1、Designation: D7558 09 (Reapproved 2014)Standard Test Method forColorimetric/Spectrophotometric Procedure to QuantifyExtractable Chemical Dialkyldithiocarbamate, Thiuram, andMercaptobenzothiazole Accelerators in Natural RubberLatex and Nitrile Gloves1This standard is issued under the fixed designatio
2、n D7558; the number immediately following the designation indicates the year oforiginal adoption 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 rea
3、pproval.1. Scope1.1 This test method is designed to quantify the amount oftotal extractable accelerators in natural rubber latex (NRL) andnitrile gloves. Three common classes of rubber accelerators,the mercaptobenzothiazole (MBT), thiuram, and thiocarbamatetype compounds can be detected and quantifi
4、ed by this method.If the specific rubber accelerator(s) present in the glovematerial is not known, quantification is based on zinc dibutyl-dithiocarbamate (ZDBC) equivalents. This method will notdetect all potential rubber accelerators, including mercaptoben-zothiazole disulfide, dimorpholine, thiou
5、reas and diphenyldiamine.1.2 For the purpose of this test method, the range ofchemical accelerator measurement is based on the limit ofdetection (LOD) established in the performing laboratory.1.3 This test method should be performed by experiencedanalysts or under the supervision of those experience
6、d in theuse of spectroscopy and working with organic solvents.1.4 This test method has not been validated for measure-ment of long chain dithiocarbamates or accelerators from otherrubber products, such as lubricated condoms (1).2Althoughthis assay has been reported in the literature for the evaluati
7、onof accelerator levels in condoms, further validation for accel-erator measurement from other rubber products is required bythe testing laboratory prior to use.1.5 This test method is not designed to evaluate the potentialof rubber materials to induce or elicit Type IV skin sensitiza-tion reactions
8、 (for Type IV skin sensitization reactions see TestMethod D6355). Total extractable accelerator content does notreflect bioavailablity of individual accelerators that are de-tected and measured by this method. This test method shouldbe used to test and measure the total residual chemicalaccelerator
9、level in NRL and nitrile gloves under controlledlaboratory conditions, and should not be used to describe,appraise, or assess the hazard or risk of these materials orproducts under actual in-use conditions.1.6 The values stated in SI units are to be regarded asstandard. No other units of measurement
10、 are included in thisstandard.1.7 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 limitation
11、s prior to use.2. Referenced Documents2.1 ASTM Standards:3D3577 Specification for Rubber Surgical GlovesD3578 Specification for Rubber Examination GlovesD4483 Practice for Evaluating Precision for Test MethodStandards in the Rubber and Carbon Black ManufacturingIndustriesD6355 Test Method for Human
12、Repeat Insult Patch Testingof Medical Gloves3. Terminology3.1 Total thiol vulcanization accelerator includes MBT, zincdithiocarbamates (ZDTCs) and thiurams.3.2 Definitions:3.2.1 limit of detection (LOD), nthe lowest acceleratorconcentration that can be measured and be statistically differentfrom the
13、 blank.3.2.1.1 DiscussionThe LOD is expressed as 3.3 stan-dard error of the y-intercept of the standard plot regression linedivided by the slope of the calibration line.1This test method is under the jurisdiction of ASTM Committee D11 on Rubberand is the direct responsibility of Subcommittee D11.40
14、on Consumer RubberProducts.Current edition approved Nov. 1, 2014. Published December 2014. Originallyapproved in 2009. Last previous edition approved in 2009 as D7558 09. DOI:10.1520/D7558-09R14.2The boldface numbers in parentheses refer to a list of references at the end ofthis standard.3For refere
15、nced 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 website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West C
16、onshohocken, PA 19428-2959. United States13.2.2 limit of quantitation (LOQ), nthe lowest acceleratorconcentration that can be measured to produce quantitativelymeaningful results with acceptable precision and accuracy.3.2.2.1 DiscussionThe LOQ is expressed as 10 standarderror of the y-intercept of t
17、he standard plot regression linedivided by the slope of the calibration line.3.2.3 linear range, narea of a graph of absorbance versusconcentration that approximates a straight line.3.2.4 spectrophotometric measurement, n the unit of mea-sure of the instrument that is proportional to absorbance.3.2.
18、5 standard solution, nthe standard analyte to whichthe test (unknown) sample being measured is compared.4. Summary of Test Method4.1 The rubber material is cut into small pieces andapproximately1gisplaced into the extraction vessel.Acetoni-trile is added to give a final volume/weight of 10 mLacetoni
19、trile per gram of rubber. The extraction vessel issecurely capped, placed onto a rotator and extracted at approxi-mately 200 rpm for a minimum of 2 h at room temperature(25 6 5C). The acetonitrile extract is recovered and centri-fuged in a sealed centrifuge tube at 500 g for 20 min at roomtemperatur
20、e to remove any residual particulate matter. Theacetonitrile extract supernatant fluid is transferred to a cleancontainer and capped. Zinc dibutyldithiocarbamate (ZDBC)standards at 500 to 31.25 g/mL in acetonitrile and a blank areprepared. Cobalt chloride (10 L, 420 mmol/L) aqueoussolution is added
21、to 1 mL aliquots of each sample extract andstandard. Each individual solution is thoroughly mixed andthen incubated for 120 min at 50 6 5C. The extracts andstandards are cooled to room temperature for approximately 15min after the 50C incubation. A100 L aliquot of each isdiluted with 1.9 mL of aceto
22、nitrile. All are mixed thoroughlyand absorbance of each sample, blank and standard is mea-sured at 320 nm on a UV spectrophotometer. Concentration ofresidual accelerator is obtained by extrapolation from thestandard plot. Depending upon the number of samples tested,this test method takes about5htoco
23、mplete.5. Significance and Use5.1 Dialkyldithiocarbamates (DTCs), benzothiazoles, andthiurams are often used as vulcanization accelerators in NRLproducts. Zinc DTC accelerators are added either directly orare formed in situ during the vulcanization process via reactionbetween a thiuram(s) and zinc o
24、xide. DTCs, benzothiazoles,and thiurams have been detected in leachates from medicaldevices made of rubber such as gloves. Studies have shownthese chemicals can cause allergic contact dermatitis. A simpleselective method to monitor rubber accelerator levels in rubberextracts would be useful for qual
25、ity control, product screeningand research.5.2 This colorimetric assay measuresdialkyldithiocarbamates, including zinc dialkyldithiocarbam-ates (ZDTC), mercaptobenzothiazole (MBT) and thiurams as atotal thiol vulcanization accelerator level in rubber products. AUV spectrophotometer with detection at
26、 320 nm is used tomeasure the ZDTC, mercaptobenzothiazole and thiurams.Sample extracts diluted at 1:20 prior to measurement on thespectrophotometer is usually sufficient to quantify the residualaccelerator level from most commercially available rubbergloves; however, sample dilution can be adjusted
27、(from neatextract to 1:20 dilution) based on analytical needs. Thiuramsand ZDTCs complex with cobalt turning the extract to aconcentration-dependent shade of green. ZDTCs reacts quicklywhile thiurams react very slowly (requiring a heat catalyst).Mercaptobenzothiazole does not complex to Co(III), how
28、ever,it absorbs strongly at 320 nm. It can be distinguished from bothZDTCs and thiurams by its strong absorbance at 320 nmwithout the cobalt dependent visible green color. Cobaltcomplexed thiurams and ZDTCs, but not MBT, also have andabsorbance at 370 nm (2).6. Interferences6.1 Suspended solids such
29、 as powder or cotton flock caninterfere with spectrophotometric measurements and care mustbe taken not to resuspend particulate following centrifugation.Some extracts may require additional steps to remove particu-late such as higher speed centrifugation or possibly filtration,dependent on the physi
30、cal nature of the particulate material.The rubber accelerators, mercaptobenzothiazole disulfide,dimorpholine, thioureas, diphenyl diamine, and diphenylguani-dine are not detected by this assay and do not interfere withmeasurement of MBT or ZDTCs. Potential exists for interfer-ence from leached dyes
31、or other additives that absorb at 320nm; however, this has not been reported.7. Apparatus7.1 Polypropylene or Glass Extraction Tubes, with screwtop lids (50 mL, conical bottom).7.2 Polypropylene Cryotubes, (3.6 mL), with screw tops forcobalt reaction of extracts and standards and for the final 1/20d
32、ilution prior to UV analyses.7.3 Parafilm.7.4 Adjustable Positive Displacement Pipettes, (5 to 10 mL,1 mL and 250 L).7.5 Laboratory Shaker, (200 rpm).7.6 Laboratory Vortex Mixer.7.7 Water or Dry Bath, capable of maintaining the tempera-ture at 50C.7.8 Centrifuge, (capable up to 500 g).7.9 UV Spectro
33、photometer.8. Materials8.1 Chemical Accelerator StandardUse specific thiuram,zinc dithiocarbamate or mercaptobenzothiazole if specificspecies in the specimen is known.44If species is not known use zinc dibutyldithiocarbamate (ZDBC), the solesource of supply of which known to the committee at this ti
34、me is ChemService, Inc.,660 Tower Lane, PO Box 599, West Chester, PA 19381 (cat. No. Ou-76 (M.W. =474.2). If you are aware of alternative suppliers, please provide this information toASTM International Headquarters. Your comments will receive careful consider-ation at a meeting of the responsible te
35、chnical committee,1which you may attend.D7558 09 (2014)2NOTE 1Storage problems for zinc diethyldithiocarbamate have beenreported and care needs to be taken if this is to be used as the referencestandard.8.2 CoCl2Cobalt (II) Chloride hexahydrate.8.3 Water, (distilled/deionized (dH2O).8.4 Acetonitrile
36、, (HPLC grade).9. Standards and Reagent Preparation9.1 Stock ZDBCWeigh 10 mg ZDBC (or appropriateaccelerator standard) and add 10 mL acetonitrile (final concen-tration of 1000 g/mL). Mix until completely dissolved.(Prepare a fresh mixture immediately before use.)NOTE 2(1) To improve precision in wei
37、ghing milligram quantities ofchemical compounds, a larger mass may be used and dissolved in greatervolumes of solvent to yield a final concentration of 1 g/mL. In addition,it is easier and more accurate to adjust the volume of acetonitrile added tothe ZDBC vs. weighing exactly 10 or 100 mg to achiev
38、e the stocksolution. (2) It is advisable to use positive displacement pipettes foraccurate addition of acetonitrile due to its low surface tension. (3) Seal allvials with Parafilm around the screw caps to prevent leakage andevaporation.9.2 Prepare DilutionsStarting with the stock solution of1000 g/m
39、L ZDBC (or appropriate accelerator standard),perform five 1:1 serial dilutions using acetonitrile as the diluentto produce the following standard concentrations 500, 250,125, 62.5, and 31.25 g/mL (500 31.25 ppm). Ensure thateach standard is dissolved by thoroughly mixing before pro-ceeding with the
40、next dilution.NOTE 3If MBT is employed as the standard, the 500 g/mL standardabsorbance will be outside the linear range of the curve.9.3 Solvent BlankBlank spectrophotometer using reagentblank (see 12.3).9.4 Cobalt Chloride ReagentTo 50 mg of CoCl26H2Oadd 500 L dH2O (100 mg/mL).NOTE 4Larger masses
41、of CoCl26H2O may be used with appropriatevolume of dH2O to achieve a final concentration of 100 mg/mL (420mmol/L). This reagent is stable up to 1 month at room temperature in asealed container.10. Hazards10.1 Laboratory personnel should adhere to standard goodlaboratory practices. Care should be tak
42、en when working withall chemical reagents. Acetonitrile is a volatile solvent and allsolvent transfer steps should be conducted in a chemical hood.Chemical resistant glove use is recommended when handlingorganic solvents.11. Extraction11.1 Extraction MediumAcetonitrile.11.2 Test Specimen:11.2.1 Cut
43、the entire test specimen into small pieces (ap-proximately 1 cm2). Mix the small pieces to ensure that thesample analyzed is representative of the entire specimen. Aweight of at least 1 g sample should be placed in extractionsolution to provide a final concentration of 1 g sample/10 mLacetonitrile.
44、The test specimen weight used and acetonitrilevolume added should be recorded. Three separate 1 g/10 mLextracts should be prepared.11.2.2 Perform the extraction of each rubber test specimenusing the extraction solution as described below:11.2.2.1 The test specimen shall be extracted in acetonitrilef
45、or 2 h at a temperature of 25 6 5C using continuousshaking at approximately 200 rpm on laboratory shaker.Periodically check each sample visually to ensure that thespecimen pieces are covered with extraction solvent (that is,not adhering to vial wall above the solvent). Fifty-millilitrepolypropylene
46、conical bottom tubes work well for this purpose.If specimen pieces are above the solvent they can easily betapped down into the solvent without opening the vials.Wrapping the top of the tube with Parafilm after screwing onthe lid ensures a good seal to prevent potential loss/leakage ofsolvent.11.2.2
47、.2 Remove the samples from the shaker after extrac-tion. Separate the NRL/nitrile pieces from the acetonitrileextract by carefully decanting into a new 50 mL centrifugetube. Centrifuge the acetonitrile sample extract in a sealedcentrifuge tube at 500 g for 20 min at room temperature toremove any res
48、idual particulate matter. Separate the extractfrom residual particulate by carefully decanting or pipetting theextract to prevent re-suspension of the particulate. If extract iscloudy or visible particulate remains additional centrifugationor filtration is required to remove particulate.12. Colorime
49、tric/Spectrophotometric Assay12.1 Takea1mLaliquot of each of the ZDBC standarddilutions and add 10 Lof the CoCl2reagent solution into each.12.2 Takea1mLaliquot of each rubber extract test sampleand add 10 L of the CoCl2reagent solution into each. Repeatthis to provide duplicate measures for each test sample.12.3 Prepare a reagent blank using 1 mLthe acetonitrile and10 L of the CoCl2reagent solution.12.4 Mix all samples, standards and blanks thoroughly andthen incubate for 120 min at 50 6 5C. All lids should besealed with Parafilm
