1、Designation: D 3875 03Standard 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 (e) indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This test method covers the determination of alkalinityin brackish water, seawater, and brines.1.2 This standard does not purport
3、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 and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:D 1129 T
4、erminology Relating to Water2D 1193 Specification for Reagent Water2D 3370 Practices for Sampling Water from Closed Con-duits2D 5847 Practice for Writing Quality Control Specificationsfor Standard Test Methods for Water Analysis3E 200 Practice for Preparation, Standardization, and Stor-age of Standa
5、rd and Reagent Solutions for ChemicalAnalysis43. Terminology3.1 DefinitionsFor definitions of terms used in this testmethod, refer to Terminology 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.
6、The pH values approximate the points where the hydroxide andbicarbonate ions are neutralized.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 offerbe
7、tter wetting to the formation rock and improve oil release.Asan additional benefit, ions 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 th
8、ereforevery important.5.2 An alkalinity value is necessary in the calculation ofcarbonate 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 Anio
9、ns other than bicarbonate, carbonate, or hydroxideions that form weakly dissociated acids 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 theanio
10、ns entering into hydrolysis reactions are combined andreported as an equivalent amount of 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 isc
11、onsidered negligible for waters with pH values of 7 or less.7. Apparatus7.1 Electrotitrator 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 Bu
12、ret, 10-mL micro.8. Reagents8.1 Purity of ReagentsReagent grade chemicals shall beused in 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,5where such specifications are
13、available. Other grades may beused, provided it is first ascertained that the reagent is of1This test method is under the jurisdiction of ASTM Committee D19 on Waterand is the direct responsibility of Subcommittee D19.05 on Inorganic Constituentsin Water.Current edition approved Aug. 10, 2003. Publi
14、shed September 2003. Originallyapproved in 1980. Last previous edition approved in 1997 as D 3875 97.2Annual Book of ASTM Standards, Vol 11.01.3Annual Book of ASTM Standards, Vol 11.02.4Annual Book of ASTM Standards, Vol 15.05.5Reagent Chemicals, American Chemical Society Specifications, AmericanChe
15、mical Society, Washington, 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. Pharmaceutical Convention, Inc. (USPC), Ro
16、ckville,MD.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.sufficiently high purity to permit its use without lessening theaccuracy of the determination.8.2 Purity of
17、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 adverselyaffecting the
18、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, 7, and 10)These
19、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 of the sample, i
20、t 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 is always used.10.
21、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 volume as P. If water
22、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 of alkalinity.The
23、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 = millilitres of acid,N =
24、 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. Precision and B
25、ias612.1 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 prepared for alk
26、alinitydeterminations, 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 known amount of alkal
27、inity 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 precisiondetermination had be
28、en 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 2777 77, which w
29、as in place at the time ofcollaborative testing. Under the allowances made in 1.4 of D2777 98, these precision and bias data do meet existingrequirements for interlaboratory studies of Committee D19 testmethods.13. Quality Control13.1 In order to be certain that analytical values obtainedusing these
30、 test methods are valid and accurate within the6Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR: D191059.TABLE 1 Volume Relationships for Alkalinity CalculationsAResultsVolume of Standard Acid Corresponding toBicarbonate,HCO3Carb
31、onate,CO3=Hydroxide,OHP =0 T 00P 12 T (T-P) 2P-TP=T 00TA“Standard Methods for the Examination of Water and Wastewater,” 13thedition, American Public Health Association, Washington, DC, 1975, p. 281.T = total titration to pH 4.5, mLP = titration to pH 8.1,mLD 3875 032confidence limits of the test, th
32、e 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 amount of alkalini
33、ty. The amount of the sampleshould fall within 6 15% 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 change in the m
34、easurement 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 alkalinity. Each
35、replicate must be takenthrough the complete analytical test method including anysample preservation and pretreatment steps. The replicates maybe interspersed with samples.13.3.3 Calculate the mean and standard deviation of theseven values and compare to the acceptable ranges of bias in12.2. This stu
36、dy should be repeated until the recoveries 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 Sa
37、mple (LCS)13.4.1 To ensure that the 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 analy
38、tical methodincluding sample preservation and pretreatment. The resultobtained for the LCS shall fall within 6 15 % 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 reanalyz
39、ed, or the results mustbe qualified 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
40、the amount of alkalinity isfound above 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 metho
41、d.13.6 Matrix Spike (MS)13.6.1 Alkalinity 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
42、 Calculate the standard deviation of the duplicatevalues and compare to the precision in the collaborative studyusing an F test. Refer to 6.4.4 of Practice D 5847 forinformation on applying the F test.13.7.3 If the result exceeds the precision limit, the batchmust be reanalyzed or the results must b
43、e qualified with anindication that 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
44、 practical) to thelaboratory at 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; seawaterSUMMARY OF CHANGESCo
45、mmittee D19 has identified the location of selected changes to this standard since the last issue (D 3875 97) that may impact the use of this standard.(1) Section 12.3 was added. (2) The QC Section 13 was added.D 3875 033ASTM International takes no position respecting the validity of any patent righ
46、ts asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any
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48、l receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by AST
49、M International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).D 3875 034
