1、Designation: D3156 96 (Reapproved 2011)Standard Practice forRubberChromatographic Analysis of Antidegradants(Antioxidants, Antiozonants and Stabilizers)1This standard is issued under the fixed designation D3156; the number immediately following the designation indicates the year oforiginal adoption
2、or, in 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 practice covers the detection and identification bythin-layer chromatogr
3、aphy of antidegradants (antioxidants,antiozonants, and stabilizers) that may be present in raw rubberor rubber products. Analysis for other types of antidegradantsis possible as long as the requirements of the practice are met.1.2 The values stated in SI units are to be regarded as thestandard.1.3 T
4、his 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.2. Referenced Docume
5、nt2.1 ASTM Standards:2D297 Test Methods for Rubber ProductsChemicalAnaly-sis3. Summary of Practice3.1 A simplified procedure (Method A, Section 13.1) basedon a single-solvent system is presented, which provides for theidentification of known materials. This may be used to checkthe presence or absenc
6、e in a rubber vulcanizate or raw rubber,of an antidegradant which should be present. However, sincethe chromatograms obtained may not be absolutely specific forany given antidegradant, a more detailed scheme is given in13.2.3.2 Method B, Section 13.2, using additional solvents andsprays is included,
7、 which enables a greater degree of separationof the spots to be made and therefore may enable detection andidentification of an unknown antidegradant.3.3 Other techniques, for example: gas chromatographic(with or without treatment to obtain derivatives), spectroscopic(ultraviolet and infrared), more
8、 sophisticated thin-layer varia-tions (two dimensional techniques), may be applied to identi-fication of spots for improved detection and identification of anunknown antidegradant.3.4 It is possible that the chromatographic pattern of oneantidegradant may overlap that of another antidegradant;theref
9、ore each laboratory must prepare its own referencestandards, based on the technique chosen from this practice.4. Significance and Use4.1 This practice is useful for the examination of rubbercompounds or products for the presence of chemicals thatprevent or greatly reduce degradation due to oxygen, o
10、zone, orother agents.4.2 This practice is suitable for quality assurance, factorycontrol, and research and development applications.5. Interferences5.1 In the absence of extender oils, antidegradants areextracted from the rubber by a solvent and the evaporatedextract is applied directly to a thin-la
11、yer chromatographicplate.5.2 In the presence of extender oils, the oils are removed byeither a pre-treatment of the plate, with light petroleum ether orby a column chromatographic technique.5.3 Identification of the antidegradant is made by thestandard technique of thin-layer chromatography, herein
12、de-scribed.6. Apparatus6.1 Spreading Device, for making thin layer chromato-graphic plates with a coating 250 to 300 m thick.6.2 Glass Plates, 200 by 200-mm, or suitable for theselected tank. As an alternative to preparing plates, the use ofprecoated plates with a coating of 250 to 300 m is permitte
13、d.Precoated film-backed plates are not recommended.1This practice is under the jurisdiction of ASTM Committee D11 on Rubber andis the direct responsibility of Subcommittee D11.11 on Chemical Analysis.Current edition approved Nov. 1, 2011. Published January 2012. Originallyapproved in 1973. Last prev
14、ious edition approved in 2005 as D3156 96 (2005).DOI: 10.1520/D3156-96R11.2For 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
15、ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.6.3 Drying Oven, 105C minimum.6.4 Desiccator, or drying box for storing plates at fixedhumidity.6.5 Micro-pipets, 5 and 10-mm3(L).6.6 Chromatographic Developing Tank, of a
16、size suitable tohold plates, approximately 250 by 250 by 70 mm to 330 by 240by 110 mm. Small “sandwich-type” tanks are not recom-mended. Add about 200 cm3of developing solvent (7.4)tothetank, swirl, cover, and allow to stand 15 min before using. Tankmay be reused by repeating the swirling and standi
17、ng step, aslong as the solvent ratio remains constant.6.7 Extraction Apparatus, in accordance with Section 18 or25 of Test Methods D297.6.8 Chromatographic Columns, short, liquid-solid. Thosefound satisfactory are as follows:6.8.1 Hypodermic Syringe Barrel, 5-cm3, fitted with aneedle about 35 mm in
18、length and 1.27 mm outside diameter(No. 18 BWG).6.8.2 Glass Tubes, 120 mm in length and 10 to 12 mm indiameter, holding about 5 cm3of silica gel.7. Reagents7.1 Plate AdsorbentSilica gel containing calcium sulfate.3Silica gel containing a fluorescent indicator may be useful insome cases to allow visu
19、alization of spots (before spraying)with ultraviolet light.7.2 Column AdsorbentSilica gel 200 to 600 m (30 to70-mesh),3activated by drying at 110C for at least 2 h, if dryin that period, or overnight (616 h) for convenience.7.3 SolventsUse of fume hoods with volatile and toxicsolvents is mandatory.
20、Approved health and safety precautionsshould be observed for the use of any solvent or chemicalmentioned in this procedure. ACS grade or equivalent shouldbe used.7.3.1 Methanol.7.3.2 Acetone.7.3.3 Isopropanol.7.3.4 Light Petroleum Ether.7.3.5 Chloroform.7.3.6 Toluene.7.3.7 Ethyl Acetate.7.3.8 n-Hexa
21、ne.7.3.9 n-Heptane.7.3.10 Cyclohexane.7.3.11 Diethylamine.7.3.12 Ammonium Hydroxide (NH4OH, 2830 % ammoniaNH3).7.3.13 WaterReferences to water shall be understood tomean distilled water or water of equal purity.7.4 Developing Solvents:7.4.1 Test Method A90 parts n-heptane and 10 parts ethylacetate b
22、y volume.7.4.2 Test Method B, used in the following order:7.4.2.1 Toluene.7.4.2.2 95 parts toluene and 5 parts ethyl acetate by volume.7.4.2.3 75 parts cyclohexane and 25 parts diethylamine byvolume.7.4.2.4 50 parts toluene and 50 parts n-heptane by volume.7.4.3 Additional developing solvents which
23、may proveuseful for special problems:7.4.3.1 100 parts toluene, 5 parts acetone and 0.1 partammonium hydroxide (NH4OH).7.4.3.2 100 parts toluene, 5 to 10 parts acetone and 0.1 to0.2 parts NH4OH.7.5 Spray Reagents for Color Development:7.5.1 Amines:7.5.1.1 Diazotized Sulfanilic Acid0.5 g of sulfanili
24、c acidand 0.5 g of potassium nitrite (KNO2) dissolved in 100 cm3of1 M hydrochloric acid (HCl). Make fresh daily.7.5.1.2 Benzoyl Peroxide (4 % solution in toluene).7.5.1.3 Tollens Reagent (0.5 cm3of 5 % silver nitrate(AgNO3) solution + 2 drops of 2 M sodium hydroxide (NaOH).Dissolve the precipitate i
25、n as little 2 % ammonium hydroxide(NH4OH) as possible, and add an equal volume of 96 %alcohol.7.5.1.4 Bismuth Nitrate (Bi(NO3)3) (7.5 g) dissolved in amixture of 1 cm3of concentrated nitric acid (HNO3, density1.42 Mg/m3) in 150 cm3of distilled water.7.5.1.5 Tetracyanoethylene (ethenetetracarbonitril
26、e)Saturated solution in methylene chloride.7.5.2 Phenols:7.5.2.1 Overspray, for use with solution 7.5.1.1 1-M so-dium hydroxide (NaOH) solution.7.5.2.2 p-Nitrophenyldiazonium Fluoroborate (1 % solu-tion in methanol containing 0.5 % hydrochloric acid (HCl,density 1.16 Mg/m3).7.5.2.3 2,6 Dichloroquino
27、nechlorimide (0.1 % solution inmethanol or toluene)Used with 7.5.2.4.7.5.2.4 Buffer Spray, for use with 7.5.2.3Dissolve 23.4 gof sodium tetraborate (Na2B4O7 10H2O) and 3.3 g of sodiumhydroxide (NaOH) in 1 dm3of water.7.6 Reagents for preliminary “screening” tests are as fol-lows:7.6.1 Ferric Chlorid
28、e SolutionMix 0.5 g of anhydrousferric chloride (FeCl3) with 100 cm3of ethanol or 3A alcohol.7.6.2 Ferric Sulfate SolutionMix1gofferric sulfate(FeSO4)3with 100 cm3of water.7.6.3 Hydroxylamine Hydrochloride SolutionMix 1.0 g ofhydroxylamine hydrochloride with 100 cm3of water.7.6.4 p-Nitroaniline Solu
29、tionMix 2.8 g of p-nitroanilinewith 32 cm3of hydrochloric acid (density 1.16 Mg/m3). Diluteto 250 cm3with water.7.6.5 Sodium Nitrite SolutionMix 1.44 g of sodium nitrite(NaNO2) with 250 cm3of water.7.6.6 Glacial Acetic Acid (99.7 % w/w).7.6.7 Titanium Tetrachloride SolutionMix the contents ofone 5-c
30、m3ampoule of titanium tetrachloride (TiCl4) with 1dm3of acetic acid (7.6.6).7.6.8 Anhydrous AlcoholsEthanol, 3A alcohol, or isopro-panol.3The sole source of supply of silica gel known to the committee at this time isE. Merck A.G., Frankfurter Str. 250, Darmstadt, Germany. If you are aware ofalternat
31、ive suppliers, please provide this information to ASTM InternationalHeadquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee,1which you may attend.D3156 96 (2011)28. Plate Preparation8.1 Make a slurry of 2 parts of water to 1 part of silica ge
32、l(7.1) by mass. Immediately, spread the slurry evenly over theglass plate with the spreading device. The layer thicknessshould be 250 to 300 m. Allow the plates to stand at roomtemperature to set the binder. Dry for 45 min at 105C.8.2 Plates may be spotted while warm, if it has been proventhat no de
33、composition of the antidegradant sought, takes place.Spotting, while warm, sometimes results in more compactspots.8.3 Plates may be stored in a desiccator over silica gel.Unused plates should be reactivated after 4 days standing.8.4 Before using, make “lanes” on the plate, about 20 mm inwidth, by sc
34、oring with a knife or scriber. If this step leads touneven development from lane to lane, eliminate.8.5 When precoated plates are used, follow the manufactur-ers directions for plate conditioning.9. Sampling9.1 Due to the nature of this practice and the wide variety ofcompounds, or products that may
35、 be examined by this practice,no directions are given for sampling other than that the selectedsample shall be at the discretion of the analyst.10. Preliminary “Screening” Tests10.1 Some preliminary spot tests that have been useful for“screening” possible antidegradant types prior to thin-layeranaly
36、sis are tabulated below. These tests are performed on afew cubic centimetres of an “extract” of about1gofmilledrubber, warmed in 10 cm3of anhydrous alcohol (7.6.8).10.1.1 Add dropwise 0.5 % ferric chloride (7.6.1) untilcolor appears; with excess reagent, the color changes to anoxidized form. Dialkyl
37、 phenylenediamines give a pink color,alkyl aryl phenylenediamines give a blue color, while diarylphenylenediamines give a green color.10.1.2 If no color was shown with the above, test forquinolines by adding 1 % aqueous ferric sulfate (7.6.2) plus1 % aqueous hydroxylamine hydrochloride (7.6.3). If q
38、uino-lines are present, a red color is observed. Phenylenediaminesinterfere.10.1.3 If no color was observed in 10.1.1, mix 10 cm3of asolution of p-nitroaniline (7.6.4) with 10 cm3of sodium nitritesolution (7.6.5). Cool mixture in an ice bath. Add this solutiondropwise to the sample solution with gla
39、cial acetic acid (7.6.6).Amine antidegradants (for example, phenyl-beta-naphthylamine and the condensation product of acetone-diphenylamine) give purple to red colors. Phenylenediaminesinterfere.10.2 Add 5 cm3of acetic acid (7.6.6)and5cm3of titaniumtetrachloride (7.6.7)to3cm3of “extract”. Most pheno
40、lics givea red color, except hindered phenols. Phenolic resins respondwith a red color also.11. Preparation of Test Specimen11.1 Sheet the test specimen thinly or cut into fine pieces (2by 2 by 2 mm) and place 2 to 5 g between the filter papersheets. Place in the extraction apparatus (6.7) and extra
41、ct withmethanol for 4 h, or 1 to 2 h for rapid reflux extraction. Analternative extraction procedure is to allow the specimen tostand overnight in isopropanol.11.2 Evaporate the extract from 11.1 in a beaker, using alow temperature hot plate (not more than 50C) and a stream ofnitrogen, to aid in eva
42、poration near the end of the evaporationstep. A rotary evaporator is helpful, if available. When about 1cm3of solution remains, examine for the presence of extenderoil. If present, proceed with 11.3, if absent, proceed directlywith the spotting of the thin-layer plate (Section 12).11.3 If visual exa
43、mination indicates the presence of oil,dissolve the residue in about 2 cm3of chloroform (CHCl3) andproceed with 11.4.11.4 Prepare a silica gel column from activated silica gel(7.2) by placing a glass wool plug at the end of the column(6.8.1 or 6.8.2) and fill immediately. Store in a desiccator nolon
44、ger than 1 to 2 h before using. Preferably, use a freshlyprepared column.11.5 Pour the CHCl3onto the dry silica gel column (11.4).Wash with n-hexane until the glass wool plug becomescolorless. Use a maximum of 25 cm3of n-hexane. The oils arelargely removed at this point.NOTE 1An alternative method f
45、or removing oil is to develop theprepared plate with light petroleum ether, until the oils have moved to thetop of the plate, carefully dry to remove the ether, then proceed with platedevelopment Section 13.11.6 After the last of the n-hexane has drained off thecolumn, place a clean beaker under the
46、 column tip. Washalternately with acetone and methanol until all the color isremoved, except a slight stain that normally cannot be removedeven with excessive washing. Discard the silica gel.11.7 Evaporate the eluant to dryness with gentle heating(maximum of 50C) and a stream of nitrogen. Dissolve i
47、n 0.5to 1.0 cm3of acetone or chloroform with gentle heating toobtain a clear solution and proceed to Section 12 for platespotting.12. Plate Spotting12.1 The technique of spotting thin-layer plates cannot bedescribed exactly. In the case of the antidegradants dealt within this method, a few general r
48、ules, or guidelines, are givenhere. Each operator must, however, develop his own techniqueby practice.12.1.1 Amount of SampleIn general, 50 to 100 g is thedesired amount of sample. Less can sometimes be used.12.1.2 Quantity of SolutionThe best chromatograms areobtained when the sample is applied in
49、a volume of 5 mm3(L)or less. 10 mm3is permissible, but larger volumes spread thespot and reduce separation efficiency.12.1.3 Concentration of SampleIt follows from 12.1.1and 12.1.2 that the ideal sampling technique would be to spotwithin the range froma1to2%solution. Some complexmixtures may produce streaks at this concentration. If streakingoccurs, it is advisable to decrease the amount of sample inorder to obtain discrete spots from the components of themixture.12.2 Spotting Technique:12.2.1 A plate, scored, with lanes (if desired) and ready
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