Wine Chemistry and Biochemistry

(Steven Felgate) #1

12 Automatic Analysers in Oenology 657


12.3.2 Composition of a Sequential Analyser


12.3.2.1 The Sample Tray


This contains a variable number of vials into which the samples to be analysed are


placed.


12.3.2.2 The Reaction Tray


This is composed of transparent cuvettes into which are placed the sample and the


reagent(s). The cuvettes are housed in a thermostatted bath to ensure constant tem-


perature for the various colour reactions. The cuvettes may be single use or may be


washed in a cleaning ramp before being re-used.


12.3.2.3 The Reagent Tray


This tray contains reservoirs of the reagents to carry out the desired analyses.


They are placed in refrigerated wells which enables the use of fragile, temperature-


sensitive reagents in the case of enzymatic methods.


12.3.2.4 The Sampling Arm(s)


These robotic arms equipped with an automatic syringe system are used to take


pre-programmed aliquots from the sample and reagent tray and place them into the


reaction cuvettes.


12.3.2.5 The Optical Sector


This component carries out colorimetric measurements of the different reaction


cuvettes, either at specific moments (at the start and end of the reaction, for example)


or in a continuous fashion in order to establish a reaction curve for each reaction


cuvette.


12.3.2.6 The Electronic-Computing Module


This component drives and controls the system and carries out the calculations


required to transform the signal into a numerical result.


12.3.3 Analytical Scheme


A wide variety of analytical schemes maybe used and the example described below


corresponds to the most classical cases. It consists of the following steps.

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