1、Designation: D 3270 00 (Reapproved 2006)Standard Test Methods forAnalysis for Fluoride Content of the Atmosphere and PlantTissues (Semiautomated Method)1This standard is issued under the fixed designation D 3270; the number immediately following the designation indicates the year oforiginal adoption
2、 or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 These test methods describe the semiautomated proce-dure for the analyses o
3、f various types of samples for thepurpose of determining total fluoride. Since the test methodsincorporate microdistillation of the sample, they may beapplied to any fluoride-containing solution where standards ofidentical composition have been carried through the samesample preparation procedures a
4、nd have proven to providequantitative recovery when analyzed by the semiautomatedsystem. Conversely, the methods shall not be applied foranalyses until the applicability has been demonstrated.1.2 In normal use, the procedure can detect 0.1 g/mL of F.The normal range of analysis is from 0.1 to 1.6 g/
5、mL of F.Higher concentrations can be analyzed by careful dilution ofsamples with reagent water. If digested samples routinelyexceed 1.6 g/mL of F, the analytical portion of the pumpmanifold can be modified to reduce sensitivity. However, thebest procedure is to analyze a smaller aliquot of the sampl
6、e.Most accurate results are obtained when the fluoride concen-tration falls in the middle or upper part of the calibration curve.1.3 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.4 This standard does not purport to address
7、all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. See 8.3, 10.2.4, and10.2.5 for additional precautions.2. Ref
8、erenced Documents2.1 ASTM Standards:2D 1193 Specification for Reagent WaterD 1356 Terminology Relating to Sampling and Analysis ofAtmospheresD 3266 Test Method for Automated Separation and Collec-tion of Particulate and Acidic Gaseous Fluoride in theAtmosphere (Double Paper Tape Sampler Method)D 326
9、7 Test Method for Separation and Collection of Par-ticulate and Water-Soluble Gaseous Fluorides in the At-mosphere (Filter and Impinger Method)D 3268 Test Method for Separation and Collection of Par-ticulate and Gaseous Fluorides in theAtmosphere (SodiumBicarbonate-Coated Glass Tube and Particulate
10、FilterMethod)D 3269 Test Methods for Analysis for Fluoride Content ofthe Atmosphere and Plant Tissues (Manual Procedures)D 3614 Guide for Laboratories Engaged in Sampling andAnalysis of Atmospheres and Emissions3. Terminology3.1 DefinitionsFor definitions of terms used in thesemethods, see Terminolo
11、gy D 1356.4. Summary of Test Methods4.1 These semiautomated methods are based on the distil-lation of hydrogen fluoride (HF) from the sample and subse-quent reaction of the distillate with alizarin fluorine blue-lanthanum nitrate reagent, to form a blue complex which ismeasured colorimetrically at 6
12、24 nm (1)3, or the subsequentmeasurement with a specific ion probe.4.2 General, Plant Material:4.2.1 The plant material including leaf samples, washed orunwashed, is dried, and ground, then dissolved with perchloricacid and diluted to 50 mL with water. In the case of leafsamples, an appreciable amou
13、nt of fluoride may be depositedon the external leaf surfaces. This fluoride behaves differentlyphysiologically from fluoride absorbed into the leaf and it isoften desirable to wash it from the surface as a preliminary stepin the analysis. Details of a leaf-washing process are describedin 9.1.1These
14、test methods are under the jurisdiction of ASTM Committee D22 on AirQuality and are the direct responsibility of Subcommittee D22.03 on AmbientAtmospheres and Source Emissions.Current edition approved April 1, 2006. Published May 2006. Originallyapproved in 1991. Last previous edition approved in 20
15、00 as D 3270 - 00.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3The boldface numbers in parentheses refer
16、to the references at the end of thismethod.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4.3 General, Atmospheric Samples:4.3.1 Test Methods D 3269 contains acceptable proceduresand also techniques for the proper preparation of atm
17、osphericsamples. Test Methods D 3266, D 3267, and D 3268 aresampling procedures for ambient air and each method containsspecific instructions for sample preparation prior to analyses bythe semiautomated method.4.4 General, System Operation:4.4.1 The dissolved digest is pumped into the polytetrafluo-
18、roethylene coil of a microdistillation device maintained at170C (2-6). A stream of air carries the acidified samplethrough a coil of TFE-fluorocarbon tubing to a fractionationcolumn. The fluoride and water vapor distilled from the sampleare swept up the fractionation column into a condenser, and the
19、condensate passed into a small collector. Acid and solidmaterial pass through the bottom of the fractionation columnand are collected for disposal. Acid and solid material passthrough the bottom of the fractionation column and arecollected for disposal. In the colorimetric method, the distillateis m
20、ixed continuously with alizarin fluorine blue-lanthanumreagent, the colored stream passes through a 15-mm tubularflow cell of a colorimeter, and the absorbance measured at 624nm. In the potentiometric method, the distillate is mixedcontinually with a buffer, the mixed streams pass through aflow-thro
21、ugh fluoride ion electrode, and the differential milli-voltage is measured with an electrometer. The impulse istransmitted to a recorder.4.4.2 All pieces of apparatus are commercially available, ormay be adapted from commercially available equipment. Thetest method can also be run on most commercial
22、ly availablerobot chemical analyzers. Details of construction of the micro-distillation device are described in 7.10. Earlier versions of thistest method have been published (3,5,6).4.5 Principle of Operation:4.5.1 Colorimetric SystemThe absorbance of an alizarinfluorine blue-lanthanum reagent is ch
23、anged by very smallamounts of inorganic fluoride.4.5.2 Potentiometric SystemSince the sample system isthe same for this procedure as for the colorimetric procedure,the distillation step removes all of the interfering cations. Thevolatile acids that remain can be buffered by mixing with theTotal Ioni
24、c Strength Adjustment Buffer (TISAB).4.5.3 Distillation SystemSince HF has a high vapor pres-sure, it is more efficiently distilled than the other acidspreviously mentioned (4.5). The factors controlling efficiencyof distillation are temperature, concentration of acid in thedistillation coil, and va
25、cuum in the system. Large amounts ofsolid matter, particularly silicates, will also retard distillation.Accordingly, the smallest sample of vegetation consistent withobtaining a suitable amount of fluoride should be analyzed.The aforementioned conditions must be carefully controlled,since accurate r
26、esults depend on obtaining the same degree ofefficiency of distillation from samples as from the standardfluoride solutions used for calibration.4.5.4 Temperature control is maintained within 62C by thethermoregulator and by efficient stirring of the oil bath. Acidconcentration during distillation i
27、s regulated by taking plantsamples in the range from 0.1 to 2.0 g and by using 100 6 10mg of CaO and 3.0 6 0.1 g of NaOH for ashing and fusion ofeach sample. Vacuum in the system is controlled with flow-meters and a vacuum gage. Any marked change in vacuum(greater than 0.7 kPa or 0.2 in. Hg) over a
28、short time periodindicates either a leak or a block in the system. Distillationshould take place at the same vacuum each day unless someother change in the system has been made. It is also essentialto maintain the proper ratio between air flow on the linedrawing liquid and solid wastes from the dist
29、illation coil andon the line drawing HF and water vapor (Fig. 1) from thedistillation unit. Occasional adjustments on the two flow-meters should be made to keep this ratio constant and tomaintain higher vacuum on the line drawing HF vapor so thatlittle or no HF is diverted into the liquid and solid
30、waste line.(See 10.3.4 for description of air flow system.)5. Significance and Use5.1 These test methods may be used for determining thefluoride content of particulate matter and gases collected fromthe atmosphere by passive and active means, including planttissues. The user is warned that the fluor
31、ide content of passivecollectors (including plants) give only qualitative or semiquan-titative measurement of atmospheric fluoride content.6. Interferences6.1 Since the air that is swept through the microdistillationunit is taken from the ambient atmosphere, airborne contami-nants in the laboratory
32、may contaminate samples. If this is aproblem, a small drying bulb filled with calcium carbonategranules can be attached to the air inlet tube of the microdis-tillation unit.6.2 If the polytetrafluoroethylene distillation coil is notcleaned periodically, particulate matter will accumulate andwill red
33、uce sensitivity.6.3 Silicate, chloride, nitrate, and sulfate ions in highconcentration can be distilled with fluoride ion and willinterfere with the analysis by bleaching the alizarin fluorineblue-lanthanum reagent. Phosphate ion is not distilled, andtherefore does not interfere. Metals such as iron
34、 and aluminumare not distilled and will not interfere with the analysis (mostmaterials distilled over do not interfere with the potentiometricmethod). Maximum concentrations of several common anionsa Air Inlet g Waste Bottle with H2SO4b Microdistillation Coil h Gas-Drying Towerc Fractionation Column
35、 i T-Tubed Water-Jacketed Condenser j Vacuum Gaugee Sample Trap k Flowmeterf Waste Bottle l Vacuum PumpFIG. 1 Schematic Drawing of Air Flow System for SemiautomatedAnalysis of FluoridesD 3270 00 (2006)2at which there was no detectable interference are given inTable1. The sulfate concentration shown
36、is the amount toleratedabove the normal amount of sulfuric acid used in microdistil-lation. A number of materials cause changes in absorbance at624 nm. Potential interfering substances commonly found inplant tissues are metal cations such as iron and aluminum,inorganic anions such as phosphate, chlo
37、ride, nitrate, andsulfate, and organic anions such as formate and oxalate.Fortunately, metal cations and inorganic phosphate are notdistilled in this system, and organic substances are destroyedby preliminary ashing. The remaining volatile inorganic anionsmay interfere if present in a sufficiently h
38、igh concentrationbecause they are distilled as acids. Hydrogen ions bleach thereagent which, in addition to being an excellent complexingagent, is also an acid-base indicator. To reduce acidic interfer-ences, a relatively high concentration of acetate buffer is usedin the reagent solution despite so
39、me reduction in sensitivity.7. Apparatus7.1 Multichannel Proportioning Pump, with assorted pumptubes, nipple connectors, glass connectors, and manifold plat-ter.7.2 Pulse Suppressors, for the sample and alizarin fluorineblue-lanthanum reagent streams are each made from 3.05 mlengths of 0.89-mm insid
40、e diameter polytetra fluoroethylenestandard wall tubing. They are both an effective reagent filterand a pulse suppressor. Discard them after one month of use.The outlet ends of the suppressor tubes are forced into shortlengths of (0.081-in.) inside diameter silicone rubber tubing,that is then connec
41、ted to the reagent pump tube, and the otherend then slipped over the h fitting which joins the sample andreagent streams.7.3 Automatic Sampler, with 8.5 mL plastic sample cups.7.4 Voltage Stabilizer.7.5 Colorimeter (for colorimetric method), with 15-mmtubular flow cell and 624-nm interference filter
42、s.7.6 Ion Selective Electrode Detector, (for potentiometricmethod) with flow-through electrodes.7.7 Rotary Vacuum and Pressure Pump, with continuousoiler.7.8 Recorder.7.9 Range Expander.7.10 Microdistillation ApparatusA schematic drawing isshown in Fig. 2. Major components of microdistillation appa-
43、ratus include the following:7.10.1 Reaction Flask, 1000-mL, with a conical flange andcover (Fig. 2 A).7.10.2 Reaction Flask Flange Clamp (Fig. 2B).7.10.3 Variable Speed Magnetic Stirrer (Fig. 2D).7.10.4 Thermometer-Thermoregulator, range 0 to 200C(Fig. 2 C).7.10.5 Electronic Relay Control Box.7.10.6
44、 Immersion Heater,500W(Fig. 2F).7.10.7 Flexible Polytetrafluoroethylene, TFE tubing,4.8-mm outside diameter, 0.8-mm wall. A9.14-m length iscoiled on a rigid support of such a diameter that the completedcoil shall fit into the resin reaction flask (7.10.1). Care must betaken to prevent kinking of the
45、 tubing.7.10.8 Flowmeter, with ranges from 0 to 5 L/min, withneedle valve control.7.10.9 Vacuum Gage, with a range from 0 to 34 kPa (254torr).7.10.10 Microdistillation Column,(Fig. 2G, also see Fig. 3).7.10.11 Distillate Collector (Fig. 2I and Fig. 3).TABLE 1 Maximum Detectable Concentration of Seve
46、ral AnionsPresent in Samples at Which There is No Detectable AnalyticalInterferenceCompound Tested Interfering Anion Molarity ToleratedNa2SO4SO4(-2) 2 E-2Na2SiO3SiO3(-2) 5 E-3NaCl Cl(-1) 1 E-3NaH2PO4PO4(-3) 3.8NaNO3NO3(-1) 5 E-3A Reaction Flask, Flange, Cover I Sample TrapB Flange Clamp J Sample Inl
47、etC Thermometer-Thermoregulator K Acid InletD Variable Speed Magnetic Stirrer L Waste TrapE Flexible TFE Tubing M TubingF Immersion Heater N Air InletG Fractionation Column O Sample Trap TopH Water-Jacketed CondenserFIG. 2 Schematic Drawing of Semiautomated MicrodistillationApparatusFIG. 3 Microdist
48、illation ColumnD 3270 00 (2006)37.10.12 Water-Jacketed Condenser (Fig. 2H).7.10.13 Heat Exchange Fluid, for reaction flask (7.10.1).7.11 Mechanical Convection Oven.7.12 Wiley Cutting Mill.7.13 Crucibles, 40 mL, nickel, platinum or inconel.7.14 Muffle Furnace.7.15 pH Meter.8. Reagents and Materials8.
49、1 Purity of ReagentsAll reagents shall conform to thespecifications of the Committee on Analytical Reagents oftheAmerican Chemical Society, where such specifications areavailable.48.2 Purity of WaterWater shall be Type II reagent waterconforming to Specification D 11938.3 Reagents for Automated Fluoride Determination:8.3.1 Acetate Buffer (pH 4.0)Dissolve 60 g of sodiumacetate trihydrate (8.3.14) in 500 mLof reagent water.Add 100mL of acetic acid (8.3.2) and dilute to approximately 900 mLwith water. Measure the pH and adjust it to pH 4.0 with NaOH(8.3.16.1) or acetic aci
