ASTM D4841-88(2013)e1
(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
5.1 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.
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
´1
Designation: D4841 − 88 (Reapproved 2013)
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.
ε NOTE—Editorial corrections made throughout in August 2013.
1. Scope in Closed Conduits (Withdrawn 2003)
D1193 Specification for Reagent Water
1.1 This practice covers the means of estimating the period
D2777 Practice for Determination of Precision and Bias of
of time during which a water sample can be stored after
Applicable Test Methods of Committee D19 on Water
collection and preservation without significantly affecting the
D3694 Practices for Preparation of Sample Containers and
accuracy of analysis.
for Preservation of Organic Constituents
1.2 The maximum holding time is dependent upon the
D4210 Practice for Intralaboratory Quality Control Proce-
matrix used and the specific analyte of interest. Therefore,
dures and a Discussion on Reporting Low-Level Data
water samples from a specific source must be tested to
(Withdrawn 2002)
determinetheperiodoftimethatsampleintegrityismaintained
D4375 Practice for Basic Statistics in Committee D19 on
by standard preservation practices.
Water
E178 Practice for Dealing With Outlying Observations
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. Terminology
provideinformationregardingdegradationoftheconstituentof
3.1 Definitions—For definitions of terms used in this
interest or changes in the matrix that may occur from the time
practice, refer to Terminology D1129.
of sample collection to the time of the initial analysis.
3.1.1 criterion of detection—the minimum quantity that
1.4 The values stated in SI units are to be regarded as
must be observed before it can be stated that a substance has
standard. No other units of measurement are included in this
been discerned with an acceptable probability that the state-
standard.
ment is true (see Practice D4210).
1.5 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 maximum holding time—the maximum period of time
responsibility of the user of this standard to establish appro-
during which a properly preserved sample can be stored before
priate safety and health practices and determine the applica-
such degradation of the constituent of interest or change in
bility of regulatory limitations prior to use.
sample matrix occurs that the systematic error exceeds the
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
4.1 Holding time is estimated by means of replicate analy-
ses at discrete time intervals using a large volume of a water
This practice is under the jurisdiction of ASTM Committee D19 on Water and
sample that has been properly collected and preserved. A
is the direct responsibility of Subcommittee D19.02 on Quality Systems,
Specification, and Statistics.
sufficient number of replicate analyses are performed to main-
Current edition approved Jan. 1, 2013. Published January 2013. Originally
tain the 99 % confidence interval within 15 % of the concen-
approved in 1988. Last previous edition approved in 2008 as D4841 – 88 (2008).
tration found at zero time. Concentration of the constituent of
DOI: 10.1520/D4841-88R13E01.
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
Standards volume information, refer to the standard’s Document Summary page on The last approved version of this historical standard is referenced on
the ASTM website. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
´1
D4841 − 88 (2013)
interest is plotted versus time. The maximum holding time is 7.1.1 Based on the estimated precision of the test (deter-
the period of time from sample collection to such time that mined from past experience or from precision data reported in
degradation of the constituent of interest or change in sample the test method), calculate the estimated total volume of
matrix occurs and the systematic error exceeds the 99 % samplerequiredtoperformtheholdingtimedeterminationplus
confidence interval (not to exceed 15 %) of the test calculated a precision study. Estimate this volume as follows:
around the mean concentration at zero time. Prior to the
V 5 A 3B 3C 12 A 3D (1)
~ ! ~ !
determination of holding time, each laboratory must generate
where:
itsownprecisiondatainmatrixwater.Thesedataarecompared
to the pooled single-operator precision data on reagent water V = estimated volume of sample required, mL,
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
somewhat different conclusions each time that this practice is applied.
holding time study (excluding the initial time zero
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
6.1 Purity of Reagents—Reagent grade chemicals shall be that calculated in 7.1.1 be collected in order to make certain that sufficient
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,
as described in the appropriate procedure. If a measurable
TypeII,anddemonstratedtobefreeofspecificinterferencefor
concentration of the constituent of interest is found, proceed to
the test being performed.
7.2.4.Iftheconcentrationoftheconstituentofinterestisbelow
7. Determination of Holding Time
7.1 Collection of Sample:
TABLE 1 Approximate Number of Replicate Determinations
Required at Each Interval in the Holding Time Study Based on
NOTE 2—In some instances, it may be of interest to determine the
the Estimated Relative Standard Deviation of the Test in the
holdingtimeofstandardsolutionspreparedinwater.Insuchcases,alarge
Matrix Under Study
volume of properly preserved, standard solution should be prepared and
Estimated RSD, % Approximate Number of Replicates
carried through the steps of the practice in the same manner as a sample.
The volume of solution required can be estimated using the equation in 1–4 1
7.1.1. 5–6 2
7–8 3
10 5
Reagent Chemicals, American Chemical Society Specifications, American
11 6
Chemical Society, Washington, DC, www.chemistry.org. For suggestions on the
12 7
testing of reagents not listed by the American Chemical Society, see Analar
13 8
Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the
14 10
United States Pharmacopeia and National Formulary, U.S. Pharmacopeial 15 11
Convention, Inc. (USPC), Rockville, MD, http://www.usp.org.
´1
D4841 − 88 (2013)
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
the sample to separate properly prepared (see Practices D3694)
such that it approaches the criterion of detection at a P level of ≤0.05, the
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
ally 10) of replicate determinations of the constituent of
constituent of interest to increase the concentration to a point where the
interest by analyzing the sample in the containers. If a
precision will be improved and fewer replicates will be required for the
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.
7.3.4 Purgeable Organic Compounds:
Methods:
7.3.1 General Organic Constituent Methods—Immediately 7.3.4.1 Immediately after collection, perform an appropriate
number(usually10)ofreplicatedeterminationsoftheconstitu-
after sample collection, analyze an appropriate number (usu-
ally 10) of measured volumes of sample as described in the ent of interest by analyzing separate aliquots of sample that
have been collected in hermetically sealed containers. If a
appropriate procedure. If a measurable concentration of organ-
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
concentration is below the criterion of detection at a P level of
organic compounds is below the criterion of detection at a P
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
collect another sample and repeat the analysis (see Note 4).
until a sample containing a measurable concentration is ob-
tained (see Note 4). 7.3.4.2 If the sample requires fortification, open all of the
remaining containers and transfer the contents to a graduated
NOTE 5—Since there is no way of positively identifying all of the
cylinder to measure the total volume of the remaining sample.
compounds that may be contributing to the values found in the general
organic constituent methods, the sample cannot be fortified. To carry out Then transfer the sample to an aspirator bottle fitted with a
the holding time determination, a sample must be obtained that contains a
stopcock at the bottom. Transfer, by means of a syringe, a
measurable concentration of organics in order to carry out the study.
measured volume of stock solution containing a known con-
7.3.1.1 Calculate the mean concentration, the standard
centration of the constituent of interest into the sample. The
deviation, and the relative standard
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.