The application of Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) in the field of inorganic elemental analysis is very well known in the field of chemical analysis. The advantages of using the above technology are wide elemental coverage, very low detection limit, fast analysis time (all elements at once), wide analytical working range (ppb to wt%), simple spectra of the constituents elements and high matrix tolerance. In spite of its application in inorganic metal and non-metal analysis in ores, alloys and refractories, the technology can also be widely applied to determine the elemental constituents in other specialized commodities. Recently, at the central laboratory of Mitra S.K. Pvt. Ltd., we had an opportunity and experience to develop a method for constituent elements determination in some of pharmaceutical samples supplied by a team of R & D experts of a reputed concern of Kolkata using our very recently procured ICP-OES. The developed method of elemental analysis have been successfully implemented on some liquid drugs e.g., CF as well as on solid drugs such as CZ, CRP etc.
The appropriate sample digestion techniques for the solid samples have been optimized through the Microwave Digestor which provides an excellent sample digestion technique in presence of organic and complex organometallic functional groups present in the drug samples avoiding any contamination and evaporation of any species during sample preparation. Inorganic acids and oxidizing agents under the optimum digestion condition were used in order to get successful digestion of the materials. Figure 1 shows the graphical presentation of the whole digestive process signifying the optimum conditions.
Power in Watt
Fig.1: Schematic representation of the optimum digestive condition during microwave digestion of the samples
Required medicinal constituents such as Ca, Zn, Fe, Mn, Cu, Cr, P etc were determined with high sensitivity and accuracy (measurement of low level trace elements) within an excellent matrix tolerance avoiding interferences of any other elemental constituents. During the analysis the radial and axial mode of the CCD detector were used for the major elements (> 1 wt %) and the trace elements (< 1 wt %) respectively. Fig.2 shows the corresponding emission spectra of the individual analytes at their respective wavelengths during such analysis. These wavelengths were selected in such a way so that any possible interference from other analytes present in the specimen matrix could be overcomed.
Fig.2: Spectral representation of the analytes during the ICP-OES analysis
For some of the samples, the accuracy of the results obtained from the instrument was also verified by the classical elemental analysis performed for a few samples. Table 1 shows some of these instrumental results compared against the classical method for these pharmaceutical samples. The comparison shows excellent compatibility between the results obtained from the instrumental and classical technique. Therefore, the optimized process is expected to perform analysis for large number of such critical pharmaceutical samples in a faster way as compared to the conventional method.
Table 1: Comparison of the results between the instrumental and classical analysis for few pharmaceutical samples
| Samples Analyzed | Elemental Concentration in wt % | |||||||||||
| Cr | Cr | Zn | Fe | P | Mn | Cu | Ca | Pb | ||||
| ICP | Classical | ICP | Classical | ICP | Classical | ICP | Classical | ICP | ICP | ICP | ICP | |
| Sample 1 | 0.017 | – | 2.1 | 1.98 | 9.98 | 9.86 | 10.6 | 10.67 | 0.46 | 0.21 | 15.00 | – |
| Sample 2 | – | – | 0.056 | – | 0.23 | 0.25 | – | 0.49 | – | |||
| Sample 3 | 12.9 | 12.8 | – | – | – | – | – | – | – | – | – | – |
| Sample 4 | – | – | – | – | – | – | 21.37 | 21.33 | ||||
| Sample 5 | – | – | – | – | 0.0028 | – | – | – | – | – | – | 0.00087 |
Innoveted & Developed by: Dr. (Mrs.) Saswati Ghosh Mr. Debasish Pal Mr. Kajal Roy & Mr. Proloy Roy [ MSK – Central Lab ]