1、Designation: E1303 95 (Reapproved 2017)Standard Practice forRefractive Index Detectors Used in Liquid Chromatography1This standard is issued under the fixed designation E1303; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the yea
2、r 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 tests used to evaluate the perfor-mance and to list certain descriptive specifications of ar
3、efractive index (RI) detector used as the detection componentof a liquid chromatographic (LC) system.1.2 This practice is intended to describe the performance ofthe detector both independent of the chromatographic system(static conditions, without flowing solvent) and with flowingsolvent (dynamic co
4、nditions).1.3 The values stated in SI units are to be regarded as thestandard.1.4 This standard does not purport 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, health, and environmental pra
5、ctices and deter-mine the applicability of regulatory limitations prior to use.1.5 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides a
6、nd Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2E386 Practice for Data Presentation Relating to High-Resolution Nuclear Magnetic Resonance (NMR) Spec-troscopy (Withdrawn 2015)33. Significance and Use3.1
7、Although it is possible to observe and measure each ofseveral characteristics of a detector under different and uniqueconditions, it is the intent of this practice that a complete set ofdetector test results should be obtained under the same oper-ating conditions. It should also be noted that to spe
8、cifycompletely a detectors capability, its performance should bemeasured at several sets of conditions within the useful rangeof the detector.3.2 The objective of this practice is to test the detector underspecified conditions and in a configuration without an LCcolumn. This is a separation independ
9、ent test. In certaincircumstances it might also be necessary to test the detector inthe separation mode with an LC column in the system, and theappropriate concerns are also mentioned. The terms and testsdescribed in this practice are sufficiently general so that theymay be adapted for use at whatev
10、er conditions may be chosenfor other reasons.4. Noise, Drift, and Flow Sensitivity4.1 Descriptions of Terms Specific to This Standard:4.1.1 short term noisethis noise is the mean amplitude inrefractive index units (RIU) for random variations of thedetector signal having a frequency of one or more cy
11、cles perminute. Short term noise limits the smallest signal detectableby an RI detector, limits the precision attainable, and sets thelower limit on the dynamic range. This noise corresponds toobserved noise of the RI detector only. (The actual noise of theLC system may be larger or smaller than the
12、 observed value,depending upon the method of data collection, or signalmonitoring of the detector, since observed noise is a function ofthe frequency, speed of response and the band width of therecorder or other electronic circuit measuring the detectorsignal.)4.1.2 long term noisethis noise is the
13、maximum amplitudein RIU for random variations of the detector signal withfrequencies between 6 and 60 cycles per h (0.1 and 1.0 cyclesper min). It represents noise that may be mistaken for alate-eluting peak. This noise corresponds to the observed noiseonly and may not always be present.4.1.3 driftt
14、he average slope of the long term noise enve-lope expressed in RIU per hour as measured over a period of1h.4.1.4 staticrefers to the noise and drift measured underconditions of no flow.4.1.5 dynamicrefers to the noise and drift measured at aflow rate of 1.0 mL/min.1This practice is under the jurisdi
15、ction of ASTM Committee E13 on MolecularSpectroscopy and Separation Science and is the direct responsibility of Subcom-mittee E13.19 on Separation Science.Current edition approved Oct. 1, 2017. Published October 2017. Originallyapproved in 1989. Last previous edition approved in 2010 as E1303 95 (20
16、10).DOI: 10.1520/E1303-95R17.2For 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.3The last approved version of th
17、is historical standard is referenced onwww.astm.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in th
18、e Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.14.1.6 flow sensitivitythe rate of change of signal displace-ment (in RIU) vs flow rate (in mL/min) resulting from ste
19、pchanges in flow rate calculated at 1 mL/min as described in4.3.12.4.2 Test Conditions:4.2.1 The same test solvent must be used in both sample andreference cells. The test solvent used and its purity should bespecified. Water equilibrated with the laboratory atmospherecontaining minimum impurities i
20、s the preferred test solvent formeasuring noise and drift. Water for this purpose (preferablypurified by distillation, deionization, or reverse osmosis)should be drawn, filtered through a 0.45-m filter, and allowedto stand in a loosely covered container for several hours atambient temperature in the
21、 laboratory in which testing is to becarried out. This will ensure complete equilibration of thewater with the gases in the laboratory atmosphere.NOTE 1It is essentially impossible to maintain a constant RI value ofde-gassed water and of very dilute samples in de-gassed water. This is dueto the fact
22、 that the difference in refractive index between completelyde-gassed water and atmosphere-equilibrated water is 1.5 106RIU.4Thus, small differences in the concentration of dissolved gases betweenthe sample and the trapped reference can lead to significant errors inmeasurement of solutions where the
23、expected difference in RI due tosolute is of the order of 106RIU or less. Therefore, in order to minimizeerror in determining samples with small RIU differences between them,atmosphere-equilibrated water (5.2.1) is recommended as the solvent fordetermining linearity and minimum detectability (Sectio
24、n 5).4.2.2 The detector should be located at the test site andswitched on at least 24 h prior to the start of testing. Somedetectors provide an oven to thermostat the optics assembly.The oven should be set at a suitable temperature, following themanufacturers recommendations, and this temperature sh
25、ouldbe noted and maintained throughout the test procedures.4.2.3 Linearity and speed of response of the recorder orother data acquisition device used should be such that it doesnot distort or otherwise interfere with the performance of thedetector.5If additional amplifiers are used between the detec
26、torand the final readout device, their characteristics should alsofirst be established.4.3 Methods of Measurement:4.3.1 Connecta1m(39.37 in.) length of clean, dry,stainless steel tubing of 0.25 mm (0.009 to 0.01 in.) insidediameter in place of the analytical column. The tubing can bestraight or coil
27、ed to minimize the space requirement. Thetubing should terminate in standard low dead volume fittings toconnect with the detector and to the pump. Commercialchromatographs may already contain some capillary tubing toconnect the pump to the injection device. If this is of a similardiameter to that sp
28、ecified, it should be included in the 1.0 mlength; if significantly wider, it should be replaced for this test.4.3.2 Repeatedly rinse the reservoir and chromatographicsystem, including the detector, with the test solvent prepared asdescribed in 4.2.1, until all previous solvent is removed fromthe sy
29、stem. Fill the reservoir with the test solvent.4.3.3 Thoroughly flush the reference cell with the samesolvent; keep the reference cell static.4.3.3.1 It may be necessary to flush both sample andreference cells with an intermediate solvent (such as methanolor acetone), if the solvent previously used
30、in the system isimmiscible with the test solvent.4.3.4 Allow the chromatographic system to stabilize for atleast 60 min without flow. The detector range, Note 2, shouldbe set such that the amplitude of short term noise may be easilymeasured. Ideally, the output should contain no filtering of thesign
31、al. If the filtering cannot be turned off, the minimum timeconstant should be set and noted in the evaluation. Manuals ormanufacturers should be consulted to determine if time con-stant and detector range controls are coupled, and informationshould be obtained to determine if they can be decoupled f
32、ortesting. Set the recorder zero to near mid-scale. Record at least1 h of baseline under these static conditions, during which timethe ambient temperature should not change by more than 2 C.NOTE 2RI detectors will have one or more controls labeledattenuation, range, sensitivity, and scale factor.All
33、 are used to set the fullscale range (in RIU) of an output display device such as a strip chartrecorder.4.3.5 Draw pairs of parallel lines, each between12 to 1 minin length, to form an envelope of all observed randomvariations over any 15-min period (Fig. 1). Draw the parallellines in such a way as
34、to minimize the distance between them.Measure the distance perpendicular to the time axis betweenthe parallel lines. Convert this value to RIU (5.2.9). Calculatethe mean value over all the segments; this value is the staticshort term noise.4.3.6 Now mark the center (center of gravity) of eachsegment
35、 over the 15-min period of the short term noisemeasurement. Draw a series of parallel lines to these centers,each 10 min in length (Fig. 1), and choose that pair of lineswhose distance apart perpendicular to the time axis is greatest.This distance is the static long term noise.4.3.7 Draw the pair of
36、 parallel lines, over the1hofmeasurement, that minimizes the distance perpendicular to thetime axis between the parallel lines. The slope of either line,measured in RIU/h, is the static drift.4.3.8 Set the solvent delivery system to a flow rate that haspreviously been shown to deliver 1.0 mL/min und
37、er the sameconditions of capillary tubing, solvent, and temperature. Allowat least 15 min to stabilize. Set the recorder zero nearmid-scale. Record at least1hofbaseline under these flowingconditions, during which time the ambient temperature shouldnot change by more than 2 C.4.3.9 Draw pairs of para
38、llel lines, measure the perpendiculardistances, and calculate the dynamic short term noise, in themanner described in 4.3.5 for the static short term noise.4.3.10 Make the measurement for the dynamic long termnoise following the procedure outlined in 4.3.6.4.3.11 Draw the pair of parallel lines in a
39、ccordance with4.3.7. The slope of this line is the dynamic drift.4.3.12 Stop the chromatographic flow.Allow at least 15 minfor re-equilibration. Set the recorder at about 5 % of full scaleand leave the detector range setting at the value used for thenoise measurements. Set the solvent delivery syste
40、m at a flow4Munk, M. N., Liquid Chromatography Detectors, (T. M. Vickrey, Ed.), MarcelDekker, New York and Basel, 1983, pp. 165204.5Bonsall, R. B., “The Chromatography SlaveThe Recorder,” Journal of GasChromatography, Vol 2, 1964, pp. 277284.E1303 95 (2017)2rate of 0.5 mL/min. Run for 15 min, or mor
41、e if necessary forre-equilibration, at a slow recorder speed. Increase the flow rateto 1.0 mL/min and record for 15 min or more. Run at 2.0, 4.0,and 8.0 mL/min if the pressure flow limit of the chromato-graphic system is not exceeded. If necessary, adjust the detectorrange to maintain an on-scale re
42、sponse.4.3.13 Draw a horizontal line through the plateau producedat each flow rate, after a steady state is reached (Fig. 2).Measure the vertical displacement between these lines, andexpress in RIU (5.2.9). Plot these values versus flow rate. Drawa smooth curve connecting the points and draw a tange
43、nt at1 mLmin (Fig. 3). Express the slope of the line as the flowsensitivity in RIU min/mL. It is preferred to give the numericalvalue and show the plot as well.5. Minimum Detectability, Linear Range, DynamicRange, and Calibration5.1 Descriptions of Terms Specific to this Standard:5.1.1 minimum detec
44、tabilitythat concentration of a spe-cific solute in a specific solvent that gives a signal equal totwice the static short-term noise.5.1.1.1 DiscussionThe static short-term noise is a mea-surement of peak-to-peak noise. A statistical approach to noisesuggests that a value of three times the rms (roo
45、t-mean-square)noise would ensure that any value outside this range would notbe noise with a confidence level of greater than 99 %. Sincepeak-to-peak noise is approximately five times the rmsnoise,5,6the minimum detectability defined in this practice is amore conservative estimate. Minimum detectabil
46、ity, as definedin this practice, should not be confused with the limit ofdetection in an analytical method using a refractive indexdetector.5.1.2 sensitivity (response factor)the signal output perunit concentration of the test substance in the test solvent, inaccordance with the following relationsh
47、ip:S 5 R/C (1)6Blair, E. J., Introduction to Chemical Instrumentation, McGraw-Hill, NewYork, NY, 1962, and Practice E386.FIG. 1 Examples for the Measurement of Short Term Noise, LongTerm Noise and DriftFIG. 2 Example for the Measurement of Flow SensitivityFIG. 3 Example of Plot for Calculation of Fl
48、ow SensitivityE1303 95 (2017)3where:S = sensitivity (response factor), RIUL/g,R = measured detector response, RIU, andC = concentration of the test substance in the test solventg/L.5.1.3 linear rangethe range of concentrations of the testsubstance in the test solvent, over which the sensitivity of t
49、hedetector is constant to with 5 % as determined from thelinearity plot specified in 5.2.13. The linear range may beexpressed in three different ways:5.1.3.1 As the ratio of the upper limit of linearity obtainedfrom the linearity plot, and the minimum linear concentration,both measured for the same test substance in the same testsolvent as follows:L.R. 5 Cmax/Cmin(2)where:L.R. = linear range of the detector,Cmax= upper limit of linearity obtained from the linearityplot, g/L, andCmin= minimum linear concentration, g/L, as defined in5.2.13.1, the minimum l
