UOP 549-2009 Sodium in Petroleum Distillates by ICP-OES or AAS.pdf

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 1964, 1970, 1972, 1981, 2009 UOP LLC.

3、All rights 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, 610.832.9

4、555 FAX, or 610.832.9585 PHONE. Sodium in Petroleum Distillates by ICP-OES or AAS UOP Method 549-09 Scope This method is for determining sodium in petroleum distillate fractions, No. 2 fuel oil and lower boiling hydrocarbons, over a concentration range of approximately 0.05 ppm to 1 wt-%. Sodium in

5、samples is present due to entrainment of aqueous droplets from a caustic washing operation or may be present as an oil-soluble salt. Total sodium, which includes suspended alkali plus oil-soluble salts, or oil-soluble sodium salts alone (organic sodium) are determined. The total sodium content of th

6、e heavier distillates, whole crude, or residual oils should be determined by means of a wet-ashing technique, such as described in UOP Method 391, “Trace Metals in Petroleum Products or Organics by AAS.” References UOP Method 391, “Trace Metals in Petroleum Products or Organics by AAS,” www.astm.org

7、 UOP Method 999, “Precision Statements in UOP Methods,” www.astm.org Outline of Method Samples for the determination of total sodium (suspended aqueous alkali plus oil-soluble organosodium salts) are collected in cleaned plastic bottles. The entire sample, including the suspended material, are extra

8、cted with dilute hydrochloric acid. Sodium is determined in the acid extract by Inductively Coupled Plasma - Optical Emission Spectroscopy (ICP-OES, or simply, ICP) or by Atomic Absorption Spectroscopy (AAS). Samples for the determination of oil-soluble organic sodium are filtered at the sampling po

9、int through glass wool which serves to coalesce the suspended aqueous alkali. The oil-soluble sodium in the filtered sample is determined by acid extraction and subsequent analysis of the extract for sodium. Apparatus References to catalog numbers and suppliers are included as a convenience to the m

10、ethod user. Other suppliers may be used. Wherever possible use plasticware in place of glassware as glass may contribute to sodium contamination over time, see Note 1. Balance, capable of weighing to 0.1 mg 2 of 7 549-09 Balance, top loading, 1000-g capacity, capable of weighing to 0.1 g Beakers, di

11、sposable, polypropylene, 30-mL, VWR, Cat. No. 47751-692 Bottle, Teflon FEP, 1000-mL, with screw cap, VWR, Cat. No. 16071-675 Cylinder, graduated, polypropylene, Class B, 50-mL, VWR, Cat. No. 83008-880 Flask, volumetric, polypropylene, Class B, 50-, 100-, 500-, and 1000-mL, VWR, Cat. Nos. 83008-970,

12、-980, 83009-001, and -006, respectively Funnel, polypropylene, 12-cm diameter, 1-cm diameter stem, VWR, Cat. No. 30252-913 Funnels, separatory, Teflon FEP, 1000- and 2000-mL, VWR, Cat. Nos. 30356-551 and -553, respectively Spectrophotometer, ICP or AAS Spectrophometer, ICP, computer controlled, havi

13、ng sufficient resolving power and dispersion to separate the analytical lines in the 160-800 nm region. The computer must be capable of performing background corrections, blank corrections, and weight/volume and dilution corrections. A commercial grating spectrometer with a band pass of 0.018 nm or

14、less in the first order is satisfactory. PerkinElmer Optima 5300 V Spectrophotometer, AAS, computer controlled, with hollow cathode lamp for sodium. The computer must be capable of performing background corrections, blank corrections, and weight/volume and dilution corrections. PerkinElmer Analyst 8

15、00. Oven, laboratory, capable of operation at 105C Pipet, volumetric transfer, Class B, 5-, 10-, 20-, 25-, 50-, and 100-mL, VWR, Cat. Nos. 89003-482, -476, -444, -446, -448, and -462, respectively Pipet filler, VWR, Cat. No. 53497-055 Ring, cork, VWR, Cat. No. 56250-068 Stand, support, VWR, Cat. No.

16、 60100-105, with support ring, VWR, Cat. No. 60120-124, and swivel clamp, VWR, Cat. No. 21573-708 Stirrer, magnetic, with PTFE-coated stir bar, VWR, Cat. No. 11301-010 Timer, VWR, Cat. No. 62344-585 Reagents and Materials References to catalog numbers and suppliers are included as a convenience to t

17、he method user. Other suppliers may be used. References to water mean deionized water. Glass wool, VWR, Cat. No. EM-GX0090-2 Gloves, disposable, nitrile, VWR, Cat. No. 40101-356 Hydrochloric acid, concentrated, Certified ACS Plus, Fisher, Cat. No. A144S-212 Hydrochloric acid, 2-M. Dilute the concent

18、rated acid with 5 volumes of deionized water. Scandium standards, if needed for ICP internal standard use, SPEX. See Note 2. Sodium standards, stock solutions (A) 1000 g Na/mL, SPEX, Cat. No. PLNA1-2X 3 of 7 549-09 (B) 100 g Na/mL. Dilute 50 mL of A with deionized water to 500 mL in a volumetric fla

19、sk. (C) 20 g Na/mL. Dilute 20 mL of A with deionized water to 1000-mL in a volumetric flask. (D) 2 g Na/mL. Dilute 100 mL of C with deionized water to 1000-mL in a volumetric flask. Sodium standards, working standards for the range 0 to 10 g Na/mL. To each of five 100-mL volumetric flasks add with a

20、 graduated cylinder 40 mL of 2-M hydrochloric acid. Pipet the prescribed sodium stock solution (see Table 1) and dilute to the mark with water. See Notes 1 and 2. These are suggested concentrations, and may be adjusted to match the composition of the samples to be analyzed. Water, deionized Table 1

21、Working Standard Solution Stock Solution Used 0.0 g/mL 0 mL (Calibration Blank) 0.1 g/mL 5 mL of D 0.5 g/mL 25 mL of D 2.0 g/mL 10 mL of C 10.0 g/mL 10 mL of B Preparation of Sample Bottles Prepare the 1000-mL Teflon bottles for sampling as follows: 1. Rinse the Teflon bottles with about 40 mL of 2-

22、M hydrochloric acid and then deionized water. 2. Dry the bottles in an oven at 105C. 3. Obtain and record the tare weight of the bottle with closure to the nearest 0.1 g. Sampling Total Sodium Obtain the sample directly from a flowing line into the cleaned and tared 1000-mL Teflon bottle as follows:

23、 1. Thoroughly purge the sample connection and line with 300 to 400 mL of sample. 2. Flush the bottle with sample several times and then fill the bottle to approximately 900 mL. Dispose of the waste according to local practices and in an environmentally safe manner. Organic Sodium Take the sample di

24、rectly from a flowing line into the cleaned and tared 1000-mL Teflon bottle through a filtering funnel fitted with a 2.5-cm plug of glass wool. 1. Thoroughly purge the sample connection and line with 300 to 400 mL of sample. 2. Pass sample through the filtering funnel fitted with a 2.5-cm plug of gl

25、ass wool and fill the bottle to approximately 900 mL. Take care not to touch the glass wool or the filter funnel with bare hands (use gloves) as this could be a source of sodium contamination. The glass wool serves as a coalescing medium for suspended aqueous solutions, e.g., aqueous sodium hydroxid

26、e. 4 of 7 549-09 Samples that contain little or no suspended aqueous solutions will be clear upon passing through the glass wool and the receiving bottle will not contain any separated aqueous solution. Samples containing a considerable amount of suspended water, when coalesced, will have distinct d

27、roplets or a separate phase on the bottom of the bottle. In either case, the glass wool will have coalesced the haze without removing oil-soluble organosodium compounds. Procedure The analyst is expected to be familiar with general laboratory practices, the technique of ICP or AAS, and the equipment

28、 being used. Total Sodium Prepare the sample for instrumental analysis for total sodium as follows: 1. Weigh the bottle, closure and contents to the nearest 0.1 g and obtain the weight of the sample. 2. Transfer the sample to a 2000-mL separatory funnel. 3. Using a graduated cylinder, add 40 mL of 2

29、-M hydrochloric acid to the bottle. 4. Recap the bottle and shake it for 2 minutes. 5. Transfer the contents of the bottle to the separatory funnel. 6. Place a stirring bar in the separatory funnel and set the funnel in an inclined position on the magnetic stirrer (see Figure). If necessary use a cl

30、amp, tape, or a cork ring to hold the separatory funnel in place. 7. Turn on the stirrer, adjust to a rapid stirring rate, and stir for one hour. 8. Remove the separatory funnel, place it on a ring stand and allow the layers to separate. 9. Draw off the lower layer directly into a 100-mL volumetric

31、flask. 10. Using a graduated cylinder, add 40 mL of deionized water to the sample bottle and rinse it by shaking for 2 minutes. 11. Transfer this washing to the separatory funnel. 5 of 7 549-09 12. Stir for 30 minutes as described in Steps 6 and 7. 13. Return the separatory funnel to the ring stand

32、and allow the layers to separate. 14. Draw off the lower (water) layer into the 100-mL volumetric flask. 15. Add deionized water to bring the volume to the mark. This is the solution for subsequent analysis by the ICP or AAS. See Note 2. Organic Sodium Prepare the sample for instrumental analysis fo

33、r organic sodium as follows: 1. Weigh the bottle, closure and contents to the nearest 0.1 g. Sample was taken into the bottle by filtering through glass wool, see Sampling, Organic Sodium. 2. Decant about 450 mL of sample into a 1000-mL separatory funnel. If a separate, coalesced aqueous phase is pr

34、esent, transfer the sample by pipet instead of decanting. Carefully immerse a 100-mL pipet into the clear hydrocarbon phase, fill, and transfer the contents to the extraction funnel. Take care not to include any of the water phase. Repeat 3 or 4 times to obtain a 400- to 500-mL sample. Predetermine

35、the level by adding this measured amount of water to the separatory funnel and mark the funnel accordingly. 3. Reweigh the bottle after decanting or pipeting the sample to obtain the exact weight of sample used. 4. Using a graduated cylinder, add 40 mL of 2-M hydrochloric acid to the separatory funn

36、el. 5. Place a stirring bar in the separatory funnel and set the funnel in an inclined position on the magnetic stirrer (see Figure). If necessary use a clamp, tape, or a cork ring to hold the separatory funnel in place. 6. Turn on the stirrer, adjust to a rapid stirring rate, and stir for one hour.

37、 7. Remove the separatory funnel, place it on a ring stand and allow the layers to separate. 8. Draw off the lower layer directly into a 100-mL volumetric flask. 9. Using a graduated cylinder, add 40 mL of deionized water to the separatory funnel. 10. Stir on the magnetic stirrer for 30 minutes. 11.

38、 Return the separatory funnel to the ring stand and allow the layers to separate. 12. Draw off the lower (water) layer into the 100-mL volumetric flask. 13. Add deionized water to bring the volume to the mark. This is the solution for subsequent analysis by the ICP or AAS. See Note 2. Preparation of

39、 Blanks Preparation of the blank for total sodium is described in Reagents and Materials, Sodium standards Table 1. A second blank solution is prepared when analyzing for organic sodium. Prepare a blank for organic sodium as follows: 1. Pipet 40 mL of 2-M hydrochloric acid through a 2.5-cm plug of g

40、lass wool and collect the filtrate in a 100-mL volumetric flask. 6 of 7 549-09 2. Rinse the plug with several 10-mL portions of water and finally dilute to the mark with water. See Note 2. 3. Label as Blank B for organic sodium. This Blank B (see Calculations) is read with the samples after the stan

41、dards are run. Instrumental Analysis for Sodium Content Set up the ICP or AAS for sodium content using conditions recommended by the manufacturer. Prepare a calibration curve by aspirating the prepared working standard solutions, including the Calibration Blank, and analyze the samples. See Note 2.

42、Samples that read higher than 10 g/mL are diluted so that they fall within the calibration range of the instrument, see Note 3. Dilute with the Calibration Blank (Blank B for organic sodium analysis). An appropriate dilution factor, C, must be applied in calculating results in such cases, see Calcul

43、ations. Water may be aspirated between the analysis of standards and between the analysis of samples to reduce the use of the calibration blank; however, the instrument must be zeroed while aspirating the calibration blank. Calculations Calculate the sodium in the distillate from Equations 1 or 2: T

44、otal sodium, mass-ppm =WAC100(1) Organic sodium, mass-ppm =WC)BA(100 (2) where: A = the sodium concentration in the diluted extract as read from the instrument or appropriate calibration curve, g/mL B = sodium concentration for the Blank B, g/mL C = dilution factor = (final dilution volume) / (aliqu

45、ot volume) If no aliquot is taken C = 1 W = sample weight, g 100 = volume of sample solution, mL Notes 1. Glassware may be used for short-term operations such as pipetting, where equivalent plasticware is not available, but plasticware must be used for all sampling and storage, as sodium can leach o

46、ut of glassware over time. 2. For analysis by ICP, a scandium internal standard is often used. If using the internal standard technique, prepare the internal standard solutions and analyze the samples according to standard ICP practices. 3. As an alternative to dilution of samples that read higher t

47、han 10 g/mL, calibration standards may be prepared at higher levels, up to 100 g/mL or more, to bracket the concentration in the sample. 7 of 7 549-09 4. For greatest accuracy it is best to obtain duplicate samples. Slight contamination at low sodium levels can cause significant differences. Precisi

48、on Precision will vary somewhat, depending upon whether an ICP or an AAS is used, and will also vary with the specific instrumentation and installation. Determine the precision for the specific installation according to the procedures listed in UOP Method 999, “Precision Statements in UOP Methods,”

49、or other valid statistical procedure. If the precision found is significantly worse than that listed in Table 2, check the equipment and procedures used for problems. Repeatability The testing protocols of UOP Method 999, concerning the number of analysts and days were not used. The calculation protocols for UOP Method 999 were used. One sample of kerosene was analyzed by AAS six times. Table 2 Repeatability, mass-ppm Sample Sodium Concentration Within- Day esd Allowable Difference Kerosene 0.16 0.013 0.05 The data in Table 2 are a short-ter