1、BOILING POINT DISTRIBUTION OF HYDROCARBONS BY GAS CHROMATOGRAPHY UOP Method 621-98 SCOPE This method is for analyzing by gas chromatography mixtures of liquid hydrocarbons in the range of C5through C20, using a column that separates components by boiling points. Procedures are provided for several a
2、pplications, depending on the calibration used. These include, but are not limited to, (a) component distribution as defined by boiling points and corresponding carbon numbers, (b) determination of individual components resolved from a mixture of other components, and (c) analysis of a total sample
3、wherein the identities of the major components or groups of components are known. Variations may be made as required, such as grouping of specific components by boiling ranges or extending the application to other ranges. The range of quantitation for a single component (or group of components) is 0
4、.05 to 99.9 mass-%. OUTLINE OF METHOD The sample is injected into a gas chromatograph that is equipped with a flame ionization detector (FID) and a fused silica capillary column internally coated with cross-linked methyl silicone. One of the following is analyzed under identical conditions: a) A qua
5、ntitative blend composed of n-paraffins whose boiling points extend throughout the boiling range of the sample to be analyzed. The “calibration chromatogram” obtained is used to determine the various boiling points or ranges by comparing the retention times of the n-paraffins to the observed retenti
6、on times of the sample components. b) A quantitative blend containing the individual components of interest in a mixture similar in composition to the sample. c) A quantitative blend of a wide boiling range mixture wherein all the major components are known. The mass-% composition of the sample is o
7、btained by the internal normalization technique of quantitation wherein component areas are first corrected for response differences and then normalized to 100%. Since hydrocarbon components have essentially the same detector response on a mass basis in an FID, a relative response factor of 1.000 ma
8、y be used for all components or groups, except when greater accuracy is desired or the samples contain a significant amount of benzene, toluene or mixed xylenes. IT IS THE USERS RESPONSIBILITY TO ESTABLISH APPROPRIATE PRECAUTIONARY PRACTICES AND TO DETERMINE THE APPLICABILITY OF REGULATORY LIMITATIO
9、NS PRIOR TO USE. EFFECTIVE HEALTH AND SAFETY PRACTICES ARE TO BE FOLLOWED WHEN UTILIZING THIS PROCEDURE. FAILURE TO UTILIZE THIS PROCEDURE IN THE MANNER PRESCRIBED HEREIN CAN BE HAZARDOUS. MATERIAL SAFETY DATA SHEETS (MSDS) OR EXPERIMENTAL MATERIAL SAFETY DATA SHEETS (EMSDS) FOR ALL OF THE MATERIALS
10、 USED IN THIS PROCEDURE SHOULD BE REVIEWED FOR SELECTION OF THE APPROPRIATE PERSONAL PROTECTION EQUIPMENT (PPE). COPYRIGHT 1965, 1980, 1998 UOP LLC ALL RIGHTS RESERVED UOP Methods are available through ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken PA 19428-2959, United St
11、ates. The Methods may be obtained through the ASTM website, www.astm.org, or by contacting Customer Service at serviceastm.org, 610.832.9555 FAX, or 610.832.9585 PHONE. 2 of 10 621-98 APPARATUS References to catalog numbers and suppliers are included as a convenience to the method user. Other suppli
12、ers may be used. Balance, readability 0.1-mg Chromatographic column, 50 m of 0.2-mm ID fused silica capillary, internally coated to a film thickness of 0.5-m with cross-linked methyl silicone, Hewlett Packard, Cat. No. 19091S-001 Gas chromatograph, capable of constant pressure mode and multiple temp
13、erature ramping, built for capillary column chromatography, utilizing a split injection system, having a glass injection port insert, and equipped with a FID that will give a minimum peak height response of 10 times the background noise for 0.05 mass-% of n-decane, when operated at the recommended c
14、onditions, Hewlett Packard, Model 6890 Gas purifier, hydrogen, used to remove oxygen from the carrier gas, UOP Mat/Sen, Cat. No. P-200-1 Integrator, electronic, for obtaining peak areas. This device must integrate areas at a sufficiently fast rate so that the narrow peaks typically resulting from us
15、e of a capillary column can be accurately measured. Leak detector, gas, Alltech Associates, Cat. No. 21-250 Recorder (optional), used to supplement integrator plot Regulator, air, two-stage, high purity, Matheson Gas Products, Model 3122-590 Regulator, hydrogen, two-stage, high purity, Matheson Gas
16、Products, Model 3122-350 Regulator, nitrogen, two-stage, high purity, Matheson Gas Products, Model 3122-580 Sample injector, syringe or injector capable of introducing a 1.0-L volume of sample, such as a SGE Universal Syringe, Fisher Scientific, Cat. No. SG-001105. An autoinjector may be used. REAGE
17、NTS AND MATERIALS All reagents shall conform to the specifications established by the Committee on Analytical Reagents of the American Chemical Society, when such specifications are available, unless otherwise specified. References to catalog numbers and suppliers are included as a convenience to th
18、e method user. Other suppliers may be used. Air, total hydrocarbons less than 2 ppm as methane Benzene, 99.9% purity, Aldrich Chemical, Cat. No. 27,070-9. CAUTION: Benzene is a known carcinogen. All operations involving its use must be performed in a properly ventilated area, while wearing appropria
19、te personal protective equipment. Ethylbenzene, 99.8% purity, Aldrich Chemical, Cat. No. 29,684-8 3 of 10 621-98 Hydrogen, zero-gas, 99.95% minimum purity, total hydrocarbons less than 0.5 ppm as methane Nitrogen, zero-gas, 99.99% minimum purity, total hydrocarbons less than 0.5 ppm as methane n-Par
20、affins, carbon nos. 5 through 20, for blending purposes, 99% minimum purity, Aldrich Chemical. Additional hydrocarbons may be required for calibration purposes. n-Paraffin Cat. No. n-Paraffin Cat. No. C5 27,041-5 C13T5,740-1 C6 13,938-6 C14 17,245-6 C727,051-2 C15P340-6 C841,223-6 C16H670-3 C9N2,940
21、-6 C1712,850-3 C10D90-1 C18O-65-2 C11U40-7 C19N2,890-6 C12D22,110-4 C2021,927-4 Toluene, 99.8% purity, Aldrich Chemical, Cat. No. 27,037-7 m-Xylene, 99% minimum purity, Aldrich Chemical, Cat. 18-556-6 o-Xylene, 97% minimum purity, Aldrich Chemical, Cat. No. X104-0 p-Xylene, 99% minimum purity, Aldri
22、ch Chemical, Cat. No. 13,444-9 PROCEDURE Chromatographic Technique 1. Install the gas purifier in the supply line between the carrier gas source and the carrier gas inlet on the gas chromatograph. Column life is significantly reduced if the gas purifier is not used. 2. Install the fused silica capil
23、lary column in the gas chromatograph, according to the column and gas chromatograph manufacturers instructions. CAUTION: Hydrogen gas leakage into the confined volume of the column oven can cause a violent explosion. It is, therefore, mandatory to check for leaks each time a connection is made and p
24、eriodically thereafter. 3. Establish the recommended operating conditions as given in Table 1. Other conditions may be used provided they produce the required sensitivity and chromatographic separations equivalent to those shown in the Typical Chromatograms (Figs. 1, 2, and 3). 4. Program the column
25、 oven to 300C and maintain this temperature until a stable baseline has been obtained at the required sensitivity. 5. Cool the column oven to a stabilized 100C. 6. Mix the sample thoroughly by shaking it vigorously. 4 of 10 621-98 7. Inject 1.0 L of sample into the gas chromatograph and immediately
26、start the recorder, the integrator and the column oven programming sequence. 8. Identify the components of interest by comparing the resultant chromatogram to the corresponding Typical Chromatogram, Fig. 1, Fig. 2 or Fig. 3. In determining the composite area of the components within a given carbon n
27、umber boiling point value (Fig. 1), start area measurements immediately after the n-paraffin peak of the previous carbon number; that is, one carbon less, and continue up to the end of the n-paraffin peak of the boiling point value under consideration. In this manner, a distribution by boiling point
28、, or by approximate carbon number, is determined. All material thus measured should be considered as the higher of the two n-paraffin carbon numbers for approximate carbon number identification. Single ring aromatics elute one carbon number later than n-paraffins of the same carbon number (Fig. 3).
29、Two ring aromatics elute approximately two carbon numbers later than n-paraffins of the same carbon number (Fig. 3). Table 1 Recommended Operating Conditions Carrier gas hydrogen Column head pressure 100C, constant pressure mode 105 kPa gauge (15 psig) Equivalent flow 0.6 mL/min Equivalent linear ve
30、locity 24 cm/sec Split flow 150 mL/min Injection port temperature 250C Column temperature program Initial temperature 100C Initial time 1.5 min Programming rate 6C/min Final temperature 300C Final time 10.5 min Detector FID Temperature 275C Hydrogen flow rate* 30 mL/min Air flow rate* 400 mL/min Mak
31、eup nitrogen flow rate* 30 mL/min Sample size 1.0 L * Consult the manufacturers instrument manual for suggested flow rates. 5 of 10 621-98 Calibration This analysis uses internal normalization of the entire sample to quantitate the desired components in any given mixture. Since hydrocarbons, except
32、C6to C8aromatics, respond almost equally in the FID on a mass basis, a relative response factor of 1.000 may be used for all components unless the sample contains a significant amount of identified C6to C8aromatics, or when greater accuracy is desired. 1. Prepare a calibration blend as described in
33、ASTM Method D 4307 to contain a representative composition of the sample to be analyzed. 2. Run the calibration blend three times as described in Steps 7 through 8 under Chromatographic Technique. A calibration blend is run when the method is initially set up and thereafter when changes have been ma
34、de to the equipment, or periodically to verify proper calibration or peak identification. 3. Identify the peaks and average the individual peak areas from the triplicate runs. 4. Use the average peak areas to calculate the relative response factor for each component of interest to three decimal plac
35、es, using one of the components as a reference (1.000), and Eq. 1. ABF = CD(1) where: A = concentration of the component of interest (or group) in the blend, mass-% B = average peak area of the reference component C = concentration of the reference component in the blend, mass-% D = average peak are
36、a for the component of interest F = relative response factor for component of interest A blend of n-paraffins, in about equal proportions, is used for designating specific boiling points over a wide range. The boiling points of n-paraffins, from C5through C20, are listed in Table 2. Table 2 Boiling
37、Points of Normal Paraffins n-Paraffin Boiling Point, oC n-Paraffin Boiling Point, oC C536.1 C13235.4 C668.7 C14253.6 C798.4 C15270.6 C8125.7 C16286.8 C9150.8 C17301.8 C10174.1 C18316.1 C11195.9 C19329.7 C12216.3 C20342.7 6 of 10 621-98 CALCULATIONS Calculate the concentration of each component (or g
38、roup) using Eq. 2. =GFComponent (or group), mass- % 100 N(2) where: F = relative response factor for component (or group), Eq. 1 or 1.000, if appropriate G = peak area of individual component (or group) in the sample N = sum of the products GF of all the components in the sample 100 = factor to conv
39、ert to mass-% Report to one significant digit below 0.1 mass-%, two significant digits from 0.1 to 1 mass-%, and three significant digits above 1 mass-%. PRECISION ASTM Repeatability A nested design was carried out for boiling point distribution of hydrocarbons analysis with four analysts. Each anal
40、yst carried out tests on two separate days, performing two tests each day. The total number of tests performed was 16. Using a stepwise analysis of variance procedure, the within-day estimated standard deviations (esds) were calculated for the components listed in Table 3. Two analyses performed in
41、one laboratory by the same analyst on the same day should not differ by more than the ASTM allowable differences shown in Table 3 at the concentrations listed with 95% confidence. UOP Repeatability A nested design was carried out for boiling point distribution of hydrocarbons analysis by four analys
42、ts, with each analyst carrying out tests on two separate days and performing two tests each day. The number of analyses performed was 16. Using a stepwise analysis of variance procedure, the within-lab estimated standard deviations (esds) were calculated for the components listed in Table 3. Two ana
43、lyses performed in one laboratory by different analysts on different days should not differ by more than the UOP allowable differences shown in Table 3 at the concentrations listed with 95% confidence. 7 of 10 621-98 Table 3 ASTM and UOP Repeatability, mass-% ASTM Repeatability UOP Repeatability Com
44、ponent Concentration Within-Day esd Allowable Difference Within-Lab esd Allowable Difference C5Non-aromatics 0.23 0.004 0.01 0.01 0.03 Benzene 26.5 0.03 0.1 0.05 0.2 Toluene 40.7 0.06 0.2 0.10 0.3 C8Aromatics 14.9 0.03 0.1 0.05 0.2 C10 Aromatics 1.05 0.006 0.02 0.005 0.02 Naphthalene 3.13 0.013 0.04
45、 0.015 0.05 C12Aromatics 0.05 0.003 0.01 0.003 0.01 The data in Table 3 were obtained using an autoinjector and are a short-term estimate of repeatability. When the test is run routinely in the field, a control standard and chart should be used to develop a better estimate of the long-term repeatabi
46、lity. Reproducibility There is insufficient data to calculate the reproducibility of the test at this time. TIME FOR ANALYSIS The elapsed time for one analysis is one hour. The labor requirement is 0.25 hour. REFERENCE ASTM Method D 4307, www.astm.org SUGGESTED SUPPLIERS Aldrich Chemical Co., Inc.,
47、P.O. Box 355, Milwaukee, WI 53201 (414-273-3850) Alltech Associates, Inc., 2051 Waukegan Rd., Deerfield, IL 60015 (847-948-8600) Fisher Scientific, 711 Forbes Ave., Pittsburgh, PA 15219 (412-562-8300) Hewlett Packard Co., 2850 Centerville Rd., Wilmington, DE 19808-1610 (302-633-8000) Matheson Gas Pr
48、oducts, Inc., P.O. Box 96, Joliet, IL 60434 (815-727-4848) UOP Mat/Sen, 4509 Golden Foothill Pkwy., El Dorado Hills, CA 95762 (916-939-8800) 8 of 10 621-98 Figure 1 Typical Chromatogram n-Paraffins and Components by Carbon Number9 of 10 621-98 Figure 2 Typical Chromatogram Molex Sample with Desorbent10 of 10 621-98 Figure 3 Typical Chromatogram n-Paraffins and Aromatics
