An American National Standard

Designation: D 3606 – 04

Standard Test Method for

Determination of Benzene and Toluene in Finished Motor
and Aviation Gasoline by Gas Chromatography1
This standard is issued under the fixed designation D 3606; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.

1. Scope* E 1044 Specification for Glass Serological Pipets (General

1.1 This test method covers the determination of benzene Purpose and Kahn)
and toluene in finished motor and aviation gasolines by gas E 1293 Specification for Glass Measuring Pipets
chromatography. 3. Summary of Test Method
1.2 Benzene can be determined between the levels of 0.1
and 5 volume % and toluene can be determined between the 3.1 An internal standard, methyl ethyl ketone (MEK), is
levels of 2 and 20 volume %. added to the sample which is then introduced into a gas
1.3 The precision for this test method was determined using chromatograph equipped with two columns connected in
conventional gasoline as well as gasolines containing oxygen- series. The sample passes first through a column packed with a
ates (ethers such as methyl tert-butyl ether, ethyl tert- nonpolar phase such as dimethylpolysiloxane (8.1.1) which
butylether and tert-amylmethylether). separates the components according to boiling point. After
1.4 It has been determined that this test method is not octane has eluted, the flow through the nonpolar column is
applicable to gasolines containing ethanol. Methanol may also reversed, flushing out the components heavier than octane. The
cause interference. octane and lighter components then pass through a column
1.5 The values stated in SI units are to be regarded as the packed with a highly polar phase such as 1,2,3-tris(2-
standard. The values given in parentheses are for information cyanoethoxy) propane (8.1.2) which separates the aromatic and
only. nonaromatic compounds. The eluted components are detected
1.6 This standard does not purport to address all of the by a thermal conductivity detector. The detector response is
safety concerns, if any, associated with its use. It is the recorded, the peak areas are measured, and the concentration of
responsibility of the user of this standard to establish appro- each component is calculated with reference to the internal
priate safety and health practices and determine the applica- standard.
bility of regulatory limitations prior to use. 4. Significance and Use
2. Referenced Documents 4.1 Benzene is classed as a toxic material. A knowledge of
2.1 ASTM Standards: the concentration of this compound can be an aid in evaluating
D 4057 Practice for Manual Sampling of Petroleum and the possible health hazard to persons handling and using the
Petroleum Products2 gasoline. This test method is not intended to evaluate such
E 694 Specification for Laboratory Glass Volumetric Appa- hazards.
ratus 5. Apparatus
E 969 Specification for Glass Volumetric (Transfer) Pipets
5.1 Chromatograph—Any chromatographic instrument that
has a backflush system and thermal conductivity detector, and
1
This test method is under the jurisdiction of ASTM Committee D02 on that can be operated at the conditions given in Table 1, can be
Petroleum Products and Lubricants and is the direct responsibility of Subcommittee employed. Two backflush systems are shown. Fig. 1 is a
D02.04 on Hydrocarbon Analysis.
Current edition approved May 1, 2004. Published May 2004. Originally
pressure system and Fig. 2 is a switching valve system. Either
approved in 1977. Last previous edition approved in 1999 as D 3606–99. one can be used.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or 5.2 Columns:
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
the ASTM website.

*A Summary of Changes section appears at the end of this standard.

Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.

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 D 3606 – 04
TABLE 1 Instrument Parameters 5.13 Burets, automatic, with integral reservoir, 25-mL ca-
Detector thermal conductivity pacity.
Columns: two, stainless steel
Length, m (A) 0.8; (B) 4.6
Outside diameter, mm 3.2
6. Materials
Stationary phase (A) dimethylpolysiloxane, 10 mass % 6.1 Carrier Gas—Helium, 99.99 % pure. (Warning—
(B) TCEP, 20 mass %
Support (A) Chromosorb W, 60 to 80-mesh
Compressed gas under high pressure.)
(B) Chromosorb P, 80 to 100-mesh 6.2 Support—Crushed firebrick, acid-washed, 60 to 80-
Reference column Any column or restriction may be mesh and 80 to 100-mesh.
used.
Temperature:
6.3 Liquid Phases—1,2,3-Tris(2-cyanoethoxy) propane
Sample inlet system, °C 200 (TCEP) and methyl silicone.3
Detector, °C 200 6.4 Solvents:
Column, °C 145
Carrier Gas: helium
6.4.1 Methanol, reagent grade. (Warning—Flammable. Va-
Linear Gas Rate, cm/s 6 por harmful. Can be fatal or cause blindness if swallowed or
Volume flow rate, cm3/min approx 30 inhaled.)
Column head pressure, kPa (psi) approx 200 (30)
Recorder range, mV 0 to 1
6.4.2 Chloroform, reagent grade. (Warning—Can be fatal if
Chart speed, cm/min 1 swallowed. Harmful if inhaled.)
Sample size, µL 2 6.4.3 Methylene Chloride, for cleaning columns.
Total cycle time, min 8
Backflush, min approximately 0.75A
(Warning—Harmful if inhaled. High concentrations can cause
A
unconsciousness or death.)
This back flush time must be determined for each column system.
6.4.4 Acetone, for cleaning columns. (Warning—
Extremely flammable. Vapors can cause flash fires.)
5.2.1 Column A—One 0.8-m (2.5-ft) by 3.2-mm (1⁄8-in.) 6.5 Internal Standard:
outside diameter stainless steel column packed with 10 mass % 6.5.1 Methyl Ethyl Ketone (MEK), 99.5% minimum purity.
dimethylpolysiloxane (for example, OV-101) on Chromosorb (Warning—Flammable. Vapor can be harmful.)
W, 60 to 80 mesh. 6.6 Calibration Standards:
5.2.2 Column B—One 4.6-m (15-ft) by 3.2-mm outside 6.6.1 Benzene, 99+ mol %. (Warning—Poison. Carcinogen.
diameter stainless steel column packed with 20 mass % TCEP Harmful or fatal if swallowed. Extremely flammable. Vapors
on Chromosorb P, 80 to 100 mesh. can cause flash fires.)
5.3 Recorder, a strip chart recorder. An electronic integrat- 6.6.2 Isooctane (2,2,4–trimethyl pentane), 99+ mol %.
ing device or a computer capable of graphical presentation of (Warning—Extremely flammable. Harmful if inhaled.)
the chromatogram. The electronic integrating device or com- 6.6.3 Toluene, (Warning—Flammable. Vapor harmful.)
puter must be capable of measuring 0.1 volume % MEK with 6.6.4 n-Nonane, 99+ mol %. (Warning—Flammable. Vapor
satisfactory signal-to-noise. If a strip chart recorder is to be harmful.)
used, a 0 to 1–mV range recording potentiometer with a
7. Sampling
response time of 2 s or less and a maximum noise level of 60.3
% of full scale is recommended. The detector strip chart 7.1 Gasoline—(Warning—Extremely flammable. Vapors
recorder combination must produce a 4–mm deflection for a harmful if inhaled.) Samples to be analyzed by this test method
2–µL sample containing 0.1 volume % MEK when operated at shall be obtained using the procedures outlined in Practice
maximum sensitivity. D 4057.
5.4 Microsyringe, 5-µL capacity.
5.5 Volumetric Pipets, Class A, 0.5, 1, 5, 10, 15, and 20-mL 8. Preparation of Column Packings
capacities (see Specification E 694 and E 969). 8.1 Prepare two packing materials (one packing material
5.6 Measuring Pipets, 1 and 2–mL capacities calibrated in consists of 10 mass % dimethylpolysiloxane on Chromosorb
0.01 mL; 5–mL calibrated in 0.1–mL, for use in dispensing W; the other, 20 mass % TCEP on Chromosorb P) in accor-
volumes of benzene and toluene not covered by the volumetric dance with the following procedures:
pipets (see Specification E 1044 and E 1293) during prepara- 8.1.1 Dimethylpolysiloxane Packing—Weigh 45 g of the
tion of standard samples (see 11.1). Chromosorb W, 60 to 80 mesh and pour into the 500-mL flask
(5.10). Dissolve 5 g of the dimethylpolysiloxane in approxi-
NOTE 1—Other volume dispensing equipment capable of delivering the
mately 50 mL of chloroform. (Warning—Can be fatal if
specified volumes within the stated tolerance limits may be used as an
alternative to the requirements stated in 5.5 and 5.6. swallowed. Harmful if inhaled.) Pour the methyl silicone-
chloroform solution into the flask containing the Chromosorb
5.7 Flasks, volumetric, 25 and 100-mL capacity. W. Attach the flask to the evaporator (5.9), connect the
5.8 Vibrator, electric. vacuum, and start the motor. Turn on the infrared lamp and
5.9 Vacuum Source. allow the packing to mix thoroughly until dry.
5.10 Evaporator, vacuum, rotary.
5.11 Flask, boiling, round-bottom, short-neck, with 24⁄40
standard taper joint, 500-mL capacity. Suitable for use with 3
Packed column liquid phases such as OV 101 are considered to be of the
evaporator (5.10). dimethylpolysiloxane type. Other equivalent phases can also be used. Consult with
5.12 Lamp, infrared. the column manufacturer or phase supplier for information.

2
 D 3606 – 04

FIG. 1 Pressure Backflush

8.1.2 1,2,3-Tris(2-cyanoethoxy) Propane (TCEP) 9. Preparation of Column

Packing—Weigh 80 g of Chromosorb P, 80 to 100 mesh and
9.1 Cleaning Column—Clean the stainless steel tubing as
pour into the 500-mL flask (5.10). Dissolve 20 g of TCEP in
follows. Attach a metal funnel to one end of the steel tubing.
200 mL of methanol and pour into the flask containing the
Hold or mount the stainless steel tubing in an upright position
Chromosorb P. Attach the flask to the evaporator (5.9), connect
the vacuum, and start the motor. Turn on the infrared lamp and and place a drain beaker under the outlet end of the tubing.
allow the packing to mix thoroughly until dry. (Do not heat the Pour about 50 mL of methylene chloride (Warning—Harmful
packing over 180°C.) if inhaled. High concentrations can cause unconsciousness or

3
 D 3606 – 04

FIG. 2 Valve Backflush

death) into the funnel and allow it to drain through the steel 4.6-m tubing (Column B) with the TCEP packing (8.1.2) using
tubing and into the drain beaker. Repeat the washing procedure the following procedure. Close one end of each tubing with a
with 50 mL of acetone. (Warning—Harmful if inhaled. High small, glass wool plug, and connect this end to a vacuum
concentrations can cause unconsciousness or death.) Remove source by means of a glass wool-packed tube. To the other end
the funnel and attach the steel tubing to an air line, using vinyl connect a small polyethylene funnel by means of a short length
tubing to make the connection. Remove all solvent from the of vinyl tubing. Start the vacuum and pour the appropriate
steel tubing by blowing filtered, oil-free air through or pulling packing into the funnel until the column is full. While filling
a vacuum. each column, vibrate the column with the electric vibrator to
9.2 Packing Columns—Preform Columns A and B sepa- settle the packing. Remove the funnel and shut off the vacuum
rately to fit the chromatograph. Pack the 0.8-m tubing (Column source. Remove the top 6 mm (1⁄4-in.) of packing and insert a
A) with the dimethylpolysiloxane packing (8.1.1) and the glass wool plug in this end of the column.

4
 D 3606 – 04
10. Configuration of Apparatus and Establishment of 10.4 Determine Time to Backflush—The time to backflush
Conditions will vary for each column system and must be determined
10.1 Conditioning Column—Install Columns A and B as experimentally as follows. Prepare a mixture of 5 volume %
shown in Fig. 1 or Fig. 2 in accordance with the system isooctane in n-nonane. Using the injection technique described
preferred (5.1). Do not connect the exit end of Column B to the in 11.4 and with the preferred system (10.3) in the forward flow
detector until the columns have been conditioned. Pass helium mode, inject 1 µL of the isooctane – n-nonane mixture. Allow
gas through the column at approximately 40 cm3/min. Condi- the chromatogram to run until the n-nonane has eluted and the
tion the column at the listed temperatures for the specified time detector signal has returned to baseline. Measure the time in
periods. seconds, from the injection until the detector signal returns to
baseline between the isooctane and n-nonane peaks. At this
Temperature, °C Hours at Temperature
50 1⁄2 point all of the isooctane, but essentially none of the n-nonane,
100 1⁄2 should have eluted. One half of the time determined should
150 1 approximate the “time to backflush” and should be from 30 to
170 3
60 s. Repeat the run, including the injection, but switching the
10.2 Assembly—Connect the outlet of Column B to the system to the backflush mode at the predetermined “time to
detector port. Adjust the operating conditions to those listed in backflush.” This should result in a chromatogram of isooctane
Table 1, but do not turn on the detector circuits. Check the with little or no n-nonane visible. If necessary, make additional
systems for leaks. runs, adjusting the “time to backflush” until this condition of
10.3 Flow Rate Adjustment: all the isooctane and little or no n-nonane is attained. The “time
10.3.1 Column System Setup for Pressure Backflushing to backflush” so established, including the actual valve opera-
(Fig. 1): tions, must be used in all subsequent calibrations and analyses.
10.3.1.1 Open Tap A and B and close C; set the primary 11. Calibration and Standardization
pressure regulator to give the desired flow (Table 1) through 11.1 Standard Samples—Prepare seven standard samples
the column system (at an approximate gage pressure of 205 covering the range 0 to 5 volume % benzene and 0 to 20
kPa (30 psi)). Measure the flow rate at the detector vent, volume % toluene as follows: For each standard, measure the
sample side. Observe the pressure on gage GC. volume of benzene and of toluene listed below into a 100-mL
10.3.1.2 Close Tap A and open B and C. The pressure volumetric flask. Dilute to volume with isooctane (2,2,4–tri-
reading on gage GA should fall to zero immediately. If not, methyl pentane), with all components and glassware at ambient
open the needle valve until the pressure falls to zero. temperature.
10.3.1.3 Close Tap B. Adjust the secondary pressure regu- Benzene Toluene
lator until the reading of gage GC is 3.5 to 7 kPa (0.5 to 1 psi) Volume % mL Volume % mL
5 5.0 20 20.0
higher than observed in 10.3.1.1. 2.5 2.5 15 15.0
10.3.1.4 Open Tap B and adjust the backflush vent control 1.25 1.25 10 10.0
needle valve until the pressure recorded on GA approximates a 0.67 0.67 5 5.0
0.33 0.33 2.5 2.50
gage pressure of 14 to 28 kPa (2 to 4 psi). 0.12 0.12 1 1.0
10.3.1.5 Forward Flow—Open Taps A and C and close Tap 0.06 0.06 0.5 0.50
B (Fig. 1 B1). 11.2 Calibration Blends—Accurately measure 1.0 mL of
10.3.1.6 Backflush—Close Tap A and open Tap B. (There MEK into a 25-mL volumetric flask, and fill to the mark with
should be no baseline shift on switching from forward flow to the first standard sample (11.1). Continue doing this until all
backflush. If there is a baseline shift increase the secondary blends have been prepared.
pressure slightly.) (Fig. 1)
NOTE 2—Commercially prepared calibration standards may be used,
10.3.2 Column System Setup for Valve Backflushing (Fig. including those that are pre-mixed with the MEK internal standard.
2):
11.3 Chromatographic Analysis—Chromatograph each of
10.3.2.1 Set the valve in the forward flow mode (Fig. 2 B1), the calibration blends using the conditions established in 10.4
and adjust flow control A to give the desired flow (Table 1). using the following injection technique:
Measure the flow rate at the detector vent, sample side. 11.4 Injection of Sample:
10.3.2.2 Set the valve in the backflush position (Fig. 2 B2), 11.4.1 Use of an automatic liquid sample injection system is
measure the flow rate at the detector vent, sample side. If the highly recommended. If manual injections are to be made, the
flow has changed, adjust flow control B to obtain the correct injection technique in 11.4.2 is necessary so that sharp sym-
flow. (Flows should match to within 61 cm3/min). metrical peaks will be obtained.
10.3.2.3 Change the valve from forward flow to the back- 11.4.2 Flush the 5-µL microsyringe at least three times with
flush position several times and observe the baseline. There the sample mixture and then fill with about 3µ L of the sample.
should be no baseline shift or drift after the initial valve kick (Avoid including any air bubbles in the syringe.) Slowly eject
that results from the pressure surge. If there is a baseline shift, the sample until 2.0 µL remains in the syringe; wipe the needle
increase or decrease flow control B slightly to balance the with tissue and draw back the plunger to admit 1 to 2 µL of air
baseline. (A persistent drift could indicate leaks somewhere in into the syringe. Insert the needle of the syringe through the
the system.) septum cap of the chromatograph and push until the barrel of

5
 D 3606 – 04
the syringe is resting against the septum cap; then push the NOTE 5—The order of elution will be nonaromatic hydrocarbons,
plunger to the hilt and remove the syringe immediately from benzene, MEK, and toluene using the prescribed dimethylpolysiloxane
the chromatograph. and TCEP. Fig. 4 is an example of a typical chromatogram.
11.5 Calibration—Measure the area of both aromatic peaks 12.4 Measurement of Area—Measure the areas under the
and of the internal standard peak as directed in 12.4. Calculate aromatic peaks and under the MEK peak by conventional
the ratio of the benzene peak area to the MEK peak area. Plot methods.
the concentration of benzene versus the ratio. Make the same NOTE 6—The precision statement in Section 15 was developed from
calculation and plot for toluene. See Fig. 3 for an example. This data obtained using electronic integrators or on-line computers. The
must be done to ensure that the entire chromatographic system precision statement may not apply if other methods of integration or peak
is operating properly and that the concentration of any one area measurement are used.
component has not exceeded the linear response range of any
part of the system: column, detector, integrator, and other 13. Calculation
components. The calibration should be linear. 13.1 Calculate the ratios of the peak areas of benzene and
toluene to the peak area of MEK. Determine from the appro-
NOTE 3—Calibrations using computer-based chromatography systems
are an acceptable alternative to the calibration procedure specified in 11.5.
priate calibration curve the liquid volume percent of benzene
NOTE 4—If the calibration has been shown to be linear, a least squares and toluene corresponding to the calculated peak ratios.
calculation may be performed to calculate a calibration factor. The 13.2 If the results are desired on a mass basis, convert to
precision statement in Section 15 was developed from data obtained from mass percent as follows:
calibration plots and may not apply if calibration factors are used.
Benzene, mass % 5 ~VB/D! 3 0.8844 (1)
12. Procedure where:
12.1 Preparation of Sample—Accurately measure 1.0 mL VB = volume percent benzene, and
of MEK into a 25-mL volumetric flask. Fill to the mark with D = relative density of sample at 15.6/15.6°C (60/60°F).
the sample to be tested and mix well.
12.2 Chromatographic Analysis—Chromatograph the
sample, using the conditions established in 10.4 “time to Toluene, mass % 5 ~V T/D! 3 0.8719 (2)
backflush” and the injection technique described in 11.4. The
valves must be turned to backflush mode at the time determined where:
in 10.4 so that undesirable components do not enter Column B. VT = volume percent toluene, and
12.3 Interpretation of Chromatogram— Identify on the D = relative density of sample at 15.6/15.6°C (60/60°F).
chromatogram the benzene, toluene, and the internal standard
MEK peaks from the retention times of the standards. 14. Report
14.1 Report the benzene and toluene contents in liquid
volume percent to the nearest 0.1 %.

15. Precision and Bias

15.1 The following criteria should be used for judging the
acceptability of results (95 % confidence). The user should
choose the precision statement that reflects the concentration
range of each component under study.

FIG. 3 Typical Calibration Curve for Benzene (Determine for Each

Analytical System) FIG. 4 Typical Chromatogram

6
 D 3606 – 04
15.1.1 Repeatability—The difference between successive TABLE 3 Reproducibility
test results, obtained by the same operator with the same NOTE—X = the mean volume % of the component.
apparatus under constant operating conditions on identical test Component Range, volume % Reproducibility See Note
material would, in the long run, in the normal and correct
Benzene 0.1–1.5 0.13(X) + 0.05 15
operation of the test method, exceed the values in Table 2 only Benzene >1.5 0.28(X) 16
in 1 case in 20: Toluene 1.7–9 0.12(X) + 0.07 15
15.1.2 Reproducibility—The difference between two, single Toluene >9 1.15 16

and independent results, obtained by different operators work-

ing in different laboratories on identical test material would, in
the long run, in the normal and correct operation of the test volume %) fall within the specified range. The sample composition and
method, exceed the values in Table 3 only 1 case in 20: results of the cooperative study are filed at ASTM International.4
NOTE 8—The precision was determined using conventional motor
NOTE 7—In order to reflect changes in gasoline composition, the gasolines purchased on the open market. This precision should be used
precision for this test method was determined in 1994 using both when the concentration of benzene exceeds 1.5 volume % and toluene 9
conventional gasolines as well as gasolines containing oxygenates (ethers volume %. The sample compositions and results of the cooperative study
such as methyl tert-butyl ether, ethyl tert-butylether and tert- are filed at ASTM International.4
amylmethylether). The precision statement does not reflect results for
gasolines that can contain alcohols. This precision should be used when 15.2 Bias—Since there is no accepted reference method
the concentration of benzene (0.1 to 1.5 volume %) and toluene (1.7 to 9 suitable for measuring bias for this method, no statement of
bias can be made.
TABLE 2 Repeatability
16. Keywords
NOTE—X = the mean volume % of the component.
16.1 aviation gasoline; benzene; gas chromatography; gaso-
Component Range, volume % Repeatability See Note
line; toluene
Benzene 0.1–1.5 0.03(X) + 0.01 15
Benzene >1.5 0.03 16
Toluene 1.7–9 0.03(X) + 0.02 15
4
Toluene >9 0.62 16 Supporting data have been filed at ASTM International Headquarters and may
be obtained by requesting Research Report RR: D02-1042.

SUMMARY OF CHANGES

Subcommittee D02.04 has identified the location of selected changes to this standard since the last issue
(D 3606–99) that may impact the use of this standard.

(1) Added additional Referenced Documents. (3) Added new Notes 1-3.
(2) Updated 5.5 and added new 5.6. (4) Updated 6.5.1, 6.6.2, and 11.1.

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