Manual de Soluções Analíticas

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18 Solutions Manual for Analytical Chemistry 2.1
.
( )
k C
k C K C
C
C K C
1 44
GA GA
GA GA GA,AA AA
GA
GA GA,AA AA# #
=
+
=
+
.
) )( (K
1 44
1 10
1 10 1 10
M
M M
4
4 5
GA,AA
#
## #
=
+
-
- -
 Solving for KGA,AA gives its value as 4.4.
 (b) he method is more selective for the interferent, ascorbic acid, 
than it is for the analyte, glycolic acid, because KGA,AA is greater than 
one.
 (c) To avoid an error of more than 1%, we require that
.K C C0 01
5
3
GA
GA,AA AA# # #
#= =
-
-
8. (a) To determine the sensitivity for the analyte, we begin with the 
equation Ssamp = kACA and solve for kA; thus
.
. .k C
S
1 12 10
7 45 10 66 5
M
A A/MA
A
samp
6
5
#
#
= = =-
-
 (b) In the presence of an interferent, the signal is
( )S k C K C,samp A A A I I#= +
 Rearranging to solve for KA,I and making appropriate substitutions
( . / ) ( . )
. ( . / ) ( . )
K
k C
S k C
A M M
A A M M
66 5 6 5 10
4 04 10 66 5 1 12 10
,A I
A I
samp A A
5
5 6
# #
# # #
=
-
=
-
-
- -
 gives –7.9×10–3 as the value for KA,I.
 (c) he method is more selective for the analyte, hypoxanthine, than 
for the interferent, ascorbic acid, because the absolute value of KA,I is 
less than one.
 (d) To avoid an error of 1.0% requires that .K C C0 01–