M. Delcarlo et al., DISPOSABLE SCREEN-PRINTED ELECTRODES FOR THE IMMUNOCHEMICAL DETECTIONOF POLYCHLORINATED-BIPHENYLS, Analytica chimica acta, 342(2-3), 1997, pp. 189-197
Three different electrochemical approaches for the detection of cr-nap
hthol (amperometry, chronoamperometry and differential pulse voltammet
ry), using screen-printed carbon electrodes, were compared with respec
t to measurable range, detection limit, reproducibility, sample throug
hput and suitability for in field use. The highest sensitivity (252 nA
/mu M) with a calculated detection limit of 0.1 mu M, combined with a
remarkable 'time for sample measurement' (5.5 s) was achieved with dif
ferential pulse voltammetry. The standard error over the whole measure
d range (0.5-100 mu M) was below 5%. The scan speed and the pulse ampl
itude of the differential pulse voltammetric method were optimised usi
ng a simplex method. The optimised electrochemical procedure was then
used to evaluate the detection of low levels of alkaline phosphatase:
this enzyme catalyses the hydrolysis of alpha-naphthol phosphate to al
pha-naphthol. Using 2 min as incubation time for the enzyme reaction,
a linear calibration curve in the range 1-10(-5) U/ml was obtained wit
h a calculated detection limit of 2.1 x 10(-6)U/ml. The standard error
for the 10(-2)U/ml enzyme standard was 6.8%. Finally a competitive en
zyme immunoassay for polychlorinated biphenyls based on alkaline phosp
hatase was performed using the optimised electrochemical detection of
alpha-naphthol. The assay measurable range was 0.01-10 mu g/ml, and th
e detection limit was 0.01 mu g/ml (B-x/B-o%=10).