UOP 938-2010 Total Mercury and Mercury Species in Liquid Hydrocarbons.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 1995, 2000, 2010 UOP LLC. All rights r

3、eserved. 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 FAX, or

4、610.832.9585 PHONE. Total Mercury and Mercury Species in Liquid Hydrocarbons UOP Method 938-10 Scope This method is for determining total mercury in liquid hydrocarbons using a Nippon Instruments Corporation (NIC) Mercury Analyzer. The lower limit of quantitation is 0.3 ng/mL (m/v-ppb). The results

5、can be converted to mass-ppb. Appendix A contains a procedure, Determination of Mercury Species in Hydrocarbons, which can be used to differentiate between elemental mercury, organic non-ionic mercury and ionic (both inorganic and organic) mercury species. Appendix B contains an alternative procedur

6、e for total mercury in liquid hydrocarbons, using different equipment from the same manufacturer. References ASTM Method D4052, “Density and Relative Density of Liquids by Digital Density Meter,” www.astm.org UOP Method 999, “Precision Statements in UOP Methods,” www.astm.org Outline of Method The N

7、IC Mercury Analyzer/Model SP-3D, consisting of a controller, a mercury atomizer and a mercury detector, is specified for this method. The sample is decomposed by heating in the instrument and the mercury vapor in the gaseous products is collected by the mercury collector as gold amalgam. The tempera

8、ture of the mercury collector is kept at 150C to prevent the adsorption of combustion products on the collector. After collection, the amalgam is heated and the mercury is re-amalgamated on a second collector. Upon completion of the two-step gold amalgamation process, the mercury is liberated by hea

9、ting the collector to 700C. The vaporized mercury is carried to an absorption cell with a pure carrier gas and detected by the cold vapor atomic absorption technique. After introducing the sample, all operations from the sample decomposition process to the mercury detection and calculation are carri

10、ed out automatically by the instrument. Apparatus References to catalog numbers and suppliers are included as a convenience to the method user. Other suppliers may be used, unless stated otherwise. 2 of 26 938-10 Balance, readability 0.01-g, 1000-g capacity Balance, readability 0.1-mg Crucibles, hig

11、h-form, 50-mL, Fisher Scientific, Cat. No. 07-965G, several required Cylinder, graduated, 500-ml, Class B, VWR, Cat. No. 89000-258 Flasks, volumetric, glass, Class A, 100- (several required), 500- and 1000-mL, Fisher Scientific, Cat. Nos. 10-210-8C, F and G, respectively Furnace, muffle, 120 V, 50/6

12、0 Hz, 1200C maximum, Fisher Scientific, Cat. No. 10-554-28 Gloves, thermal protection, VWR, Cat. No. 32885-407, optional Mercury analyzer, NIC, Model SP-3D (no substitute), with the following accessories: Air purifier, NIC, Cat. No. 2750-01 Boats, ceramic, NIC, Cat. No. 2744 Collector tube, quartz,

13、NIC, Model M-160, Cat. No. 2704-01 Drawing rod, for boats, NIC, Cat. No. 2725-01 Heat tube, NIC, Cat. No. 2702 Inlet cap for naphtha, NIC, Cat. No. 2710-01N, replaces inlet cover, included with the instrument, when volatile samples are to be analyzed Joints, 6-mm diameter, NIC, Cat. No. 2715-6 Joint

14、s, 8-mm diameter, NIC, Cat. No. 2715-8 Mercury collector, chromosorb coated with gold, NIC, Cat. No. 2751 O-rings, NIC, Cat. No. 2733 Paper, NIC, Cat. No. 2757-02 Printer, NIC, Cat. No. 2606 Sample vessel, for boats and additives, NIC, Model SK-1 Spoon, NIC, Cat. No. 2748-02 Stand, boat, NIC, Cat. N

15、o. 2709 Pipetter, digital, variable volume 20-200 L, Fisher Scientific, Cat. No. 21-377-289 (required for the analysis of heavy hydrocarbon and calibration samples) Pipets, volumetric, Class A, 1-, 2-, 5-, and 10-mL, Fisher Scientific, Cat. Nos. 13-660A, B, E, and F, respectively Pipet filler, Fishe

16、r Scientific, Cat. No. 13-681-51 Recorder, 1-V full scale, 1-sec or less full-scale response, optional Refrigerator, explosion proof or flammable storage Sample containers, glass or Teflon bottles, acid cleaned, see Procedure Syringes, 100- and 250-L capacity, Supelco, Cat. Nos. 20737 and 20738, res

17、pectively (required for the analysis of light hydrocarbon) 3 of 26 938-10 Tongs, crucible, VWR, Cat. No. 82027-372, for muffle furnace use Tweezers, flat, round point, Baxter Scientific, Cat. No. E1200-9 Wash bottle, Nalgene, LDPE, 500-mL, Fisher Scientific, Cat. No. 03-409-17F (used for nitric acid

18、 washing of all glassware) Wash bottle, Nalgene, Right to Know Safety, 1000-mL, for acetone, Fisher Scientific, Cat. No. 03-409-11F Wash bottle, Nalgene, Right to Know Safety, 1000-mL, for water, Fisher Scientific, Cat. No. 03-409-11K Reagents and Materials References to catalog numbers and supplier

19、s are included as a convenience to the method user. Other suppliers may be used, unless stated otherwise. References to water mean deionized or distilled water. Acetone, Fisher Scientific, Cat. No. A18-4 Additive B, NIC, Cat. No. 2754-02 Additive M, prepare by mixing 350 g of calcium hydroxide and 5

20、00 g of sodium carbonate. This can be purchased from NIC premixed, Cat. No. 2754-01 Calcium hydroxide, 99.5% purity, Sigma-Aldrich, Cat. No. C7887 L-Cysteine, 99% purity, Pfaltz and Bauer, Cat. No. C33800 Mercuric chloride, mercury (II) chloride, 99.999% purity, Sigma-Aldrich, Cat. No. 20-377-7 Nitr

21、ic acid, concentrated, Trace Metal Grade, Fisher Scientific, Cat. No. A509-212 Nitric Acid, 1:1. Combine 250 mL of concentrated nitric acid with 250 mL of water in a plastic wash bottle, swirl to mix, and use freshly prepared while still warm. Nitrogen, or oil-free clean air, for blow drying glasswa

22、re Phosphate buffer, pH 7.2, Fisher Scientific, Cat. No. 5800-32. Some phosphate buffers contain mercury compounds as a preservative. The buffer must be mercury free. Pipet tips, disposable, Fisher Scientific, Cat. No. 21-377-45 Sodium carbonate, 99.99% purity, Sigma-Aldrich, Cat. No. 22,442-0 Water

23、, deionized or distilled Weighing paper, Fisher Scientific, Cat. No. 09-898-12A Procedure The analyst is expected to be familiar with general laboratory practices and the equipment being used. Portions of these procedures are specific to the specified apparatus. All glassware including containers fo

24、r samples (glass or Teflon) must be thoroughly cleaned by washing with 1:1 nitric acid, rinsing with water, rinsing with acetone, followed by blow-drying with nitrogen or oil-free clean air. Sampling Samples should be collected in a manner that assures representative sampling. Elemental mercury and

25、4 of 26 938-10 organic-mercury species are unstable and will react with the walls of the sample containers. Do not collect samples in metal containers. Any mercury present will adsorb on the metal. Samples must be collected in previously acid cleaned glass containers and then analyzed as soon as pos

26、sible. Samples should be kept refrigerated if stored. Instrument Set Up 1. Set up the instrument according to the manufacturers instructions. 2. Turn on the power to the instrument in the order shown below. Step-down transformer (if needed) AC stabilizer Controller MA-1 Detector MD-1 Printer Recorde

27、r (optional) The instrument is normally turned off overnight and when not in use. 3. Establish the conditions required for the analysis as indicated in Table 1. 4. Confirm that the AC stabilizer has power and its output voltage is 100V AC by observing the voltmeter on the AC stabilizer panel. If nec

28、essary, adjust to the correct values. 5. Dilute an equal volume of phosphate buffer and distilled water. Pour the dilute buffer into scrubber bottle 1 located on the left position in the cooler. The level of the liquid must be 10 to 20 mm above the air bubble outlet. The buffer mixture is prepared d

29、aily when the instrument is used, and drained and disposed of in an environmentally safe manner when the instrument is shut down. Table 1 Operating Conditions Temperature of sample heating furnace 950C Temperature of decomposition furnace element 850C Pre-heating temperature of mercury collector 150

30、C Mercury collector temperature 700C Carrier gas Dry purified room air Carrier gas pressure 0.4 kg/cm2 (39 kPa) Combustion system flow rate 0.5 L/min Measuring system flow rate (AAS) 0.5 L/min Recorder chart speed 5 mm/min Recorder full scale 1 V Analysis time (dependent on heating mode and measurin

31、g range) 5 - 15 min 6. Turn the leak check switch of the mercury atomizer (MA) upward. The system is now closed. 7. Verify that the gas pressure, the combustion system flow and the measuring system flow correspond to the settings in Table 1. If necessary, adjust the operating conditions to the corre

32、ct values. 5 of 26 938-10 8. Close each of the exhaust outlets, located in the rear lower center of the mercury atomizer, by placing your finger over each opening, and ensure that there is no leakage by observing the flow rate decrease to zero. Only one exhaust outlet should be closed at a time; do

33、not close both at the same time or excessive pressure will build up in the instrument. If there is a leak, consult the instruction manual for the correct procedure to follow. 9. Turn the leak check switch downward and allow the system to warm up for one hour. The system is now open. Preparation of L

34、-Cysteine Solution and Standards L-Cysteine Solution, Approximately 10-mg/L 1. Weigh approximately 0.010 g of L-cysteine, to the nearest 0.1 mg, onto a weighing paper. 2. Transfer quantitatively with water into a 1000-mL volumetric flask. Pipet 2 mL of concentrated nitric acid and dilute to the mark

35、 with water. Cap and invert several times to mix thoroughly. L-cysteine prevents the deposition of mercury on the walls of the glassware. Mercury Standard, Approximately 100-mg/L Alternatively, the standard solutions may be prepared from commercially available 1000-mg/L solutions provided with a cer

36、tificate of analysis. 1. Weigh approximately 0.067 g of mercuric chloride, to the nearest 0.1 mg, onto a weighing paper. 2. Transfer quantitatively with the 10-mg/L L-cysteine solution into a 500-mL (0.5-L) volumetric flask. 3. Dilute to the mark with the 10-mg/mL L-cysteine solution. Cap and invert

37、 several times to mix thoroughly. 4. Calculate the concentration of mercury (Hg) in the standard to three significant figures using Equation 1: Hg, mg/L = 5.0 M)739.0(103(1) where: M = mass of mercuric chloride, g 0.5 = dilution volume, L 0.739 = molecular mass of mercury (200.6) divided by the mole

38、cular mass of mercuric chloride (271.5) 103 = factor to convert g to mg Mercury Standard, Approximately 10-mg/L 1. Pipet 10 mL of the 100-mg/L mercuric chloride standard into a 100-mL volumetric flask. 2. Dilute to volume with the 10-mg/L L-cysteine solution. Cap and invert several times to mix thor

39、oughly. The actual concentration of this standard will be one-tenth of the standard being diluted. 6 of 26 938-10 Mercury Standard, Approximately 5-mg/L 1. Pipet 5 mL of the 100-mg/L mercury standard into a 100-mL volumetric flask. 2. Dilute to volume with the 10-mg/L L-cysteine solution. Cap and in

40、vert several times to mix thoroughly. The actual concentration of this standard will be one-twentieth of the standard being diluted. Mercury Standard, Approximately 1-mg/L 1. Pipet 1 mL of the 100-mg/L mercury standard into a 100-mL volumetric flask. 2. Dilute to volume with the 10-mg/mL L-cysteine

41、solution. Cap and invert several times to mix thoroughly. The actual concentration of this standard will be one-hundredth of the standard being diluted. Mercury Standard, Approximately 0.1-mg/L 1. Pipet 10 mL of the 1-mg/L mercury standard into a 100-mL volumetric flask. 2. Dilute to volume with the

42、 10-mg/L L-cysteine solution. Cap and invert several times to mix thoroughly. The actual concentration of this standard will be one-tenth of the standard being diluted. Mercury Standard, Approximately 0.01-mg/L 1. Pipet 10 mL of the 0.1-mg/L mercury standard into a 100-mL volumetric flask. 2. Dilute

43、 to volume with the 10-mg/L L-cysteine solution. Cap and invert several times to mix thoroughly. The actual concentration of this standard will be one-tenth of the standard being diluted. The mercury standard solutions should be stored in a cool dark place. The maximum shelf life of the solutions is

44、 as follows: 10-mg/L L-cysteine solution - 6 months Mercury standard solutions with concentrations 0.1 mg/L and greater - 6 months Mercury standard solutions with concentrations less than 0.1 mg/L - 1 month Analysis of Light Hydrocarbons Samples that contain volatile material, e.g., gasoline, are an

45、alyzed using this procedure. Less volatile hydrocarbons, e.g., kerosene, diesel, and heavier, are analyzed using the heavy hydrocarbons procedure. Preparation of Additives and Sample Boats Heat-treated portions of Additive B should be used for each analysis. 1. Set the muffle furnace temperature at

46、700 50C. 2. Place approximately 30 g of Additive B into crucibles and place them in the muffle furnace. If the sample is known to contain sulfur compounds, it may be appropriate to use Additive M in addition to Additive B. Consult the instrument manufacturer for specific information and procedures.

47、3. Place sample boats to be used for the analysis in the muffle furnace. Normally, two boats are used for the analysis. 7 of 26 938-10 4. Heat boats and the additive for at least 2 hours. Preparation and Measurement of the Blank 1. Remove the crucibles containing Additive B and the boats from the fu

48、rnace and place them inside the sample vessel. The boats and additives are kept in the sample vessel to prevent contamination by mercury in the air. 2. Set the MA-1 controller to Mode 2 and select a measuring range. Table 2 serves as a guide for selecting a measuring range. The selection of the rang

49、e depends on the expected mercury content of the sample. Table 2 Calibration Ranges and Standards Measuring Range, ng Standard Solution, mg/L Standard Solution Injection Volume, L 2 0.01 50, 100, 150 20 0.1 50, 100, 150 200 1.0 50, 100, 150 1000 5.0 50, 100, 150 3. While the boats and crucibles are cooling in the sample vessel, perform an analysis without inserting a sample boat into the furnace of the analyzer by pressing “START”. This is to expel any mercury gas remaining in the analyzer. The buzzer will soun