ASTM D1768-89(2016)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D1768 − 89 (Reapproved 2016)
Standard Test Method for
Sodium Alkylbenzene Sulfonate in Synthetic Detergents by
Ultraviolet Absorption
This standard is issued under the fixed designation D1768; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3. Summary of Test Method
1.1 This test method covers commercial synthetic deter- 3.1 This test method involves measurement of the ultravio-
gents and built detergent formulations that do not contain let absorbance of the sample at the maximum absorbance point
organic additives such as amides. Optical dyes and materials for sodium alkylbenzene sulfonate (224 nm) and at a selected
normally found in formulated detergents do not interfere; background point of 270 nm in order to determine the amount
however, materials other than sulfonates that possess strong of active ingredient present. The percentage of active ingredi-
ultraviolet absorptions must be absent. The indicated sample ent is calculated from the above absorbances and data on the
size and aliquoting scheme is based on samples containing 30 pure active ingredient.
to 40% of active ingredient.
4. Apparatus
1.2 The values stated in SI units are to be regarded as
4.1 Spectrophotometer, equipped for liquid samples and for
standard. No other units of measurement are included in this
measurements in the ultraviolet region.The instrument shall be
standard.
capable of measuring absorbance with a repeatability of
1.3 This standard does not purport to address all of the
60.5 % or better from an average at the 0.4 absorbance level
safety concerns, if any, associated with its use. It is the
in the spectral region between 220 and 270 nm. The spectral
responsibility of the user of this standard to establish appro-
positions shall be accurate to 60.5 nm and repeatable to 60.2
priate safety and health practices and determine the applica-
nm.
bility of regulatory limitations prior to use. Material Safety
4.2 Absorption Cells, silica, matched pairs of optical path
Data Sheets are available for reagents and materials. Review
length 1.000 6 0.005 cm.
them for hazards prior to usage.
5. Reagent
2. Referenced Documents
5.1 Ethyl Alcohol (95 %) —Conforming to either Formula
2.1 ASTM Standards:
No. 3A or No. 30 of the U.S. Bureau of Internal Revenue.
D460 Test Methods for Sampling and Chemical Analysis of
Soaps and Soap Products
6. Reference Standard
D1568 TestMethodsforSamplingandChemicalAnalysisof
Alkylbenzene Sulfonates 6.1 A previously analyzed sample or solution may be used
D3049 Test Method for Synthetic Anionic Ingredient by
to check performance of the cell and instrument. Guard such
Cationic Titration reference samples from contamination and renew periodically
D4251 TestMethodforActiveMatterinAnionicSurfactants
(quarterly).
by Potentiometric Titration
7. Calibration and Standardization of Cells
E275 Practice for Describing and Measuring Performance of
Ultraviolet and Visible Spectrophotometers
7.1 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 a
This test method is under the jurisdiction of ASTM Committee D12 on Soaps
correction factor for each cell.
and Other Detergents and is the direct responsibility of Subcommittee D12.12 on
Analysis and Specifications of Soaps, Synthetics, Detergents and their Components.
Current edition approved July 1, 2016. Published August 2016. Originally
approved in 1960 as D1768 – 60 T. Last previous edition approved in 2009 as Forinformationonperformancetestingofspectrophotometers,refertoPractice
D1768 – 89(2009). DOI: 10.1520/D1768-89R16. E275.
2 4
For referenced ASTM standards, visit the ASTM website, www.astm.org, or One-centimetre silica cells manufactured by either the Pyrocell Manufacturing
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Co., 270 E. 84th St., New York, NY, Catalog No. S22-240, or by Beckman
Standards volume information, refer to the standard’s Document Summary page on Instruments, Inc., Fullerton, CA, Catalog No. 40736 have been found satisfactory
the ASTM website. for this purpose.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D1768 − 89 (2016)
7.2 Before each day of operation, load the quartz cells with 9.2 Slurry Sample—Weigh, to the nearest 1 mg, three
distilledwaterandmakecertainthatthecellsmatchwithin1 % approximately 20-g portions of a representative sample. Add
transmittance. This practice is necessary to check cleanliness 50 mL of alcohol and mix to disperse the sample. Dissolve
of the cells. Clean cells, if necessary, using dichromate each portion of the sample in water (Note 3) and dilute to 1000
cleaning solution, until the desired transmittance is obtained.
mL with water at room temperature, employing a 1000-mL
volumetric flask. Mix well. Pipet a 50-mL aliquot of each
NOTE 1—All glassware must be rinsed with freshly prepared distilled
solution into a 500-mL volumetric flask, dilute to volume with
water before use. Do not dry the rinsed glassware. This is necessary,
water at room temperature, and mix well. Treat each of the
especially after the first dilution, to avoid errors due to contamination.
three sample solutions as directed in 9.3 and 9.4.
8. Determination of Purity of Sodium Alkylbenzene
9.3 Pipet a 5-mLaliquot of the solution from 9.1 or 9.2 into
Sulfonate Standard from its Organic Alcohol-Soluble
a 250-mL volumetric flask and dilute to volume with water at
Matter
room temperature. Mix well.
8.1 Determinetriplicatevaluesforthepercentageoforganic
9.4 Using 1-cm cells in the spectrophotometer, measure the
alcohol-soluble matter in the alkylbenzene sulfonate standard
absorbance at 224 and 270 nm versus a water blank. With
(or particular alkylbenzene sulfonate being determined) in
instrumentshavingscanningcapability,scanfrom300downto
accordance with 8.2 – 8.5.
210 nm. This facilitates obtaining the absorbance at the peak
NOTE 2—The purity of the standard, or percentage of active ingredient,
maximum near 224 nm. (Caution, Note 4. See also Note 5 and
can also be determined by the cationic titration of Test Method D3049 or
Note 6).
by the specific ion electrode titration of Test Method D4251.
NOTE4—Caution:Thereisdangerofcontaminationofthesamplewith
8.2 Determine moisture in accordance with Moisture by the
detergent dust in the production laboratory air; therefore, these measure-
Distillation Method sections of Test Methods D1568.
ments must be made immediately after the procedure described in 9.3.
Contamination is evident when a high reading (above 0.1 absorbance) at
8.3 Determine alcohol-insoluble matter in accordance with
270 nm is obtaine
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