Gj. Mohr et al., Effect of the polymer matrix on the response of optical sensors for dissolved aliphatic amines based on the chromoreactand ETHT 4001, ANALYT CHIM, 414(1-2), 2000, pp. 181-187
The absorbance-based chromoreactand 4-(N, N-dioctylamino)-4'-trifluoroacety
lazobenzene (ETHT 4001) has been investigated in different polymer matrices
for the optical sensing of dissolved aliphatic amines. Sensor layers compo
sed of ETHT 4001 and different polymer materials generally show a decrease
in absorbance at around 500 nm and an increase in absorbance at around 420
nm wavelength upon exposure to dissolved aliphatic amines. This change in a
bsorbance is caused by a conversion of the trifluoroacetyl group of the rea
ctand into a hemiaminal or a zwitterion.
Several polymer materials have been screened for their use in optical amine
sensing, such as plasticized poly(vinyl chloride) (PVC), copolymers of acr
ylates, polybutadiene (PBD), and silicone. The choice of the polymer affect
s the sensitivity of the sensor layer, which is generally in the mM range f
or 1-butylamine, and the response time, which lies in the range of 10-30 mi
n. Furthermore, the polarity of the polymer matrix has a strong influence o
n the diol formation caused by conditioning in water, and on the absorbance
maximum of the solvatochromic reactand. However, the selectivity of the se
nsor layers for primary, secondary and tertiary amines is nearly unaffected
by the polymer matrix. Thus, while it is possible to vary sensitivity towa
rds amines and humidity by choosing the appropriate polymer matrix, it is n
ot possible to modify the sensor's selectivity within different amines. (C)
2000 Elsevier Science B.V. All rights reserved.