, dried and filtered. 5.5 Fuel, acetylene, standard commercial grade. (Re

17、place the cylinder when the cylinder pressure drops to 700 kPa.) CAUTION: Never allow the operating pressure of acetylene to exceed 105 kPa. 5.6 Pressure-reducing regulators, for the supply of fuel and oxidant to the instrument at the appropriate levels recommended by the manufacturer. 5.7 Glassware

18、. 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, as relevant. Amdt 1; amdt 2 SANS 5201:2010 Edition 3.2 3 6 Sample preparation 6.1 Sample concentration Where it is requ

19、ired to extend the working range below 0,05 mg/L, concentrate the sample, using the appropriate technique for the relevant form of metal required, as follows: a) total metal recovery: evaporate a sample aliquot on a hotplate and reconstitute to a volume that will result in the required degree of con

20、centration; b) suspended metal recovery: so filter a sufficient volume of sample in accordance with SANS 6168 that the required degree of concentration is achieved when the residue is reconstituted to 100 mL; Amdt 1 c) dissolved metal recovery: evaporate the acidified filtrate in accordance with SAN

21、S 6168, and reconstitute the filtrate to a volume that will result in the required degree of concentration. Amdt 1 Determine the concentration factor as follows: 01VVf = where f is the concentration factor; V0is the initial sample aliquot, in millilitres; V1is the concentrate volume, in millilitres.

22、 6.2 Sample pretreatment Pretreat the sample or concentrated sample (see 6.1), a blank (see 4.3) and at least one standard in accordance with SANS 6168 in order to analyse for the appropriate form of metal, i.e. soluble, insoluble or total metal. NOTE For the purposes of legislation or specification

23、s relating to this method, pretreat the sample for recovery of total cadmium, unless specifically indicated otherwise. 7 Procedure 7.1 Instrument operation NOTE The differences between makes and models of atomic absorption spectrophotometers make it impracticable to formulate detailed operating inst

24、ructions. Follow the manufacturers operating instructions for the specific instrument but, in general, proceed in accordance with the instructions given in 7.1.1 to 7.1.11. 7.1.1 Turn on the instrument, install the cadmium hollow-cathode lamp (see 5.3) and apply the current recommended by the manufa

25、cturer. 7.1.2 Set the wavelength at 228,8 nm and set the slit width in accordance with the manufacturers instructions. SANS 5201:2010 Edition 3.2 4 7.1.3 Allow the lamp to stabilize for approximately 10 min and then align it to obtain optimum transmission. 7.1.4 Adjust the fine control of the wavele

26、ngth setting of the monochromator in order to ensure maximum response. 7.1.5 Apply and optimize the background correction facility installed on the instrument, to correct for background absorption. NOTE If the instrument is not fitted with a background correction facility, verify (for each sample) t

27、he presence or absence of continuous absorption by measuring the absorption in the immediate vicinity of the resonance wavelength at which the cadmium absorption is determined. The absorbance of the continuum should then be subtracted from the observed absorbance at the cadmium resonance wavelength

28、in order to determine the true cadmium absorbance. 7.1.6 Install the air-acetylene burner (see 5.2). 7.1.7 Check and, if necessary, adjust the gas flow rates to ensure that they are at the levels specified for the instrument. 7.1.8 Turn on the air supply and then the acetylene flow, and ignite the m

29、ixture. 7.1.9 Ensure that the flame is oxidizing (non-luminous with a hazy blue inner core), and then zero the instrument in the absorbance mode. 7.1.10 Aspirate a standard that will give an absorbance exceeding 0,2, and optimize the burner position until the maximum absorbance value is recorded. Th

30、e instrument is now ready for calibration and analysis. 7.1.11 After analysis, extinguish the flame by turning off the acetylene flow first. When the flame is extinguished, turn off the air supply. 7.2 Instrument calibration 7.2.1 Aspirate the analyte blank (see 4.3) and zero the instrument. 7.2.2 A

31、spirate each of the standard solutions (see 4.6), using the acidified water (see 4.3) to flush the nebulizer between aspirations, and record their respective absorbances. 7.2.3 Construct a calibration curve, using the standard concentrations and their respective absorbances. 7.3 Sample analysis 7.3.

32、1 Aspirate the pretreated blank, standard(s) and sample (see 6.2), using the acidified water (see 4.3) to flush the nebulizer between aspirations. 7.3.2 Record the absorbances and determine the concentrations by referring to the calibration curve as constructed in 7.2.3, or record the concentrations

33、 directly if an instrument with concentration mode is used. 7.3.3 Correct the results for the sample and the control standard(s) by subtracting the result for the pretreated blank, if applicable, and verify the absence of interference due to the pretreatment method by confirmation of the true concen

34、tration(s) of the control standard(s). SANS 5201:2010 Edition 3.2 5 7.3.4 In the case where the sample is preconcentrated, determine the true sample concentration as a product of the concentration factor (see 6.1) and the sample result determined in 7.3.3. 8 Expression of results So express the resu

35、lt as to indicate the form of metal analysed and the concentration units used, e.g. Total cadmium as Cd in mg/L. 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.

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