ASTM D5441-93
(Test Method)Standard Test Method for Analysis of Methyl Tert-Butyl Ether (MTBE) by Gas Chromatography
Standard Test Method for Analysis of Methyl Tert-Butyl Ether (MTBE) by Gas Chromatography
SCOPE
1.1 This test method provides for determination of the purity of methyl tert-butyl ether (MTBE) by gas chromatography. It also provides a procedure to measure impurities in MTBE such as C 4 to C 12 olefins, methyl, isopropyl and tert-butyl alcohols, methyl sec-butyl and methyl tert-amyl ethers, acetone, and methyl ethyl ketone. Impurities are determined to a minimum concentration of 0.02 mass %.
1.2 This test method is not applicable to the determination of MTBE in gasoline.
1.3 Water cannot be determined by this test method and must be measured by a procedure such as Test Method D1364 and the result used to normalize the chromatographic values.
1.4 A majority of the impurities in MTBE is resolved by the test method, however, some co-elution is encountered.
1.5 This test method is inappropriate for impurities that boil at temperatures higher than 180°C or for impurities that cause poor or no response in a flame ionization detector, such as water.
1.6 The values stated in SI (metric) units of measurement are preferred and used throughout the standard. Alternate units, in common usage, are also provided to improve clarity and aid the user of this method.
1.7 This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user of this standard to consult and establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: D 5441 – 93
Standard Test Method for
Analysis of Methyl Tert-Butyl Ether (MTBE) by Gas
Chromatography
This standard is issued under the fixed designation D 5441; 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 Analytical Standards
D 4626 Practice for Calculation of Gas Chromatographic
1.1 This test method provides for determination of the
Response Factors
purity of methyl tert-butyl ether (MTBE) by gas chromatogra-
E 355 Practice for Gas Chromatography Terms and Rela-
phy. It also provides a procedure to measure impurities in
tionships
MTBE such as C to C olefins, methyl, isopropyl and
4 12
E 594 Practice for Testing Flame Ionization Detectors Used
tert-butyl alcohols, methyl sec-butyl and methyl tert-amyl
in Gas Chromatography
ethers, acetone, and methyl ethyl ketone. Impurities are deter-
mined to a minimum concentration of 0.02 mass %.
3. Terminology
1.2 This test method is not applicable to the determination
3.1 Definitions:
of MTBE in gasoline.
3.1.1 This test method makes reference to many common
1.3 Water cannot be determined by this test method and
gas chromatographic procedures, terms, and relationships.
must be measured by a procedure such as Test Method D 1364
Detailed definitions of these can be found in Practices E 355
and the result used to normalize the chromatographic values.
and E 594.
1.4 A majority of the impurities in MTBE is resolved by the
3.2 Definitions of Terms Specific to This Standard:
test method, however, some co-elution is encountered.
3.2.1 C to C olefins— common olefin impurities in
4 12
1.5 This test method is inappropriate for impurities that boil
MTBE are unreacted feedstock and dimers or trimers of feed
at temperatures higher than 180°C or for impurities that cause
such as trimethylpentene or pentamethylheptene.
poor or no response in a flame ionization detector, such as
water.
4. Summary of Test Method
1.6 The values stated in SI (metric) units of measurement
4.1 A representative aliquot of the MTBE product sample is
are preferred and used throughout the standard. Alternate units,
introduced into a gas chromatograph equipped with a methyl
in common usage, are also provided to improve clarity and aid
silicone bonded phase fused silica open tubular column.
the user of this method.
Helium carrier gas transports the vaporized aliquot through the
1.7 This standard does not purport to address all of the
column where the components are separated by the chromato-
safety problems, if any, associated with its use. It is the
graphic process. Components are sensed by a flame ionization
responsibility of the user of this standard to consult and
detector as they elute from the column.
establish appropriate safety and health practices and deter-
4.2 The detector signal is processed by an electronic data
mine the applicability of regulatory limitations prior to use.
acquisition system or integrating computer. Each eluting com-
ponent is identified by comparing its retention time to those
2. Referenced Documents
established by analyzing standards under identical conditions.
2.1 ASTM Standards:
4.3 The concentration of each component in mass percent is
D 1364 Test Method for Water in Volatile Solvents (Fischer
2 determined by normalization of the peak areas after each peak
Reagent Titration Method)
area has been corrected by a detector response multiplication
D 3700 Practice for Containing Hydrocarbon Fluid Samples
3 factor. The detector response factors are determined by ana-
Using Floating Piston Cylinder
lyzing prepared standards with concentrations similar to those
D 4057 Practice for Manual Sampling of Petroleum and
3 encountered in the sample.
Petroleum Products
D 4307 Practice for Preparation of Liquid Blends for Use as
5. Significance and Use
5.1 The presence of impurities in MTBE product can have a
This test method is under the jurisdiction of ASTM Committee D-2 on
deleterious effect upon the value of MTBE as a gasoline
Petroleum Products and Lubricants and is the direct responsibility of Subcommittee
D02.D0.05 on C Hydrocarbons and Oxygenated Hydrocarbons.
Current edition approved Aug. 15, 1993. Published October 1993.
Annual Book of ASTM Standards, Vol 06.04.
3 4
Annual Book of ASTM Standards, Vol 05.02. Annual Book of ASTM Standards, Vol 14.01.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
D 5441
additive. Oxygenate and olefin contents are of primary con- 7.3 Open Tubular Column—This test method utilizes a
cern. This test method provides a knowledge of the composi- fused silica open tubular column with non-polar methyl sili-
tion of MTBE product. This is useful in the evaluation of cone bonded (cross-linked) phase internal coating such as one
process operations control, in the valuation of the product, and of the following:
for regulatory purposes.
Column length 50 m 100 m 150 m
Film thickness 0.5 μm 0.5 μm 1.0 μm
5.2 Open tubular column gas chromatography with a flame
Internal diameter 0.20 mm 0.25 mm 0.25 mm
ionization detector, used by the test method, is a technique that
is sensitive to the contaminants commonly found in MTBE, Other columns with equal or greater resolving power may be
used. A minimum resolution between trans-2-pentene and
and a technique that is widely used.
tert-butanol, and between cis-2-pentene and tert-butanol of 1.3
6. Interferences
is required. The 150 m column is expected to decrease the
likelihood of co–elution of impurities.
6.1 Cyclopentane and 2,3-dimethylbutane have been ob-
7.4 Electronic Data Acquisition System—Any data acquisi-
served to co-elute with MTBE. However, these are not com-
tion and integration device used for quantification of these
monly found impurities in MTBE.
analyses must meet or exceed these minimum requirements:
7.4.1 Capacity for at least 50 peaks per analysis,
7. Apparatus
7.4.2 Normalized area percent calculations with response
7.1 Gas Chromatograph—Instrumentation capable of oper-
factors,
ating at the conditions listed in Table 1. A heated flash
7.4.3 Identification of individual components based on re-
vaporizing injector designed to provide a linear sample split
tention time,
injection (that is, 200:1) is required for proper sample intro-
7.4.4 Noise and spike rejection capability,
duction. Carrier gas controls must be of adequate precision to
7.4.5 Sampling rate for fast (<1 s) peaks,
provide reproducible column flows and split ratios in order to
7.4.6 Positive and negative sloping baseline correction,
maintain analytical integrity. Pressure control devices and
7.4.7 Peak detection sensitivity compensation for narrow
gages must be designed to attain the linear velocity required in
and broad peaks, and
the column used (for example, if a 150 m column is used, a
7.4.8 Non-resolved peaks separated by perpendicular drop
pressure of approximately 550 kPa (80 psig) is required). A
or tangential skimming as needed.
hydrogen flame ionization detector with associated gas controls
and electronics, designed for optimum response with open
8. Reagents and Materials
tubular columns, is required.
8.1 Carrier Gas, helium, 99.99 % pure. (Warning—See
7.2 Sample Introduction—Manual or automatic liquid sy-
Note 1.)
ringe sample injection to the splitting injector is employed.
Devices capable of 0.1 to 0.5 μL injections are suitable. It
NOTE 1—Warning: Compressed gas under high pressure.
should be noted that inadequate splitter design, or poor
8.2 Fuel Gas, hydrogen, 99.99 % pure. (Warning—See
injection technique, or both can result in poor resolution.
Note 2.)
Overloading of the column can also cause loss of resolution for
some components and, since overloaded peaks are skewed, NOTE 2—Warning: Extremely flammable gas under pressure.
variation in retention times. Watch for any skewed peaks that
8.3 Oxidant, air, oil free, (Warning—See Note 1.).
indicate overloading during column evaluation. Observe the
8.4 Make-Up Gas, nitrogen, 99.99 % pure. (Warning—See
component size and where possible, avoid conditions leading
Note 1.)
to this problem during the analyses.
8.5 Reference Standards:
8.5.1 tert-Amyl methyl ether, (Warning—See Note 3.)
TABLE 1 Typical Operating Conditions
NOTE 3—Warning: Flammable Liquid. Harmful if inhaled.
Column Temperature Program
8.5.2 Butane,(Warning—See Note 3.)
Column length 50 m 100 m 150 m
8.5.3 tert-Butanol,(Warning—See Note 3.)
Initial temperature 40°C 50°C 60°C
Initial hold time 13 min 13 min 13 min
8.5.4 sec-Butyl methyl ether, (Warning—See Note 3.)
Program rate 10°C/min 10°C/min 10°C/min 8
8.5.5 4,4-Dimethyl-2-neopentyl-1-pentene, (Warning—
Final temperature 180°C 180°C 180°C
See Note 3.)
Final hold time 3 min 7 min 20 min
Injector
8.5.6 Isobutylene,(Warning—See Note 3.)
Temperature 200°C
8.5.7 Methanol,(Warning—See Note 4.)
Split ratio 200:1
Sample size 0.1 to 0.5 μL
Detector
Type flame ionization
Petrocol DH series columns available from Supelco, Inc., Bellefonte, PA, USA
Temperature 250°C
have proven satisfactory for this test method and were used to obtain the retention
Fuel gas hydrogen (’30 mL/min)
data and example chromatogram shown. Also, HP-PONA columns available from
Oxidizing gas air (’300 mL/min)
Hewlett Packard Company, Wilmington, DE, have been found satisfactory.
Make-up gas nitrogen (’30 mL/min)
A 96 % pure sample obtained from Aldrich Chemical Company, Inc., Milwau-
Carrier Gas
kee, Wisconsin was the highest purity found.
Type helium
Average linear velocity 20–24 cm/s Available from Farcham Laboratories, Gainesville, FL
Available from Wiley Organics, Coshocton, OH.
D 5441
NOTE 4—Warning: Toxic Flammable Liquid. Harmful if inhaled or u 5 L/t (1)
ave m
ingested.
where:
8.5.8 2-Methyl-2-butene, (Warning—See Note 3.)
L = the length of the column in cm, and
8.5.9 Methyl tert-butyl ether, 99 + % pure, (Warning—
t = the retention time in seconds of methane.
m
See Note 3.)
10.3 Adjust the operating conditions of the gas chromato-
8.5.10 2,2,4,6,6-Pentamethyl-3-heptene, (Warning—See
graph to conform to the list in Table 1. Turn on the detector,
Note 3.)
ignite the flame, and allow the system to equilibrate.
8.5.11 n-Pentane,(Warning—See Note 3.)
8.5.12 cis-2-Pentene,(Warning—See Note 3.)
11. Column Evaluation and Optimization
8.5.13 trans-2-Pentene (Warning—See Note 3.)
11.1 In order to establish that the column/temperature pro-
8.5.14 2,4,4-Trimethyl-1-pentene,(Warning—See Note 3.)
gram will perform the required separation, the resolution
8.5.15 2,4,4-Trimethyl-2-pentene,(Warning—See Note 3.)
between cis-2-pentene and tert-butanol and between trans-2-
8.5.16 1 % Contaminant Standard— contains 1.0 % of
pentene and tert-butanol must be determined. The retention of
some of the contaminants in MTBE, (Warning—See Note 3.)
tert-butanol relative to cis- and trans-2-pentene is very tem-
8.5.17 0.1 % Contaminant Standard, contains 0.1 % of
perature dependent. The order of elution of cis-2-pentene and
some of the contaminants in MTBE, (Warning—See Note 3.)
tert-butanol reverses at subambient temperature. A column
which does not resolve these components after adjusting
9. Sampling
operating conditions is unsuitable.
9.1 MTBE can be sampled either in a floating piston
11.2 Analyze a standard mixture that contains approxi-
cylinder or into an open container since vapor pressures less
mately 1 % each of tert-butanol, cis-2-pentene, and trans-2-
than 70 kPa (10 psi) are expected.
pentene in MTBE by the procedure in Section 13. Calculate
9.1.1 Cylinder Sampling—Refer to Practice D 3700 for
resolution (R) between tert-butanol and cis-2-pentene and
instructions on transferring a representative sample from a
between trans-2-pentene and tert-butanol using Eq 2. Both
source into a floating piston cylinder. Add inert gas to the
resolutions must be at least 1.3.
ballast side of the piston to achieve a pressure of 310 kPa (45
2 t 2 t !
~
B A
psi) above the vapor pressure of the sample.
R 5 (2)
1.699 W 1 W
~ !
A B
9.1.2 Open Container Sampling—Refer to Practice D 4057
for instructions on manual sampling from bulk storage into
open containers. Stopper container immediately after drawing where:
R = resolution,
sample.
t = retention time Component A,
9.2 Preserve the sample by cooling to approximately 4°C
A
t = retention time Component B,
and by maintaining that temperature until immediately prior to
B
W = peak width at half height of Component A, and
analysis. A
W = peak width at half height of Component B and t > t
B B A
9.3 Transfer an aliquot of the cooled sample into a pre-
cooled septum vial, then seal appropriately. Obtain the test
12. Calibration and Standardization
specimen for analysis directly from the sealed septum vial, for
12.1 Component peaks from a sample analysis are identified
either manual or automatic syringe injection.
by matching their retention time with the retention time of
reference compounds analyzed under identical conditions.
10. Preparation of Apparatus
Typical retention times of most common contaminants in
10.1 Install and condition column in accordance with manu-
MTBE products are listed in Table 2. Analyze mixtures
facturer’s or supplier’s instructions. After conditioning, attach
containing these compounds to verify their retention times.
column outlet to flame ionization detector inlet and check for
Mixtures used for determining retention times can be blended
leaks throughout the system. When leaks are found, tighten or
from pure compounds or purchased. Retention times of other
replace fittings before proceeding.
suspected contaminants can be established by analyzing mix-
10.2 Adjust the carrier gas flow rate so that an average
tures containing these materials under identical conditions. A
linear velocity at the starting temperature of the run is between
typical chromatogram of a MTBE product sample, analyzed on
21 and 24 cm/s, as determined in Eq 1. Flow rate adjustment is
the 150 meter column, is shown in Fig. 1. The peaks are
made by raising or lowering the carrier gas pressure (head
indexed to Table 2.
pressure) to the injector. The following starting point pressures
12.2 Typical mass relative response factors are found in
can be useful to adjust the carrier gas flow:
Table 2. These response factors must be verified by analyzing
Column length 50 m 100 m 150 m
a prepared standard with concentrations similar to those
Starting point pressure, kPa (psig) 262 (38) 275 (40) 552 (80)
encountered in a MTBE product sample and comparing the
10.2.1 Average Linear Gas Velocity:
measured res
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