Spectrophotometric determination of carbamazepine ... - MA Zayed

carbamazepine. The data obtained are shown in Figure (3). The results indicate that a 1:1 [Mo(V)-
thiocyanate]: [drug] ion–pair is formed through the electrostatic attraction between positive protonated
drug CBZ + and thiocyanate negative complex as shown in scheme (3).
N
(Mo (SCN) 6
) -
O NH 3
Carbamazepine -Mo (V)
Scheme (3). Proposed structure of Mo(V)-carbmazepine ion pair.
Validity of Beer's law:
Under the optimum conditions described above, the calibration graph can be constructed for
the investigated drug. Table (1) shows the analytical parameters obtained for the determination of
carbamazepine using Mo(V)-thiocyanate reagent. The absorbance-concentration curve is found to be
rectilinear and Beer's law is obeyed in the concentration range 10-350 µg ml -1 . The mean recovery
values obtained amount in the range 100-100.3%. The correlation coefficient of the data obtained is
0.9998. The Sandell sensitivity (S) is found to be 2.22 µg cm -2 . The limit of detection (LOD) and
quantification (LOQ) are found to be 3.36 and 11.21 µg mL -1 , respectively. The SD is found to be
0.04–0.09 and the RSD are 0.63–2.17%. The low values of the relative standard deviation indicate the
high accuracy and precision of the method. This is supported also by the calculated values of Sandell
sensitivity which indicates the high sensitivity of the method.
3.2. Determination of mosapride citrate (MOC) using BTB and BCG reagents
Mosapride citrate drug is present in positively charged protonated form and dyestuff reagents
present mainly in anionic form at pH ≥ 3. So by adding 0.7 and 1 mL of pH 4.0 and 3.0 of universal
buffer using BTB and BCG reagents, respectively, the ion-pairs which are extracted with 10 mL of
chloroform (5 mL x 2) and 10 mL of methylene chloride (10 mL x 1) using BTB and BCG,
respectively, are formed. The spectra of the ion-pair reaction products show characteristic λ max at 412
and 416 nm for mosapride citrate using BTB and BCG reagents, respectively (Figure (4)). The
optimum reaction conditions for determination of the ion-pair complexes were established. The effect
of varying the concentration of 1 mg mL -1 BTB or 0.02% w/v BCG on the intensity of the coloured
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