2.2. Reagents and solutions
All reagents were of analytical grade and all
solutions were prepared with water from a Millipore
(Bedford, MA) Milli-Q system (Model UV
Plus Ultra-Low Organics Water). Catecholamines
from Aldrich (Milwaukee, WI) 2.0/102 mol l1
stock solutions were prepared daily in 0.1 mol l1
phosphate buffer solution at pH 6.0. Reference
solutions from 6.1/106 to 1.0/104 mol l1
epinephrine, from 6.6/106 to 3.9/104
mol l1 dopamine, from 6.7/106 to 7.0/
105 mol l1 L-dopa and from 6.2/106 to
8.1/105 mol l1 isoprenaline were analyzed in
a 0.1 mol l1 phosphate buffer solution at the
same pH. In the construction of the biosensors an
Acheson 38 graphite powder from Fisher and
mineral oil from Sigma were used throughout.
890 O.D. Leit