Liquid sampling in batch analysers

The aspiration systems used by batch analysers, normally moving articulated probes, withdraw the samples from the sampler vials and dispense them to the analyser cups or cuvettes. Time Is not such a decisive factor here, so that high-precision syringes are the commonest option for measuring and transferring the liquid samples. 

The sampling of water for the determination of traces of organic pollutants requires a preconcentration step. The use of sorptive pre-columns Is a representative example of the Inability to separate sample collection and treatment, which are carried out In a single step. This analytical methodology Is described In greater detail in Chapter 11, dealing with the automation of chromatographic processes. 

The aspirated and dispensed volumes can be independently programmed (from 10 to 150 pL, from 60 to 900 mL, from 0.2 to 2 mL, etc.). By means of the manually transported aspiration/withdrawal tip, the unknown solution is aspirated by pressing a knob. Then, the volume taken and that of the reagent are poured into the reaction cuvette. Obviously, the sample pump must operate in a reversible fashion. 

8 Automatic system for sampling of variable volumes of liquid by computerized control of weights, reported by Malmstadt et al. (Reproduced from [5] with permission on the American Chemical Society). 

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