Nitrogen and sulphur management: challenges for organic sources in temperate agricultural systems

A current global trend towards intensification or specialization of agricultural enterprises has been accompanied by increasing public awareness of associated environmental consequences. Air and water pollution from losses of nutrients, such as nitrogen (N) and sulphur (S), are a major concern. Governments have initiated extensive regulatory frameworks, including various land use policies, in an attempt to control or reduce the losses. This paper presents an overview of critical input and loss processes affecting N and S for temperate climates, and provides some background to the discussion in subsequent papers evaluating specific farming systems. Management effects on potential gaseous and leaching losses, the lack of synchrony between supply of nutrients and plant demand, and options for optimizing the efficiency of N and S use are reviewed. Integration of inorganic and organic fertilizer inputs and the equitable re-distribution of nutrients from manure are discussed. The paper concludes by highlighting a need for innovative research that is also targeted to practical approaches for reducing N and S losses, and improving the overall synchrony between supply and demand

Capillary electrochromatography of basic compounds using octadecyl-silica stationary phases with an amine-containing mobile phase

The capillary electrochromatographic (CEC) analysis of basic compounds on octadecyl-silica stationary phases (Hypersil ODS and Spherisorb ODS I) was studied. A basic drug (fluvoxamine) and one of its possible impurities were used as test compounds. With an eluent of acetonitrile-phosphate buffer (pH 7.0), the compounds could be baseline-separated; however, broad and tailing peaks were obtained. To minimise detrimental interactions with residual silanol groups, the pH of the mobile phase was lowered to 2.5, but the plate numbers were still quite low

Profiling of cocaine by micellar electrokinetic chromatography

The potential of micellar electrokinetic chromatography (MEKC) for the profiling of cocaine samples is described. An MEKC system containing sodium dodecyl sulfate (SDS) and methanol was optimized using a test mixture of cocaine, its common impurities (benzoylecgonine, norcocaine, tropacocaine, and trans-cinnamoylcocaine), and several degradation products. The effect of pH, percentage modifier, and concentration surfactant on the separation has been investigated. The optimal separation buffer for cocaine samples consisted of 75 mM SDS, 17.5% methanol, and 25 mM berate (pH 8.3) and was well suited to separate components of diverse polarity in one run. Various cocaine seizures have been analyzed with the MEKC system and their signatures were compared. The electrokinetic chromatograms obtained were characteristic, and differences and similarities among the samples could easily be observed. Several impurities were identified in the samples by means of migration times and comparison of recorded and library UV spectra. The composition of the samples was determined semiquantitatively using relative corrected peak areas