1、Designation: D3875 08D3875 15Standard Test Method forAlkalinity in Brackish Water, Seawater, and Brines1This standard is issued under the fixed designation D3875; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last rev
2、ision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope Scope*1.1 This test method covers the determination of alkalinity in brackish water, seawater, and brines.1.2 The values stated i
3、n SI units are to be regarded as standard. No other units of measurement are included in this standard.1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and h
4、ealth practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:D1129 Terminology Relating to WaterD1193 Specification for Reagent WaterD2777 Practice for Determination of Precision and Bias of Applicable Test Methods of Committee D19 o
5、n WaterD3370 Practices for Sampling Water from Closed ConduitsD5847 Practice for Writing Quality Control Specifications for Standard Test Methods for Water AnalysisE200 Practice for Preparation, Standardization, and Storage of Standard and Reagent Solutions for Chemical Analysis3. Terminology3.1 Def
6、initionsFor definitions of terms used in this test method, refer to Terminology D1129.4. Summary of Test Method4.1 An electrotitrator or pH meter is used to determine the amount of acid necessary to reach pH 8.1 and 4.5, respectively. ThepH values approximate the points where the hydroxide and bicar
7、bonate ions are neutralized.5. Significance and Use5.1 Alkalinity as carbonate and bicarbonate of saline water is very important in chemical waterflooding or tertiary recoveryprocesses for recovering petroleum. Alkaline waters offer better wetting to the formation rock and improve oil release. As an
8、additional benefit, ions that provide alkalinity adsorb on rock surfaces occupying adsorption sites and decrease the loss of recoverychemical by adsorption. Determination of alkalinity in waters used in tertiary recovery processes is therefore very important.5.2 An alkalinity value is necessary in t
9、he calculation of carbonate scaling tendencies of saline waters. It is also necessary todetermine the alkalinity if the ionic balance of a water analysis is to be used as a check of the reliability of the analysis.6. Interferences6.1 Anions other than bicarbonate, carbonate, or hydroxide ions that f
10、orm weakly dissociated acids that participate in hydrolysisreactions may also contribute to the alkalinity as may some organic materials. The user of this test method on determining thealkalinity is cautioned that all the effects of the anions entering into hydrolysis reactions are combined and repo
11、rted as anequivalent amount of a single substance or two postulated ions. Included in the reported value is the alkalinity resulting from thepresence of borate, silicate, sulfide, and phosphate. The effect of borate on the alkalinity value is considered negligible for waterswith pH values of 7 or le
12、ss.1 This test method is under the jurisdiction ofASTM Committee D19 on Water and is the direct responsibility of Subcommittee D19.05 on Inorganic Constituents in Water.Current edition approved Oct. 1, 2008Feb. 1, 2015. Published November 2008April 2015. Originally approved in 1980. Last previous ed
13、ition approved in 20032008 asD3875 03.D3875 08. DOI: 10.1520/D3875-08.10.1520/D3875-15.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to
14、 adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright
15、ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States17. Apparatus7.1 Electrotitrator or Standard pH Meter with suitable electrodes. Maintenance and standardization of electrodes and pH metershould follow manufacturers instructions because performanc
16、e can be affected by improper treatment.NOTE 1Automatic titrators with combined pH electrode are found useful to increase reliability and save time. The use of an automatic titrator isrecommended in the procedure.7.2 Buret, 10-mL micro.8. Reagents8.1 Purity of ReagentsReagent grade chemicals shall b
17、e used in all tests. Unless otherwise indicated, it is intended that allreagents shall conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society,2 wheresuch specifications are available. Other grades may be used, provided it is first ascertained that the
18、reagent is of sufficiently highpurity to permit its use without lessening the accuracy of the determination.8.2 Purity of WaterUnless otherwise indicated, reference to water shall be understood to mean reagent water conforming toSpecification D1193, Type I. Other reagent water types may be used prov
19、ided it is first ascertained that the water is of sufficientlyhigh purity to permit its use without adversely affecting the bias and precision of this test method. Type II water was specified atthe time of round-robin testing of this test method.8.3 Sulfuric or Hydrochloric Acid, Standard Solution (
20、not exceeding 0.1 N)See Practice E200 for preparation andstandardization of acid.8.4 Buffer Solutions (pH 4, 7, and 10)These pH buffers are available from many chemical suppliers.9. Sampling9.1 Collect the sample in accordance with Practices D3370.10. Procedure10.1 Standardize the pH meter at a pH c
21、lose to that of the samples. Normally this would be pH 7 for oilfield waters. However,depending on the source of the sample, it may be as low as pH 4 or as high as pH 10. Check the meter periodically with threebuffers. Standardize the meter to 7 with pH 7 buffer and check its response at 4 and 10 wi
22、th pH 4 and pH 10 buffers (within 0.1pH unit). This is important. Serious errors can result if only one buffer is always used.10.2 Make this analysis immediately after determining the pH in order to minimize errors due to decomposition of thebicarbonate of the sample. Transfer an undiluted sample, u
23、sually 50 to 100 mL, into a beaker.10.3 Titrate with standard acid, while stirring, to pH 8.1 and record this volume as P. If water has a pH below 8.1, record Pas zero and proceed to 10.4. (See Note 1.)NOTE 2Although most alkalinity methods titrate to a pH of 8.3, this method was proved out using a
24、pH of 8.1.10.4 Continue the titration, with stirring, to pH 4.5 and record the total volume of acid used as TT. .11. Calculation11.1 Results of the titration offer a means for the stoichiometric classification of the three principal forms of alkalinity. Thepresence of the ions may be indicated by th
25、e relationships shown in Table 1 (Note).(Note 3). Using Table 1, make the followingcalculations:NOTE 3The presence of interferences (see 6.1) may produce errors in these relationships.11.2 Bicarbonate:HCO32, mg/L 5A 3N 36131000!/Mwhere:A = millilitres of acid,N = normality of acid, andM = millilitre
26、s of sample.11.3 Carbonate:CO35,mg/L 5A 3N 33031000!/M2 Reagent Chemicals, American Chemical Society Specifications, American Chemical Society, Washington, DC. For Suggestions on the testing of reagents not listed bythe American Chemical Society, see Annual Standards for Laboratory Chemicals, BDH Lt
27、d., Poole, Dorset, U.K., and the United States Pharmacopeia and NationalFormulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville, MD.D3875 15211.4 Hydroxyl:OH2,mg/L 5A 3N 31731000!/M11.5 Results of titrations to specific end points may alternatively be reported as follows: The alkalinity to
28、pH _ at_,C = _ meq/L (epm).12. Precision and Bias312.1 The precision of this test method within its designated range may be expressed as follows:S T 50.005X12.8SO 50.0076X10.375where:ST = overall precision,SO = single-operator precision, andX = concentration of alkalinity determined, mg/L.Because of
29、 the instability of solutions prepared for alkalinity determinations, no statement of the accuracy of these measurementsis practical. In determining the precision, six operators from five different laboratories analyzed three samples in duplicate on thesame day.12.2 The bias of this test method dete
30、rmined from recovery of a known amount of alkalinity in a prepared standard follows:colwidth=“28.08*“/COLSPECAmountAddedmg/LAmountFoundmg/LBiasBias BiasBiasStatisticallySignificant(95 %ConfidenceLevel)975 973 2 0.2 noNOTE 4The above bias estimate is based on an interlaboratory study on one artificia
31、l brine sample. Other samples used in the precision determinationhad 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 the bias determination.The mean responses to the other two solutions were 176 mg/L and 537 mg/L.12.3 Preci
32、sion and bias for this test method conforms to Practice D2777 77, which was in place at the time of collaborativetesting. Under the allowances made in 1.4 of D2777 06, 13, these precision and bias data do meet existing requirements forinterlaboratory studies of Committee D19 test methods.13. Quality
33、 Control13.1 In order to be certain that analytical values obtained using these test methods are valid and accurate within the confidencelimits of the test, the following QC procedures must be followed when analyzing alkalinity.13.2 Calibration and Calibration VerificationCalibration and Calibration
34、 Verification:13.2.1 Calibrate the pH meter using pH 4 and pH 7 solutions; or as recommended by the manufacturer.13.2.2 For titration, standardize the titrant as directed above.3 Supporting data have been filed at ASTM International Headquarters and may be obtained by requesting Research Report RR:D
35、19-1059. Contact ASTM CustomerService at serviceastm.org.TABLE 1 Volume Relationships for Alkalinity Calculations Acolwidth=“21.31*“/COLSPECResultsVolume of Standard Acid Corresponding toBicarbonate,HCO3Carbonate,CO3 =Hydroxide,OHP = 0 T 0 0P 12 T 0 2(T-P) 2P-TP = T 0 0 TA “Standard Methods for the
36、Examination of Water and Wastewater,” 13th edition,American Public Health Association, Washington, DC, 1975, p. 281.T = total titration to pH 4.5, mLP = titration to pH 8.1, mLP = titration to pH 8.1, mLD3875 15313.2.3 Verify instrument calibration titrant concentration after standardization by anal
37、yzing a sample with a known amount ofalkalinity. The amount of the sample standard at a mid-range concentration. The measured concentration of a mid-range standardshould fall within 615% 615 % of the known concentration.13.2.4 If calibration cannot be verified, recalibrate the instrument.recalibrate
38、.13.2.5 It is recommended to analyze continuing calibration verification (CCV) at a 10 % frequency. The results should fallwithin the expected precision of the method or 615 % of the known concentration.13.3 Initial Demonstration of Laboratory CapabilityInitial Demonstration of Laboratory Capability
39、:13.3.1 If a laboratory has not performed the test before, or if there has been a major change in the measurement system, forexample, new analyst, new instrument, and so forth, a precision and bias study must be performed to demonstrate laboratorycapability.13.3.2 Analyze seven replicates of a known
40、 solution prepared from an Independent Reference Material containing a knownamount of alkalinity. Each replicate must be taken through the complete analytical test method including any sample preservationand pretreatment steps.13.3.3 Calculate the mean and standard deviation of the seven values and
41、compare to the acceptable ranges of bias in 12.2. Thisstudy should be repeated until the recoveries are within the limits given in 12.2. If an amount other than the recommended amountis used, refer to Practice D5847 for information on applying the F test and t test in evaluating the acceptability of
42、 the mean andstandard deviation.13.4 Laboratory Control Sample (LCS)Laboratory Control Sample (LCS):13.4.1 To ensure that the test method is in control, analyze a LCS containing a known amount of alkalinity with each batch orten samples. If large numbers of samples are analyzed in the batch, analyze
43、 the LCS after every ten samples. (laboratory definedin twenty samples). The laboratory control samples for a large batch should cover the analytical range when possible. The LCSmust be taken through all of the steps of the analytical method including sample preservation and pretreatment. The result
44、 obtainedfor the LCS shall fall within 615 % of the known amount.13.4.2 If the result is not within these limits, analysis of samples is halted until the problem is corrected, and either all thesamples in the batch must be reanalyzed, or the results must be qualified with an indication that they do
45、not fall within theperformance criteria of the test method.13.5 Method BlankMethod Blank:13.5.1 Analyze a reagent water test blank with each laboratory-defined batch. The amount of alkalinity found in the blankshould be less than the analytical reporting limit. If the amount of alkalinity is found a
46、bove this level, analysis of samples is halteduntil the contamination is eliminated, and a blank shows no contamination at or above this level, or the results must be qualifiedwith an indication that they do not fall within the performance criteria of the test method.13.6 Matrix Spike (MS)Matrix Spi
47、ke (MS):13.6.1 Alkalinity is not an analyte that can be feasibly spiked into samples.13.7 DuplicateDuplicate:13.7.1 To check the precision of sample analyses, analyze a sample in duplicate with each laboratory-defined batch. The valueobtained must fall within the control limits established by the la
48、boratory.13.7.2 Calculate the standard deviation of the duplicate values and compare to the precision in the collaborative study using anF test. Refer to 6.4.4 of Practice D5847 for information on applying the F test.13.7.3 If the result exceeds the precision limit, the batch must be reanalyzed or t
49、he results must be qualified with an indicationthat they do not fall within the performance criteria of the test method.13.8 Independent Reference Material (IRM)Independent Reference Material (IRM):13.8.1 In order to verify the quantitative value produced by the test method, analyze an Independent Reference Material (IRM)submitted as a regular sample (if practical) to the laboratory at least once per quarter. The concentration of the IRM should be inthe analytical range for the method chosen. The value obtained must fall within the control li
