1、Designation: E 1787 02Standard 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 (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 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 ppm include: bromide,chlorate, chloride, fluoride, nitrate, phosphate, and sulfate.1.2 By varying the sample size,
4、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 accura
5、te 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 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsi
6、bility of the 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:D 1193 Specification for Reagent Water2E 180
7、Practice for Determining the Precision of ASTMMethods of Analysis and Testing of Industrial Chemicals3E 291 Test Methods for Chemical Analysis of Caustic Sodaand Caustic Potash (Sodium Hydroxide and PotassiumHydroxide)33. Summary of Test Method3.1 Bromide, chlorate, chloride, fluoride, nitrate, phos
8、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
9、 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
10、 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
11、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 preci
12、sion 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, c
13、austic 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.45.2 Organic acids, surfactants, dyes, metals, etc., can causefouling of the columns and memb
14、ranes used in this testmethod, resulting in interferences and decreased sensitivity. Itis very important to follow the manufacturers recommenda-tions for cleaning and maintaining the various parts of the ICsystem.1This test method is under the jurisdiction of ASTM Committee E15 onIndustrial and Spec
15、ialty Chemicals and is the direct responsibility of SubcommitteeE15.01 on General Standards.Current edition approved Oct. 10, 2002. Published December 2002. Originallypublished in 1996. Last previous edition approved in 1996 as E 1787-96.2Annual Book of ASTM Standards, Vol 14.01.3Annual Book of ASTM
16、 Standards, Vol 15.05.4Ion Pac AS9 HC column, Dionex Corp., Sunnyvale, CA, has been foundsuitable.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.3 The anion concentrator column in the neutralizationmodule has a finite capacity for
17、 trapping anions, approximately25 micro-equivalents per column. When the capacity of thecolumn is exceeded, the stripping of anions will not bequantitative.6. Apparatus6.1 Ion Chromatograph, equipped with:6.1.1 Conductivity Detector,6.1.2 Anion Separator Column,56.1.3 Guard Column,66.1.4 100-L Sampl
18、e Loop,6.1.5 Autoneutralization Device, capable of neutralizing thecaustic sample prior to being directed through the separatorcolumn,76.1.6 Post-Column Chemical Suppression Device, capableof reducing background conductivity due to the eluent,8and6.1.7 Data Acquisition System, such as an integrator
19、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. Reagents7.1 Purity of ReagentsReagent grade chemicals shou
20、ld 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.9Other grades may be used pro-vided it is first ascertained that the reagent is of suffic
21、ientlyhigh 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) conforming to Specification D 1193.7.3 Anion Stock Standards, 1000 ppm:7.3.1 Bromide Stock Solution (1.00 mL = 1.00 mgBromide)Dry sodiu
22、m 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, dilute to 1 L with water, and mix well.7.3.3 Chloride
23、 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 mgFluoride)Dry sodium fluoride (NaF) at 105C for at least 8h and
24、 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 = 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 wi
25、th 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 Sulfate)Dry sodium sulfate (Na2SO4)for1hat105C and cool in ad
26、esiccator. 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. The eluentdescribed below is used with the Dionex AS-12A separatorcolumn.7.4.1 Eluent Concentrate, 0.27 M S
27、odium Carbonate/0.03M Sodium Bicarbonate (1003 Concentrate)Dissolve 28.6 gof sodium carbonate and 2.52 g of sodium bicarbonate in a 1-L volumetric flask containing 800 mL of water. Dilute tovolume with water and mix. Store in a tightly capped polypro-pylene bottle.7.4.2 Eluent, 2.7 mM Sodium Carbona
28、te/0.3 mM SodiumBicarbonate EluentPipet 20.0 mL of the eluent concentrateinto a 2-L volumetric flask, dilute to the mark with water, andmix.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 t
29、he skin they produce burns thatmay be quite serious unless promptly treated. Their action isinsidious since they produce no 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
30、safety goggles or face shields and rubber gloveswhen handling these alkalies, and avoid spillage on clothing.These materials 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 sw
31、eep up and discard in accordance with allfederal, state, and local health and environmental regulations.Last traces may be 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 informatio
32、n.9. Calibration9.1 The retention time for each anion is determined byinjecting a series of standard solutions, each containing onlyone anion of interest, into the IC and recording the time5IonPac AS12A column, Dionex Corp., Sunnyvale, CA, has been found to besuitable.6IonPac AG12A column, Dionex Co
33、rp., Sunnyvale, CA, has been found to besuitable.7SP10 AutoNeutralization Module, Dionex Corp., has been found to be suitable.8ASRS-Ultra (4 mm), Dionex Corp., Sunnyvale, CA, has been found to besuitable.9Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washingt
34、on, DC. For suggestions 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.E1787022requi
35、red 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 module. Fig. 1 is a typical chromatogram that showsthe
36、elution order of various anions from the Dionex AS-12Aseparator column using the carbonate/bicarbonate eluent.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 sho
37、uld be prepared so they bracket the expectedconcentration 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
38、integrator, calibration should be done 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 drawingt
39、he “best-fit” straight line through the points.9.2.1 A typical calibration would include a series of four tofive standards containing the anions of interest from 0.110g/mL (ppm).10. Procedure10.1 Set up the ion chromatograph and the automatedneutralization device according to the manufacturers instr
40、uc-tions. The IC system can be set 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 typica
41、lanalytical conditions for the anion analysis by IC.NOTE 1Styrene-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 sophis
42、ticated on-line neutralization devices.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 than 50ppm in caustic soda or caustic potash.NOTE 2An Anion Self-Reg
43、enerating Suppressor,9installed in the ICsystem before the separator column, has been successfully used as areplacement for the automated neutralization module to neutralize causticsoda and caustic potash samples. By using this approach, however, the50 % solutions of caustic soda and caustic potash
44、must be diluted by aratio of 100:1. The quantitation limits using this modified technique,therefore, are correspondingly higher. Details of the modification are notgiven in this test method.10.2 Equilibrate the system by pumping eluent through thecolumns and the detector until a stable baseline is o
45、btained(approximately 15 to 20 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
46、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 the neutralizer
47、 at least twice. Sample solu-tions containing up to 50 g of 50 % product or 25 g ofanhydrous, 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 1
48、0 ppm has been assumed.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/NaH
49、CO3EluentTABLE 1 Ion ChromatographTypical Analytical ConditionsAnion separator column: AS-12AGuard column: AG-12AEluent: 2.7 mM Na2CO3/0.3 mM NaHCO3Eluent flow rate: 1.5 mL/minSample loop: 100 LEluent suppression: ASRS, recycle modeNeutralization cycles: 2E178702310.4 Inject the sample into the ion chromatograph andrecord the ion chromatogram of anions in caustic. Fig. 2 showsan IC chromatogram of 45 % caustic potash that was diluted 20g/100 mL.11. Calculation11.1 Calculate the concentration of each anion of interestusing the peak area of that anion from the s
