UOP 796-2009 Silicon in Petroleum Liquids by ICP-OES.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. 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 2009 UOP LLC. All rights reserved. Non

3、confidential UOP Methods 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.

4、832.9585 PHONE. Silicon in Petroleum Liquids by ICP-OES UOP Method 796-09 Scope This method is for the determination of silicon (Si) in petroleum liquids using an Inductively Coupled Plasma - Optical Emission Spectrometer (ICP-OES). Silicon (Si) is typically present in petroleum liquids as soluble o

5、rganic silicones, but the method will also detect other forms of silicon (Si) such as the generally insoluble inorganic silicon (Si) 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

6、oil (VGO). The lower limit of quantition is approximately 1.0 mg/kg (mass-ppm) as silicon (Si). Standard addition, as described in the Appendix, may be used to verify the results. Reference UOP Method 999, “Precision Statements in UOP Methods,” www.astm.org Outline of Method The sample is mixed with

7、 an internal standard and diluted in an organic solvent. The sample is then analyzed directly by ICP-OES. Apparatus References to catalog numbers and suppliers are included as a convenience to the method user. Other suppliers may be used. Balance, analytical, capable of weighing to nearest 0.01 g Ba

8、th, ultrasonic, VWR, Cat. No. 21811-820 Centrifuge, if needed, see Procedure, Sample Preparation Gloves, thermal protection, VWR, Cat. No. 32932-270, if needed, see Procedure, Sample Preparation Oven, laboratory, capable of operation at 100C Spatula, VWR, Cat. No. 57952-253, if needed, see Procedure

9、, Sample Preparation 2 of 10 796-09 Spectrometer, ICP-OES, computer controlled, having sufficient resolving power and dispersion to separate the analytical lines in the 160 to 800 nm region. The computer shall be capable of performing background corrections, blank corrections, mass/volume correction

10、s and dilution corrections. A commercial grating spectrometer with a band pass of 0.018 nm or less in the first order is satisfactory. PerkinElmer Optima 5300 V. Reagents and Materials References to catalog numbers and suppliers are included as a convenience to the method user. Other suppliers may b

11、e used. Bottles, 240 mL, amber, with conical polyseal caps, VWR, Cat. No. 14234-032 Dry ice, if needed, see Procedure, Sample Preparation Hexane, VWR, Cat. No. BJ216-1 Pipets, dropper, glass, Fisher, Cat. No. 13-700 Scandium standard, 1000 g/g, in organic media, SPEX, Cat. No. ORG-SC8-2Z, used as an

12、 internal standard, see Notes 1 and 2 Silicon standard, 1000 g/g, in organic media, SPEX, Cat. No. ORG-SI8-2Z, see Notes 1, 2, and 3 Silicone, 100% polydimethylsiloxane (37.87% silicon), Dow Corning, 200 Fluid, 10 cSt, see Note 3 Solvent, kerosene, VWR, Cat. No. AA36447-K7 or SPEX, Cat. No. KER-BLK-

13、G Vials, 20-mL, with conical polyseal caps, VWR, Cat. No. 16087-068 Procedure The analyst is expected to be familiar with general laboratory practices, the technique of ICP-OES, and the equipment being used. Preparation of Standards Because the response of the ICP is linear, two-point standards (cal

14、ibration standard and blank) approximating the concentration of silicon expected in the samples are used. See Note 3. Preparation of Stock Silicon Standards Prepare a nominally 1,000-mg/kg silicon standard from polydimethylsiloxane as follows (see Note 3). If a purchased Si standard is to be used in

15、 place of polydimethylsiloxane, skip this part and proceed with the preparation of the nominally 100- and 10-mg/kg silicon calibration standards below. 1. Weigh 2.64 0.05 g of 100% polydimethylsiloxane (37.87% silicon) into a clean 240-mL bottle and record the weight to the nearest 0.01 g. Add 97.36

16、 0.05 g of kerosene and record the weight to the nearest 0.01 g. Mix by shaking and in an ultrasonic bath. Label as “Stock Silicon Standard A.” It will contain approximately 10,000-mg/kg Si. 2. Weigh 10.00 0.05 g of Stock Silicon Standard A into a clean 240-mL bottle and record the weight to the nea

17、rest 0.01 g. Add 90.00 0.05 g of kerosene and record the weight to the nearest 0.01 g. Mix by shaking and in an ultrasonic bath. Label as “Stock Silicon Standard B.” It will contain approximately 1000-mg/kg Si. 3. Calculate the concentration of silicon (Si) in Stock Silicon Standards A and B using E

18、quations 1 and 2: 3 of 10 796-09 Concentration of silicon (Si), Stock Silicon Standard A, mg/kg =BAA378700+(1) where: A = weight of polydimethylsiloxane from Step 1, g B = weight of kerosene from Step 1, g 378700 = 37.87 x 10000 where: 37.87 = concentration of Si in polydimethylsiloxane, mass-% 1000

19、0 = factor to convert mass-% to mg/kg Concentration of silicon (Si), Stock Silicon Standard B, mg/kg =EDDC+(2) where: C = concentration of Si in Stock Silicon Standard A, from Equation 1, mg/kg D = weight of Stock Silicon Standard A in Step 2, g E = weight of kerosene in Step 2, g Preparation of Sil

20、icon Calibration Standards Prepare nominally 100- and 10-mg/kg Silicon Calibration Standards as follows: 1. Tare a vial to the nearest 0.01 g and add 1.0 0.05 g of the Stock Silicon Standard B or the purchased 1000-g/g silicon standard. Record the weight to the nearest 0.01 g. 2. Add 9.00.05 g of ke

21、rosene and record the weight to the nearest 0.01 g. 3. Label the vial as Silicon Calibration Standard, first dilution. 4. Tare another vial to the nearest 0.01 g and add 1.00.05 g of the first dilution standard. Record the weight to the nearest 0.01 g. 5. Add 9.00.05 g of kerosene and record the wei

22、ght to the nearest 0.01 g. For ICP analysis, the composition of the calibration standard should match the sample as closely as possible, particularly when measuring silicon below 10 mg/kg. If the sample is a light naphtha or gasoline, it may change the characteristics of the plasma, even when dilute

23、d. For such samples, prepare the nominally 10-mg/kg silicon calibration standard by first adding 1.0 g of hexane, and then adding 8.0 g of kerosene. 6. Label the vial as Silicon Calibration Standard, second dilution. 7. Fill an additional vial with kerosene and label it as Solvent Blank. For ICP ana

24、lysis the composition of the calibration standard should match the sample as closely as possible, particularly when measuring silicon below 10 mg/kg. If the sample is a light naphtha or gasoline, it may change the characteristics of the plasma, even when diluted. For such samples, prepare the blank

25、by first adding 1.0 g of hexane, and then adding 9.0 g of kerosene. Calculate the concentration of silicon (Si) in the first and second dilutions using Equations 3 and 4: Concentration of silicon, Silicon Calibration Standard, first dilution, mg/kg =HGGF+(3) where: F = concentration of Si in Stock S

26、ilicon Standard B (or purchased 1000-g/g Si standard), mg/kg G = weight of the Stock Silicon Standard B in vial, g H = weight of kerosene in vial, g 4 of 10 796-09 Concentration of silicon, Silicon Calibration Standard, second dilution, mg/kg =LKKJ+(4) where: J = concentration of Si in the Silicon C

27、alibration Standard, first dilution, from Equation 3, mg/kg K = weight of Silicon Calibration Standard, first dilution, in vial, g L = weight of kerosene (or kerosene plus hexane) in vial, g Relabel the vials with the calculated concentration (to three significant figures) of silicon (Si) in each. F

28、or the low concentration silicon samples typically analyzed, the nominally 10-mg/kg Silicon Calibration Standard is used. Higher concentration samples may either be analyzed using the 100-mg/kg standard, or the sample may be diluted to a concentration to fit the 10-mg/kg standard. Preparation of Sca

29、ndium Internal Standard Solutions A known concentration of scandium is added to sample solutions prior to ICP analyses, which is used as an internal standard for the calculation of silicon concentration. Prepare the nominally 100- and 10-mg/kg Internal Standard Solutions as follows: 1. Tare a vial t

30、o the nearest 0.01 g. Weigh in 1.0 0.05 g of the 1,000 g/g scandium standard and record the weight to the nearest 0.01 g. 2. Add 9.00.05 g kerosene and record the weight to the nearest 0.01 g. 3. Label the vial as Internal Standard Solution, first dilution. 4. Tare another vial and add 1.0 0.05 g of

31、 the Internal Standard Solution, first dilution, and record the weight to the nearest 0.01 g. 5. Add 9.00.05 g kerosene and record the weight to the nearest 0.01 g. 6. Label the vial as Internal Standard Solution, second dilution. Calculate the concentration of scandium in the Internal Standard Solu

32、tion, first and second dilutions using Equations 5 and 6: Concentration of scandium, Internal Standard Solution, first dilution, mg/kg =NMM1000+(5) where: M = weight of the 1,000-g/g scandium standard in the Internal Standard Solution, first dilution vial, g N = weight of kerosene in the Internal St

33、andard Solution, first dilution vial, g 1000 = concentration of scandium in the 1,000 g/g standard Concentration of scandium, Internal Standard Solution, second dilution, mg/kg =RQQP+(6) where: P = concentration of scandium in Internal Standard Solution, first dilution vial, from Equation 5, mg/kg Q

34、 = weight of Internal Standard Solution, first dilution vial, g R = weight of kerosene in Internal Standard Solution, second dilution vial, g Relabel the vials with the calculated concentration (to three significant figures) of scandium in each. 5 of 10 796-09 Preparation of Spectrometer Start up th

35、e ICP-OES, ignite the plasma according to the manufacturers recommendations, and allow a minimum of 30 minutes for the instrument to stabilize before starting the analysis. When recommended by the manufacturer, perform a wavelength calibration prior to the start of the analysis. The recommended wave

36、lengths to use for this analysis are listed in Table 1. Table 1 Recommended Wavelengths Element , nm Sc 424.689 Si 212.412 or 251.611* or 288.158 *Use 251.611 as the primary wavelength for silicon. The other wavelengths listed may be used to verify that there is no background interference at the pri

37、mary wavelength. Sample Preparation Samples must be diluted with kerosene prior to analysis. The minimum dilution is a 9:1 ratio of diluent to sample. If aspirating the 9:1 diluted sample is problematic or the silicon is present at higher concentrations, increase the dilution factor. The lower limit

38、 of detection will be impacted with increased dilution. Liquids For samples that are liquid at room temperature and are miscible with the solvent: 1. Obtain a tare weight, to the nearest 0.01 g, of a vial with cap. 2. Shake the sample bottle and, using a disposable dropping pipet, weigh 1.0 0.05 g o

39、f the sample; record the weight to the nearest 0.01 g. If the 9:1 diluted sample is problematic, increase the dilution factor. For example, weigh only 0.5 g or less of the sample. Make up the weight difference by adding more solvent kerosene. 3. Add 8.0 0.05 g of kerosene. Record the weight to the n

40、earest 0.01 g. 4. Add 1.0 0.05 g of the nominally 10-mg/kg Scandium Internal Standard Solution; record the weight to the nearest 0.01 g. For high volume analyses, it may save time to pipet the Scandium Internal Standard Solution into the standard and samples. An automated pipettor (not listed in App

41、aratus) may be set up to dispense a repeatable volume corresponding to 1.00 g of scandium internal standard solution, which will then not need to be weighed. 5. Cap the vial and shake to mix the contents. 6. If insoluble matter is present, centrifuge the solution prior to analysis, and note the pres

42、ence of insolubles in the report. 7. Prepare a calibration standard in the same manner as Steps 1 through 5 above, substituting the nominally 10-mg/kg Silicon Calibration Standard for the sample. 8. Prepare a Sample Blank in the same manner as Steps 1 through 5 above, except do not add sample in Ste

43、p 2, and add 9.0 0.05 g of solvent blank in Step 3. 9. Analyze the calibration standard, the sample blank, and the samples as described under Sample Analysis. 6 of 10 796-09 Viscous Liquids or Meltable Solids If the sample is a solid or a very viscous liquid at room temperature and cannot be readily

44、 dissolved in the solvent: 1. Loosen the sample bottle cap and heat the sample in an oven at 100C for approximately 30 minutes. Also place a glass dropper pipet in the oven. Heating the sample above 100C is not recommended as it may result in the loss of volatile silicone compounds. 2. Place a vial

45、and cap (removed from vial) on the balance and obtain a tare weight. 3. Using thermal gloves or other protection, remove the pipet and sample bottle from the oven, tighten the cap on the sample bottle and shake to mix. 4. Using the hot pipet, transfer 1.0 0.1 g of the hot sample into the tared sampl

46、e vial. Record the weight to the nearest 0.01 g and continue with Steps 3 through 5 for liquid samples. If the 9:1 diluted sample is problematic or the silicon is present at higher concentrations increase the dilution factor. For example, weigh only 0.5 g or less of the sample. Make up the weight di

47、fference by adding more solvent kerosene. 5. Place the vial in an ultrasonic bath for 10 minutes (or as needed for complete dissolution). 6. Analyze the calibration standard, the sample blank (both prepared as described under Sample Preparation, Liquids, Steps 7 and 8), and the sample as described u

48、nder Sample Analysis. The sample must be analyzed within 5 minutes after sonication. If not analyzed within 5 minutes, phase separation may occur, and the results may be suspect. Non-meltable Solids If the sample does not melt at 100C: 1. Obtain dry ice and break it up so that optimum contact with t

49、he sample bottle is achieved 2. Place the sample bottle in the dry ice to cool for about 30 min. 3. Place a vial and cap (removed from vial) on the balance and obtain a tare weight to the nearest 0.01 g. 4. Using thermal protection, remove the sample bottle from the dry ice and use a spatula to break/homogenize the sample 5. Transfer 1.0 0.1 g of the chilled sample into the tared sample vial. Record the weight to the nearest 0.01 g and continue with Steps 3 through 5 for liquid samples. If the 9:1 diluted sample is problemat