ASTM E594-96(2006)
(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’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, Refs. (5,6) 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 E 260 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 E 355.
1.5 For general information concerning the principles, construction, and operation of an FID, see Refs (1, 2, 3, 4).
1.6 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 .
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Designation:E594–96(Reapproved 2006)
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 E355 Practice for Gas Chromatography Terms and Rela-
tionships
1.1 This practice covers the testing of the performance of a
2.2 CGA Standards:
flame ionization detector (FID) used as the detection compo-
CGAP-1 Safe Handling of Compressed Gases in Contain-
nent of a gas or supercritical fluid (SF) chromatographic
ers
system.
CGAG-5.4 Standard for Hydrogen Piping Systems at
1.2 This recommended practice is directly applicable to an
Consumer Locations
FID that employs a hydrogen-air or hydrogen-oxygen flame
CGAP-9 The Inert Gases: Argon, Nitrogen and Helium
burner and a dc biased electrode system.
CGAV-7 Standard Method of Determining CylinderValve
1.3 This recommended practice covers the performance of
Outlet Connections for Industrial Gas Mixtures
the detector itself, independently of the chromatographic col-
CGAP-12 Safe Handling of Cryogenic Liquids
umn, the column-to-detector interface (if any), and other
HB-3 Handbook of Compressed Gases
systemcomponents,intermsthattheanalystcanusetopredict
overall system performance when the detector is made part of
3. Terminology
a complete chromatographic system.
3.1 Definitions:
1.4 For general gas chromatographic procedures, Practice
3.1.1 drift—the average slope of the baseline envelope
E260 should be followed except where specific changes are
expressed in amperes per hour as measured over ⁄2 h.
recommended herein for the use of an FID. For definitions of
3.1.2 noise (short-term)—the amplitude expressed in am-
gas chromatography and its various terms see Recommended
peres of the baseline envelope that includes all random
Practice E355.
variations of the detector signal of a frequency on the order of
1.5 For general information concerning the principles, con-
2 1 or more cycles per minute (see Fig. 1).
struction, and operation of an FID, see Refs (1, 2, 3, 4).
3.1.2.1 Discussion— Short-term noise corresponds to the
1.6 This standard does not purport to address all of the
observed noise only. The actual noise of the system may be
safety concerns, if any, associated with its use. It is the
larger or smaller than the observed value, depending upon the
responsibility of the user of this standard to establish appro-
method of data collection or signal monitoring from the
priate safety and health practices and determine the applica-
detector, since observed noise is a function of the frequency,
bility of regulatory limitations prior to use. For specific safety
speed of response, and the bandwidth of the electronic circuit
information, see Section 5.
measuring the detector signal.
2. Referenced Documents 3.1.3 other noise—Fluctuations of the baseline envelope of
3 a frequency less than 1 cycle per minute can occur in
2.1 ASTM Standards:
chromatographic systems.
E260 Practice for Packed Column Gas Chromatography
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
difficult to characterize and are not typically to be expected.
Spectroscopy and is the direct responsibility of Subcommittee E13.19 on Chroma-
Theyareusuallycausedbyotherchromatographiccomponents
tography.
such as the column, system contaminants, and flow variations.
Current edition approved March 1, 2006. Published March 2006. Originally
approved in 1977. The last previous edition approved in 2001 as E594–96(2001).
These other noise contributions are not derived from the
DOI: 10.1520/E0594-96R06.
detector itself and are difficult to quantitate in a general
The boldface numbers in parentheses refer to the list of references appended to
this recommended practice.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on Available from Compressed Gas Association (CGA), 1725 Jefferson Davis
the ASTM website. Hwy., Suite 1004, Arlington, VA 22202-4102.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E594–96 (2006)
FIG. 1 Example of the FID Noise Level and Drift Measurement.
manner.Itis,however,importantforthepracticingchromatog- Applicable CGA publications include CGAP-1, CGAG-5.4,
rapher to be aware of the occurrence of this type of noise CGAP-9, CGAV-7, CGAP-12, and HB-3.
contribution.
6. Noise and Drift
4. Significance and Use
6.1 Methods of Measurement:
4.1 Although it is possible to observe and measure each of 6.1.1 With the attenuator set at maximum sensitivity (mini-
mum attenuation), adjust the detector output with the “zero”’
the several characteristics of a detector under different and
uniqueconditions,itistheintentofthisrecommendedpractice controltonearmid-scaleontherecorder.Allowatleast ⁄2hof
that a complete set of detector specifications should be ob- baseline to be recorded. Draw two parallel lines to form an
tained at the same operating conditions, including geometry, envelopethatenclosestherandomexcursionsofafrequencyof
flow rates, and temperatures. It should be noted that to specify approximately 1 cycle per minute or more. Measure the
a detector’s capability completely, its performance should be distance between the parallel lines at any particular time.
measured at several sets of conditions within the useful range Express the value as amperes of noise.
of the detector. The terms and tests described in this recom- 6.1.2 Measurethenetchangeinamperesofthelowerlineof
mended practice are sufficiently general so that they may be the envelope over ⁄2 h and multiply by two. Express as
used at whatever conditions may be chosen for other reasons. amperes per hour drift.
4.2 The FID is generally only used with non-ionizable
NOTE 1—This method covers most cases of baseline drift. Occasion-
supercritical fluids as the mobile phase. Therefore, this stan-
ally, with sinusoidal baseline oscillations of lower frequency, a longer
dard does not include the use of modifiers in the supercritical
measurement time should be used. This time must then be stated and the
fluid. drift value normalized to 1 h.
4.3 Linearity and speed of response of the recording system
6.1.3 In specifications giving the measured noise and drift
orotherdataacquisitiondeviceusedshouldbesuchthatitdoes
oftheFID,specifythetestconditionsinaccordancewith7.2.4.
not distort or otherwise interfere with the performance of the
detector. Effective recorder response, Refs. (5,6) in particular,
7. Sensitivity (Response)
should be sufficiently fast so that it can be neglected in
7.1 Sensitivity(response)oftheFIDisthesignaloutputper
sensitivity of measurements. If additional amplifiers are used
unit mass of a test substance in the carrier gas, in accordance
between the detector and the final readout device, their
with the following relationship:
characteristics should also first be established.
A
i
S 5 (1)
m
5. Hazards
5.1 Gas Handling Safety—The safe handling of com-
where:
pressed gases and cryogenic liquids for use in chromatography
S = sensitivity (response), A·s/g,
is the responsibility of every laboratory. The Compressed Gas A = integrated peak area, A·s, and
i
Association,(CGA),amembergroupofspecialtyandbulkgas m = mass of the test substance in the carrier gas, g.
suppliers, publishes the following guidelines to assist the 7.2 Test Conditions:
laboratory chemist to establish a safe work environment. 7.2.1 Normalbutaneisthepreferredstandardtestsubstance.
E594–96 (2006)
7.2.2 The measurement must be made within the linear
where:
range of the detector.
S = sensitivity, A·s/g,
7.2.3 The measurement must be made at a signal level at E = detector signal, A,
least 200 times greater than the noise level. C = concentration of the test substance at time, t, after
f
introducton into the flask, g/mL, and
7.2.4 The test substance and the conditions under which the
F = carrier gas flow rate, corrected to flask temperature
detector sensitivity is measured must be stated. This will f
(see Annex A1), mL/min.
include, but not necessarily be limited to, the following:
7.2.4.1 Type of detector,
NOTE 2—This method is subject to errors due to inaccuracies in
7.2.4.2 Detector geometry (for example, electrode to which
measuring the flow rate and flask volume. An error of 1 % in the
measurementofeithervariablewillpropagateto2 %overtwodecadesin
bias is applied),
concentrationandto6 %oversixdecades.Therefore,thismethodshould
7.2.4.3 Carrier gas,
not be used for concentration ranges of more than two decades over a
7.2.4.4 Carrier gas flow rate (corrected to detector tempera-
single run.
ture and fluid presssure),
NOTE 3—A temperature difference of 1 C between flask and flow-
7.2.4.5 Make-up gas,
measuring apparatus will, if uncompensated, introduce an error of ⁄3 %
7.2.4.6 Make-up gas flow rate,
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
into the calculations.
7.2.4.9 Hydrogen flow rate,
NOTE 5—Flask volumes between 100 and 500 mLhave been found the
7.2.4.10 Air or oxygen flow rate,
most convenient. Larger volumes should be avoided due to difficulties in
7.2.4.11 Method of measurement, and
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
R
t
flask to give an initial concentration, C , of the test substance
o
(4)
in the carrier gas, and simultaneously start a timer.
7.4.2 Calculatetheconcentrationofthetestsubstanceinthe
where:
carrier gas at the outlet of the flask at any time as follows (see
S = sensitivity, A·s/g,
E = detector signal, A, and
Annex A1):
R = permeation rate of a test substance from the perme-
t
C 5 C exp [2F t/V ] (2)
f o f f
ation device, g/min.
where:
NOTE 7—Permeation devices are suitable only for preparing relatively
C = concentration of the test substance at time t after
f
low concentrations in the part-per-million range. In addition, only a
introduction into the flask, g/mL,
limited range of linearity can be explored because it is experimentally
C = initial concentration of the test compound introduced
o difficult to vary the permeation rate over an extended range. Thus, for
into the flask, g/mL, detectorsofrelativelylowsensitivityorofhighernoiselevels,thismethod
F = carrier gas flow rate, corrected to flask temperature may not satisfy the criteria given in 4.2.3, which requires that the signal
f
beatleast200timesgreaterthanthenoiselevel.Afurtherlimitationinthe
(see Annex A1), mL/min,
use of permeation devices is the relatively slow equilibration of the
t = time, min, and
permeation rate, coupled with the life expectancy of a typical device
V = volume of flask, mL.
f
which is on the order of a few months.
7.4.3 Calculatethesensitivityofthedetectoratanyconcen-
NOTE 8—This method may not be used with supercritical-fluid mobile
tration as follows:
phase. SC-CO would adversly affect the permeation tube by either
60E
extracting the polymer or swelling the tube, resulting in a potential safety
S 5 (3)
C F hazard.
f f
E594–96 (2006)
7.6 Dynamic Method: 9.1.1.1 As the ratio of the upper limit of linearity, obtained
7.6.1 In this method, inject a known quantity of test sub- from the linearity plot to the minimum detectability, both
stance into the flowing carrier gas stream. A length of empty measured for the same test substances as follows:
tubing or an empty high-pressure cell between the sample
LR 5 m˙ /D (6)
max
injection point and the detector permits the band to spread and
where:
be detected as a Gaussian band. Then integrate the detector
LR = linear range of the detector,
signal by any suitable method. This method has the advantage
m˙ = upperlimitoflinearityobtainedfromthelinearity
max
that no special equipment or devices are required other than
plot, g/s, and
conventional chromatographic hardware.
D = minimum detectability, g/s.
7.6.2 As an alternative to 7.6.1, an actual chromatogram
If the linear range is expressed by this ratio, the minimum
may be generated by substituting a column for the length of
detectability must also be stated.
empty tubing. This approach is not preferred because it is
9.1.1.2 By giving the minimum detectability and the upper
common for the sample to have adverse interaction with the
−12 -
limit of linearity (for example, from 1 310 g/s to 1 310
column. These problems can be minimized by using an inert
...
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