1、Designation: E 2193 08Standard Test Method forUltraviolet Transmittance of Monoethylene Glycol(Ultraviolet Spectrophotometric Method)1This standard is issued under the fixed designation E 2193; the number immediately following the designation indicates the year oforiginal adoption or, in the case of
2、 revision, the year of last revision. 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 a procedure for the determina-tion of the transmittance of monoethyle
3、ne glycol (1,2-ethanediol; MEG) at wavelengths in the region 220 to 350 nm.The results provide a measure of the purity of the sample withrespect to ultraviolet absorbing compounds.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstand
4、ard.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 and determine the applica-bility of regulatory limitations prior to use.1.4 Review
5、the current Material Safety Data Sheets (MSDS)for detailed information concerning toxicity, first aid proce-dures, and safety precautions.2. Referenced Documents2.1 ASTM Standards:2E 131 Terminology Relating to Molecular SpectroscopyE 169 Practices for General Techniques of Ultraviolet-Visible Quant
6、itative AnalysisE 180 Practice for Determining the Precision of ASTMMethods for Analysis and Testing of Industrial and Spe-cialty ChemicalsE 275 Practice for Describing and Measuring Performanceof Ultraviolet, Visible, and Near-Infrared Spectrophotom-eters2.2 Other Document:Manufacturers Instruction
7、 Manual of Spectrophotometer3. Summary of Test Method3.1 The product is sampled in such a way as to avoidextraneous contamination and air contact. The absorbance ofthe sample contained in a 50-mm or 10-mm cell is measuredagainst water at a series of wavelengths and the transmittanceover a pathlength
8、 of 10 mm is calculated.3.2 This test method can be performed with two options asto sample preparation prior to UV measurement.3.2.1 Option A: Nitrogen sparging of the sample (see 4.2).3.2.2 Option B: No nitrogen sparging.4. Significance and Use4.1 Knowledge of the ultraviolet transmittance of monoe
9、t-hylene glycol is required to establish whether the productmeets the requirements of its quality specifications.4.2 Dissolved oxygen in organic solvents, such as MEG,forms complexes that shift the solvent absorption from thevacuum ultraviolet range into the measurable UV range (near190 to 250 nm).
10、Monoethylene glycol has a UV absorptionpeak at 180 nm. For MEG-oxygen complexes, this peak isshifted to a longer wavelength, thus increasing the absorbabil-ity at 220 nm.4.2.1 However, this effect is not observed in water. There isno significant measurable effect due to dissolved oxygen inwater that
11、 would require nitrogen sparging prior to using forcollection of the reference spectrum.4.2.2 Nitrogen sparging and re-measurement of suspect orborderline glycol samples at 220 nm can be used as a tool torule out or confirm the presence of UV affecting contaminantsother than oxygen.5. Apparatus5.1 U
12、ltraviolet Spectrophotometer, double beam, suitablefor measurement at wavelengths in the region 200 to 400 nm,having a spectral bandwidth of 2.0 nm or less at 220 nm,wavelength accuracy 60.5 nm or less at 220 nm, wavelengthrepeatability 0.3 nm or less at 220 nm and a photometricaccuracy of 60.5 % T
13、or less, in the transmittance regionabove 50 % T. Stray light shall be less than 0.1 % at 220 nm.The instrument shall be provided with matched fused silica1This test method is under the jurisdiction of ASTM Committee E15 onIndustrial and Specialty Chemicals and is the direct responsibility of Subcom
14、mitteeE15.02 on Product Standards.Current edition approved April 1, 2008. Published May 2008. Originallyapproved in 2002. Last previous edition approved in 2004 as E 2193 04.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For
15、Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.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.cells
16、with pathlengths of 50 6 0.1 mm or 10 mm 6 0.01 mm.Use of 50-mm cell should provide better precision.5.1.1 Optional Single Beam SpectrophotomerUse thesame cell for measurement of the blank and the sample.5.2 Nitrogen Stripping Apparatus (Option A, 3.2.1), consist-ing of an oil-free pressure reducing
17、 valve to fit the nitrogencylinder, a control valve, vinyl tubing and a disposable glasspipette to be inserted in a 25-mL volumetric flask. Componentsshould be clean and free of ultraviolet contaminants. Avoidcontacting the sample with any plastic material containingplasticizers. Plasticizers can le
18、ach out of the material and causeerroneous results. Replace the disposable pipette by a clean,new one after each sample handling. (See Section 9.)5.3 Bottles, capacity at least 0.5L, with lined, well-fittingcap. Use a fresh bottle for each determination.5.4 Glassware:5.4.1 Volumetric Flask, 25-mL.6.
19、 Reagents and Materials6.1 Purity of ReagentsUnless otherwise indicated, it isintended that all reagents shall conform to the specifications ofthe Committee onAnalytical Reagents of theAmerican Chemi-cal Society where such specifications are available.3Othergrades may be used, provided it is first a
20、scertained that thereagent is of sufficiently high purity to permit its use withoutlessening the accuracy of the determination.6.2 Holmium Oxide Wavelength Calibration Filter, cali-brated (if required; see 8.1.1).NOTE 1The standard reference material SRM 2034, available fromthe National Institute of
21、 Standards and Technology (NIST),4is suitable.6.3 Standard Absorbance Filter, with certified absorbancevalues (if required; see 8.1.2).NOTE 2The standard reference material SRM 2031, available fromNIST,4is suitable. In addition, SRM 935a may be used (see 6.4).6.4 Stray Light Filter, for measuring st
22、ray light at 220 nm (ifrequired; see 8.1.3).NOTE 3The (potassium iodide) standard reference material SRM2032, available from NIST,4is suitable (see also 6.8).6.5 Naphthalene Solution(1 mg/L isooctane) Dissolve 1mg naphthalene in 1000 mL of spectroscopic grade isooctane.(WarningIsooctane is highly fl
23、ammable and irritating to therespiratory system. Avoid contact with skin. Naphthalene isirritating to the skin, eyes, and respiratory system. It may causesensitization by skin contact. Avoid contact with eyes. Wearsuitable protective clothing.6.6 Nitrogen, minimum purity 99.99 % (V/V), oil-free.6.7
24、Potassium Dichromate or Potassium Chromate, forchecking photometric accuracy (if required; see 8.1.2).NOTE 4The standard reference material, no. SRM 935a, availablefrom NIST,4is suitable.(WarningPotassium dichromate is harmful in contactwith skin, toxic if swallowed, and very toxic by inhalation. It
25、is irritating to the respiratory system and skin. Risk of seriousdamage to eyes. It may cause sensitization by skin contact. Itmay cause heritable genetic damage. It may cause cancer byinhalation. In case of accident or if you feel unwell, seekmedical advice immediately (show the label where possibl
26、e).Avoid exposureobtain special instructions before use. Thismaterial or its container, or both, must be disposed of ashazardous waste. Avoid release to the environment. Refer tospecial instructions/safety data sheets.) (WarningPotassiumchromate is irritating to eyes, respiratory system, and skin. I
27、tmay cause sensitization by skin contact. It may cause heritablegenetic damage. It may cause cancer by inhalation. In case ofaccident or if you feel unwell, seek medical advice immedi-ately (show the label where possible). Avoid exposureobtainspecial instructions before use. This material or its con
28、tainer, orboth, must be disposed of as hazardous waste. Avoid release tothe environment. Refer to special instructions/safety datasheets.)6.8 Potassium or Sodium Iodide Solution, for measuringstray light at 220 nm (if required; see 8.1.3).NOTE 5The “UV-VIS Standard” sodium iodide solution,5is suitab
29、le.Potassium iodide solutions can be prepared from NIST standard referencematerial SRM 2032 (see 6.4 and Note 3).6.9 Water, HPLC grade.6.10 Monoethylene Glycol Quality Control Sample, (onlyrequired if maintaining a control chart, see 10.5). Store at atemperature between 0 and 5C. Warm to ambient tem
30、peraturebefore use.7. Sampling7.1 The following precautions must be observed carefullysince the ultraviolet transmittance is very sensitive to smallamounts of extraneous material contaminating the sample andto oxygen dissolved in the sample through air contact. Thesample connection must be protected
31、 against accidental con-tamination and designed so that it will permit convenientpositioning of the sample bottle to the sample outlet in order tominimize air contact, that is, the descending stream of sampleshould be as short as possible. Purge the sampling linethoroughly with sample. Fill the bott
32、le partly with sample,shake and discard. Repeat the rinsing procedure. Then take thesample in a “gentle stream,” thus filling the bottle to within 10mm of the top. A “gentle stream” is a rate of flow that avoidsspattering, splashing, or other aggressive manifestations on thepart of the sample flow.
33、Cap and avoid excessive shakingduring transport (see also Section 9).8. Preparation of Apparatus8.1 SpectrophotometerCheck the performance of thespectrophotometer as described below. General information on3Reagent Chemicals, American Chemical Society Specifications , AmericanChemical Society, Washin
34、gton, 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. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.4Available
35、from National Institute of Standards and Technology (NIST), 100Bureau Dr., Stop 1070, Gaithersburg, MD 20899-1070, http:/www.nist.gov.5Available from Merck KGaA, Frankfurterstrae 250, D-64293 Darmstadt,Germany.E2193082the measurement of performance of spectrophotometers isgiven in Practice E 275.8.1
36、.1 Wavelength AccuracyCheck the wavelength accu-racy of the spectrophotometer at 220 nm, in accordance withthe manufacturers instructions, for example, by means of anaphthalene solution (Warningsee 6.5) in a 10-mm cell. Ifthe scale reading at the observed band maximum differs bymore than 0.3 nm from
37、 220.6 nm (wavelength of naphthaleneband maximum), measure the absorbance in the actual proce-dure (Section 10) at a wavelength setting of 0.6 nm below thevalue found for the naphthalene band maximum.8.1.1.1 Alternatively, wavelength accuracy may be checkedusing the calibrated holmium oxide filter (
38、6.2). Naphthalene isthe preferred material for this purpose but holmium oxide is asufficient alternative.NOTE 6Since the absorbance of monoethylene glycol rises consider-ably at wavelengths shorter than 220 nm, it is essential that the wavelengthposition in this region is accurately set.8.1.2 Photom
39、etric AccuracyCheck that the photometricaccuracy of the spectrophotometer is in accordance with theinstrumental specification (see 5.1), for example, by means ofstandard absorbance filters or solutions of suitable materials(WarningSee 6.7).8.1.3 Stray LightCheck that any stray light emanatingfrom th
40、e spectrophotometer at 220 nm does not exceed theinstrumental specification (see 5.1), for example, by means ofa stray light filter or a solution of a suitable material (see 6.4and 6.5).8.2 GlasswareThoroughly clean the cells, and otherglassware, using the guidelines described in Practice E 275.8.3
41、Nitrogen Stripping Apparatus (Option A, 3.2.1)Assemble the apparatus and flush thoroughly with nitrogen.Pass nitrogen through 20 mL of monoethylene glycol con-tained in a 25-mL volumetric flask and check the quality of thenitrogen by measuring the absorbance at 220 nm, in order tosee whether it rema
42、ins constant after a possible initial decreasedue to the removal of dissolved oxygen.9. Sample Preparation (Option A only-skip to 10 if usingOption B)9.1 Strip the sample with nitrogen before measurement.Introduce 20 mL of test sample into a 25-mL volumetric flaskand pass a brisk stream of nitrogen
43、(see 5.2, 5.4 and 6.6)through the sample for 15 min, using a clean disposablepipette. Stopper the flask.10. Procedure10.1 Adjust the spectrophotometer to the optimum instru-ment settings, selecting the slit width to give a spectralbandwidth of 2.0 nm or less. Spectral bandwidth of 2.0 nm ispreferred
44、 as lower bandwidths increase the noise level of thespectral data.10.2 Fill two 50-mm or 10-mm matched cells with HPLCgrade (see 6.9) water. Make sure the cell windows are clear andthe water is free of bubbles. Place the cells in the cellcompartment of the spectrophotometer, noting the direction oft
45、he cells inside the cell holder, and measure the absorbances at220, 250, 275, and 350 nm, or any other wavelengths requiredby the relevant product specification. Use the cell with thehigher absorbance as the sample cell, the other as the referencecell, and record the absorbances observed as the cell
46、 correc-tions at the various wavelengths.NOTE 7With properly matched cells, the cell correction is less than0.01 absorbance units.10.3 Empty the sample cell and dry with cell tissue.Carefully fill the sample cell with the test sample. Avoidproducing bubbles in the sample. Without changing the adjust
47、-ments of the spectrophotometer, measure and record theabsorbances at the same set of wavelengths as measured in10.2 against the reference cell filled with water. Ensure that thedirection of the cells in the holder is the same as noted in 10.2.Change the water in the reference cell for each set (10.
48、2 and10.3) of measurements made.10.4 Empty the cells and rinse with water. Clean the cells atregular intervals, according to 8.2, and store filled with water.NOTE 8Although the determination in the procedure is described suchthat only one test result is obtained, it is required to perform a second(d
49、uplicate) determination to enable comparison of the duplicate resultswith the repeatability value given in Section 13.10.5 Qualtiy ControlIt is recommended that a controlchart for the UV transmittance in the Monoethylene glycolquality control sample be established and maintained accordingto generally accepted guidelines.6Measure the control sampleeach time a test sample(s) is tested, using the same calibrationprocedure as applied for the sample. If the measured valueexceeds the action limit of the control chart, take appropriateaction before proceeding w
