Electroanalytical determination of codeine in pharmaceutical preparations

A square wave voltammetric (SWV) method and a flow injection analysis systemwi th electrochemical detection (FIA-EC) using a glassy carbon electrode were evaluated for the determination of codeine in pharmaceutical preparations. The interference of several compounds, such as acetaminophen,guaiacol, parabens, ephedrine, acetylsalicylic acid and caffeine, that usually appear associated with codeine pharmaceutical preparations was studied. It was verified that these electroanalytical methods could not be used with acetaminophen present in the formulations and that with guaiacol, parabens or ephedrine present the use of the FIA-EC system was impracticable. A detection limit of 5 µmol L- 1 and a linear calibration range from 40 to 140 µmol L- 1 was obtained with the SWV method. For the flow injection analysis procedure a linear calibration range was obtained from 7 to 50 µmol L- 1 with a detection limit of 3 µmol L- 1 and the FIA-EC systemallowed a sampling rate of 115 samples per hour. The results obtained by the two methods, SWV and FIA-EC, were compared with those obtained using reference methods and demonstrated good agreement, with relative deviations lower than 4%.

Electrochemical determination of dihydrocodeine in pharmaceuticals

Two analytical methods for the quality control of dihydrocodeine in commercial pharmaceutical formulations have been developed and compared with reference methods: a square wave voltammetric (SWV) method and a flow injection analysis system with electrochemical detection (FIA-EC). The electrochemical methods proposed were successfully applied to the determination of dihydrocodeine in pharmaceutical tablets and in oral solutions. These methods do not require any pretreatment of the samples, the formulation only being dissolved in a suitable electrolyte. Validation of the methods showed it to be precise, accurate and linear over the concentration range of analysis. The automatic procedure based on a flow injection analysis manifold allows a sampling rate of 115 determinations per hour.

Chromatographic techniques for the determination of free phenol in foundry resins

Phenol is a toxic compound present in a wide variety of foundry resins. Its quantification is important for the characterization of the resins as well as for the evaluation of free contaminants present in foundry wastes. Two chromatographic methods, liquid chromatography with ultraviolet detection (LC-UV) and gas chromatography with flame ionization detection (GC-FID), for the analysis of free phenol in several foundry resins, after a simple extraction procedure (30 min), were developed. Both chromatographic methods were suitable for the determination of phenol in the studied furanic and phenolic resins, showing good selectivity, accuracy (recovery 99–100%; relative deviations <5%), and precision (coefficients of variation <6%). The used ASTM reference method was only found to be useful in the analysis of phenolic resins, while the LC and GC methods were applicable for all the studied resins. The developed methods reduce the time of analysis from 3.5 hours to about 30 min and can readily be used in routine quality control laboratories.