**1. Introduction**

The majority of the methods currently available used in pharmaceutical analysis are high-performance liquid chromatography (HPLC), ultra-performance liquid chromatography (UPLC), high-performance thin layer chromatography (HPTLC), gas chromatography (GC), gas chromatography/mass spectrometry (GC/MS), liquid chromatography/mass spectrometry (LC/MS), capillary electrophoresis (CE), voltammetry, HPLC/NMR, etc., all require highly sophisticated instruments which are very expensive, involve tedious multiple extraction steps and are time-consuming. Therefore, there is a constant need for developing analytical methods, such as titrimetry and spectrophotometry that are simple, sensitive, rapid, accurate, precise, and inexpensive and that can be easily adapted by the pharmaceutical industry. In recent years, the assay methods in the monographs including titrimetric and spectrometric analytical methods can be seen in the literature for pharmaceutical analysis.

Titrimetric methods have maintained their great value as an analytical tool despite the steadily growing resort to purely physical methods which often necessitate very sophisticated and expensive instrumentation.

The titrimetric techniques are still widely used in the analysis for the assay of bulk drug materials and their share in the European Pharmacopeia (EP) is almost 70%. Also, in the United States Pharmacopeia (USP) more than 40% of low molecular weight organic compounds are determined by aqueous or non-aqueous titration [1]. In fact, titrimetric methods are still as widely used as ever in pharmaceutical analysis, especially since the development of physicochemical assays of measurement, as well as spreading of non-aqueous titration method and potentiometric end point detection, expanding and improving the field of application of titrimetric methods, especially in the pharmaceutical analysis. The European and United States Pharmacopeias are adopting many analytical methods to ensure the quality of the drug, such as titration, spectrometry, chromatography, and others. These methods and their respective proportions are included in **Table 1** according to the edition of European (The European Pharmacopeia and Council of Europe, 2002) and US (United States Pharmacopeia, 2004) pharmacopeias [2, 3]. It is noted from the table that spectroscopic and titration methods are still widely used in the pharmaceutical analysis. To name a few, in the literature survey, titrimetric methods have been used for the determination of terbinafine [4–8], ethionamide [9–13], and Amoxicillin [14–20] in pharmaceutical formulations. In addition to many drug formulations that were estimated using titration methods.

Further, among the various instrumental methods available for trace analysis, UV–visible spectrophotometry continues to be one of the most popular, because of its simplicity and cost-effectiveness. UV–visible spectrophotometry is one of the most widespread techniques were used in analytical chemistry for drug analysis, capable of producing accurate and precise results. For these reasons, procedures using this technique are found in analytical, pharmaceutical, and research laboratories. Specially, in the field of pharmaceutical analysis, spectrophotometric offers the best detection sensitivity, accuracy, and reproducibility of drug analysis in the bath of drug research, development, and laboratories quality control testing of marketed drug products.

In the United States Pharmacopeia (USP), UV–visible spectrophotometric methods still provide the majority of the spectrophotometric procedures, there are still over 200 specific monographs containing UV–visible spectrophotometric measurements in the current version of (USP36-NF31). As well as, the number of UV– visible spectrophotometric assays used in the pharmaceutical analysis is increasing more than other spectrophotometric techniques, such as IR and fluorescence.

If we follow the international refereed journals that are concerned with publishing scientific research in the field of drug analysis, we will find that the majority of


#### **Table 1.**

*Proportion of titrimetric/spectrophotometric methods used for the assay of bulk drug according to European and Unites States pharmacopeias [00,000].*

#### *Spectrophotometric/Titrimetric Drug Analysis DOI: http://dx.doi.org/10.5772/intechopen.109364*

published research has used the spectrophotometric technique in analysis, directly or indirectly. To name a few, in the estimation of some anti-infective agents in pharmaceuticals, we will find that most of the published research about it used spectroscopic methods [21–30]. We also find that browsing through the majority of pharmaceutical analysis books finds that all of them give more space in that books to talk about spectrophotometric techniques and their various applications, especially in the field of drug analysis.

The above proves beyond any doubt that titrimetric and spectrophotometric methods are considered to present and future as the most important methods used in the analysis of pharmaceutical formulations with their accuracy in measurements.
