UOP 1006-2014 Trace Silicon in Petroleum Liquids by ICP-MS.pdf

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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. SAFETY DATA SHEETS (SDS) OR EXPERIMENTAL SAFETY DATA SHEETS (ESDS) FOR ALL OF THE MATERIALS USED IN THIS PROCEDURE SHOULD BE REVIEWED FOR SELECTION OF THE APPROPRIATE PERSONAL PROTECTION EQUIPMENT (PPE). COPYRIGHT 2014 UOP LLC. All rights reserved. Nonconfidential UOP Met

3、hods are available from ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States. The UOP 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. Trac

4、e Silicon in Petroleum Liquids by ICP-MS UOP Method 1006-14 Scope This method is for the determination of silicon (Si) in petroleum liquids using an Inductively Coupled Plasma - Mass Spectrometer (ICP-MS). Silicon is typically present in petroleum liquids as soluble organic silicones, but the method

5、 will also detect other forms of silicon such as the generally insoluble inorganic silicon salts and silica. The method is primarily used to analyze reformer charge stocks for silicones, but may also be used for refinery charge stocks as heavy as vacuum gas oil (VGO). The lower limit of quantitation

6、 is less than 0.1 mg/kg (mass-ppm) as silicon. Less sensitive tests for trace silicon are UOP Method 796, “Silicon in Petroleum Liquids by ICP-OES,” (to 1 mg/kg) and ASTM Method D7757, “Silicon in Gasoline and Related Products by Monochromatic Wavelength Dispersive X-ray Fluorescence Spectrometry,”

7、(to 3 mg/kg). References ASTM Specification D1193, “Reagent Water,” www.astm.org ASTM Practice D7455, “Sample Preparation of Petroleum and Lubricant Products for Elemental Analysis,” www.astm.org ASTM Method D7757, “Silicon in Gasoline and Related Products by Monochromatic Wavelength Dispersive X-ra

8、y Fluorescence Spectrometry,” www.astm.org ASTM Practice D7876, “Sample Decomposition Using Microwave Heating (With or Without Prior Ashing) for Atomic Spectroscopic Elemental Determination in Petroleum Products and Lubricants,” www.astm.org UOP Method 796, “Silicon in Petroleum Liquids by ICP-OES,”

9、 www.astm.org UOP Method 999, “Precision Statements in UOP Methods,” www.astm.org Outline of Method The sample is treated intially with water and nitric acid to reduce the volatility of silicon, followed by hydrofluoric acid, after which the samples are digested. The digestate is quantitatively tran

10、sferred to an autosampler tube using purified water. Indium is added as a monitoring standard and the mixture is diluted to the desired volume. The concentration of silicon in the resulting solution is determined by ICP-MS. 2 of 11 1006-14 Apparatus References to catalog numbers and suppliers are in

11、cluded as a convenience to the method user. Other suppliers may be used. Balance, readable to 0.0001 g Beaker, PTFE, 600-mL, Fisher Scientific, Cat. No. 02-586-1K Bottles, polypropylene, narrow mouth, screw cap, 125-mL, VWR, Cat. No. 16067-066 Bottle, wash, VWR, Cat. No. 2402-0500, for deionized wat

12、er Cover, PTFE, Milestone, Cat. No. MCL0435, with o-ring, Cat. No. OR0138, used to cover the stainless steel vessel in the microwave oven Cylinders, graduated, Class B, 5-, 10-, 25-, and 100-mL, VWR, Cat. Nos. 14201-610, -462, -364, and -718, respectively Flasks, volumetric, polypropylene, Class B,

13、25-, 50-, 100-, and 1000-mL, VWR, Cat. Nos. 83008-964, -974, -984, and 83009-008, respectively; several of each required Fume hood Hot plate, VWR, Cat. No. 11301-006 ICP-MS, PerkinElmer, DRC-e, equipped with an AS10 autosampler Microwave oven, 15-vessel capacity, with closed digestion vessels, quart

14、z tubes and lids, CryoLab chiller, and computer, Milestone, UltraWAVE Pipet, automatic, 10-100-L, VWR, Cat. No. 89079-968; calibrated and/or certified according to manufacturers recommendations Pipet, automatic, 100-1000-L, VWR, Cat. No. 89079-974; calibrated and/or certified according to manufactur

15、ers recommendations Pipet, electronic, 110-mL, EDP 3-Plus, Rainin, Cat. No. SE3-10mL; calibrated and/or certified according to manufacturers recommendations Regulator, argon or nitrogen, two-stage, high purity, delivery pressure range 30-700 kPa (4-100 psi), Matheson Tri-Gas, Model 3122-580 Timer, c

16、apable of timing two hours, VWR, Cat. No. 62344-440 Watch glass, PTFE, 125-mm, Fisher Scientific, Cat. No. 02-617-1F Reagents and Materials References to catalog numbers and suppliers are included as a convenience to the method user. Other suppliers may be used. Unless otherwise specified, reference

17、s to water mean deionized water. Argon, 99.995% minimum purity Cleaning compound, Alconox detergent, VWR, Cat. No. 21835-032 Dry ice Gloves, neoprene/natural rubber, VWR, Cat. No. 32917-212 (size 10) Gloves, Viton, VWR, Cat. No. 89236-768 (size 10) Hydrofluoric acid, concentrated, trace metals grade

18、, VWR, Cat. No. EM-HX0628-7 3 of 11 1006-14 Hydrogen peroxide, 29-32%, VWR, Cat. No. VW3690-5 Indium metal solution, aqueous, 1000-g/mL, SPEX CertiPrep, Cat. No. PLIN2-2X, for use as a monitoring solution Indium metal stock solution, aqueous, 100-g/mL. To prepare 50 mL, pipet 5 mL of the 1000-g/mL i

19、ndium metal solution into a 50-mL volumetric flask. Fill to the mark with deionized water. Cap and invert several times to mix. The solution should remain stable for two months. Indium monitoring standard solution, 10-g/mL. To prepare 100 mL, pipet 10.0 mL of the 100-g/mL indium metal stock solution

20、 into a 100-mL volumetric flask. Fill to the mark with deionized water. Cap and invert several times to mix. Store in a 125-mL polypropylene bottle. The solution should remain stable for two months. Lubricant, dry spray, PTFE, W. W. Grainger, Cat. No. 4JB33, or local supply Nitric acid, concentrated

21、, trace metals grade, VWR, Cat. No. EM-NX0408-2 Nitric acid, 2%. Pipet 20 mL of concentrated nitric acid into a 1000-mL volumetric flask containing 800 mL of deionized water; fill to mark with deionized water. Cap and invert several times to mix. Nitrogen, 99.995% minimum purity, optional, see Micro

22、wave Digestion, Step 6 O-rings, replacement, for microwave oven, Milestone, Cat. No. OR0159 O-ring, top of chamber, replacement, Milestone, Cat. No. OR0170 Pipet, glass, dropping, VWR, Cat. No. 52950-206 Pipet tips, 10-mL, Rainin, Cat. No. RC-10 mL Pipet tips, 1-200-L, VWR, Cat. No. 53508-810 Pipet

23、tips, 100-1250-L, VWR, Cat. No. 53508-922 Silicon standard solution, 1000-g/mL, SPEX CertiPrep, Cat. Nos. PLSi9-2X. Sulfuric acid, concentrated, trace metals grade, VWR, Cat. No. EM-SX1248-6 Towels, paper, disposable, local supply Tubes, autosampler, 50 mL, with caps, PerkinElmer, Cat. No. BO193234

24、Vials, PTFE, 15-mL, Milestone, Cat. No. HB00086, with caps, Cat. No. DD00134 Water, deionized, ASTM D1193 Type III reagent grade water, unless otherwise specified Water, hot, tap Wipers, Kimwipes Ex-L, VWR, Cat. No. 21905-026 The following materials are not required to perform the analyses described

25、 herein and are not cited in the Procedure portion of the method. However, they may be useful for reference purposes, for verification of instrument performance, or as an aid in instrument maintenance. Kerosene solvent, metals free, VWR, Cat. No. AA36447-K7 or SPEX, Cat. No. KER-BLK-G Reference mate

26、rial, SPEX CertiPrep 23 Multi-Element Standard, 100-g/g (mg/kg) each, SPEX CertiPrep, Cat. No. S23 1004. Dilute by weight in kerosene to 10 g/g. Alternatively, a reference standard for silicon may be prepared using polydimethylsiloxane as described in the Appendix. 4 of 11 1006-14 Procedure The anal

27、yst is expected to be familiar with general laboratory practices, the technique of ICP-MS, and the equipment being used. Additional information regarding sample preparation may be found in ASTM Practice D7455, “Sample Preparation of Petroleum and Lubricant Products for Elemental Analysis.” Additiona

28、l information regarding the use of microwave digestion for sample decomposition may be found in ASTM Practice D7876, “Sample Decomposition Using Microwave Heating (With or Without Prior Ashing) for Atomic Spectroscopic Elemental Determination in Petroleum Products and Lubricants.” Dispose of all sup

29、plies and samples in an environmentally safe manner according to applicable regulations. CAUTION: All subsequent steps involving additions of reagents and heating of samples must be performed in a properly operating fume hood, and appropriate personal protective equipment must be worn. See the safet

30、y data sheet (SDS) and any local requirements for each material used. Preparation of Standards Standards are required for analytes to be determined. Stock standard solution is prepared first, from which lower level, matrix matched, calibration standard solutions are then prepared. Preparation of Sil

31、icon Stock Standard Solution Prepare stock standard solution of 10-g/mL concentration of silicon as follows: 1. Pipet 1.0 mL of the 1000-g/mL silicon standard solution into a 100-mL polypropylene volumetric flask. 2. Dilute to the mark with deionized water. Label as Stock Standard A. The solution sh

32、ould remain stable for two months. Cleaning of PTFE Vials and Caps Clean the PTFE vials and caps as follows: 1. Place PTFE vials and caps in a 600-mL beaker, cover with 2% nitric acid, and place a watch glass on top of the beaker. 2. Place the beaker on a hot plate. Set the hot plate to 200 C and br

33、ing to a boil. Adjust the temperature of the hot plate to maintain a slow boil. Boil for two hours. 3. Remove the beaker from the hot plate and allow it to cool. 4. Decant the acid and dispose of it in an environmentally safe manner according to applicable regulations. 5. Rinse the PTFE vials, caps,

34、 beaker, and watch glass with deionized water, and air dry. 6. Store the vials and caps in the beaker, covered with the watch glass until needed. Microwave Digestion The blank and the reference are digested in the same manner as the samples. 1. Weigh 0.25-0.30 g of each sample or reference material

35、to the nearest 0.0001 g into the previously cleaned and air dried vials. Using a pipet or graduated cylinder, add 1 mL of water. Using a graduated cylinder, add 1.5 to 2 mL of concentrated nitric acid (HNO3) and 0.3 mL of hydrofluoric acid (HF) to the PTFE vials. 5 of 11 1006-14 2. Prepare an additi

36、onal three vials as digestion acid blanks by adding 1 ml water, 1.5 to 2 ml concentrated nitric acid (HNO3) and 0.3 mL of hydrofluoric acid (HF) to each pre-cleaned, air dried, PTFE vials. One vial is used for preparing the blank, two are used for standard preparation. This is to ensure matrix match

37、ing with the samples. 3. Close the digestion vessels and place them into the sample holder. 4. Set up the microwave as described below. Refer to the UltraWAVE Operator Manual for details. Add the basic load/absorption media as follows: Using graduated cylinders, add 130 mL of water, 5 mL of 30% hydr

38、ogen peroxide, and 2 mL of sulfuric acid into the PTFE vessel that goes into the stainless steel pressure vessel. This acts as absorption media. Ensure that all o-rings are properly cleaned and greased. 5. Check the water level in the CryoLab chiller. 6. Turn on the gas (nitrogen or argon), CryoLab

39、chiller, computer, and UltraWAVE. 7. Program the system using the settings shown in Table 1. Other conditions may be used provided they produce equivalent results. Table 1 Digestion Conditions Nr. t(min) E (w) T1 C T2 C P 1 00:30:00 1500 230 60 150 2 00:35:00 1500 230 60 150 Nr. 1 is for reaching to

40、 the prescribed condition, and Nr. 2 is holding at that condition. 8. Load the samples into the UltraWAVE. 9. Press the down arrow on the touch screen monitor to lower the sample holder to level 1, check that everything is OK, then press the down arrow again to lower it to level 2. At this point the

41、 sample holder is immersed into the absorption media. 10. Manually close the clamps. 11. Check the method and parameters, and then start the run. At the end of the digestion process, after the materials have cooled to 30 C or lower on the readout, open the UltraWAVE clamps, press the up arrow on the

42、 monitor to lift the sample holder, wait for the fumes to exhaust through the vent, and press the up arrow again to lift the sample holder fully. Cover the stainless steel vessel with the PTFE cover to protect it from possible dripping of the acid condensate. 12. Carefully remove the sample holder w

43、ith the PTFE vials and place it on disposable paper towels. 13. Lift each vial from the sample holder and wipe the bottom on a paper towel. Quantitatively transfer the contents of each vial into separate 50-mL autosampler tubes using deionized water as the diluent. 14. Add 80 L of the 10-g/mL indium

44、 monitoring standard solution to each tube containing samples. 15. Fill each tube to the 40 mL mark with water. Cap and invert several times to thoroughly mix the contents. 16. Immediately after use, to avoid corrosion of the UltraWAVEs stainless steel pressure vessel, dispose of the absorption medi

45、a, and rinse with water. Carefully clean and wipe dry other 6 of 11 1006-14 exposed parts. Spray lubricant on a wiper and wipe as described in the UltraWAVE Operator Manual. Also clean the PTFE container and PTFE vials. Preparation of Blank and Calibration Standard Solutions Prepare calibration stan

46、dards and a blank as follows: 1. Into one of the three 50-mL autosampler tubes containing the digestate of the acid blank, pipet 200 L of 10.0-g/mL silicon standard stock solution. Label as calibration standard solution, 50-ng/mL 2. Into a second tube containing the digestate of the acid blank, pipe

47、t 400 L of the 10.0-g/mL silicon standard stock solution. Label as calibration standard solution, 100-ng/mL. The third flask containing the digestate of the acid blank will be used for the blank preparation. (Initially dilute to 25-mL volume and transfer 3 mL of the diluted digestate to another 50-m

48、L tube and 1 drop of HF). The blank can be also prepared by pipetting 0.1 mL of nitric acid and 0.1 mL of hydrofluoric acid into a 50 mL tube containing 25 ml of water. 3. Add 80 L of 10-g/mL indium internal standard solution to each tube. 4. Dilute to the 40-mL mark with water and mix the contents.

49、 ICP-MS Determination of Analytes The ICP-MS is calibrated with prepared standards using the autosampler. Three calibration points are obtained by analyzing a blank, 50- and 100-ng/mL silicon standards. Samples are then analyzed and the 50- and 100-ng/mL standards are reanalyzed as samples at the end of the run. 1. Set up the instrument according to the manufacturers recommended conditions, see Table 2. Table 2 ICP-MS Parameters ICP/MS instrument: Perkin Elmer DRC-e (DRC Mode) Analytes: Si is measured as 44SiO Internal standard: 11