1、Designation: E1787 16Standard Test Method forAnions in Caustic Soda and Caustic Potash (SodiumHydroxide and Potassium Hydroxide) by IonChromatography1This standard is issued under the fixed designation E1787; the number immediately following the designation indicates the year oforiginal adoption or,
2、 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 % caustic
3、soda (sodium hydroxide) and 50 %caustic potash (potassium hydroxide) solutions using ionchromatography (IC). Anions that can be determined at con-centrations of approximately 0.1 to 1000 ug/g (ppm) include:bromide, chlorate, chloride, fluoride, nitrate, phosphate, andsulfate.1.2 By varying the sampl
4、e 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 mos
5、t accuratedeterminations, it is recommended that high concentrations ofchloride be analyzed using a potentiometric titration procedure,such as the one described in Test Methods E291.1.4 The values stated in SI units are to be regarded asstandard. The values given in parentheses are for informationon
6、ly.1.5 Review the current appropriate Safety Data Sheets(SDS) for detailed information concerning toxicity, first aidprocedures, 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 user of thi
7、s 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:2D1193 Specification for Reagent WaterE180 Practice for Determining th
8、e Precision of ASTMMethods for Analysis and Testing of Industrial and Spe-cialty Chemicals (Withdrawn 2009)3E291 Test Methods for Chemical Analysis of Caustic Sodaand Caustic Potash (Sodium Hydroxide and PotassiumHydroxide)3.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,
9、phosphateand 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 suppressor device (electro-lytically or chemically regenerated) to neutralize the hydroxi
10、deions. Anionic constituents of the neutralized sample are con-centrated on an anion concentrator column. After the concen-tration they are separated into individual elution bands in theeluent on a separator column. The conductivity of the eluent isreduced with an anion suppression device, and the a
11、nions ofinterest are detected using a conductivity detector. Quantitationof the anions in the sample solution is achieved by calibratingthe IC with a series of standards containing known amounts ofthe anions. These standards are also passed through theneutralization device.4. Significance and Use4.1
12、 Anion impurities in caustic soda and caustic potash aremonitored by manufacturers and users for quality control of the1This test method is under the jurisdiction of ASTM Committee E15 onIndustrial and Specialty Chemicals and is the direct responsibility of SubcommitteeE15.01 on General Standards.Cu
13、rrent edition approved May 15, 2016. Published May 2016. Originallyapproved in 1996. Last previous edition approved in 2008 as E1787-08. DOI:10.1520/E1787-16.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of A
14、STMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, P
15、O Box C700, West Conshohocken, PA 19428-2959. United States1products.Anions of primary interest are chloride, chlorate, andsulfate. This test method has determined precision estimatesonly for these three impurities.5. Interferences5.1 Substances that coelute with the anions of interest willinterfere
16、. A high concentration of one anion can interfere withaccurate quantitation of another anion if their retention timesare close and resolution is affected. For example, caustic sodasamples containing large concentrations of chloride can inter-fere with the quantitation of small amounts of fluoride.Se
17、lection of a high capacity anion separator column willminimize this problem.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
18、 recommenda-tions for cleaning and maintaining the various parts of the ICsystem.5.3 The anion concentrator column in the neutralizationmodule has a finite capacity for trapping anions. Consult withmanufacturer for selection of concentrator column of suitablecapacity. Care should be taken not to exc
19、eed the capacity of thecolumn. When the capacity of the column is exceeded, thestripping of anions will not be quantitative.6. Apparatus6.1 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, other sizes are permitted
20、so longas they do not degrade the precision of the method,6.1.5 Autoneutralization Device, capable of neutralizing thecaustic sample prior to being directed through the separatorcolumn,6.1.6 Post-Column Chemical Suppression Device, capableof reducing background conductivity due to the eluent, and6.1
21、.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 (optional), can be used as an alterna-tive to manually injecting samples.7. Reagents
22、7.1 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 Society, where suchspecifications are available.4Other grades may be used pro-vided it
23、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 (18M-cm deionized water) conforming to Specification D1193.7.3 Anion Stock Standards, 1000 ug/g (ppm):7.3.1 Bro
24、mide Stock Solution (1.00 mL = 1.00 mgBromide)Dry sodium bromide (NaBr) for6hat150C 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 Stock Solution (1.00 mL = 1.00 mgChlorate)Dissolve 1.275 g of sodium chlorate (NaClO3)inwater
25、, 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, dilute to 1 L with water, and mix well.7.3.4 Fluoride Stock Solution (1.00 mL = 1.00 mgFluorid
26、e)Dry sodium fluoride (NaF) at 105C for at least 8 hand cool in a desiccator. Dissolve 2.210 g of the dried NaF in500 mL of water, dilute to 1 L with water, and mix well.7.3.5 Nitrate Stock Solution (1.00 mL = 1.00 mg Nitrate)Dry sodium nitrate (NaNO3) at 105C for 48 h and cool in adesiccator. Disso
27、lve 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, dilute to 1 L with water, and mixwell.7.3.7 Sulfate Stock Solution (1.00 mL = 1.00 mg Sulfat
28、e)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 the choice of separator column selected. Follow themanufacturers instructions for preparation
29、 of the eluent.7.4.1 Eluent Concentrate, 0.27 mol/L (M) SodiumCarbonate/0.03 mol/L (M) Sodium Bicarbonate (100 Concentrate)Dissolve 28.6 g of sodium carbonate and 2.52 gof sodium bicarbonate in a 1-Lvolumetric flask containing 800mL of water. Dilute to volume with water and mix. Store in atightly ca
30、pped 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 with water, and mix.8. Hazards8.1 Sodium and potassium hydroxides are caustic alkalies,which in their
31、 anhydrous or strong solution form, are hazard-ous materials. In contact with the skin they produce burns that4Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society,
32、 see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USP), Rockville,MD.E1787 162may be quite serious unless promptly treated. Their action isinsidious since they produce no immedi
33、ate 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 materials rapid
34、ly 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 neutral
35、ized with dilute acetic acid and thearea washed with water.8.5 Consult Safety Data Sheets (SDS) for chemicals listedin this test method for further information.9. Calibration9.1 The retention time for each anion is determined byinjecting a series of standard solutions, each containing onlyone anion
36、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 chromatographed in the same manner as the samplesolutions, which includes passing them through the autoneu-tralization mod
37、ule. Fig. 1 is a typical chromatogram that showsthe elution order of various anions separator column using thecarbonate/bicarbonate eluent. The elution order may changedepending on the column used. See Note 1.NOTE 1Other anion separation and guard columns, and eluent may beused so long as the ions o
38、f interest are separated and the precision of themethod is not degraded.9.2 Calibrate the ion chromatograph 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 ex
39、pectedconcentration of anions in the diluted sample. After thestandards have been analyzed by IC, 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
40、 accordingto manufacturers instructions for multi-level external standardcalibrations. If an integrator 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 th
41、e points.9.2.1 A typical calibration would include a series of four tofive standards containing the anions of interest from 0.1 to10 gmL (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
42、up to accommodate the use ofan autosampler or manual injection with a syringe. Thedetector ranges are 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 anio
43、n analysis by IC.NOTE 2Styrene-based strong acid resin in the H+form and commer-cially available neutralization 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 devi
44、ces.Even when rinsed thoroughly, however, they introduce contaminants(especially chloride and sulfate) to the sample solution and are notrecommended for determining anions with concentrations less than50 ug g (ppm) in caustic soda or caustic potash.NOTE 3A chemical suppression device or commercially
45、 availableneutralization cartridge installed in the IC system before the separatorcolumn, has been successfully 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 ca
46、ustic potash must be diluted by a ratio of at least 1:10. ThePeak # 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 A
47、S-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 flow rate: 1.5 mL/minSample loop: 100 LEluent suppression: ASRS, recycle modeNeutralization cycles:
48、 2E1787 163quantitation limits using this modified technique, 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
49、 30 min).10.3 Sample solutions are prepared by transferring 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 moresample 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
