1、Designation: E 1787 08Standard Test Method forAnions in Caustic Soda and Caustic Potash (SodiumHydroxide and Potassium Hydroxide) by IonChromatography1This standard is issued under the fixed designation E 1787; the number immediately following the designation indicates the year oforiginal adoption o
2、r, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This test method covers the determination of anionicimpurities in 50 % causti
3、c soda (sodium hydroxide) and 50 %caustic potash (potassium hydroxide) solutions using ionchromatography (IC). Anions that can be determined at con-centrations of approximately 0.11000 ug/g (ppm) include:bromide, chlorate, chloride, fluoride, nitrate, phosphate, andsulfate.1.2 By varying the sample
4、size, this test method can be usedfor anhydrous caustic soda and caustic potash products, as wellas other concentrations of liquid products.1.3 This test method is not intended to be used to quantifychloride in caustic soda where the sodium chloride concentra-tion is approximately 1 %. For the most
5、accurate determina-tions, it is recommended that high concentrations of chloridebe analyzed using a potentiometric titration procedure, such asthe one described in Test Methods E 291.1.4 The values stated in SI units are to be regarded asstandard. The values given in parentheses are for informationo
6、nly.1.5 Review the current appropriate Material Safety DataSheets (MSDS) for detailed information concerning toxicity,first aid procedures, and safety precautions.1.6 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the
7、user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. Specific hazardsstatements are given in Section 8.2. Referenced Documents2.1 ASTM Standards:2D 1193 Specification for Reagent WaterE 180 Practice for D
8、etermining the Precision of ASTMMethods for Analysis and Testing of Industrial and Spe-cialty ChemicalsE 291 Test Methods for Chemical Analysis of Caustic Sodaand Caustic Potash (Sodium Hydroxide and PotassiumHydroxide)3. Summary of Test Method3.1 Bromide, chlorate, chloride, fluoride, nitrate, phos
9、phateand sulfate are measured in NaOH or KOH by ion chromatog-raphy. The sample solution is diluted and injected onto asample loop of an automated neutralization module. Thesample in the loop is pumped to a suppression device whichuses electrolysis to neutralize the hydroxide ions. The samplethen is
10、 circulated through this device several times until it iscompletely neutralized. Anionic constituents of the neutralizedsample are concentrated on an anion concentrator column.After the concentration they are separated into individualelution bands in the eluent on a separator column. Theconductivity
11、 of the eluent is reduced with an anion suppressiondevice, and the anions of interest are detected using a conduc-tivity detector. Quantitation of the anions in the samplesolution is achieved by calibrating the IC with a series ofstandards containing known amounts of the anions. Thesestandards are a
12、lso passed through the neutralization device.4. Significance and Use4.1 Anion impurities in caustic soda and caustic potash aremonitored by manufacturers and users for quality control of theproducts.Anions of primary interest are chloride, chlorate, andsulfate. This test method has determined precis
13、ion estimatesonly for these three impurities.5. Interferences5.1 Substances that coelute with the anions of interest willinterfere. A high concentration of one anion can interfere withaccurate quantitation of another anion if their retention timesare close and resolution is affected. For example, ca
14、ustic sodasamples containing large concentrations of chloride can inter-fere with the quantitation of small amounts of fluoride.Selection of a high capacity anion separator column willminimize this problem.1This test method is under the jurisdiction of ASTM Committee E15 onIndustrial and Specialty C
15、hemicals and is the direct responsibility of SubcommitteeE15.01 on General Standards.Current edition approved April 1, 2008. Published May 2008. Originallypublished in 1996. Last previous edition approved in 2002 as E 1787-02.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orco
16、ntact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, We
17、st Conshohocken, PA 19428-2959, United States.5.2 Organic acids, surfactants, dyes, metals, etc., can causefouling of the columns and membranes used in this testmethod, resulting in interferences and decreased sensitivity. Itis very important to follow the manufacturers recommenda-tions for cleaning
18、 and maintaining the various parts of the ICsystem.5.3 The anion concentrator column in the neutralizationmodule has a finite capacity for trapping anions, approximately25 micro-equivalents per column. When the capacity of thecolumn is exceeded, the stripping of anions will not bequantitative.6. App
19、aratus6.1 Ion Chromatograph, equipped with:6.1.1 Conductivity Detector,6.1.2 Anion Separator Column,6.1.3 Guard Column,6.1.4 100-L Sample Loop,6.1.5 Autoneutralization Device, capable of neutralizing thecaustic sample prior to being directed through the separatorcolumn,6.1.6 Post-Column Chemical Sup
20、pression Device, capableof reducing background conductivity due to the eluent, and6.1.7 Data Acquisition System, such as an integrator orcomputer system.6.2 100-mL Volumetric Flasks, for preparing sample solu-tions.6.3 Disposable 10-mL Syringes, for injecting solution intothe IC.6.3.1 IC Autosampler
21、 (optional), can be used as an alterna-tive to manually injecting samples.7. Reagents7.1 Purity of ReagentsReagent grade chemicals should beused in all tests. Unless otherwise indicated, all reagents mustconform to the specifications of the Committee on AnalyticalReagents of the American Chemical So
22、ciety, where suchspecifications are available.3Other grades may be used pro-vided it is first ascertained that the reagent is of sufficientlyhigh purity to permit its use without lessening the accuracy ofthe determination.7.2 Purity of WaterReferences to water means Type 1 (18MV-cm deionized water)
23、conforming to Specification D 1193.7.3 Anion Stock Standards, 1000 ug/g (ppm):7.3.1 Bromide Stock Solution (1.00 mL = 1.00 mgBromide)Dry sodium bromide (NaBr) for 6 h at 150C andcool in a desiccator. Dissolve 1.288 g of the dried NaBr inwater, dilute to 1 L with water, and mix well.7.3.2 Chlorate St
24、ock Solution (1.00 mL = 1.00 mgChlorate)Dissolve 1.275 g of sodium chlorate (NaClO3)inwater, dilute to 1 L with water, and mix well.7.3.3 Chloride Stock Solution (1.00 mL = 1.00 mgChloride)Dry sodium chloride (NaCl) for1hat100C andcool in a desiccator. Dissolve 1.648 g of the dried NaCl inwater, dil
25、ute to 1 L with water, and mix well.7.3.4 Fluoride Stock Solution (1.00 mL = 1.00 mgFluoride)Dry sodium fluoride (NaF) at 105C for at least 8h and cool in a desiccator. Dissolve 2.210 g of the dried NaFin 500 mL of water, dilute to 1 L with water, and mix well.7.3.5 Nitrate Stock Solution (1.00 mL =
26、 1.00 mg Nitrate)Dry sodium nitrate (NaNO3) at 105C for 48 h and cool in adesiccator. Dissolve 1.371 g of the dried NaNO3in water,dilute to 1 L with water, and mix well.7.3.6 Phosphate Stock Solution (1.00 mL = 1.00 mgPhosphate)Dissolve 1.433 g of potassium dihydrogen phos-phate (KH2PO4) in water, d
27、ilute to 1 L with water, and mixwell.7.3.7 Sulfate Stock Solution (1.00 mL = 1.00 mg Sulfate)Dry sodium sulfate (Na2SO4)for1hat105C and cool in adesiccator. Dissolve 1.479 g of the Na2SO4in water, dilute to1 L with water, and mix well.7.4 EluentThe eluent used for the anion analysis willdepend on th
28、e choice of separator column selected. The eluentdescribed below is used with the Dionex AS-12A separatorcolumn.7.4.1 Eluent Concentrate, 0.27 mol/L (M) SodiumCarbonate/0.03 mol/L (M) Sodium Bicarbonate (1003Concentrate)Dissolve 28.6 g of sodium carbonate and 2.52g of sodium bicarbonate in a 1- L vo
29、lumetric flask containing800 mL of water. Dilute to volume with water and mix. Storein a tightly capped polypropylene bottle.7.4.2 Eluent, 2.7 mmol/L (mM) Sodium Carbonate/0.3mmol/L (mM) Sodium Bicarbonate EluentPipet 20.0 mL ofthe eluent concentrate into a 2-L volumetric flask, dilute to themark wi
30、th water, and mix.8. Hazards8.1 Sodium and potassium hydroxides are caustic alkalies,which in their anhydrous or strong solution form, are hazard-ous materials. In contact with the skin they produce burns thatmay be quite serious unless promptly treated. Their action isinsidious since they produce n
31、o immediate stinging or burningsensation, and damage may result before their presence isrealized.8.2 Eyes are particularly vulnerable to severe damage fromthese alkalies.8.3 Use safety goggles or face shields and rubber gloveswhen handling these alkalies, and avoid spillage on clothing.These materia
32、ls rapidly attack wool and leather.8.4 Flush away spilled caustic with water where possible, orcover with absorbent material (such as sawdust, vermiculite, orbaking soda), and sweep up and discard in accordance with allfederal, state, and local health and environmental regulations.Last traces may be
33、 neutralized with dilute acetic acid and thearea washed with water.8.5 Consult Material Safety Data Sheets (MSDS) for chemi-cals listed in this test method for further information.3Reagent Chemicals, American Chemical Society Specifications , AmericanChemical Society, Washington, DC. For suggestions
34、 on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.E17870829. Calibration9.1 The retent
35、ion time for each anion is determined byinjecting a series of standard solutions, each containing onlyone anion of interest, into the IC and recording the timerequired for a peak to appear on the chromatogram. Retentiontimes vary with operating conditions. The standards, therefore,must be chromatogr
36、aphed in the same manner as the samplesolutions, which includes passing them through the autoneu-tralization module. Fig. 1 is a typical chromatogram that showsthe elution order of various anions from the Dionex AS-12Aseparator column using the carbonate/bicarbonate eluent.9.2 Calibrate the ion chro
37、matograph using a series ofcalibration standards. Each standard should contain all theanions of interest. The concentration of anions in this series ofstandards should be prepared so they bracket the expectedconcentration of anions in the diluted sample. After thestandards have been analyzed by IC,
38、the “best-fit” straight lineis determined for each anion using the concentration versus ICarea counts. If the IC is equipped with a computer operatedsoftware or an integrator, calibration should be done accordingto manufacturers instructions for multi-level external standardcalibrations. If an integ
39、rator or computer is not used, calibra-tion curves can be created on graph paper by plotting concen-tration versus peak area for each anion of interest and drawingthe “best-fit” straight line through the points.9.2.1 A typical calibration would include a series of four tofive standards containing th
40、e anions of interest from 0.110g/mL (ppm).10. Procedure10.1 Set up the ion chromatograph and the automatedneutralization device according to the manufacturers instruc-tions. The IC system can be set up to accommodate the use ofan autosampler or manual injection with a syringe. Thedetector ranges are
41、 variable. The range setting required for theanalysis will depend on the concentration of anions in thesample and should be chosen accordingly. Table 1 lists typicalanalytical conditions for the anion analysis by IC.NOTE 1Styrene-based strong acid resin in the H+form and commer-cially available neut
42、ralization cartridges containing this resin have beenused to neutralize caustic samples prior to introduction into an IC. Theiruse can eliminate the need for sophisticated on-line neutralization devices.Even when rinsed thoroughly, however, they introduce contaminants(especially chloride and sulfate
43、) to the sample solution and are notrecommended for determining anions with concentrations less than 50ug/g (ppm) in caustic soda or caustic potash.NOTE 2A chemical suppression device or commercially availableneutralization cartridge installed in the IC system before the separatorcolumn, has been su
44、ccessfully used as a replacement for the automatedneutralization module to neutralize caustic soda and caustic potashsamples. By using this approach, however, the 50 % solutions of causticsoda and caustic potash must be diluted by a ratio of 100:1. Thequantitation limits using this modified techniqu
45、e, therefore, are corre-spondingly higher. Details of the modification are not given in this testmethod.10.2 Equilibrate the system by pumping eluent through thecolumns and the detector until a stable baseline is obtained(approximately 15 to 20 min).10.3 Sample solutions are prepared by transferring
46、 a knownweight of sample (weighed to the nearest 0.01 g) to a 100-mLvolumetric flask and diluting to volume with water. Theamount of dilution is dependent on levels of anions in thesample. In many cases, when both high level and lower levelsof anions are to be quantified in the same sample, two or m
47、oresample solutions of different dilutions may have to be ana-lyzed. The neutralization module is capable of neutralizingsolutions containing 25 % sodium hydroxide when the solutionis cycled through the neutralizer at least twice. Sample solu-tions containing up to 50 g of 50 % product or 25 g ofanh
48、ydrous, therefore, can be neutralized effectively. Table 2can be used as a general guideline of sample dilutions based onexpected concentrations of individual anions.An IC calibrationcovering the range of 0.1 to 10 g/mL has been assumed.10.4 Inject the sample into the ion chromatograph andrecord the
49、 ion chromatogram of anions in caustic. Fig. 2 showsan IC chromatogram of 45 % caustic potash that was diluted 20g/100 mL.Peak # Retention Time (min) Component1 1.90 Fluoride2 2.44 Chlorite3 2.94 Bromate4 3.30 Chloride5 4.15 Nitrite6 6.61 Bromide7 7.08 Chlorate8 7.82 Nitrate9 9.03 Phosphate10 11.02 SulfateFIG. 1 Typical Chromatogram of Anions Eluting from a AS-12ASeparator Column Using Na2CO3/NaHCO3EluentTABLE 1 Ion ChromatographTypical Analytical ConditionsAnion separator column: AS-12AGuard column: AG-12AEluent: 2.7 mmol/L Na2CO3/0.3 mmol/L NaHCO3Eluent fl
