Predicting HCl concentrations in fire enclosures using an HCl decay model coupled to a CFD-based fire field model

The amount of atmospheric hydrogen chloride (HCl) within fire enclosures produced from the combustion of chloride-based materials tends to decay as the fire effluent is transported through the enclosure due to mixing with fresh air and absorption by solids. This paper describes an HCl decay model, typically used in zone models, which has been modified and applied to a computational fluid dynamics (CFD)-based fire field model. While the modified model still makes use of some empirical formulations to represent the deposition mechanisms, these have been reduced from the original three to two through the use of the CFD framework. Furthermore, the effect of HCl flow to the wall surfaces on the time to reach equilibrium between HCl in the boundary layer and on wall surfaces is addressed by the modified model. Simulation results using the modified HCl decay model are compared with data from three experiments. The model is found to be able to reproduce the experimental trends and the predicted HCl levels are in good agreement with measured values

Development and release mechanism of diltiazem HCl prolonged release matrix tablets

A coated matrix tablet formulation has been used to develop controlled release diltiazem HCl (DIL) tablets. The developed drug delivery system provided prolonged drug release rates over a defined period of time. DIL tablets prepared using dry mixing and direct compression and the core consisted of hydrophilic and hydrophobic polymers such as hydroxypropylmethylcellulose (HPMC), Eudragits RLPO/RSPO, microcrystalline cellulose, and lactose. Tablets were coated with Eudragit NE 30D, and the influence of varying the inert hydrophobic polymers and the amount of the coating polymer were investigated. The release profile of the developed formulation was described by the Higuchi model. Stability trials up to 6 months displayed excellent reproducibility.

HPLC-ESI-MS method development for the elucidation of nicardipine degradation products

Purpose: Nicardipine is a member of a family of calcium channel blockers named dihydropiridines that are known to be photolabile and may cause phototoxicity. It is therefore vital to develop analytical method which can study the photodegradation of nicardipine. Method: Forced acid degradation of nicardipine was conducted by heating 12 ml of 1 mg/ml nicardipine with 3 ml of 2.5 M HCl for two hours. A gradient HPLC medthod was developed using Agilent Technologies 1200 series quaternary system. Separation was achieved with a Hichrome (250 x 4.6 mm) 5 μm C18 reversed phase column and mobile phase composition of 70% A(100%v/v water) and 30% B(99%v/v acetonitrile + 1%v/v formic acid) at time zero, composition of A and B was then charged to 60%v/v A;40%v/v B at 10minutes, 50%v/v A; 50%v/v B at 30minutes and 70%v/v A; 30%v/v B at 35minutes. 20μl of 0.8mg/ml of nicardipine degradation was injected at room temperature (25oC). The gradient method was transferred onto a HPLC-ESI-MS system (HP 1050 series - AQUAMAX mass detector) and analysis conducted with an acid degradation concentration of 0.25mg/ml and 20μl injection volume. ESI spectra were acquired in positive ionisation mode with MRM 0-600 m/z. Results: Eleven nicardipine degradation products were detected in the HPLC analysis and the resolution (RS) between the respective degradants where 1.0, 1.2, 6.0, 0.4, 1.7, 3.7, 1.8, 1.0, and 1.7 respectively. Nine degradation products were identified in the ESI spectra with the respective m/z ratio; 171.0, 166.1, 441.2, 423.2, 455.2, 455.2, 331.1, 273.1, and 290.1. The possible molecular formulae for each degradants were ambiguously determined. Conclusion: A sensitive and specific method was developed for the analysis of nicardipine degradants. Method enables detection and quantification of nicardipine degradation products that can be used for the study of the kinetics of nicardipine degradation processes.