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Advisor(s)
Abstract(s)
The present work reports new sensors for the direct determination of Microcystin-LR (MC-LR) in
environmental waters. Both selective membrane and solid contact were optimized to ensure suitable
analytical features in potentiometric transduction. The sensing layer consisted of Imprinted Sol–Gel
(ISG) materials capable of establishing surface interactions with MC-LR. Non-Imprinted Sol–Gel
(NISG) membranes were used as negative control. The effects of an ionic lipophilic additive, time of
sol–gel polymerization, time of extraction of MC-LR from the sensitive layer, and pH were also
studied. The solid contact was made of carbon, aluminium, titanium, copper or nickel/chromium alloys
(80 : 20 or 90 : 10). The best ISG sensor had a carbon solid contact and displayed average slopes of
211.3 mV per decade, with detection limits of 7.3 1010 M, corresponding to 0.75 mg L1
. It showed
linear responses in the range of 7.7 1010 to 1.9 109 M of MC-LR (corresponding to 0.77–2.00 mg
L1
), thus including the limiting value for MC-LR in waters (1.0 mg L1
). The potentiometric-selectivity
coefficients were assessed by the matched potential method for ionic species regularly found in waters
up to their limiting levels. Chloride (Cl) showed limited interference while aluminium (Al3+),
ammonium (NH4
+
), magnesium (Mg2+), manganese (Mn2+), sodium (Na+
), and sulfate (SO4
2) were
unable to cause the required potential change. Spiked solutions were tested with the proposed sensor.
The relative errors and standard deviation obtained confirmed the accuracy and precision of the
method. It also offered the advantages of low cost, portability, easy operation and suitability for
adaptation to flow methods.