Appendix F to Part 80 - Test for Determining the Quantity of Alcohol in Gasoline

Method 1—Water Extraction Method 1. Scope.

This test method covers the determination of the type and amount of alcohols in gasoline.

2. Summary of method.

Gasoline samples are extracted with water prior to analysis on a gas chromatograph (GC). The extraction eliminates hydrocarbon interference during chromatography. A known quantity of isopropanol is added to the fuel prior to extraction to act as an internal standard.

3. Sample description.

3.1Sample in accordance with 40 CFR part 80, appendix D.

3.2At least 100 ml. of gasoline suspected of containing ethanol and/or methanol are required.

4. Apparatus.

4.1Gas chromatograph—A gas chromatograph equipped with a flame ionization detector.

4.2Column—A gas chromatograph column, glass, 1800 by 6.35 cm. outside diameter, packed with chromosorb 102.

4.3Recorder—A 1-mv recorder with a 1 second full scale response and a chart speed of 10 mm. per minute (0.4 inches per minute).

4.4Syringe (100 ul.) for adding the internal standard.

4.5Pipet.

4.6Injection syringe (10 ul.).

4.7Extraction syringe (1-5 ml.) with 3-inch needle.

4.8250 ml. (1/2 pint) glass sample bottles with screw caps or equivalent.

4.9Calibration standard solutions extracted from gasoline containing known quantities of alcohols.

4.10Reference standard solutions extracted from gasoline containing known quantities of alcohols.

4.11Distilled water.

4.12Reagent grade isopropanol.

4.13Rubber gloves.

4.14I.D. tags.

5. Precautions. Note 1:

Gasoline and alcohols are extremely flammable and may be toxic over prolonged exposure. Methanol is particularly hazardous. Persons performing this procedure must be familiar with the chemicals involved and all precautions applicable to each.

5.1Extractions and dilutions must be performed in well-ventilated areas, preferably under a fume hood, away from open flames and sparks.

5.2Rubber gloves must be worn during the handling of gasoline and alcohols.

5.3Avoid breathing fumes from gasoline and alcohols, particularly methanol.

5.4Gas cylinders must be properly secured and the hydrogen FID fuel must be segregated from the compressed air (oxidizer) tank.

6. Visual inspection.

6.1Ensure that the samples do not certain sediment or separated phases prior to extraction.

6.2Ensure adequate quantities of GC supply gases to maintain a run.

7. Test article preparation.

7.1Gas chromatography—Use carrier gas, flow rates, detector and injection temperatures and column as specified in the GC manufacturer's specifications.

7.2Sample extraction, preparation and analysis.

7.2.1Label two 6 ml. vials with the sample identification number supplied with the original sample. The estimated percent alcohol from any screening tests must also be included on the label.

7.2.2Pipet 4 ml.±0.01 ml. of sample into one of the vials. Label as vial #1.

7.2.3Measure 100 ul. (0.1 ml.)±0.5 ul. of isopropanol into vial #1.

Note:

This adds an internal standard to the sample which is required for accurate analysis.

7.2.4Add 1 ml.±0.2 ml. of distilled water to the gasoline sample in vial #1 and shake for 10 seconds.

7.2.5Allow the mixture to separate into two phases (at least 5 minutes).

7.2.6Carefully draw off the aqueous (lower) phase using a 5 ml. syringe and long needle.

Note:

Be careful not to allow any of the gasoline phase to get into the needle. Leave a small amount (approximately 0.2 ml.) of the aqueous phase in the vial.

7.2.7Transfer the aqueous phase into the other 6 ml. vial (vial #2).

7.2.8Repeat steps 7.2.4 to 7.2.6 two more times.

7.2.9Fill vial #2 (the aqueous phase) to 4 ml.±0.05 ml. with distilled water.

7.2.10Retain the remaining original gasoline sample (not the gasoline phase).

7.2.11Discard the extracted gasoline phase in vial #1 in an appropriate manner.

7.2.12Perform a second extraction on one sample in every 20. This sample is to be labeled with the sample number and as a duplicate and run as a normal sample.

7.2.13Transfer approximately 2 ml. of the aqueous solution to vials compatible with the autosampler. Tag the vial with the sample number.

7.2.14Perform analysis of the sample according to the GC manufacturer's specifications.

7.3Standards.

7.3.1Calibration standard solutions (made in gasoline).

7.3.1.1Reagent grade or better alcohols (including undenatured ethanol) are to be diluted with regular unleaded gasoline. The isopropanol internal standard is to be added during extraction of the alcohols. Newly acquired stocks of reagent grade alcohols shall be diluted to 10% with hydrocarbon-free water and analyzed for contamination by GC before use.

7.3.1.2Required calibration standards (% by volume in gasoline):

AlcoholRange (percent)Standard (MIN)Methanol0.5-125Ethanol0.5-115

The standards should be as equally spaced within the range as possible and may contain more than one alcohol.

Note:

Level #1 must contain all of the alcohols.

8. Quality control provisions.

8.1Alcohol(s) in water solution may be used to characterize the GC. The resulting characterization always reflects the absolute sensitivity of the instrument to each alcohol.

8.2Calibration standards are made by extraction of known alcohol(s) in gasoline blends. These standards account for inaccuracies caused by incomplete extraction of alcohols.

8.3The addition of isopropanol as an internal standard reduces errors caused by variations in injection volumes, and further reduces inaccuracies caused by incomplete extraction of alcohols.

8.4Sufficient sample should be retained to permit reanalysis.

8.5Running averages of reference standards data must not exceed 0.75% of applicable limits or investigation should be started for the cause of such variation.

9. Calculations.

9.1Calculate purity of component as follows:

$EC10NO91.000$ where: Pi = purity of component i, Ai = area of response of component i, and ΣA = total area response of all components.

9.2Calculate response factors as follows:

$EC10NO91.001$ where: Fi = response factor for component of interest i, Ai = area response for component of interest i, Ais = area response of internal standard, Wi = weight of component of interest i (be sure to consider all sources), Wis = weight of internal standard, Pi = purity of component of interest i as determined in 9.1 expressed as a decimal, and Pis = purity of internal standards as determined in 9.1 expressed as a decimal.

9.3Calculate the percent alcohols as follows:

$EC10NO91.002$ where: Ai = peak area component i, Ais = peak area of internal standard, Wi = weight of sample, Wis = weight of internal standard, and Fi = response factor for component i. 10. Report.

10.1Report results to the nearest 0.1%.

11. Precision and accuracy.

11.1Precision—The precision of this test method has not been determined.

11.2Accuracy—The accuracy of this test method has not been determined.

Method 2—Test Method for Determination of C1 to C4 Alcohols and MTBE in Gasoline by Gas Chromatography 1. Scope.

1.1This test method covers a procedure for determination of methanol, ethanol, isopropanol, n-propanol, isobutanol, sec-butanol, tert-butanol, n-butanol, and methyl tertiary butyl ether (MTBE) in gasoline by gas chromatography.

1.2Individual alcohols and MTBE are determined from 0.1 to 10 volume %. Any sample found to contain greater than 10 volume % of an alcohol or MTBE shall be diluted to concentrations within these limits.

1.3Sl (metric) units of measurement are preferred and used throughout this standard. Alternative units, in common usage, are also provided to improve the clarity and aid the user of this test method.

1.4This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address all of the safety problems 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.

2. Referenced documents.

2.1ASTM Standards:

D4307Practice for Preparation of Liquid Blends for Use as Analytical Standards 1 D4626Practice for Calculation of Gas Chromatographic Response Factors 1 E260Practice for Packed Column Gas Chromatographic Procedures 2 E355Practice for Gas Chromatography Terms and Relationships 2

2.2EPA Regulations:

40 CFR Part 80 Appendix D 3. Descriptions of terms specific to this standard.

3.1MTBE—methyl tertiary butyl ether.

3.2Low volume connector—a special union for connecting two lengths of tubing 1.6 mm inside diameter and smaller. Sometimes this is referred to as a zero dead volume union.

3.3Oxygenates—used to designate fuel blending components containing oxygen, either in the form of alcohol or ether.

3.4Split ratio—a term used in gas chromatography using capillary columns. The split ratio is the ratio of the total flow of the carrier gas to the sample inlet versus the flow of carrier gas to the capillary column. Typical values range from 10:1 to 500:1 depending upon the amount of sample injected and the type of capillary column used.

3.5WCOT—abbreviation for a type of capillary column used in gas chromatography that is wall-coated open tubular. This type of column is prepared by coating the inside of the capillary with a thin film of stationary phase.

3.6TCEP—1,2,3,-tris-2-cyanoethoxypropane—a gas chromatographic liquid phase.

4. Summary of test method.

4.1An internal standard, tertiary amyl alcohol, is added to the sample which is then introduced into a gas chromatograph equipped with two columns and a column switching valve. The sample first passes onto a polar TCEP column which elutes lighter hydrocarbons to vent and retains the oxygenated and heavier hydrocarbons. After methylcyclopentane, but before MTBE elutes from the polar column, the valve is switched to backflush the oxygenates onto a WCOT non-polar column. The alcohols and MTBE elute from the non-polar column in boiling point order, before elution of any major hydrocarbon constituents. After benzene elutes from the non-polar column, the column switching valve is switched back to its original position to backflush the heavy hydrocarbons. The eluted components are detected by a flame ionization or thermal conductivity detector. The detector response, proportional to the component concentration, is recorded; the peak areas are measured; and the concentration of each component is calculated with reference to the internal standard.

5. Significance and use.

5.1Alcohols and other oxygenates may be added to gasoline to increase the octane number. Type and concentration of various oxygenates are specified and regulated to ensure acceptable commercial gasoline quality. Drivability, vapor pressure, phase separation, and evaporative emissions are some of the concerns associated with oxygenated fuels.

5.2This test method is applicable to both quality control in the production of gasoline and for the determination of deliberate or extraneous oxygenate additions or contamination.

6. Apparatus.

6.1Chromatograph:

6.1.1A gas chromatographic instrument which can be operated at the conditions given in Table 1, and having a column switching and backflushing system equivalent to Fig. 1. Carrier gas flow controllers shall be capable of precise control where the required flow rates are low (Table 1). Pressure control devices and gages shall be capable of precise control for the typical pressures required.

Table 1—Chromatographic Operating ConditionsTemperaturesFlows, mL/minOther parameters: Carrier gas, heliumColumn oven, °C60To injector75Sample size, μL3Injector, °C200Column5Split ratio15 : 1Detector—TCD, °C200Auxiliary3Backflush, min0.2-0.3FID, °C250Makeup18Valve reset time, min8-10Valve, °C60Total analysis time, min18-20

6.1.2Detector—A thermal conductivity detector or flame ionization detector may be used. The system shall have sufficient sensitivity and stability to obtain a recorded deflection of at least 2 mm at a signal-to-noise ratio of at least 5 to 1 for 0.005 volume % concentration of an oxygenate.

6.1.3Switching and backflushing valve—A valve, to be located within the gas chrom-a-to-graph-ic column oven, capable of performing the functions described in Section 11. and illustrated in Fig. 1. The valve shall be of low volume design and not contribute significantly to chromatographic deterioration.

6.1.3.1Valco Model No. CM-VSV-10-HT, 1.6-mm (1/16-in.) fittings. This particular valve was used in the majority of the analyses used for the development of Section 15.

6.1.3.2Valco Model No. C10W, 0.8-mm (1/32-in.) fittings. This valve is recommended for use with columns of 0.32-mm inside diameter and smaller.

6.1.4Although not mandatory, an automatic valve switching device is strongly recommended to ensure repeatable switching times. Such a device should be synchronized with injection and data collection times. If no such device is available, a stopwatch, started at the time of injection, should be used to indicate the proper valve switching time.

6.1.5Injection system—The chrom-a-to-graph should be equipped with a splitting-type inlet device. Split injection is necessary to maintain the actual chrom-a-to-graphed sample size within the limits of column and detector optimum efficiency and linearity.

6.1.6Sample introduction—Any system capable of introducing a representative sample into the split inlet device. Microlitre syringes, automatic syringe injectors, and liquid sampling valves have been used successfully.

6.2Data presentation or calculation, or both:

6.2.1Recorder—A recording potentiometer or equivalent with a full-scale deflection of 5 mV or less. Full-scale response time should be l s or less with sufficient sensitivity and stability to meet the requirements of 6.1.2.

6.2.2Integrator or computer—Devices capable of meeting the requirements of 6.1.2, and providing graphic and digital presentation of the chromatographic data, are recommended for use. Means shall be provided for determining the detector response. Peak heights or areas can be measured by computer, electronic integration or manual techniques.

6.3Columns, two as follows:

6.3.1Polar column—This column performs a preseparation of the oxygenates from volatile hydrocarbons in the same boiling point range. The oxygenates and remaining hydrocarbons are backflushed onto the non-polar column in section 6.3.2. Any column with equivalent or better chromatographic efficiency and selectivity to that described in 6.3.1.1 can be used. The column shall perform at the same temperature as required for the column in 6.3.2.

6.3.1.1TCEP micro-packed column, 560 mm (22 in.) by 1.6-mm (1/16-in.) outside diameter by 0.38-mm (0.015-in.) inside diameter stainless steel tube packed with 0.14 to 0.15g of 20% (mass/mass) TCEP on 80/100 mesh Chromosorb P(AW). This column was used in the (ASTM) cooperative study to provide the Precision and Bias data referred to in Section 15.

6.3.2Non-polar (analytical) column—Any column with equivalent or better chrom-a-to-graph-ic efficiency and selectivity to that described in 6.3.2.1 and illustrated in Fig. 2 can be used.

6.3.2.1WCOT methyl silicone column, 30m (1181 in.) long by 0.53 mm (0.021-in.) inside diameter fused silica WCOT column with a 2.6-μm film thickness of cross-linked methyl siloxane. This column was used in the (ASTM) cooperative study to provide the Precision and Bias data referred to in Section 15.

7. Reagents and materials.

7.1Carrier gas—Carrier gas appropriate to the type of detector used. Helium has been used successfully. The minimum purity of the carrier gas used must be 99.95 mol %.

7.2Standards for calibration and identification—Standards of all components to be analyzed and the internal standard are required for establishing identification by retention as well as calibration for quantitative measurements. These materials shall be of known purity and free of the other components to be analyzed.

Note 1.

Warning—These materials are flammable and may be harmful or fatal if ingested or inhaled.

7.3Preparation of calibration blends—For best results, these components must be added to a stock gasoline or petroleum naphtha, free of oxygenates (Warning—See Note 2). Refer to Test Method D 4307 for preparation of liquid blends. The preparation of several different blends, at different concentration levels covering the scope of the method, is recommended. These will be used to establish the linearity of the component response.

Note 2.

Warning—Extremely flammable. Vapors harmful if inhaled.

7.4Methylene chloride—Used for column preparation. Reagent grade, free of non-volatile residue.

Note 3.

Warning—Harmful if inhaled. High concentrations may cause unconsciousness or death.

8. Preparation of column packings.

8.1TCEP column packing:

8.1.1Any satisfactory method, used in the practice of the art that will produce a column capable of retaining the C1 to C4 alcohols and MTBE from components of the same boiling point range in a gasoline sample. The following procedure has been used successfully.

8.1.2Completely dissolve 10 g of TCEP in 100 mL of methylene chloride. Next add 40 g of 80/100 mesh Chromosorb P(AW) to the TCEP solution. Quickly transfer this mixture to a drying dish, in a fume hood, without scraping any of the residual packing from the sides of the container. Constantly, but gently, stir the packing until all of the solvent has evaporated. This column packing can be used immediately to prepare the TCEP column.

9. Preparation of micro-packed TCEP column.

9.1Wash a straight 560 mm length of 1.6-mm outside diameter (0.38-mm inside diameter) stainless steel tubing with methanol and dry with compressed nitrogen.

9.2Insert 6 to 12 strands of silvered wire, a small mesh screen or stainless steel frit inside one end of the tube. Slowly add 0.14 to 0.15 g of packing material to the column and gently vibrate to settle the packing inside the column. When strands of wire are used to retain the packing material inside the column, leave 6.0 mm (0.25 in.) of space at the top of the column.

9.3Column conditioning—Both the TCEP and WCOT columns are to be briefly conditioned before use. Connect the columns to the valve (see 11.1) in the chromatographic oven. Adjust the carrier gas flows as in 11.3 and place the valve in the RESET position. After several minutes, increase the column oven temperature to 120 °C and maintain these conditions for 5 to 10 min. Cool the columns below 60 °C before shutting off the carrier flow.

10. Sampling.

10.1Gasoline samples to be analyzed by this test method shall be sampled in accordance with 40 CFR part 80, appendix D.

11. Preparation of apparatus and establishment of conditions.

11.1Assembly—Connect the WCOT column to the valve system using low volume connectors and narrow bore tubing. It is important to minimize the volume of the chromatographic system that comes in contact with the sample, otherwise peak broadening will occur.

11.2Adjust the operating conditions to those listed in Table 1, but do not turn on the detector circuits. Check the system for leaks before proceeding further.

11.3Flow rate adjustment.

11.3.1Attach a flow measuring device to the column vent with the valve in the RESET position and adjust the pressure to the injection port to give 5.0 mL/min flow (14 psig). Soap bubble flow meters are suitable.

11.3.2Attach a flow measuring device to the split injector vent and adjust flow from the split vent using the A flow controller to give a flow of 70 mL/min. Recheck the column vent flow set in 11.3.1 and adjust if necessary.

11.3.3Switch the valve to the BACK-FLUSH position and adjust the variable restrictor to give the same column vent flow set in 11.3.1. This is necessary to minimize flow changes when the valve is switched.

11.3.4Switch the valve to the inject position RESET and adjust the B flow controller to give a flow of 3.0 to 3.2 mL/min at the detector exit. When required for the particular instrumentation used, add makeup flow or TCD switching flow to give a total of 21 mL/min at the detector exit.

11.4When a thermal conductivity detector is used, turn on the filament current and allow the detector to equilibrate. When a flame ionization detector is used, set the hydrogen and air flows and ignite the flame.

11.5Determine the Time of Backflush—The time to backflush will vary slightly for each column system and must be determined experimentally as follows. The start time of the integrator and valve timer must be synchronized with the injection to accurately reproduce the backflush time.

11.5.1Initially assume a valve BACK-FLUSH time of 0.23 min. With the valve RESET, inject 3 μL of a blend containing at least 0.5% or greater oxygenates (7.3), and simultaneously begin timing the analysis. At 0.23 min., rotate the valve to the BACKFLUSH position and leave it there until the complete elution of benzene is realized. Note this time as the RESET time, which is the time at which the valve is returned to the RESET position. When all of the remaining hydrocarbons are backflushed the signal will return to a stable baseline and the system is ready for another analysis. The chromatogram should appear similar to that illustrated in Fig. 2.

11.5.2It is necessary to optimize the valve BACKFLUSH time by analyzing a standard blend containing oxygenates. The correct BACKFLUSH time is determined experimentally by using valve switching times between 0.2 and 0.3 min. When the valve is switched too soon, C5 and lighter hydrocarbons are backflushed and are co-eluted in the C4 alcohol section of the chromatogram. When the valve BACKFLUSH is switched too late, part or all of the MTBE component is vented resulting in an incorrect MTBE measurement. Chromatograms resulting from incorrect valve times are shown in Figs. 3 and 4.

12. Calibration and standardization.

12.1Identification—Determine the retention time of each component by injecting small amounts either separately or in known mixtures or by comparing the relative retention times with those in Table 2.

12.2Standardization—The area under each peak in the chromatogram is considered a quantitative measure of the corresponding compound. Measure the peak area of each oxygenate and of the internal standard by either manual methods or electronic integrator. Calculate the relative volume response factor of each oxygenate, relative to the internal standard, according to Test Method D 4626.

Table 2—Retention Characteristics for TCEP/WCOT Column Set Conditions as in Table 1ComponentRetention time, minRelative retention time (t-amyl alcohol = 1.00)Methanol3.210.44Ethanol3.580.50Isopropanol3.950.56tert-Butanol4.310.61n-Propanol4.750.68MTBE5.290.76sec-Butanol5.630.82Isobutanol6.330.93n-Butanol7.551.10Benzene7.881.17 13. Procedure.

13.1Preparation of sample—Precisely add a quantity of the internal standard to an accurately measured quantity of sample. Concentrations of 1 to 5 volume percent have been used successfully.

13.2Chromatographic analysis—Introduce a representative aliquot of the sample, containing internal standard, into the chromatograph using the same technique as used for the calibration analyses. An injection volume of 3 μL with a 15:1 split ratio has been used successfully.

13.3Interpretation of chromatogram—Compare the results of sample analyses to those of calibration analyses to determine identification of oxygenates present.

14. Calculation.

14.1After identifying the various oxygenates, measure the area of each oxygenate peak and that of the internal standard. Calculate the volume percent of each oxygenate as follows:

$EC10NO91.009$ where: Vj = volume percent of oxygenate to be determined, VS = volume of internal standard (tert-amyl alcohol) added, VG = volume of gasoline sample taken, PAj = peak area of the oxygenate to be determined, PAS = peak area of the internal standard (tert-amyl alcohol), and Sj = relative volume response factor of each component (relative to the internal standard).

14.2Report the volume of each oxygenate. If the volume percent exceeds 10%, dilute the sample to a concentration lower than 10% and repeat the procedures in sections 13 and 14.

15. Precision and bias.

15.1Precision—The precision of this test method as determined by statistical examination of the interlaboratory test results is as follows:

15.1.1 Repeatability—The difference between successive results obtained by the same operator with the same apparatus under constant operating conditions on identical test materials would, in the long run, in the normal and correct operation of the test method exceed the following values only in one case in twenty (see Table 3).

Methanol 0.086 × (V+0.070)Isobutanol 0.064 × (V+0.086)Ethanol 0.083 × (V+0.000) sec-Butanol 0.014 × √ VIsopro-panol 0.052 × (V+0.150)tert-Butanol 0.052 × (V+0.388)n-Propanol 0.040 × (V+0.026)n-Butanol 0.043 × (V+0.020)MTBE 0.104 × (V+0.028) where V is the mean volume percent.

15.1.2 Reproducibility—The difference between two single and independent results obtained by different operators working in different laboratories on identical material would, in the long run, exceed the following values only in one case in twenty (see Table 3).

Methanol 0.361 × (V+0.070)Isobutanol 0.179 × (V+0.086)Ethanol 0.373 × (V+0.000)sec-Butanol 0.277 × √ VIsopro-panol 0.214 × (V+0.150)tert-Butanol 0.178 × (V+0.388)n-Propanol 0.163 × (V+0.026)n-Butanol 0.415 × (V+0.020)MTBE 0.244×(V+0.028) where V is the mean volume percent.

15.2 Bias—Since there is no accepted reference material suitable for determining bias for the procedure in the test method, bias cannot be determined.

Table 3—Precision Intervals—Determined from Cooperative Study Data Summarized in Section 15ComponentsVolume percent0.20 0.501.002.003.004.005.006.00RepeatabilityMethanol0.020.050.090.180.260.350.440.52Ethanol0.020.040.080.170.250.330.420.50Isopro-panol0.020.030.060.110.160.220.270.32n-Propanol0.010.020.040.080.120.160.200.24tert-Butanol0.030.050.070.120.180.230.280.33sec-Butanol0.010.010.010.020.020.030.030.03Isobu-tanol0.020.040.070.130.200.260.330.39n-Butanol0.010.020.040.090.130.170.220.26MTBE0.020.050.110.210.310.420.520.63ReproducibilityMethanol0.100.210.390.751.111.471.832.19Ethanol0.070.190.370.751.121.491.872.24Isopro-panol0.070.140.250.460.670.891.101.32n-Propanol0.040.090.170.330.490.660.820.98tert-Butanol0.100.160.250.430.600.780.961.14sec-Butanol0.120.200.280.390.480.550.620.68Isobu-tanol0.050.100.190.370.550.730.911.09n-Butanol0.090.220.420.841.251.672.082.50MTBE0.050.120.230.450.680.901.131.35 EC01SE92.150 EC01SE92.151 EC01SE92.152 EC01SE92.153