2.7. Optimisation of detection conditions for the
hand-held detector
The FLUO SENS SD confocal fluorescence detector includes
a software controlled setup for detector sensitivity as well as
a correction for background signal and blank sample. Detector
sensitivity was adjusted initially with a 4MU standard curve
with the scope to achieve linearity over a range of 103
magnitudes and reproducible signal to background ratios for
the lowest concentrations. 4MU concentrations used for this
step were from 10 nM to 20 mM. The settings where then
further adjusted with the MUG-GUD assay and finally with E.
coli spiked water samples. Once the sensitivity setup had been
optimised it was stored in the software file and remained
unchanged for the analyses of river water samples. Sterile
Ringer’s solution was used as a blank to zero the instrument.