1、Designation: C 1345 96 (Reapproved 2001)Standard Test Method forAnalysis of Total and Isotopic Uranium and Total Thorium inSoils by Inductively Coupled Plasma-Mass Spectrometry1This standard is issued under the fixed designation C 1345; 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 the measurement of totalura
3、nium (U) and thorium (Th) concentrations in soils, as wellas the determination of the isotopic weight percentages of234U,235U,236U, and238U, thereby allowing for the calculationof individual isotopic uranium activity or total uranium activ-ity. This inductively coupled plasma-mass spectroscopy (ICP-
4、MS) method is intended as an alternative analysis to methodssuch as alpha spectroscopy or thermal ionization mass spec-troscopy (TIMS). Also, while this test method covers onlythose isotopes listed above, the instrumental technique may beexpanded to cover other long-lived radioisotopes since theprep
5、aration technique includes the preconcentration of theactinide series of elements. The resultant sample volume can befurther reduced for introduction into the ICP-MS via anelectrothermal vaporization (ETV) unit or other sample intro-duction device, even though the standard peristaltic pumpintroducti
6、on is applied for this test method. The samplepreparation removes organics and silica from the soil by use ofa high temperature furnace and hydrofluoric acid digestion.Thus, this test method can allow for sample variability of bothorganic and silica content. This test method is also described inASTM
7、 STP 1291.1.2 The analysis is performed after an initial drying andgrinding sample preparation process, and the results are re-ported on a dry weight basis. The sample preparation techniqueused incorporates into the sample any rocks and organicmaterial present in the soil. The method of sample prepa
8、rationapplied differs from other techniques, such as those found inPractice C 999, which involve simply tumbling and sieving thesample; however, the user may select whichever technique ismost appropriate to their needs.1.3 A linear calibration is performed for total uranium andthorium over a concent
9、ration range from 5 to 5000 g/L, usingapproximately 6 points. As with the data presented, it issuggested that the increments between points be less than orequal to a factor of ten. With a sample dilution factor of 200resulting from the preparation, this equates to a concentrationrange in the samples
10、 from 1 to 1000 g/g. For those samplesestimated to be above that range by initial activity screening, asmaller aliquot is taken to a dilution of 1000, thereby extendingthe range to 5000 g/g. It is important to note that theconcentration measured directly from this calibration is theconcentration of2
11、38U. The standard values are adjusted forabundance and the abundances in the instrument database aremodified to eliminate any automatic correction, as discussedfurther in the appropriate sections. The calibration range can bechanged based on the needs of the user and the expectedvariation among samp
12、les.1.4 Corrections to the measured isotopic ratios for mass biaseffects are made by determining and applying a mass biasfactor (see 13.3.1). This can be performed for each batchanalyzed. Refer to Appendix X1 for an optional correctionapproach where this factor is determined and applied lessfrequent
13、ly and a calibration correction of measured versuscertified ratios is determined on a batch basis in the range of thesamples analyzed.1.5 The values stated in g/g, g/L or ng/g concentration,and Becquerel per gram (Bq/g) activity are the acceptable SIunits. However, picocurie per gram (pCi/g) is freq
14、uently usedin radiochemistry and established regulatory guidelines andwill, therefore, also be regarded as standard in this test method.1.6 Many of the quality control (QC) practices or checks inthis test method (such as the QC standards used, their fre-quency and general sequence) reflect the guide
15、lines set forth inEPA Method 6020 in SW-846. EPA Method 6020 is not strictlyfollowed, however, because of the fact that it does not coveruranium and thorium analysis, or radioisotopic determinations.The quality control practices and checks used is subject to thediscretion of the laboratory or user,
16、and EPA Method 6020should be referred to as a guideline.1.7 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-bilit
17、y of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:1This test method is under the jurisdiction of ASTM Committee C26 on NuclearFuel Cycle and is the direct responsibility of Subcommittee C26.05 on Methods ofTest.Current edition approved July 10, 1996. Published Octobe
18、r 1996.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.C 859 Terminology Relating to Nuclear Materials2C 998 Practice for Sampling Surface Soil for Radionu-clides2C 999 Practice for Soil Sample Preparation for the Deter-mination of R
19、adionuclides2C 1255 Test Method for Analysis of Uranium and Thoriumin Soils by Energy Dispersive X-Ray Fluorescence Spec-troscopy2D 420 Guide to Site Characterization for Engineering, De-sign, and Construction Purposes3D 1193 Specification for Reagent Water4D 1452 Practice for Soil Investigation and
20、 Sampling byAuger Borings3D 1586 Test Method for Penetration Test and Split-BarrelSampling of Soils3D 1587 Practice for Thin-Walled Tube Geotechnical Sam-pling of Soils3D 2113 Practice for Diamond Core Drilling for Site Inves-tigation3D 2216 Test Method for Laboratory Determination of Water(Moisture
21、) Content of Soil and Rock3D 3550 Practice for Ring-Lined Barrel Sampling of Soils3E 135 Terminology Relating to Analytical Chemistry forMetals, Ores, and Related Materials5E 305 Practice for Establishing and Controlling Spectro-chemical Analytical Curves5E 456 Terminology Relating to Quality and St
22、atistics6E 876 Practice for Use of Statistics in the Evaluation ofSpectrometric Data7E 882 Guide for Accountability and Quality Control in theChemical Analysis Laboratory7STP 1291 “Applications of Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) to Radionuclide Determina-tions”2.2 U.S. EPA Stan
23、dard:Method 6020, SW-846, Inductively Coupled Plasma-MassSpectrometry83. Terminology3.1 Definitions:3.1.1 For definitions of terms relating to analytical atomicspectroscopy, refer to Terminology E 135.3.1.2 For definitions of terms relating to statistics, refer toTerminology E 456.3.1.3 For definiti
24、ons of terms relating to nuclear materials,refer to Terminology C 859.3.1.4 For definitions of terms specifically related to ICP-MSin addition to those found in 3.2, refer to Appendix 3 of Ref(1).93.2 Definitions of Terms Specific to This Standard:3.2.1 mass bias or fractionation, nthe deviation of
25、theobserved or measured isotope ratio from the true ratio as afunction of the difference in mass between the two isotopes.This deviation is the result of several different processes;however, the primary cause is“ Rayleigh fractionation associ-ated with sample evaporation in which lighter isotopes ar
26、ecarried away preferentially” (2). With solution nebulization inICP-MS, source fractionation would be expected to be rela-tively insignificant and independent of time, but with othermethods of introduction, it could be more significant.3.2.2 dead time, nthe interval during which the detectorand its
27、associated counting electronics are unable to recordanother event or resolve successive pulses. The instrumentsignal response becomes non-linear above a certain count ratedue to deadtime effects, typically about 1 3 106counts/s.3.2.3 specific activity, nthe radioactivity of a radioisotopeof an eleme
28、nt per unit weight of the element in a sample, inunits of Bq/g or pCi/g.4. Summary of Test Method4.1 A representative sample of soil is obtained by firsttaking a sizeable amount (150 grams) and drying it, thenrunning it through a crusher, or placing it on a shaker/tumblerto homogenize it, or both. A
29、 portion of the dried and groundsample is weighed out and placed in a high temperature furnaceto remove organics. It is then digested in HNO3/HF, followedby a rapid fuming with H2O2, and209Bi (bismuth) is used as aninternal standard. For an analysis of total and isotopic uranium,the sample can be fi
30、ltered and diluted at this time. A secondarydigestion, using HNO3/HClO4, followed by another H2O2fuming, is performed, if thorium analysis is required. Twoseparate runs of a sample batch are performed on the instru-ment; the first run (at a dilution factor of 200) is to obtain thetotal uranium and t
31、horium results and measure the235U/238Uisotopic ratio, and the second run (after a portion of thedigestate has been concentrated and the actinides separated outby solid phase extraction) is to measure the234U/235U and236U/235U ratios. If the234U and236U information is not needed, thesecond run can b
32、e omitted and the measured238U concentra-tion data (with abundance correction) can be combined withthe235U/238U ratio data to obtain the total uranium concentra-tion (assuming that234U and236U have negligible concentra-tion). A standard peristaltic pump is used as the means ofsample introduction int
33、o the plasma; however, as mentioned inSection 1, an ETV unit, or other method more efficient atsample introduction, may be used to improve sensitivity, whichwould be necessary to look at other actinide series radioiso-topes.5. Significance and Use5.1 This test method measures the presence of uranium
34、 andthorium in soil that occurs naturally and as a result ofcontamination from nuclear operations and uranium ore pro-cessing. The reporting detection levels (RDLs) of total uraniumand thorium are well below the normal background in soil. Thenormal background level for uranium is between 3 and 5 g/g
35、in most geographic areas and slightly higher for thorium. The235U enrichment is also measured from an initial sample passthrough the instrument. The other less abundant uranium2Annual Book of ASTM Standards, Vol 12.01.3Annual Book of ASTM Standards, Vol 04.08.4Annual Book of ASTM Standards, Vol 11.0
36、1.5Annual Book of ASTM Standards, Vol 03.05.6Annual Book of ASTM Standards, Vol 14.02.7Annual Book of ASTM Standards, Vol 03.06.8Available from the U.S. Government Printing Office, Washington, DC 20402.9The boldface numbers in parentheses refer to a list of references at the end ofthis test method.C
37、 13452isotopes (234U and236U) are measured down to a typical soilbackground level after sample concentration and a secondsample analysis. This allows for calculation of individualisotopic uranium and total uranium activity. The majority of theuranium activity results from234U and238U.6. Interference
38、s6.1 Adjacent Isotopic Peak EffectsInterferences can occurfrom adjacent isotopes of high concentration, such as anintense235U peak interfering with the measurement of234Uand236U. This is particularly the case for instruments thatprovide only nominal unit mass resolution at 10 % of the peakheight. Fo
39、r this test method, the ICP-MS peak resolution for209Bi was set to within 0.75 6 0.10 AMU full-width-tenth-maximum (FWTM) peak height to reduce adjacent peakinterference effects. The analysis of spiked and serial dilutionQC standards are used to check for good analyte recovery,which would give indic
40、ation of such matrix interferences.6.2 Isobaric Molecular Ion InterferencesUranium-235could interfere with236U determinations by forming aUH + ion. A laboratory control standard (LCS) is run with eachbatch, which is from a certified soil source of known naturalenrichment (thus containing no236U). Th
41、e measurement ofany236U peak from this standard is used to monitor thismolecular ion interference. At the 300 g/g concentration levelused, there is no236U peak presence above the236U reportingdetection limit (RDL). Another possible molecular ion inter-ference would be the formation of NaBi+, which w
42、ouldinterfere with232Th, since Bi is used as an internal standard.Follow the instrument manufacturers instructions to minimizethese molecular ion formations, for example by optimizing thenebulizer gas flow rate. Correction factors can be established ifthe above interferences are found to be signific
43、ant.6.3 Memory and Sample Matrix Interference EffectsMemory effects or sample carryover can occur from previouslyrun samples. These effects can be detected by looking at thestandard deviation of the repeat trials from a sample analysis.Also, with each batch, a memory check is performed toestablish a
44、n acceptable rinse time. Sample matrix effects canoccur due to the high ion flux through the electrostatic lenses.Biases are possible since pure solution standards are used forcalibration which do not reflect the same high ion flux from thedigested soil sample matrix of unknowns. The soil LCS,mentio
45、ned in 6.2, is used to determine if this error is signifi-cant. Also, this error may be reduced if the lenses are tunedwhile monitoring the Bi in a sample matrix.7. Apparatus7.1 Stirring hotplate,7.2 High temperature furnace,7.3 Balance, with precision of 0.0001 g,7.4 ICP-MS instrument, controlled b
46、y computer and fittedwith the associated software and peripherals,7.5 Peristaltic pump,7.6 Desiccator,7.7 400-mL polytetrafluoroethylene (PTFE) beaker,7.8 10.0 cm PTFE watch glasses,7.9 Magnetic stirring bars,7.10 30-mL quartz crucibles,7.11 Whatman #40 and #542 filter paper,7.12 Funnels, 10 to 7 cm
47、 diameter size,7.13 Funnel rack or stand setup,7.14 100-mL and 250-mL polymethylpentene (PMP) volu-metric flasks,7.15 100- and 250-mL glass quartz beakers,7.16 25-mL glass (or PMP) volumetric flasks, and7.17 25- and 50-mL graduated cylinders, or optional 25-mLacid bottle-top dispensers.8. Reagents a
48、nd Materials8.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents conform to the specifications of the Committee onAnalytical Reagents of the American Chemical Society wheresuch specifications are available.10Other grades
49、 may be usedprovided it is first ascertained that the reagent is of sufficientlyhigh purity to permit its use without lessening the accuracy ofthe determination.8.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean reagent water, as definedby Type I of Specification D 1193.8.3 Nitric Acid (sp gr 1.42)70 % w/w concentrated nitricacid (HNO3).8.4 Hydrofluoric Acid (sp gr 1.18)49 % w/w concentratedhydrofluoric acid (HF).8.5 Hydrogen Peroxide (sp gr 1.41)30 % w/w concen-trated hydrogen peroxide (H2O2).8.6 Perchloric Acid (sp gr 1.67)69
