CERTIFICATE OF ANALYSIS

Transcription

1 CERTIFICATE OF ANALYSIS Platinum Group Elements in Unused Automobile Catalyst Constituent Certified value 1,2,4 Uncertainty 3,4 Platinum Palladium The measurand is defined as the mass fraction extracted by microwave digestion and subsequent quantification by MC-ICP-IDMS (Multi-collector Inductively Coupled Plasma Isotope Dilution Mass Spectrometry). 2. The certified values are traceable to the SI through the use of standard solutions (NIST SRM 3140 and SRM 3138) as calibrants and the calibration of all other input quantities to the method specified. 3. The quoted uncertainty is the half-width of the expanded uncertainty interval calculated using a coverage factor (k) of 2, which gives a level of confidence of approximately 95 %. 4. Results are expressed on a dry weight basis. 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 0.2 g. European Reference Material ERM -EB503a was produced and certified under the responsibility of LGC according to the principles laid down in the Technical Guidelines of the European Reference Materials cooperation agreement between BAM-LGC-IRMM. Information on these guidelines is available on the Internet ( Accepted as an ERM, Teddington, August Certificate revised October 2011 Signed: Dr Derek Craston, UK Government Chemist LGC Limited Queens Road Teddington Middlesex TW11 0LY, UK 4005 Page 1 of 5

2 Constituent Indicative Value Concentration Rhodium 220 Additional statistical analysis of data from a number of commercial laboratories suggested that the homogeneity of rhodium in the material was unsatisfactory for sub-samples smaller than 1 g. Due to concerns over this possible heterogeneity at small sample sizes, the rhodium value for this material has been assigned as an indicative value with no associated uncertainty. DESCRIPTION OF THE SAMPLE The material is a mixture of unused automobile catalysts supplied and prepared by a commercial manufacturer. The material was ground to <100 µm and homogenised thoroughly before bottling in 100 g units in screw cap amber glass bottles. INTENDED USE This material is intended for use as a reference material in the development, validation or quality control of analytical methods for the determination of platinum group elements (PGE) in automobile catalysts. The material may also be applicable to other matrices where suitable 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 analysed using Multi-Collector Inductively Coupled Plasma Isotope Dilution Mass Spectrometry (MC-ICP-IDMS) applying a method which had previously been developed under contract with the UK s Department of Trade and Industry as part of the VAM programme 1, 2. Six sub-samples were analysed from a single unit of the material and the mean result was used as the certified value. A full uncertainty budget was calculated for the analysis and this uncertainty was included in the combined uncertainty for the material. The material was first issued for sale in August In 2011, (a) a typographical error was identified and corrected involving the column headings in the table on page 3 summarising the QC data obtained and (b) the wording of the uncertainty statement on page 1 was modified slightly plus minor textual corrections. ANALYTICAL METHOD USED FOR CERTIFICATION Sample Preparation The material was digested using a microwave digestion protocol. Approximately 0.2 g of automobile catalyst was accurately weighed into a Teflon microwave vessel followed by the addition of suitable amounts of 196 Pt and 105 Pd enriched isotopic spike (Oak Ridge Laboratories, Oak Ridge, Tennessee, USA) to give a ratio of 1 for platinum and 0.25 for palladium. Because rhodium is mono-isotopic, ruthenium (Alfa Aesar, Lancashire, United Kingdom) was used as the internal standard for rhodium measurement at a ratio of approximately 7:1. The calibration standards were prepared from serial dilutions of NIST standard solutions SRM 3140 platinum, SRM 3138 palladium and SRM 3144 rhodium, with 5 % HCl diluent. 2 ml HNO 3 was added and the vessels left with lids on for 2 hours for the sample and spike to equilibrate. A further 2 ml HNO 3, 2 ml HCl and 2 ml HF were added to the vessels. Samples were then digested in a Multiwave 3000 microwave using the following programme: Page 2 of 5

3 1) Power W: Ramp for 5 minutes 2) Hold at 1400 W for 50 minutes 3) Then hold at 0 W for 20 minutes with the fan on continuous cooling Once the vessels had cooled, solutions were transferred into pre-weighed plastic tubes and made up to approx. 50 g with 5 % HCl. All samples were then diluted to a concentration of approximately 200 ng/g for analysis. Analysis The analysis was carried out using a Thermo Scientific Neptune MC-ICP-MS. The following instrument parameters were used: Parameters Isotopes monitored for platinum: Isotopes monitored for palladium: Integration times: Idle time: Blocks: Cycles: Cones: RF Power: Values 192 Pt, 193 Ir, 194 Pt, 195 Pt, 196 Pt, 199 Hg, 200 Hg; 105 Pd, 106 Pd, 108 Pd, 110 Pd, 111 Cd, 114 Cd, 117 Sn, 118 Sn s 3 s 10 for Pt and Pd and 5 for Rh 5 for Pd, Pt and Rh Ni 1220 W for all analytes Sample gas flow: ~1.2 L min -1 A USN6000AT ultrasonic nebuliser with membrane desolvator (CETAC, Ohio, USA) was used to reduce interference from metal oxides (particularly ZrO). An automobile catalyst NIST SRM 2556 (certified concentrations: ± 2.3 mg/kg platinum, ± 1.6 mg/kg palladium, and 51.2 ± 0.5 mg/kg rhodium) was used as a quality control sample. Recoveries of greater than 95 % were achieved for all analyses of the SRM. Sample Platinum QC data NIST SRM 2556 Palladium Rhodium (1) (2) (3) (4) Page 3 of 5

4 CONFIRMATORY DATA Confirmation of the platinum level was obtained by analyses carried out at Physikalisch-Technische Bundesanstalt (PTB), Bundesanstalt für Materialforschung und prüfung (BAM) and the Institute for Reference Materials and Measurements (IRMM-SCK). The concentration of platinum in this material determined by PTB was (1890 ± 40) mg/kg. The concentration of platinum in this material determined by BAM was (1907 ± 12) mg/kg. The concentration of platinum in this material determined by IRMM-SCK was (1920 ± 90) mg/kg. Confirmation of the palladium level was obtained by analyses carried out at PTB. The concentration of palladium measured by PTB was (2770 ± 98) mg/kg. Confirmation of the rhodium level was obtained by analyses carried out at PTB. Two independent analyses were undertaken. The first value measured was (239 ± 40) mg/kg and the second value measured was (236 ± 10) mg/kg. All of the confirmatory data agree well with the results obtained by LGC. HOMOGENEITY The homogeneity of the batch was determined by duplicate analysis of 10 units of the material using 0.2 g sub-samples and the same analytical methodology as the characterisation analysis (MC-ICP-IDMS). The data was then analysed by one-way ANOVA. The material was found to be homogeneous for all analytes at the 99 % and 95 % confidence levels. An uncertainty contribution equal to the larger of the between sample standard deviation and the method standard deviation derived by ANOVA was added to the combined uncertainty of the material. SAFETY INFORMATION Refer to material safety data sheet. INSTRUCTIONS FOR USE Prior to use, the material should be thoroughly mixed by several inversions of the bottle. The moisture content of the material must be determined every time aliquots are analysed, as the material will absorb moisture rapidly. A 2 g portion of the material should be accurately weighed and then dried at 110 C for 15 hours. The material should then be left to cool before weighing in a closed vessel. Particular attention should be paid to maintaining a dry environment during cooling and weighing. The minimum sample size which should be used for the analysis of platinum and palladium in this material is 0.2 g. For rhodium analysis the minimum sample size to be used is 1 g. STORAGE The material should be stored at (20 ± 5) C in the original bottle. REFERENCES 1. L. A. Simpson, R. Hearn, T. Catterick, J.Anal.At.Spectrom., 2004, 19, Page 4 of 5

5 Unit Number Date of Shipment 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. Production of this reference material and certificate was supported by the Department for Innovation, Universities & Skills as part of the National Measurement System Chemical & Biological Metrology Knowledge Base Programme. 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