Electrolysis: processes – compositions used therein – and methods – Electrolytic analysis or testing – Involving enzyme or micro-organism
Reexamination Certificate
1999-08-16
2002-06-25
Tung, T. (Department: 1744)
Electrolysis: processes, compositions used therein, and methods
Electrolytic analysis or testing
Involving enzyme or micro-organism
C205S789000, C205S787000, C204S409000, C204S403060, C204S411000, C422S051000, C422S082010
Reexamination Certificate
active
06409909
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority of the Swiss application 64/97, filed Jan. 14, 1997, the disclosure of which is incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
The invention is related to process monitoring, especially a sensor system for the process monitoring technology, which allows the continuous and selective determination of various measured parameters.
STATE-OF-THE-ART
Sensor systems are known and described by the state-of-the-art.
The most well known systems for continuous monitoring are FIA-systems (flow-injection analysis). said systems consist of an extensive fluidics-system having pumps and valves. They make use of traditional analytical procedures using reagents and, occasionally, biosensors or ion-selective electrodes (ISE) at the end of the flow-system as detectors.
The known sensor systems are solely defined and specified by the application of potentiometric or voltammetric (electrochemical determination of the variation in the oxygen partial pressure) or amperometric or optical measuring techniques. The company YSI (2700 SELECT) offers an instrument equipped with biosensors for continuous process monitoring. The sensor elements are inserted into a miniaturized measuring chamber, which is filled with the specimen and evacuated therefrom. The amperometric and voltammetric systems involve biosensors and miniaturized modified electrodes such as “glassy carbon” or carbon Paste″graphite electrodes [compare Kalcher, K.; Kauffmann, J.-M.; Wang, J.; Svancara, I.; Vytras, K.; Neuhold, C.; Yang, Z. Electroanalysis 7/1 (1995) 5-22 (Review)]. Publications involve especially arrays (serial switch of a multitude of identical sensors, being identical with respect to their principle of function, on a geometrically defined sensor surface) using miniaturized sensors, so-called solid-state electrodes and ISFETs (ion-selective field-effect transistors) respectively [see Schindler, J. G.,: Schindler, M. M.; Herna, K; Reisinger, E.; Kulmann, U.; Graef, R.; Lange, H.
Biomed Tech
36/11 (1991) 271-280, 282-284. (HCA 116:136186.; van der Schoot, B. H.; Jeanneret, S.; van den Berg, A.; de Rooij, N. F.
Sensors and Actuators B
15/1-3 (1993) 211-213;
1
Hoffmann, W.; Rapp, R.; Ache, H. J.;
Stolze, D.; Neuhaus, D.; Hofmann, D.; Freywald, K. H. Micro Total Anal. Syst., Proc. &mgr;-TAS '94 Workshop, 1st (1995), in van den Berg, A.; Bergveld, P. (Eds). Dordrecht: Kluwer, Netherlands.
These systems lack on the one hand the ruggedness, especially of the structured layer and of the reference system, on the other hand, the flexibility, to integrate novel developments. Depending on the fabrication process, they can be optimized for a limited selection and limited number of types of selective layers only. Therefore, the applications are considerably restricted. Modifications of micro-structured sensor platforms are rarely advantageous and only if extremely large numbers of pieces can be produced. On the other hand, due to their unsatisfactory ruggedness and long-term stability, miniaturized sensors are primarily marketed as “one-way” sensors (i-STAT). This induces the production of waste of precious materials.
Continuous monitoring systems generally require the possibility of recalibration in order to guarantee a high reliability of the results. Nevertheless calibration-free systems were evaluated [Rumpf, G.; Spichiger, U. E.; Bühler, H.; Simon, W.;
Anal. Sciences
8 (1992) 553-559.]
The selective determination of specific components of a mixture of substances is solely feasible upon applying so-called selectivity principles.
A large number of selectivity principles based on recognition molecules, such as selective ligands, or effective selectivity principles based on partition equilibria, are known [Fluka-catalogue “Selectophore™”, 1996]. The development of some of these selectivity principles such as the magnesium-, nitrite-, heavy metal-selective ligands and layers have been considerably developed [Schaller, U.; Bakker, E.; Spichiger, U. E.; Pretsch, E.
Talanta
41/6 (1994) 1001-1005; Spichiger, U. E.; Eugster, R.; Citterio, D.; Li, H.; Schmid, A.; Simon, W. In: S. Golf, D. Dralle, L. Vecchiet (Eds) “Magnesium 1993” London: John Libbey & Comp., 1993.]
Substance-selective ligands are dissolved in the bulk of a layer. Said layer or membrane often provides a satisfactory selectivity after a process of carefully optimizing the composition of the bulk medium. If such a layer is implemented into existing sensor elements by cast-in, gluing, photo-polymerization, and other polymerization procedures, a considerable loss in selectivity and sensitivity, respectively, has frequently to be accepted.
The process technique for casting layers and immobilizing of selectivity principles by photo-polymerization considerably limits the range of applications of selective layers and is not exploit the full potential of molecular recognition elements.
Despite of the large number of ligands and recognition elements, only few were incorporated into a layer and tested in analytical applications. Therefore, only single ligands were used in chemical sensors. The application of chemical sensors in analytical instruments has a fixed position only in medical applications since many years. Electrolytes are determined by automated instruments for daily routine, but also in “bed-side” analyzers or peripheral analyzers for the physician's lab, by using ion-selective sensors. The first instrument, which makes use of optical sensors, is on the market (OPTI, AVL Biosense Corp., Atlanta). The instrument is equipped with “disposable cartridges” and offers the parameters pO
2
, pCO
2
and pH (based on fluorescence emission technology). In some instruments, a combination of biosensors (voltammetric or amperometric determination of the oxygen partial pressure, e.g. according to Olson, L. et al., Anal. Chim. Acta 224(1) (1989) 31 fe)) for lactate, glucose, peroxide, glutamate, creatinine combined with ion-selective electrodes are implemented. These combinations are based on miniaturized sensors making use of solid-phase transducers or semiconductor elements of type ISFET and ENFET (ion-selective-, enzymatic field effect transistors), where changes in the coulometric properties or the potential, respectively, at the gate are measured. Such a combination was marketed by “i-STAT” as a disposable sensor. These sensors exhibit the disadvantages of sensors as discussed before such as unsatisfying ruggedness and large amounts of waste.
A company selling since many years an amperometric glucose sensor ExacTech™ for self-monitoring, is MediSens Inc. (Waltham, Mass.) having a subsidiary in Basle; a coresponding instrument for industrial applications is the YSI glucose sensor of Yellow Springs (OH, USA). The sensors used in these instruments display several layers, which eventually provide for the selectivity of the biosensors. Each offered biosensor relies on the same electrode principle, which consists of the determination of the oxygen consumption by applying the traditional electrochemical oxygen electrode.
Since 1988, more than 1000 publications related to glucose biosensors have been published (see Gorton, L., Electroanalysis 7/1 (1995) 23-44). In contrast, optical sensors have hardly been introduced. The WPIDS (World Patent Index No) 95-256069 [34] describes the optical determination of straylight in living tissues, and WPIDS 93-213750 [26], the optical measurement of the blood hemoglobin content.
The objective of the present invention was therefore to provide a measuring system, especially for continuous process monitoring, which avoids the drawbacks of known sensor systems and sensors, and which is notably characterized by its high flexibility and ruggedness.
BRIEF SUMMARY OF THE INVENTION
The intended objective has been achieved by providing a continuous, modular, especially multidimensional, and rugged measuring system, which is ideally operated without reagents, as well as by provid
Müller Jörg
Spichiger-Keller Ursula
Eidgenossische Technische Hochschule Zurich
Ladas & Parry
Noguerola Alexander
Tung T.
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