Search results

The direct chromatographic resolution of enantiomers using chiral stationary phases (CSPs) is actually a very well established separation technique. Several reasons were responsible for the growing success of this technique. The continuous technical development of new chiral stationary phases (CSPs) combined with their commercial availability has been, probably, the most relevant leverage issue. Chiral liquid chromatography is based on different mutual interactions between the molecules that elute with the liquid (solvent and solutes) and the molecules that are present in the stationary phase. Therefore, optimization of a chiral separation is based on the selection of a proper combination between a CSP and a mobile phase (solvent) composition by promoting, in a favourable way, all possible mutual interactions. The optimization will be a much more challenging task if we are leading not with a traditional binary racemic mixture separation problem but if we are interested in the separation of a quaternary chiral mixture. The complexity degree will be significantly increased if we consider a preparative separation, using a technique such as the simulated moving bed technology, were high feed concentrations are normally used in order to improve the process performance. In these situations, the wanted high concentrations of the different chiral solutes inside the chromatographic columns will enhance significantly the mutual competition between solutes for adsorption with the stationary phase. From a preparative point of view, and when considering the choice of the mobile phase ("solvent") composition, a high selectivity of the enantiomers should not be the only goal to be aimed, as it is frequently the case at analytical scale. Besides the choice of a CSP with high loading capacity, a high solubility of the solutes in the solvent and low retention times should also be taken into account, in order to improve the preparative process performance, as it was extensively explained for the separation of chiral non-steroidal anti-inflammatory drugs1-4 . Nadolol (1-(tert-butyamino)-3-[(5,6,7,8-tetrahydro-cis-6,7-dihydroxy-1-naphthyl)oxy]-2-propanol) is a non-selective beta-adrenergic antagonist pharmaceutical drug. This class of pharmaceutical drugs is prescribed, mainly, to treat arrhythmias, angina pectoris, hypertension, migraine disorders and for tremor. Today, and in spite of the more and more restricted international legislation towards the commercialization of pharmaceutical drugs based on active principles that are made of single enantiomers, nadolol is still only commercially available as an equal mixture of four stereoisomers. This is even more serious due to the considerable evidence, recently made both by the academic community and pharmaceutical industry, that it is important to characterize the single stereochemical components when describing the pharmacodynamics and pharmacokinetics of a racemic drug. The separation of nadolol stereoisomers on CHIRALPAK® AD at both analytical and preparative scales was recently reportedby Ribeiro et al5. However, nowadays no further work was developed to better understand and exploit the capabilities of Chiralpak® IA both for the analytical and preparative chiral separations of nadolol stereoisomers. This work will present a complete methodology concerning experimental, modelling and simulation results. Both the CHIRALPAK® AD and CHIRALPAK® IA CSP will be evaluated. The selection of the proper CSP/solvent combination for preparative operation will be fully study taking into account the screening strategy proposed by Zhang et al6. Additional results include the measurement of nadolol stereoisomers solubilities, equilibrium adsorption data and fixed bed (breakthroughs) experiments. The complete screening of CSP/solvent combination will lead to the choice of the better solutions for the separation of nadolol stereoisomers, considering the target component or components to be obtained. Simulation and experimental results will be presented for the multicomponent separation of nadolol stereoisomers by Simulated Moving Bed adsorption process.

Pharmaceutical drugs have been considered in recent years as one of the groups belonging to emerging contaminants regarding environmental pollution. Their presence in aqueous matrices is mainly related to emissions in their production, direct disposal in environment and human and/or animal excretion. These pollutants can be found in rivers and other aqueous matrices, in very low concentrations, below the ppm level. As, normally, they occur in trace concentrations, their identification and quantification were complex tasks since they require very expensive and not so available analytical methods. Additionally, the actual European Legislation is still scarce for this called "emergent contaminants". Nowadays, there is a strong interest in the development of inexpensive and acute determination methods for these compounds, to overcome the huge lack of information about the potential harmful effects in the living beings and in the environment. In this study, it will be presented the development of a complete analytical methodology and its validation, for the detection and quantification of a set of eight different pharmaceutical drugs. The studied pharmaceutical drugs, azithromycin, sulfamethoxazole, caffeine, paracetamol, acetylsalicylic acid, ketoprofen, diclofenac, and carbamazepine, are representative drugs of several different therapeutic classes: two antibiotics, one central nervous system stimulant, two analgesics, two non-steroidal anti-inflammatories and one anticonvulsant, respectively. Experimental results will include solid phase extraction (SPE) as an extraction/concentration technique followed by detection and quantification using high performance liquid chromatography with diode array detector (HPLC-DAD). The complete separation of all the studied compounds requires the use of two different columns and the optimization of two mobile phase compositions. For compounds with low pKa values a Nucleosil 100-5 C18 column is used with a solvent composed of acetonitrile:water:trifuoracetic acid. For compounds ...

The increasing demand of modern societies for the production and use of chemical compounds coupled with inefficient sewage collection and treatment systems, results in an inadequate release of all types of pollutants in the environment. Emerging pollutants are potentially toxic substances that although typically found in very small concentrations can produce hazard effects on the environment. Due to their very small concentrations they are not yet included in the water quality monitoring programs neither in the environmental control legislation standards. Pharmaceutical and Personal Care Products (PPPs) represents an important group of emerging pollutants due to their continued increase in worldwide consumption and to their inherent capacity to induce physiological effects in very low doses, which raises concerns about the potential adverse effects on humans, animals and environmental systems. In this work, it will be presented the development and validation of an analytical methodology based in solid phase extraction (SPE) and high performance liquid chromatography with diode array detection (HPLC-DAD). The method is validated through its application using real samples of aqueous matrices obtained from different hydric media (swimming pools, rivers and wastewater treatment plants). To extend the scope of the analytical method and thereby a more comprehensive study, the study includes five pharmaceutical drugs that belong to four different pharmacological classes, namely, an analgesic (paracetamol), two antibiotics (azithromycin and sulfamethoxazole), an anticonvulsant (carbamazepine) and a stimulator of the central nervous system (caffeine). These compounds were selected due to their high use and medical prescription levels and consequently leading to a high probability of environmental contamination. ; info:eu-repo/semantics/publishedVersion

The increasing production and use of chemical compounds, coupled with inefficient sewage treatment systems, results in an inadequate release of all types of pollutants into the environment. Emerging pollutants are potentially toxic substances normally found in very small concentrations but that can produce harmful effects on the environment. These compounds are not yet included in water quality monitoring programs nor in environmental control legislation standards. Pharmaceutical and Personal Care Products (PPCPs) are an important group of emerging pollutants due to their continuing increase in world consumption and their inherent capacity to induce physiological effects at very low doses, raising concerns about potential adverse effects in humans, animals and environmental systems. ; info:eu-repo/semantics/publishedVersion

Emerging micropollutants are substances found in the environment in very low concentrations, as micrograms or nanograms per liter, but that can cause harmful effects even in these low quantities. Since this is a recent issue, these pollutants are not legislated yet, but depending on the results of toxicity, bioaccumulation and other studies, they can be regulated in the future. The Pharmaceuticals and Personal Care Products (PPCP's) are a subclass of emerging micropollutants. Although they are very relevant to society, these compounds are eliminated in high quantities by the human body and are not efficiently removed from water in sewage treatment plants. Since they are present in very low concentrations, the analysis and study of PPCP's is a tough task, demanding sophisticated instrumental methods of analysis. Therefore, the aim of this study is to develop a method of analysis to quantify and to monitor the concentration of some PPCP´s, such as, ibuprofen, diclofenac, naproxen, sulfamethoxazole, azithromycin and carbamazepine in aqueous media from Bragança region. These were the pharmaceutical drugs chosen since they are compounds most likely to be found in the aqueous matrices of the area. ; info:eu-repo/semantics/publishedVersion

Emerging micropollutants are substances found in the environment in very low concentrations, as micrograms or nanograms per liter, but that can cause harmful effects even in these low quantities. Since this is a recent issue, these pollutants are not legislated yet, but depending on the results of toxicity, bioaccumulation and other studies, they can be regulated in the future. The Pharmaceuticals and Personal Care Products (PPCP's) are a subclass of emerging micropollutants. ; info:eu-repo/semantics/publishedVersion