A novel method for classification of wine based on organic acids.

Bio-electronic tongue was linked to artificial intelligence processing unit and used for classification of wines based on carboxylic acids levels, which were indirectly related to malolactic fermentation. The system employed amperometric biosensors with lactate oxidase, sarcosine oxidase, and fumarase/sarcosine oxidase in the three sensing channels. The results were processed using two statistical methods - principal component analysis (PCA) and self-organized maps (SOM) in order to classify 31 wine samples from the South Moravia region in the Czech Republic. Reference assays were carried out using the capillary electrophoresis (CE). The PCA patterns for both CE and biosensor data provided good correspondence in the clusters of samples. The SOM treatment provided a better resolution of the generated patterns of samples compared to PCA, the SOM derived clusters corresponded with the PCA classification only partially. The biosensor/SOM combination offers a novel procedure of wine classification.

Various instrumental approaches for determination of organic acids in wines.

Biosensors based on lactate oxidase, sarcosine oxidase and mixture of fumarase and sarcosine oxidase were used for monitoring of organic acids in wine samples. Additionally, tartaric acid was determined by modified colorimetric method based on formation of the vanadate-tartrate complex. The above mentioned methods were used for the analysis of 31 wine samples and obtained data were compared with the results from capillary electrophoresis as a basic standard method. This comparison showed a certain degree of correlation between biosensors and capillary electrophoresis. The provided information pointed to the potential uses of biosensors in the field of winemaking.

Development of a bifunctional sensor using haptenized acetylcholinesterase and application for the detection of cocaine and organophosphates.

We developed a dual piezoelectric/amperometric sensor for the detection of two unrelated analytes in one experiment that uses propidium to anchor acetylcholinesterases (AChE) at the surface. This mass-sensitive sensor does not only allow the examination of the interaction between AChE and the modified surface but also the detection of in situ inhibition of the surface-bound AChE. Here we describe the application of the propidium-based sensor in combination with a modified AChE. For this reason the cocaine derivative benzoylecgonine (BZE) was coupled via a 10A long hydrophilic linker - 1,8-diamino-3,4-dioxaoctane - to carboxylic groups of the AChE after EDC/NHS activation. Thus the modified AChE (BZE-AChE) possesses an additional recognition element besides the inhibitor binding site. After the deposition of BZE-AChE on the sensor surface the binding of an anti-BZE-antibody to the BZE-AChE can be monitored. This makes it possible to determine two analytes - cocaine and organophosphate - in one experiment by measuring antibody binding and decrease in enzymatic activity, respectively. Furthermore it was also shown that other cocaine-binding enzymes, e.g., butyrylcholinesterase, can bind to the modified BZE-AChE. The competitive immunoassay allowed the detection of cocaine with a dynamic range from 10(-9) to 10(-7)M. The organophosphate chlorpyrifos-oxon could be detected in concentrations from 10(-6) down to 10(-8)M after 20 min of injection time (equals to 500 microL sample volume.

Analysis of cholinesterase binding to a carnitine-modified EQCM sensor.

A sensor for cholinesterases (ChEs) has been developed by binding carnitine via 1,6-diaminohexane to a mixed monolayer of 11-mercaptoundecanoic acid/11-mercapto-1-undecanol on the surface of a gold-coated quartz crystal. Catalytically active and organophosphate-inhibited acetyl- and butyryl-cholinesterases of different origins were tested for their binding ability to D- and L-carnitine, respectively. The binding constants were calculated by using a one-to-one binding model. Additionally, the activity of the immobilized ChE was monitored and the operational stability was investigated amperometrically.

Development of direct ELISA for the determination of 4-nonylphenol and octylphenol.

Development of direct competitive enzyme-linked immunoadsorbent assays (ELISAs) based on polyclonal and monoclonal antibodies raised against 4-n-alkylphenol hapten mimics is described. A strong tendency to recognize 4-nonylphenol (NP) and 4-octylphenol (OP) as a total analyte amount was indicated by cross-reactivity pattern established for two polyclonal antibodies. These antibodies were employed for development of class-selective assays exhibiting IC(50) values around 40 microg.L(-1) for technical 4-NP. Specificity of the monoclonal antibody 4H6 and additional two polyclonal antibodies allowed sensitive detection of linear long-chain forms of 4-n-alkylphenols (4-n-AP). The assays incorporating these antibodies offer a potential for detecting the minor fraction of NP/OP isomer spectrum having IC(50) = 11.5 microg.L(-1) for 4-n-NP. No cross-reactivity interference was indicated for linear alkylbenzene sulfonates and phenolic compounds. To interpret the measured data in terms of analytical equivalents, a reliable relationship between the assay responses and AP content of contaminated samples should be verified and validated.