Atomic absorption re-invented... ^ J Instrumentation Laboratory
At IL, we are continually reThe recent history of A A is one of small improvements. Not so at IL, where we're lucky enough t o have people w h o ignore preconceptions and take fresh looks at needs and possibilities. A t IL, atomic absorption is continually being re-invented.. It starts with something as basic as optics. Most A A optical systems use many mirrors. IL's engineers asked, " W h y not lenses?" Lenses are rugged where mirrors are touchy, they can double as w i n dows t o keep fumes out of the photometer, and not many are needed in a double-beam syst e m (Figure 1). Fewer optics
IL divulges analytical secrets. Microprocessors are a boon t o the analyst, but may conceal w h a t is really going on. In t h e ideal automated system, a sample is inserted and t h e instrument delivers "an answer." Is it "the answer"? Hard t o tell. All the intermediate information is hidden in the machine. IL's Video™ instruments, however, tell you a great deal. Figure 2 shows t h e simultaneous
The printer also tells all. Most A A printers give nothing but unidentified numbers, sometimes accompanied by a hard-to-decipher single-letter code. IL printers are different. The printout available in t h e IL951 (Figure 3) shows elements, conditions, date and t i m e , operator ID, selectable six-digit sequence numbers, and mean analytical results. It can also shov t h e values of t h e w o r k i n g curves as well as complete statistics. Figure 3. IL951 printout. Mean of several readings— —6-digit sample number Operator identification, date, time —| -4-second integration, no delay time Each reading repeated 3 times -
Figure 1. In IL double-beam design, lenses also serve as windows. mean a more efficient system because any o p t i c - lens, mirror, or w i n d o w - w a s t e s about 10% of the light. There is one objection t o lenses-focus changes w i t h wavelength. The solution: add an adjustable zoom lens. And now, t h e IL951 (IL's dual-element double-beam AA) has special achromatic lenses, which keep t h e focus constant over t h e whole wavelength range. Why should you care? Simpler optics are more efficient; lamps use lower currents, last longer; w o r k i n g curves are straighter and more sensitive; EDL sources, expensive and time-consuming, are not needed.
Figure 2. Figure shows the pyrolysis and atomization stages of the simultaneous determination of traces of copper and iron in beer with the IL555 CTF atomizer. furnace atomizer determinat i o n of t w o elements in beer. Cu and Fe are being run, w i t h background correction (indicated by -D). Most of t h e background absorption (dotted line) is removed by pyrolysis before atomization (solid line). You see what's happening. That's clearly better t h a n an unidentified and uncheckable reading of "0.044" (or "0.002" or "0.813" if the answer happened t o be wrong). Not t o mention t h a t you're seeing two elements. The IL951 is currently the only dual-element instrument.
For more information, circle Reader Service Number 95.
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inventing atomic absorption Easy operation or versatility? Or do you want both? Conventionally, you must choose between ease of operation and versatility. Once again, behold the magic of video. The IL551 Video I™ AA Spectrophotometer displays t h e "cookb o o k " values f o r all common elements and guides t h e operator step-by-step t h r o u g h the set-up procedure. Thus, it's easy t o use. It can display w o r k i n g curves and can show absorption peaks and background simultaneously. This helps make it versatile. For example, a new analysis w i t h t h e furnace atomizer can be developed in hours, not in days. The IL951 is even more versatile and is equally easy to use. As hundreds of labs n o w know, modern IL two-channel instruments can determine any t w o elements simultaneously, as easily as t h e IL551 measures one. The IL951 can even employ t h e
internal-standard mode t o get accurate results in unweighted and unmeasured samples. (You don't believe it? Ask for Report 114.) Low cost or high performance? Or both? All IL instruments, including t h e low-cost IL157 and t h e moderate-cost IL257, can provide the same fine performance. All IL AA's share these features: • Excellent 0.04 nm resolution. Competitors also recognize t h a t high performance requires high resolution, but provide it only in their top-ofthe-line instruments. • L/V'/Visible absorption spectroscopy is available on all IL AA instruments. Double-beam units can be used in true double-beam mode, w i t h sample and reference cells (See Report 106). An IL exclusive. • Working curves can be reentered from the keyboard. No need t o remake the working
curves for each new day's work. Re-enter them f r o m the keyboard. W i t h the Video instruments, store t h e m in memory. An IL exclusive. • New fail-safe drain trap. When a burner is used w i t h an empty drain trap, there can be a flashback. IL n o w has a simple but ingenious trap which is
Float rises, allowing liquid to flow over the top of the well and down the drain
With no liquid, the glass float rests on -bottom, preventing fuel from escaping
Hose filled with liquid from premix chamber
Inlet (hose from premix chamber)
Figure 4. New drain trap. never empty. (Figure 4). W i t h no liquid present, t h e float covers the hole. W i t h enough liquid, the float rises. Patent applied for.
The IL furnace atomizer measures temperature, analyzes solids. All furnace atomizers, including IL's, use a hollow graphite cylinder. That's where t h e similarity ends. Most designs deduce cylinder temperature f r o m a measurement of current and/or voltage. Accuracy depends on t h e graphite age, coating, and dimensions. Only IL uses a true thermometer, a tungsten based wire touching t h e graphite. Better accuracy improves versatility. To w i t : The IL furnace easily measures trace mercury, replacing the tedious cold-vapor method (Report 12); also, measures barium in seawater w i t h out background correction (Report 11). Many solids can be analyzed directly w i t h IL's microboat (U.S. Patent 3,895,873). Only IL has it. See Report 14 on Pb, Se, Zn, Bi, and Ag in undissolved nickel alloys and steels. IL's FASTAC™ Autosampler dramatically improves furnace analysis. Manual use of any furnace atomizer is tedious and errorprone. Fortunately, there are now many autosamplers, essentially automatic pipettors, available. Useful, but w e can do better. IL's FASTAC-Flame/Furnace AutoSampling technique w i t h Automatic Calibration-which deposits the sample as an aerosol mist provides an astonishing set of advantages: • It can be used f o r both flame and furnace. Saves t i m e , space and money. • Organic solvents such as MIBK can be used w i t h ease. W i t h conventional pipetting, such solvents run uncontrollably. See Figure 5* and Report 16 on transformer oils. Deposition t i m e : 50 sec Standard 5.0 ^ g / l (ppb)
Figure 5. Determination of As in Naphtha
»Sensitivity depends on deposit i o n time. Thus, the operator can choose t h e desired sensitivity. • W i t h some samples, sensitivity is much better than could ever be achieved before. See Figure 6. * Standard 1.0 m g / l
Standard 0.5 m g / l Sample
0.1 mg/l
Figure 6. Phosphorus in semiconductor rinse water. • Viscous samples are analyzed w i t h ease. The sample is merely diluted, and then deposited for a longer period in order t o regain the sensitivity. • The furnace drying stage is eliminated. Saves time and reduces errors. • The FASTAC reduces interferences. The cumbersome method of additions is rarely necessary. • If the method of additions is required, the FASTAC can run it automatically. IL's competitors know who the technical leader is. When IL has a good idea, the competitors recognize it quickly. Some examples: • IL introduced t h e first instrument t o compute and print statistics in 1977. Competitors showed theirs in '78. • IL introduced AUTO-CAL, or recalibration of a corrected w o r k i n g curve w i t h one standard, in 1977. Competitors came out in '78. They called it "Reslope." • IL showed " r u n n i n g m e a n " in 1978. Competition had it in '79. • Do you believe this? Everybody knows you can't do arsenic in organics, or phosphorus at l o w levels. Make us prove it. We'll do it easily.
• IL showed the IL551 Video A A in March '78. The first competitive CRTunit came out in July '79. Luckily for us, it's not as good as ours. • They even imitate our bad ideas. In 1976, w e connected desk calculators t o our AA's. Bad idea. They cost t o o much, are t o o complicated, and don't bring enough t o t h e party. By t h e time w e w i t h d r e w t h e o p t i o n , all the major competitors had introduced it. You need IL if you need: t h e best optics...versatility. And ease of operation...high performance at modest cost...a video system t h a t really shows what's happening...dual element capability...an auto-sampler that does more than pipet samples... UV/Vis absorption capability...a printer t h a t really g ives t h e data... a t r u ly sensitive, repeatable, and versatile furnace atomizer...the most advanced instrumentation available. For immediate interest, please call 617-658-5125 or w r i t e : Instrumentation Laboratory Analytical Instrument Division 56 Jonspin Road W i l m i n g t o n , MA 01887 Circle Reader Service Number 96 for interest w i t h i n 90 days. Circle Reader Service Number 97 for interest w i t h i n 1 year. Circle Reader Service Number 98 f o r scientific interest only.
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