ASTM D4841-88(2008)
(Practice)Standard Practice for Estimation of Holding Time for Water Samples Containing Organic and Inorganic Constituents
Standard Practice for Estimation of Holding Time for Water Samples Containing Organic and Inorganic Constituents
SIGNIFICANCE AND USE
In order to obtain meaningful analytical data, sample preservation techniques must be effective from the time of sample collection to the time of analysis. A laboratory must confirm that sample integrity is maintained throughout maximum time periods between sample collection and analysis. In many cases, it is useful to know the maximum holding time. An evaluation of holding time is useful also in judging the efficacy of various preservation techniques.
SCOPE
1.1 This practice covers the means of estimating the period of time during which a water sample can be stored after collection and preservation without significantly affecting the accuracy of analysis.
1.2 The maximum holding time is dependent upon the matrix used and the specific analyte of interest. Therefore, water samples from a specific source must be tested to determine the period of time that sample integrity is maintained by standard preservation practices.
1.3 In the event that it is not possible to analyze the sample immediately at the time of collection, this practice does not provide information regarding degradation of the constituent of interest or changes in the matrix that may occur from the time of sample collection to the time of the initial analysis.
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 and health practices and determine the applicability of regulatory limitations prior to use.
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: D4841 − 88 (Reapproved 2008)
StandardPractice for
Estimation of Holding Time for Water Samples Containing
Organic and Inorganic Constituents
This standard is issued under the fixed designation D4841; 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 D2777 Practice for Determination of Precision and Bias of
Applicable Test Methods of Committee D19 on Water
1.1 This practice covers the means of estimating the period
D3694 Practices for Preparation of Sample Containers and
of time during which a water sample can be stored after
for Preservation of Organic Constituents
collection and preservation without significantly affecting the
D4210 Practice for Intralaboratory Quality Control Proce-
accuracy of analysis.
dures and a Discussion on Reporting Low-Level Data
1.2 The maximum holding time is dependent upon the 3
(Withdrawn 2002)
matrix used and the specific analyte of interest. Therefore,
D4375 Practice for Basic Statistics in Committee D19 on
water samples from a specific source must be tested to
Water
determinetheperiodoftimethatsampleintegrityismaintained
E178 Practice for Dealing With Outlying Observations
by standard preservation practices.
3. Terminology
1.3 In the event that it is not possible to analyze the sample
immediately at the time of collection, this practice does not
3.1 Definitions:
provideinformationregardingdegradationoftheconstituentof
3.1.1 For definitions of terms used in this practice, refer to
interest or changes in the matrix that may occur from the time
Terminology D1129.
of sample collection to the time of the initial analysis.
3.1.2 criterion of detection—the minimum quantity that
must be observed before it can be stated that a substance has
1.4 The values stated in SI units are to be regarded as
been discerned with an acceptable probability that the state-
standard. No other units of measurement are included in this
ment is true (see Practice D4210).
standard.
3.2 Definitions of Terms Specific to This Standard:
1.5 This standard does not purport to address all of the
3.2.1 maximum holding time—the maximum period of time
safety concerns, if any, associated with its use. It is the
during which a properly preserved sample can be stored before
responsibility of the user of this standard to establish appro-
such degradation of the constituent of interest or change in
priate safety and health practices and determine the applica-
sample matrix occurs that the systematic error exceeds the
bility of regulatory limitations prior to use.
99 % confidence interval (not to exceed 15 %) of the test
2. Referenced Documents
calculated around the mean concentration found at zero time.
2.1 ASTM Standards: 3.2.2 acceptable holding time—any period of time less than
D1129 Terminology Relating to Water or equal to the maximum holding time.
D1192 Guide for Equipment for Sampling Water and Steam
4. Summary of Practice
in Closed Conduits (Withdrawn 2003)
D1193 Specification for Reagent Water
4.1 Holding time is estimated by means of replicate analy-
ses at discrete time intervals using a large volume of a water
sample that has been properly collected and preserved. A
This practice is under the jurisdiction of ASTM Committee D19 on Water and
sufficient number of replicate analyses are performed to main-
is the direct responsibility of Subcommittee D19.02 on Quality Systems,
Specification, and Statistics.
tain the 99 % confidence interval within 15 % of the concen-
Current edition approved July 15, 2008. Published August 2008. Originally
tration found at zero time. Concentration of the constituent of
approved in 1988. Last previous edition approved in 2003 as D4841 – 88 (2003).
interest is plotted versus time. The maximum holding time is
DOI: 10.1520/D4841-88R08.
the period of time from sample collection to such time that
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
degradation of the constituent of interest or change in sample
Standards volume information, refer to the standard’s Document Summary page on
matrix occurs and the systematic error exceeds the 99 %
the ASTM website.
confidence interval (not to exceed 15 %) of the test calculated
The last approved version of this historical standard is referenced on
www.astm.org. around the mean concentration at zero time. Prior to the
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D4841 − 88 (Reapproved 2008)
determination of holding time, each laboratory must generate where:
itsownprecisiondatainmatrixwater.Thesedataarecompared
V = estimated volume of sample required, mL,
to the pooled single-operator precision data on reagent water
A = volume of sample required to perform each separate
reported in the test method and, the less precise of the two sets
analysis, mL,
of data are used in the calculation.
B = estimated number of replicate determinations required
at each interval in the holding time study (see Table 1),
NOTE 1—This practice generates only limited data which may not lead
to consistent conclusions each time that the test is applied. In cases where
C = estimated number of time intervals required for the
the concentration of the constituent of interest changes gradually over an
extended period of time, the inherent variability in test results may lead to
holding time study (excluding the initial time zero
somewhat different conclusions each time that this practice is applied.
precision study), and
D = number of replicate determinations performed in initial
5. Significance and Use
precision study (usually 10).
5.1 In order to obtain meaningful analytical data, sample
7.1.2 Based on the volume calculated in 7.1.1, collect a
preservation techniques must be effective from the time of
sufficient volume of the specific matrix to be tested to perform
sample collection to the time of analysis. A laboratory must
a precision study and the holding time study. Collect the
confirm that sample integrity is maintained throughout maxi-
sample in a properly prepared sample container or series of
mum time periods between sample collection and analysis. In
containers.Refertotheprocedurefortheconstituentofinterest
manycases,itisusefultoknowthemaximumholdingtime.An
for specific instructions on sample collection procedures.
evaluation of holding time is useful also in judging the efficacy
NOTE 3—The total volume of sample calculated in 7.1.1 is only an
of various preservation techniques.
estimate.Dependinguponthedegreeofcertaintywithwhichtheprecision
can be estimated, it is recommended that a volume somewhat in excess of
6. Reagents
that calculated in 7.1.1 be collected in order to make certain that sufficient
6.1 Purity of Reagents—Reagent grade chemicals shall be
sample will be available to complete the holding time study. The analyst
may want to consider performing a preliminary precision study prior to
used in all tests. Unless otherwise indicated, it is intended that
sample collection in order to be certain that the estimate of precision used
all reagents shall conform to the specifications of the Commit-
in 7.1.1 is reasonably accurate.
tee onAnalytical Reagents of theAmerican Chemical Society,
7.1.3 Add the appropriate preservation reagents to the
where such specifications are available. Other grades may be
sample immediately after collection. Immediately proceed to
used provided it is first ascertained that the reagent is of
7.2 or 7.3 depending upon whether inorganic or organic
sufficiently high purity to permit its use without lowering the
compounds are being determined.
accuracy of the determination.
6.1.1 Refer to the specific test method and to Practices
7.2 Determination of Single Operator Precision—Inorganic
D3694 for information regarding necessary equipment and
Methods:
preparation of reagents.
7.2.1 Immediately after sample collection, analyze an ap-
propriate number (usually 10) of measured volumes of sample
6.2 Purity of Water— Reference to water shall be under-
as described in the appropriate procedure. If a measurable
stood to mean reagent water conforming to Specification
concentration of the constituent of interest is found, proceed to
D1193, Type II, and demonstrated to be free of specific
7.2.4.Iftheconcentrationoftheconstituentofinterestisbelow
interference for the test being performed.
the criterion of detection at a P level of ≤ 0.05, fortify the
7. Determination of Holding Time sample as described in 7.2.2 and reanalyze or collect another
sample.
7.1 Collection of Sample:
NOTE 4—If the concentration of the constituent of interest is very low
NOTE 2—In some instances, it may be of interest to determine the
suchthatitapproachesthecriterionofdetectionata Plevelof≤0.05,the
holdingtimeofstandardsolutionspreparedinwater.Insuchcases,alarge
precision will be very poor.At such very low concentrations, a fairly large
volume of properly preserved, standard solution should be prepared and
number of replicate determinations will be required to bring the 99 %
carried through the steps of the practice in the same manner as a sample.
confidenceintervaltowithin15 %oftheconcentrationfound.Underthese
The volume of solution required can be estimated using the equation in
circumstances, it may be desirable to fortify the sample with the
7.1.1.
constituent of interest to increase the concentration to a point where the
7.1.1 Based on the estimated precision of the test (deter-
precision will be improved and fewer replicates will be required for the
holdingtimedetermination.However,theholdingtimemaybedifferentat
mined from past experience or from precision data reported in
the higher concentration than it would be at the lower concentration. This
the test method), calculate the estimated total volume of
decision is left to the judgement of the analyst.
samplerequiredtoperformtheholdingtimedeterminationplus
7.2.2 Accurately measure the volume of the remainder of
a precision study. Estimate this volume as follows:
the sample and fortify with a known concentration of the
V 5 A 3B 3C 12 A 3D (1)
~ ! ~ !
constituent of interest.
7.2.3 Immediately perform an appropriate number (usually
10) of replicate analyses of the sample as described in the
Reagent Chemicals, American Chemical Society Specifications, American
Chemical Society, Washington, DC. For Suggestions on the testing of reagents not
appropriate procedure.
listed by the American Chemical Society, see Annual Standards for Laboratory
7.2.4 Calculate the mean concentration, the standard devia-
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
tion, and relative standard deviation of these replicate deter-
and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,
MD. minations (see Practice D4375). Proceed to 8.1.
D4841 − 88 (Reapproved 2008)
7.3 Determination of Single-Operator Precision—Organic 7.3.3.5 Calculate the mean concentration, the standard de-
Methods: viation, and the relative standard deviation of these replicate
determinations (see Practice D4375). Proceed to 8.1.
7.3.1 General Organic Constituent Methods—Immediately
after sample collection, analyze an appropriate number (usu- 7.3.4 Purgeable Organic Compounds :
ally 10) of measured volumes of sample as described in the
7.3.4.1 Immediately after collection, perform an appropriate
appropriate procedure. If a measurable concentration of organ-
number(usually10)ofreplicatedeterminationsoftheconstitu-
ics is found, proceed to 7.3.1.1. If the concentration of the
ent of interest by analyzing separate aliquots of sample that
organic compounds is below the criterion of detection at a P
have been collected in hermetically sealed containers. If a
level of ≤ 0.05, collect another sample and repeat the analysis
measurable concentration is found, proceed to 7.3.4.3.Ifthe
until a sample containing a measurable concentration is ob-
concentration is below the criterion of detection at a P level of
tained (see Note 4).
≤ 0.05, either fortify the sample as described in 7.3.4.2 or
collect another sample and repeat the analysis (see Note 4).
NOTE 5—Since there is no way of positively identifying all of the
7.3.4.2 If the sample requires fortification, open all of the
compounds that may be contributing to the values found in the general
remaining containers and transfer the contents to a graduated
organic constituent methods, the sample cannot be fortified. To carry out
the holding time determination, a sample must be obtained that contains a
cylinder to measure the total volume of the remaining sample.
measurable concentration of organics in order to carry out the study.
Then transfer the sample to an aspirator bottle fitted with a
stopcock at the bottom. Transfer, by means of a syringe, a
7.3.1.1 Calculate the mean concentration, the standard de-
measured volume of stock solution containing a known con-
viation, and the relative standard deviation of these replicate
centration of the constituent of interest into the sample. The
determinations (see Practice D4375). Proceed to 8.1.
syringe needle should be below the surface of the liquid during
7.3.2 Specific Organic Constituent Methods (Applicable to
the transfer. Stopper the bottle and mix well. Carefully transfer
methodsthatdonotrequireextractionofthesamplecontainer):
(bydrainingthroughthestopcock)thesampletoseparatesmall
7.3.2.1 Immediately after sample collection, analyze an
glass vials. Take care to carry out the sample transfer with a
appropriate number (usually 10) of measured volumes of
minimum of sample agitation and aeration. Fill each sample
sample as determined in the appropriate procedure. If a
vial to overflowing so that a convex meniscus forms at the top.
measurable concentration of the constituent of interest is
Seal each vial as described in Practices D3694.
found, proceed to 7.3.2.4. If not, either collect another sample
or fortify the sample as described in 7.3.2.2 and reanalyze (see
NOTE 6—It is recommended that the operator’s technique used in
Note 4). transferring solutions of purgeable organic compounds be tested by
preparation and analysis of replicates prepared from a standard solution.
7.3.2.2 Accurately measure the volume of the remainder of
This should be done to make certain that no loss of purgeable organic
the sample and fortify it with a known concentration of the
compounds is occurring during transfer. Such loss can seriously bias the
constituent of i
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