1、AMMONIA IN HYDROCARBONSUOP Method 958-98SCOPEThis method is an extraction procedure that, when used in conjunction with UOP Method 959, allows thedetermination of ammonia in liquid hydrocarbon streams. Other nitrogen species, if present, are notdetected by this method. This procedure yields quantita
2、tive results and has been tested in the range ofapproximately 0.5 to 10 mass-ppm ammonia. Higher concentrations can be determined by dilution of theaqueous extract as noted in UOP Method 959, or by performing the extraction using a larger volume ofwater and/or a smaller sample size (preferred if the
3、 ammonia level can be estimated).OUTLINE OF METHODAmmonia is extracted from the hydrocarbon sample using water (see Note 1). The amount of ammoniumion present in the extract is determined using UOP Method 959, an ion chromatographic method. The resultfrom that determination is used to calculate the
4、ammonia in the original sample. Hydrocarbon solutionscontaining ammonia are unstable and have a tendency to lose ammonia with time (see Note 2). Therefore, itis necessary to perform the hydrocarbon extraction and run the UOP Method 959 analysis within the sameworking day. If the ion chromatographic
5、analysis can not be run immediately, the sample extracts must berefrigerated (see UOP Method 959).APPARATUSReferences to catalog numbers and suppliers are included as a convenience to the method user. Othersuppliers may be used.Funnel, separatory, 125-mL, Fisher Scientific, Cat. No. 10-436APipets, v
6、olumetric transfer, Class A, 20- and 50-mL, Fisher Scientific, Cat. Nos. 13-650-2N and 13-650-2S, respectivelyRefrigerator, laboratory, explosion proof, Fisher Scientific, Cat. No. 97-950-1IT IS THE USERS RESPONSIBILITY TO ESTABLISH APPROPRIATE PRECAUTIONARY PRACTICES AND TODETERMINE THE APPLICABILI
7、TY OF REGULATORY LIMITATIONS PRIOR TO USE. EFFECTIVE HEALTH ANDSAFETY PRACTICES ARE TO BE FOLLOWED WHEN UTILIZING THIS PROCEDURE. FAILURE TO UTILIZE THISPROCEDURE IN THE MANNER PRESCRIBED HEREIN CAN BE HAZARDOUS. MATERIAL SAFETY DATA SHEETS(MSDS) OR EXPERIMENTAL MATERIAL SAFETY DATA SHEETS (EMSDS) F
8、OR ALL OF THE MATERIALS USED INTHIS PROCEDURE SHOULD BE REVIEWED FOR SELECTION OF THE APPROPRIATE PERSONAL PROTECTIONEQUIPMENT (PPE). COPYRIGHT 1998 UOP LLCALL RIGHTS RESERVEDUOP Methods are available through ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken PA 19428-2959,Uni
9、ted States. The Methods may be obtained through the ASTM website, www.astm.org, or by contacting Customer Service atserviceastm.org, 610.832.9555 FAX, or 610.832.9585 PHONE.2 of 4958-98Water purification system, Barnstead NANOpure II, three module, equipped with Pretreatment (D0835),Ultrapure (D0809
10、) and Organic Free (D0820) replacement cartridges, Fisher Scientific, Cat. Nos. 09-050-254, 09-034-104, 09-034-3 and 09-034-175K, respectivelyREAGENTS AND MATERIALSAll reagents shall conform to the specifications established by the Committee on Analytical Reagents ofthe American Chemical Society, wh
11、en such specifications are available, unless otherwise specified.References to water mean deionized and distilled water that is subsequently treated with a BarnsteadNANOpure II water purification system to produce ionically pure, 18 megohm-cm, organic-free, water.Vials and caps, for sample water ext
12、ract, Fisher Scientific, Cat No. 03-339-10H. Rinse the vials and capsfive times with water, allow to air dry and store with the caps on.PROCEDURESample ExtractionIf the ammonia concentration can be estimated, the sample volume can be decreased and/or the extractwater volume increased (from that call
13、ed for below) to minimize dilution of the extract required for the ionchromatographic (UOP Method 959) determination. The volumes used must be recorded for later use inCALCULATIONS.1. Obtain the density of the hydrocarbon sample by ASTM Method D 4052.2. Pipet 50 mL of the hydrocarbon sample into a 1
14、25-mL separatory funnel.3. Pipet 20 mL of water into the separatory funnel. Stopper and shake the separatory funnel for fiveminutes, venting frequently by opening the stopcock with the funnel inverted (into a fume hood).Then allow 10 minutes for the two phases to separate.4. Drain a portion of the a
15、queous extract into a 15-mL sample vial, and cap the vial. Discard thehydrocarbon layer.5. Analyze the aqueous extract by ion chromatography as directed in UOP Method 959 (see Note 2).CALCULATIONSCalculate the ammonia concentration in the aqueous extract using the equation below. Report results toon
16、e significant figure below one mass-ppm, to two significant figures at or above one mass-ppm.BEA 0.944 CD=where:A = concentration of ammonia in the hydrocarbon sample, mass-ppmB = mass of water used to extract the sample, gC = volume of the hydrocarbon sample, mLD = density of the hydrocarbon sample
17、 (from ASTM D 4052), g/mLE = concentration of ammonium in extract (from UOP Method 959), mass-ppm0.944 = factor to convert ammonium to ammonia (molecular weight of ammonia divided by themolecular weight of ammonium, 17/18)3 of 4958-98NOTES1. Experiments have shown 98 to 107% recovery of ammonia from
18、 hydrocarbon samples using water toextract the hydrocarbon, which is considered adequate for the intended use of this method.2. Hydrocarbon samples containing ammonia are unstable and will lose ammonia with time. This isespecially true at ambient and elevated temperatures, but will also happen slowl
19、y under refrigeration.Therefore, samples must be extracted as quickly as possible after they are sampled, and the extractsanalyzed within the same working day. If there is to be some delay (but not longer than a few hours)between sampling and extraction or between extraction and analysis, refrigerat
20、e the samples orextracts. For the same reasons, it is difficult, if not impossible, to maintain a control standard formonitoring this analysis.PRECISIONASTM RepeatabilityA nested design was carried out by two analysts at two different concentration levels on one day. Eachanalyst performed four analy
21、ses at each concentration level for a total of 16 analyses. Using a stepwiseanalysis of variance procedure, the within-day estimated standard deviations (esd) were calculated at themean concentrations shown in the Table. Two analyses performed in one laboratory by the same analyst onthe same day sho
22、uld not differ by more than the ASTM allowable differences shown in the concentrationrange listed in the Table with 95% confidence.UOP RepeatabilityA nested design was carried out by two analysts at two different concentration levels on one day. Eachanalyst performed four analyses at each concentrat
23、ion level for a total of 16 analyses. Using a stepwiseanalysis of variance procedure, the within-lab estimated standard deviations (esd) were calculated at themean concentrations shown in the Table. Two analyses performed in one laboratory by different analysts onthe same day should not differ by mo
24、re than the UOP allowable differences shown in the concentrationrange listed in the Table with 95% confidence. The data were all collected on one day due to sampleinstability problems.TableASTM and UOP Repeatability, mass-ppmASTM Repeatability UOP RepeatabilityComponentConcentrationRangeWithin-Day e
25、sdAllowableDifferenceWithin-Lab esdAllowableDifferenceAmmonia 1 to 2 0.06 0.2 0.08 0.3The data in the Table are short-term estimates of repeatability. When the test is run routinely in the field,a control standard and chart should be used to develop a better estimate of the long-term repeatability (
26、if astable control standard can be obtained).4 of 4958-98ReproducibilityThere is insufficient data to calculate the reproducibility of the test at this time.TIME FOR ANALYSISThe labor required for this procedure, without the UOP Method 959 determination, is 0.33 hours and theelapsed time is 0.5 hour
27、s. Including the UOP Method 959 determination, the total labor and elapsed timesare 1.33 hours and 2.5 hours, respectively.REFERENCESASTM Method D 4052, www.astm.orgUOP Method 959, “Ammonium Determination in Aqueous Solutions by Ion Chromatography”SUGGESTED SUPPLIERFisher Scientific Co., 711 Forbes Ave., Pittsburgh, PA 15219-4785 (412-562-8300)
