1、Designation:E151193(Reapproved 2010)Standard Practice forTesting Conductivity Detectors Used in Liquid and IonChromatography1This standard is issued under the fixed designation E1511;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,th
2、e year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This practice covers the testing of the performance ofconductivity detectors used as the detection component of a
3、liquid or ion chromatography system.1.2 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.2.Referenced Documents2.1 ASTM Standards:2E1151 Practice for Ion Chromatography Terms and Rela-tionships3.Terminology3.1 See Practice E1151.3
4、.2 Definitions:3.2.1 cell constantthe cell constant(K)of a conductivitycell is equal to 1/A,so =G K.3.2.1.1 DiscussionIf the cell constant of the flow-throughcell used is equal to one,then the conductivity equals theconductance.Although the cell constant is often specified forconductivity detectors,
5、there is little practical value in knowingthe constant as long as the detector is properly calibrated forconductivity.3.2.2 conductancethe conductance(G)of a solution is theinverse of the resistance measured between two electrodes in acell,expressed in units of siemens(S),equal to inverse ohms.3.2.2
6、.1 DiscussionThe term resistance refers specificallyto the dc resistance to ionic current,independent of thecapacitive reactance at the interfaces between the electrodesand the solution.3.2.3 conductivitysince the conductance is dependent onboth the conductive properties of the solution and on thedi
7、mensions of the electrodes and the cell,the conductivity()of the solution is defined to be independent of electrode andcell dimensions.Specifically,5 G1A(1)where:1=the distance between two planer disk electrodes,andA=the electrodes surface area.3.2.3.1 DiscussionIn liquid and ion chromatography,cell
8、dimensions are commonly measured in centimetres,so theunits of are S/cm.(Alternatively,the SI units of S/m may beused.S/m=100 S/cm.)3.2.4 driftthe average slope of the noise envelope ex-pressed in nano siemens per centimetre per hour as measuredover a period of 1 h.3.2.5 equivalent conductivityof an
9、 ionic solute,the con-tribution of the solute to the total conductivity of the solution,measured in microsiemens per centimetre,divided by itsconcentration in milliequivalents/litre.3.2.6 flow dependence ratethe change in measured con-ductivity as a function of flow rate.3.2.7 limiting equivalent co
10、nductivityof an ionic solute,itsequivalent conductivity extrapolated to infinite dilution.3.2.8 linear rangeof a conductivity detector for a givensolute in a specific solvent,the concentration range of solutefor which the detector response factor is within 5%of theresponse factor in the middle of th
11、e range as determined fromthe linearity plot specified in Section 11.3.2.8.1 DiscussionThe lower limit may be limited bynoise,and the upper limit by deviation from linearity.(Theupper limit may instead be limited by the maximum full-scaledeflection on the detectors least sensitive output range.)3.2.
12、9 long-term noisethe maximum amplitude in nanosiemens per centimetre for all random variations of the detectoroutput of frequencies between 2 and 60 cycles per hour.3.2.9.1 DiscussionLong-term noise represents noise thatcan be mistaken for eluting peaks.1This practice is under the jurisdiction of AS
13、TM Committee E13 on MolecularSpectroscopy and Separation Science and is the direct responsibility of Subcom-mittee E13.19 on Separation Science.Current edition approved Nov.1,2010.Published November 2010.Originallyapproved in 1993.Last previous edition approved in 2005 as E1511-93(2005).DOI:10.1520/
14、E1511-93R10.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International,100 Barr Harbor Drive,PO
15、Box C700,West Conshohocken,PA 19428-2959.United States1 3.2.10 minimum detectabilityof a conductivity detector,that concentration of solute in a specific solvent that corre-sponds to twice the short-term noise.3.2.10.1 DiscussionBecause of the difficulty of pumpingsolvents through the chromatographi
16、c system without anycontamination of the solvents from the system,this quantitycan only be measured with solutes retained by a column.Sinceminimum detectability is dependent on the chromatographicsystem used,it is not measured in this practice.However,if theminimum detectability of a solute is measured on one systemwith one detector,the minimum detectability can be predictedwhen other detectors are tested on the same system bycomparing the measured values of short-term noise.3.2.11 response fact
