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SECTION 1PRELIMINARY OPERATIONSOF ANALYSIS1.11.1 SAMPLING 1.21.1.1 Handling the Sample in the Laboratory 1.21.1.2 Sampling Methodology 1.31.2 MIXING AND REDUCTION OF SAMPLE VOLUME 1.61.2.1 Introduction 1.61.2.2 Coning and Quartering 1.6Figure 1.1 Coning Samples 1.7Figure 1.2 Quartering Samples 1.71.2.3 Riffles 1.71.3 CRUSHING AND GRINDING 1.81.3.1 Introduction 1.81.3.2 Pulverizing and Blending 1.8Table 1.1 Sample Reduction Equipment 1.9Table 1.2 Properties of Grinding Surfaces 1.101.3.3 Precautions in Grinding Operations 1.111.4 SCREENING AND BLENDING 1.11Table 1.3 U.S. Standard Sieve Series 1.121.5 MOISTURE AND DRYING 1.121.5.1 Forms of Water in Solids 1.131.5.2 Drying Samples 1.14Table 1.4 Drying Agents 1.14Table 1.5 Solutions for Maintaining Constant Humidity 1.151.5.3 Drying Collected Crystals 1.15Table 1.6 Concentrations of Solutions of H2SO4, NaOH, and CaCl2 GivingSpecified Vapor Pressures and Percent Humidities at 25C 1.161.5.4 Drying Organic Solvents 1.16Table 1.7 Relative Humidity from Wet- and Dry-Bulb Thermometer Readings 1.17Table 1.8 Relative Humidity from Dew-Point Readings 1.181.5.5 Freeze-Drying 1.191.5.6 Hygroscopic lon-Exchange Membrane 1.191.5.7 Microwave Drying 1.19Table 1.9 Chemical Resistance of a Hygroscopic lon-Exchange Membrane 1.201.5.8 Critical-Point Drying 1.20Table 1.10 Transitional and Intermediate Fluids for Critical-Point Drying 1.211.5.9 Karl Fischer Method for Moisture Measurement 1.211.6 THE ANALYTICAL BALANCE AND WEIGHTS 1.221.6.1 Introduction 1.22Table 1.11 Classification of Balances by Weighing Range 1.231.6.2 General-Purpose Laboratory Balances 1.23Table 1.12 Specifications of Balances 1.231.6.3 Mechanical Analytical Balances 1.241.6.4 Electronic Balances 1.241.6.5 The Weighing Station 1.261.6.6 Air Buoyancy 1.271.6.7 Analytical Weights 1.27Table 1.13 Tolerances for Analytical Weights 1.27 3. 1.2 SECTION ONE1.1 SAMPLING1.1.1 Handling the Sample in the LaboratoryEach sample should be completely identified, tagged, or labeled so that no question as to its originor source can arise. Some of the information that may be on the sample is as follows:1. The number of the sample.2. The notebook experiment-identification number.3. The date and time of day the sample was received.1.7 METHODS FOR DISSOLVING THE SAMPLE 1.281.7.1 Introduction 1.281.7.2 Decomposition of Inorganic Samples 1.29Table 1.14 Acid Digestion Bomb-Loading Limits 1.31Table 1.15 The Common Fluxes 1.33Table 1.16 Fusion Decompositions with Borates in Pt or Graphite Crucibles 1.341.7.3 Decomposition of Organic Compounds 1.34Table 1.17 Maximum Amounts of Combustible Material Recommendedfor Various Bombs 1.36Table 1.18 Combustion Aids for Accelerators 1.361.7.4 Microwave Technology 1.38Table 1.19 Typical Operating Parameters for Microwave Ovens 1.391.7.5 Other Dissolution Methods 1.41Table 1.20 Dissolution with Complexing Agents 1.41Table 1.21 Dissolution with Cation Exchangers (H Form) 1.42Table 1.22 Solvents for Polymers 1.421.8 FILTRATION 1.421.8.1 Introduction 1.421.8.2 Filter Media 1.43Table 1.23 General Properties of Filter Papers and Glass Microfibers 1.44Table 1.24 Membrane Filters 1.47Table 1.25 Membrane Selection Guide 1.47Table 1.26 Hollow-Fiber Ultrafiltration Cartridge Selection Guide 1.48Table 1.27 Porosities of Fritted Glassware 1.49Table 1.28 Cleaning Solutions for Fritted Glassware 1.491.8.3 Filtering Accessories 1.491.8.4 Manipulations Associated with the Filtration Process 1.501.8.5 Vacuum Filtration 1.511.9 SPECIFICATIONS FOR VOLUMETRIC WARE 1.521.9.1 Volumetric Flasks 1.52Table 1.29 Tolerances of Volumetric Flasks 1.521.9.2 Volumetric Pipettes 1.52Table 1.30 Pipette Capacity Tolerances 1.531.9.3 Micropipettes 1.53Table 1.31 Tolerances of Micropipettes (Eppendorf) 1.531.9.4 Burettes 1.54Table 1.32 Burette Accuracy Tolerances 1.54 4. 4. The origin of the sample and cross-reference number.5. The (approximate) weight or volume of the sample.6. The identifying code of the container.7. What is to be done with the sample, what determinations are to be made, or what analysis is desired?A computerized laboratory data management system is the solution for these problems. Informationas to samples expected, tests to be performed, people and instruments to be used, calculations to beperformed, and results required are entered and stored directly in such a system. The raw experimen-tal data from all tests can be collected by the computer automatically or can be entered manually.Status reports as to the tests completed, work in progress, priority work lists, statistical trends, andso on are always available automatically on schedule and on demand.1.1.2 Sampling MethodologyThe sampling of the material that is to be analyzed is almost always a matter of importance, and notinfrequently it is a more important operation than the analysis itself. The object is to get a represen-tative sample for the determination that is to be made. This is not the place to enter into a discussionon the selection of the bulk sample from its original site, be it quarry, rock face, stockpile, productionline, and so on. This problem has been outlined elsewhere.15 In practice, one of the prime factors thattends to govern the bulk sampling method used is that of cost. It cannot be too strongly stressed thata determination is only as good as the sample preparation that precedes it. The gross sample of the lotbeing analyzed is supposed to be a miniature replica in composition and in particle-size distribution.If it does not truly represent the entire lot, all further work to reduce it to a suitable laboratory sizeand all laboratory procedures are a waste of time. The methods of sampling must necessarily varyconsiderably and are of all degrees of complexity.No perfectly general treatment of the theory of sampling is possible. The technique of samplingvaries according to the substance being analyzed and its physical characteristics. The methods ofsampling commercially important materials are generally very well prescribed by various societies inter-ested in the particular material involved, in particular, the factual material in the multivolume publica-tions of the American Society for Testing Materials, now known simply as ASTM, its former acronym.These procedures are the result of extensive experience and exhaustive tests and are generally so defi-nite as to leave little to individual judgment. Lacking a known method, the analyst can do pretty well bykeeping in mind the general principles and the chief sources of trouble, as discussed subsequently.If moisture in the original material is to be determined, a separate sample must usually be taken.1.1.2.1 Basic Sampling Rules. No perfectly general treatment of the theory of sampling is possi-ble. The technique of sampling varies according to the substance being analyzed and its physical char-acteristics. The methods of sampling commercially important materials are generally very wellprescribed by various societies interested in the particular material involved: water and sewage by theAmerican Public Health Association, metallurgical products, petroleum, and materials of constructionby the ASTM, road building materials by the American Association of State Highway Officials, agri-cultural materials by the Association of Official Analytical Chemists (AOAC), and so on.A large sample is usually obtained, which must then be reduced to a laboratory sample. The sizeof the sample must be adequate, depending upon what is being measured, the type of measurementbeing made, and the level of contaminants. Even starting with a well-gathered sample, errors canPRELIMINARY OPERATIONS OF ANALYSIS 1.31 G. M. Brown, in Methods in Geochemistry, A. A. Smales and L. R. Wager, eds., Interscience, New York, 1960, p. 4.2 D. J. Ottley, Min. Miner. Eng. 2:390 (1966).3 C. L. Wilson and D. W. Wilson, Comprehensive Analytical Chemistry, Elsevier, London, 1960; Vol. 1A, p. 36.4 C. A. Bicking, Principles and Methods of Sampling, Chap. 6, in Treatise on Analytical Chemistry, I. M. Kolthoff andP. J. Elving, eds., Part 1, Vol. 1, 2d ed., Wiley-Interscience, New York, 1978; pp. 299359.5 G. M. Brown, in Methods in Geochemistry, A. A. Smales and L. R. Wager, eds., Interscience, New York, 1960, p. 4. 5. occur in two distinct ways. First, errors in splitting the sample can result in bias with concentrationof one or more of the components in either the laboratory sample or the discard material. Second,the process of attrition used in reducing particle sizes will almost certainly create contamination ofthe sample. By disregarding experimental errors, analytical results obtained from a sample of n itemswill be distributed about mwith a standard devitation(1.1)In general, s and mare not known, but s can be used as an estimate of s, and the average of analyti-cal results as an estimate of m. The number of samples is made as small as compatible with thedesired accuracy.If a standard deviation of 0.5% is assigned as a goal for the sampling process, and data obtainedfrom previous manufacturing lots indicate a value for s that is 2.0%, then the latter serves as an esti-mate of s. By substituting in Eq. (1.1),(1.2)and n =16, number of samples that should be selected in a random manner from the total sample sub-mitted.To include the effect of analytical error on the sampling problem requires the use of variances.The variance of the analysis is added to the variance of the sampling step. Assuming that the ana-lytical method has a standard deviation of 1.0%, then(1.3)where the numerator represents the variance of the sampling step plus the variance of the analysis. Thus(1.4)and n = 20, the number of samples required. The above discussion is a rather simple treatment of theproblem of sampling.1.1.2.2 Sampling Gases.6 Instruments today are uniquely qualified or disqualified by theEnvironmental Protection Agency. For a large number of chemical species there are as yet noapproved methods.The size of the gross sample required for gases can be relatively small because any inhomogeneityoccurs at the molecular level. Relatively small samples contain tremendous quantities of molecules.The major problem is that the sample must be representative of the entire lot. This requires the takingof samples with a sample thief at various locations of the lot, and then combining the varioussamples into one gross sample.Gas samples are collected in tubes [250 to 1000 milliliter (mL) capacity] that have stopcocks at bothends. The tubes are either evacuated or filled with water, or a syringe bulb attachment may be used todisplace the air in the bottle by the sample. For sampling by the static method, the sampling bottle isevacuated and then filled with the gas from the source being sampled, perhaps a cylinder. These stepsare repeated a number of times to obtain the desired sampling accuracy. For sampling by the dynamicmethod, the gas is allowed to flow through the sampling container at a slow, steady rate. The containeris flushed out and the gas reaches equilibrium with the walls of the sampling lines and container withrespect to moisture. When equilibrium has been reached, the stopcocks on the sampling container are( . )[( . ) ( . ) ]0 52 0 1 022 2nsns a22 2s s( )0 52 0..=nsns1.4 SECTION ONE6 J. P. Lodge, Jr., ed., Methods of Air Sampling and Analysis, 3d ed., Lewis, Chelsea, Michigan, 1989. Manual of methodsadopted by an intersociety committee. 6. closedthe exit end first followed by the entrance end. The sampling of flowing gases must be madeby a device that will give the correct proportion of the gases in each annular increment.Glass containers are excellent for inert gases such as oxygen, nitrogen, methane, carbon monox-ide, and carbon dioxide. Stainless-steel containers and plastic bags are also suitable for the collec-tion of inert gases. Entry into the bags is by a fitting seated in and connected to the bag to form anintegral part of the bag. Reactive gases, such as hydrogen sulfide, oxides of nitrogen, and sulfur diox-ide, are not recommended for direct collection and storage. However, TedlarTM bags are especiallyresistant to wall losses for many reactive gases.In most cases of atmospheric sampling, large volumes of air are passed through the samplingapparatus. Solids are removed by filters; liquids and gases are either adsorbed or reacted with liquidsor solids in the sampling apparatus. A flowmeter or other device determines the total volume of airthat is represented by the collected sample. A manual pump that delivers a definite volume of air witheach stroke is used in some sampling devices.1.1.2.3 Sampling Liquids. For bottle sampling a suitable glass bottle of about 1-L capacity,with a 1.9-centimeter (cm) opening fitted with a stopper, is suspended by clean cotton twine andweighted with a 560-gram (g) lead or steel weight. The stopper is fitted with another length of twine.At the appropriate level or position, the stopper is removed with a sharp jerk and the bottle permittedto fill completely before raising. A cap is applied to the sample bottle after the sample is withdrawn.In thief sampling a thief of proprietary design is used to obtain samples from within about 1.25 cmof the tank bottom. When a projecting stem strikes the bottom, the thief opens and the sample entersat the bottom of the unit and air is expelled from the top. The valves close automatically as the thiefis withdrawn. A core thief is lowered to the bottom with valves open to allow flushing of the interior.The valves shut as the thief hits the tank bottom.When liquids are pumped through pipes, a number of samples can be collected at various timesand combined to provide the gross sample. Care should be taken that the samples represent a con-stant fraction of the total amount pumped and that all portions of the pumped liquid are sampled.Liquid solutions can be sampled relatively easily provided that the material can be mixed thor-oughly by means of agitators or mixing paddles. Homogeneity should never be assumed. After ade-quate mixing, samples can be taken from the top and bottom and combined into one sample that isthoroughly mixed again; from this the final sample is taken for analysis.For sampling liquids in drums, carboys, or bottles, an open-ended tube of sufficient length toreach within 3 mm of the bottom of the container and of sufficient diameter to contain from 0.5 to1.0 L may be used. For separate samples at selected levels, insert the tube with a thumb over the topend until the desired level is reached. The top hole is covered with a thumb upon withdrawing thetube. Alternatively the sample may be pumped into a sample container.Specially designed sampling syringes are used to sample microquantities of air-sensitive materials.For suspended solids, zone sampling is very important. A proprietary zone sampler is advanta-geous. When liquids are pumped through pipes, a number of samples can be collected at varioustimes and combined to provide the gross sample. Take care that the samples represent a constantfraction of the total amount pumped and that all portions of the pumped liquid are sampled.1.1.2.4 Sampling Compact Solids. In sampling solids particle size introduces a variable. Thesize/weight ratio b can be used as a criterion of sample size. This ratio is expressed as(1.5)A value of 0.2 is suggested for b; however, for economy and accuracy in sampling, the value of bshould be determined by experiment.The task of obtaining a representative sample from nonhomogeneous solids requires that one pro-ceeds as follows. A gross sample is taken. The gross sample must be at least 1000 pounds (lb) if thepieces are greater than 1 inch (in) (2.54 cm), and must be subdivided to 0.75 in (1.90 cm) beforereduction to 500 lb (227 kg), to 0.5 in (1.27 cm) before reduction to 250 lb (113 kg), and so on, downb weight of largest particle 100weight of samplePRELIMINARY OPERATIONS OF ANALYSIS 1.5 7. to the 15-lb (6.8-kg) sample, which is sent to the laboratory. Mechanical sampling machines are usedextensively because they are more accurate and faster than hand-sampling methods described below.One type removes part of a moving steam of material all of the time. A second type diverts all ofstream of material at regular intervals.For natural deposits or semisoft solids in barrels, cases, bags, or cake form, an auger sampler ofpost-hole digger is turned into the material and then pulled straight out. Core drilling is done withspecial equipment; the driving head should be of hardened steel and the barrel should be at least46 cm long. Diamond drilling is the most effective way to take trivial samples of large rock masses.For bales, boxes, and similar containers, a split-tube thief is used. The thief is a tube with a slotrunning the entire length of the tube and sharpened to a cutting edge. The tube is inserted into thecenter of the container with sufficient rotation to cut a core of the material.For sampling from conveyors or chutes, a hand scoop is used to take a cross-sectional sample ofmaterial while in motion. A gravity-flow auger consists of a rotating slotted tube in a flowing mass.The material is carried out of the tube by a worm screw.1.1.2.5 Sampling Metals. Metals can be sampled by drilling the piece to be sampled at regularintervals from all sides, being certain that each drill hole extends beyond the halfway point. Additionalsamples can be obtained by sawing through the metal and collecting the sawdust. Surface chipsalone will not be representative of the entire mass of a metallic material because of differences in themelting points of the constituents. This operation should be carried out dry whenever possible. Iflubrication is necessary, wash the sample carefully with benzene and ether to remove oil and grease.For molten metals the sample is withdrawn into a glass holder by a sample gun. When the sam-ple cools, the glass is broken to obtain the sample. In another design the sampler is constructed oftwo concentric slotted brass tubes that are inserted into a molten or powdered mass. The outer tubeis rotated to secure a representative solid core.1.2 MIXING AND REDUCTION OF SAMPLE VOLUME1.2.1 IntroductionThe sample is first crushed to a reasonable size and a portion is taken by quartering or similar pro-cedures. The selected portion is then crushed to a somewhat smaller size and again divided. Theoperations are repeated until a sample is obtained that is large enough for the analyses to be madebut not so large as to cause needless work in its final preparation. This final portion must be crushedto a size that will minimize errors in sampling at the balance yet is fine enough for the dissolutionmethod that is contemplated.Every individual sample presents different problems in regard to splitting the sample and grind-ing or crushing the sample. If the sample is homogeneous and hard, the splitting procedure will pre-sent no problems but grinding will be difficult. If the sample is heterogeneous and soft, grinding willbe easy but care will be required in splitting. When the sample is heterogeneous both in compositionand hardness, the interactions between the problems of splitting and grinding can be formidable.Splitting is normally performed before grinding in order to minimize the amount of material thathas to be ground to the final size that is suitable for subsequent analysis.1.2.2 Coning and QuarteringA good general method for mixing involves pouring the sample through a splitter repeatedly, com-bining the two halves each time by pouring them into a cone.When sampling very large lots, a representative sample can be obtained by coning (Fig. 1.1) andquartering (Fig. 1.2). The first sample is formed into a cone, and the next sample is poured onto theapex of the cone. The result is then mixed and flattened, and a new cone is formed. As each successive1.6 SECTION ONE 8. sample is added to the re-formed cone, the total is mixed thoroughly and a new cone is formed priorto the addition of another sample.After all the samples have been mixed by coning, the mass is flattened and a circular layer ofmaterial is formed. This circular layer is then quartered and the alternate quarters are discarded. Thisprocess can be repeated as often as desired until a sample size suitable for analysis is obtained.The method is easy to apply when the sample is received as a mixture of small, equal-sizedparticles. Samples with a wide range of particle sizes present more difficulties, especially if thelarge, intermediate, and small particles have appreciably different compositions. It may be nec-essary to crush the whole sample before splitting to ensure accurate splitting. When a coarse-sized material is mixed with a fine powder of greatly different chemical composition, thesituation demands fine grinding of a much greater quantity than is normal, even the whole bulksample in many cases.Errors introduced by poor splitting are statistical in nature and can be very difficult to identifyexcept by using duplicate samples.1.2.3 RifflesRiffles are also used to mix and divide portions of the sample. A riffle is a series of chutes directedalternately to opposite sides. The starting material is divided into two approximately equal portions.One part may be passed repeatedly through until the sample size is obtained.PRELIMINARY OPERATIONS OF ANALYSIS 1.7FIGURE 1.1 Coning samples. (From Shugar and Dean, The Chemists Ready ReferenceHandbook, McGraw-Hill, 1990.)FIGURE 1.2 Quartering samples. The cone is flattened, opposite quarters are selected, andthe other two quarters are discarded. (From Shugar and Dean, 1990.) 9. 1.3 CRUSHING AND GRINDING1.3.1 IntroductionIn dealing with solid samples, a certain amount of crushing or grinding is sometimes required toreduce the particle size. Unfortunately, these operations tend to alter the composition of the sampleand to introduce contaminants. For this reason the particle size should be reduced no more than isrequired for homogeneity and ready attack by reagents.If the sample can be pulverized by impact at room temperature, the choices are the following:1. Shatterbox for grinding 10 to 100 mL of sample2. Mixers or mills for moderate amounts to microsamples3. Wig-L-Bug for quantities of 1 mL or lessFor brittle materials that require shearing as well as impact, use a hammercutter mill for grind-ing wool, paper, dried plants, wood, and soft rocks.For flexible or heat-sensitive samples, such as polymers or tissues, chill in liquid nitrogen andgrind in a freezer mill or use the shatterbox that is placed in a cryogenic container.For hand grinding, use boron carbide mortars.Many helpful hints involving sample preparation and handling are in the SPEX Handbook.71.3.2 Pulverizing and BlendingReducing the raw sample to a fine powder is the first series of steps in sample handling. Samplereduction equipment is shown in Table 1.1, and some items are discussed further in the followingsections along with containment materials, the properties of which are given in Table 1.2.1.3.2.1 Containment Materials. The containers for pulverizing and blending must be harder thanthe material being processed and should not introduce a contaminant into the sample that wouldinterfere with subsequent analyses. The following materials are available.Agate is harder than steel and chemically inert to almost anything except hydrofluoric acid.Although moderately hard, it is rather brittle. Use is not advisable with hard materials, particularlyaluminum-containing samples, or where the silica content is low and critical; otherwise agate mor-tars are best for silicates. Agate mortars are useful when organic and metallic contaminations areequally undesirable. Silicon is the major contaminant, accompanied by traces of aluminum, calcium,iron, magnesium, potassium, and sodium.Alumina ceramic is ideal for extremely hard samples, especially when impurities from steel andtungsten carbide are objectionable. Aluminum is the major contaminant, accompanied by traces ofcalcium, magnesium, and silicon. However, because alumina ceramic is brittle, care must be takennot to feed uncrushable materials such as scrap metal, hardwoods, and so on into crushers or mills.Boron carbide is very low wearing but brittle. It is probably most satisfactory for general use inmortars, although costly. Major contaminants are boron and carbide along with minor amounts ofaluminum, iron, silicon, and possibly calcium. The normal processes of decomposition used in sub-sequent stages of the analysis usually convert the boron carbide contaminant into borate plus carbondioxide, after which it no longer interferes with the analysis.Plastic containers (and grinding balls) are usually methacrylate or polystyrene. Only traces oforganic impurities are added to the sample.Steel (hardened plain-carbon) is used for general-purpose grinding. Iron is the major contami-nant, accompanied by traces of carbon, chromium, manganese, and silicon. Stainless steel is lesssubject to chemical attack, but contributes nickel and possibly sulfur as minor contaminants.1.8 SECTION ONE7 R. H. Obenauf et al., SPEX Handbook of Sample Preparation and Handling, 3d ed., SPEX Industries, Edison, N. J., 1991. 10. 1.9TABLE1.1SampleReductionEquipmentHardness,CuttingJawCrossRotorCentrifugalMortarMixerBallMicroSamplecompositionmohsmillcrusherbeatermillbeatermillgrindermillmillmillsrapidmillBasalt,carbide,carborundum,cementVeryhardclinker,corundum,diabase,glass,andbrittle,granite,ironalloys,ironore,quartz6.58.5Artificialfertilizers,ash,calcite,Hard,4.56.5feldspar,hematite,magnetite,marble,sandstones,slagsBarite,bauxite,calcite,dolomite,Mediumhard,gneiss,kaolin,limestone,2.54.5magnetite,pumice,stonesGraphite,gypsum,hardlignite,Soft,1.52.5mica,salts,talcCardboard,cereals,feeds,fish,food,Fibrousanddriedfruit,leatherscraps,paper,celluloseplantmaterial,textilestypeDuroplasticandthermoplasticElasticmaterials,artificialresins,rubberMaximumsamplesize,cm31MHClO4orHNO3Al,alkalineearths,As,Cr(III),T.Bidleman,Anal.Chim.ActaFe(III),Ga,Ge,Ir,lanthanoids,56:221(1971)Mn,Mo,P,Rh,Ru,Sb(III),Si,Ta,Ti,U,V,W,ZrCHCl30.005Mcupferron,0.1NA,Al,Be,Cd,Co,Cr,Mg,Mn,H.BodeandG.Henrich,Z.Anal.H2SO4orHNO3Ni,U,ZnChem.135:98(1952)Isopentylacetate0.005MKIand3MHClO4orH2SO4plus3%hypophosphiteBoronTetraphenylarsoniumion0.01MTetrafluoroborateionL.DucretandP.Sequin,Anal.Chim.withCHCl3Acta17:213(1957)Methylenebluewith0.01MTetrafluoroborateionL.C.Pasztor,J.D.Bode,andCHCl3or1,2-Q.Fernando,Anal.Chem.32:277dichloroethane(1960)CadmiumDithizoneandCHCl31M2MNaOHpluscitratePb,ZnZ.Marczenko,M.Mojski,andortartrateK.Kasiura,Zh.Anal.Khim.22:1805(1967)DithizoneandCCl4pH8.3,cyanideSeawaterJ.B.MullinandJ.P.Riley,Nature174:42(1954)DiethyldithiocarbamatepH11,cyanide-tartrateZnSeealsoS.BajoandA.Wyttenbach,andCCl4Anal.Chem.49:158(1977)Diethylphosphoro-pH46ZnH.BodeandK.Wulff,Z.Anal.dithioateintoCCl4Chem.219:32(1966)Cerium(IV)Diethylether6M8MHNO3LanthanoidsA.W.Wylie,J.Chem.Soc.1951,1474MIBK8M10MHNO3LanthanoidsL.E.Glendeninetal.,Anal.Chem.27:59(1955)40%v/vtributylphos-8M10MHNO3Silicaterocks;Fe,TiF.CulkinandJ.P.Riley,phateinisooctaneAnal.Chim.Acta32:197(1965)2.43(Continued)Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)Copyright 2004 The McGraw-Hill Companies. All rights reserved.Any use is subject to the Terms of Use as given at the website.PRELIMINARY SEPARATION METHODS 99. TABLE2.21ExtractionProceduresfortheElements(Continued)ElementOrganicphaseAqueousphaseSeparatedfromReferenceCerium(IV)Thenoyltrifluoroacetone0.5MH2SO4Lanthanoids,Th,UG.W.SmithandF.L.Moore,Anal.andxyleneChem.29:448(1957)Chromium(VI)MIBK1M2MHCl,5C,30sV;FeifFpresentH.A.BryanandJ.A.Dean,Anal.shakingChem.29:1289(1957);J.A.DeanandM.L.Beverly,ibid.30:977(1958);P.D.Blundy,Analyst83:555(1958);E.S.PilkingtonandP.R.Smith,Anal.Chim.Acta39:321(1967)MIBK0.02MH2O2;pH1.74,0CHg,Mo(VI),V(V)R.K.BrookshierandH.Freund,Anal.Chem.23:1110(1951);N.Ichinoseetal.,Anal.Chim.Acta96:391(1978)ChromiumTribenzylamineinCHCl31MHClAlkalineearths,As(V),Cd,G.B.Fasolo,R.Malvano,andA.Ce(IV),Co,Cr(III),Cu,Massaglia,Anal.Chim.ActaFe(III),Ga,lanthanoids,29:569(1963);E.M.Donaldson,Mn,Mo,Ni,Sc,U(VI),Talanta27:779(1980)V(V),ZnChromium(III)Aliquat336inCCl4ThiocyanateCo,NiG.J.deJongandU.A.T.Brinkman,J.Radioanal.Chem.35:223(1977)Cobalt1%2-Nitroso-1-naphtholpH4.58.0Fe(III)andNiwhenbackE.Boyland,Analyst71:230(1946);inCHCl3,orCCl4,extractedwithstrongHClO.K.Borggaardetal.,ibid.ortoluene107:1479(1982)0.05%dithizoneinCCl40.02McitrateandpH8Cr,Fe(III),Ti,V;seawater,H.R.MarstonandD.W.Dewey,biomaterials,rock,andAustr.J.Exptl.Biol.Med.Sci.soils18:343(1940);V.D.Anand,G.S.Deshmukh,andC.M.Pandey,Anal.Chem.33:1933(1961)MIBK5MNaSCNNiR.A.SharpandG.Wilkinson,J.Am.Chem.Soc.77:6519(1955)DiethyldithiocarbamatepH6.5Fe,Ca,PG.H.EllisandJ.F.Thompson,Ind.andCCl4Eng.Chem.Anal.Ed.17:254(1945)Copper0.05%dithizone0.1M0.2MHClAs,Cd,Ga,Ge,Fe,Mg,K.J.Hahn,D.J.Tuma,andJ.L.Mn,Mo,Ni,P,Pb,Sb,Sullivan,Anal.Chem.40:974Se,V,W,Zn;steeland(1968)biomaterials5%triphenylphosphitein0.1M1MHCl+ascorbicHighlyselective;Hg,platinumT.H.HandleyandJ.A.Dean,Anal.CCl4acidmetals,ZnChem.33:1087(1961)2.44Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)Copyright 2004 The McGraw-Hill Companies. All rights reserved.Any use is subject to the Terms of Use as given at the website.PRELIMINARY SEPARATION METHODS 100. 2.45NeocuproineManymetalionsP.J.JonesandE.J.Newman,Analyst87:637(1962);C.L.Luke,Anal.Chim.Acta32:286(1965);P.Battistonietal.,Talanta27:623(1980)0.04%diethylammonium10MHClT.V.Ramakrishnaetal.,Talantaacetate,tributyl16:847(1969);A.K.Deandphosphate,trioctylph-A.K.Sen,ibid.13:853(1966);osphineincyclohexaneK.IlsemannandR.Bock,Z.Anal.Chem.274:185(1975)OsmiumCHCl3orCCl41MNaClO4EverythingbutRuunlessR.D.SauerbrunnandE.B.Sandell,Fe(II)isaddedJ.Am.Chem.Soc.75:4170(1953);Anal.Chim.Acta9:86(1953);G.Goldstein,D.L.Manning,O.Menis,andJ.A.Dean,Talanta7:296(1961)CHCl3AsOsCl6withtetraphe-RuW.GeilmannandR.Neeb,Z.Anal.nylarsoniumchlorideChem.156:420(1957)PalladiumDimethylglyoxime0.2M0.3MHClor0.5MAg;CuandCoiforganicR.S.Young,Analyst76:49(1951);inCHCl3H2SO4phaseiswashedwithdiluteseeF.E.Beamish,Talanta14:991aqueousammonia(1967);S.J.Al-BaziandA.Chow,ibid.31:815(1984)Dimethylglyoximein1MHNO3Ag,Au,Ir,Rh,Ru,PtF.I.Danilovaetal.,Zh.Anal.Khim.CHCl329:2150(1974)MIBKAs[PdI4]2Nb,ZrE.M.DonaldsonandM.Wang,Talanta33:35(1986)MesityloxideSalicylicacidatpH4.55.0Au,Ir,Os,Pt,Rh,RuA.D.LangadeandV.M.Shinde,Analyst107:708(1982)Phosphorus20%1-butanolinCHCl3Asmolybdophosphoricacid;Arsenate,germanate,andC.WadelinandM.G.Mellon,Anal.1MHClsilicateionsChem.38:1668(1953)2.48Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)Copyright 2004 The McGraw-Hill Companies. All rights reserved.Any use is subject to the Terms of Use as given at the website.PRELIMINARY SEPARATION METHODS 104. Platinum4-Ocytlanilineindiiso-3MHClCo,Cu,Fe,Ni,andAuA.A.Vasilyevaetal.,Talantabutylketone(ifback-extractedwith7M22:745(1975);C.Pohlandt,ibid.HClO4)26:199(1979);seeS.J.Al-BaziandA.Chow,ibid.31:815(1984);F.E.Beamish,ibid.14:991(1967)PotassiumBenzenewithcrown105 105 7250 15* Precipitate forms.References: F. W. E. Strelow, Anal. Chem. 32:1185 (1960); see also J. Korkisch and S. S. Ahluwalia, Talanta 14:155(1967).Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)Copyright 2004 The McGraw-Hill Companies. All rights reserved.Any use is subject to the Terms of Use as given at the website.PRELIMINARY SEPARATION METHODS 128. in sulfuric acid. Cations such as Zr, Th(IV), U(VI), Ti(IV), Sc, and to a lesser extent Fe(III), In, andCr(III) show the sulfate complexing effect. Uranium(VI) can be separated from Be, Mg, Co, Cu,Fe(II), Fe(III), Mn(II), Al, rare earths, Th, and other elements, and Ti(IV) can be separated from thesame elements, as well as Nb(V), V(V), and Mo(VI). Scandium can readily be separated from Y, La,and the other rare-earth elements. V(IV) is most easily separated from V(V) or V(IV) from Mo(VI)and Nb(V) with H2SO4 as eluent.PRELIMINARY SEPARATION METHODS 2.73TABLE 2.31 Distribution Coefficients (Dg) of Metal Ions on AG50W-X8 Resin in Perchloric Acid SolutionsMetal ion 0.2M 1.0M 4.0MAg(I) 90 20 5.8Al(III) 5250 106 11Ba 2280 127 19Be 206 14 1.9Bi(III) >104 243 42Ca 636 50 7.7Cd 423 36 6.3Ce(III) >104 459 53Co(II) 378 31 4.8Cr(III) 8410 120 11Cu(II) 378 30 4.5Dy(III) >104 258 39Fe(II) 389 32 5.2Fe(III) 7470 119 12Ga(III) 5870 112 11Hg(I) 4160 147 9Hg(II) 937 85 23In(III) 6620 128 14La >104 475 58Mg 312 24 3Mn(II) 387 32 4.7Mo(VI) 22 5.5 4.5Mo(VI)* 0.7 0.4 1.3Ni(II) 387 32 5Pb(II) 1850 117 17Sn(IV) Precipitate Precipitate 7.5Sr 870 67 10Th(IV) >104 5870 686Ti(IV) 549 19 5.7Tl(I) 131 23 2.7Tl(III) 1550 176 41U(VI) 276 29 18V(IV) 201 18 4.4V(V) 9.8 2.2 0.8V(V)* 9.3 3 1W(VI)* 0.4 0.4 0.4Y >104 246 24Yb(III) >104 205 20Zn 361 30 5Zr >104 >104 333* Hydrogen peroxide present.Reference: F. W. E. Strelow and H. Sondorp, Talanta 19:1113 (1972).Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)Copyright 2004 The McGraw-Hill Companies. All rights reserved.Any use is subject to the Terms of Use as given at the website.PRELIMINARY SEPARATION METHODS 129. 2.74 SECTION TWOTABLE 2.32 Distribution Coefficients (Dg) of Metal Ions on AG 50W-X8 Resin in Nitric AcidSolutionsTotal resin capacity ratio q = 0.4, except for Te(IV) where q = 0.2Metal ion 0.1M 0.2M 0.5M 1.0M 4.0MAg(I) 156 86 36 18 4Al >104 3900 392 79 5As(III) 104 4100 362 74 3Ga >104 4200 445 94 6Gd >104 >104 1000 167 7Hf >104 >104 >104 2400 21Hg(I) >104 7600 640 94 14Hg(II) 4700 1090 121 17 3In(III) >104 >104 680 118 6K 99 59 26 11 3La >104 >104 1870 267 9Li 33 19 8 4 1Mg 794 295 71 23 4Mn(II) 1240 389 89 28 3Mo(VI) ppt 5 3 2 1Na 54 29 13 6 1Nb(V) 12 6 1 0.2 0.1Ni(II) 1140 384 91 28 7Pb(II) >104 1420 183 36 4Pd(II) 97 62 23 9 2Rb 118 68 29 13 3Rh(III) 78 45 19 8 1Sc >104 3300 500 116 8Se(IV) 104 1180 25Ti(IV) 1410 461 71 15 3Tl(I) 173 91 41 22 3U(VI) 659 262 69 24 7V(IV) 495 157 36 14 2V(V) 20 11 5 2 1Y >104 >104 1020 174 10Yb >104 >104 1150 193 9Zn 1020 352 83 25 4Zr >104 >104 104 6500 31References: F. W. E. Strelow, R. Rethemeyer, and C. J. C. Bothma, Anal. Chem. 37:106 (1965); J. Korkisch,F. Feik, and S. S. Ahluwalia, Talanta 14:1069 (1967).Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)Copyright 2004 The McGraw-Hill Companies. All rights reserved.Any use is subject to the Terms of Use as given at the website.PRELIMINARY SEPARATION METHODS 130. PRELIMINARY SEPARATION METHODS 2.75TABLE 2.33 Distribution Coefficients (Dg) of Metal Ions on AG 50W-X8 Resin in H2SO4 SolutionsTotal resin capacity q = 0.4, except q = 0.06 for Bi(III)Metal ion 0.1N 0.2N 0.5N 1.0N 4.0NAl >104 8300 540 126 5As(III) 104 >104 1300 242 8Fe(II) 1600 560 139 46 7Fe(III) >104 2050 255 58 2Ga >104 3500 618 137 5Gd >104 >104 1390 246 9Hf 2690 1240 160 12 1Hg(II) 7900 1790 321 103 12In >104 3190 376 87 12K 138 86 41 19 3La >104 >104 1860 329 12Li 48 28 12 6 1Mg 1300 484 124 42 3Mn(II) 1590 610 165 59 5Mo(VI) ppt 5 3 1 0.2Na 81 48 20 9 2Nb(V) 14 7 4 2 0.3Ni(II) 1390 590 140 46 3Pd(II) 109 71 33 14 3Rb 148 91 44 21 3Rh(III) 80 49 29 16 1Sc 5600 1050 141 35 3Se(IV) 104 >104 1380 253 9Yb >104 >104 >104 1330 9Zn 1570 550 135 43 4Zr 546 474 98 5 1* ppt denotes precipitate.Reference: F. W. E. Strelow, R. Rethemeyer, and C. J. C. Bothma, Anal. Chem. 37:106 (1965).Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)Copyright 2004 The McGraw-Hill Companies. All rights reserved.Any use is subject to the Terms of Use as given at the website.PRELIMINARY SEPARATION METHODS 131. 2.76 SECTION TWOTABLE 2.34 Distribution Coefficients (Dg) of Metal Ions on AG 50W-X8 Resin in 0.2N Acid SolutionsMetal ion HCl HClO4 HNO3 H2SO4Ag(I) 90 86Al 2 5250 3900 8300As(III) 104Ca 790 636 480Cd 84 423 392 540Ce(III) 105 >104 >104 >104Co(II) 460 378 392 433Cr(III) 262 8410 1620 176Cu(II) 420 378 356 505Dy >104Fe(II) 389Fe(III) 3400 7470 4100 2050Ga 3040 5870 4200 3500Hg(I) 4160 7600Hg(II) 1 937 1090 1790In 6620 >104 3190La 105 >104 >104 >104Mg 530 312 295 484Mn(II) 610 387 389 610Mo(VI) 22 5 5Ni(II) 450 387 384 590Pb(II) 1850 1420Pd(II) 62 71Rh(III) 45 49Sc 3300 1050Sn(IV) 45 precipitateSr 1070 870Th(IV) >105 >104 >104 3900Ti(IV) 297 549 461 225Tl(I) 131 91 236Tl(III) 1550 1490U(VI) 860 276 262 118V(IV) 201V(V) 7 10 11 15W(VI) 0.4Y >104 >104 >104 >104Yb >104Zn 510 361 361 550Zr 105 >104 >104 474ReferencesFor HCl: F. W. E. Strelow, Anal. Chem. 32:1185 (1960); J. Korkisch and S. S. Ahluwalia, Talanta 14:155 (1967).For HClO4: F. W. E. Strelow and H. Sondorp, Talanta 19:1113 (1972).For HNO3: F. W. E. Strelow, R. Rethemeyer, and C. J. C. Bothma, Anal. Chem. 37:106 (1965); J. Korkisch, F. Feik,and S. S. Ahluwalia, Talanta 14:1069 (1967).For H2SO4: F. W. E. Strelow, R. Rethemeyer, and C. J. C. Bothma, Anal. Chem. 37:106 (1965).Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)Copyright 2004 The McGraw-Hill Companies. All rights reserved.Any use is subject to the Terms of Use as given at the website.PRELIMINARY SEPARATION METHODS 132. PRELIMINARY SEPARATION METHODS 2.772.3.4.5 Anion Exchange of Metal Complexes. Many metal ions may be converted to a nega-tively charged complex through suitable masking systems. This fact, coupled with the greater selec-tivity of anion exchangers, makes anion exchange a logical tool for handling certain metals. Thenegatively charged metal complexes are initially adsorbed by the exchanger from a high concentra-tion of complexing agent, the eluted stepwise by lowering the concentration of the complexing agentin the eluent sufficiently to cause dissociation of the least stable of the metal complexes, and so on.If interconversion of the anion complex is fast, control of ligand concentration affords a powerfultool for control of absorbability, since ligand concentration controls the fraction of the metal presentas adsorbable complex. For each metal and complexing ligand, there is a characteristic curve of logDv versus molarity of complexing agent. Examples are given in Tables 2.35 and 2.36 for metals thatform chloride and sulfate complexes. Similar studies are available for fluoride solution22 and nitratesolutions.23It is possible to devise a number of separation schemes in which a group of metals isadsorbed on a resin from a concentration of the complexing agent, and then each metal in turnis eluted by progressively lowering the complexing agent concentration (Table 2.37). Thus acation that forms no, or only a very weak, anionic complex is readily displaced by several col-umn volumes of the complexing agent, while its companions are retained. For separating twoions, it is advisable to choose a concentration of the complexing agent for which the separationfactor is maximal, yet, at the same time, it is important that the volume distribution ratio of theeluting ion not be higher than unity. When Dv = 1, the peak maximum emerges within approxi-mately two column volumes. The separation of nickel, manganese, cobalt, copper, iron(III), andzinc ions is done as follows.24 The mixture of cations in 12M HCl is poured onto the columnbed, which has been previously washed with 12M HCl. Nickel, which forms no chloro complex,elutes within several column volumes of a 12M HCl solution. The receiver is changed and man-ganese(II) is eluted with several column volumes of 6M HCl. This procedure is repeated usingsuccessively 4M HCl to elute cobalt(II), 2.5M HCl for copper(II), 0.5M HCl for iron(III), andlastly, 0.005M HCl for zinc.Table 2.38 contains selected applications of ion exchange for the separation of a particular ele-ment from other metals or anions. A discussion of ion-exchange chromatographic methods for analy-sis is reserved for Sec. 4.5.2.3.4.6 Ligand-Exchange Chromatography.25 In this method a cation-exchange resin, satu-rated with a complex-forming metal, such as Cu(II), Fe(III), Co(II), Ni(II), or Zn(II), acts as asolid adsorbent. Thus, even though they are bound to an exchanger, these metals retain their abil-ity to be the central atom of a coordination compound. Ligands, which may be anions or neutralmolecules such as ammonia, amines, amino acids, or olefins, are removed from the liquid phaseby formation of complexes with the metal attached to the resin and subsequent displacement ofwater or other solvents coordinated to the metal ion. Although the ordinary strongly acidic andweakly acidic cation exchangers undergo very satisfactory ligand-exchange reactions, the chelat-ing resins that have iminodiacetate functional groups attached to a styrene matrix are ideally suitedfor ligand-exchange work. Strong complex formers, such as nickel, copper, or zinc, are tightlybound to the iminodiacetate exchanger. Consequently, leakage of metal ions from chelatingresins by ordinary ion-exchange reactions with cationic materials in eluting solutions is held toa minimum.Ligands with a stronger complexing tendency are more strongly retained. It is an efficient way toseparate ligands from nonligands. Elution development uses a ligand in the eluent that complexeswith the metal less strongly than the ligands of the mixture. Separations by ligand-exchange chro-matography are outlined in Table 2.39.22 J. P. Faris, Anal. Chem. 32:520 (1960).23 J. P. Faris and R. F. Buchman, Anal. Chem. 36:1157 (1964).24 K. A. Kraus and G. E. Moore, J. Am. Chem. Soc. 75:1460 (1953).25 F. Helfferich, Nature 189:1001 (1961).Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)Copyright 2004 The McGraw-Hill Companies. All rights reserved.Any use is subject to the Terms of Use as given at the website.PRELIMINARY SEPARATION METHODS 133. 2.4 DISTILLATION OR VAPORIZATION METHODSVaporization is the process of separating a mixture into its components by utilizing differences in theboiling points or partial pressures of the constituents. It is a useful method for the isolation, purifica-tion, and identification of volatile compounds. For use in analysis, the process may be simple batch2.78 SECTION TWOTABLE 2.35 Distribution Coefficients (Dv) of Metal Ions on AG 1-10X in HCl SolutionsSlight adsorption observed for Cr(III), Sc, Ti(III), Tl(I), and V(IV) in 12M HCl (0.3 Dv 1).No adsorption observed for Al, Ba, Be, Ca, Cs, K, La, Li, Mg, Na, Ni(II), Po, Rb, Th, and Y in0.112M HCl.Metal ions 2M 4M 6M 8MAg 100 10 3 2As(III) 0.3 6 10As(V) 2 2 2Au(III) 6 105 2 105 79000 30000Bi(III) 5000 630 100 50Cd 1300 630 100 50Co(II) 63 (10M)