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2、n American National StandardStandard Test Method forBarium in Brines, Seawater, and Brackish Water by Direct- Current Argon Plasma Atomic Emission Spectroscopy1This standard is issued under the fixed designation D 3986; the number immediately following the designation indicates the year oforiginal a
3、doption 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 determination of dissolved and total rec
4、overable barium in brines, seawater, and brackish waters by direct-current argon plasma atomic emission spec- troscopy (DCPAES).1.2 This test method has been tested in the range from 10 mg/L to 20 mg/L. Samples shall be diluted to contain concen- trations within the calibration range (see 11.1 and 1
5、2.5). Higher concentrations can also be determined by changing to a less sensitive emission line.1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appro- priate safety and heal
6、th practices and determine the applica- bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:D 1129 Terminology Relating to Water2D 1192 Specification for Equipment for Sampling Water and Steam in Closed Conduits2D 1193 Specification for Reagent Water2D 3352 Test M
7、ethod for Strontium Ion in Brackish Water, Seawater, and Brines3D 3370 Practices for Sampling Water from Closed Con- duits2D 5847 Practice for Writing Quality Control Specifications for Standard Test Methods for Water Analysis 3E 1097 Guide for Direct Current Plasma Emission Spec- trometry Analysis4
8、3. Terminology3.1 DefinitionsFor definitions of terms used in this test method refer to Terminology D 1129.1 This test method is under the jurisdiction of ASTM Committee D19 on Water and is the direct responsibility of Subcommittee D19.05 on Inorganic Constituents in Water.Current edition approved M
9、ay 10, 2002. Published June 2002. Originally published as D 3986 81. Last previous edition D 3986 95.2 Annual Book of ASTM Standards, Vol 11.01.3 Annual Book of ASTM Standards, Vol 11.02.4 Annual Book of ASTM Standards, Vol 03.05.3.2 Definitions of Terms Specific to This Standard:3.2.1 total recover
10、able bariumrecoverable forms of barium that are determinable by the digestion method which is included in the procedure.3.2.2 laboratory control sample, na solution with a cer- tified concentration of barium.4. Summary of Test Method4.1 This test method is dependent upon excitation of the barium ato
11、m by a direct-current plasma source. When the excited barium atom decays to a lower energy state it emits energy of a wavelength characteristic to the barium atom. The intensity of this emitted radiation will increase in direct proportion to the concentration of barium in the sample, when working in
12、 the linear response range.4.2 Since the variable and often high concentration of matrix materials in brines, seawater, and brackish water affect emission differently, it is a difficult task to prepare standards sufficiently similar to the samples. To overcome this problem, the standards are buffere
13、d with lithium ion and the samples are diluted and buffered in the same manner. The standards are used to construct a calibration curve and the concentration of the samples are calculated from this curve. Alternatively, the instrument may be calibrated using a blank and a standard or bracketing stan
14、dards. The sample concentration can then be read out directly from the instrument.4.3 The 455.4-nm line has been found to be the most satisfactory for analysis.NOTE 1The barium lines at 230.4 nm, 233.5 nm, and 553.6 nm have been checked and found to be unsatisfactory for this analysis.4.4 Dissolved
15、barium is determined by filtering the sample through a 0.45-m pore size membrane filter (Note 2) at the time of sampling. This definition of “dissolved” barium is arbitrary since very fine crystals of barium sulfate may pass through the membrane filter.NOTE 2These filters have been found to be conta
16、minated to various degrees with heavy metals depending on the manufacturer. Care should be exercised in selecting a source for these filters. It has been found to be a good practice to wash the filters with nitric acid and then reagent water before filtering a sample.Copyright ASTM International, 10
17、0 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.1D 3986 024.5 If there are no visible suspended solids in the sample,total recoverable barium may be determined on an acidified unfiltered sample in the same manner as dissolved barium.4.6 When the sample contains susp
18、ended solids total recov- erable barium is determined by an acid digestion step to destroy organic and inorganic particulates.5. Significance and Use5.1 All waters containing acid soluble barium compounds are known to be toxic. This test method is useful for the determination of barium in brines, se
19、awater, and brackish waters.5.2 Consumption, inhalation, or absorption of 500 to 600 mg of barium is considered fatal to human beings. Lower levels may result in disorders of the heart, blood vessels, and nerves. The drinking water standards set the maximum con- taminant level for barium as 2 mg/L b
20、arium.6. Interferences6.1 Calcium interferes in concentrations greater than 300 mg/L, however, this can be overcome by dilution of the sample. The method of standard additions as described in Test Method D 3352 will also overcome this interference.6.2 High concentrations of sulfate anion are also kn
21、own to interfere in this test method by causing precipitation of barium in the form of barium sulfate.7. Apparatus7.1 See the manufacturers instruction manual on installa- tion and operation of direct-current argon plasma spectrom- eters. Refer to Guide E 1097 for information on DCP spec- trometers.
22、8. Reagents8.1 Purity of ReagentsReagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that reagents shall conform to the specifications of the committee on analytical reagents of the American Chemical Society5, where such specifications are available. Other
23、grades may be used provided it is first ascertained that the reagent is of sufficiently high purity to permit its use without lessening the accuracy of the determination.8.2 Purity of WaterUnless otherwise indicated, reference to water shall be understood to mean reagent water conforming to Type II
24、of Specification D 1193. Other reagent water types may be used provided it is first ascertained that the water is of sufficiently high purity to permit its use without adversely affecting the precision and bias of the test method. Type II water was specified at the time of round robin testing of thi
25、s test method.5 Reagent Chemicals, American Chemical Society Specifications, American Chemical Society, Washington, DC. For suggestions on the testing of reagents not listed by the American Chemical Society, see Analar Standards for Laboratory8.3 Barium Solution, Stock (1g/L Ba)Dissolve 1.7787 g ofb
26、arium chloride dihydrate (BaCl22H2O) in 100 mLof water, add 2 mL of nitric acid (sp gr 1.42) and dilute to1 L. 8.4 Barium Solution, Standard (50 mg/L)To 5.0 mL of barium stock solution add 5.0 mL of lithium solution (8.8) and dilute to 100 mL with HCl (1 + 499) (8.10). Working standards(11.1) are pr
27、epared from this solution.8.5 Hydrochloric Acid (sp gr 1.19)Concentrated hydro- chloric acid (HCl).NOTE 3If a high reagent blank is obtained for either acid, distill the acid or use spectrograde acid.8.5.1 CautionWhen HCl is distilled, an azeotropic mix- ture is obtained (approximately 6 N HCl).8.6
28、Hydrochloric Acid (1 + 499)Add 1 volume of hydro- chloric acid (sp gr 1.19) to 499 volumes of water.8.7 Lithium CarbonateHigh-purity lithium carbonate(Li2CO3). 68.8 Lithium Solution (40 g/L Li)Dissolve 213.0 g ofLi2CO3 in a minimum amount of hydrochloric acid (sp gr 1.19) and dilute to 1 L with wate
29、r. Approximately 250 mL of HCl (sp gr 1.19) is needed to completely dissolve the lithium carbonate.If distilled HCl is used double the amount (see 8.5, Note 3). Store in a cleaned polyethylene or TFE-fluorocarbon bottle.8.9 Nitric Acid (sp gr 1.42)Concentrated nitric acid(HNO3).8.10 Nitric Acid (1 +
30、 499)Add 1 volume of nitric acid (spgr 1.42) to 499 volumes of water.9. Hazards9.1 As with any method where pumping or aspiration of samples is employed, the viscosity of blank, standards, and samples must be controlled within reasonable limits (that is, do not use reagent water standards to analyze
31、 oil field brines).9.2 To analyze waters containing a high percentage of dissolved solids it is necessary to prepare standards and blanks with matrices similar to the unknown samples. In many cases this is almost impossible and the problem can be solved by high dilution and introduction of lithium i
32、on as an emission enhancement buffer.10. Sampling10.1 Collect the sample in accordance with the applicable method, Specification D 1192, or Practices D 3370.10.2 Preserve the samples with high-purity hydrochloric acid to a pH of two or less immediately at the time of collection(about 2 mL/L). If onl
33、y dissolved barium is to be determined, filter the samples through a 0.45-m membrane (Note 2) filter before acidification.11. Standardization and Calculation11.1 Prepare 100 mL each of a blank and 0.01, 0.02, 0.05, and 0.10 mg/L standards by diluting 5 mL of lithium solution(8.8) and 20, 40, 100, an
34、d 200 L of barium standard solutionChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia and National Formulary, U.S. Pharmaceutical Convention, Inc. (USPC), Rockville,MD.6 A lithium carbonate that has been found satisfactory for preparing this solutionis LI 30 or its equivale
35、nt from Spex Industries, Inc., Box 798, Metuchen, NJ 08840.2D 3986 02TABLE 1 Determination of Precision and Bias for Barium byTABLE 2 Composition of Artificial Brine Samples, g/L Direct-Current Argon Plasma Atomic Emission SpectroscopySample No.123AmountAdded, mg/LAmountFound, mg/LSt,mg/LSO,mg/L% ,
36、BiasStatisticallySignificant95 % LevelChemicalCompound:NaCl A100.050.0150.010.010.881.0760.39+ 8.8yes15.015.500.6640.48+ 3.3yes20.020.320.7560.70+ 1.6yes(8.4) with HCl (1 + 499). Prepare standards and blank each time the test is performed.11.2 Aspiratetheblankandstandards.AspirateHNO3(1 + 499) betwe
37、en each standard and sample.11.3 Using the instrument software, verify that the instru-ment calibration is within user acceptable QC limits and report the barium concentrations accordingly.12. Procedure12.1 When determining dissolved barium the sample should be previously filtered through a 0.45-m m
38、embrane filter and acidified (10.2) then proceed with 12.5.12.2 When determining total recoverable barium and pre- cipitation has occurred or large amounts of suspended solids are present, add 5 mL each of nitric acid (sp gr 1.42) and HCl(sp gr 1.19) to 100 mL of the sample and proceed with 12.3 and
39、12.4.12.3 Heat the samples on a steam bath or hot plate until the volume is reduced to 15 to 20 mL, making certain that the samples do not boil.NOTE 4When analyzing samples of brines or samples containing large amounts (5 %) of dissolved solids. The amount of reduction in volume is left to the discr
40、etion of the analyst.12.4 Cool and filter the samples through fine ashless filter paper into 100-mL volumetric flasks. Wash the filter paper at least three times with water and adjust to 100 mL volume.12.5 Approximate Barium ConcentrationAspirate the sample and compare its emission intensity to that
41、 of the barium solution standard (50 mg/L, 8.4). It should be stressed that this is not an accurate result and is to be used only to calculate thequantity of sample needed for dilution in 12.6.12.6 Transfer an aliquot of the sample containing approxi- mately 0.001 to 0.01 mg of barium to a 100-mL vo
42、lumetric flask. Add 5 mL of lithium solution and dilute to volume with HCl (1 + 499).12.7 Aspirate the sample and record its emission intensity at455.4 nm. Concentrations may be read directly if this capabil- ity is provided. Aspirate HNO3(1 + 499) between samples and standards.13. Precision and Bia
43、s 713.1 PrecisionThe overall and single-operator precision of this method within its designated range for brines, seawater, and brackish water varies with the quantity tested in accor- dance with Table 1. Eight operators from six laboratories7 Supporting data are available from ASTM International He
44、adquarters. RequestRR: D19-1071.KCl A1.002.001.00KBr A1.002.001.00KI A0.5001.000.500CaCl2 A8.0010.008.00MgCl2 A4.505.005.00SrCl2 A1.0000.5001.000Ba + + B10.015.020.0A Concentrations in grams per litre.B Concentrations in milligrams per litre.participated in this study by determining three replicates
45、, on different days, at each concentration level as listed in Table 2.13.2 BiasRecoveries of barium from brines and selected water matrices were as shown in Table 1.13.3 It is the users responsibility to ensure the validity of this test method for waters of untested matrices.13.4 Precision and bias
46、for this test method conforms to Practice D 2777-77, which was in place at the time of collaborative testing. Under the allowances made in 1.4 of D2777-98, these precision and bias data do meet existing requirements for interlaboratory studies of Committee D19 test methods.14. Quality Control (QC)14.1 The following quality control information is recom- mended
