1、Designation: D 1768 89 (Reapproved 2003)Standard Test Method forSodium Alkylbenzene Sulfonate in Synthetic Detergents byUltraviolet Absorption1This standard is issued under the fixed designation D 1768; the number immediately following the designation indicates the year oforiginal adoption or, in th
2、e case of 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. Scope1.1 This test method covers commercial synthetic deter-gents and built detergent formulat
3、ions 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
4、samples containing 30to 40% of active ingredient.1.2 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 re
5、gulatory limitations prior to use. Material SafetyData Sheets are available for reagents and materials. Reviewthem for hazards prior to usage.2. Referenced Documents2.1 ASTM Standards:D 460 Test Methods for Sampling and Chemical Analysisof Soaps and Soap Products2D 1568 Test Methods for Sampling and
6、 Chemical Analysisof Alkylbenzene Sulfonates2D 3049 Test Method for Synthetic Anionic Ingredient byCationic Titration2D 4251 Test Method for Active Matter in Anionic Surfac-tants by Potentiometric Titration2E 275 Practice for Describing and Measuring Performanceof Ultraviolet, Visible, and Near Infr
7、ared Spectrophotom-eters33. 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) and at a selectedbackground point of 270 nm in order to determine the amountof active ing
8、redient present. The percentage of active ingredi-ent is calculated from the above absorbances and data on thepure active ingredient.4. Apparatus4.1 Spectrophotometer,4equipped for liquid samples and formeasurements in the ultraviolet region. The instrument shall becapable of measuring absorbance wi
9、th 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 Absorption Cells,5silica, matched pairs of optical pathlength 1.000 6 0.005 cm.5. Reagent5.1
10、 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 cell and instrument.4Guard suchreference samples from contamination and renew periodically
11、(quarterly).7. Calibration and Standardization of Cells47.1 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 the manufacturer and use acorrection factor for each cell.7.2 Before each day of operation,
12、load 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
13、rinsed with freshly prepared distilled1This test method is under the jurisdiction of ASTM Committee D12 on Soapsand Other Detergents and is the direct responsibility of Subcommittee D12.12 onAnalysis of Soaps and Synthetic Detergents.Current edition approved May 26, 1989. Published July 1989. Origin
14、ally pub-lished as D 1768 60 T. Last previous edition D 1768 83.2Annual Book of ASTM Standards, Vol 15.04.3Annual Book of ASTM Standards, Vol 03.06.4For information on performance testing of spectrophotometers, refer to PracticeE 275.5One-centimetre silica cells manufactured by either the Pyrocell M
15、anufacturingCo., 270 E. 84th St., New York, NY, Catalog No. S22-240, or by BeckmanInstruments, Inc., Fullerton, CA, Catalog No. 40736 have been found satisfactoryfor this purpose.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.water
16、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 triplicate values for the percentage of org
17、anicalcohol-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 titration of Test Method D 3049 orby the spec
18、ific ion electrode titration of Test Method D 4251.8.2 Determine moisture in accordance with Moisture by theDistillation Method sections of Test Methods D 1568.8.3 Determine alcohol-insoluble matter in accordance withSections 19 to 20 (Total Matter Insoluble in Alcohol) of TestMethods D 460 or Total
19、 Matter Insoluble in Alcohol 20 to 22of Test Methods D 1568.8.4 Determine chlorides calculated as sodium chloride inaccordance with Chlorides Calculated as Sodium Chloride(NaCl) sections of Test Methods D 1568.8.5 Determine unsulfonated matter (neutral oil) in accor-dance with Neutral Oil sections o
20、f Test Methods D 1568.9. 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 temperature in avolumetric flask. M
21、ix 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 and dilute tovolume with water at room temperature. Carefully insert
22、 a TFE-fluorocarbon-covered stirring magnet and agitate vigorously on a mag-netic stirrer for 15 to 20 min. Carefully invert the flask several times toensure thorough mixing. If insoluble matter remains, allow the flask tostand for several hours, or preferably overnight. Then continue inaccordance w
23、ith 9.3 by pipetting the 5-mL aliquot from the top of thesupernatant solution.(2) Transfer the weighed sample to a 600-mL beaker. Add 200 mL ofwater and place on a steam bath or hot plate for about 10 min withoccasional stirring. Cool to room temperature and dilute to volume. A finestream of water o
24、r a few drops of alcohol will aid in breaking any foampersisting in the neck of the volumetric flask. As in (1), allow anyinsoluble matter to settle before continuing in accordance with 9.3 and 9.4.9.2 Slurry SampleWeigh, to the nearest 1 mg, threeapproximately 20-g portions of a representative samp
25、le. 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 flask, dilute to volume with
26、water 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 cells in the spectrophotomete
27、r, 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: There is danger of contamina
28、tion of the samplewith detergent dust in the production laboratory air; therefore, thesemeasurements must be made immediately after the procedure described in9.3. Contamination is evident when a high reading (above 0.1 absorbance)at 270 nm is obtained. Discard such contaminated samples and start wit
29、ha new 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 sample of the sodium alkylbenzene
30、 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 at either 220 nm or 228 nm.
31、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 percentages. Calculate the p
32、ercentage of alcohol-soluble matter in the sodium alkylbenzene sulfonate standard(or particular alkylbenzene sulfonate being determined) aspercent sodium alkylbenzene sulfonate as follows:Alcohol2soluble matter sodium alkylbenzene sulfonate!,%5 1002 M 1 A 1 B 1 C! (1)where:M = percentage of alcohol-
33、insoluble matter,A = percentage of moisture,B = percentage of sodium chloride, andC = percentage of neutral oil.Average the results of the three determinations, which shouldagree within 0.5 %.10.2 Absorptivity ValueCalculate the absorptivity value,a, for each of the three portions of the sodium alky
34、lbenz-esulfonate standard (or particular alkybenzene sulfonate beingdetermined) as follows:Absorptivity value, a 5 A2242 A270!/Msbc 3 100 (2)where:A = observed absorbance,Ms= percentage of organic alcohol-soluble matter in thesample (average of three determinations),b = cell length in centimetres, a
35、ndc = 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 A270!3 25/Wa 3 100 (3)D 1768 89 (2003)2
36、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 alkylbenzenesulfonate being determined (10.2).NOTE 7The calculation as written is based on th
37、e diluting andaliquoting scheme as described in 9.1-9.4 and the absorptivity value, a,ofproducts made from commercially available dodecylbenzenes. The calcu-lation may be adapted to general use as follows:Active ingredient sodium sulfonate!,%5 A2242 A270!/cb 3 100/a(4)where:A = observed absorbance,b
38、 = cell length in centimetres,c = concentration of final dilution in grams per 1000 mLanda = absorptivity value.11. Precision611.1 Repeatability (Single Analyst)The standard deviationof results (each of the average of duplicates), obtained by thesame analyst on different days, has been estimated to
39、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 different laboratories, ha
40、s 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 0.1.Duplicate runs tha
41、t 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 with any item mention
42、edin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and
43、 must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of
44、 theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box
45、C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).6Supporting data are available from ASTM Headquarters, 100 Barr HarborDrive, West Conshohoken, PA 19428. Request RR:D12-1001.D 1768 89 (2003)3
