Influence of different types of commercially available microcrystalline cellulose on degradation of perindopril erbumine and enalapril maleate in binary mixtures.

Influence of some commercially available types of microcrystalline cellulose (MCC) on the stability of certain active pharmaceutical ingredients (APIs), when in contact, has been investigated. Two structurally similar APIs, perindopril erbumine (PER) and enalapril maleate (EM), both well-known angiotensin-converting enzyme inhibitors were used. The main properties of an MCC that could determine the stability for each API were measured and correlated to the stability of these two APIs in binary mixtures. The stability of these APIs differed when in contact with different types of MCC. The dominant properties of MCC from one manufacturer were surface features that influenced the stability of PER and acidity that influenced the stability of EM. In the case of MCC from other manufacturers, unbound water was stability determining for both substances.

Determination of bisphosphonates by ion chromatography-inductively coupled plasma mass spectrometry.

An ion chromatography-inductively coupled plasma mass spectrometry (IC-ICP-MS) was introduced in the analysis of bisphosphonates. Two compounds (alendronic acid and etidronic acid) were separated on a Dionex AS-7 anion-exchange column with dilute nitric acid employed as the mobile phase. The analytes were detected at m/z 31, as they contain phosphorus. The detection limits achieved were 0.20 mg l(-1) for alendronic acid and 0.05 mg l(-1) for etidronic acid. Since the determination of phosphorus by ICP-MS is difficult due to polyatomic interferences at m/z 31 (15N16O+, 14N16O1H+, and 12C1H(3)16O+), a detailed study of the influence of plasma parameters on phosphorus and background signal was performed.