ASTM E594-96(2011)
(Practice)Standard Practice for Testing Flame Ionization Detectors Used in Gas or Supercritical Fluid Chromatography
Standard Practice for Testing Flame Ionization Detectors Used in Gas or Supercritical Fluid Chromatography
SIGNIFICANCE AND USE
Although it is possible to observe and measure each of the several characteristics of a detector under different and unique conditions, it is the intent of this recommended practice that a complete set of detector specifications should be obtained at the same operating conditions, including geometry, flow rates, and temperatures. It should be noted that to specify a detector's capability completely, its performance should be measured at several sets of conditions within the useful range of the detector. The terms and tests described in this recommended practice are sufficiently general so that they may be used at whatever conditions may be chosen for other reasons.
The FID is generally only used with non-ionizable supercritical fluids as the mobile phase. Therefore, this standard does not include the use of modifiers in the supercritical fluid.
Linearity and speed of response of the recording system or other data acquisition device used should be such that it does not distort or otherwise interfere with the performance of the detector. Effective recorder response, Bonsall (5) and McWilliam (6), in particular, should be sufficiently fast so that it can be neglected in sensitivity of measurements. If additional amplifiers are used between the detector and the final readout device, their characteristics should also first be established.
SCOPE
1.1 This practice covers the testing of the performance of a flame ionization detector (FID) used as the detection component of a gas or supercritical fluid (SF) chromatographic system.
1.2 This recommended practice is directly applicable to an FID that employs a hydrogen-air or hydrogen-oxygen flame burner and a dc biased electrode system.
1.3 This recommended practice covers the performance of the detector itself, independently of the chromatographic column, the column-to-detector interface (if any), and other system components, in terms that the analyst can use to predict overall system performance when the detector is made part of a complete chromatographic system.
1.4 For general gas chromatographic procedures, Practice E260 should be followed except where specific changes are recommended herein for the use of an FID. For definitions of gas chromatography and its various terms see recommended Practice E355.
1.5 For general information concerning the principles, construction, and operation of an FID, see Refs (1, 2, 3, 4).
1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For specific safety information, see Section 5.
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Designation: E594 − 96 (Reapproved 2011)
Standard Practice for
Testing Flame Ionization Detectors Used in Gas or
Supercritical Fluid Chromatography
This standard is issued under the fixed designation E594; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
2.1 ASTM Standards:
1.1 This practice covers the testing of the performance of a
E260Practice for Packed Column Gas Chromatography
flame ionization detector (FID) used as the detection compo-
E355PracticeforGasChromatographyTermsandRelation-
nent of a gas or supercritical fluid (SF) chromatographic
ships
system.
2.2 CGA Standards:
1.2 This recommended practice is directly applicable to an
CGAP-1 Safe Handling of Compressed Gases in Contain-
FID that employs a hydrogen-air or hydrogen-oxygen flame
ers
burner and a dc biased electrode system.
CGAG-5.4 Standard for Hydrogen Piping Systems at
Consumer Locations
1.3 This recommended practice covers the performance of
CGAP-9The Inert Gases: Argon, Nitrogen and Helium
the detector itself, independently of the chromatographic
CGAV-7Standard Method of Determining Cylinder Valve
column, the column-to-detector interface (if any), and other
Outlet Connections for Industrial Gas Mixtures
systemcomponents,intermsthattheanalystcanusetopredict
CGAP-12Safe Handling of Cryogenic Liquids
overall system performance when the detector is made part of
HB-3Handbook of Compressed Gases
a complete chromatographic system.
3. Terminology
1.4 For general gas chromatographic procedures, Practice
3.1 Definitions:
E260 should be followed except where specific changes are
3.1.1 drift—the average slope of the baseline envelope
recommended herein for the use of an FID. For definitions of
expressed in amperes per hour as measured over ⁄2 h.
gas chromatography and its various terms see recommended
Practice E355.
3.1.2 noise (short-term)—the amplitude expressed in am-
peres of the baseline envelope that includes all random
1.5 For general information concerning the principles,
variations of the detector signal of a frequency on the order of
construction, and operation of an FID, see Refs (1, 2, 3, 4).
1 or more cycles per minute (see Fig. 1).
1.6 The values stated in SI units are to be regarded as 3.1.2.1 Discussion—Short-term noise corresponds to the
observed noise only. The actual noise of the system may be
standard. No other units of measurement are included in this
standard. larger or smaller than the observed value, depending upon the
method of data collection or signal monitoring from the
1.7 This standard does not purport to address all of the
detector, since observed noise is a function of the frequency,
safety concerns, if any, associated with its use. It is the
speed of response, and the bandwidth of the electronic circuit
responsibility of the user of this standard to establish appro-
measuring the detector signal.
priate safety and health practices and determine the applica-
3.1.3 other noise—Fluctuations of the baseline envelope of
bility of regulatory limitations prior to use. For specific safety
a frequency less than 1 cycle per minute can occur in
information, see Section 5.
chromatographic systems.
3.1.4 Discussion—The amplitude of these fluctuations may
actually exceed the short-term noise. Such fluctuations are
This practice is under the jurisdiction ofASTM Committee E13 on Molecular
Spectroscopy and Separation Science and is the direct responsibility of Subcom-
mittee E13.19 on Separation Science. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Nov. 1, 2011. Published December 2011. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 1977. The last previous edition approved in 2006 as E594–96(2011). Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/E0594-96R11. the ASTM website.
The boldface numbers in parentheses refer to the list of references appended to Available from Compressed Gas Association (CGA), 4221 Walney Rd., 5th
this recommended practice. Floor, Chantilly, VA 20151-2923, http://www.cganet.com.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E594 − 96 (2011)
FIG. 1 Example of the FID Noise Level and Drift Measurement
difficult to characterize and are not typically to be expected. responsibility of every laboratory. The CGA, a member group
Theyareusuallycausedbyotherchromatographiccomponents of specialty and bulk gas suppliers, publishes the following
such as the column, system contaminants, and flow variations. guidelines to assist the laboratory chemist to establish a safe
These other noise contributions are not derived from the work environment. Applicable CGA publications include
detector itself and are difficult to quantitate in a general CGAP-1, CGAG-5.4, CGAP-9, CGAV-7, CGAP-12, and
manner.Itis,however,importantforthepracticingchromatog- HB-3.
rapher to be aware of the occurrence of this type of noise
6. Noise and Drift
contribution.
6.1 Methods of Measurement:
4. Significance and Use
6.1.1 With the attenuator set at maximum sensitivity (mini-
4.1 Although it is possible to observe and measure each of
mum attenuation), adjust the detector output with the “zero”
the several characteristics of a detector under different and
controltonearmid-scaleontherecorder.Allowatleast ⁄2hof
uniqueconditions,itistheintentofthisrecommendedpractice
baseline to be recorded. Draw two parallel lines to form an
that a complete set of detector specifications should be ob-
envelopethatenclosestherandomexcursionsofafrequencyof
tained at the same operating conditions, including geometry,
approximately 1 cycle per minute or more. Measure the
flow rates, and temperatures. It should be noted that to specify
distance between the parallel lines at any particular time.
a detector’s capability completely, its performance should be
Express the value as amperes of noise.
measured at several sets of conditions within the useful range
6.1.2 Measurethenetchangeinamperesofthelowerlineof
of the detector. The terms and tests described in this recom-
the envelope over ⁄2 h and multiply by two. Express as
mended practice are sufficiently general so that they may be
amperes per hour drift.
used at whatever conditions may be chosen for other reasons.
NOTE1—Thismethodcoversmostcasesofbaselinedrift.Occasionally,
4.2 The FID is generally only used with non-ionizable with sinusoidal baseline oscillations of lower frequency, a longer mea-
surement time should be used. This time must then be stated and the drift
supercritical fluids as the mobile phase. Therefore, this stan-
value normalized to 1 h.
dard does not include the use of modifiers in the supercritical
6.1.3 In specifications giving the measured noise and drift
fluid.
oftheFID,specifythetestconditionsinaccordancewith7.2.4.
4.3 Linearity and speed of response of the recording system
orotherdataacquisitiondeviceusedshouldbesuchthatitdoes
7. Sensitivity (Response)
not distort or otherwise interfere with the performance of the
7.1 Sensitivity(response)oftheFIDisthesignaloutputper
5) and McWil-
detector. Effective recorder response, Bonsall (
unit mass of a test substance in the carrier gas, in accordance
liam (6), in particular, should be sufficiently fast so that it can
with the following relationship:
be neglected in sensitivity of measurements. If additional
A
amplifiers are used between the detector and the final readout
i
S 5 (1)
m
device, their characteristics should also first be established.
where:
5. Hazards
S = sensitivity (response), A·s/g,
5.1 Gas Handling Safety—The safe handling of compressed
A = integrated peak area, A·s, and
i
gases and cryogenic liquids for use in chromtography is the
E594 − 96 (2011)
7.4.3 Calculatethesensitivityofthedetectoratanyconcen-
m = mass of the test substance in the carrier gas, g.
tration as follows:
7.2 Test Conditions:
60E
7.2.1 Normalbutaneisthepreferredstandardtestsubstance.
S 5 (3)
C F
7.2.2 The measurement must be made within the linear f f
range of the detector.
where:
7.2.3 The measurement must be made at a signal level at
S = sensitivity, A·s/g,
least 200 times greater than the noise level.
E = detector signal, A,
7.2.4 The test substance and the conditions under which the
C = concentration of the test substance at time, t, after
f
detector sensitivity is measured must be stated. This will
introducton into the flask, g/mL, and
include, but not necessarily be limited to, the following:
F = carriergasflowrate,correctedtoflasktemperature(see
f
7.2.4.1 Type of detector,
Annex A1), mL/min.
7.2.4.2 Detector geometry (for example, electrode to which
NOTE 2—This method is subject to errors due to inaccuracies in
bias is applied), measuring the flow rate and flask volume. An error of 1% in the
measurement of either variable will propagate to 2% over two decades in
7.2.4.3 Carrier gas,
concentration and to 6% over six decades.Therefore, this method should
7.2.4.4 Carrier gas flow rate (corrected to detector tempera-
not be used for concentration ranges of more than two decades over a
ture and fluid presssure),
single run.
7.2.4.5 Make-up gas,
NOTE 3—A temperature difference of 1°C between flask and flow-
7.2.4.6 Make-up gas flow rate, measuring apparatus will, if uncompensated, introduce an error of ⁄3 %
into the flow rate.
7.2.4.7 Detector temperature,
NOTE 4—Extreme care should be taken to avoid unswept volumes
7.2.4.8 Detector polarizing voltage,
betweentheflaskandthedetector,asthesewillintroduceadditionalerrors
7.2.4.9 Hydrogen flow rate,
into the calculations.
7.2.4.10 Air or oxygen flow rate,
NOTE 5—Flask volumes between 100 and 500 mLhave been found the
7.2.4.11 Method of measurement, and
most convenient. Larger volumes should be avoided due to difficulties in
obtaining efficient mixing and likelihood of temperature gradients.
7.2.4.12 Electrometer range setting.
NOTE 6—This method may not be used with supercritical-fluid mobile
7.3 Methods of Measurement:
phases unless the flask is specifically designed and rated for the pressure
7.3.1 Sensitivitymaybemeasuredbyanyofthreemethods: in use.
7.3.1.1 Experimental decay with exponential dilution flask
7.5 Method Utilizing Permeation Devices:
(7) (see 7.4).
7.5.1 Permeation devices consist of a volatile liquid en-
7.3.1.2 Utilizing the permeation device (8) under steady-
closed in a container with a permeable wall.They provide low
state conditions (see 7.5).
concentrations of vapor by diffusion of the vapor through the
7.3.1.3 UtilizingYoung’s apparatus (9) under dynamic con-
permeablesurface.Therateofdiffusionforagivenpermeation
ditions (see 7.6).
device is dependent only on the temperature. The weight loss
7.3.2 Calculation of FID sensitivity by utilizing actual
over a period of time is carefully and accurately determined;
chromatograms is not preferred because in such a case the
thus, these devices have been proposed as primary standards.
amountoftestsubstanceatthedetectormaynotbethesameas
7.5.2 Accurately known permeation rates can be prepared
that introduced.
by passing a gas over the previously calibrated permeation
7.4 Exponential Dilution Method:
device at constant temperature. Knowing this permeation rate,
7.4.1 Purge a mixing vessel of known volume fitted with a
R, the sensitivity of the detector can be obtained from the
t
magneticallydrivenstirrerwiththecarriergasataknownrate.
following equation:
The effluent from the flask is delivered directly to the detector.
60E
Introduce a measured quantity of the test substance into the
S 5 (4)
R
t
flask to give an initial concentration, C , of the test substance
o
in the carrier gas, and simultaneously start a timer. where:
7.4.2 Calculatetheconcentrationofthetestsubstanceinthe
S = sensitivity, A·s/g,
carrier gas at the outlet of the flask at any time as follows (see
E = detector signal, A, and
Annex A1): R = permeationrateofatestsubstancefromthepermeation
t
device, g/min.
C 5 C exp 2F t/V (2)
@ #
f o f f
NOTE 7—Permeation devices are suitable only for preparing relatively
where: low concentrations in the part-per-million range. In addition, only a
limited range of linearity can be explored because it is experimentally
C = concentration of the test substance at time t after
f
difficult to vary the permeation rate over an extended range. Thus, for
introduction into the flask, g/mL,
detectorsofrelativelylowsensitivityorofhighernoiselevels,thismethod
C = initial concentration of the test compound introduced
o may not satisfy the criteria given in 7.2.3, which requires that the signal
into the flask, g/mL,
beatleast200timesgreaterthanthenoiselevel.Afurtherlimitationinthe
use of permeation devices is the relatively slow equilibration of the
F = carriergasflowrate,correctedtoflasktemperature(see
f
permeation rate, coupled with the life expectancy of a typical device
Annex A1), mL/min,
which is on the order of a few months.
t = time, min, and
NOTE 8—This method may not be used with supercritical-fluid mobile
V = volume of flask, mL.
f
phase. SC-CO would adversly affect the permeation tube by either
E594 − 96 (2011)
extracting the polymer or swelling the tube, resulting in a potential safety
sensitivity of the detector is constant to within 5 % as
hazard.
determined from the linearity plot specified in 9.2.2.
7.6 Dynamic Method: 9.1.1 The linear range may be expressed in three different
7.6.1 In this method, inject a known quantity of test sub- ways:
stance into the flowing carrier gas stream. A length of empty 9.1.1.1 As the ratio of the upper limit of linearity, obtained
tubing or an empty high-pressure cell between the sample from the linearity plot to the minimum detectability, both
injection point and the detector permits the band to spread and measured for the same test substances as follows:
be detected as a Gaussian band. Then integrate the detector
LR 5 m˙ /D (6)
max
signal by any suitable method. This method has the advantage
where:
that no special equipment or devices are required other than
conventional chromatographic hardware. LR = linear range of the detector,
m˙ = upper limit of linearity obtained from the linearity
7.6.2 As an alternative to 7.6.1, an actual chromatogram
max
plot, g/s, and
may be generated by substituting a column for the length of
D = minimum detectability, g/s.
empty tubing. This approach is not preferred because it is
common for
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