Optics: measuring and testing – By dispersed light spectroscopy – With sample excitation
Patent
1996-04-15
1998-06-02
Evans, F. L.
Optics: measuring and testing
By dispersed light spectroscopy
With sample excitation
G01N 2167
Patent
active
057608970
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a one-step process useful in the chemical analysis for atomising electrolyte solutions or fluids with electric conductivity, and a multielement direct analysis method of the components of such fluids, which is also operable in a monitoring mode. In this analysis method, the one-step atomisation of the fluid is followed by optical and/or mass spectroscopy determination of the sample components.
BACKGROUND ART
In many fields of optical spectroscopy (atomic absorption or atomic emission spectrophotometry, atomic fluorescence) and mass spectroscopy the precondition of measurement is the existence of the components in an atomic vapour state. The term: "atomisation" defines a complex process wherein an atomic aerosol is obtained from the sample by one or multistep energy transfer. In the following, the term: "atomisation" is used in this sense.
According to the prior art, most of the atomisation processes used for analytical purposes prepares first a coarse aerosol by pneumatic vaporisation of the electrolyte solution, which is then transferred into properly selected chemical flame of high temperature or plasma flame generated by high frequency (Boumans, editor: Theory of Atomic Emission Spectroscopy). In these processes the vaporisation step, due to the small sample requirement, is performed by capillary blotting or blow-slot method and accordingly, they can be used in the analysis of solutions which are predominantly clear and/or contain little amount of floating material, which would mean the necessity of inserting a pre-filtering step before vaporisation in many practical processes. The mass flow of atomisation, i.e. the amount of electrolyte atomised in a time unit is determined by the atomisation velocity, thus, regular cleaning of the vaporisation system and permanent control of the flow and pressure conditions is necessary. Another drawback of such processes is that atomisation by chemical flames needs a permanent and strict control due to the extraordinarily flammable and explosive gases (acetylene, dinitrogen oxide, oxygen) used therein. This disadvantage does not appear in the high frequency-generated plasma flame atomisation, but the high frequency unit is of complicated structure and high energy consumption.
Another method for solution atomisation used for analytical purposes is the electro-thermal, heating of a precisely determined quantity of electrolyte by programmed steps of evaporation, drying and vaporisation, the so-called graphite furnace atomisation. This method provides an advantageous high atom vapour concentration, however, the process is complicated and consists of multiple steps, automation of sample injection is difficult to accomplish, and continuous working mode is impossible due to permanent contamination of the graphite furnace by the non-evaporating parts of the electrolytes.
In the optical spectroscopy, other methods for quasi-continuous atomisation and analysis connected therewith in dude "weeping carbon electrode" method (Feldman, C.: Anal. Chem. 21: 1041/1949/), "capillary electrode carbon arc" method (Nalimov, V. V.: Zav. Lab. 23: 1351/1955/, Zink, T. H. Appl. Spectr. 13: 94/1959/), rotating disc electrode spark excitation (Pierucci, M. et al: Nuovo Cimento 17: 275/1931/) and feeding electrolyte in the spark gap (Twyman, F. et al: Proc. Roy. Soc. 133: 72/1931/). These methods have never been widely used due to their common disadvantage that during atomisation, irreversible deposits are formed on the solid electrodes, and accordingly, they cannot be used in continuous technologies.
As summarized above, the known analytical methods based on analytical chemical atomisation processes of electrolyte-containing fluids (atomic absorption, atomic emission, atomic fluorescence, mass spectroscopy) require a very thorough sample preparation, (filtration, recovery, dissolving), precise solution administration, permanent control (explosion risk in technology) and they are not suitable for continuous, control-free (monitoring) system.
A
REFERENCES:
patent: 2643574 (1953-06-01), Todd
patent: 4195641 (1980-04-01), Joines et al.
Cserfalvi Tamas
Mezei Pal
Aqua-Concorde KFT
Evans F. L.
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