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Solution inlet

Reference inlet

Waste

(a)

Counter electrode

Glucose

Lactate

pCO 2

pH

K+

Ca++

Na+

Reference electrode

pO 2

Haematocrit

Sensor channel

Counter electrode

(b)

Enzyme layer

(Glucose or lactate oxidase)

Interference

rejection layer

Sample path

Sensor well

Enzyme electrode

Diffusion controlling

layer

Pt wire

Silver wire

Sensor card

Silver print

3-electrode

potentiostat

Card reference electrode

Fig. 16.2Micro sensor analyte detectors. (a) The GEM 3000 Sensor Card; (b) the Amperometric Glucose/Lactate

Analyte Sensors. (Reproduced by permission of IL Critical Care, Lexington, USA.)

635 16.2 Clinical measurements and quality control