1、Designation: D7980 15Standard Guide forIon-Chromatographic Analysis of Anions in Grab Samplesof Ultrapure Water (UPW) in the Semiconductor Industry1This standard is issued under the fixed designation D7980; the number immediately following the designation indicates the year oforiginal adoption or, i
2、n the case of revision, the year of last revision. 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 guide applies to ultrapure water that is thought tocontain low ppt (parts-per
3、-trillion, weight/weight) levels ofanionic contaminants (for example, bromide, chloride, fluoride,nitrate, nitrite, phosphate, and sulfate). To minimize carry-overproblems between analyses, it is best to limit the concentrationof any one contaminant to approximately 200 ppt (althoughthis limit is on
4、ly an approximation and may vary, depending onthe users application).1.2 This guide is intended to help analysts avoid contami-nation of ultrapure-water samples, since contamination controlis the primary challenge when quantifying ppt-level anions ingrab samples.1.3 This guide does not include recom
5、mendations for col-lecting samples from the water source.1.4 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 and determine the applica-bili
6、ty of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D1129 Terminology Relating to WaterD5127 Guide for Ultra-Pure Water Used in the Electronicsand Semiconductor Industries3. Terminology3.1 Definitions:3.1.1 For definitions of terms used in this standard, refer toTerm
7、inology D1129.3.2 Acronyms:3.2.1 HDPE, nhigh-density polyethylene3.2.2 IC, nion chromatograph3.2.3 PEEK, npolyether ether ketone3.2.4 ppb, nparts-per-billion (weight/weight)3.2.5 ppt, nparts-per-trillion (weight/weight)3.2.6 UPW, nultrapure water4. Significance and Use4.1 This guide is intended to h
8、elp analysts in the semicon-ductor industry. Examples of the usefulness of anion monitor-ing include: (1) determining when ion-exchange resin beds (inwater-purification systems) need to be regenerated, and (2)ensuring that anion levels are low enough to allow the water tobe used for the manufacture
9、of semiconductor devices.4.2 To ensure that the anions are indeed at low-ppt levels, itis recommended to check the conductivity of a subsamplebefore proceeding with Section 5 of this guide. This check doesnot need to be exact; its purpose is simply to let the analystknow if the conductivity is highe
10、r than that of the highest-levelstandard solution being tested. Any high reading signifies thatthe sample, if analyzed, might contaminate the instrument.5. Guidelines5.1 General Considerations:5.1.1 In working with grab samples of ultrapure water,concentrate on controlling contamination, which is th
11、e over-riding challenge when analyzing for anions in UPW. Precau-tions must be taken, including the following. Wear gloves (forexample, nitrile) that do not shed anions. Do not touchanything that might contact the samples. Minimize anioniccontamination in the laboratory air; for example, do not work
12、in the same lab where concentrated mineral acids are beingused or where acid fumes might be brought in by means of theventilation system.5.1.2 Use only fresh, running-from-the-tap UPW wheneverwater is needed. For guidelines regarding maximum contami-nation levels allowed in this water, consult Guide
13、 D5127;recommendations are based on the type of semiconductordevice that ultimately is involved. To ensure highest purity and1This guide is under the jurisdiction of ASTM Committee D19 on Water and isthe direct responsibility of Subcommittee D19.05 on Inorganic Constituents inWater.Current edition a
14、pproved Feb. 15, 2015. Published March 2015. DOI: 10.1520/D7980-15.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM we
15、bsite.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1minimize the build-up of contamination, keep the water streamflowing at all times (a slow rate is acceptable when the waterstream is not in use).5.2 Ion Chromatograph (IC):5.2.1 Us
16、e caution in selecting the IC that will be used forthese analyses. While an entirely new instrument is notmandatory, a unit that has been used for, for example, parts-per-million-level samples often needs extensive clean-up be-fore the anion levels are acceptably low. When utilizing such“used” chrom
17、atographs, replace all tubing with new lengthsand clean the Load/Inject valve thoroughly with fresh, running-from-the-tap UPW; in some cases, the internal parts of thisvalve will need to be replaced with new ones.5.2.2 Use new PEEK (polyether ether ketone) tubing toplumb the instrument.5.2.3 Use a l
18、ow-back-pressure concentrator column forsample loading; install the device such that the sample will beloaded onto the bottom of the concentrator.5.2.4 Use columns with the smallest internal diameterpossible, thereby lowering the amount of sample that must beloaded to achieve a given level of sensit
19、ivity. Install new (fromthe manufacturer) columns to avoid carryover from previousapplications.5.2.5 Keep tubing lengths at a minimum, to decrease dead-volume.5.2.6 Use columns that will give adequate separation of allions of interest and that will provide adequate sensitivity.5.3 Containers for Sta
20、ndards and Samples:5.3.1 Use new, UPW-soaked plastic for example,polystyrene, high-density polyethylene (HDPE) that willbleed down to acceptably low background levels.5.3.2 Use ONLY fresh, running-from-the-tap UPW for rins-ing and soaking; never use soap or acid to clean containers, asthey will intr
21、oduce high levels of anionic contamination andmake background reduction extremely difficult (if not impos-sible).5.3.3 Analyze the soaking water from UPW-soaked newbottles to determine if the anion levels are acceptably low. (Notall brands and formulations of a given plastic type are equallyclean. F
22、or example, polystyrene tissue-culture flasks are typi-cally clean enough, but the background levels depend on themanufacturer. Other types of polystyrene containers, such ascoffee cups, are not acceptable).5.3.4 Dedicate standards bottles to specific concentrations.Also, dedicate a bottle to UPW, f
23、or use in making dilutions.5.3.5 When not in use, keep bottles filled (completely) withUPW that has been obtained fresh and running from the tap.5.3.6 After each use, immediately rinse bottles with UPWby emptying and then refilling at least 34 times. Once thecycles have been completed, fill the bott
24、le to the brim withUPW and cap for storage. Rinse the cap, too; while rinsing thebottle, leave the cap filled with UPW. Before capping the bottlefor storage, rinse the cap once more with UPW. In all of theserinsing procedures, use only UPW that has been obtained freshand running from the tap.NOTE 1E
25、arly-eluting organic acids (for example, acetate, formate)will be the most difficult species to eliminate from the background.5.4 Preparation of Standards:5.4.1 Follow the guidelines in 5.3 when selecting,preparing, and storing containers for standards.5.4.2 Prepare all standards by weight, not by v
26、olume.5.4.3 Prepare all low-level standards that is, approximately1 ppb (parts-per-billion, weight/weight) and lower by pouring,since transfer pipets will contaminate.5.4.4 Remake low-level standards (that is, approximately 1ppb and lower) daily.5.4.5 Prepare and analyze the following types of blank
27、s: (1)a sample of the UPW that has been obtained fresh and runningfrom the tap (to test the purity of the UPW used for dilutions),and (2) a standard-preparation blank. (The second type ofblank is a water sample that has been through all the prepara-tion steps needed to prepare any given working stan
28、dard; theonly difference is that an aliquot of UPW is added instead ofthe usual stock standard.) When calibrating the IC, use thesecond type of blank to obtain data points for inclusion in thecalibration curve.5.5 Loading the Concentrator Column:5.5.1 Use loading procedures that minimize contact wit
29、hpotential sources of contamination. The best choices involveonly a single piece of tubing that runs from the sample bottleto the Load/Inject valve of the IC.5.5.2 Do not “store” the aliquot (to be loaded) in a portionof tubing or other device at any time during the process.5.5.3 If the back pressur
30、e is low enough, pull the samplethrough the concentrator column; otherwise, push the aliquotthrough by means of a pressurizable container and inert,ultrapure gas.5.5.4 Follow manufacturers instructions for determiningthe concentrator columns break-through volume (that is, thevolume beyond which furt
31、her concentrating will result in theelution of some of the already trapped anions).NOTE 2Sensitivity of the analysis can be increased by concentratinga larger mass of water sample, as long as the break-through volume of theconcentrator column has not been exceeded.NOTE 3Automated liquid-handling dev
32、ices for delivering precisevolume for pre-concentration technique are acceptable, if such deviceshave been proven not to contaminate the sample.6. Keywords6.1 anions; contamination control; high purity; ion chroma-tography; trace analysis; ultrapure waterD7980 152ASTM International takes no position
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