Low-Cost Fluorescence Sensor for Ammonia Measurement in Livestock Houses.

Measurements of ammonia with inexpensive and reliable sensors are necessary to obtain information about e.g., ammonia emissions. The concentration information is needed for mitigation technologies and documentation of existing technologies in agriculture. A flow-based fluorescence sensor to measure ammonia gas was developed. The automated sensor is robust, flexible and made from inexpensive components. Ammonia is transferred to water in a miniaturized scrubber with high transfer efficiency (>99%) and reacts with o-phthalaldehyde and sulfite (pH 11) to form a fluorescent adduct, which is detected with a photodiode. Laboratory calibrations with standard gas show good linearity over a dynamic range from 0.03 to 14 ppm, and the detection limit of the analyzer based on three-times the standard deviation of blank noise was approximately 10 ppb. The sampling frequency is 0.1 to 10 s, which can easily be changed through serial commands along with UV LED current and filter length. Parallel measurements with a cavity ring-down spectroscopy analyzer in a pig house show good agreement (R2 = 0.99). The fluorescence sensor has the potential to provide ammonia gas measurements in an agricultural environment with high time resolution and linearity over a broad range of concentrations.

Generic, highly selective and robust capillary electrophoresis method for separation of a racemic mixture of glitazone compounds.

A generic, highly selective, and robust capillary electrophoresis (CE) method was developed for separation of a racemic mixture of three available glitazone compounds (also known as thiazolidinediones) in active pharmaceutical ingredients (API) and tablets. The method separated the R and S enantiomers of balaglitazone, pioglitazone and rosiglitazone, and showed that the samples contained an equal (50:50) quantity of the enantiomers as a mixture. After a simple extraction of samples with acetonitrile:water (80:20), separation was performed using a combination of two cyclodextrins: sulfobuthylether-beta-cyclodextrin (SB-beta-CD) and dimethyl-beta-cyclodextrin (DM-beta-CD) in the electrolyte at pH 8.0. The method showed a very good specificity, and all separations were achieved with a resolution (Rs) over 3.0. The developed CE method was then validated. The Rs for the separations were 3.5 for balaglitazone enantiomers, 3.5 for pioglitazone enantiomers, and 3.7 for rosiglitazone. The squared correlation coefficients (r2) were found to be 0.999 for all three compounds. The range of the CE method (injection volume was approximately 4 nl) was demonstrated to be from 1.0 to 2.4 ng. The R.S.D. in the repeatability study was found to be less than 0.5 for area/area ratio (and 3.0% for area) for all three compounds. The R.S.D. in the intermediate precision study was found to be less than 0.7 for area/area ratio (and 4.5% for area) for all three compounds. Generally, the method showed good robustness. Resolution between the enantiomers peak was maintained acceptable throughout the small variations around the pH value of the buffer, different capillary, CE instrument and electrolytes ion strength capacity, but changes in concentration of cyclodextrins and acetonitrile showed significant effects on separations and affected the resolution. The validation results showed that the CE method was suitable for separation of the racemic mixtures of the three glitazone drugs. The CE method was then applied for routine test during the drug and formulation development work of balaglitazone. Due to the achieved results from this work, it is the authors' belief that this method can easily separate other glitazone racemic mixtures.

Dry deposition of reactive nitrogen to marine environments: recent advances and remaining uncertainties.

Many highly productive marine ecosystems exhibit nitrogen limitation or co-limitation. This article is a status review of research into the exchange of nitrogen between the atmosphere and these ecosystems with a particular focus on reactive nitrogen compounds. A summary of research conducted over the past ten years is presented and a perspective given as to remaining uncertainities and research needs. Looking toward development of coastal management modeling tools, we illustrate the processes that need to be resolved in order to accurately simulate the flux from the atmosphere and provide guidance on the required resolution of such models.