Optics: measuring and testing – Sample – specimen – or standard holder or support – Fluid containers
Patent
1999-07-09
2000-03-28
Font, Frank G.
Optics: measuring and testing
Sample, specimen, or standard holder or support
Fluid containers
G01N 110
Patent
active
060438789
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to the analytical chemistry arts. It finds particular application in conjunction with the titrimetric analysis of microliter size samples. It also finds application in conjunction with instrumentation for electrochemical studies of microliter size samples and in studies where the rapid achievement of steady state conditions is desirable. Further, it finds application in conjunction with the electrochemical analysis of non-homogeneous samples. It is to be appreciated, however, that the invention is also applicable to other chemical procedures where precise microdelivery of a reagent is desirable.
I. Routine analysis of the chemical composition of fluids is important in a wide range of fields, including clinical diagnosis, food and drug industries, industrial process control, and environmental studies. Due to the accuracy and reliability that titrimetric methods provide, they are widely used in diagnostic tests.
For accurate results, however, laboratory expertise, relatively large sample volumes, and often devices with expensive micromechanical elements are required for titrimetric studies. In many areas, for example in forensic testing and clinical diagnosis, large quantities of a sample to be studied may be costly or not readily available. To maintain the accuracy of measurements as the size of the sample decreases, the cost of the titration equipment, and the level of skill required, generally increase. Automated addition of reagents further adds to the cost, particularly when delivering microliter size volumes or less.
II. Another analytical technique, the investigation of basic electrochemical reactions, is very important for industrial development in many fields, including semiconductors, the fuel industry, corrosion, quality control, and process monitoring. The rate of electrochemical reactions is limited by the rate of mass transport over the surface of the electrode.
However, the natural processes of diffusion can be accelerated by hydrodynamic electrochemical techniques.
Hydrodynamic electrochemical techniques with enhanced convective mass transport exhibit a number of advantageous voltammetric characteristics. The relative contribution of mass transport limitations with respect to electron kinetics is less pronounced. (Bard, A. J.; Faulkner, L. R.: Electrochemical Methods; John Wiley, (1980)). Steady state conditions (where the current is independent of potential scan direction and time) are attained quickly. Thus, measurements can be carried out with high precision. In addition, at steady state, double layer charging is not a factor.
Traditionally, one of the best methods of obtaining efficient convective mass transport uses a rotating electrode system, such as a rotating disc or ring-disc electrodes. In the latter case, the electrochemically generated species at the disc are swept by laminar flow past the ring, where they can be monitored. Both electrode types have proven to be useful in basic electrochemical studies, such as those of coupled homogeneous reactions (Kissinger, P. T. and Heineman, W. R., Laboratory Techniques in Electroanalytical Chemistry; Marcel Dekker (1984)) and short lived reaction intermediates (Zhao, M. and Scherson, D. A., 64 Anal. Chem. 3064-67 (1992)). Hydrodynamic methods also play an important role in electrochemical preconcentration techniques, such as stripping voltammetry or potentiometry, where enhanced mass transport allows for efficient extraction of the analyte on to the surface of the electrode. Preconcentration of heavy metal trace elements is particularly useful for the analysis of food, environmental, and biological samples, because of the large useful concentration range (1-10-2M), and the simpler, portable and less expensive instrumentation (Bersier, P. M., et al., 119 Analyst 2195-32 (1994)). Potentiometric stripping techniques have been used successfully in the determination of lead in blood samples (Jagner, D., et al., 6 Electroanalysis 285-91 (1994)), in gasoline (Jagner, D., et al., 267 Anal.
REFERENCES:
patent: 5658723 (1997-08-01), Oberhardt
Cserey Andrea
Gratzl Miklos
Hui Kwong Yue
Case Western Reserve University
Font Frank G.
Stafira Michael P.
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