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Automatisierung und Simultanbetrieb zweier handelsüblicher Atomabsorptions Spektrometer mit Flamme und elektrothermaler Anregung



1979
Kernforschungsanlage Jülich GmbH Zentralbibliothek, Verlag Jülich

Jülich : Kernforschungsanlage Jülich GmbH Zentralbibliothek, Verlag, Spezielle Berichte der Kernforschungsanlage Jülich 46, 32 p. ()

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Report No.: Juel-Spez-0046

Abstract: lt is extremely important in present day analysis that the data are obtained with high speed and accuracy. In many problems of trace analysis for quality control, it may be necessary to compute the data quickly and avoid manual data reduction which involves a great deal of time in addition to the risks of error. The present report briefly describes the work carried out by the Central Department for Chemical Analysis, KFA Jülich in collaboration with Fa. Beckmann and Wang to develop and set up a fully automatic system for processing the data from an atomic absorption spectrometer, both numerically and graphically. The heart of the calculating system (Wang 2200) is the Central Processing Unit (CPU) which has a warehouse of free access memory (RAM) via program steps or a data bank. The data bank can supply the data in steps from 4 K to maximum of 32 K. The arrangement is controlled via six on-off units by the CPU. The data and programme can be displayed by a Cathode Ray Tube (CRT) which has at its disposal an integrating unit, coupled to the magnetic tape data station which utilises an alphanumeric combination of BASIC programme keyboard network. A fast tape control system (Wang Disc 2270) is used to automatically control the various peripheral systems. All units are connected to an XY-recorder which can register the text and data network and provide a suitable plot of the output. In order to execute a programme, it is transferred to the CRT from the magnetic tape. The available information on the analysis is then recorded. Each analysis can be given a code number and analysed by a special programme if required. The calibration curve programme can be executed directly by obtaining data from the atomic absorption spectrophotometer. The standards and samples are put in an automatic sample changer and measured sequentially. A number of readings (7 per sample) are taken on each sample and the value is averaged over a period of time. A cleaning solution washes the capillary between two sample solutions. Further, a blank and a standard solution can be run from time to time for control and check of the calibration by special coding on the sample vials which transmit a signal to the microprocessor (blank, control or sample). The results can be computed by obtaining a calibration curve from which the samples are read off afterregression analysis. The method of standard addition can be used when the matrix has unknown composition. A format of the type y = a + bx is used and solved for the unknown constants. When the calibration curve is non-linear because of deviations from Beers law, the relation between concentration and extinction can be approximated by the formular c = m (E + nE$^{2}$). In this case one obtains a quadratic equation of two unknowns. These can be computed by use of two standard solutions, which allow the microprocessor to compute the corrected calibration curve and obtain the sample concentrations. The curvature correction can be made fully automatic through subroutines, "auto zero", "auto lin" and "auto cal". The system has been coupled to a Beckman Atomic Absorption Spectrometer 1272 M with a sampling change capacity of 250 probes and a Perkin Eimer Model auto sampler for the graphite tube furnace HGA 76 with a capacity of 30 samples. lt can be used simultaneously with two or more instruments and is simple and reliable.


Contributing Institute(s):
  1. Publikationen vor 2000 (PRE-2000)
Research Program(s):
  1. 899 - ohne Topic (POF3-899) (POF3-899)

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 Record created 2016-12-01, last modified 2021-01-29