Background:
Spectrophotometry and thin layer chromatography have been commonly applied
in pharmaceutical analysis for many years due to low cost, simplicity and short time of execution.
Moreover, the latest modifications including automation of those methods have made them very effective
and easy to perform, therefore, the new UV- and derivative spectrophotometry as well as high performance
thin layer chromatography UV-densitometric (HPTLC) methods for the routine estimation of
amrinone and milrinone in pharmaceutical formulation have been developed and compared in this work
since European Pharmacopoeia 9.0 has yet incorporated in an analytical monograph a method for quantification
of those compounds.
Methods:
For the first method the best conditions for quantification were achieved by measuring the
lengths between two extrema (peak-to-peak amplitudes) 252 and 277 nm in UV spectra of standard
solutions of amrinone and a signal at 288 nm of the first derivative spectra of standard solutions of milrinone.
The linearity between D252-277 signal and concentration of amironone and 1D288 signal of milrinone
in the same range of 5.0-25.0 μg ml/ml in DMSO:methanol (1:3 v/v) solutions presents the square
correlation coefficient (r2) of 0,9997 and 0.9991, respectively. The second method was founded on
HPTLC on silica plates, 1,4-dioxane:hexane (100:1.5) as a mobile phase and densitometric scanning at
252 nm for amrinone and at 271 nm for milrinone.
Results:
The assays were linear over the concentration range of 0,25-5.0 μg per spot (r2=0,9959) and
0,25-10.0 μg per spot (r2=0,9970) for amrinone and milrinone, respectively. The mean recoveries percentage
were 99.81 and 100,34 for amrinone as well as 99,58 and 99.46 for milrinone, obtained with
spectrophotometry and HPTLC, respectively.
Conclusion:
The comparison between two elaborated methods leads to the conclusion that UV and
derivative spectrophotometry is more precise and gives better recovery, and that is why it should be
applied for routine estimation of amrinone and milrinone in bulk drug, pharmaceutical forms and for
therapeutic monitoring of the drug.