The plates were exposed to ammonia vapour before using fluorescence quenching as a detection method. From the plates it can be seen that phenbarbitone (PB) and barbitone are the barbiturates present in mixture A. See fig 1 (write on plates how you came to conclusion) IR analysis Mixture A and standards of different barbiturates were analysed by the IR spectrophotometer by radiation at wavelengths ranging from 500cm-1 to 4000cm-1.
The IR spectra of Mixture A shows a 95. 53% match with phenobarbitone and otherwise appears not to contain any other barbiturates.This could be because there is much more phenobarbitone than barbitone in the mixture but looking at the TLC plates this does appear to be the case. The spots of barbitone and phenobarbitone are similar in size. Another reason may be that the machine had not been properly cleaned before use. This is unlikely because Mixture A was analysed twice and both spectra produced a similar result.
See fig 2 To be sure the spectrum of a standard could be subtracted and the remainder identified. Raman analysis The Raman effect is analogous to fluorescence except that it is not wavelength dependant and does not require the molecule to have a chromophore.The energy shift in cm-1 due to inelastic scattering of laser radiation is measured rather than wavelength. The shifts measured correspond to the wavenumbers of the bands present in the middle-IR spectrum of the molecule.
Mixture A and standards of phenobarbitone and barbitone were put through the Raman spectrometer. The spectrum produced of Mixture A shows a 77. 43% match with phenobarbitone and a 54. 74% match with barbitone standards on the machine’s library.When the barbitone spectrum was subtracted from the Mixture A spectrum, a 99.28% correlation with phenobarbitone is obtained.
When the phenobarbitone spectra was subtracted from the Mixture A spectrum, a 98. 64% correlation with barbitone was obtained. Therefore the result of the Raman analysis suggests that phenobarbitone and barbitone are the barbiturates present in the mixture. Quantitation methods Gas liquid chromatography (GLC) analysis, high-pressure liquid chromatography (HPLC) and ultra-violet (UV) spectroscopy were used in order to quantify the amount of phenobarbitone and barbitone present in mixture A GLC analysisA gaseous mobile phase flows under pressure through a heated tube either coated with a liquid stationary phase or packed with a liquid stationary phase coated onto a solid support.
The analyte is loaded onto the head of the column via a heated injection port where it evaporates. It then condenses at the head of the column, which is at a lower temperature. The oven temperature is then either held constant or is programmed to rise gradually. Once on the column separation of a mixture occurs according to the relative lengths of time spent by its components in the stationary phase.Monitoring of the column effluent can be carried out with a variety of detectors. An internal standard was used in the investigation to eliminate the errors created by variations of injector volume.
The internal standard should have a similar structure to the unknown, must produce a distant peak and t must not be present in the sample. In the investigation butabarbitone was used. The result shows that HPLC is a precise and accurate technique in the quantitation of drugs in formulation.
UV UV analysis has several applications in pharmaceutical analysis.It is used in the determination of the pka, partition coefficients, solubility and the release of drugs from formulations with time. The UV spectrum of a compound is often used as one of the number of pharmacopoeial identity checks. Strengths 1. An easy to use, cheap and robust method offering good precision for making quantitative measurements of drugs in formulations 2. Routine method for determining some of the physico-chemical properties of drugs which need to be known for the purposes of formulation.
3. Some of the problems of the basic method can be solved by the use of derivative spectra.1. Only moderately selective.
The selectivity of the method depends on the chromophore of the individual drugs, e. g. a coloured drug with an extended chromophore is more distinctive than a drug with a simple benzene chromophore. 2.
Not readily applicable to the analysis of mixtures. Derivative spectroscopy was used because there was a lot of background interference. There was still some interference even at the 4th derivative (D4).
Spectra were repeated several times but with similar results. This led me to believe that the machine was faulty and another machine were used the results may have been different.