Introduction

The regents are mainly used for quantitative and qualitative analyses. There are number of reagents which are mainly used for the determination of pharmaceuticals. The most commonly employed reagents for the determinations are the following:

• 3-Methyl-benzathiazolinone hydrazone which is commonly known as MBTH. The colour production is bowed upon the oxidative coupling of this reagent with phenols, amines, carbonyl compounds, etc.
• Triketohydrindine hydrate commonly known as ninhydrin reagent. The basic principle involved in this is oxidative deamination of amino acids followed by reduction of ninhydrin to hydrindantin.
• Paradimethyl amino benzaldhyde (PDAB) (or) cinnamaldhyde (PDAC) condenses with amines in acidic media to product utilisable products to give a colour.
• 2,4,6-Tripyridyl-S-tiazine (TPTZ) is best example for chromogenic agent for the determination of iron. The basic principle is oxidation.
• 1,2-Naphthoquinone-4-sulfonate sodium (NQS) is a chromogenic agent used for the determination of 1° aromatic amines.
• N-1-Naphthyl ethylene diaminedihydrochloride called as Bratton–Marshall reagent (BM reagent) undergoes diazotisation for the determination of sulpha drugs, local anaesthetics, etc.
• Phosphomolybdotungstic acid called as Folin–Ciocalteu reagent (FC reagent) undergoes oxidation, reduction (or) hydrolysis based on the functional group to be determined such as phenols, amines, etc.
• 2,6-Dichloroquinone chloroimide which is commonly known as GIBB'S reagent used for the identification and estimation of phenols.

All above listed regents are most wildly employed in the determination of several pharmaceutical compounds. These reagents have greater applications in the pharmaceutical field and also applicable to recent analytical techniques.