Tyson. What Do Analytical Chemists Do

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Chapter 1What Do Analytical Chemists Do?

Chemicals are part and parcel of our everyday life. The quality oflife we enjoy in our part of the world in the latter part of thetwentieth century heavily depends on the chemical industry. Thebasic materials for fabrication - metals, cements, glass, andplastics - are all produced by the thousands of tonnes each year.Even wooden objects are glued, nailed, or screwed together by aproduct of a s~ctor of the chemical industry, and are maybefinished off with a thin layer of varnish or paint.Clothes consist, in part at least, of a manufactured fibre and arecoloured by dyes and washed in detergents that have beenformulated and made by chemists. As well as keeping us cleanand warm and dry, chemicals are closely involved in keeping usalive by virtue of what we eat and drink. Agriculture could nothave achieved its present level of output without fertilisers,pesticides, animal feeds, supplements, etc., nor could ill-health becombated soeffectively without the enormous range of medicinesproduced by the pharmaceutical industry.If you make a list of all the things you can see now that aremanufactured chemicals and compare it with the correspondinglist of natural materials, you will perhaps appreciate just howimportant the modern chemical industry is. It is strange that thepublic at large has come to regard the word 'chemical' as meaningsomething nasty and dangerous, whereas the reality of the matteris that we are now almost totally dependent on the skill andingenuity of our chemists.An even more sobering thought is that we are totally dependent on a continuing supply of the starting materials. Skilled


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What DoAnalytical Chemists Do? 3though chemists are, even they are subject to the law of conservation of matter. Ballpoint pens and semi-conductor devices are notmade out of thin air, nor do the starting materials grow on trees.Though who knows: when what we can get out of the groundruns out, cellulose may come into its own as a feedstock materialsince the most efficient way of chemically storing solar energy isatpresent bygreen-plant photosynthesis. At the moment itisoil andmineral deposits that keep the chemical industries going. But notjust the chemical industry, these materials also provide ourenergy. In the not too distant future we will be faced with theproblem of what to do when these resources run out. Although itis difficult to predict accurately when these basic feedstocks willbe depleted, it will be up to chemists to provide solutions to theproblems this will cause.At present there are about 50000 chemists in the U.K.(approximately half of all the U.K. scientists). The major employers of chemists are shown in Figure 1.1, the various majorcategories of jobs that chemists do are shown in Figure 1.2,and afurther, more detailed breakdown of the variety of manufacturing industries, government, and other service industries in whichchemists are employed is shown in Figure 1.3. No doubt, you

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Figure 1.2 The relative numbers ofchemistsin the major types of work that theydo. Note that analytical work is one of the three major categories ofwork for chemists.

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Figure 1.3 A more detailed breakdoum of thefield of emPloyment of chemists inthe U.K.


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5appreciate the role of the chemist in agriculture, cement manufacture, cosmetic formulation, food preparation, pa,ckaging technology, petroleum refining, drug synthesis, etc. But what aboutanalytical chemists - where do they fit into the picture?

THE IMPORTANCE OF CHEMICAL COMPOSITIONTo appreciate the role of the analytical chemist, we need to look abit more closely at the materials produced by the chemicalindustry. All industrial products, whether they are tobe viewed aschemicals or as something more complex, are designed for aparticular purpose or to do a specific job. It may be quite a simplejob such as providing a relatively rigid, insoluble container forhot, aqueous liquids that won't break when dropped on thekitchen floor (a plastic cup), or it may be a more complicatedjobsuch as the combination of the long list of specifications for thecomponents of a video recorder. The fundamental designfeature common to both these examples is that the componentsand the complete article will only be up to specification if theyhave the correct chemical composition. That is to say themechanical, electrical, optical, thermal, and other properti~s of amaterial depend on its chemical nature. In some cases itis not justthe relative proportions of the various atoms or molecules thatare important but also the way in which the atoms are linkedtogether. This is particularly true in the ca,.seof polymers whosemechanical properties (flexibility, rigidity, etc.) are directly related to the extent of crosslin king between polymeric chains. Inother cases the properties may depend on relatively smallproportions of constituent atoms or molecules. In steel the minoralloying elements, carbon, tungsten, nickel, cobalt, etc., governthe mechanical properties and even, in the case of chromium, thechemical properties (e.g. corrosion resistance). A more strikingexample of the role of minor components is provided by theelectrical properties of semi-conductor devices, governed by keyelements such asarsenic or germanium, which are present at verylow concentrations indeed in the silicon.

The material may be a mixture of chemicals that only has theright properties because of the composition of the mixture. Aprocessed food may contain preservatives, colouring, sugar,vitamins, and emulsifiers added to the basic fat, protein, and/orcarbohydrate. Beer only has its intoxicating effect because of the

alcohol content, and its taste is due to the presence of chemicalsextracted from the malt or hops during the brewing process.Manufacturers obviously must not only be able to perform theappropriate chemical reactions to convert the starting materialsinto the desired product but also ensure that the product has theappropriate chemical composition. There may be a range ofcompositions for which the product has the required properties,and it isclearly economic sense to minimise the proportion of theexpensive chemicals. As weshall see later, analytical chemists, too,are subject to financial constraints in what they do.

WHAT DO ANALYTICAL CHEMISTS DO?What analytical chemists do, as you may already have guessed, ischeck the chemical composition of the products. However, this isnot the only thing that analytical chemists do: there are manyother things, apart from the products of various manufacturingprocesses, that need to have their chemical compositions checked.But let's start by ccjnsidering this aspect of the analytical chemist'swork.As a very larg~ number of materials are mixtures of chemicals,

every manufacturing company needs to employ analytical chemists whose job it is to devise ways of measuring the relativeamounts of the various chemical species that go to make up theparticular material. This may be the concentration of elementslike carbon and nickel in the case of a steel sample or theconcentration of certain molecules such as the vitamins in abreakfast cereal or the amount of drug in a pill. Not only doanalytical chemists have to devise ways of carrying out thesemeasurements but they also have to be able to identify chemicals.This is because no manufacturing process runs indefinitelywithout a hitch and when something goes wrong analyticalchemists will be called on to help troubleshoot. This may involveidentifying the impurities or components that have thrown theprocess off beam and trying to track down their source. It may bethat the nature of a starting material has changed, perhapsbecause the company has changed supplier or critical reactionconditions have not been maintained, or a catalyst has reachedthe end of its useful life.If the company is selling the product in a very competitive

market, the analytical chemists willbe given thejob of finding out


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7the nature and composition of the competitor's products. Evenwhen production is running smoothly, there may bf the composition of various intermediates to check and the composition ofthe starting materials will have to be verified. The research labswill be making new materials that will have to be analysed, and thelevels of toxic materials in effluents that a factory discharges intothe atmosphere or into a water course will have to be monitored.The role of the analytical chemist in industry is summarised inFigure 1.4.

Figure 1.4 The analytical chemist in indlL5try: (a) samPling and test ing rawmaterials, (b) testing intermediates, (c) monitoring product quality,and (d) monitoring effluent quality.

What Else Do Analytical Chemists Do?:\part from the role of the analytical chemist in the manufacturing and processing industries, there are many other aspects ofour complex life-style in which analytical chemists (and otherchemists, of course) are involved. For example, did you know thatanalytical chemists are '"Helping to Save Lives. The laboratories of nearly all hospitalscontain a considerable number of analytical personnel (calledclinical chemists) who carry out a wide range of jobs. Theseinvolve the analysis of samples of patients'blood, urine, etc. for avariety of components to help doctors with their diagnoses (seeFigure 1.5). The progress of a patient with a particular disease

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Figure 1.5 The analytical chemist in hosPital.may be followed by monitoring the concentrations of certain keycomponents of the blood or urine. The effectiveness of a courseof drugs may be assessed by analysing for the particular activeingredient or its metabolites (compounds into which the bodyconverts the drug in order to try to remove it). Often a drug maynot be effective at very low levels but is harmful at highconcentrations and so the patient must be checked regularly tosee that the level of drug circulating in the body is correct. If youthink of the number of people who have a 'sample' taken by theirdoctor or health clinic staff and of the number of people inhospital or being treated with drugs at anyone time, you begin toget an idea of the problems that clinical chemists face. Dealing


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What DoAnalytical Chemists Do? 9with a very large number of samples and producing quickanswers (to the questions the doctors are asking in !his case) is aproblem that will be discussed later. In cases of poisoning, aspecialist analytical chemist called a toxicologist will be involvedwho may have to identify the toxic material responsible but mayhave litt le evidence to work with if the victim is unconscious.Helping to Protect the Consumer and the Environment. The qualityof some of the materials that we make use of in our everyday lives(e.g. those we eat and drink) is controlled by acts of parliament.Among other jobs, the public analyst checks all these productsregularly to see if they conform to the appropriate legal requirement (see Figure 1.6). The work of the public analysts and their

Figure 1.6 The analytical chemist checks (a) food and drink and (b) theenvironment.staff is obviously very important and the highest standards arerequired, to the extent that public analysts must have a specialqualification in analytical chemistry (called the Mastership ofChemical Analysis). Central and local government have largenumbers of scientists working for them, including a goodproportion of analytical chemists. The best-known establishmentis probably the Laboratory of the Government Chemist (LGC) inLondon. The scientific civil servants who work there not onlyanalyse food, drink, medicines, pesticides, etc. but also provide aservice to Customs and Excise by examining beers, wines, spirits,oils, petrol, tobacco products, and a variety of contrabandincluding drugs.

Along with the Health and Safety Executive laboratories, theLGC also monitors the level of toxic and hazardous substances inthe work-place environment, such as the level of asbestos fibres,mercury vapour, or lead dust. Like the clinical chemist, thescientific civil servant in this situation may be faced with theproblem of measuring very small amounts of the potentiallyhazardous chemical as well as dealing with a work-load of anextremely large number of analyses.The provision of drinking water is a process which must becarefully and constantly monitored. The Water Authorities makegreat use of analytical chemists' skills in keeping a check on thequality of the water, not only in terms of the materials that mustbe removed before the water is considered drinkable but also interms of the chemicals that are added, such as fluoride to helpkeep our teeth in good shape and chlorine to kill bacteria. Thewater analyst willalsobe keeping an eye on the contents ofsurfacewaters and on what is discharged into the sewerage system,particularly those into which industrial plants discharge effluent(see Figure 1.6).The sudden arrival of a high concentration of atransition metal.at the sewage works, for example, can kill thebacteria used in the purification process. In the normal course ofevents, the sludge produced in the process is often used as afertiliser, so it is important that the concentration of potentiallytoxic metals isknown, asthese can have harmful effects on crops.Aswith the action of drugs mentioned earlier, there may wellbe aconcentration range in which the action of the metal isbeneficial,even desirable. The organism may suffer ill-health at metalconcentrations both below this range, because of a deficiency, andabove it, because of a toxic effect.Helping the Farmer. The role of agricultural chemists in increasing the efficiency of farming has already been mentioned.Analytical chemists play a role in monitoring the levels ofnutrients in soils, giving the farmer information of use indeciding how much of which fertiliser to apply (see Figure 1.7).There are a number of laboratorie around the country providing such a service to farmers through the skil ls of soil scientistsand agricultural analytical chemists. Levels of potentially harmfulmaterials willbe monitored, not only in the soil but also in cropsand animals. It isalso important to monitor levels of pesticides,weed killers, etc. applied to crops and soils that could pass alongthe food chain to us. The Ministry of Agriculture, Fisheries, and


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Figure 1.7 The analytical chemist helPs the farmer.Foods has laboratories which monitor the residual concentrationsof some of the components of animal feeding stuffs or veterinarydrug residues in meat. Detection and measurement of some ofthese components are often extremely difficult as they may bepresent at very low concentrations, and the requirements of theanalysis place severe demands on the analytical chemist's skill andingenuity.H elping to C atch C rimina ls. The work of the police in solvingcrimes and bringing the culprits tojustice isconsiderably helpedby analytical chemists. The specialised analysts involved in thistype of work are known as forensic (meaniIig 'related to the courtsof law') scientists. A lot of their work is concerned with estab-

Figure 1.8 The analytical chemist helps to catch criminals.

lishing a contact, i.e. was such-and-such a person at such-and-sucha place or was this vehicle at this place and so on (see Figure 1.8).Answering this type of question is based on the principle that'e\'ery contact leaves its traces', and the work may involvemicroscopic examination and the measurement of several of thechemical components. For example, when a hand gun isfired, thehand of the firer receives a small amount of powder, ejected fromthe muzzle and breech, arising from the propellant in the bullet.This material has a high concentration of antimony and barium,so if the hands of a suspect are swabbed and an unusually highconcentration of these' elements isfound then itmay mean that theperson has recently fired a gun.Victims of hit-and-run incidents may have fragments of paintor glass lodged in their clothing. Comparison of the traceelement concentrations in a glass fragment taken from thevictim's clothing with the trace-element concentrations in glassfrom the headlamp of a suspect vehicle may establish that the twomaterials could be tl,1esame. Different types of glass have differenttrace-element conc:entrations arising from variations in startingmaterials or in ~he manner of manufacture; so for examplewindow glass is easily distinguished from headlamp glass. Howeasily one headlamp isdistinguished from another isa problemwith which the forensic scientist has to grapple in puttingtogether a case to take to court. There are lots of other materialsthat may be transferred during a contact, such as clothing fibres,dust, soil, blood, and so on. Very often the forensic scientist isfaced with the problem that the amount of material available foranalysis is very small so that even if the components whichcharacterise the material are major components the final analysismay involve very low concentrations. For example, in the analysisof gunshot residues the amount of the material deposited is sosmall that even if the final volume of swab liquid is 0.5 cm3 theconcentration of the metals may only be at the part per million(p.p.m.) level. A 'p.p.m.' isa concentration equivalent to I Ilg (i.e.10-6 g) i n I cm3 The limited amount of material means that thereisno room for mistakes: the forensic scientist cannot ask for moreif the solution isspilled or contaminated accidentally, as you canin the teaching laboratory.Helping to E nsure Fa ir P lay. It is a sad reflection on the positionthat sport occupies in our society that some competitors resort toartificial means to increase their performance (see Figure 1.9). In


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12 Chapter 1 r I\'hat DoA nalytical Chemists Do?bulk I pretreated result or chemical d "materia 1-:-+ s amp e~ sample : number~information- eClslon

sampling physics, test or

pw"~\n"'lmen/7"ionAnalytical ChemistFigure 1.10 The various stages in the overall analytical method.

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Figure 1.9 The analytical chemist helps to detect drug abuse in sport .some cases the competitor may have no say in the matter, as forexample in the case of a racehorse or greyhound. The abuse ofdrugs in connection with sporting events is sufficiently wide-spread for a number of laboratories, admittedly a small number,to be involved in checking blood and urine samples for drugs ofthis type or their metabolites. The problems are formid


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The analytical chemist will not forget that if this sample is notrepresentative of the bulk material then any decision based on theinformation provided as a result of the laboratory proceduresmay be unsound.

FURTHER READINGB. Dixon, 'What Is Science For?', Penguin, Harmondsworth,1976.A. Isaacs, 'Introducing Science', Penguin, Harmondsworth,1972.'Chemistry and the Needs of Society', Special Publication No. 26,The Chemical Society, London, 1974.M.D. Wynne, 'Chemical Processing in Industry', Monograph forTeachers No. 16, The Royal Institute of Chemistry, London,1970.D.F. Ball, 'Some Aspects of Technological Economics', Monograph for Teachers No. 25, The Chemical Society, London, 1974.'Chemistry and Agriculture', Special Publication No. 36> TheChemical Society, London, 1979.'Understanding Our Environment', ed. R.E. Hester, The RoyalSociety of Chemistry, London, 1986.'Pollution: Causes, Effects and Control', ed. R.M. Harrison,Special Publication No. 44, The Royal Society of Chemistry,London, 1983.G.F. Lewis, 'Analytical Chemistry', 2nd Edn., Macmillan, London, 1985.R.A. Chalmers, 'Aspects of Analytical Chemistry', Oliver andBoyd, Edinburgh, 1968.D. Betteridge and H.E. Hallam, 'Modern Analytical Methods',The Chemical Society, London, 1972.G.E. Baiulescu, C. Patroescu, and R.A. Chalmers, 'Education andTeaching in Analytical Chemistry', Ellis Horwood, Chichester,1982.

Chapter 2Making Light Work

Examples of some of the materials about which analyticalchemists are requested to provide information are given in theprevious chapter. Thus analytical chemists are asked to provideinformation not only about the nature of the components of amixture, i.e. qualitative analysis (the identification of the chemicals), but also about how much of a particular component ispresent, i.e. quantitative analysis.Both categories of information may be provided by theapplication of the way that light and the material in questioninteract. For many of us the attraction of chemistry is ourperception of chemical reactions through the senses of sight,smell, and hearing. In particular, the colour effects produced bymany chemical reactions are a continued source of fascination.There are many analytical situations where the perception of theappropriate chemistry directly by eye is adequate to provide therequired information. There are fewer examples in which nosesand ears will do the same. However, there are also a great manyanalytical problems, for which the interaction of light isthe basisofthe appropriate solution, where the perceptive skill of the eye isinadequate. In these situations analytical chemists make use of anappropriate instrument that in effect extends the abilities of thehuman eye. One such situation isthe requirement to quantify lowlight intensities or small changes in light intensity. This in turnhas arisen from the requirement to provide information aboutcomponents of a mixture present at very low concentrations. Theanalysis of such components is known as trace analysis.

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Tyson. What Do Analytical Chemists Do

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