Performance of a time multiplex multiple slit multielement flame atomic absorption spectrometer

Abstract

The performance characteristics of a new multielement flame atomic absorption (AA) spectrometer are presented. Compared to a conventional single element AA, the absolute light level8 measured are considerably lower and additional spectral overlap problems arise. These differences do not significantly affect detection limits, sensitivities, precision, and calibration curves in most cases. Detection limits (in ppb) of 50 (Au), 8 (Cd), 40 (Co), 9 (Cu), 60 (Fe), 2 (Mg), 5 (Mn), 50 (Ni), 50 (Pb), and 20 (Zn) were obtained under favorable multielement conditions and are within a factor of two of detection limits obtained on a good quallty commercial slngle element AA operating with comparable spectral bandpass and integration time. The relative measurement precision at moderate absorbances is typically 1 % or better.The design and construction of a new multielement flame atomic absorption (AA) spectrophotometer were described along with a review of other multielement AA spectrophotometers in a recent paper ( I ) . This instrument is denoted a Time Multiplex Multiple Slit (TMMS) system. It is similar to a conventional single-element AA except that the light beams from four single element hollow cathode (HC) tubes are directed through the flame by the use of beam splitters and the exit slit is replaced by multiple exit slit array (one slit for each element). The light passing through all exit slits is directed to one photomultiplier tube (PMT). The HC lamps are pulsed on sequentially (one on a t a time) with a 12.5% duty cycle at a 12.5-Hz rate. Data acquisition is synchronized with the lamp pulsing such that the lamp signal from each element's HC lamp is directed to a separate data acquisition readout channel a t the proper time. To signal average, typically 100 ''laps'' or 10-ms duration lamp pulses are averaged for each element. The system is configured to determine simultaneously any four of the following ten elements:Cu, Mg, Pb, Mn, Au, Fe, Co, Ni, Cd, and Zn. In this paper the performance characteristics of this instrument are critically examined. EXPERIMENTALThe TMMS instrument and its general operation have been previously described ( I ) . For all flame AA ineasurements on the TMMS instrument, the burner air and CzH2 flow rates were 4.6 and 0.5 Ljmin, respectively, and the sample flow rate was 4.6 mL/min. The FMT bias voltage was adjusted to 60G800 V and R, was lo5 -10' R. Solutions were prepared from reagent grade metal salts and distilled and deionized water.The most common AA analysis lines were used in all cases except for Au and Pb. The Au 267.6 nm line provides an AA sensitivity and lamp intensity near those of the more common 242.8 nm line and avoids any possible overlaps with the Co 242.5 nm line and the Sn 242.1 nm line. The Pb 283.3 nm line was chosen as opposed to the normal 217.0 nm line because it is five times more intense and the AA sensitivity is within a factor of Present address, two of the 217.0 nm line. A Au slit was included on the mask because Au is a good internal standard element for corr...

Developments and Applications of Multielement Graphite Furnace Atomic Absorption Spectrometry

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Background-corrected simultaneous multielement atomic absorption spectrometer

“…Consequently, a comparison of SIMAAC noise levels to those of other systems is informative. Table II compares the electronic and 70 noise of SIMAAC, another multielement AAS (20), and a Varían Techtron AA-6 (78). For SIMAAC, a¡JI0 computed from base-line absorbance noise, this comparison shows the expected wavelength dependence.…”

Atomic absorption spectrometry with a photodiode array spectrometer

“…For multielement analysis the radiation from a second HCL was combined with the first by placing a polka dot beamsplitter in the optical path and the second HCL at right angles to the optical path as shown in Figure 2. This method of combining the output of HCLs is acceptable for perhaps as many as three lamps; however, as more beamsplitters are introduced tbe radiant throughput becomes too low for practical applications (13). The gas flow rates and burner position were optimized for each analyte species studied.…”

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