1、Designation: D 3875 08Standard Test Method forAlkalinity in Brackish Water, Seawater, and Brines1This standard is issued under the fixed designation D 3875; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision.
2、 A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of alkalinityin brackish water, seawater, and brines.1.2 The values stated in SI units are
3、 to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 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
4、and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:D 1129 Terminology Relating to WaterD 1193 Specification for Reagent WaterD 2777 Practice for Determination of Precision and Bias ofApplicable Test Methods of Committee D19 on WaterD 337
5、0 Practices for Sampling Water from Closed ConduitsD 5847 Practice for Writing Quality Control Specificationsfor Standard Test Methods for Water AnalysisE 200 Practice for Preparation, Standardization, and Stor-age of Standard and Reagent Solutions for ChemicalAnalysis3. Terminology3.1 For definitio
6、ns of terms used in this test method, refer toTerminology D 1129.4. Summary of Test Method4.1 An electrotitrator or pH meter is used to determine theamount of acid necessary to reach pH 8.1 and 4.5, respectively.The pH values approximate the points where the hydroxide andbicarbonate ions are neutral
7、ized.5. Significance and Use5.1 Alkalinity as carbonate and bicarbonate of saline wateris very important in chemical waterflooding or tertiary recov-ery processes for recovering petroleum. Alkaline waters offerbetter wetting to the formation rock and improve oil release.Asan additional benefit, ions
8、 that provide alkalinity adsorb onrock surfaces occupying adsorption sites and decrease the lossof recovery chemical by adsorption. Determination of alkalin-ity in waters used in tertiary recovery processes is thereforevery important.5.2 An alkalinity value is necessary in the calculation ofcarbonat
9、e scaling tendencies of saline waters. It is also neces-sary to determine the alkalinity if the ionic balance of a wateranalysis is to be used as a check of the reliability of theanalysis.6. Interferences6.1 Anions other than bicarbonate, carbonate, or hydroxideions that form weakly dissociated acid
10、s that participate inhydrolysis reactions may also contribute to the alkalinity asmay some organic materials. The user of this test method ondetermining the alkalinity is cautioned that all the effects of theanions entering into hydrolysis reactions are combined andreported as an equivalent amount o
11、f a single substance or twopostulated ions. Included in the reported value is the alkalinityresulting from the presence of borate, silicate, sulfide, andphosphate. The effect of borate on the alkalinity value isconsidered negligible for waters with pH values of 7 or less.7. Apparatus7.1 Electrotitra
12、tor or Standard pH Meter with suitableelectrodes. Maintenance and standardization of electrodes andpH meter should follow manufacturers instructions becauseperformance can be affected by improper treatment.7.2 Buret, 10-mL micro.8. Reagents8.1 Purity of ReagentsReagent grade chemicals shall beused i
13、n all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to the specifications of the Commit-tee onAnalytical Reagents of theAmerican Chemical Society,2where such specifications are available. Other grades may be1This test method is under the jurisdiction of ASTM Commit
14、tee D19 on Waterand is the direct responsibility of Subcommittee D19.05 on Inorganic Constituentsin Water.Current edition approved Oct. 1, 2008. Published November 2008. Originallyapproved in 1980. Last previous edition approved in 2003 as D 3875 03.2Reagent Chemicals, American Chemical Society Spec
15、ifications, AmericanChemical Society, Washington, DC. For Suggestions on the testing of reagents notlisted by the American Chemical Society, see Annual Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Conve
16、ntion, Inc. (USPC), Rockville,MD.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.used, provided it is first ascertained that the reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the determinati
17、on.8.2 Purity of WaterUnless otherwise indicated, referenceto water shall be understood to mean reagent water conformingto Specification D 1193, Type I. Other reagent water types maybe used provided it is first ascertained that the water is ofsufficiently high purity to permit its use without advers
18、elyaffecting the bias and precision of this test method. Type IIwater was specified at the time of round-robin testing of thistest method.8.3 Sulfuric or Hydrochloric Acid, Standard Solution (notexceeding 0.1 N)See Practice E 200 for preparation andstandardization of acid.8.4 Buffer Solutions (pH 4,
19、 7, and 10)These pH buffersare available from many chemical suppliers.9. Sampling9.1 Collect the sample in accordance with Practices D 3370.10. Procedure10.1 Standardize the pH meter at a pH close to that of thesamples. Normally this would be pH 7 for oilfield waters.However, depending on the source
20、 of the sample, it may be aslow as pH 4 or as high as pH 10. Check the meter periodicallywith three buffers. Standardize the meter to 7 with pH 7 bufferand check its response at 4 and 10 with pH 4 and pH 10 buffers(within 0.1 pH unit). This is important. Serious errors can resultif only one buffer i
21、s always used.10.2 Make this analysis immediately after determining thepH in order to minimize errors due to decomposition of thebicarbonate of the sample. Transfer an undiluted sample,usually 50 to 100 mL, into a beaker.10.3 Titrate with standard acid, while stirring, to pH 8.1 andrecord this volum
22、e as P. If water has a pH below 8.1, record Pas zero and proceed to 10.4.10.4 Continue the titration, with stirring, to pH 4.5 andrecord the total volume of acid used as T.11. Calculation11.1 Results of the titration offer a means for the stoichio-metric classification of the three principal forms o
23、f alkalinity.The presence of the ions may be indicated by the relationshipsshown in Table 1 (Note). Using Table 1, make the followingcalculations:NOTE 1The presence of interferences (see 6.1) may produce errors inthese relationships.11.2 Bicarbonate:HCO32, mg/L 5 A 3 N 3 61 3 1000!/Mwhere:A = millil
24、itres of acid,N = normality of acid, andM = millilitres of sample.11.3 Carbonate:CO35, mg/L 5 A 3 N 3 30 3 1000!/M11.4 Hydroxyl:OH2, mg/L 5 A 3 N 3 17 3 1000!/M11.5 Results of titrations to specific end points may alterna-tively be reported as follows: The alkalinity to pH _ at_,C = _ meq/L (epm).12
25、. Precision and Bias312.1 The precision of this test method within its designatedrange may be expressed as follows:ST5 0.005X 1 2.8SO5 0.0076X 1 0.375where:ST= overall precision,SO= single-operator precision, andX = concentration of alkalinity determined, mg/L.Because of the instability of solutions
26、 prepared for alkalinitydeterminations, no statement of the accuracy of these measure-ments is practical. In determining the precision, six operatorsfrom five different laboratories analyzed three samples induplicate on the same day.12.2 The bias of this test method determined from recoveryof a know
27、n amount of alkalinity in a prepared standard follows:AmountAddedmg/LAmountFoundmg/L6 Bias 6 BiasStatistically Signifi-cant (95 % Confi-dence Level)975 973 2 0.2 noNOTE 2The above bias estimate is based on an interlaboratory studyon one artificial brine sample. Other samples used in the precisiondet
28、ermination had been altered with acid after make-up to adjust the pH.Some alkalinity was lost in the process so these could not be used in thebias determination. The mean responses to the other two solutions were176 mg/L and 537 mg/L.12.3 Precision and bias for this test method conforms toPractice D
29、 2777 77, which was in place at the time ofcollaborative testing. Under the allowances made in 1.4 ofD 2777 06, these precision and bias data do meet existingrequirements for interlaboratory studies of Committee D19 testmethods.3Supporting data have been filed at ASTM International Headquarters and
30、maybe obtained by requesting Research Report RR: D19-1059.TABLE 1 Volume Relationships for Alkalinity CalculationsAResultsVolume of Standard Acid Corresponding toBicarbonate,HCO3Carbonate,CO3=Hydroxide,OHP =0 T 00P 12 T (T-P) 2P-TP=T 00TA“Standard Methods for the Examination of Water and Wastewater,
31、” 13thedition, American Public Health Association, Washington, DC, 1975, p. 281.T = total titration to pH 4.5, mLP = titration to pH 8.1,mLD387508213. Quality Control13.1 In order to be certain that analytical values obtainedusing these test methods are valid and accurate within theconfidence limits
32、 of the test, the following QC procedures mustbe followed when analyzing alkalinity.13.2 Calibration and Calibration Verification13.2.1 Calibrate the pH meter using pH 4 and pH 7solutions; or as recommended by the manufacturer.13.2.2 Verify instrument calibration by analyzing a samplewith a known am
33、ount of alkalinity. The amount of the sampleshould fall within 615% of the known concentration.13.2.3 If calibration cannot be verified, recalibrate theinstrument.13.3 Initial Demonstration of Laboratory Capability13.3.1 If a laboratory has not performed the test before, or ifthere has been a major
34、change in the measurement system, forexample, new analyst, new instrument, and so forth, a precisionand bias study must be performed to demonstrate laboratorycapability.13.3.2 Analyze seven replicates of a known solution pre-pared from an Independent Reference Material containing aknown amount of al
35、kalinity. Each replicate must be takenthrough the complete analytical test method including anysample preservation and pretreatment steps.13.3.3 Calculate the mean and standard deviation of theseven values and compare to the acceptable ranges of bias in12.2. This study should be repeated until the r
36、ecoveries arewithin the limits given in 12.2. If an amount other than therecommended amount is used, refer to Practice D 5847 forinformation on applying the F test and t test in evaluating theacceptability of the mean and standard deviation.13.4 Laboratory Control Sample (LCS)13.4.1 To ensure that t
37、he test method is in control, analyzea LCS containing a known amount of alkalinity with eachbatch or ten samples. If large numbers of samples are analyzedin the batch, analyze the LCS after every ten samples. The LCSmust be taken through all of the steps of the analytical methodincluding sample pres
38、ervation and pretreatment. The resultobtained for the LCS shall fall within 615 % of the knownamount.13.4.2 If the result is not within these limits, analysis ofsamples is halted until the problem is corrected, and either allthe samples in the batch must be reanalyzed, or the results mustbe qualifie
39、d with an indication that they do not fall within theperformance criteria of the test method.13.5 Method Blank13.5.1 Analyze a reagent water test blank with each batch.The amount of alkalinity found in the blank should be less thanthe analytical reporting limit. If the amount of alkalinity isfound a
40、bove this level, analysis of samples is halted until thecontamination is eliminated, and a blank shows no contamina-tion at or above this level, or the results must be qualified withan indication that they do not fall within the performancecriteria of the test method.13.6 Matrix Spike (MS)13.6.1 Alk
41、alinity is not an analyte that can be feasiblyspiked into samples.13.7 Duplicate13.7.1 To check the precision of sample analyses, analyze asample in duplicate with each batch. The value obtained mustfall within the control limits established by the laboratory.13.7.2 Calculate the standard deviation
42、of the duplicatevalues and compare to the precision in the collaborative studyusing an F test. Refer to 6.4.4 of Practice D 5847 for informa-tion on applying the F test.13.7.3 If the result exceeds the precision limit, the batchmust be reanalyzed or the results must be qualified with anindication th
43、at they do not fall within the performance criteriaof the test method.13.8 Independent Reference Material (IRM)13.8.1 In order to verify the quantitative value produced bythe test method, analyze an Independent Reference Material(IRM) submitted as a regular sample (if practical) to thelaboratory at
44、least once per quarter. The concentration of theIRM should be in the analytical range for the method chosen.The value obtained must fall within the control limits estab-lished by the laboratory.14. Keywords14.1 alkalinity; brackish; brine; seawaterD3875083ASTM International takes no position respect
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46、dard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM Internatio
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