ASTM D2330-20

Standard Test Method for Methylene Blue Active Substances

SIGNIFICANCE AND USE
5.1 The widespread use and discharge of detergents into surface waters can result in a lowering of its aesthetic quality by foam formation and by causing toxicity to aquatic wildlife. This test method is capable of detecting small concentrations of detergents as MBAS so that they can be controlled to prevent such problems.  
5.2 Biodegradable linear alkyl benzene sulfonates (LAS) have replaced the branched-chain alkyl benzene sulfonates (ABS) in detergent formulations, which were more resistant to biodegradation. Differentiation between linear and branched-chain alkyl benzene sulfonates, as well as differentiation of the various positional isomers of either type, is not possible by this test method. While the methylene blue method may be employed to monitor studies designed to measure biodegradability, it cannot be used to predict this quality.
SCOPE
1.1 This test method covers the determination of compounds that react with methylene blue under the conditions specified in the test procedure. They are referred to as methylene blue active substances (MBAS), and are calculated and reported in terms of the reference material, linear alkyl benzene sulfonate, LAS.  
1.2 This test method is applicable for determining MBAS in water and wastewater. It is the user's responsibility to ensure the validity of this test method for waters of untested matrices.  
1.3 This test method is a simple, rapid, control procedure suitable for monitoring the effectiveness of a biodegradation or other linear alkyl benzene sulfonate (LAS) removal process. For greater specificity and interference removal, the pretreatment procedure in Annex A1 should be used. Data derived without the pretreatment procedure should be interpreted with care. This test method is applicable in the range from 0.03 to 1.5 mg/L for a 100-mL sample.  
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. For a specific hazard statement, see 8.3.  
1.6 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.

General Information

• Status: Published
• Publication Date: 31-Dec-2019
• ICS: 13.060.50 - Examination of water for chemical substances
• Technical Committee: D19 - Water
• Drafting Committee: D19.06 - Methods for Analysis for Organic Substances in Water

Relations

• Replaces: ASTM D2330-02 - Standard Test Method for Methylene Blue Active Substances (Withdrawn 2011)
• Effective Date: 01-Jan-2020
• Refers: ASTM D5788-95(2024) - Standard Guide for Spiking Organics into Aqueous Samples
• Effective Date: 01-Apr-2024
• Refers: ASTM D1129-13(2020)e2 - Standard Terminology Relating to Water
• Effective Date: 01-May-2020
• Refers: ASTM D5788-95(2017) - Standard Guide for Spiking Organics into Aqueous Samples
• Effective Date: 15-Dec-2017
• Refers: ASTM D459-16 - Standard Terminology Relating to Soaps and Other Detergents
• Effective Date: 01-Jul-2016
• Refers: ASTM D3856-11 - Standard Guide for Management Systems in Laboratories Engaged in Analysis of Water
• Effective Date: 15-Nov-2011
• Refers: ASTM D5788-95(2011) - Standard Guide for Spiking Organics into Aqueous Samples
• Effective Date: 01-May-2011
• Refers: ASTM D3370-10 - Standard Practices for Sampling Water from Closed Conduits
• Effective Date: 01-Dec-2010
• Refers: ASTM D1129-10 - Standard Terminology Relating to Water
• Effective Date: 01-Mar-2010
• Refers: ASTM E131-10 - Standard Terminology Relating to Molecular Spectroscopy
• Effective Date: 01-Mar-2010
• Refers: ASTM D459-09 - Standard Terminology Relating to Soaps and Other Detergents <a href="#fn00002"></a>
• Effective Date: 01-Oct-2009
• Refers: ASTM D459-08a - Standard Terminology Relating to Soaps and Other Detergents <a href="#fn00002"></a>
• Effective Date: 15-Oct-2008
• Refers: ASTM E275-08 - Describing and Measuring Performance of Ultraviolet and Visible Spectrophotometers
• Effective Date: 15-Oct-2008
• Refers: ASTM D3370-08 - Standard Practices for Sampling Water from Closed Conduits
• Effective Date: 01-Oct-2008
• Refers: ASTM D459-08 - Standard Terminology Relating to Soaps and Other Detergents <a href="#fn00002"></a>
• Effective Date: 15-Jul-2008

Overview

ASTM D2330-20: Standard Test Method for Methylene Blue Active Substances (MBAS) provides a reliable method for detecting and quantifying substances in water and wastewater that react with methylene blue dye. These substances, known as methylene blue active substances, are primarily anionic surfactants like linear alkyl benzene sulfonates (LAS) used in detergents. The method is widely used to monitor and control the presence of detergent-related compounds in environmental water sources, helping prevent foam formation and toxicity to aquatic life.

This test method is recognized by regulatory bodies and developed in accordance with internationally accepted standardization principles, including guidance from the World Trade Organization's Technical Barriers to Trade (TBT) Committee.

Key Topics

• Detection of Detergents: The core focus is on measuring low concentrations of anionic surfactant pollutants in surface waters and wastewater, notably linear alkyl benzene sulfonates (LAS), calculated as MBAS.
• Environmental Impact: By detecting these surfactants, regulatory authorities and industries can prevent aesthetic degradation (such as foaming) and potential toxicity in aquatic ecosystems.
• Sample Range and Applicability: The method is effective for MBAS concentrations ranging from 0.03 to 1.5 mg/L in a 100-mL sample. It can be applied to both treated and untreated water and wastewater.
• Pretreatment for Interference: The standard includes provisions for a specialized pretreatment procedure to remove substances that might interfere with measurement, ensuring specificity.
• Control Procedure: This is a straightforward, rapid protocol suitable for routine monitoring of water quality or the effectiveness of detergent removal and biodegradation processes.

Applications

• Environmental Compliance Monitoring: Used by government agencies, water treatment plants, and environmental labs to ensure that detergent levels in discharged water comply with regulatory limits.
• Wastewater Treatment Assessment: Helps operators of municipal and industrial wastewater facilities assess the performance of their treatment systems in removing synthetic detergents, especially LAS.
• Detergent Manufacturing: Enables manufacturers to evaluate how products perform in terms of biodegradability and environmental impact.
• Water Quality Studies: Valuable for researchers conducting water pollution, biodegradability, and surfactant residue studies.
• Quality Assurance and Control: Provides a standardized procedure for laboratories to consistently and accurately detect anionic surfactants in a variety of water matrices.

Related Standards

• ASTM D1129: Terminology Relating to Water
• ASTM D1193: Specification for Reagent Water
• ASTM D3370: Practices for Sampling Water from Flowing Process Streams
• ASTM D3856: Guide for Management Systems in Laboratories Engaged in Analysis of Water
• ASTM D459: Terminology Relating to Soaps and Other Detergents
• ASTM E60 and ASTM E275: Practices involving spectrophotometric analysis and equipment requirements

Practical Value

Implementing ASTM D2330-20 ensures accurate and consistent detection of methylene blue active substances in water systems, supporting regulatory compliance and environmental protection efforts. The ease of use, broad applicability, and clear quality control guidelines make it an essential method for any laboratory or facility involved in water quality monitoring, pollution control, or surfactant analysis. Maintaining water quality by monitoring detergent residues not only safeguards public health and aquatic ecosystems but also upholds sustainability standards in detergent manufacturing and wastewater management.

Keywords: ASTM D2330-20, methylene blue active substances, MBAS, linear alkyl benzene sulfonate, LAS, anionic surfactants, water quality, wastewater, detergent monitoring, environmental compliance, spectrophotometry

Standards Content (Sample)

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: D2330 − 20
Standard Test Method for
Methylene Blue Active Substances
This standard is issued under the fixed designation D2330; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope 2. Referenced Documents
2.1 ASTM Standards:
1.1 This test method covers the determination of com-
D459Terminology Relating to Soaps and Other Detergents
pounds that react with methylene blue under the conditions
D1129Terminology Relating to Water
specified in the test procedure. They are referred to as
D1193Specification for Reagent Water
methylene blue active substances (MBAS), and are calculated
D3370Practices for Sampling Water from Flowing Process
and reported in terms of the reference material, linear alkyl
Streams
benzene sulfonate, LAS.
D3856Guide for Management Systems in Laboratories
1.2 ThistestmethodisapplicablefordeterminingMBASin
Engaged in Analysis of Water
water and wastewater. It is the user’s responsibility to ensure
D4210Practice for Intralaboratory Quality Control Proce-
the validity of this test method for waters of untested matrices.
dures and a Discussion on Reporting Low-Level Data
(Withdrawn 2002)
1.3 This test method is a simple, rapid, control procedure
D5788Guide for Spiking Organics into Aqueous Samples
suitableformonitoringtheeffectivenessofabiodegradationor
D5789Practice for Writing Quality Control Specifications
other linear alkyl benzene sulfonate (LAS) removal process.
for Standard Test Methods for Organic Constituents
For greater specificity and interference removal, the pretreat-
(Withdrawn 2002)
ment procedure in Annex A1 should be used. Data derived
D5847Practice for Writing Quality Control Specifications
without the pretreatment procedure should be interpreted with
for Standard Test Methods for Water Analysis
care. This test method is applicable in the range from 0.03 to
E60Practice for Analysis of Metals, Ores, and Related
1.5 mg/L for a 100-mL sample.
Materials by Spectrophotometry
1.4 The values stated in SI units are to be regarded as
E131Terminology Relating to Molecular Spectroscopy
standard. No other units of measurement are included in this
E275PracticeforDescribingandMeasuringPerformanceof
standard.
Ultraviolet and Visible Spectrophotometers
1.5 This standard does not purport to address all of the
3. Terminology
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro- 3.1 Definitions:
priate safety, health, and environmental practices and deter- 3.1.1 For definitions of terms used in this standard, refer to
mine the applicability of regulatory limitations prior to use. Terminologies D1129 and E131.
For a specific hazard statement, see 8.3.
3.2 Definitions of Terms Specific to This Standard:
1.6 This international standard was developed in accor-
3.2.1 alkyl benzene sulfonate (ABS), n—the generic name
dance with internationally recognized principles on standard-
applied to the neutralized product resulting from the sulfona-
ization established in the Decision on Principles for the
tion of a branched-chain alkylated benzene. See also Termi-
Development of International Standards, Guides and Recom-
nology D459.
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
This test method is under the jurisdiction of ASTM Committee D19 on Water the ASTM website.
andisthedirectresponsibilityofSubcommitteeD19.06onMethodsforAnalysisfor The last approved version of this historical standard is referenced on
Organic Substances in Water. www.astm.org.
Current edition approved Jan. 1, 2020. Published February 2020. Originally For a more complete discussion of terms relating to synthetic detergents and
approvedin1965.Lastpreviouseditionapprovedin2002asD2330–02whichwas theirsignificance,refertoMcKinney,R.E.,“SyndetsandWasteDisposal,” Sewage
withdrawn January 2011 and reinstated in January 2020. DOI: 10.1520/D2330-20. and Industrial Wastes, Vol 29, Part 6, June 1957, pp. 654–666.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D2330 − 20
3.2.2 linear alkyl benzene sulfonate (LAS), n—a form of 6.3 An evaluation of the effect of various potential interfer-
alkyl benzene sulfonate (ABS) in which the alkyl group is ences is summarized in Table 1. The listed compounds, in the
linear rather than a branched chain. See also Terminology concentrations indicated, were added to solutions containing 1
D459. mg/L LAS.
6.4 When interferences are present, the pretreatment proce-
4. Summary of Test Method
dure described in AnnexA1 should be used. Table 2 shows the
4.1 This test method is based upon the formation of a
interferences that can be present even though the pretreatment
blue-colored chloroform extractable ion pair by the reaction of
was used.
cationic methylene blue and an anionic surfactant (including
6.5 When a concentrated acid chromate cleaning solution is
LAS, other sulfonates, and sulfate esters).
used to clean glassware, including separatory funnels, between
4.2 Thesampleismixedwithanacidified,aqueoussolution
samples, care must be taken to completely flush all of the acid
of methylene blue. Any resulting hydrophobic ion pair which
chromate cleaning solution from all surfaces and, in particular,
may be formed is extracted successfully with chloroform. The
from the space between the barrel and plug of the separatory
combinedchloroformextractsarewashedwithanacidsolution
funnel stopcock. Failure to remove the acid can result in an
to remove the less hydrophobic ion pairs (having low partition
error in results.
coefficients) that can be formed by potentially interfering
6.5.1 Never use a detergent to clean any glassware used in
substances. The chloroform layer retains the highly hydropho-
this test method as a detergent is difficult to remove from
bic methylene blue-LAS ion pairs.
surfaces. Any residual detergent could cause a high result.
4.3 The intensity of the blue color remaining in the chloro-
form extract is measured photometrically at the wavelength of
7. Apparatus
maximum absorption near 650 nm. This intensity is related to
7.1 Filter Photometer or Spectrophotometer, suitable for
the concentration of LAS by means of a calibration curve or
measurement at a wavelength in the region near 650 nm and
chart.
equipped with 50-mm and 10-mm light path absorption cells.
5. Significance and Use
NOTE 1—Photometers and photometric practices prescribed in this test
5.1 The widespread use and discharge of detergents into
method shall conform to Practice E60. Spectrophotometers shall conform
surface waters can result in a lowering of its aesthetic quality to Practice E275.
by foam formation and by causing toxicity to aquatic wildlife.
7.2 Separatory Funnels, 250-mL size, Squibb-type, glass-
Thistestmethodiscapableofdetectingsmallconcentrationsof
stoppered, preferably with TFE-fluorocarbon stopcocks.
detergents as MBAS so that they can be controlled to prevent
such problems.
5.2 Biodegradable linear alkyl benzene sulfonates (LAS)
have replaced the branched-chain alkyl benzene sulfonates
TABLE 1 Evaluation of Potential Interferences in the Methylene
Blue Method
(ABS) in detergent formulations, which were more resistant to
biodegradation. Differentiation between linear and branched-
Added to 1.0 mg/L LAS
Concentration, mg/L Indicated LAS, mg/L
Solution
chain alkyl benzene sulfonates, as well as differentiation of the
Acetic acid 100 1.0
variouspositionalisomersofeithertype,isnotpossiblebythis
Ammonium 20 1.1
test method. While the methylene blue method may be em-
diethylphosphorodithioate
ployed to monitor studies designed to measure Benzene sulfonic acid 100 1.3
Cholesterol 100 1.0
biodegradability, it cannot be used to predict this quality.
2,4-dichlorophenol 100 1.0
Diethanolamine 1000 1.0
6. Interferences
Disodium phenylphosphate 10 1.0
Isopropylamine 14 1.0
6.1 Any organic or inorganic compound that will form a
Leucine 10 1.0
chloroformextractibleionpairwillinterferebyproducinghigh
N-1- 100 0.9
(naphthylethylenediamine)
results, unless the ion pair formed is eliminated by the
hydrochloride
treatmentdescribedin4.1.Thesepositiveinterferencesinclude
Nonyl phenol + 9 EtO 100 1.0
organic sulfonates, carboxylates, phosphates, and phenols, as
Phenol 100 1.0
Picric acid 5 4.6
well as inorganic cyanates, chlorides, nitrates, and thiocya-
Potassium chloride 100 1.0
nates.
Potassium cyanate 100 1.0
Potassium nitrate 100 1.0
6.2 Any compound effectively competing with methylene
Potassium thiocyanate 2 1.0
blue to form a LAS ion pair will give negative results. This
Potassium thiocyanate 100 4.1
negative interference is demonstrated by some amines and has Proteins (Knox gelatine) 100 0.9
Sodium dodecyl sulfate 10 14.6
analytical significance in the case of quaternary ammonium
Sodium dodecane 55.0
compounds.
sulfonate
Sodium naphthalene 55.1
sulfonate
Adopted from “Surfactants (Anionic) Methylene Blue Methods,” Standard Sodium stearate 100 1.0
Methods for the Examination of Water and Waste Water, Twelfth Ed., 1965.
D2330 − 20
TABLE 2 Evaluation of Potential Interferences in the Methylene
(NaH PO ·H O). Shake until solution is complete and then
2 4 2
Blue Method with Pretreatment Described in Annex A1
dilute to 1 L with water and mix.
Added to 1.0 mg/L LAS
Concentration, mg/L Indicated LAS, mg/L
8.7 Phenolphthalein Indicator Solution (5.0 g/L)—Dissolve
Solution
0.5 g of phenolphthalein in 50 mL of 95% ethyl alcohol and
Sodium dodecane 53.7
sulfonate
dilute to 100 mL with water and mix.
Sodium benzene sulfonate 100 1.2
Sodium dodecyl sulfate 10 0.9
NOTE 2—Specially denatured ethyl alcohol conforming to Formula No.
Potassium thiocyanate 100 1.0
3A or 30 of the U. S. Bureau of Alcohol, Tobacco, and Firearms may be
Picric acid 10 1.0
substituted for 95% ethyl alcohol.
8.8 Phosphate Wash Solution—Dissolve 50 g of sodium
dihydrogen phosphate monohydrate (NaH PO ·H O) in 500
2 4 2
8. Reagents and Materials
mLof water in a 1-Lvolumetric flask.Add carefully 50 mLof
8.1 Purity of Reagents—Reagent grade chemicals shall be
14% sulfuric acid stock solution (8.10) and dilute to volume
used in all tests. Unless otherwise indicated, it is intended that
with water and mix. The solution has a pH of approximately
all reagents shall conform to the specifications of the Commit-
1.8.
teeonAnalyticalReagentsoftheAmericanChemicalSociety.
8.9 Sodium Hydroxide Solution (10 g/L)—Dissolve 10 g of
Other grades may be used, provided it is first ascertained that
sodium hydroxide (NaOH) in water, dilute to 1 L and mix.
the reagent is of sufficiently high purity to permit its use
without lessening the accuracy of the determination. 8.10 Sulfuric Acid Stock Solution (14 % volume per
volume)—Add carefully 140 mL of concentrated sulfuric acid
8.2 Purity of Water—Unless otherwise indicated, references
(H SO , sp gr 1.84) to 700 mL of cold (0 to 5°C) water with
2 4
towatershallbeunderstoodtomeanreagentwaterconforming
good stirring, dilute to 1 L with water and mix.
to Specification D1193, Type II.
8.11 Sulfuric Acid Solution, Dilute (0.7% volume per
8.3 Chloroform (CHCl ). (Warning—Chloroform (CHCl )
3 3
volume)—Dilute carefully 50 mL of 14% sulfuric acid stock
is toxic and is suspected of being a possible carcinogen: avoid
solution (8.10) to 1 L with water and mix.
ingestion, inhalation, or absorption through the skin. Use a
well-ventilated fume hood to carry off chloroform vapors
9. Sampling
during analysis.)
9.1 Collect the sample in accordance with Practices D3370.
8.4 Linear Alkyl Benzene Sulfonate Solution, Stock(1.0
mL=1.0 mg LAS)—Weigh the amount of reference material
9.2 Samples may be preserved against biological oxidation
necessary to provide the equivalent of 1.000 g of LAS on a
by adding concentrated sulfuric acid (H SO ) to adjust the
2 4
100%activebasis.Dissolveinwateranddiluteto1L,mixing
sample to pH 2 or less and storing at 4°C. Analyze the
gentlytopreventfoamformation.Recordthemolecularweight
preserved sample as soon as possible, or within one week after
of the LAS reference material as supplied. The stock solution
collection. Data on decomposition are not available.
may be stored at 4°C in the dark for 12 months in a
9.3 Rinse the sample container and cap well to free them of
well-stoppered flask without deterioration.
detergent if they have been used previously and cleaned prior
8.5 Linear Alkyl Benzene Sulfonate Standard Solution(1.0
to recycling.
mL=0.01 mg LAS)—Dilute 10.0 mL of the foam-free stock
solution (8.4) to 1 L with water that has been previously
10. Preparation of Apparatus
adjusted to pH 2 with sulfuric acid and mix. The standard
10.1 Glassware Conditioning:
solutionmaybestoredat4°Cinthedarkforatleast12months
in a well-stoppered flask without deterioration. 10.1.1 All glassware used for the determination of LAS
should be free of scratches and etch marks because of the
8.6 Methylene Blue Solution (30 mg/L)—Dissolve 0.1 g of
tendency of surface-active materials to adsorb on this type of
methylenebluechloridein100mLofwater.Transfer30mLof
surface. All volumetric flasks and photometer cells, projected
thissolutiontoa1-Lvolumetricflaskandadd500mLofwater.
for use in LAS determinations, should, as instructed herein, be
Add carefully 50 mL of 14% sulfuric acid stock solution
preconditioned as follows: Obtain the chloroform extract from
(8.10) and 50 g of sodium dihydrogen phosphate monohydrate
12.0 mL of the standard LAS solution as described in 11.4.
Transfer sequentially to each of the volumetric flasks and
ACS Reagent Chemicals, Specifications and Procedures for Reagents and
photometer cells and permit a minimum contact time, in each
Standard-Grade Reference Materials, American Chemical Society, Washington,
case, of 5 min. Rinse thoroughly with chloroform and drain
DC. For suggestions on the testing of reagents not listed by theAmerican Chemical
(Warning—See 8.3).
Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset,
U.K., and the United States Pharmacopeia and National Formulary, U.S. Pharma-
copeial Convention, Inc. (USPC), Rockville, MD.
11. Calibration
Linear alkyl benzene sulfonate reference material may be obtained from the
United States Environmental Protection Agency, Environmental Monitoring and
11.1 Prepare a series of standards by adding the standard
Support Laboratory, Cincinnati, OH 45268.
solution (8.5) from a 25-mL buret to a series of 250-mL
Supporting data have been filed atASTM International Headquarters and may
separatoryfunnels(see6.5)anddilutethestandardsto100mL
beobtainedbyrequestingResearchReportRR:D19-0169.ContactASTMCustomer
Service at [e-mail]. volume with water, yielding solutions as follows:
D2330 − 20
NOTE 7—Aseparate calibration curve must be made for each photom-
Standard, mL (1.0 mL = LAS, mg (per 100 mL
eter and each cell used. Each calibration curve must be checked periodi-
0.01 mg LAS) of extract)
cally to ensure repeatability. If a subsequent calibration curve does not
0.00 0.00
reproduce the previous curve, then recheck the curve again. Make sure
1.00 0.01
thattheLASreferencematerialassuppliedhasthesamemolecularweight
3.00 0.03
as that which was used to produce the previous curve.
5.00 0.05
7.00 0.07
12. Procedure
9.00 0.09
12.00 0.12
12.1 Select a volume of sample consistent with the antici-
NOTE 3—If desired, additional standards in the range from 0.00 to 0.12 patedLAScontent.IftheLASconcentrationisnotexpectedto
mg of LAS may be prepared for the calibration series.
exceed1mg/L,usea100-mLsample.ForLASinthe10mg/L
range, use a 10-mL sample diluted to 100 mL with water. The
11.2 Add 3 drops of phenolphthalein solution (8.7) and just
enough sodium hydroxide solution (8.9) to produce a pink sensitivity of the method may be improved in the cases of
relatively unpolluted waters by concentrating larger sample
color. Add dilute sulfuric acid solution (8.11), in small incre-
ments until the pink color is barely discharged. volumes to 100 mL by evaporation.
12.2 Process the sample or a set of samples, a quality
11.3 Add 25 mL of methylene blue solution (8.6) and mix.
Add 25 mL of chloroform (Warning—See 8.3) and mix control standard (see Annex A2), selected from near the
midscale of the series used to prepare the calibration chart in
thoroughly for 30 s with shaking. Vent carefully, permit the
phases to separate and then drain the chloroform layer into a 11.1,andaparallelprocedureblank,using100mLofwater,in
250-mL separatory funnels as outlined in 11.2 to 11.6.
second 250-mL separatory funnel (see 6.5). Leave any emul-
sion layer in the first separatory funnel. Repeat the extraction,
NOTE 8—If an excessive amount of emulsion forms with a sample in
serially, with two additional 25-mL portions of chloroform.
11.3 and it is evident that a substantial loss of MBAS will occur, then the
analystisadvisedtousewell-knowntechniquesinanattempttobreakthe
NOTE 4—Vent the separatory funnel through the stopcock with the
emulsion. Several known techniques are (1) the brief local application of
funnel tip directed away from the face to avoid contact with any sample
heat by a hot-water stream applied to the outside of the separatory funnel
spray (Warning—See 8.3).
in the area of the emulsion layer and (2) filtering the emulsion through a
wadofglasswooltoremoveparticulatematter,etc.Iftheemulsioncannot
11.4 Add 50 mL of phosphate wash solution (8.8)tothe
be broken, then make a note recording the fact,
...