ASTM E594-96(2001)
(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
SCOPE
1.1 This practice serves as a guide for 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 d-c 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 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.
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:E594–96(Reapproved 2001)
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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope E1449 Standard Guide for Supercritical Fluid Chromatog-
raphy Terms and Relationships
1.1 This practice serves as a guide for the testing of the
2.2 CGA Standards:
performance of a flame ionization detector (FID) used as the
CGAP-1 Safe Handling of Compressed Gases in Contain-
detection component of a gas or supercritical fluid (SF)
ers
chromatographic 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 d-c 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
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
E355 Practice for Gas Chromatography Terms and Rela-
actually exceed the short-term noise. Such fluctuations are
tionships
difficult to characterize and are not typically to be expected.
Theyareusuallycausedbyotherchromatographiccomponents
This recommended practice is under the jurisdiction ofASTM Committee E13 such as the column, system contaminants, and flow variations.
on Molecular Spectroscopy and is the direct responsibility of Subcommittee E13.19
These other noise contributions are not derived from the
on Chromatography.
detector itself and are difficult to quantitate in a general
Current edition approved April 10, 1996. Published June 1996. Originally
published as E594–77. The last previous edition E594–95.
The boldface numbers in parentheses refer to the list of references appended to
this recommended practice. Available from Compressed Gas Association, Inc., 1725 Jefferson Davis
Annual Book of ASTM Standards, Vol 3.06. Highway, Arlington, VA 22202-4100.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E594
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
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
bias is applied), measurementofeithervariablewillpropagateto2 %overtwodecadesin
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,
Annex A1): E = detector signal, A, and
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
LR 5 m˙ /D (6)
7.6 Dynamic Method:
max
7.6.1 In this method, inject a known quantity of test sub-
where:
stance into the flowing carrier gas stream. A length of empty
LR = linear range of the detector,
tubing or an empty high-pressure cell between the sample
m˙ = upperlimitoflinearityobtainedfromthelinearity
max
injection point and the detector permits the band to spread and
plot, g/s, and
be detected as a Gaussian band. Then integrate the detector
D = minimum detectability, g/s.
signal by any suitable method. This method has the advantage
If the linear range is expressed by this ratio, the minimum
that no special equipment or devices are required other than
detectability must also be stated.
conventional chromatographic hardware.
9.1.1.2 By giving the minimum detectability and the upper
7.6.2 As an alternative to 7.6.1, an actual chromatogram
−12 -
limit of linearity (for example, from 1 310 g/s to 1 310
may be generated by substituting a column for the length of
5g/s).
empty tubing. This approach is not preferred because it is
9.1.1.3 Bygivingthelinearityplotitself,withtheminimum
common for the sample to have adverse interaction with the
detectability indicated on the plot.
column. These problems can be minimized by using an inert
9.2 Method of Measurement:
stable liquid phase loaded sufficiently to overcome support
9.2.1 For the determination of the linear range of an FID,
adsorption effects. Likewise a nonpolar sample will minimize
use either the exponential decay or the dyn
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.