The application of monolithic columns in pesticides analysis.
ABSTRACT HPLC and HPLC/MS are the most widely used analytical techniques in the field of pesticides analysis. In recent years, there has been considerable focus on fast separations in HPLC in order to reduce analysis time as well as cost. Monolithic columns, consisting of continuous beds with macropores and mesopores, can meet this requirement and have been widely used in the medical and biological fields. However, it has seldom been used when analyzing pesticides. In this work, the application of monolithic columns in pesticides analysis and their advantages are evaluated and compared with those obtained using conventional packed columns.
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ABSTRACT: This article describes the development of an enhanced liquid chromatography-mass spectrometry (LC-MS) method for the analysis of pesticides in olive oil. One hundred pesticides belonging to different classes and that are currently used in agriculture have been included in this method. The LC-MS method was developed using a hybrid quadrupole/linear ion trap (QqQ(LIT)) analyzer. Key features of this technique are the rapid scan acquisition times, high specificity and high sensitivity it enables when the multiple reaction monitoring (MRM) mode or the linear ion-trap operational mode is employed. The application of 5 ms dwell times using a linearly accelerating (LINAC) high-pressure collision cell enabled the analysis of a high number of pesticides, with enough data points acquired for optimal peak definition in MRM operation mode and for satisfactory quantitative determinations to be made. The method quantifies over a linear dynamic range of LOQs (0.03-10 microg kg(-1)) up to 500 microg kg(-1). Matrix effects were evaluated by comparing the slopes of matrix-matched and solvent-based calibration curves. Weak suppression or enhancement of signals was observed (<15% for most-80-of the pesticides). A study to assess the identification criteria based on the MRM ratio was carried out by comparing the variations observed in standard vs matrix (in terms of coefficient of variation, CV%) and within the linear range of concentrations studied. The CV was lower than 15% when the response observed in solvent was compared to that in olive oil. The limit of detection was < or =10 microg kg(-1) for five of the selected pesticides, < or =5 microg kg(-1) for 14, and < or =1 microg kg(-1) for 81 pesticides. For pesticides where additional structural information was necessary for confirmatory purposes-in particular at low concentrations, since the second transition could not be detected-survey scans for enhanced product ion (EPI) and MS3 were developed.Analytical and Bioanalytical Chemistry 11/2007; 389(6):1815-31. · 3.66 Impact Factor
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ABSTRACT: The computerization of method development and validation are useful in analysis of pharmaceuticals in pharmaceutical industry. In this article a simple and rapid high performance liquid chromatographic method has been developed for the determination of oxcarbazipine in pharmaceutical formulations. Factorial design was applied for optimization of essential factors for robustness study. A linear model was postulated and a 2 3 full factorial design was employed to estimate the model coefficients. More specifically, experimental design helps the researcher to verify if changes in factor values produce a statistically significant variation of the observed response. The strategy is most effective if statistical design is used in most or all stages for screening and optimizing process in future method validation for method development and validation.01/2008;
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ABSTRACT: For almost 10years, silica-based monolithic stationary phases have been used in numerous fields of analytical chemistry, especially when high flow rate is required or for the separation of high molecular weight compounds such as peptides. In comparison with particulate stationary phases, the macroporous structure of the silica rod induces low pressure drops, which allows the use of high flow rates, leading to a dramatic reduction of the analysis duration. We suggest another use of this type of phases with mobile phases having a high viscosity, such as ethanol–water mixtures. These mobile phases are environmentally friendly, avoiding the use of toxic solvents such as methanol and acetonitrile, and consequently the necessary cleaning of waste is reduced. In this paper, the eluting strength of different hydro-organic mobile phases and their efficiencies are compared on Chromolith RP-18e. Due to higher eluting strength, the use of ethanol–water mixtures also allows decreasing the amount of organic solvent required to achieve a separation, whereas, despite a higher viscosity, the chromatographic efficiencies are as good as those obtained with classical mobile phases. Finally, separation of pesticides (triazines) and sunscreen molecules are presented.Chromatographia 11/2008; 68(11):985-990. · 1.44 Impact Factor