ASTM D4841-88(2018)

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: D4841 − 88 (Reapproved 2018)
Standard Practice 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 2. Referenced Documents
2.1 ASTM Standards:
1.1 This practice covers the means of estimating the period
D1129 Terminology Relating to Water
of time during which a water sample can be stored after
D1193 Specification for Reagent Water
collection and preservation without significantly affecting the
D2777 Practice for Determination of Precision and Bias of
accuracy of analysis.
Applicable Test Methods of Committee D19 on Water
1.2 The maximum holding time is dependent upon the
D3694 Practices for Preparation of Sample Containers and
matrix used and the specific analyte of interest. Therefore,
for Preservation of Organic Constituents
water samples from a specific source must be tested to
D4210 Practice for Intralaboratory Quality Control Proce-
determinetheperiodoftimethatsampleintegrityismaintained dures and a Discussion on Reporting Low-Level Data
by standard preservation practices. (Withdrawn 2002)
D4375 Practice for Basic Statistics in Committee D19 on
1.3 In the event that it is not possible to analyze the sample
Water
immediately at the time of collection, this practice does not
E178 Practice for Dealing With Outlying Observations
provideinformationregardingdegradationoftheconstituentof
interest or changes in the matrix that may occur from the time
3. Terminology
of sample collection to the time of the initial analysis.
3.1 Definitions—For definitions of terms used in this
1.4 The values stated in SI units are to be regarded as standard, refer to Terminology D1129.
3.1.1 criterion of detection, n—the minimum quantity that
standard. No other units of measurement are included in this
must be observed before it can be stated that a substance has
standard.
been discerned with an acceptable probability that the state-
1.5 This standard does not purport to address all of the
ment is true (see Practice D4210).
safety concerns, if any, associated with its use. It is the
3.2 Definitions of Terms Specific to This Standard:
responsibility of the user of this standard to establish appro-
3.2.1 acceptable holding time, n—any period of time less
priate safety, health, and environmental practices and deter-
than or equal to the maximum holding time.
mine the applicability of regulatory limitations prior to use.
3.2.2 maximum holding time, n—the maximum period of
1.6 This international standard was developed in accor-
time during which a properly preserved sample can be stored
dance with internationally recognized principles on standard-
before such degradation of the constituent of interest or change
ization established in the Decision on Principles for the
in sample matrix occurs that the systematic error exceeds the
Development of International Standards, Guides and Recom-
99 % confidence interval (not to exceed 15 %) of the test
mendations issued by the World Trade Organization Technical
calculated around the mean concentration found at zero time.
Barriers to Trade (TBT) Committee.
4. Summary of Practice
4.1 Holding time is estimated by means of replicate analy-
ses at discrete time intervals using a large volume of a water
1 2
This practice is under the jurisdiction of ASTM Committee D19 on Water and For referenced ASTM standards, visit the ASTM website, www.astm.org, or
is the direct responsibility of Subcommittee D19.02 on Quality Systems, contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Specification, and Statistics. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Oct. 15, 2018. Published October 2018. Originally the ASTM website.
ɛ1 3
approved in 1988. Last previous edition approved in 2013 as D4841 – 88 (2013) . The last approved version of this historical standard is referenced on
DOI: 10.1520/D4841-88R18. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D4841 − 88 (2018)
volume of properly preserved, standard solution should be prepared and
sample that has been properly collected and preserved. A
carried through the steps of the practice in the same manner as a sample.
sufficient number of replicate analyses are performed to main-
The volume of solution required can be estimated using the equation in
tain the 99 % confidence interval within 15 % of the concen-
7.1.1.
tration found at zero time. Concentration of the constituent of
7.1.1 Based on the estimated precision of the test (deter-
interest is plotted versus time. The maximum holding time is
mined from past experience or from precision data reported in
the period of time from sample collection to such time that
the test method), calculate the estimated total volume of
degradation of the constituent of interest or change in sample
samplerequiredtoperformtheholdingtimedeterminationplus
matrix occurs and the systematic error exceeds the 99 %
a precision study. Estimate this volume as follows:
confidence interval (not to exceed 15 %) of the test calculated
V 5 A 3B 3C 12 A 3D (1)
around the mean concentration at zero time. Prior to the ~ ! ~ !
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
NOTE 1—This practice generates only limited data which may not lead
at each interval in the holding time study (see Table 1),
to consistent conclusions each time that the test is applied. In cases where
the concentration of the constituent of interest changes gradually over an
C = estimated number of time intervals required for the
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
5. Significance and Use D = number of replicate determinations performed in initial
precision study (usually 10).
5.1 In order to obtain meaningful analytical data, sample
preservation techniques must be effective from the time of 7.1.2 Based on the volume calculated in 7.1.1, collect a
sample collection to the time of analysis. A laboratory must sufficient volume of the specific matrix to be tested to perform
confirm that sample integrity is maintained throughout maxi- a precision study and the holding time study. Collect the
mum time periods between sample collection and analysis. In
sample in a properly prepared sample container or series of
manycases,itisusefultoknowthemaximumholdingtime.An containers.Refertotheprocedurefortheconstituentofinterest
evaluation of holding time is useful also in judging the efficacy
for specific instructions on sample collection procedures.
of various preservation techniques.
NOTE 3—The total volume of sample calculated in 7.1.1 is only an
estimate.Dependinguponthedegreeofcertaintywithwhichtheprecision
6. Reagents
can be estimated, it is recommended that a volume somewhat in excess of
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
used in all tests. Unless otherwise indicated, it is intended that
may want to consider performing a preliminary precision study prior to
all reagents shall conform to the specifications of the Commit-
sample collection in order to be certain that the estimate of precision used
tee onAnalytical Reagents of theAmerican Chemical Society,
in 7.1.1 is reasonably accurate.
where such specifications are available. Other grades may be
7.1.3 Add the appropriate preservation reagents to the
used provided it is first ascertained that the reagent is of
sample immediately after collection. Immediately proceed to
sufficiently high purity to permit its use without lowering the
7.2 or 7.3 depending upon whether inorganic or organic
accuracy of the determination.
compounds are being determined.
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-
6.2 Purity of Water—Referencetowatershallbeunderstood
propriate number (usually 10) of measured volumes of sample
to mean reagent water conforming to Specification D1193,
TypeII,anddemonstratedtobefreeofspecificinterferencefor
TABLE 1 Approximate Number of Replicate Determinations
the test being performed.
Required at Each Interval in the Holding Time Study Based on
the Estimated Relative Standard Deviation of the Test in the
7. Determination of Holding Time
Matrix Under Study
7.1 Collection of Sample:
Estimated RSD, % Approximate Number of Replicates
1–4 1
NOTE 2—In some instances, it may be of interest to determine the
5–6 2
holdingtimeofstandardsolutionspreparedinwater.Insuchcases,alarge
7–8 3
10 5
Reagent Chemicals, American Chemical Society Specifications, American
11 6
Chemical Society, Washington, DC. For suggestions on the testing of reagents not
12 7
listed by the American Chemical Society, see Analar Standards for Laboratory
13 8
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
14 10
and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville, 15 11
MD.
D4841 − 88 (2018)
as described in the appropriate procedure. If a measurable 7.3.2.4 Calculate the mean concentration, the standard
concentration of the constituent of interest is found, proceed to deviation, and the relative standard deviation of these replicate
7.2.4.Iftheconcentrationoftheconstituentofinterestisbelow determinations (see Practice D4375). Proceed to 8.1.
the criterion of detection at a P level of ≤0.05, fortify the
7.3.3 Specific Organic Constituent Methods—(Applicableto
sample as described in 7.2.2 and reanalyze or collect another
methods that require extraction of the sample container):
sample.
7.3.3.1 If the sample was collected in a container other than
litre glass bottles, immediately transfer shaken, 1-Lportions of
NOTE 4—If the concentration of the constituent of interest is very low
such that it approaches the criterion of detection at a P level of ≤0.05, the
the sample to separate properly prepared (see Practices D3694)
precision will be very poor.At such very low concentrations, a fairly large
litre glass bottles which have had the litre mark placed on the
number of replicate determinations will be required to bring the 99 %
neck of the container.
confidenceintervaltowithin15 %oftheconcentrationfound.Underthese
7.3.3.2 Immediately perform an appropriate number (usu-
circumstances, it may be desirable to fortify the sample with the
constituent of interest to increase the concentration to a point where the ally 10) of replicate determinations of the constituent of
precision will be improved and fewer replicates will be required for the
interest by analyzing the sample in the containers. If a
holdingtimedetermination.However,theholdingtimemaybedifferentat
measurable concentration of the constituent of interest is
the higher concentration than it would be at the lower concentration. This
found,proceedto7.3.3.5.Ifnot,fortifythesampleasdescribed
decision is left to the judgement of the analyst.
in 7.3.3.3 and reanalyze (see Note 4).
7.2.2 Accurately measure the volume of the remainder of
7.3.3.3 Fortify the sample in all of the remaining glass
the sample and fortify with a known concentration of the
bottles with a known concentration of the constituent of
constituent of interest.
interest by adding an accurately measured small volume of a
7.2.3 Immediately perform an appropriate number (usually
concentrated standard solution of the analyte.
10) of replicate analyses of the sample as described in the
7.3.3.4 Immediately perform an appropriate number (usu-
appropriate procedure.
ally 10) of replicate analyses of the fortified sample as
7.2.4 Calculate the mean concentration, the standard
described in the appropriate procedure.
deviation, and relative standard deviation of these replicate
7.3.3.5 Calculate the mean concentration, the standard
determinations (see Practice D4375). Proceed to 8.1.
deviation, and the relative standard deviation of these replicate
7.3 Determination of Single-Operator Precision—Organic
determinations (see Practice D4375). Proceed to 8.1.
Methods:
7.3.4 Purgeable Organic Compounds:
7.3.1 General Organic Constituent Methods—Immediately
7.3.4.1 Immediately after collection, perform an appropriate
after sample collection, analyze an appropriate number (usu-
number(usually10)ofreplicatedeterminationsoftheconstitu-
ally 10) of measured volumes of sample as described in the
ent of interest by analyzing separate aliquots of sample that
appropriate procedure. If a measurable concentration of organ-
have been collected in hermetically sealed containers. If a
ics is found, proceed to 7.3.1.1. If the concentration of the
measurable concentration is found, proceed to 7.3.4.3.Ifthe
organic compounds is below the criterion of detection at a P
concentration is below the criterion of detection at a P level of
level of ≤0.05, collect another sample and repeat the analysis
≤0.05, either fortify the sample as described in 7.3.4.2 or
until a sample containing a measurable concentration is ob-
collect another sample and repeat t
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