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4、 PHONE. Total Oxygen in Solid, Semi-solid, and High Boiling Point Liquid Hydrocarbons by Pyrolysis UOP Method 649-10 Scope This method is for determining total oxygen in solid, semi-solid, and high boiling point liquid hydrocarbons at concentrations ranging from approximately 0.1 to 50 mass-%. Sampl
5、ing methods are described for several types of sample matrices. The method determines the total oxygen, including organic oxygen compounds, dissolved water and dissolved molecular oxygen. The contributions of oxygen from water and dissolved molecular oxygen can be measured using other methods (see R
6、eferences below) and subtracted from this result. Volatile liquid samples should be analyzed using UOP Method 730, “Total Oxygen in Liquid Hydrocarbons by Pyrolysis.” References ASTM Method D 1364, “Water in Volatile Solvents (Karl Fischer Reagent Titration Method),” www.astm.org ASTM Method D 4052,
7、 “Density and Relative Density of Liquids by Digital Density Meter,” www.astm.org UOP Method 481, “Water in Liquid Hydrocarbons by Coulometry,” www.astm.org UOP Method 678, “Dissolved Molecular Oxygen in Liquid Hydrocarbons by Electrochemical Detection,” www.astm.org UOP Method 730, “Total Oxygen in
8、 Liquid Hydrocarbons by Pyrolysis,” www.astm.org Outline of Method An oxygen analyzer (CHN/O instrument) is set up and calibrated with liquid standards or solid standards, as required for the sample matrix. Liquid samples are diluted in toluene and directly injected into the pyrolysis reactor in a h
9、elium carrier. Solid or semi-solid samples are sealed in silver foil capsules before introduction into the pyrolysis reactor. Samples are pyrolyzed at a temperature in excess of 1000C. A metalized carbon reagent helps convert all of the oxygen in the sample into carbon monoxide (CO). Acid gas is rem
10、oved from the product stream with an appropriate trap material (soda lime). The pyrolysis product gas is passed through a GC column to separate the CO. The CO content is measured using thermal conductivity detection. 2 of 9 649-10 Apparatus References to catalog numbers and suppliers are included as
11、 a convenience to the method user. Other suppliers may be used. Balance, readability 0.1-mg Capsule press, CE Elantech, Cat. No. 205-030-02 CHN/O Analyzer, Thermo Scientific, Model FLASH 2000, available from CE Elantech. Instrument is equipped with a liquid autosampler and/or a solids autosampler, d
12、epending on the types of samples analyzed. Follow the manufacturers recommendations for maintaining a supply of spare parts and consumables, such as autosampler vials. Any use of an alternative instrument must be tested to determine if it provides equivalent sensitivity and precision. Flasks, volume
13、tric, Class A, borosilicate glass, 10-, 25-, and 50-mL, Fisher Scientific, Cat. Nos. 20-812D, 10-210-8A, and -8B, respectively Hot plate, Fisher Scientific, Cat. No. 11-100-16H Microbalance, readability 1-g, Mettler-Toledo, Model MX5. The microbalance is normally purchased with the instrument and co
14、nfigured to automatically transfer the sample weights to the instrument control program. Pipet, automatic delivery with disposable plastic tips, 20L, Fisher Scientific, Cat. No. 21-377-817 Pipet, volumetric, Class A, 1-, 2-, 5- and 10-mL, Fisher Scientific, Cat. No. 13-650-2B, -2C, -2F, and -2L, res
15、pectively Pipet filler, Fisher Scientific, Cat. No. 13-681-51 Regulator, helium, two-stage, high purity, with stainless steel diaphragm, delivery pressure range 30-700 kPa (4-100 psi), Matheson, Cat. No. 3810-580 Syringe, gastight, 250-L, CE Elantech, Cat. No. 365-040-42 Reagents and Materials Refer
16、ences to catalog numbers and suppliers are included as a convenience to the method user. Other suppliers may be used. References to water mean deionized or distilled water. The following items are required to perform the analysis. Additional reagents and materials may be required depending on the sp
17、ecific oxygen analyzer utilized. Where different reagents are specified in the instrument manual, follow the manufacturers recommendations. BBOT (2,5-Bis(5-tert-butyl-benzoxazol-2-yl)thiophene), CE Elantech, Cat. No. 338-352-10. For calibration, nominal oxygen content 7.43 mass-%. Certificate of Ana
18、lysis sent with material. Benzoic acid, Aldrich, Cat. No. 242381-100G. For calibration, nominal oxygen content 26.2 mass-%. Certificate of Analysis sent with material. Cystine, CE Elantech, Cat. No. 338-400-18. For calibration, nominal oxygen content 26.6 mass-%. Certificate of Analysis sent with ma
19、terial. Helium, compressed gas, 99.999% minimum purity, such as Matheson Ultra High Purity. Magnesium perchlorate (anhydrone), CE Elantech, Cat. No. 338-219-00 Methionine, CE Elantech, Cat. No. 338-352-20. For calibration, nominal oxygen content 21.5 mass-%. Certificate of Analysis sent with materia
20、l. 3 of 9 649-10 Nickel coated carbon, CE Elantech, Cat. No. 338-238-00 Pipet, transfer, disposable plastic, 152-mm length, Fisher Scientific, Cat. No. 13-711-SA Quartz turnings, CE Elantech, Cat. No. 338-223-10 Quartz wool, CE Elantech, Cat. No. 338-222-50 Silver capsules for liquids, CE Elantech,
21、Cat. No. 240-051-00 Silver foil capsules, CE Elantech, Cat. No. 240-054-00 Soda lime, CE Elantech, Cat. No. 338-352-30 Toluene, anhydrous, Burdick otherwise troubleshoot the leak before proceeding. Calibration of Apparatus Part A Liquid Calibration 1. Select the appropriate calibration standards for
22、 a linear calibration over the range of interest. It is recommended to include at least 3 standards and a solvent blank (anhydrous toluene). Follow instrument manufacturers guidelines to determine maximum injectable volume. 5 of 9 649-10 The linear calibration is made from injections of the same vol
23、ume of standards of different concentrations. It is recommended that an autosampler be used with the instrument. The sample must be completely injected into the pyrolysis reactor. Small volumes and/or slow injection rates can result in a loss of sample to the walls of the pyrolysis reactor, resultin
24、g in a bias to lower results. The use of larger injection volumes shortens the useful life of the pyrolysis reactor. The injection of 20-30 L from a 250L syringe is the best compromise for meeting the analytical requirements while maximizing the reactor life. 2. Create a calibration program sequence
25、 in the instrument control software. The solvent blank and the standards on the calibration sequence should be analyzed in duplicate. 3-5 injections of anhydrous toluene should be made before starting the calibration to condition the pyrolysis reactor. The injections of the anhydrous toluene and low
26、est standard should repeat within 20% relative, and the standards above 0.02% O, within 10% relative. If not, check the equipment and procedures. 3. Fill autosampler vials with the standards using disposable transfer pipets. Place the samples in the appropriate positions on the autosampler. 4. Run t
27、he calibration sequence according to manufacturers instructions. 5. Once completed, check the calibration line. If a single injection of a standard is off of the calibration line (the CF reported by the data system is less than 0.99), re-analyze that standard. If the chromatograms show excessive tai
28、ling, the pyrolysis reactor will need to be repacked. See Preparation of Apparatus, Step 1. If tailing still occurs, consult the instrument manual for other possible causes and remedies. Inspect the peaks on the chromatogram. On occasion the data system will miss or incorrectly measure the CO peak.
29、The solvent blanks and low standards may require reintegration and recalculation. Part B Solid Calibration 1. Select the appropriate calibration standards for a linear calibration over the range of interest. Typically, three or more standards and a blank are run. BBOT (nominally 7.43 mass-% O) is re
30、commended for 0.1 10% oxygen calibration Calibrations above 10% oxygen should use a high level standard, such as benzoic acid (nominally 26.2 mass-% O), methionine (nominally 21.5 mass-% O), or cystine (nominally 26.6 mass-% O) as part of the calibration set. Samples containing more than 30% water s
31、hould be analyzed using a calibration curve with deionized water (88.81 mass-% O) as the oxygen standard. 2. Create a calibration program sequence in the instrument control software. 2 or 3 empty silver capsules (either hard or foil) should be analyzed at the start of the calibration sequence. Silve
32、r capsules serve to condition the instrument and serve as the instrument blank value. The standard should repeat within 10% relative. If not, check the equipment and procedures. 3. Weigh the standard into the silver capsules over the range of 0.1 to 10 mg. Solid materials are weighed in silver foil
33、capsules. For samples containing high amounts of water, the deionized water calibrant should be dispensed into tared hard silver capsules, purged with helium and then crimp sealed before weighing (see Note 2). 6 of 9 649-10 4. Run the calibration sequence according to manufacturers instructions. 5.
34、Once completed, check the calibration line. If a single measurement of a standard is off of the calibration line (the CF reported by the data system is less then 0.99), re-analyze that standard. If the chromatograms show excessive tailing, the pyrolysis reactor will need to be repacked. See Preparat
35、ion of Apparatus, Step 1. If tailing still occurs, consult the instrument manual for other possible causes and remedies. Inspect the peaks on the chromatogram. On occasion the data system will miss or incorrectly measure the CO peak. The solvent blanks and low standards may require reintegration and
36、 recalculation. Sample Analysis Benzoic acid in anhydrous toluene can be used to calibrate up to 1% oxygen in samples (see Note 1). If the result for the diluted portion of the sample is less than 0.02% oxygen or greater than 1% oxygen, re-dilute and reanalyze. Part A - Dilution Procedure for Liquid
37、 Samples 1. Calibrate the instrument using 1% oxygen standard as the highest point on the calibration line. 2. Using a volumetric pipet, add 2.00 mL of sample to a 10-mL volumetric flask. If diluting by mass, use approximately 2 g of sample measured to the nearest 0.1 mg. 3. Dilute the sample to the
38、 mark with anhydrous toluene and shake the flask well to mix. 4. Fill an autosampler vial with diluted sample using a disposable transfer pipet. 5. Set up the sample program to analyze the samples. 6. Follow the procedure recommended by the manufacturer for the analysis of the sample. Sample analysi
39、s is generally performed at least in duplicate; 3 or 4 replicate injections are recommended. Average the results. The repeatability of the replicates should be within the precision of the method. If they are not, look for air bubbles in the syringe or other instrument malfunction. The sample must be
40、 completely injected into the pyrolysis reactor. Small volumes and/or slow injection rates can result in a loss of sample to the walls of the pyrolysis reactor, resulting in a bias to lower results. 1 or 2 conditioning blanks should be injected before the first sample if the instrument has been idle
41、 for longer than 30 minutes. 7. A QC sample should be analyzed before and after the set of samples to check instrument stability. A benzoic acid in toluene solution made at a concentration not used for calibration can be used as a QC. This solution should be prepared each week. Part B - Capsule Proc
42、edure for Solid Samples 1. Calibrate the instrument using solid organic standards, such as BBOT or methionine, depending on the concentration range of the samples. 2. Samples should be ground to a fine powder or chipped into small pieces. 3. Tare the capsule. 4. Add the sample to the silver foil cap
43、sule. Fold the capsule to exclude air before weighing. 7 of 9 649-10 Weigh 5 10 mg of sample. 5. Weigh the sample in the tared capsule and enter the weight on the sample table. 6. Repeat steps 3 5 for this sample for a duplicate analysis. If the sample is non-homogeneous, analyze a third portion. 7.
44、 Repeat these steps for all remaining samples. 8. Follow the procedure recommended by the manufacturer for the analysis of the sample. Sample analysis is generally performed at least in duplicate. Average the results of all the analyses performed. The repeatability of the replicates should be within
45、 the precision of the method. 1 or 2 conditioning blanks (empty silver capsules) should be analyzed before the first sample, if the instrument has been idle for longer than 30 minutes. 9. A QC sample should be analyzed before and after the set of samples to check instrument stability. The QC materia
46、l should be a different compound than the one used for calibration. Part C - Capsule Procedure for Semi-solid and Low Melting Point Solids 1. Calibrate the instrument using solid organic standards, such as BBOT or methionine, depending on the concentration range of the samples. 2. Warm the samples o
47、n a hot plate until melted, then cap and mix thoroughly. 3. Unfold the silver foil capsule until nearly flat. Tare the capsule. 4. Add a drop of the sample to the foil capsule near the center. Weigh 5 10 mg of sample. 5. Allow the drop of sample to cool to room temperature and solidify. 6. Fold the
48、foil in half, then fold in from each side and then finally fold down the top of the foil capsule to make a sealed packet. 7. Weigh the sample in the tared capsule and enter the weight on the sample table. 8. Repeat steps 3 7 for this sample for a duplicate analysis. If the sample is non-homogeneous,
49、 analyze a third portion. 9. Repeat these steps for all remaining samples. 10. Follow the procedure recommended by the manufacturer for the analysis of the sample. Sample analysis is generally performed at least in duplicate. Average the results. The repeatability of the replicates should be within the precision of the method. 1 or 2 conditioning blanks (empty silver capsules) should be analyzed before the first sample if the instrument has been idle for longer than 30 minutes. 11. A QC sample should be analyzed
