1、Designation:D 4515 85(Reapproved 2001)An American National StandardStandard Practice forEstimation of Holding Time for Water Samples ContainingOrganic Constituents1This standard is issued under the fixed designation D 4515;the number immediately following the designation indicates the year oforigina
2、l adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon(e)indicates an editorial change since the last revision or reapproval.1.Scope1.1 This practice describes the means of estimating theperiod of time during
3、 which a water sample can be stored aftercollection and preservation without significantly affecting theaccuracy of analysis.1.2 The maximum holding time is highly matrix-dependentand is also dependent on the specific analyte of interest.Therefore,water samples from a specific source must be testedt
4、o determine the period of time that sample integrity ismaintained by standard preservation practices.1.3 In those cases where it is not possible to analyze thesample immediately at the time of collection,this practice doesnot provide information regarding degradation of the constitu-ent of interest
5、or changes in matrix that may occur from thetime of sample collection to the time of the initial analysis.1.4 This practice does not provide information regardingholding time for concentration of analyte less than one order ofmagnitude above the criterion of detection.1.5 This standard does not purp
6、ort to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:D 1129 T
7、erminology Relating to Water2D 1193 Specification for Reagent Water2D 2777 Practice for Determination of Precision and Bias ofApplicable Methods of Committee D-19 on Water2D 3694 Practices for Preparation of Sample Containers andfor Preservation of Organic Constituents33.Terminology3.1 DefinitionsFo
8、r definitions of terms used in this prac-tice,refer to Terminology D 1129.3.2 Definitions of Terms Specific to This Standard:3.2.1 acceptable holding timeacceptable holding time isany period of time less than or equal to the maximum holdingtime.3.2.2 maximum holding timemaximum holding time isthe ma
9、ximum period of time during which a properly preservedsample can be stored before such degradation of the constituentof interest occurs or change in sample matrix occurs that thesystematic error exceeds the 99%confidence interval(not toexceed 15%)of the test about the mean concentration found atzero
10、 time.4.Summary of Practice4.1 Holding time is estimated by means of replicate analysisat discrete time intervals of a large volume of a water samplethat has been properly collected and preserved.Concentrationof the constituent of interest is plotted versus time.Themaximum holding time is the period
11、 of time from samplecollection to such time that degradation of the constituent ofinterest occurs or change in sample matrix occurs that thesystematic error exceeds the 99%confidence interval(not toexceed 15%)of the test about the mean concentration at zerotime.Prior to determination of holding time
12、,each laboratorymust generate its own precision data for use in the calculation.For those tests which are relatively imprecise,replicate deter-minations are performed at each time interval to maintain the99%confidence interval within 15%of the concentrationfound at zero time.NOTE1This practice gener
13、ates only limited data that may not lead toconsistent conclusions each time the test is applied.In cases where theconcentration of the constituent of interest changes very gradually over anextended period of time,the inherent variability in test results may lead tosomewhat different conclusions each
14、 time that the practice is applied.5.Significance and Use5.1 In order to obtain meaningful analytical data,samplepreservation techniques must be effective from the time ofsample collection to the time of analysis.This period of timemust be defined in order that the analyst may know how longsamples m
15、ay be stored prior to analysis.1This practice is under the jurisdiction of ASTM Committee D19 on Water andis the direct responsibility of Subcommittee D19.06 on Methods for Analysis forOrganic Substances in Water.Current edition approved Aug.30,1985.Published October 1985.2Annual Book of ASTM Standa
16、rds,Vol 11.01.3Annual Book of ASTM Standards,Vol 11.02.1Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959,United States.6.Reagents6.1 Purity of ReagentsReagent grade chemicals shallbeused in all tests.Unless otherwise indicated,it is intendedthat all reagents shall conform to the specifications of thecommittee on Analytical Reagents of the American ChemicalSociety,where such specifications are available.4Other gradesmay be used,provided it is first as
