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2、n American National StandardStandard 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 rev
3、ision. 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 alkalinity in brackish water, seawater, and brines.1.2 This standard does not p
4、urport to address all of the safety concerns, if any, associated with its use. It is the responsibility 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 Standar
5、ds:D 1129 Terminology Relating to Water2D 1193 Specification for Reagent Water2D 3370 Practices for Sampling Water from Closed Con- duits2D 5847 Practice for Writing Quality Control Specifications for Standard Test Methods for Water Analysis3E 200 Practice for Preparation, Standardization, and Stor-
6、 age of Standard and Reagent Solutions for Chemical Analysis43. Terminology3.1 DefinitionsFor definitions of terms used in this test method, refer to Terminology D 1129.4. 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
7、.5, respectively. The pH values approximate the points where the hydroxide and bicarbonate ions are neutralized.5. Significance and Use5.1 Alkalinity as carbonate and bicarbonate of saline water is very important in chemical waterflooding or tertiary recov- ery processes for recovering petroleum. Al
8、kaline waters offer better 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 loss of recovery chemical by adsorption. Determination of alkalin- ity in waters used in tertiary
9、 recovery processes is therefore very important.5.2 An alkalinity value is necessary in the calculation of carbonate scaling tendencies of saline waters. It is also neces- sary to determine the alkalinity if the ionic balance of a water analysis is to be used as a check of the reliability of the ana
10、lysis.6. Interferences6.1 Anions other than bicarbonate, carbonate, or hydroxide ions that form weakly dissociated acids that participate in hydrolysis reactions may also contribute to the alkalinity as may some organic materials. The user of this test method on determining the alkalinity is caution
11、ed that all the effects of the anions entering into hydrolysis reactions are combined and reported as an equivalent amount of a single substance or two postulated ions. Included in the reported value is the alkalinity resulting from the presence of borate, silicate, sulfide, and phosphate. The effec
12、t of borate on the alkalinity value is considered negligible for waters with pH values of 7 or less.7. Apparatus7.1 Electrotitrator or Standard pH Meter with suitable electrodes. Maintenance and standardization of electrodes and pH meter should follow manufacturers instructions because performance c
13、an be affected by improper treatment.7.2 Buret, 10-mL micro.8. Reagents8.1 Purity of ReagentsReagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that all reagents shall conform to the specifications of the Commit- tee on Analytical Reagents of the American
14、Chemical Society,5 where such specifications are available. Other grades may be used, provided it is first ascertained that the reagent is of1 This test method is under the jurisdiction of ASTM Committee D19 on Waterand is the direct responsibility of Subcommittee D19.05 on Inorganic Constituents in
15、 Water.Current edition approved Aug. 10, 2003. Published September 2003. Originally approved in 1980. Last previous edition approved in 1997 as D 3875 97.2 Annual Book of ASTM Standards, Vol 11.01.3 Annual Book of ASTM Standards, Vol 11.02.4 Annual Book of ASTM Standards, Vol 15.05.5 Reagent Chemica
16、ls, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents not listed by the American Chemical Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia and Nationa
17、l Formulary, U.S. Pharmaceutical Convention, Inc. (USPC), Rockville, MD.*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.1D 3875 03sufficiently high purity to permit its
18、 use without lessening theaccuracy of the determination.8.2 Purity of WaterUnless otherwise indicated, reference to water shall be understood to mean reagent water conforming to Specification D 1193, Type I. Other reagent water types may be used provided it is first ascertained that the water is of
19、sufficiently high purity to permit its use without adversely affecting the bias and precision of this test method. Type II water was specified at the time of round-robin testing of this test method.8.3 Sulfuric or Hydrochloric Acid, Standard Solution (not exceeding 0.1 N)See Practice E 200 for prepa
20、ration and standardization 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 D 3370.10. Procedure10.1 Standardize the pH meter at a pH close to that of the samples. Normally this wo
21、uld 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 three buffers. Standardize the meter to 7 with pH 7 buffer and check its response at 4 and 10 with pH 4 and pH 10 buffers(within 0.1 pH uni
22、t). 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 the bicarbonate of the sample. Transfer an undiluted sample, usually 50 to 100 mL, into a beaker.10.3 Ti
23、trate with standard acid, while stirring, to pH 8.1 and record this volume as P. If water has a pH below 8.1, record P11.2 Bicarbonate:HCO 2, mg/L 5 A 3 N 3 61 3 1000!/Mwhere:A= millilitres of acid,N= normality of acid, andM= millilitres of sample.11.3 Carbonate:CO3 5 , mg/L 5 A 3 N 3 30 3 1000!/M11
24、.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 Bias 612.1 The precision of this test method within its designated range may be expressed as follow
25、s:S T 5 0.005X 1 2.8SO 5 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 alkalinity determinations, no statement of the accuracy of these measure- ments is practical. In
26、 determining the precision, six operators from five different laboratories analyzed three samples in duplicate on the same day.12.2 The bias of this test method determined from recovery of a known amount of alkalinity in a prepared standard follows:as zero and proceed to 10.4.10.4 Continue the titra
27、tion, with stirring, to pH 4.5 and record the total volume of acid used as T.AmountAdded mg/LAmountFound mg/L6 Bias6 BiasStatistically Signifi-cant (95 % Confi- dence Level)11. Calculation11.1 Results of the titration offer a means for the stoichio- metric classification of the three principal forms
28、 of alkalinity. The presence of the ions may be indicated by the relationships shown in Table 1 (Note). Using Table 1, make the following calculations:NOTE 1The presence of interferences (see 6.1) may produce errors in these relationships.A97597320.2noNOTE 2The above bias estimate is based on an int
29、erlaboratory study on one artificial brine sample. Other samples used in the precision determination 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 the bias determination. The mean responses to the other two solutions
30、were176 mg/L and 537 mg/L.12.3 Precision and bias for this test method conforms to Practice D 2777 77, which was in place at the time of collaborative testing. Under the allowances made in 1.4 of DTABLE 1 Volume Relationships for Alkalinity Calculations 2777 98, these precision and bias data do meet
31、 existing Volume of Standard Acid Corresponding torequirements for interlaboratory studies of Committee D19 testResultsBicarbonate,HCO3Carbonate,CO3 =Hydroxide,OHmethods.P = 0T0013. Quality ControlP 12 T02(T-P)2P-TP = T0 0TA“Standard Methods for the Examination of Water and Wastewater,” 13th edition
32、, American Public Health Association, Washington, DC, 1975, p. 281.T = total titration to pH 4.5, mLP = titration to pH 8.1, mL13.1 In order to be certain that analytical values obtainedusing these test methods are valid and accurate within the6 Supporting data have been filed at ASTM International
33、Headquarters and may be obtained by requesting Research Report RR: D191059.2D 3875 03confidence limits 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 rec
34、ommended by the manufacturer.13.2.2 Verify instrument calibration by analyzing a sample with a known amount of alkalinity. The amount of the sample should fall within 6 15% of the known concentration.13.2.3 If calibration cannot be verified, recalibrate the instrument.13.3 Initial Demonstration of L
35、aboratory Capability13.3.1 If a laboratory has not performed the test before, or if there has been a major change in the measurement system, for example, new analyst, new instrument, and so forth, a precision and bias study must be performed to demonstrate laboratory capability.13.3.2 Analyze seven
36、replicates of a known solution pre- pared from an Independent Reference Material containing a known amount of alkalinity. Each replicate must be taken through the complete analytical test method including any sample preservation and pretreatment steps. The replicates may be interspersed with samples
37、.13.3.3 Calculate the mean and standard deviation of the seven values and compare to the acceptable ranges of bias in12.2. This study should be repeated until the recoveries are within the limits given in 12.2. If an amount other than the recommended amount is used, refer to Practice D 5847 for info
38、rmation on applying the F test and t test in evaluating the acceptability of the mean and standard deviation.13.4 Laboratory Control Sample (LCS)13.4.1 To ensure that the test method is in control, analyzea LCS containing a known amount of alkalinity with each batch or ten samples. If large numbers
39、of samples are analyzed in the batch, analyze the LCS after every ten samples. The LCS must be taken through all of the steps of the analytical method including sample preservation and pretreatment. The result obtained for the LCS shall fall within 6 15 % of the known amount.13.4.2 If the result is
40、not within these limits, analysis ofsamples is halted until the problem is corrected, and either all the samples in the batch must be reanalyzed, or the results must be qualified with an indication that they do not fall within the performance criteria of the test method.13.5 Method Blank13.5.1 Analy
41、ze a reagent water test blank with each batch. The amount of alkalinity found in the blank should be less than the analytical reporting limit. If the amount of alkalinity is found above this level, analysis of samples is halted until the contamination is eliminated, and a blank shows no contamina- t
42、ion at or above this level, or the results must be qualified with an indication that they do not fall within the performance criteria of the test method.13.6 Matrix Spike (MS)13.6.1 Alkalinity is not an analyte that can be feasibly spiked into samples.13.7 Duplicate13.7.1 To check the precision of s
43、ample analyses, analyze a sample in duplicate with each batch. The value obtained must fall within the control limits established by the laboratory.13.7.2 Calculate the standard deviation of the duplicate values and compare to the precision in the collaborative study using an F test. Refer to 6.4.4
44、of Practice D 5847 for information on applying the F test.13.7.3 If the result exceeds the precision limit, the batch must be reanalyzed or the results must be qualified with an indication that they do not fall within the performance criteria of the test method.13.8 Independent Reference Material (I
45、RM)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 in the analytical range for the method chos
46、en. The value obtained must fall within the control limits estab- lished by the laboratory.14. Keywords14.1 alkalinity; brackish; brine; seawaterSUMMARY OF CHANGESCommittee 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 w