Monograph pubs.acs.org/doi/book/10.1021/acsreagents
Sodium Dodecyl Sulfate (SDS; Sodium Lauryl Sulfate) Part 4, Monographs for Reagent Chemicals: General Descriptions, Specifications, and Tests eISBN: 9780841230460 Tom Tyner Chair, ACS Committee on Analytical Reagents James Francis Secretary, ACS Committee on Analytical Reagents
ABSTRACT This monograph for Sodium Dodecyl Sulfate provides, in addition to common physical constants, a general description including typical appearance, applications, and aqueous solubility. The monograph also details the following specifications and corresponding tests for verifying that a substance meets ACS Reagent Grade specifications including: Assay, Fatty Alcohols, Absorbance, Loss on Drying, Titrable Base, Heavy Metals, and Unsulfated Alcohols.
CH3(CH2)11SO4Na
Formula Wt 288.38
CAS No. 151-21-3
GENERAL DESCRIPTION Typical appearance . . . . . . . . . . . . . . . . . . . white solid Applications . . . . . . . . . . . . . . . . . . . . . . . . wetting agent; electrophoretic separation of proteins and lipids Aqueous solubility . . . . . . . . . . . . . . . . . . . . soluble
SPECIFICATIONS Assay (acidimetric, on dried basis) . . . . . . . . . ≥99.0% C12H25NaO4S Fatty alcohols (as C12H25OH) . . . . . . . . . . . . . >96.0%
Absorbance (3% w/v) Loss on drying . . . . Titrable base . . . . . Heavy metals (as Pb) Unsulfated alcohols .
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© 2017 American Chemical Society
Maximum Allowable 0.1 AU 1.0% 0.06 meq/g 0.002% 4.0%
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DOI:10.1021/acsreagents.4346 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
TESTS Assay Weigh accurately about 5.0 g, transfer to a 500 mL round-bottom flask equipped with a ground-glass joint. Add 25.0 mL of 1 N sulfuric acid, and attach a condenser. Using a heating mantle and a magnetic stirrer, heat cautiously and gently at about 100 °C until foaming ceases (about 4 h). Boil under reflux for 3–4 h or more after foaming ceases. Cool, and wash the condenser with 30 mL of ethanol and then 30 mL of water. Titrate with 1 N sodium hydroxide volumetric solution, using 0.15 mL of phenolphthalein indicator solution. Perform a complete blank. One milliliter of 1 N sodium hydroxide corresponds to 0.2884 g C12H25NaO4S. Correct the assay value for loss on drying.
Fatty Alcohols
Sample Preparation for the Determination of Fatty Alcohols Using a 150 mL glass-stoppered conical flask, warm 25 mL of distilled water on a hot plate (~100 °C). Add approximately 2 g of sample and dissolve. Add 5 mL of hydrochloric acid, connect a cold finger condenser, and let reflux for 2 h. When hydrolysis is complete and the molten fatty alcohol has separated as a completely clear liquid, cool the flask to 0 °C by using an ice bath. (Note: This should be done with minimum disturbance to the separated fatty alcohol. It is desirable to solidify the fatty alcohol in one piece without increasing the surface area or allowing occluded water to be introduced.) Prepare a funnel with a suitable filter paper, and transfer the fatty alcohol and solution to the funnel. Wash the solid fatty alcohol with cold water. The fatty alcohol may be broken up and transferred to the filter. However, this should only be done after the first washing. Using a dry filter paper, blot the fatty alcohol dry.
Chromatographic Conditions for the Determination of Fatty Alcohols Column . . . . . . . . . . Column Temperature . Injector Temperature . Detector Temperature Sample Size . . . . . . . Carrier Gas . . . . . . . Detector . . . . . . . . .
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Type I, methyl silicone 80 to 230 °C, programmed at 10 °C/min, hold 5 min at 230 °C 220 °C 250 °C 0.2 µL Helium at 6 mL/min Flame ionization
S t a n d a r d S o l u t i o n . Accurately weigh 0.10 g of pure dodecyl alcohol, and transfer to a 50 mL volumetric flask. Dissolve and dilute to volume with hexanes. Mix well, and stopper. S a m p l e S o l u t i o n . Accurately weigh 0.10 g of the dried fatty alcohol from the sample preparation, and transfer to a 50 mL volumetric flask. Dissolve, and dilute to volume with hexanes. Mix well, and stopper.
Consecutively inject the standard and sample solutions into a prepared gas chromatograph. Record the chromatogram for the duration of the temperature-programmed run. Electronically integrate the area under the peaks of interest. Determine the amount of dodecyl alcohol (C12) in the sample by a conventional area normalization calculation. Correct for assay content of dodecyl alcohol.
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4346 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
Absorbance Determine the absorbance of 3.0% w/v aqueous solution in 10 mm silica or quartz cuvettes over the range 220 to 350 nm against water as the reference. The absorbance does not exceed 0.1.
Loss on Drying Weigh accurately about 2 g, and in a preconditioned crucible dry at 105 °C to constant weight.
Titrable Base Dissolve 1.0 g in 100 mL of water, add 0.15 mL phenol red indicator solution, and titrate with 0.1 N hydrochloric acid. Not more than 0.60 mL is required for neutralization.
Heavy Metals [Part 2: Colorimetry and Turbidimetry; Heavy Metals (as Lead); Procedure for Heavy Metals, Method 2]. Use 1.0 g.
Unsulfated Alcohols Dissolve about 10 g, accurately weighed, in 100 mL of water, and add 100 mL of ethyl alcohol. Transfer the solution to a separator, and extract with three 50 mL portions of solvent hexane. If an emulsion forms, sodium chloride may be added to promote separation of the two layers. Wash the combined solvent hexane extracts with three 50 mL portions of water, and dry with anhydrous sodium sulfate. Filter the solvent hexane extract into a tared beaker, evaporate on a steam bath until the hexane is completely volatilized, dry the residue at 105 °C for 30 min, cool, and weigh. The weight of the residue is not more than 4.0% of the weight of the sodium dodecyl sulfate taken.
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4346 ACS Reagent Chemicals, Part 4
