Development And Validation Of Chromatographic Methods For Simultaneous Quantification Of Drugs In Bulk And In Their Formulations: HPLC And HPTLC Techniques

Extract:

Chapter 1, INTRODUCTION:

Introduction to analytical chemistry (1-4):

Analytical chemistry may be defined as the 'science and art of determining the composition of materials in terms of the elements or compounds contained". Large number of drug/s introduced in the pharmaceutical market is increasing per year. These drugs may be either new entities or partial structural modification/s of the existing one. Very often there is a time delay from the date of introduction of a drug in the market to the date of its inclusion in pharmacopoeias. This is because of the possible uncertainties in the continuous and wider usage of these drug/s, reports of new toxicities (resulting in their withdrawal from the market), development and introduction of better drug/s by competitor/s. Under these conditions, standard/s and analytical procedure/s for these drugs may not be available in the pharmacopoeia/s. It therefore becomes necessary to develop newer analytical methods for such drugs.
Quality control is a concept, which strives to produce a perfect product by series of measures designed to prevent and eliminate errors at different stages of production. With the growth of pharmaceutical industry during last many years, there has been fast development in the field of pharmaceutical analysis involving complex instrumentation. Providing simple, rapid analytical method for complex formulation is a matter of importance.
Important reasons for the improvement of newer drug analysis methods are:

The drug or combinations of drug may not be official in any pharmacopoeias.
An appropriate analytical method for the drug may not be available in the literature due to patent regulations.
Suitable analytical procedure may not be available for the drug in the form of a formulation due to the interference caused by the formulation excipients.
Analytical method/s for the evaluation of the drug in biological fluids may not be available.
Analytical method for a drug in combination with other drugs may not be available.
The existing analytical procedures may require expensive solvents and reagents. It may also involve burdensome extraction, separation procedures and these may not be reliable.
ANALYTICAL METHODS:

Highly specific and sensitive analytical techniques hold the key in the designing, development, standardization and quality control of medicinal products. They are equally important in drug metabolism and pharmacokinetics studies, both of which are fundamental to the evaluation of bioavailability and duration of clinical response.
Modern physical methods of analysis are very sensitive, precise and providing thorough information from minute samples of material. They are for the most part quickly applied and in general are readily amenable to automation. For these reasons they are now widely used in product development, control of manufacture, quality control, as a check on stability during storage and monitoring the use of drugs and medicines.
CLASSIFICATION OF ANALYTICAL METHODS:

1) Chemical Methods:

a) Titrimetric Methods; They involve:

i. acid base reactions, ii. precipitations, iii. redox reactions iv. complexomeric reactions, v. large cation reagents.
b) Gravimetric Methods are:

i. weighing the active ingredients after separation, ii. weighing of the residue after ignition of the sample, iii. precipitation and weighing of the derivatives of the active ingredients.
2) Instrumental methods:

a) Spectroscopic techniques; There are:

i. ultraviolet and visible spectrophotometry, ii. fluorescence and phosphorescence spectrophotometry, iii. atomic spectrometry (emission and absorption), iv. infrared spectrophotometry, v. raman spectroscopy, vi. X-ray spectroscopy, vii. radiochemical techniques including activation analysis, viii. nuclear magnetic resonance spectroscopy, ix. electron spin resonance spectroscopy.
b) Electrochemical techniques cover:

i. potentiometry (pH and ion selective electrodes), ii. conductance techniques, iii. voltammetric techniques, iv. stripping techniques, v. coulometry, vi. Electrogravimetry.
c) Chromatographic techniques;