1、Designation: C 1466 00 (Reapproved 2007)Standard Test Method forGraphite Furnace Atomic Absorption SpectrometricDetermination of Lead and Cadmium Extracted fromCeramic Foodware1This standard is issued under the fixed designation C 1466; the number immediately following the designation indicates the
2、year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers procedures for using graphi
3、tefurnace atomic absorption spectroscopy (GFAAS) to quantita-tively determine lead and cadmium extracted by acetic acid atroom temperature from the food-contact surface of foodware.The method is applicable to food-contact surfaces composed ofsilicate-based materials (earthenware, glazed ceramicware,
4、decorated ceramicware, decorated glass, and lead crystal glass)and is capable of determining lead concentrations greater than0.005 to 0.020 g/mLand cadmium concentrations greater than0.0005 to 0.002 g/mL, depending on instrument design.1.2 This test method also describes quality control proce-dures
5、to check for contamination and matrix interferenceduring GFAAS analyses and a specific sequence of analyticalmeasurements that demonstrates proper instrument operationduring the time period in which sample solutions are analyzed.1.3 Cleaning and other contamination control proceduresare described in
6、 this test method. Users may modify contami-nation control procedures provided that the modificationsproduce acceptable results and are used for both sample andquality control analyses.1.4 The values stated in SI (metric) units are to be regardedas the standard. The values given in parentheses are f
7、orinformation only.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to
8、use.2. Referenced Documents2.1 ASTM Standards:2C 738 Test Method for Lead and Cadmium Extracted fromGlazed Ceramic Surfaces3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 calibration solutions4 % acetic acid solutions con-taining known amounts of lead or cadmium which are used
9、 tocalibrate the instrument.3.1.2 characteristic mass (m0mass (picograms, pg) oflead or cadmium that produces instrument response (peak area)of 0.0044 integrated absorbance (absorbance-seconds, A-s).Characteristic mass is a measure of instrument sensitivity andis a function of instrument design, ope
10、rating conditions, andanalyte-matrix-graphite interactions. Characteristic mass iscalculated from the volume of solution in the furnace and theslope of the calibration curve or the concentration that gives aninstrument response in the middle of the working range (that is,approximately 0.100 or 0.200
11、 A-s). Characteristic mass iscompared to manufacturer specifications to verify that theinstrument is optimized.3.1.3 check solutions4 % acetic acid solutions containingknown amounts of lead or cadmium which are analyzed in thesame time period and subjected to the same analytical condi-tions and cali
12、bration curve as sample solutions. Check solu-tions are analyzed to verify that carry-over did not occur andthe instrument was operating correctly during the time periodin which sample solutions were analyzed. Portions of calibra-tion solutions analyzed as unknown test solutions (as opposedto analys
13、is for calibrating the instrument) are used for thispurpose.3.1.4 dilution factor (DF)factor by which concentrationin test solution is multiplied to obtain concentration in originalleach solution. For test solutions prepared by mixing pipet-measured portions of leach solution and diluent, DF =(V1+V2
14、)/V1where V1and V2are volumes of leach solution anddiluent in test solution, respectively. For test solutions preparedby mixing weighed portions of leach solution (gravimetricdilution). DF = WT/W1where: W1is the weight of leachsolution in test solution and WTis the total weight of leachsolution and
15、diluent in the test solution.1This test method is under the jurisdiction ofASTM Committee C21 on CeramicWhitewares and Related Products and is the direct responsibility of SubcommitteeC21.03 on Methods for Whitewares and Environmental Concerns.Current edition approved May 1, 2007. Published May 2007
16、. Originallyapproved in 2000. Last previous edition approved in 2000 as C146600.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page
17、onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.5 fortified leach solutiona portion of leach solution towhich a known amount of lead or cadmium is added. Afortified leach solution is analyzed to calculate perce
18、nt recov-ery and monitor matrix interference. Stock, intermediate, andcalibration solutions are used to fortify leach solutions.3.1.6 gravimetric dilutionpractice of quantitatively pre-paring dilute solutions from more concentrated ones by com-bining known weights of diluent and solution of knowncon
19、centration. Gravimetric dilution using contamination-free,disposable plasticware is recommended whenever possiblebecause glass volumetric flasks require time-consuming, acid-cleaning procedures to eliminate contamination. Gravimetricdilution may be used when densities and major components ofthe dilu
20、ent and concentrated solution are the same (that is, bothsolutions contain 4 % acetic acid). Volumetric flasks must beused when the densities are different (that is, as when diluentcontains 4 % acetic acid and stock standards contain 2 % nitricacid). Gravimetric dilution is accomplished as follows:
21、weighnecessary amount ($1.0000 g) of solution with known con-centration to nearest 0.0001 g in a tared, plastic container. Add4 % acetic acid so that weight of final solution providesrequired concentration. Calculate concentration in final solu-tion as:C25 C13 W1/W2(1)where:C2= concentration in dilu
22、ted (final) solution, ng/mL;C1= concentration in initial solution, ng/mL;W1= weight of initial solution, g; andW2= weight of final solution, g.3.1.7 independent check solution4 % acetic acid solutioncontaining a known amount of lead or cadmium which is froma starting material that is different from
23、the starting materialused to prepare calibration solutions. Starting materials withdifferent lot numbers are acceptable, but starting materialsfrom different manufacturers are preferable. The independentcheck solution is analyzed to verify that calibration solutionshave been prepared correctly. An i
24、ndependent check solutionmust be used to verify calibration until such time that areference material certified for lead and cadmium leachingbecomes available.3.1.8 leach solutionsolution obtained by leaching a testvessel or method blank with 4 % acetic acid for 24 h.3.1.9 method blanka contamination
25、-free laboratory bea-ker or dish that is analyzed by the entire method includingpreparation, leaching, and solution analysis.3.1.10 samplesix test vessels of identical size, shape,color, and decorative pattern.3.1.11 sample concentration limit (SCL)a low concentra-tion (g/mL) that can be reliably me
26、asured in leach solutions.In this test method, the sample concentration limit is theconcentration of lead or cadmium that produces 0.050A-s. Thevalue 0.050 A-s is chosen to establish the limit of this testmethod for two reasons; 0.050A-s is ten times greater than themaximum response (0.005 A-s) typi
27、cally expected from peri-odic, repeated analysis of a contamination-free, 0 ng/mLsolution and thus guarantees that concentrations in samplesolutions are significantly (ten times) greater than those in atrue blank; and percent relative standard deviation of instru-ment response (relative variability
28、as a result of instrumentprecision) is better for 0.050 A-s than for lower values. Thesample concentration limit depends on the characteristic massof the instrument and volume of solution deposited in thefurnace; the numerical value of the limit increases as charac-teristic mass increases and as the
29、 volume of solution depositedin the furnace decreases.3.1.12 sample mass limit (SML)a low mass (g) ofextractable lead or cadmium that can be reliably measured bythis method. The sample limit is the product of the concentra-tion limit times the volume of leach solutions.3.1.13 subsampleeach of the si
30、x individual vessels whichmake up the sample.3.1.14 test solutionsolution deposited in the graphitefurnace for analysis. Test solutions are prepared by dilutingleach solutions with known amounts of 4 % acetic acid. Testsolutions also include portions of undiluted leach, check, andindependent check s
31、olutions deposited in the furnace.3.1.15 working rangerange of instrument response thatmay be described as a linear function of the mass of analyte.The linear range of graphite furnace peak area measurements isapproximately 0.050 to 0.3500-0.400 A-s. The range of linearresponse depends on the elemen
32、t and operating conditions andmust be verified by analyzing calibration solutions each timethe instrument is used. The linear range of instrument responsewas chosen as the working range of this method becauseresponses in the linear range are well below those at whichroll-over adversely affects lead
33、and cadmium instrument re-sponses obtained using Zeeman background correction.4. Summary of Test Method4.1 Lead and cadmium are extracted from the food-contactsurface of test vessels by filling them with 4 % acetic acid towithin 6 to 7 mm (14 in.) of overflowing and leaching them for24 h at 20 to 24
34、C (68 to 75F). Lead and cadmium aredetermined by GFAAS using a chemical modifier and instru-mental background correction. Concentrations in leach solu-tions are calculated using a calibration curve and linear leastsquares regression.5. Significance and Use5.1 Toxic effects of lead and cadmium are we
35、ll known andrelease of these elements from foodware is regulated by manycountries. Regulatory decisions are based on results of 24-hleaching with acetic acid because results of this test method areprecise and accurate and this test method is easy to use.Concentrations of lead and cadmium extracted b
36、y food may bedifferent from results of this method, however, because acidity,contact time, and temperature typical of consumer use aredifferent from those of this test method.5.2 This test method is intended for application only incontamination-free settings and should be performed by well-qualified
37、 technical personnel. It is recognized that it is not apractical or appropriate method to use in a nonlaboratoryenvironment for quality assurance and control of the ceramicprocess. Users are advised to use Test Method C 738 (flameAAS) for purposes of the latter.C 1466 00 (2007)26. Interferences6.1 N
38、onspecific absorption and scattering of light as a resultof concomitant species in leach solutions may produce errone-ously high results. Instrumental background correction is usedto compensate for this interference.6.2 Concomitant elements in leach solutions alter the atomi-zation process and thus
39、degrade or enhance instrumentalresponse. This problem, generally referred to as matrix inter-ference, is controlled by diluting leach solutions and by usinga chemical modifier and is monitored by calculating percentrecovery from a fortified (spiked) portion of leach solution.6.3 Contamination from l
40、aboratory glassware, supplies, andenvironmental particulate matter (dust) may cause erroneouslyhigh results. Contamination is minimized by keeping workareas and labware scrupulously clean, using plastic labwarewhenever possible, using acid-cleaning procedures when glasslabware is required, and prote
41、cting samples and supplies fromdust.Analysts must establish contamination control proceduresbefore attempting sample analysis because correcting for leadand cadmium contamination that is sporadic (heterogeneous)by the practice of “blank subtraction” is not scientifically valid.6.4 Spectral interfere
42、nces due to direct line overlap areextremely rare when hollow cathode lamps are used and are notexpected from leach solutions.7. Apparatus7.1 Atomic Absorption Spectrometer, capable of displayingand recording fast, transient signals, measuring peak area, andhaving sensitivity (m0based on peak area)
43、less than or equal to30-pg lead and 1.3-pg cadmium when wavelengths 283.3 and228.8 nm are used for lead and cadmium determinations,respectively; equipped with light sources (hollow cathode orelectrodeless discharge lamps) specific for lead and cadmium,instrumental background correction (deuterium ar
44、c, Zeeman,or pulsed techniques such as Smith-Hieftje), autosampler, andelectrothermal atomizer (graphite furnace) with pyrolyticallycoated tubes and platforms. Use wavelengths of 283.3 and228.8 nm for lead and cadmium, respectively. Record instru-ment response as peak area (A-s). Do not use peak hei
45、ght. Peakarea compensates for small differences in peak shape anappearance time that occur in leach and calibration solutions.7.2 Gas Supply for Furnace, high purity (99.99 %) argon.7.3 Cooling Water for FurnaceUse device that controlstemperature and recirculates coolant.7.4 Adjustable Macro- and Mi
46、cropipettesManually oper-ated pipets with disposable, colorless, plastic tips and withcapacity ranging from 10 L to 10 mL are acceptable.Motorized pipets capable of automatic dilution are preferred.7.5 Plastic LabwareUse plastic or Teflon labware (gradu-ated cylinders, beakers, stirrers, containers,
47、 pipet tips, autosam-pler cups) for all procedures except preparation of intermediatelead and cadmium solutions (8.7). Disposable labware thatdoes not need precleaning is preferred.3When precleaning isnecessary to eliminate contamination, rinse plastic labwarewith 10 % (1+9) nitric acid followed by
48、rinsing with copiousquantities of reagent water. Air dry the ware in a dust-freeenvironment.7.6 GlasswareUse new volumetric flasks dedicated foruse with only this method to prepare intermediate calibrationsolutions. Do not use glassware used for other laboratoryoperations because potential for conta
49、mination is too great. Donot use glass pipets. Wash new glassware with warm tap waterand laboratory detergent4followed by soaking over night in10 % (1+9) nitric acid and rinsing with copious quantities ofreagent water. Air dry in dust-free environment. Dedicatedglassware may be reused after rinsing with copious quantitiesof reagent water and repeating the acid-cleaning procedure.7.7 Gloves, Powder-Free VinylWear gloves when han-dling test vessels to prevent contamination.7.8 Polyethylene Bags, Self-SealingCover or wrap lab-ware with new plastic bags of sui
