Acta Pharm. 57
(2007) 87-98
Original research paper
Rapid titrimetric and spectrophotometric
methods for salbutamol sulphate
in pharmaceuticals using N-bromosuccinimide
KANAKAPURA BASAVAIAH1,*
BANKAVADI CHIKKASWAMY SOMASHEKAR1
and VEERAIAH RAMAKRISHNA2
basavaiahk@yahoo.co.in
1Department of Chemistry, University of Mysore, Manasagangotri,
Mysore-570 006, India
2Department of Pharmaceutical Chemistry, Government
College of Pharmacy, Bangalore-27, India
One titrimetric
and two spectrophotometric methods which are simple,
sensitive and rapid are described for the assay of salbutamol
sulphate (SBS) in bulk drug and in tablet dosage
forms using N-bromosuccinimide
(NBS) and two dyes, rhodamine-B and methylene blue, as reagents. In titrimetry,
aqueous solution of salbutamol sulphate
is treated with a measured excess of NBS in acetic acid medium and after the
oxidation of SBS is complete, the unreacted oxidant
is determined iodometrically. Spectrophotometric
methods entail addition of a known excess of NBS in acid medium followed by the
determination of residual oxidant by reacting with a fixed amount of either rhodamine B and measuring the absorbance at 555 nm (method
A) or methylene blue and measuring the absorbance at
665 nm (method B). In all methods, the amount of NBS reacting corresponds to
the amount of SBS content. Titrimetric method is
applicable over 1.74 × 10-4 – 8.68 × 10-4 mol L-1
range and the reaction stoichiometry is found to be
1:6 (SBS:NBS). In spectrophotometric methods, the
absorbance is found to increase linearly with the concentration of SBS, which
is corroborated by the correlation of coefficients of 0.9993 and 0.9988 for
method A and method B, respectively. The systems obey Beer’s law for 0.25-1.75
mg
mL-1 (method A) and 0.5-5.0 mg mL-1 (method B). The
calculated apparent molar absorptivity values were
found to be 2.10 × 105 and 6.16 × 104 L mol-1
cm-1, for method A and method B, respectively. The limits of
detection and quantification are also reported for both spectrophotometric
methods. Intra-day and inter-day precision and accuracy for the developed
methods were evaluated. The methods were successfully applied to the assay of
SBS in tablet and capsule formulations and the results were statistically compared
with those of a reference method. No interference was observed from common
tablet adjuvants. The accuracy and reliability of the
methods were further ascertained by recovery experiments via the standard-addition technique.
Keywords: salbutamol
sulphate, assay, titrimetry,
spectrophotometry, N-bromosuccinimide