1、Designation: D1768 89 (Reapproved 2016)Standard Test Method forSodium Alkylbenzene Sulfonate in Synthetic Detergents byUltraviolet Absorption1This standard is issued under the fixed designation D1768; the number immediately following the designation indicates the year oforiginal adoption or, in the
2、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 test method covers commercial synthetic deter-gents and built detergent formulation
3、s that do not containorganic additives such as amides. Optical dyes and materialsnormally found in formulated detergents do not interfere;however, materials other than sulfonates that possess strongultraviolet absorptions must be absent. The indicated samplesize and aliquoting scheme is based on sam
4、ples containing 30to 40% of active ingredient.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility
5、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. Material SafetyData Sheets are available for reagents and materials. Reviewthem for hazards prior to usage.2. Referenced Documents2.1 ASTM Stand
6、ards:2D460 Test Methods for Sampling and Chemical Analysis ofSoaps and Soap ProductsD1568 Test Methods for Sampling and ChemicalAnalysis ofAlkylbenzene SulfonatesD3049 Test Method for Synthetic Anionic Ingredient byCationic TitrationD4251 Test Method forActive Matter inAnionic Surfactantsby Potentio
7、metric TitrationE275 Practice for Describing and Measuring Performance ofUltraviolet and Visible Spectrophotometers3. Summary of Test Method3.1 This test method involves measurement of the ultravio-let absorbance of the sample at the maximum absorbance pointfor sodium alkylbenzene sulfonate (224 nm)
8、 and at a selectedbackground point of 270 nm in order to determine the amountof active ingredient present. The percentage of active ingredi-ent is calculated from the above absorbances and data on thepure active ingredient.4. Apparatus4.1 Spectrophotometer,3equipped for liquid samples and formeasure
9、ments in the ultraviolet region. The instrument shall becapable of measuring absorbance with a repeatability of60.5 % or better from an average at the 0.4 absorbance levelin the spectral region between 220 and 270 nm. The spectralpositions shall be accurate to 60.5 nm and repeatable to 60.2nm.4.2 Ab
10、sorption Cells,4silica, matched pairs of optical pathlength 1.000 6 0.005 cm.5. Reagent5.1 Ethyl Alcohol (95 %) Conforming to either FormulaNo. 3A or No. 30 of the U.S. Bureau of Internal Revenue.6. Reference Standard6.1 A previously analyzed sample or solution may be usedto check performance of the
11、 cell and instrument.3Guard suchreference samples from contamination and renew periodically(quarterly).7. Calibration and Standardization of Cells37.1 The cells in a pair, when filled with distilled water,should match within 1 % transmittance at 224 nm. Otherwise,calibrate the cells as directed by t
12、he manufacturer and use acorrection factor for each cell.1This test method is under the jurisdiction of ASTM Committee D12 on Soapsand Other Detergents and is the direct responsibility of Subcommittee D12.12 onAnalysis and Specifications of Soaps, Synthetics, Detergents and their Components.Current
13、edition approved July 1, 2016. Published August 2016. Originallyapproved in 1960 as D1768 60 T. Last previous edition approved in 2009 asD1768 89(2009). DOI: 10.1520/D1768-89R16.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org.
14、For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3For information on performance testing of spectrophotometers, refer to PracticeE275.4One-centimetre silica cells manufactured by either the Pyrocell ManufacturingCo., 270 E. 84th St.
15、, New York, NY, Catalog No. S22-240, or by BeckmanInstruments, Inc., Fullerton, CA, Catalog No. 40736 have been found satisfactoryfor this purpose.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States17.2 Before each day of operation, load
16、the quartz cells withdistilled water and make certain that the cells match within 1 %transmittance. This practice is necessary to check cleanlinessof the cells. Clean cells, if necessary, using dichromatecleaning solution, until the desired transmittance is obtained.NOTE 1All glassware must be rinse
17、d with freshly prepared distilledwater before use. Do not dry the rinsed glassware. This is necessary,especially after the first dilution, to avoid errors due to contamination.8. Determination of Purity of Sodium AlkylbenzeneSulfonate Standard from its Organic Alcohol-SolubleMatter8.1 Determine trip
18、licate values for the percentage of organicalcohol-soluble matter in the alkylbenzene sulfonate standard(or particular alkylbenzene sulfonate being determined) inaccordance with 8.2 8.5.NOTE 2The purity of the standard, or percentage of active ingredient,can also be determined by the cationic titrat
19、ion of Test Method D3049 orby the specific ion electrode titration of Test Method D4251.8.2 Determine moisture in accordance with Moisture by theDistillation Method sections of Test Methods D1568.8.3 Determine alcohol-insoluble matter in accordance withSections 19 to 20 (Total Matter Insoluble in Al
20、cohol) of TestMethods D460 or Total Matter Insoluble inAlcohol 20 to 22 ofTest Methods D1568.8.4 Determine chlorides calculated as sodium chloride inaccordance with Chlorides Calculated as Sodium Chloride(NaCl) sections of Test Methods D1568.8.5 Determine unsulfonated matter (neutral oil) in accor-d
21、ance with Neutral Oil sections of Test Methods D1568.9. Determination of Active Ingredient9.1 Powders and Solid SamplesWeigh, to the nearest 0.1mg, three 0.9 to 1.1-g portions of a representative sample.Dissolve each portion of the sample in water (Note 3) anddilute to 500 mL with water at room temp
22、erature in avolumetric flask. Mix well. Treat each portion of the samplesolution in accordance with 9.3 and 9.4.NOTE 3It is desirable for the sample to be completely dissolved. Itmay be dissolved as follows:(1) Transfer the weighed sample to the volumetric flask anddilute to volume with water at roo
23、m temperature. Carefullyinsert a TFE-fluorocarbon-covered stirring magnet and agitatevigorously on a magnetic stirrer for 15 to 20 min. Carefullyinvert the flask several times to ensure thorough mixing. Ifinsoluble matter remains, allow the flask to stand for severalhours, or preferably overnight. T
24、hen continue in accordancewith 9.3 by pipetting the 5-mL aliquot from the top of thesupernatant solution.(2) Transfer the weighed sample to a 600-mL beaker. Add200 mL of water and place on a steam bath or hot plate forabout 10 min with occasional stirring. Cool to room tempera-ture and dilute to vol
25、ume.Afine stream of water or a few dropsof alcohol will aid in breaking any foam persisting in the neckof the volumetric flask. As in (1), allow any insoluble matter tosettle before continuing in accordance with 9.3 and 9.4.9.2 Slurry SampleWeigh, to the nearest 1 mg, threeapproximately 20-g portion
26、s of a representative sample. Add50 mL of alcohol and mix to disperse the sample. Dissolveeach portion of the sample in water (Note 3) and dilute to 1000mL with water at room temperature, employing a 1000-mLvolumetric flask. Mix well. Pipet a 50-mL aliquot of eachsolution into a 500-mL volumetric fl
27、ask, dilute to volume withwater at room temperature, and mix well. Treat each of thethree sample solutions as directed in 9.3 and 9.4.9.3 Pipet a 5-mL aliquot of the solution from 9.1 or 9.2 intoa 250-mL volumetric flask and dilute to volume with water atroom temperature. Mix well.9.4 Using 1-cm cel
28、ls in the spectrophotometer, measure theabsorbance at 224 and 270 nm versus a water blank. Withinstruments having scanning capability, scan from 300 down to210 nm. This facilitates obtaining the absorbance at the peakmaximum near 224 nm. (Caution, Note 4. See also Note 5 andNote 6).NOTE 4Caution: Th
29、ere is danger of contamination of the sample withdetergent dust in the production laboratory air; therefore, these measure-ments must be made immediately after the procedure described in 9.3.Contamination is evident when a high reading (above 0.1 absorbance) at270 nm is obtained. Discard such contam
30、inated samples and start with anew aliquot (9.3, Note 5 and Note 6).NOTE 5The observed absorbance readings should be between 0.2 and0.9; otherwise weigh a new sample or take a new or different aliquot anddilute to a known volume. (A calibration curve in this absorbance rangemust be made with a sampl
31、e of the sodium alkylbenzene sulfonate beingquantitatively measured. See also Note 7.)NOTE 6When analyzing samples of doubtful origin, the absorptionmaximum at 224 nm should be checked. Measure the absorbance at 220,224, 228, and 270 nm. The absorbance at 224 nm should be greater thanthe absorbance
32、at either 220 nm or 228 nm. If the 224-nm absorption is notthe maximum of all the absorbance readings, alkylbenzene sulfonate is notresponsible for the observed absorption and the spectrophotometricmethod is invalid.10. Calculation10.1 Alcohol-Soluble MatterAll percentages appearing in10 are weight
33、percentages. Calculate the percentage of alcohol-soluble matter in the sodium alkylbenzene sulfonate standard(or particular alkylbenzene sulfonate being determined) aspercent sodium alkylbenzene sulfonate as follows:Alcohol 2 soluble matter sodium alkylbenzene sulfonate!,%5 1002 M1A1B1C! (1)where:M
34、= percentage of alcohol-insoluble matter,A = percentage of moisture,B = percentage of sodium chloride, andC = percentage of neutral oil.Average the results of the three determinations, whichshould agree within 0.5 %.10.2 Absorptivity ValueCalculate the absorptivity value,a, for each of the three por
35、tions of the sodium alkylbenzesul-fonate standard (or particular alkybenzene sulfonate beingdetermined) as follows:Absorptivity value, a 5 A2242 A270!/Msbc 3100 (2)D1768 89 (2016)2where:A = observed absorbance,Ms= percentage of organic alcohol-soluble matter in thesample (average of three determinat
36、ions),b = cell length in centimetres, andc = concentration of final dilution in grams per 1000 mL.Average the three results.10.3 Active IngredientCalculate the percentage of activeingredient (sodium alkylbenzene sulfonate) as follows (Note7):Active ingredient sodium alkylbenzene sulfonate!,%5 A2242
37、A270!325/Wa 3100 (3)where:A = observed absorbance at 224 and 270 nm (average ofthree results),W = grams of sample used (9.1) or grams of samplerepresented in the aliquot used (9.2), anda = absorptivity value for the particular alkylbenzene sul-fonate being determined (10.2).NOTE 7The calculation as
38、written is based on the diluting andaliquoting scheme as described in 9.1 9.4 and the absorptivity value, a,of products made from commercially available dodecylbenzenes. Thecalculation may be adapted to general use as follows:Active ingredient sodium sulfonate!,%5 A2242 A270!/cb 3100/a(4)where:A = o
39、bserved absorbance,b = cell length in centimetres,c = concentration of final dilution in grams per 1000 mL anda = absorptivity value.11. Precision511.1 Repeatability (Single Analyst)The standard deviationof results (each of the average of duplicates), obtained by thesame analyst on different days, h
40、as been estimated to be 0.34 %absolute at 10 df. Two such averages should be consideredsuspect (95 % confidence level) if they differ by more than1.07 % absolute.11.2 Reproducibility (multilaboratory)The standard de-viation of results (each of the average of duplicates), obtainedby analysts in diffe
41、rent laboratories, has been estimated to be0.95 % of absolute at 4 df. Two such averages should beconsidered suspect (95 % confidence level) if they differ bymore than 3.72 % absolute.11.3 Checking Limits for DuplicatesReport the percent ofsodium alkylbenzene sulfonate of the sample to the nearest 0
42、.1.Duplicate runs that agree within 0.86 % absolute are acceptablefor averaging (95 % confidence level).12. Keywords12.1 sodium alkylbenzene sulfonate; synthetic detergents;ultraviolet absorptionASTM International takes no position respecting the validity of any patent rights asserted in connection
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