Part I: Fu ndam en tals and Ins tru m en tat ion 29 6 Complete Instruments In this section an attempt will be made to review the currently available range of commercial instruments as well as significant laboratory-built equipment. Unfortun- ately, the coverage of commercial instrumentation is more uneven than the compilers would have wished. The main causes of this have been threefold, namely: variation in the response from manufacturers t o requests for information on recently introduced instruments, problems of establishing the availability of equipment throughout the * J. Lacy, J. M. Skinner and C. Woodward, 3rd SACConference, Durham, (1971), Paper €315. 30 Part I: Fundamentals and Instrumentation world and the basic difficulty of becoming aware of all models from all manufacturers.Regrettably, therefore, this listing will inevitably be incomplete. Information from readers on any conspicuous omissions will be of great assistance in compilation of the second volume of this report and consequently will be welcomed by the editors. Despite these limitations it is felt that the information below is of considerable potential value t o readers and it is hoped that they will find it useful. 6.1 ARClSPARK EMISSION SPECTROMETERS Photographic emission spectroscopy, a long-established technique, is now used mainly in conjunction with other analytical methods for miscellaneous inorganic analysis. During the past decade, the more important instrumental developments have been in multi-channel direct-reading spectrometers frequently with associated computer facil- ities.These are, however, necessarily rather expensive because of the electronic requirements for detection and data-processing. Recent developments of less costly, sequential, integrating spectrometers using a single detector are therefore to be welcomed by users whose financial resources are not unlimited. The ARL 33,000 (185, 663, 1076, 1077) and Carl Zeiss Jena DSA 240 are examples of this type. These appear, along with other currently available commercial arclspark emission spectro- meters, in Table B. Dudeney (9 58) has discussed the difficulties encountered by instrument manufac- turers attempting to produce many identical spectrometers. His experience was based on Baird Atomic’s supply of forty instruments to an inflexible specification for the U.S. government. 6.2 FLAME EMISSION Commercial instrumental developments in flame emission spectroscopy are in two main areas: (a) the automation of simple, often filter, photometers to permit easy handling of large numbers of samples, (b) introduction of flame- or plasma-based instruments operating at a temperature high enough to excite most elements, with a monochromator capable of resolving the resulting emission spectrum sufficiently to permit simultaneous or sequential multi-element analysis. Examples of both of these classes are given below. Several manufacturers produce rather similar flame emission spectrophotometers designed basically for use in clinical laboratories where rapid handling of large numbers of samples is essential.Such instruments frequently have two measuring channels, normally used for Na and K, with Li measured as an internal standard. Depending upon the model selected, emission readings may be integrated and read out on a meter scale or displayed digitally. The full sample-handling capacity is realised if an auto- matic sample changer is used together with a printer unit. These accessories permit unattended operation for periods of an hour or more and provide almost fully auto- mated systems at modest cost. Instruments of this type are supplied by, amongst others, Baird-Atomic Inc. (model KY-3), Instrumentation Laboratory Inc. (models 143 and 343), Shandon-Southern Instruments Ltd.(model 1740), Evans Electro- selenium Ltd. (models 170, 227 and 450) and Beckman. At least two manufacturers (Spectrametrics Inc. and Hitachi) produce emission instruments in which the excitation source is a plasma. To a degree the performance of TABLE B COMMERCIALLY AVAILABLE EMISSION SPECTROMETERS Identification Supplier Description V-70 Vacuum instrument serving as production control polychro- mator or research tool. Wavelength scanning facility, Angstrom-West Division Angstrom Inc 600 Fig Avenue, Monrovia Calif. 91016, U.S.A. Quantometer 3 1,000 1 m vacuum grating, 170-407 nm, up to 80 elements, 60 simultaneously. Quantometer 33,000 Applied Research Laboratories SA, En Vallaire CH- 1024 Ecublens Lausanne Switzerland Integrating sequential analysis using programmable cards.Gratings range (1) 256-610 nm, ( 2 ) 170-407 nm. Also suitable for flame emission. Quantovac 80 Similar to Quantometer 3 1,000 but with new electronic console. Quantometer 80 1 m grating, 190-610 nm, up to 80 elements, 6 0 simultaneously. Applied Research Laboratories Ltd., Wingate Road Luton, Bedfordshire England Quantovac 29,500 1 m grating, 170-235 nm, 2160 lines/mm. Blazed for 200 nm, up to 1 8 elements. No details available Baird-Atomic Inc Bedford Mass. 01730, U.S.A. See Applied Research Laboratories Bausch and Lomb PGS-2 Q- 24 VEB Carl Zeiss Jena German Democratic Republic DSA- 24 0 2 m plane grating spectrograph, 200-280 nm. Prism spectrograph, 200-580 nm covered in one photograph.Quartz prism scanning spectrometer, 210-550 nm. Dispersion 0.78 am/mm a t 250 nm. Automatic recorder with tape punch and reader. C.Z. Scientific Instruments Ltd Zeiss England House 93/97 New Cavendish Street London W1A 2AR, England See Rank Precision Industries. Hilger and Watts TABLE B COMMERCIALLY AVAILABLE EMISSION SPECTROMETERS - continued ~~~ ,- Description Identification Supplier 66-000 Compact Atom-counter 65-100 Vacuum Atom-counter Jarrell-Ash/Fisher 590 Lincoln Street Waltham Mass. 02154, U.S.A. Direct reading, 190-800 nm, up to 60 elements. Vacuum attachment (66-070) permits C and S determination. Direct reading. Up to 45 elements including C, S and P in steel. V A Howe & Co. Ltd 88 Peterborough Road London S.W.6, England 70-310 70-314 66-750 78-090 3.4 m Ebert spectrograph with photographic or direct reading detection.Range 200-300 nm, dispersion 0.5 nm/mm. Relatively inexpensive direct reader, up to 30 elements. 1.5 m Wadsworth spectrograph. Choice of gratings to cover 420-960 nm or 210-480 nm. Resolution of 0.01 nm, aperture €/24. No information received. Jobin Yvon 26 Rue Berthollet 94 Arcueil (Seine) Paris, France PV 8300 (Philips) Vacuum direct reader featuring new measuring console (PV 8700). Up to 80 elements. Gratings (1) 1200 lines/mm, 170-430 nm; (2) 1440 lines/mm, 177-407 nm. MBLE 80 Rue des Deux Gares Brussels, Belgium ESA 1 Stigmatic plane grating 2160 lines/mm. Sequential analysis.ESA 3 Optica S.A.S. 20139 Milano Via Gargano 21 Italy Czerny-Turner plane grating, 21 60 lines/mm. Vacuum. Dispersion 0.36 nm/mm. Used as polychromator (9 elements) 177-217 nm or monochromator 160-500 nm. Polyvac E600 Direct reading vacuum instrument. 2 X 66" fluorite prisms 177-310 nm. Up to 25 elements. Various options in data presentation. E800 Rank Precision Industries Ltd Analytical Division Hilger and Watts 31 Camden Road London N.W.l, England Direct reading air-path instrument for production control. Up to 35 elements. Polyvac E 1000 Computer-controlled direct reading vacuum instrument. Dual gratings give 6 systems in range 159.6-864.3 nm. Dual spark chamber system available. Up to 60 elements. R.P.I.Inc. 260 North Route Westnyack N.Y. 10994, U.S.A. €398 Medium Quartz E742 Large Quartz 0.6 m prism, 200-1000 nm, available with direct reading attachment (E54 9). Well-known, “classical” 1.1 m prism spectrograph. 191 -800 nm. a.c. spark or d.c. arc excitation. E l I I I1 18 1 .5 m Czerny-Turner grating spectrographs, 1200 lines/mm. 200-1200 nm, aperture f/20. 3.5 m spectrometer. No details available. RSV GmbH, 8031 Hechendorf/Pilsensee West Germany Analymat 1.5 m spectrometer, choices of gratings and readout units. Glow discharge excitation. Automatic sample changing. No details available. GV-200 Shimadzu-Seisakusho Ltd. 14-5 Uchikanda 1-chome Chiy oda-ku Tokyo 101, Japan Spectraspan 101 Spectraspan 201 Spectraspan 401 Compact spectrometers using Echelle grating with prism order separation. Dispersion 0.04 nm/mm at 200 nm.Incorporate argon plasma jet excitation source for liquids and gases, DC arc for solids. Spectrametrics Inc. 2nd Avenue Burlington Mass. 01803, U.S.A. Techmation Ltd. 58 Edgware Way Edgware Middlesex HA8 8JP, England 1802 1500 SP Spex Industries Inc P. 0. Box 198 Metuchen N.J. 08840, U.S.A. 1 m Czerny-Turner spectrograph/spectrometer. Grating/camera provides 9 in. (200 nm) of spectrum in one exposure. f/8.4. Versatile 0.75 m Czerny-Turner vacuum instrument. Optimum range 110-250 nm, aperture f/6.8, dispersion 1.1 nm/mm. 1500 DP Versatile 0.82 m Czerny-Turner vacuum instrument. Choice of gratings, aperture f/7.4. Dispersion 0.5 nm/mm.Glen Creston The Red House 31 The Broadway Stanmore, Middlesex England 34 Part I: Fundamentals and Instrumentation these is intermediate between that of a flame emission spectrophotometer and of a direct-reading arc/spark spectrometer. Spectrametrics have two instruments giving single element (model 101 ) or simultaneous ten-element (model 20 1) analyses, the sample being nebulised into an Ar plasma with excitation temperature approximately 10,OOOo K. Optical dispersion is by means of an Echelle grating crossed with a prism which yields a dispersion of approximately 0.04 nm/mm at 200 nm. The Hitachi model 300 similarly uses an Ar plasma torch, excitation temperature -7000° K, with nebulisation of the sample, via a heating chamber, into the plasma flame.Multi- element analyses are obtained by use of the scanning monochromator. These instru- ments are of the type needed if the capabilities of emission spectroscopy as applied t o liquid samples are t o be realised, i.e. sample introduction is simple, excitation is efficient and optical dispersion is adequate t o permit simultaneous or sequential multi-element analysis. It should be pointed out that, in addition t o those instruments described above, most standard atomic absorption spectrophotometers also have flame emission capabil- ities. Other interesting work on complete flame emission instruments has included Mavrodineanu's description (443, 887, 929) of a flame spectrometer designed and built at the National Bureau of Standards, Washington.This consisted of a 1.0 m spectrometer with multi-channel phototube housings, signal integration and print-out facilities and a punch-tape arrangement for computer calculations. The instrument could be used as a monochromator, spectrograph or multi-channel spectrometer. in the last mode, simultaneous determination of eight elements by emission or six by emission and two by absorption was possible. Several groups have described complete systems for carrying out automated analyses by flame emission. Bissett et a1 (894) discussed practical problems such as baseline correction, time compensation for handling delays, minimisation of carbon build-up and burner memory effects, in the continuous determination of Ca in brine.i n a typical biological application, a combination of an IL 143 flame photometer, IL 144 dilutor and Technicon Sampler I1 has been applied (208) t o the automated flame photometric determination of serum Na and K. Two applications have appeared of flame photometric detection following gas chromatographic separation both of which actually rely on detection of emission of molecular species. A Tracor inc. flame photometric detector has been linked with a Hewlett-Packard model 5750 gas chromatograph for detection of P and S in pesticide residues in foodstuffs (10). Secondly, a modified Beckman DU with the photocells replaced by an EM1 9601B photomultiplier and a capillary burner supporting an N2 /H2 diffusion flame has been designed for detection of relatively volatile fluorides (1 38).6.3 SPECIALISED EMISSION INSTRUMENTS Refinements to direct-reading spectrometers t o provide more rapid analyses, e.g. high- repetition source units, are only short-term improvements on the present situation. The real need in industries using spectrometers for process control is for analysis in situ, e.g. of steel while molten. Bojic and Barbier (557) described preliminary labor- atory work with this aim which yielded some encouraging results but was, as the authors pointed out, still far removed from being applicable to a practical situation. Three other interesting instruments are note worthy. Part I: Fundamentals and Instrumentation 35 A small portable polychromator has been developed (27) to monitor O2 and H2 products in the W arc/inert gas welding process.The H 656.28 nm and 0 777.19 nm lines were monitored with the Ar 852.14 nm line as internal standard. To allow for variable arc position, the focusing assembly was mounted on the torch head and a fibre optic bundle transmitted the light t o the spectrometer. An oscillating prism in the entrance beam produced an a.c. signal above the d.c. background and the read-out was sensitive only t o signal above background. Gram et a1 (904) described an emission-resonance dedicated instrument for Hg detection in pollution monitoring which used a demountable hollow-cathode lamp, resonance detection and a phase-sensitive subtraction type lock-in amplifier. Mainka and Baeckmann (574) compared emission spectroscopy using a 3.5 m spectrometer with mass spectrometry for isotope analysis in fissile materials. Emission lines must be narrow and clearly high resolving power is of paramount importance.The authors were unable t o determine Pu241 using arc excitation because the line half-widths (S eff = 0.0035 nm) were too large t o permit adequate separation between lines from different isotopes. 6.4 ATOMIC ABSORPTION/FLUORESCENCE SPECTROMETERS Descriptions of commercial instruments in the scientific literature have included: the Jarrell-Ash Model 800 dual double-beam spectrometer (660), the Perkin-Elmer single- beam Models 103 and 107 (93) and double-beam Model 306 (94). Thomerson (194) showed that the performance of the Pye-Unicam SP90 was improved significantly by the use of a nebuliser impact bead and aperture stops.A testing routine for a new atomic absorption instrument has been presented by Perkin-Elmer workers (889). A single-beam atomic absorption spectrometer (850) has been built which can compen- sate for variations in source intensity and non-specific absorption. Source radiation was passed through the atom reservoir and detected using a repetitively scanning monochromator with both a.c. and d.c. amplifiers. The ratio of the two signals was related t o concentrations. A spectrometer which measures the sum of atomic fluore- scence and emission signals has been constructed (122) for the determination of wear metals in lubricating oils. Few advantages of this approach over conventional atomic absorption could be claimed.A digital atomic fluorescence spectrometer, designed (1 20) for the determination of Se gave a limit of detection of 0.1 mg 1-l Se. The possibilities of on-line process control using atomic absorption have been explored (874, 922, 942), and a list of required specifications compiled. The main problems are those associated with safety, stability and automatic control. Automatic feed back control of the industrial process has also been discussed. Table C summarises currently available commercial atomic absorption spectro- photometers. 6.5 NON-DISPERSIVE INSTRUMENTS Atomic fluorescence spectroscopy has found little application in practical analysis t o date and has few advantages over atomic absorption.However, AFS easily lends itself t o non-dispersive analysis because of the selectivity of excitation obtainable with a modulated light source. In this way only the fluorescence of the element of interest is excited; the whole of the fluorescence spectrum being measured instead of only one wavelength. As there are few positional limitations a number of light sources may be arranged round the flame and can be used for simultaneous multi-element analysis if a suitable gating system is used. TABLE C COMMERCIALLY AVAILABLE INSTRUMENTS FOR ATOMIC ABSORPTION SPECTROSCOPY Identification See OCLI Instruments Model 440 Model 444 Model 44 8 Model 485 Model 495 Supplier Aztec Instruments Beckman Instruments Fullerton, Calif.92634, U.S.A. Bausch and Lomb 142 Linden Ave., Rochester, N.Y. 14625, U.S.A. ARL Ltd Wingate Road Luton, Bedfordshire Carl Zeiss 7082 Oberkochen Wiirttemburg, W. Germany Cary Instruments Evans Electroselenium Ltd Halstead, Essex, England Description Single beam, single- or triple-pass optics, grating 1200 lines/mm blazed at 250 nm, resolution to 0.2 nm, automatic filter selection, three lamp turret. Double or single beam, single- or triple-pass optics, grating 1200 lines/mm, blazed at 250 nm, resolution to 0.2 nm, automatic filter selection, three lamp turret. Single beam, single-pass optics, grating 1200 lines/mm, blazed at 250 nm, resolution to 0.2 nm, automatic filter selection, three lamp turret. Double or single beam, single- and triple-pass optics, grating 1200 lines/mm, blazed at 250 nm, resolution on 0.2 nm, automatic filter selection, 50 X scale expansion, meter display.As model 485, 100 X scale expansion, digital display. Range 190-800 nm with wavelength drive, 10 X scale expansion, direct concentration read-out. Double grating monochromator, 3-speed wavelength drive, automatic stray light and 2nd order filter selection. Use also as emission or UV solution spectrophotometer. FA-1 and FA-2 attachments for PMQ I1 spectrophotometer. Variety of single or double grating of prism monochromators available. Total comsumption or laminar flow burners. Converts to UV solution spectrophotometer. Single beam, 0.25 m modified Czerny-Turner monochromator, grating 576 lineslmm, dispersion 7 nm/mm, non-linear dial read-out, single lamp turret, inexpensive.Spectronic 760-AA Spectronic AC2-20 PMQ I1 See Varian-Techtron. EEL 140 EEL 240 Single beam, 0.25 m modified Czerny-Turner monochromator, grating 576 lineslmm, dispersion 6.6 nm/mm, f/lO aperture, 4 lamp turret, integration, meter read-out. See Jarrell-AshiFisher Fisher Scientific Co. Modular System Heath/S chlumberger Benton Harbor, Mich., 49022, U.S.A. Modular AA, flame emission, UV spectrophotometer with double or single beam optics and various amplifier/detector types. Model 5960A Simultaneous, multielement AAS for 6 elements, no longer produced. Hewlett Packard Palo Alto, Calif. 94303, U.S.A. See Rank Precision Industries. Hilger and Watts Hitachi 208 Single beam, Czerny-Turner monochromator, grating 1440 lines/mm, dispersion 1.8 nm/mm, 3 lamp turret, 20 X scale expansion, meter read-out directly in concentration, wave- length drive.Hitachi Ltd Nissei Sangyo Co. Ltd. 15-1 2 Nishi-Shimbashi ZChome, Minato-Ku, Tokyo, Japan. IL 153/353 Instrumentation Laboratory 11 3 Hartwell Ave., Lexington, Mass. 02173, U.S.A. Double beam, dual-channel, 0.35 m Ebert monochromator, grating 1200 lines/mm, dispersion 2.5 nm/mm, aperture f/9, six lamp turret, autocalibrate, autozero, integration, wave- length drive, digital display. IL 253 P K Morgan Ltd., 10 Manor Road Chatham, Kent. Single channel, double-beam, digital read-out, wavelength drive. Full specifications not available.Dial Atom I1 Single beam, 0.25 m Czerny-Turner monochromator, grating 11 80 lines/mm, dispersion 3.3 nm/mm, aperture f/7.5, two lamp turret, 10 X scale expansion, meter read-out. Jarrell-Ash/Fisher 71 1 Forbes Ave., Pittsburgh, Pa. 15219, U.S.A. Atomsorb Single beam, 0.25 m Ebert monochromator, grating 11 80 lines/mm, aperture f/3.6, up to 6 lamp turret, 20 X scale expansion, meter read-out. V A Howe & Co. Ltd 88 Peterborough Road London S.W.6. Model 82-500 (Maximum Versatility) Single beam, 0.5 m Ebert monochromator, grating 1180 lines/mm, various options available on gratings, slits and wave- length drive, multi-pass optics, six lamp turret, 20 X scale expansion. Dual double beam, predecessor of Model 810.Model 82-800 TABLE C COMMERCIALLY AVAILABLE INSTRUMENTS FOR ATOMIC ABSORPTION SPECTROSCOPY - continued Identification ~ ~~~~~ Model 82-810 Model 82-600 Supplier V A Howe & Co. Ltd. 88 Peterborough Road London S.W.6. Jobin Yvon 26 Rue Berthollet 94 Arcueil (Seine), France OCLI Instruments 132 Water St., South Norwalk, Conn. 06854, U.S.A. Optica Via Gargano 21-20139 Milan, Italy Perkin-Elmer Corp. Norwalk, Conn. 06854, U.S.A. Description Double beam, dual channel, two 0.4 m Ebert monochromators, gratings 1180 lines/mm, dispersion 2.1 nm/mm, 5 speed wave- length scan, integration, autozero, digital display. Simultaneous multielement (12 elements), 0.75 m spectrograph, concave grating 1180 lines/mm, meter read-out with magnetic needle lock.No information received. Previously sold by Aztec Instruments. Single beam, 0.5 m Czerny-Turner monochromator, grating 1200 lines/mm, dispersion 1.6 nm/mm, 3 or 6 lamp turret, purgeable mono- chromator, rotating optical bench. Single beam, 0.35 m Ebert monochromator, automatic filter insertion, pre-focused water-cooled hollow cathode lamps, integration, digital display. Single beam, 0.27 m Littrow monochromator, grating 1800 lines/mm, dispersion 1.6 nm/mm, single lamp turret, autozero, 50 X scale expansion, integration, meter display. As Model 103 with digital display. Single beam, 0.4 m Czerny-Turner monochromator, UV grating 2880 lines/mm, dispersion 1.0 nm/mm, VIS grating 1800 fines/mm, dispersion 1.6 nm/mm, changeover 420 nm, automatic filter insertion, single lamp turret, autozero, auto- concentration, curve corrector, 40 X scale expansion, gas flow interlocks, D, background corrector, digital display.Double beam, monochromator specification as Model 300, single lamp turret, % absorption meter display. As Model 303, absorbance meter display, concentration display on counter, Model 403 or 107 burner option. Atomic Analyser Mark 2 Model 6000 Model 103 Model 107 Model 300 Model 303 Model 305 Model 306 As Model 305, digital display, autozero, auto-concentration, curve correction, Model 403 burner. Model 403 As Model 306, automated flame ignition/extinguishing and safety monitoring. See Pye Unicam. Philips SP 90 Series 2 F'ye Unicam Ltd York S t , Cambridge England SP 1900 Single beam, Littrow monochromator, 30" rear aluminised silica prism, dispersion 3 nm/mm at 200 nm, 6 nm/mm at 250 nm and 32 nm/mm at 400 nm, three turret accessory, 10 X scale expansion, meter display.Single or double beam, Ebert monochromator, grating 1800 lines/mm, dispersion 2.2 nm/mm, 20 X scale expansion, 10 X scale contraction, integration, 6 lamp turret, digital display. As SP 1900 but with single lamp turret. SP 1950 Atomspek Mark 2 Single beam, 60" silica prism monochromator, dispersion 1.7 nm/mm at 200 nm, 44.6 nm/mm at 500 nm, 6 lamp turret, meter display, scale expansion. Rank Precision Industries Hilger and Watts 31 Camden Rd., London N.W.l, England A-3000 Single beam, 0.25 m Czerny-Turner monochromator, grating 700 line/mm, dispersion 6.0 nm/mm, four lamp turret, 10 X scale expansion, meter display.Shandon Southern Instruments Ltd., Frimley Road, Camberley Surrey, England AA-600 Single beam, 0.35 m Czerny-Turner monochromator, two lamp turret, 10 x scale expansion, meter display, wavelength drive. Shimadzu-Seisakusho Ltd 14-5 Uchikanda 1-chome Chiy oda-Ku Tokyo 101, Japan MAF-1 Single beam, simultaneous analysis for up to 4 elements, 0.5 m Ebert monochromator, grating 1200 lines/mm, dispersion 1.66 nm/mm, aperture fi8.5, four-pass optics, wavelength drive. MAF-2 As MAF-1 but with additional reference channel including independent monochromation/detection. TABLE C COMMERCIALLY AVAILABLE INSTRUMENTS FOR ATOMIC ABSORPTION SPECTROSCOPY - continued Description Identification Supplier Spectraspan 101 Spectraspan 201 Spectraspan 401 Spectrametrics Inc.2nd Ave., Burlington Mass. 01803, U.S.A. Compact spectrometers using Echelle grating with prism order separation. Dispersion 0.04 nm/mm at 200 nm. Although intended primarily as emission instruments they can be used for AA with a Xe continuum source and photoelectric or photographic detection. AFS -6 Technicon Industrial Systems Tarrytown, N.Y. 10591, U.S.A. Multielement spectrometer for simultaneous analysis of 6 elements by non-dispersive atomic fluorescence/emission using filters. Direct concentration read-out on printer. Hollow cathode or electrodeless discharge lamps.Not an AA instrument but included for completeness. AA-5 Single beam, 0.5 m Ebert monochromator, grating 638 lines/ mm, dispersion 3.3 nm/mm, aperture f/lO, four lamp turret, 10 X scale expansion, autozero, meter display. Varim-Techtron 679 Springvale Road N. Springvale, Vic., Australia 3 17 1 AA-120 Single beam, 0.25 m Ebert monochromator, grating 1276 lines/mm, dispersion 3.3 nm/mm, aperture f/10, four lamp turret, 10 X scale expansion, 2 speed wavelength drive, autozero, meter display. Varian Associates Ltd Russell House, Molesey Road Wal ton-on-Thames Surrey, England Model 1000 Single beam, 0.25 m Czerny-Turner monochromator, grating 1276 lines/mm, aperture f/8, four lamp turret, 10 X scale expansion, autozero, meter display.0 P Part I: Fundamentals and Instrumen tation 41 Work on a non-dispersive instrument for atomic fluorescence was carried out as far back as 1967". However, the problems presented by emission from high concentra- tions of Nay for example, precluded formal publication of this work. Although the emission problem could not be solved by modulation, the additional use of solar-blind photomultipliers? , responding t o ultraviolet but not visible radiation, overcame the difficulty. The wide optical acceptance angles of monochromatorless systems can improve the atomic fluorescence limits of detection over those obtainable with disper- sive instruments, and the short path-lengths involved may improve performance in the far ultraviolet. Work at the C.S.I.R.O. in Australia (121, 168, 673, 674) has been directed at evaluating the various components of non-disp ersive instrument at io n : high-int ensit y hollow cathode, conventional hollow cathode and vapour discharge lamps with several premixed flames, both separated and unseparated. The best limits of detection obtained (673) were frequently factors of ten better than those obtained using a monochromator instrument. The separated air/C2H2 flame was found to be best for general purposes (674), and N2 separated N2 O/C2 H2 flame gave adequate detection limits for some elements and could be improved further by noble gas shielding. The N2 O/Hz flame was generally unimpressive. Other monochromatorless systems have been reported by Elser and Winefordner (37) who used electrodeless discharge tubes and H2 /Ar/entrained air flames supported on a total-consumption burner for Cd, Hg and Zn. Marshall and Smith (506) deter- mined Zn and Fe in air/H2 flames also using electrodeless discharge tubes for excit- ation. Simultaneous, multi-element analysis using non-dispersive atomic fluorescence has been commercially developed in the Technicon AFS-6 instrument (882). This six channel instrument is based on the design of Mitchell and Johanssonz, and employs pulsed hollow-cathode lamps to stimulate the atomic fluorescence. The fluorescence emission is focused on to a photomultiplier after passing through an interference filter. The filters for each element are stepped into the optical path in sequence with the pulsing of the hollow-cathode lamps. A few applications have been described (1 5 1 , 483, 1019) and more may be expected from users whose high workloads justify the cost of such an instrument.