1、 IT IS THE USERS RESPONSIBILITY TO ESTABLISH APPROPRIATE PRECAUTIONARY PRACTICES AND TO DETERMINE THE APPLICABILITY OF REGULATORY LIMITATIONS PRIOR TO USE. EFFECTIVE HEALTH AND SAFETY PRACTICES ARE TO BE FOLLOWED WHEN UTILIZING THIS PROCEDURE. FAILURE TO UTILIZE THIS PROCEDURE IN THE MANNER PRESCRIB
2、ED HEREIN CAN BE HAZARDOUS. MATERIAL SAFETY DATA SHEETS (MSDS) OR EXPERIMENTAL MATERIAL SAFETY DATA SHEETS (EMSDS) FOR ALL OF THE MATERIALS USED IN THIS PROCEDURE SHOULD BE REVIEWED FOR SELECTION OF THE APPROPRIATE PERSONAL PROTECTION EQUIPMENT (PPE). COPYRIGHT 1980, 1990, 1996, 2013 UOP LLC. All ri
3、ghts reserved. Nonconfidential UOP Methods are available from ASTM International, 100 Barr Harbor Drive, P.O. Box C700, West Conshohocken, PA 19428-2959, USA. The UOP Methods may be obtained through the ASTM website, www.astm.org, or by contacting Customer Service at serviceastm.org, 610.832.9555 FA
4、X, or 610.832.9585 PHONE. Trace p-DEB or Indan in C8 Aromatics and Trace C8 Aromatics in p-DEB by GC UOP Method 798-13 Scope This gas chromatographic method is for determining trace amounts of p-diethylbenzene (p-DEB) or trace amounts of indan as impurities in C8 and lower boiling aromatic streams.
5、High levels of other C9 or C10 aromatics may interfere with the determination of trace p-DEB and indan in C8 aromatics. The method can also be used for determining trace amounts of C8 aromatics in p-DEB. The C8 aromatic isomers are resolved and determined individually. The lower limit of quantitatio
6、n for p-DEB or indane is 0.5 mass-ppm and for each xylene isomer it is 2 mass-ppm. References ASTM Practice D4307, “Preparation of Liquid Blends for Use as Analytical Standards,” www.astm.org UOP Method 999, “Precision Statements in UOP Methods,” www.astm.org Outline of Method Two gas chromatographi
7、c analyses are required. One set of conditions is used to determine trace p-DEB and indan in C8 aromatics (Analysis A). Different conditions are required to determine trace C8 aromatics in p-DEB (Analysis B). In both analyses, a repeatable volume of sample is injected into a gas chromatograph equipp
8、ed with a fused silica capillary column internally coated with 1,2,3-tris (2-cyanoethoxy) propane (TCEP), and a flame ionization detector. The concentrations of individual impurities are determined by the external standard method of quantitation, wherein peak areas of the sample components are compa
9、red to the peak areas of a calibration blend analyzed under identical conditions and injection volumes. Apparatus References to catalog numbers and suppliers are included as a convenience to the method user. Other suppliers may be used. Balance, readable to 0.0001 g Chromatographic column, 60 m of 0
10、.25-mm ID fused silica capillary, internally coated to a film thickness of 0.4-m with TCEP, Restek, Cat. No. 10999 2 of 11 798-13 Gas chromatograph, temperature programmable, built for capillary column chromatography, utilizing a split injection system having a glass injection port insert, and equip
11、ped with a flame ionization detector that will give a minimum peak height response of 10 times the background noise for one mass-ppm of p-DEB when operated at the recommended conditions, Agilent Technologies, Model 7890A, with autosampler capable of injecting both a repeatable 0.5-L and 1.0-L volume
12、 of sample, Agilent Technologies, Model 7693A Data system, electronic, for obtaining peak areas. This device must integrate areas at a sufficiently fast rate so that narrow peaks, typically resulting from use of a capillary column, can be accurately measured. Agilent Technologies, ChemStation. Leak
13、detector, gas, Grace Davison, Cat. No. 60229 Refrigerator, flammable-materials storage, Fisher Scientific, Cat. No. 97-938-1 Regulator, air, two-stage, high purity, delivery pressure range 30-700 kPa (4-100 psi), Matheson Tri-Gas, Model 3122-590 Regulator, hydrogen, two-stage, high purity, delivery
14、pressure range 30-700 kPa (4-100 psi), Matheson Tri-Gas, Model 3122-350 Regulator, nitrogen, two-stage, high purity, delivery pressure range 30-700 kPa (4-100 psi), Matheson Tri-Gas, Model 3122-580 Reagents and Materials References to catalog numbers and suppliers are included as a convenience to th
15、e method user. Other suppliers may be used. Air, zero gas, total hydrocarbons less than 2.0 ppm as methane Decane, 99% minimum purity, Sigma-Aldrich, Cat. No. D901 p-Diethylbenzene (1,4-diethylbenzene or p-DEB), 96% minimum purity, Sigma-Aldrich, Cat. No. D91004 Ethylbenzene, 99.8% minimum purity, S
16、igma-Aldrich, Cat. No. 296848 Gas purifier, for hydrogen, to remove oxygen and moisture from carrier gas, VICI Mat/Sen, Cat. No. P200-1, and (optional) indicating oxygen trap, Restek, Cat. No. 22010, see Procedure, Chromatographic Technique, Step 1 Hydrogen, zero gas, 99.99% minimum purity, total hy
17、drocarbons less than 0.5 ppm as methane Indan, 95% minimum purity, Sigma-Aldrich, Cat. No. I1804 Nitrogen, zero gas, 99.99% minimum purity, total hydrocarbons less than 0.5 ppm as methane Pipets, disposable, Pasteur, VWR, Cat. No. 14673-043 Pipet bulbs, VWR, Cat. No. 15001-362 Syringe, replacement,
18、for recommended autosampler, 5-L, Agilent Technologies, Cat. No. 5181-1273 Vials, 22- and 30-mL, with polyseal-lined caps, VWR, Cat. Nos. 16087-068 and -058, respectively Vials, autosampler, for recommended sample injector, with caps, Agilent Technologies, Cat. No. 5182-0864 m-Xylene (1,3-dimethylbe
19、nzene), 99% minimum purity, Sigma-Aldrich, Cat. No. 296325 3 of 11 798-13 o-Xylene (1,2-dimethylbenzene), 99.0% minimum purity, Sigma-Aldrich, Cat. No. 95662 p-Xylene (1,4-dimethylbenzene), 99.0% minimum purity, Sigma-Aldrich, Cat. No. 95682 Procedure The analyst is expected to be familiar with gene
20、ral laboratory practices, the technique of gas chromatography, and the equipment being used. Dispose of used reagents, materials, and samples in an environmentally safe manner according to local regulations. Chromatographic Technique 1. Install the gas purifier in the supply line between the carrier
21、 gas source and the carrier gas inlets on the gas chromatograph. Column life is significantly reduced if the gas purifier is not used. Replace the gas purifier at intervals determined by good laboratory practice. An indicating oxygen trap may be placed downstream of the gas purifier. When the indica
22、tor shows one-half used, replace both the gas purifier and the indicating trap. 2. Install the fused silica capillary column in the gas chromatograph according to the column and gas chromatograph manufacturers instructions. CAUTION: Hydrogen leakage into the confined volume of the column oven can ca
23、use a violent explosion. Therefore, it is mandatory to check for leaks each time a connection is made and periodically thereafter. 3. Establish the recommended operating conditions as given in Table 1. Different conditions may be used provided they produce the required sensitivity and chromatographi
24、c separations equivalent to those shown in the Typical Chromatograms (see Figures 1 - 4). Table 1 Recommended Operating Conditions Analysis A Analysis B Trace p-DEB/Indan Trace C8 Aromatics Carrier gas hydrogen hydrogen Mode constant flow constant flow Flow rate 1.6 mL/min 1.8 mL/min Head pressure 1
25、39 kPa (20.2 psig) 120C 121 kPa (17.5 psig) 50C Linear velocity 40 cm/sec 120C 40 cm/sec 50C Split flow 50 mL/min 90 mL/min Injection port temperature 200C 200C Column temperature program Initial temperature 120C 50C Initial time 6 min 20 min Programming rate 10C/min 10C/min Final temperature 130C 1
26、30C Final time 15 min 15 min Detector Temperature 250C 250C Hydrogen flow ratea 30 mL/min 30 mL/min Air flow ratea 400 mL/min 400 mL/min Makeup gas nitrogen nitrogen Makeup gas flow ratea 30 mL/min 30 mL/min Sample size 1.0 L, repeatable 0.5 L, repeatable aConsult the manufacturers instrument manual
27、 for suggested flow rates. 4 of 11 798-13 4. Program the column oven to 130C (see Table 1) and maintain this temperature until a stable baseline has been obtained at the required sensitivity. 5. Cool the column oven to a stabilized initial temperature according to the analysis being performed. 6. Mi
28、x the sample by shaking. Fill an autosampler vial with an aliquot of the sample and place it in the autosampler tray. Multiple samples may be prepared in advance for unattended operation. 7. Inject nominally 0.5-L or 1.0-L (repeatable) of sample into the gas chromatograph, according to the analysis
29、being performed (see Table 1), and start the data system and the column oven programming sequence. The use of an autosampler automates the injection of the sample into the GC, starts the data system, and the GC oven program simultaneously. 8. Identify the components in the resultant chromatogram and
30、 determine the areas of the impurity peaks. Typical chromatograms are shown in Figures 1 and 3 with expanded regions shown in Figures 2 and 4. Calibration Analysis A Quantitative results are based on the injection of repeatable volumes of both the calibration blend and the sample. Absolute response
31、factors, derived from the calibration blend, are used to relate the peak areas of each known component to mg/kg. 1. Prepare 10 g or more of the Analysis A stock solution as described in ASTM Practice D4307, “Preparation of Liquid Blends for Use as Analytical Standards,” to contain approximately 1.0
32、mass-% each of p-DEB and indan in p-xylene, by weight. Thoroughly mix the solution by shaking. Record all weights to the nearest 0.0001 g. Obtain the purest p-xylene possible to prepare the blend. Analyze it, looking for impurities that elute at the p-DEB and indan sites. If an impurity in the p-xyl
33、ene is present, obtain p-xylene from a different vendor and check for the impurity. If no p-xylene can be found without an impurity at the p-DEB and indan sites, correct for the impurity as described in ASTM Practice D4307. 2. From the recorded weights, calculate the concentrations of each of the an
34、alytes in the Analysis A stock solution to three significant figures using Equation 1 or the procedure described in ASTM Practice D4307: A = CB100 (1) where: A = concentration of each analyte in the Analysis A stock solution, mass-% B = mass of each analyte in the Analysis A stock solution, g C = to
35、tal mass of the Analysis A stock solution prepared, g 100 = factor to convert to mass-% 3. Prepare 10 g or more of the Analysis A intermediate blend solution containing approximately 1.0 mass-% of the Analysis A stock solution in p-xylene. Thoroughly mix the solution by shaking. Record all weights t
36、o the nearest 0.0001 g. 4. From the recorded weights, calculate the concentrations of each of the analytes in the Analysis A intermediate blend solution to three significant figures using Equation 2 or the procedure described in ASTM Practice D4307. The intermediate blend solution should contain app
37、roximately 0.01 mass-% each of p-DEB and indan in p-xylene. 5 of 11 798-13 D = FEA (2) where: A = concentration of each analyte in the Analysis A stock solution, from Equation 1, mass-% D = concentration of each analyte in the Analysis A intermediate blend solution, mass-% E = mass of the Analysis A
38、 stock solution, g F = total mass of the Analysis A intermediate blend solution prepared, g 5. Prepare 10 g or more of the Analysis A calibration blend containing approximately 5.0 mass-% of Analysis A intermediate blend solution in p-xylene. Thoroughly mix the solution by shaking. Record all weight
39、s to the nearest 0.0001 g. If refrigerated, the stock solution, secondary blend solution and calibration blend should remain stable for six months. If the response factors change more than 10% from when the blend was initially prepared and analyzed, prepare and use a new stock solution, secondary bl
40、end solution and calibration blend. 6. Calculate the concentration of p-DEB and indan in Analysis A calibration blend to the nearest mg/kg using Equation 3 or the procedure described in ASTM Practice D4307. Using the above dilutions, the resulting Analysis A calibration blend should contain approxim
41、ately 5 mg/kg of each added component. J = IHGD104 + (3) where: D = concentration of each analyte in the Analysis A intermediate blend solution, from Equation 2, mass-% G = mass of the Analysis A intermediate blend solution in the calibration blend, g H = total mass of the Analysis A calibration ble
42、nd solution prepared, g I = concentration of p-DEB or indan, if any, in the p-xylene, mg/kg J = concentration of p-DEB or indan in the calibration blend, mg/kg 104 = factor to convert mass-% to mg/kg 7. Analyze the calibration blend in triplicate daily when samples are analyzed as described under Ch
43、romatographic Technique. The peak areas from each of the triplicate runs should not deviate from the average by more than 2% (relative) of the value. If greater deviations occur, make certain that there are no problems with the equipment and then make additional runs until the required repeatability
44、 is obtained on three consecutive runs. Confirm the stability of the chromatographic system by analyzing the calibration blend again at the end of a daily series of analyses. If the results differ by more than 5% from the average of the triplicate runs, a problem has developed with the chromatograph
45、ic system and the series of samples must be rerun after the problem is resolved. Typical problems to look for include a leaky septum and a dirty or partially plugged syringe. 8. Use the average peak areas to calculate the absolute response factor for p-DEB and indan in p-xylene, by weight, to three
46、significant figures, using Equation 4. L = KJ (4) where: L = absolute response factor for p-DEB or indan J = concentration of p-DEB or indan in the calibration blend, from Equation 3, mg/kg K = average peak area for p-DEB or indan in the calibration blend 6 of 11 798-13 Calibration Analysis B Quanti
47、tative results are based on the injection of repeatable volumes of both the calibration blend and the sample. Absolute response factors, derived from the calibration blend, are used to relate the peak areas of each known component to mg/kg. 1. Prepare 10 g or more of the Analysis B stock solution as
48、 described in ASTM Practice D4307, “Preparation of Liquid Blends for Use as Analytical Standards,” to contain approximately 1.0 mass-% each of ethylbenzene, m-xylene, o-xylene and p-xylene in decane, by weight. Thoroughly mix the solutions by shaking. Record all weights to the nearest 0.0001 g. Obta
49、in the purest decane possible to prepare the blend. Analyze it, looking for impurities that elute at the ethylbenzene, m-xylene, o-xylene and p-xylene sites. If an impurity in the decane is present, obtain decane from a different vendor and check for the impurity. If no decane can be found without an impurity at the ethylbenzene, m-xylene, o-xylene and p-xylene sites, correct for the impurity as described in ASTM Practice D4307. 2. From the recorded weights, calculate the concentrations of each of the analytes in the Analysis B s
