1、Designation: E594 96 (Reapproved 2011)Standard Practice forTesting Flame Ionization Detectors Used in Gas orSupercritical Fluid Chromatography1This standard is issued under the fixed designation E594; the number immediately following the designation indicates the year oforiginal adoption or, in the
2、case of revision, the 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 of aflame ionization detector (FID)
3、used as the detection compo-nent of a gas or supercritical fluid (SF) chromatographicsystem.1.2 This recommended practice is directly applicable to anFID that employs a hydrogen-air or hydrogen-oxygen flameburner and a dc biased electrode system.1.3 This recommended practice covers the performance o
4、fthe detector itself, independently of the chromatographic col-umn, the column-to-detector interface (if any), and othersystem components, in terms that the analyst can use to predictoverall system performance when the detector is made part ofa complete chromatographic system.1.4 For general gas chr
5、omatographic procedures, PracticeE260 should be followed except where specific changes arerecommended herein for the use of an FID. For definitions ofgas chromatography and its various terms see recommendedPractice E355.1.5 For general information concerning the principles, con-struction, and operat
6、ion of an FID, see Refs (1, 2, 3, 4).21.6 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.7 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the u
7、ser of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. For specific safetyinformation, see Section 5.2. Referenced Documents2.1 ASTM Standards:3E260 Practice for Packed Column Gas ChromatographyE355 Practice
8、 for Gas Chromatography Terms and Rela-tionships2.2 CGA Standards:CGA P-1 Safe Handling of Compressed Gases in Contain-ers4CGA G-5.4 Standard for Hydrogen Piping Systems atConsumer Locations4CGA P-9 The Inert Gases: Argon, Nitrogen and Helium4CGA V-7 Standard Method of Determining Cylinder ValveOutl
9、et Connections for Industrial Gas Mixtures4CGA P-12 Safe Handling of Cryogenic Liquids4HB-3 Handbook of Compressed Gases43. Terminology3.1 Definitions:3.1.1 driftthe average slope of the baseline envelopeexpressed in amperes per hour as measured over12 h.3.1.2 noise (short-term)the amplitude express
10、ed in am-peres of the baseline envelope that includes all randomvariations of the detector signal of a frequency on the order of1 or more cycles per minute (see Fig. 1).3.1.2.1 DiscussionShort-term noise corresponds to theobserved noise only. The actual noise of the system may belarger or smaller th
11、an the observed value, depending upon themethod of data collection or signal monitoring from thedetector, since observed noise is a function of the frequency,speed of response, and the bandwidth of the electronic circuitmeasuring the detector signal.1This practice is under the jurisdiction of ASTM C
12、ommittee E13 on MolecularSpectroscopy and Separation Science and is the direct responsibility of Subcom-mittee E13.19 on Separation Science.Current edition approved Nov. 1, 2011. Published December 2011. Originallyapproved in 1977. The last previous edition approved in 2006 as E594 96 (2011).DOI: 10
13、.1520/E0594-96R11.2The boldface numbers in parentheses refer to the list of references appended tothis recommended practice.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, r
14、efer to the standards Document Summary page onthe ASTM website.4Available from Compressed Gas Association (CGA), 4221 Walney Rd., 5thFloor, Chantilly, VA 20151-2923, http:/.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.3 other
15、noiseFluctuations of the baseline envelope ofa frequency less than 1 cycle per minute can occur inchromatographic systems.3.1.4 DiscussionThe amplitude of these fluctuations mayactually exceed the short-term noise. Such fluctuations aredifficult to characterize and are not typically to be expected.T
16、hey are usually caused by other chromatographic componentssuch as the column, system contaminants, and flow variations.These other noise contributions are not derived from thedetector itself and are difficult to quantitate in a generalmanner. It is, however, important for the practicing chromatog-ra
17、pher to be aware of the occurrence of this type of noisecontribution.4. Significance and Use4.1 Although it is possible to observe and measure each ofthe several characteristics of a detector under different andunique conditions, it is the intent of this recommended practicethat a complete set of de
18、tector specifications should be ob-tained at the same operating conditions, including geometry,flow rates, and temperatures. It should be noted that to specifya detectors capability completely, its performance should bemeasured at several sets of conditions within the useful rangeof the detector. Th
19、e terms and tests described in this recom-mended practice are sufficiently general so that they may beused at whatever conditions may be chosen for other reasons.4.2 The FID is generally only used with non-ionizablesupercritical fluids as the mobile phase. Therefore, this stan-dard does not include
20、the use of modifiers in the supercriticalfluid.4.3 Linearity and speed of response of the recording systemor other data acquisition device used should be such that it doesnot distort or otherwise interfere with the performance of thedetector. Effective recorder response, Bonsall (5) and McWil-liam (
21、6), in particular, should be sufficiently fast so that it canbe neglected in sensitivity of measurements. If additionalamplifiers are used between the detector and the final readoutdevice, their characteristics should also first be established.5. Hazards5.1 Gas Handling SafetyThe safe handling of co
22、mpressedgases and cryogenic liquids for use in chromtography is theresponsibility of every laboratory. The CGA, a member groupof specialty and bulk gas suppliers, publishes the followingguidelines to assist the laboratory chemist to establish a safework environment. Applicable CGA publications inclu
23、deCGA P-1, CGA G-5.4, CGA P-9, CGA V-7, CGA P-12, andHB-3.6. Noise and Drift6.1 Methods of Measurement:6.1.1 With the attenuator set at maximum sensitivity (mini-mum attenuation), adjust the detector output with the “zero”control to near mid-scale on the recorder.Allow at least12 hofbaseline to be r
24、ecorded. Draw two parallel lines to form anenvelope that encloses the random excursions of a frequency ofapproximately 1 cycle per minute or more. Measure thedistance between the parallel lines at any particular time.Express the value as amperes of noise.6.1.2 Measure the net change in amperes of th
25、e lower line ofthe envelope over12 h and multiply by two. Express asamperes per hour drift.NOTE 1This method covers most cases of baseline drift. Occasion-ally, with sinusoidal baseline oscillations of lower frequency, a longermeasurement time should be used. This time must then be stated and thedri
26、ft value normalized to 1 h.6.1.3 In specifications giving the measured noise and driftof the FID, specify the test conditions in accordance with 7.2.4.7. Sensitivity (Response)7.1 Sensitivity (response) of the FID is the signal output perunit mass of a test substance in the carrier gas, in accordanc
27、ewith the following relationship:FIG. 1 Example of the FID Noise Level and Drift MeasurementE594 96 (2011)2S 5Aim(1)where:S = sensitivity (response), As/g,Ai= integrated peak area, As, andm = mass of the test substance in the carrier gas, g.7.2 Test Conditions:7.2.1 Normal butane is the preferred st
28、andard test substance.7.2.2 The measurement must be made within the linearrange of the detector.7.2.3 The measurement must be made at a signal level atleast 200 times greater than the noise level.7.2.4 The test substance and the conditions under which thedetector sensitivity is measured must be stat
29、ed. This willinclude, but not necessarily be limited to, the following:7.2.4.1 Type of detector,7.2.4.2 Detector geometry (for example, electrode to whichbias is applied),7.2.4.3 Carrier gas,7.2.4.4 Carrier gas flow rate (corrected to detector tempera-ture and fluid presssure),7.2.4.5 Make-up gas,7.
30、2.4.6 Make-up gas flow rate,7.2.4.7 Detector temperature,7.2.4.8 Detector polarizing voltage,7.2.4.9 Hydrogen flow rate,7.2.4.10 Air or oxygen flow rate,7.2.4.11 Method of measurement, and7.2.4.12 Electrometer range setting.7.3 Methods of Measurement:7.3.1 Sensitivity may be measured by any of three
31、 methods:7.3.1.1 Experimental decay with exponential dilution flask(7) (see 7.4).7.3.1.2 Utilizing the permeation device (8) under steady-state conditions (see 7.5).7.3.1.3 Utilizing Youngs apparatus (9) under dynamic con-ditions (see 7.6).7.3.2 Calculation of FID sensitivity by utilizing actualchro
32、matograms is not preferred because in such a case theamount of test substance at the detector may not be the same asthat introduced.7.4 Exponential Dilution Method:7.4.1 Purge a mixing vessel of known volume fitted with amagnetically driven stirrer with the carrier gas at a known rate.The effluent f
33、rom the flask is delivered directly to the detector.Introduce a measured quantity of the test substance into theflask to give an initial concentration, Co, of the test substancein the carrier gas, and simultaneously start a timer.7.4.2 Calculate the concentration of the test substance in thecarrier
34、gas at the outlet of the flask at any time as follows (seeAnnex A1):Cf5 Coexp 2Fft/Vf (2)where:Cf= concentration of the test substance at time t afterintroduction into the flask, g/mL,Co= initial concentration of the test compound introducedinto the flask, g/mL,Ff= carrier gas flow rate, corrected t
35、o flask temperature(see Annex A1), mL/min,t = time, min, andVf= volume of flask, mL.7.4.3 Calculate the sensitivity of the detector at any concen-tration as follows:S 560ECfFf(3)where:S = sensitivity, As/g,E = detector signal, A,Cf= concentration of the test substance at time, t, afterintroducton in
36、to the flask, g/mL, andFf= carrier gas flow rate, corrected to flask temperature(see Annex A1), mL/min.NOTE 2This method is subject to errors due to inaccuracies inmeasuring the flow rate and flask volume. An error of 1 % in themeasurement of either variable will propagate to 2 % over two decades in
37、concentration and to 6 % over six decades. Therefore, this method shouldnot be used for concentration ranges of more than two decades over asingle run.NOTE 3A temperature difference of 1C between flask and flow-measuring apparatus will, if uncompensated, introduce an error of13 %into the flow rate.N
38、OTE 4Extreme care should be taken to avoid unswept volumesbetween the flask and the detector, as these will introduce additional errorsinto the calculations.NOTE 5Flask volumes between 100 and 500 mL have been found themost convenient. Larger volumes should be avoided due to difficulties inobtaining
39、 efficient mixing and likelihood of temperature gradients.NOTE 6This method may not be used with supercritical-fluid mobilephases unless the flask is specifically designed and rated for the pressurein use.7.5 Method Utilizing Permeation Devices:7.5.1 Permeation devices consist of a volatile liquid e
40、n-closed in a container with a permeable wall. They provide lowconcentrations of vapor by diffusion of the vapor through thepermeable surface. The rate of diffusion for a given permeationdevice is dependent only on the temperature. The weight lossover a period of time is carefully and accurately det
41、ermined;thus, these devices have been proposed as primary standards.7.5.2 Accurately known permeation rates can be preparedby passing a gas over the previously calibrated permeationdevice at constant temperature. Knowing this permeation rate,Rt, the sensitivity of the detector can be obtained from t
42、hefollowing equation:S 560ERt(4)where:S = sensitivity, As/g,E = detector signal, A, andRt= permeation rate of a test substance from the perme-ation device, g/min.NOTE 7Permeation devices are suitable only for preparing relativelylow concentrations in the part-per-million range. In addition, only ali
43、mited range of linearity can be explored because it is experimentallydifficult to vary the permeation rate over an extended range. Thus, fordetectors of relatively low sensitivity or of higher noise levels, this methodE594 96 (2011)3may not satisfy the criteria given in 7.2.3, which requires that th
44、e signalbe at least 200 times greater than the noise level.Afurther limitation in theuse of permeation devices is the relatively slow equilibration of thepermeation rate, coupled with the life expectancy of a typical devicewhich is on the order of a few months.NOTE 8This method may not be used with
45、supercritical-fluid mobilephase. SC-CO2would adversly affect the permeation tube by eitherextracting the polymer or swelling the tube, resulting in a potential safetyhazard.7.6 Dynamic Method:7.6.1 In this method, inject a known quantity of test sub-stance into the flowing carrier gas stream. A leng
46、th of emptytubing or an empty high-pressure cell between the sampleinjection point and the detector permits the band to spread andbe detected as a Gaussian band. Then integrate the detectorsignal by any suitable method. This method has the advantagethat no special equipment or devices are required o
47、ther thanconventional chromatographic hardware.7.6.2 As an alternative to 7.6.1, an actual chromatogrammay be generated by substituting a column for the length ofempty tubing. This approach is not preferred because it iscommon for the sample to have adverse interaction with thecolumn. These problems
48、 can be minimized by using an inertstable liquid phase loaded sufficiently to overcome supportadsorption effects. Likewise a nonpolar sample will minimizethese adverse interactions. For example, a column preparedwith OV101 on Chromosorb G5with a n-octane sample shouldbest ensure that the entire samp
49、le introduced will reach thedetector.7.6.3 Calculate the sensitivity of the detector from the peakarea and the mass injected in accordance with 7.1.NOTE 9Care should be taken that the peak obtained is sufficientlywide so the accuracy of the integration is not limited by the response timeof the recording device.NOTE 10The approach given here should be used with caution as ithas not been applied over a wide concentration range.8. Minimum Detectability8.1 Minimum detectability is the mass flow rate of the testsubstance in the carrier gas th
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