ASTM D1783-01(2020)

Standard Test Methods for Phenolic Compounds in Water

SIGNIFICANCE AND USE
5.1 Phenolic compounds are sometimes found in surface waters from natural and industrial sources. Their presence in streams and other waterways frequently will cause off flavor in fish tissue and other aquatic food.  
5.2 Chlorination of waters containing phenols may produce chlorophenols that are odoriferous and objectionable tasting.
SCOPE
1.1 These test methods cover the preparation of the sample and the determination of the concentration of phenolic compounds in water. They are based on the color reaction of phenol (C6H5OH) with 4-aminoantipyrine and any color produced by the reaction of other phenolic compounds is reported as phenol. The concentration of phenol measured represents the minimum concentration of phenolic compounds present in the sample.  
1.2 Phenolic compounds with a substituent in the para position may not quantitatively produce color with 4-aminoantipyrine. However, para substituents of phenol such as carboxyl, halogen, hydroxyl, methoxyl, or sulfonic acid groups do produce color with 4-aminoantipyrine.  
1.3 These test methods address specific applications as follows:    
Range  
Sections  
Test Method A—Chloroform Extraction  
0 to 100 μg/L  
11 to 17  
Test Method B—Direct Photometric  
>0.1 mg/L
(100 μg/L)  
18 to 24  
1.4 It is the users’ responsibility to assure the validity of the standard test method for use in their particular matrix of interest.  
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.6 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 specific hazard statements see 6.3.2 and 8.6.  
1.7 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 D1783-01(2012)e1 - Standard Test Methods for Phenolic Compounds in Water
• Effective Date: 01-Jan-2020
• Refers: ASTM D1129-13(2020)e2 - Standard Terminology Relating to Water
• Effective Date: 01-May-2020
• Refers: ASTM D2777-12 - Standard Practice for Determination of Precision and Bias of Applicable Test Methods of Committee D19 on Water
• Effective Date: 15-Jun-2012
• Refers: ASTM D1293-12 - Standard Test Methods for pH of Water
• Effective Date: 01-Jan-2012
• Refers: ASTM D5810-96(2011) - Standard Guide for Spiking 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 D3370-08 - Standard Practices for Sampling Water from Closed Conduits
• Effective Date: 01-Oct-2008
• Refers: ASTM D2777-08 - Standard Practice for Determination of Precision and Bias of Applicable Test Methods of Committee D19 on Water
• Effective Date: 15-Jan-2008
• Refers: ASTM D3370-07 - Standard Practices for Sampling Water from Closed Conduits
• Effective Date: 01-Dec-2007
• Refers: ASTM D1129-06ae1 - Standard Terminology Relating to Water
• Effective Date: 01-Sep-2006
• Refers: ASTM D1129-06a - Standard Terminology Relating to Water
• Effective Date: 01-Sep-2006
• Refers: ASTM D2777-06 - Standard Practice for Determination of Precision and Bias of Applicable Test Methods of Committee D19 on Water
• Effective Date: 15-Aug-2006
• Refers: ASTM D5810-96(2006) - Standard Guide for Spiking into Aqueous Samples
• Effective Date: 15-Aug-2006
• Refers: ASTM D1193-06 - Standard Specification for Reagent Water
• Effective Date: 01-Mar-2006

Overview

ASTM D1783-01(2020): Standard Test Methods for Phenolic Compounds in Water establishes procedures for detecting and measuring phenolic compounds in water. Developed by ASTM International, this standard is important for environmental monitoring, water quality control, and ensuring the safety of water for both human and aquatic life. Phenolic compounds can originate from both natural and industrial sources and are of concern due to their potential to affect water flavor and aquatic food, particularly when undergoing chlorination. This document outlines two validated colorimetric test methods based on the reaction of phenol with 4-aminoantipyrine: the Chloroform Extraction (Method A) and the Direct Photometric Method (Method B).

Key Topics

• Scope and Measurement Range: ASTM D1783-01(2020) provides detailed procedures for both low and higher concentrations:

  • Test Method A – Chloroform Extraction: Designed for quantifying phenolic compounds in the range of 0 to 100 µg/L.
  • Test Method B – Direct Photometric: Suited for concentrations greater than 0.1 mg/L (100 µg/L).

• Significance and Use:

  • Detects phenolic compounds which can impart off-flavors to fish and other aquatic food.
  • Highlights the risks associated with chlorination of waters containing phenols, which can create unpleasant, odoriferous chlorophenols.
  • Suitable for monitoring surface waters, wastewater treatment plant effluent, and industrial process streams.

• Sample Preparation and Analysis:

  • Involves colorimetric detection using the reaction with 4-aminoantipyrine in the presence of potassium ferricyanide.
  • Both methods require initial distillation to isolate phenolic compounds from the matrix.
  • Step-by-step instructions address the removal of interfering substances (e.g., oxidizing/sulfur compounds, oils, tars) to ensure accurate results.

• Quality Control:

  • The standard emphasizes verifying precision and bias through calibration, control samples, spike recoveries, and duplicate analyses.
  • Guidance is provided for sample preservation and storage to minimize changes in phenolic content prior to analysis.

Applications

Adherence to ASTM D1783-01(2020) supports regulatory and compliance testing in environmental laboratories, water utilities, and industrial settings. Common applications include:

• Environmental Monitoring: Tracking phenolic contamination in rivers, lakes, and reservoirs to protect aquatic ecosystems and public health.
• Wastewater Treatment: Monitoring influent and effluent to ensure treatment processes effectively reduce phenolic compound levels before discharge.
• Drinking Water Safety: Evaluating source and treated water to prevent taste and odor issues related to phenol and chlorophenol formation.
• Industrial Discharge Compliance: Assessing process streams to meet environmental standards for phenolic release.

By providing reliable measurement methods, ASTM D1783-01(2020) helps organizations maintain water quality, fulfill reporting obligations, and safeguard natural resources.

Related Standards

• ASTM D1129: Terminology Relating to Water
• ASTM D1193: Specification for Reagent Water
• ASTM D1293: Test Methods for pH of Water
• ASTM D2777: Practice for Determination of Precision and Bias of Applicable Test Methods of Committee D19 on Water
• ASTM D3370: Practices for Sampling Water from Flowing Process Streams
• ASTM D5810: Guide for Spiking into Aqueous Samples
• ASTM D5847: Practice for Writing Quality Control Specifications for Water Analysis

These related standards offer complementary guidance on terminology, sampling, and quality assurance procedures that support the effective implementation of ASTM D1783-01(2020) for phenolic compounds in water.

Keywords: phenolic compounds in water, ASTM D1783, water quality testing, 4-aminoantipyrine method, chlorophenols, environmental monitoring, water analysis, drinking water standards, wastewater compliance, water sampling.

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: D1783 − 01 (Reapproved 2020)
Standard Test Methods for
Phenolic Compounds in Water
This standard is issued under the fixed designation D1783; 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
1.1 These test methods cover the preparation of the sample
Barriers to Trade (TBT) Committee.
and the determination of the concentration of phenolic com-
poundsinwater.Theyarebasedonthecolorreactionofphenol
2. Referenced Documents
(C H OH) with 4-aminoantipyrine and any color produced by
6 5
thereactionofotherphenoliccompoundsisreportedasphenol.
2.1 ASTM Standards:
Theconcentrationofphenolmeasuredrepresentstheminimum
D1129 Terminology Relating to Water
concentration of phenolic compounds present in the sample.
D1192 Guide for Equipment for Sampling Water and Steam
in Closed Conduits (Withdrawn 2003)
1.2 Phenolic compounds with a substituent in the para
D1193 Specification for Reagent Water
position may not quantitatively produce color with
D1293 Test Methods for pH of Water
4-aminoantipyrine. However, para substituents of phenol such
D2777 Practice for Determination of Precision and Bias of
as carboxyl, halogen, hydroxyl, methoxyl, or sulfonic acid
Applicable Test Methods of Committee D19 on Water
groups do produce color with 4-aminoantipyrine.
D3370 Practices for Sampling Water from Flowing Process
1.3 These test methods address specific applications as
Streams
follows:
D5789 Practice for Writing Quality Control Specifications
Range Sections
for Standard Test Methods for Organic Constituents
(Withdrawn 2002)
Test Method A—Chloroform Extraction 0 to 100 µg/L 11 to 17
D5810 Guide for Spiking into Aqueous Samples
Test Method B—Direct Photometric >0.1 mg/L 18 to 24
(100 µg/L)
D5847 Practice for Writing Quality Control Specifications
1.4 It is the users’responsibility to assure the validity of the for Standard Test Methods for Water Analysis
standard test method for use in their particular matrix of
interest.
3. Terminology
1.5 The values stated in SI units are to be regarded as
3.1 Definitions:
standard. No other units of measurement are included in this
3.1.1 For definitions of terms used in this standard, refer to
standard.
Terminology D1129.
1.6 This standard does not purport to address all of the
3.2 Definitions of Terms Specific to This Standard:
safety concerns, if any, associated with its use. It is the
3.2.1 phenolic compounds, n—hydroxy derivatives of ben-
responsibility of the user of this standard to establish appro-
zene and its condensed nuclei.
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
4. Summary of Test Methods
For specific hazard statements see 6.3.2 and 8.6.
4.1 Test Method A and Test Method B are photometric
1.7 This international standard was developed in accor-
procedures based on the reaction of steam-distillable phenolic
dance with internationally recognized principles on standard-
compounds with 4-aminoantipyrine.
ization established in the Decision on Principles for the
1 2
ThesetestmethodsareunderthejurisdictionofD19onWaterandarethedirect For referenced ASTM standards, visit the ASTM website, www.astm.org, or
responsibility of Subcommittee D19.06 on Methods for Analysis for Organic contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Substances in Water. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Jan. 1, 2020. Published January 2020. Originally the ASTM website.
ɛ1 3
approved in 1960. Last previous edition approved in 2012 as D1783 – 01R12 . The last approved version of this historical standard is referenced on
DOI: 10.1520/D1783-01R20. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D1783 − 01 (2020)
4.2 Test Method A differs from Test Method B mainly in sulfide (CuS) precipitate is formed. Excessive amounts of H S
thatthesampleisextractedwithchloroform,therebyproviding or SO may be removed from the acidified sample by a brief
20-fold greater sensitivity. aeration treatment or stirring before the addition of the CuSO
solution or both. (Warning—Acidification of certain samples
4.3 Both procedures involve first separating the phenolic
mayproducevigorousevolutionofcarbondioxide(CO ),SO ,
2 2
compounds from the background matrix by distillation. Due to
H S, or other gases. Therefore, perform the acidification
the differing solubilities and boiling points of the various
cautiously and stir the samples during the process. Complete
phenolic compounds, each phenolic comes over in the distil-
the evolution of gases before the sample is stoppered.)
lation at a different rate. Some phenolics will be substantially
6.3.3 Oils and Tars—If the sample contains oil or tar, some
transferred near the beginning of the distillation and some will
phenolic compounds may be dissolved in these materials. An
not start to distill until near the end. For this reason, some
alkaline extraction, in the absence of CuSO , may be used to
phenolics may not have been quantitatively transferred to the
eliminate the tar and oil.Adjust the pH of the sample between
receivingflaskwhenthespecifiedvolumeofdistillatehasbeen
12 and 12.5 with sodium hydroxide (NaOH) pellets to avoid
collected.
extraction of the phenols. Extract the mixture with carbon
tetrachloride (CCl ). Discard the oil- or tar-containing layer.
5. Significance and Use
Remove any CCl remaining in the aqueous portion of the
5.1 Phenolic compounds are sometimes found in surface
sample by gentle heating.
waters from natural and industrial sources. Their presence in
NOTE 1—The presence of CuSO is detrimental since it is converted to
streams and other waterways frequently will cause off flavor in 4
cupric hydroxide (Cu(OH) ) by the NaOH. The Cu(OH) acts as an
2 2
fish tissue and other aquatic food.
oxidizing agent on phenols.
5.2 Chlorination of waters containing phenols may produce
chlorophenols that are odoriferous and objectionable tasting.
7. Apparatus
7.1 Buchner-Type Funnel with Coarse Fritted Disk—At
6. Interferences
least three funnels are needed for determination of phenolic
6.1 Common interferences that may occur in waters are
compounds by Test Method A. Alternatively, standard glass
phenol-decomposing bacteria, reducing substances, and
funnels and pre-fluted filter paper may be used. The funnel
strongly alkaline conditions of the sample. Provisions incorpo-
paper must be large enough to hold5gof sodium sulfate.
rated in these test methods will minimize the effects of such
These funnels are not used in Test Method B.
interferences.
7.2 Photometer—A spectrophotometer or filter photometer,
6.2 Treatment procedures required prior to the analysis for
suitable for use at 460 nm (Test MethodA) or at 510 nm (Test
removal of interfering compounds may result in the unavoid-
Method B), and accommodating a cell that gives a light path of
able elimination or loss of certain types of phenolic com-
1.0to10cmshallbeused.Thesizeofthecellusedwilldepend
pounds.Itisbeyondthescopeofthesetestmethodstodescribe
on the absorbance of the colored solutions being measured and
proceduresforovercomingallofthepossibleinterferencesthat
the characteristics of the photometer. In general, if the absor-
may be encountered in the test methods, particularly with
bances are greater than 1.0 with a larger cell, the next smaller
highly contaminated water and industrial waste water. The
size cell should be used.
procedures used must be revised to meet the specific require-
7.3 Distillation Apparatus—A 1-L, heat-resistant, distilling
ments.
flaskattachedtoaGrahamcondenserbymeansofaglassjoint.
6.3 A few methods for eliminating certain interferences are
7.4 pH Meter—This apparatus shall conform to the require-
suggested. (See Section 8 for descriptions of reagents re-
ments in Test Methods D1293.
quired.)
6.3.1 Oxidizing Agents—If the sample smells of chlorine, or
8. Reagents
if iodine is liberated from potassium iodide on acidification of
8.1 Purity of Reagents—Reagent grade chemicals shall be
the sample, remove the oxidizing agents so indicated immedi-
used in all tests. Unless otherwise indicated, it is intended that
ately after sampling. The presence of oxidizing agents in the
all reagents shall conform to the specifications of the Commit-
sample may oxidize some or all of the phenols in a short time.
tee onAnalytical Reagents of theAmerican Chemical Society,
Ferrous sulfate or sodium arsenite solution may be added to
where such specifications are available. Other grades may be
destroy all of the oxidizing substances. Excess ferrous sulfate
used, provided it is first ascertained that the reagent is of
or sodium arsenite do not interfere since they are removed in
sufficiently high purity to permit its use without lessening the
the distillation procedure.
accuracy of the determination.
6.3.2 Sulfur Compounds—Compounds that liberate hydro-
gen sulfide (H S) or sulfur dioxide (SO ) on acidification may
2 2
interfere with the phenol determination. Treatment of the
acidified sample with copper sulfate usually eliminates such
ACS Reagent Chemicals, Specifications and Procedures for Reagents and
Standard-Grade Reference Materials, American Chemical Society, Washington,
interferences.Acidify the sample with sulfuric acid (H SO )or
2 4
DC. For suggestions on the testing of reagents not listed by theAmerican Chemical
hydrochloric acid (HCl) until just acid to methyl orange. Then
Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset,
add a sufficient quantity of copper sulfate (CuSO ) solution to
4 U.K., and the United States Pharmacopeia and National Formulary, U.S. Pharma-
give a light blue color to the sample or until no more copper copeial Convention, Inc. (USPC), Rockville, MD.
D1783 − 01 (2020)
8.2 Purity of Water—Unless otherwise indicated, references longer sampling periods are necessary, collect a series of
to water shall be understood to mean water conforming to composite samples. Then preserve such composite samples in
Specification D1193Types I, II, III, or IV.Water used for these accordance with Section 10 until analyzed.
test methods shall be free of phenolic compounds, residual
10. Preservation of Samples
chlorine, and substances that interfere with the test. Water
sufficiently free of phenolics can be generated by boiling the
10.1 Phenolic compounds in water are subject to both
water for 20 min.
chemical and biochemical oxidation. Preserve samples within
4 h of collection.Acidify the samples to a pH between 0.5 and
8.3 Aminoantipyrine Solution (20 g/L)—Dissolve 2.0 g of
2.0 with H PO , HCl, H SO , or NaHSO .
3 4 2 4 4
4-aminoantipyrine in water and dilute to 100 mL. Prepare this
reagent fresh as used. 10.2 To further minimize any changes in the phenolic
contentofthesample,keepitcold,preferablybetween2°Cand
NOTE2—Themeltingpointofasatisfactorygradeof4-aminoantipyrine
4°C until analysis. The preserved samples should be in glass,
ranges from 108.0 to 109.5°C.
notplasticbottles,andpreferablyanalyzedwithin28daysafter
8.4 Ammonium Chloride Solution (20 g/L)—Dissolve 20 g
collection.
of ammonium chloride (NH Cl) in water and dilute to 1 L.
TEST METHOD A—CHLOROFORM EXTRACTION
8.5 Ammonium Hydroxide (NH OH) (sp gr 0.90)—
Concentrated ammonium hydroxide (NH OH).
11. Scope
8.6 Carbon Tetrachloride (CCl ). Warning—Phenol, car-
11.1 This test method is generally applicable to water that
bon tetrachloride, and chloroform are potentially hazardous to
containslessthan100µg/L(0.1mg/L)ofphenoliccompounds.
human health. Avoid inhalation and direct contact. Use in a
Lower levels may be achieved with different instruments and
well-ventilated hood.
larger cells. Higher levels can be achieved by dilution.
8.7 Chloroform (CHCl ).
11.2 The lowest levels of analyte detection or accurate
8.8 Hydrochloric Acid (HCl) (sp gr 1.19)—Concentrated
quantitation are laboratory and sample matrix dependent and it
hydrochloric acid (HCl).
is up to the users of the test method to determine these levels
in their own situation.
8.9 Phenol Solution, Stock (1 mL = 1.0 mg phenol)—
Dissolve 1.00 g of phenol (C H OH) in freshly boiled and
6 5
11.3 This test method was tested on municipal wastewater
cooled water. Dilute to 1 000 mL with freshly boiled cooled
treatment plant influent and effluent, lake water, river water,
water. Prepare a fresh stock solution within 30 days of use.
and industrial treatment plant effluent. It is the user’s respon-
sibility to insure the validity of this test method for waters of
8.10 Phenol Solution, Intermediate (C H OH) (1 mL = 10
6 5
untested matrices.
µg phenol)—Dilute 10.0 mLof the stock solution to 1 000 mL
with freshly boiled and cooled water. Prepare this solution
12. Summary of Test Method
fresh on the day it is used.
12.1 This is a photometric test method, based on the
8.11 Phenol Solution, Standard (C H OH) (1 mL = 1.0 µg
6 5
reaction of steam-distillable phenolic compounds with
phenol)—Dilute 50 mLof the intermediate solution to 500 mL
4-aminoantipyrine at a pH of 10.0 6 0.2 in the presence of
with freshly boiled and cooled water. Prepare this solution
K Fe(CN) . The antipyrine dye formed is extracted from the
3 6
fresh within2hof use.
aqueous solution with chloroform and the absorbance is
8.12 Potassium Ferricyanide Solution(K Fe(CN) ) (80
3 6
measured at 460 nm. The concentration of phenolic com-
g/L)—Dissolve8.0gof(K Fe(CN) )inwateranddiluteto100
3 6
pounds in the sample is expressed in terms of micrograms per
mL. Filter if necessary. Prepare fresh weekly.
litre of phenol C H OH.
6 5
8.13 Sodium Bisulfate (NaHSO ).
13. Calibration
8.14 Sodium Sulfate (Na SO ), anhydrous and granular.
2 4
13.1 Prepare a series of 500-mL C H OH standards in
6 5
8.15 Sulfuric Acid (H SO ) (sp gr 1.84)—Concentrated
2 4
freshly boiled and cooled water containing 0, 5, 10, 20, 30, 40,
sulfuric acid (H SO ).
2 4
and 50 mL of standard C H OH solution (1 mL = 1.0 µg
6 5
C H OH). Use all solutions at room temperature.
8.16 Sulfuric Acid Solution (H SO ) (1+9)—Cautiously add
2 4 6 5
one volume of concentrated H SO to nine volumes of water
2 4
13.2 Developcolorintheseriesofstandardsandpreparethe
with continuous cooling and mixing. Solution will become hot.
chloroform extracts in accordance with the procedures pre-
scribed in Section 14 and 15.
9. Sampling
13.3 Measure the absorbance of each standard at 460 nm
9.1 Collect the sample in accordance with Guide D1192 and
against the reagent method blank (blank) as zero absorbance.
Practices D3370.
Plot the absorbances against the corresponding weights in
micrograms of phenol.
9.2 When samples are composited, chill the samples or the
composite sample immediately and keep at a temperature of
NOTE 3—Make a separate calibration curve for each spectrophotometer
not more than 4°C during the compositing period. The collec-
or photoelectric colorimeter. Check each curve periodically to ensure
tion time for a single composite sample shall not exceed 4 h. If reproducibility.
D1783 − 01 (2020)
TABLE 1 Precision Data—Test Method A
Reagent Water Matrix Optional Water Matrix
Level
6.460 µg/L 34.780 µg/L 67.900 µg/L 5.430 µg/L 32.840 µg/L 66.260 µg/L
n 23 23 2324 2423
S 3.384 4.190 8.923 2.494 3.957 8.147
T
S 2.718 5.320 7.300 2.528 3.243 5.850
o
A
So:C.V. 38 % 10.8 % 11.8 % 46.6 % 9.9 % 8.8 %
A
Coefficient of variation (S level) by 100.
o
14. Distillation Procedure 15.5 Using the chloroform extract of the reagent blank
adjust the colorimeter to zero absorbance at 460 nm. Measure
14.1 Measure 500 mL of the sample into a beaker. Adjust
the absorbance of the sample extract at the same wavelength.
the pH of the sample to between pH 0.5 and 4 with H SO
2 4
By reference to the calibration curve (Section 13) and the
solution (1+9). Use methyl orange indicator solution or a pH
absorbance obtained on the sample extract, determine the
meter to aid in the pH adjustment. If the sample has been
phenolic content of the sample.
previously preserved according to 10.1, this pH adjustment
step may be omitted. Transfer the mixture to the distillation
16. Calculation
apparatus. Use a 500-mL graduated cylinder as a receiver.
16.1 Calculate the phenolic content of the sample, in mi-
14.2 Distill 450 mLof the sample. Stop the distillation and,
crograms per litre, as follows:
when boiling ceases, add 50 mL of water to the distillation
Concentration of phenolics in original sample µg/L 5 W 3100/V
flask. Continue the distillation until a total of 500 mLhas been
collected.
where:
14.3 If the distillate is turbid, a second distillation may
W = phenolics, in aliquot of sample distillate diluted to 500
prove helpful.Acidify the turbid distillate with H SO solution
mL as determined from calibration curve, µg, and
2 4
(1+9) and repeat the previously described distillation. The V = sample distillate, in the 500-mL solution reacted with
second distillation usually eliminates the turbidity. However, if 4-aminoantipyrine, mL.
NOTE 5—Since the ratio of the various phenolic compounds present in
the second distillate is also turbid, the screening procedure
a given sample is unpredictable, phenol (C H OH) is used as a standard.
6 5
must be modified. Attempt an extraction process before the
Any color produced by the reaction of other phenolic compounds is
distillation to avoid turbidity in the distillate.
reported as phenol. This value will represent the min
...