CERTIFICATE OF ANALYSIS

Transcription

1 Constituent 2 CERTIFICATE OF ANALYSIS Hard Drinking Water Metals Number of laboratories Certified value 3 (µg/l) Uncertainty 4 (µg/l) Coverage factor, k 4 Aluminium Antimony Arsenic Barium Beryllium Boron Cadmium Chromium Cobalt Copper Iron Lead Manganese Molybdenum Nickel Selenium Strontium Vanadium Zinc Number of laboratories Certified value 3 (mg/l) Uncertainty 4 (mg/l) Coverage factor, k 4 Calcium Magnesium Potassium Sodium ) Lead was determined at LGC using Isotope Dilution ICP-MS (IDMS). The unweighted mean of duplicate IDMS measurements was used. These certified values were confirmed by the results of an inter-laboratory comparison using different methods (see Table 1). 2) The remaining constituents were certified using the results of an inter-laboratory comparison using different methods (see Table 1). Robust estimates of dispersion and location were used as the values of the concentration determined by participant laboratories. Each data set was obtained in a different laboratory and/or using a different method of measurement. 3) The results are traceable to the SI through the physical and chemical standards used by LGC and the inter-laboratory study participant laboratories. The certified values are reported to the same number of decimal places as the uncertainties (reported to 2 significant figures). 4) The quoted uncertainty is the half-width of the expanded uncertainty interval calculated using a coverage factor (k), which gives a level of confidence of approximately 95 %. This certificate is valid for 12 months from the date of shipment provided the sample is stored under the recommended conditions. The minimum amount of sample to be used is 1 ml. European Reference Material ERM -CA011c was produced and certified under the responsibility of LGC according to the principles laid down in the Technical Guidelines of the European Reference Materials co-operation agreement between BAM-LGC-IRMM. Information on these guidelines is available on the Internet ( Accepted as an ERM, Teddington, November Signed: 4005 Dr Derek Craston, Government Chemist LGC Limited Queens Road Teddington Middlesex TW11 0LY, Page 1 of 5

2 DESCRIPTION OF THE MATERIAL Hard drinking water was sourced from the Tamworth (Staffordshire, ) potable mains supply. The water was filtered through a 0.2 µm in-line filter and acidified to approximately ph 2 by addition of high purity nitric acid to give a final concentration of approximately 0.1 % nitric acid. The acidified water was analysed by ICP-MS and ICP-OES at LGC to establish the base levels of the elements of interest and then high purity metal standards (Inorganic Ventures, New Jersey, USA) were used to spike the base material to levels as close to the England and Wales drinking water regulation limits as possible (Council Directive 98/83/EC, enacted in Statutory Instruments 2000 No. 3184, and 2010 No. 991). The material was mixed and dispensed into pre-cleaned 250 ml screw cap HDPE bottles. The homogeneity of the material was assessed by analysis of eleven units randomly selected from across the fill run. A contribution to the combined uncertainty was included to allow for possible inhomogeneity. INTENDED USE This material is intended for use in the development, validation or quality control of analytical methods for the determination of elements in hard drinking water. The material may also be applicable to other similar matrices where more clearly matched reference materials are not available. Information on how to compare an analytical result with the certified value can be found in ERM Application Note 1; CHARACTERISATION The material was characterised using a combination of IDMS analysis carried out at LGC and an inter-laboratory study organised by LGC. IDMS characterisation was carried out for lead; the value was confirmed by an inter-laboratory study. The participants of the inter-laboratory study were asked to measure aluminium, antimony, arsenic, barium, beryllium, boron, cadmium, calcium, chromium, cobalt, copper, iron, lead, magnesium, manganese, molybdenum, nickel, potassium, selenium, sodium, strontium, vanadium and zinc. The IDMS value obtained as a mass fraction was converted to mass/volume using a measured density of kg/m 3. ANALYTICAL METHODS USED FOR CERTIFICATION IDMS The sample was spiked with a solution containing enriched 206 Pb (NIST SRM983) to give a predicted 208 Pb: 206 Pb ratio of 1. For the characterisation of the material, duplicate measurements were carried out on ten bottles. For calibration, a solution prepared from the NIST reference material SRM981 (Pb) was diluted to give a similar concentration to that of the sample. This was then spiked with the same enriched 206 Pb solution to match the ratio of the sample blends. The measurements were performed using an Agilent 7500ce collision/reaction cell inductively coupled plasma mass spectrometer operating in standard mode. The certified value was assigned as the mean of the 10 duplicate measurements. Inter-laboratory Study Units of the candidate material were distributed to laboratories that had previously agreed to participate in the inter-laboratory study. Participant laboratories chose suitable methods with which they were familiar which included ICP-MS (inductively coupled plasma mass spectrometry), ICP-OES (inductively coupled plasma optical emission spectrometry), ETAAS (electrothermal atomic absorption spectrometry), FAAS (flame atomic absorption spectrometry), IC (ion chromatography), and colorimetry. The number of laboratories that used a particular method is shown in Table 1, overleaf. Page 2 of 5

3 The data from the inter-laboratory study were processed using a robust statistical approach, after screening laboratories based on their performance in analysing a separate QC sample. The certified value for each constituent was assigned as the robust estimate of location of the accepted laboratory data. Uncertainties were based on the robust estimate of dispersion (taking into account the number of laboratories and corrected for the efficiency of the estimator), and combined with the uncertainties related to homogeneity and stability. Table 1 Constituent ICP-MS ICP-OES IC ETAAS FAAS Colorimetry Total Aluminium Antimony Arsenic Barium Beryllium Boron Cadmium Calcium Chromium Cobalt Copper Iron Lead Magnesium Manganese Molybdenum Nickel Potassium Selenium Sodium Strontium Vanadium Zinc Page 3 of 5

4 PARTICIPANTS The following laboratories participated in the inter-laboratory study for this material. Affinity Water Laboratory ALS Environmental Anglian Water British Geological Survey Centre for Ecology and Hydrology (CEH) Dwr Cymru Welsh Water Glasgow Scientific Services I2 Analytical Ltd Intertek Sunbury Technology Centre LATU Atomic Spectrometry Department Northern Ireland Water Northumbrian Water Ltd Northumbrian Water Scientific Services Scientific Analysis Laboratories Ltd Seibersdorf Labor GmbH, Chemical Analytics Severn Trent Water South East Water Sutton and East Surrey Water Thailand Institute of Scientific and Technological Research Thames Water The James Hutton Institute Wessex Water Uruguay Austria Thailand SAFETY INFORMATION Refer to the material Safety Data Sheet. INSTRUCTIONS FOR USE Before use the material should be thoroughly mixed by inversion, and allowed to equilibrate to room temperature (20 ± 5) C. The minimum amount of sample to be used is 1 ml. STORAGE The material should be stored at (5 ± 4) C in its original packaging. After use the bottle should be securely closed and returned to storage at (5 ± 4) C. Page 4 of 5

5 Unit Number: Shipment Date: LEGAL NOTICE The values quoted in this certificate are the best estimate of the true values within the stated uncertainties and based on the techniques described herein. No warranty or representation, express or implied, is made that the use of the product or any information, material, apparatus, method or process which is the subject of or referred to in this certificate does not infringe any third party rights. Further, save to the extent: (a) prohibited by law; or (b) caused by a party's negligence; no party shall be liable for the use made of the product, any information, material, apparatus, method or process which is the subject of or referred to in this certificate. In no event shall the liability of any party exceed whichever is the lower of: (i) the value of the product; or (ii) 500,000; and any liability for loss of profit, loss of business or revenue, loss of anticipated savings, depletion of goodwill, any thirdparty claims or any indirect or consequential loss or damage in connection herewith is expressly excluded. This material was produced by LGC in its role as the s designated National Measurement Institute (NMI) for chemical and bio-measurement. This certificate may not be published except in full, unless permission for the publication of an approved extract has been obtained in writing from LGC Limited. It does not of itself impute to the subject of measurement any attributes beyond those shown by the data contained herein. Page 5 of 5