1、Designation: E 594 96 (Reapproved 2006)Standard Practice forTesting Flame Ionization Detectors Used in Gas orSupercritical Fluid Chromatography1This standard is issued under the fixed designation E 594; the number immediately following the designation indicates the year oforiginal adoption or, in th
2、e 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 covers the testing of the performance of aflame ionization detector (FI
3、D) 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 performanc
4、e ofthe 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
5、chromatographic procedures, PracticeE 260 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 E 355.1.5 For general information concerning the principles, con-struction, and o
6、peration of an FID, see Refs (1, 2, 3, 4).21.6 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 and health practices and determine the applica-bility of regulato
7、ry limitations prior to use. For specific safetyinformation, see Section 5.2. Referenced Documents2.1 ASTM Standards:3E 260 Practice for Packed Column Gas ChromatographyE 355 Practice for Gas Chromatography Terms and Rela-tionships2.2 CGA Standards:CGA P-1 Safe Handling of Compressed Gases in Contai
8、n-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 ValveOutlet Connections for Industrial Gas Mixtures4CGA P-12 Safe Handling of Cryogenic Liquids4HB-3 Handbook of Compressed Ga
9、ses43. 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 expressed in am-peres of the baseline envelope that includes all randomvariations of the detector signal of a frequency on t
10、he order of1 or more cycles per minute (see Fig. 1).3.1.2.1 Discussion Short-term noise corresponds to theobserved noise only. The actual noise of the system may belarger or smaller than the observed value, depending upon themethod of data collection or signal monitoring from thedetector, since obse
11、rved noise is a function of the frequency,speed of response, and the bandwidth of the electronic circuitmeasuring the detector signal.3.1.3 other noiseFluctuations of the baseline envelope ofa frequency less than 1 cycle per minute can occur inchromatographic systems.3.1.4 DiscussionThe amplitude of
12、 these fluctuations mayactually exceed the short-term noise. Such fluctuations aredifficult to characterize and are not typically to be expected.They are usually caused by other chromatographic componentssuch as the column, system contaminants, and flow variations.These other noise contributions are
13、 not derived from thedetector itself and are difficult to quantitate in a general1This practice is under the jurisdiction of ASTM Committee E13 on MolecularSpectroscopy and is the direct responsibility of Subcommittee E13.19 on Chroma-tography.Current edition approved March 1, 2006. Published March
14、2006. Originallyapproved in 1977. The last previous edition approved in 2001 as E 594 96 (2001).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 Serv
15、ice at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.4Available from Compressed Gas Association (CGA), 1725 Jefferson DavisHwy., Suite 1004, Arlington, VA 22202-4102.1Copyright ASTM International, 100 Barr Harbor
16、 Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.manner. It is, however, important for the practicing chromatog-rapher 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 char
17、acteristics of a detector under different andunique conditions, it is the intent of this recommended practicethat a complete set of detector specifications should be ob-tained at the same operating conditions, including geometry,flow rates, and temperatures. It should be noted that to specifya detec
18、tors capability completely, its performance should bemeasured at several sets of conditions within the useful rangeof the detector. The 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
19、The FID is generally only used with non-ionizablesupercritical fluids as the mobile phase. Therefore, this stan-dard does not include 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
20、 doesnot distort or otherwise interfere with the performance of thedetector. Effective recorder response, Refs. (5,6) in particular,should be sufficiently fast so that it can be neglected insensitivity of measurements. If additional amplifiers are usedbetween the detector and the final readout devic
21、e, theircharacteristics should also first be established.5. Hazards5.1 Gas Handling SafetyThe safe handling of com-pressed gases and cryogenic liquids for use in chromatographyis the responsibility of every laboratory. The Compressed GasAssociation, (CGA), a member group of specialty and bulk gassup
22、pliers, publishes the following guidelines to assist thelaboratory chemist to establish a safe work environment.Applicable CGA publications include CGA P-1, CGA G-5.4,CGA P-9, CGA V-7, CGA P-12, and HB-3.6. Noise and Drift6.1 Methods of Measurement:6.1.1 With the attenuator set at maximum sensitivit
23、y (mini-mum attenuation), adjust the detector output with the “zero”control to near mid-scale on the recorder.Allow at least12 hofbaseline to be recorded. Draw two parallel lines to form anenvelope that encloses the random excursions of a frequency ofapproximately 1 cycle per minute or more. Measure
24、 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 the 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
25、-ally, with sinusoidal baseline oscillations of lower frequency, a longermeasurement time should be used. This time must then be stated and thedrift 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.
26、Sensitivity (Response)7.1 Sensitivity (response) of the FID is the signal output perunit mass of a test substance in the carrier gas, in accordancewith the following relationship:S 5Aim(1)where:S = sensitivity (response), As/g,Ai= integrated peak area, As, andm = mass of the test substance in the ca
27、rrier gas, g.7.2 Test Conditions:7.2.1 Normal butane is the preferred standard test substance.FIG. 1 Example of the FID Noise Level and Drift Measurement.E 594 96 (2006)27.2.2 The measurement must be made within the linearrange of the detector.7.2.3 The measurement must be made at a signal level atl
28、east 200 times greater than the noise level.7.2.4 The test substance and the conditions under which thedetector sensitivity is measured must be stated. 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 whi
29、chbias 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,7.2.4.6 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
30、,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 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 conditio
31、ns (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 actualchromatograms 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 Dilu
32、tion 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 from the flask is delivered directly to the detector.Introduce a measured quantity of the test substance into theflask to give an initial concentration,
33、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 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 afterin
34、troduction into the flask, g/mL,Co= initial concentration of the test compound introducedinto the flask, g/mL,Ff= carrier gas flow rate, corrected to 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-tratio
35、n as follows:S 560ECfFf(3)where:S = sensitivity, As/g,E = detector signal, A,Cf= concentration of the test substance at time, t, afterintroducton into 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 ina
36、ccuracies inmeasuring the flow rate and flask volume. An error of 1 % in themeasurement of either variable will propagate to 2 % over two decades inconcentration and to 6 % over six decades. Therefore, this method shouldnot be used for concentration ranges of more than two decades over asingle run.N
37、OTE 3A temperature difference of 1 C between flask and flow-measuring apparatus will, if uncompensated, introduce an error of13 %into the flow rate.NOTE 4Extreme care should be taken to avoid unswept volumesbetween the flask and the detector, as these will introduce additional errorsinto the calcula
38、tions.NOTE 5Flask volumes between 100 and 500 mL have been found themost convenient. Larger volumes should be avoided due to difficulties inobtaining efficient mixing and likelihood of temperature gradients.NOTE 6This method may not be used with supercritical-fluid mobilephases unless the flask is s
39、pecifically designed and rated for the pressurein use.7.5 Method Utilizing Permeation Devices:7.5.1 Permeation devices consist of a volatile liquid en-closed in a container with a permeable wall. They provide lowconcentrations of vapor by diffusion of the vapor through thepermeable surface. The rate
40、 of diffusion for a given permeationdevice is dependent only on the temperature. The weight lossover a period of time is carefully and accurately determined;thus, these devices have been proposed as primary standards.7.5.2 Accurately known permeation rates can be preparedby passing a gas over the pr
41、eviously calibrated permeationdevice at constant temperature. Knowing this permeation rate,Rt, the sensitivity of the detector can be obtained from thefollowing equation:S 560ERt(4)where:S = sensitivity, As/g,E = detector signal, A, andRt= permeation rate of a test substance from the perme-ation dev
42、ice, g/min.NOTE 7Permeation devices are suitable only for preparing relativelylow concentrations in the part-per-million range. In addition, only alimited range of linearity can be explored because it is experimentallydifficult to vary the permeation rate over an extended range. Thus, fordetectors o
43、f relatively low sensitivity or of higher noise levels, this methodmay not satisfy the criteria given in 4.2.3, which requires that the signalbe at least 200 times greater than the noise level.Afurther limitation in theuse of permeation devices is the relatively slow equilibration of thepermeation r
44、ate, 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 supercritical-fluid mobilephase. SC-CO2would adversly affect the permeation tube by eitherextracting the polymer or swelling the tube, resulting in a potential safety
45、hazard.E 594 96 (2006)37.6 Dynamic Method:7.6.1 In this method, inject a known quantity of test sub-stance into the flowing carrier gas stream. A length of emptytubing or an empty high-pressure cell between the sampleinjection point and the detector permits the band to spread andbe detected as a Gau
46、ssian band. Then integrate the detectorsignal by any suitable method. This method has the advantagethat no special equipment or devices are required other thanconventional chromatographic hardware.7.6.2 As an alternative to 7.6.1, an actual chromatogrammay be generated by substituting a column for t
47、he length ofempty tubing. This approach is not preferred because it iscommon for the sample to have adverse interaction with thecolumn. These problems can be minimized by using an inertstable liquid phase loaded sufficiently to overcome supportadsorption effects. Likewise a nonpolar sample will mini
48、mizethese adverse interactions. For example, a column preparedwith OV101 on Chromosorb G5with a n-octane sample shouldbest ensure that the entire sample 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.NO
49、TE 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 that gives a detector signal equal totwice the noise level and is calculated from the measuredsensitivity and noise level values as follows:D 5 2N/S (5)where:D = minimu
