The characterization of new benzimidazole fungicides /

Extensive studies have been initiated to generate enough data to register the methyl homologue (MBC-MIC, see List of Abbreviations, page 14) of benomyl (MBC-BIC) as a commercial product through a joint effort between the federal government and Canadian industry. The objective of this study, as part of the whole project, was to generate fundamental data on the physical properties of the series of benomyl homologues (MBC-MIC, MBC-EIC, MBC-PIC and MBC-BIC). These data include the half lives of these compounds in water at the pH range from 2 to 12; they ranged from 0.7 to 10. 1 hours. Standard solutions of these compounds in concentrated acid were found to be stable for at least two weeks, and in the case of MBC-MIC it was stable at least 1 month. Another major goal of this study was to determine the solubility of each compound in water at different pHs in the range of 1 to 12. The solubility of the compounds ranged from 0.6 jig/mL to 396 fig/mL. In addition, it was possible to prepare stable stock solutions at concentrations > 1 000 |ig/mL in concentrated nitric acid. Several aspects of analytical methods have been improved to accurately assess the solubility and rate of degradation of benomyl and its homologues in alkaline conditions. The determination of melting points was attempted but all compounds decomposed before melting.To complement the studies of the benomyl homologue series attempts were made to explore the presence of any relationships between the structures of the compounds and their properties. Although there were some exceptions, the compound's solubility decreased and half life increased as the molecular size increased from the methyl to the butyl analogue.

Development and characterization of concentric capillary nebulizer used in inductively coupled plasma analysis /

A simple, low-cost concentric capillary nebulizer (CCN) was developed and evaluated for ICP spectrometry. The CCN could be operated at sample uptake rates of 0.050-1.00 ml min'^ and under oscillating and non-oscillating conditions. Aerosol characteristics for the CCN were studied using a laser Fraunhofter diffraction analyzer. Solvent transport efficiencies and transport rates, detection limits, and short- and long-term stabilities were evaluated for the CCN with a modified cyclonic spray chamber at different sample uptake rates. The Mg II (280.2nm)/l\/lg 1(285.2nm) ratio was used for matrix effect studies. Results were compared to those with conventional nebulizers, a cross-flow nebulizer with a Scott-type spray chamber, a GemCone nebulizer with a cyclonic spray chamber, and a Meinhard TR-30-K3 concentric nebulizer with a cyclonic spray chamber. Transport efficiencies of up to 57% were obtained for the CCN. For the elements tested, short- and long-term precisions and detection limits obtained with the CCN at 0.050-0.500 ml min'^ are similar to, or better than, those obtained on the same instrument using the conventional nebulizers (at 1.0 ml min'^). The depressive and enhancement effects of easily ionizable element Na, sulfuric acid, and dodecylamine surfactant on analyte signals with the CCN are similar to, or better than, those obtained with the conventional nebulizers. However, capillary clog was observed when the sample solution with high dissolved solids was nebulized for more than 40 min. The effects of data acquisition and data processing on detection limits were studied using inductively coupled plasma-atomic emission spectrometry. The study examined the effects of different detection limit approaches, the effects of data integration modes, the effects of regression modes, the effects of the standard concentration range and the number of standards, the effects of sample uptake rate, and the effect of Integration time. All the experiments followed the same protocols. Three detection limit approaches were examined, lUPAC method, the residual standard deviation (RSD), and the signal-to-background ratio and relative standard deviation of the background (SBR-RSDB). The study demonstrated that the different approaches, the integration modes, the regression methods, and the sample uptake rates can have an effect on detection limits. The study also showed that the different approaches give different detection limits and some methods (for example, RSD) are susceptible to the quality of calibration curves. Multicomponents spectral fitting (MSF) gave the best results among these three integration modes, peak height, peak area, and MSF. Weighted least squares method showed the ability to obtain better quality calibration curves. Although an effect of the number of standards on detection limits was not observed, multiple standards are recommended because they provide more reliable calibration curves. An increase of sample uptake rate and integration time could improve detection limits. However, an improvement with increased integration time on detection limits was not observed because the auto integration mode was used.