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Potato production requires intensive nitrogen (N) fertilization. To maintain yield and profitability, potato farmers must satisfy the need of the crops for N by applying fertilizer during the growing season. Petiole nitrate analysis and whole leaf total N test have been studied before to guide in-season N application, and both have strengths and weaknesses. Whole vine total N test has been discussed by the US potato industry as another diagnostic tool to understand the overall N uptake of the plant, but little data are available. A 2-year field study was conducted at the University of Wisconsin Hancock Agricultural Research Station in 2018 and 2019 with the objective to compare three diagnostic tools, petiole nitrate analysis, whole leaf total N test and whole vine total N test, for identifying the nutrient status of two chipping potato cultivars subjected to five different N rates. It was found that petiole nitrate analysis is still the most responsive method to reflect supplemental N application during the growing season and is the most relevant to final tuber yield. Whole leaf total N test is less responsive, but it can reflect plant N uptake up to the date of testing. Comparatively, whole vine total N test is not acceptable because of the excessive amount of time needed to collect and process the samples, and the concern over whether or not the sample tested in the last step of analysis is representative. Future diagnostic tools using cutting-edge remote sensing and machine learning technologies that can detect spatial variability should be developed to further enhance the effectiveness of in-season N monitoring, which is critical for sustainable potato production.

A review of the literature has identified 10 agents causing contact dermatitis among topically administered drugs for glaucoma. These agents include beta-blockers (timolol, befunolol, betaxolol, levobunolol, carteolol, metipranolol), a carbonic anhydrase inhibitor (dorzolamide), a parasympathomimetic (pilocarpine), and sympathomimetics (dipivefrin, apraclonidine). Patch testing has been documented in certain individuals as well as cross sensitization and reactivity. Systemic reactions to these topically applied medications have been briefly noted.

A modification of the spectrofluorimetric method of Lowe et al 1 for the measurement of glutamic acid decarboxylase (GAD) activity in rat brain is described. This method involves the indirect determination of GAD activity by measurement of the formation of gamma-amino-butyric acid (GABA). The minimum activity of GAD observable was 0.45 μg GABA/hour/mg protein and the limit of detection was 0.20 × 10−6 M GABA. This method was developed for measurement of GAD activity of gabaergic terminals in globus pallidus, endopeduncular nucleus, substantia nigra, and ventromedial thalamus in rat brain.

A quantitative high pressure liquid chromato-graphic (HPLC) assay has been developed for the determination of glutamic acid decarboxylase (GAD) activity in subregions of rat brain. GAD activity was determined indirectly by measurement of gamma-aminobutyric acid (GABA). Fluorimetric detection was made possible by derivatization with ortho-phthalaldehyde and the limit of detection was 11 ng GABA.

A quantitative high pressure liquid chromatographic (HPLC) assay has been developed for the determination of isoniazid (INH) and acetylisoniazid (ACINH) in human plasma. Plasma samples were taken from a patient after oral administration of INH (with proven tuberculosis infection). A C18 reversed phase radial compression column was used to separate INH and ACINH from other plasma components. The analysis takes 10 minutes per sample and the lower limit of detection for each compound is 0.10 ug/ml plasma.

An analytical method has been developed for the determination of N-acetylcysteine in human serum following acetaminophen overdosage in humans. Serum samples were treated with dithiothreitol and the protein-freed product was derivatized with 2,4-dinitrofluorobenzene. N-Acetylhomocysteine thiolactone was used as an internal standard. Following diethyl ether extraction, the components were separated on a reversed-phase column with retention times of 7.4 and 9.9 min for N-acetylcysteine and internal standard, respectively. Ultraviolet detection at 365 nm was employed and little interference was noted from other serum components. The method has been applied to quantitation of N-acetylcysteine given as treatment for acetaminophen intoxication.

An experimental determination of heats of atomization of some ortho -substituted benzoic acids has been performed by combustion and differential scanning calorimetry. Resonance energy was calculated by the difference between the heat of atomization in the gas phase and the sum of the bond energies of a fixed bond structure for a resonating molecule. As the van der Waals radii of the ortho -substituent increased a decrease in resonance energy was observed.

A quantitative gas chromatographic--mass spectrometric method has been developed for the determination of glutamic acid decarboxylase (GAD) activity in subregions of rat brain. The five subregions analyzed, weighing approximately 2.51 mg each, were globus pallidus, entopeduncular nucleus, ventromedial thalamus, and substantia nigra medical and lateral. The activity of the GAD enzyme has been determined indirectly by measurement of gamma-aminobutyric acid (GABA) using gamma-[2,2-2H2] aminobutyric acid as the internal standard. Both compounds were quantitatively converted to trimethylsilyl-GABA and trimethylsilyl-[2H2]GABA in 90 min with hexamethylchlorosilane, trimethylchlorosilane, pyridine and N,O-bis(trimethylsilyl)trifluoroacetamide silylating agents. Using selective ion monitoring and electron impact ionization at 70 eV, the limit of detection was 15 ng GABA per mg tissue. This method is compared with a fluorimetric procedure.

Two procedures using liquid chromatography with electrochemical detection are described for the determination of dopamine (DA) and its two acidic metabolites, homovanillic acid (HVA) and 3,4-dihydroxyphenylacetic acid (DOPAC), in subregions of rat striatum and nucleus accumbens. A strong cation-exchange column was used for DA analysis and a C18 reversed-phase column was used for the analysis of the metabolites. Effects of pH, temperature and percentage of methanol on the retention time of HVA and DOPAC were studied. Levels of these compounds in the subregions of rat stratum and nucleus accumbens are reported.

A comparison of liquid chromatography with electrochemical detection (LCEC) and gas chromatography mass spectrometry (GCMS) has been made for analysis of homovanillic acid (HVA) in rat brain tissue. The LCEC procedure gave slightly higher average values of HVA in the samples measured; however, the HVA content determined by both methods related significantly. Rat brain meostriatum was used as representative samples for comparison of the two analytical procedures.

A quantitative gas chromatographic—mass spectrometric assay has been developed for the determination of ethambutol (EMB) in human plasma. Plasma samples were taken from a patient after oral administration of EMB (with proven tuberculosis infection). Deuterated EMB and a non-deuterated analogue of EMB were synthesized and used as internal standards in this procedure; both gave excellent agreement in the analysis. The derivatizing agent used was trifluoroacetic anhydride (TFAA) and quantitative derivatization was complete in one hour, forming EMB-(TFA). Selective ion monitoring was utilized to monitor the gas chromatographic effluent. Ions were generated by electron impact at 70 eV. The limit of detection was 36 ng EMB per ml plasma. This method is compared with the electron-capture gas chromatographic procedure of Lee and Benet.

A quantitative gas chromatographic-mass spectrometric assay was developed for the determination of dopamine in subregions of rat brain. Five tissue punches weighing approximately 1.7 mg each were taken from the nucleus accumbens and four neostriatal regions differing in anterior-posterior level. The dopamine extracted from the tissue was treated with pentafluoropropionic anhydride (PFP) and quantitatively formed dopamine-(PFP)3. The derivatizing procedure took 15 min and the retention time for dopamine-(PFP)3 and its deuterated analogue [1,1,2,2-2H4]dopamine-(PFP)3) was 120 sec. Selective ion monitoring was utilized to monitor the gas chromatographic effluent. Ions were generated by electron impact ionization. The assay was able to measure concentrations of 1 nanogram dopamine per milligram protein. An anterior-posterior gradient of dopamine was observed in the striatum. This assay should be useful in studies examining the effects of experimental manipulations on dopamine content in relatively small areas of brain tissue.

A simple zone melting apparatus has been constructed for purification of low melting [

Mesure par calorimetrie differentielle a balayage avec rapidite et bonne precision de ΔH de fusion, sublimation et vaporisation de C 6 H 5 CO 2 H et composes o-substitues

Numerous chromatographic and non-chromatographic methods of analysis for anti-tuberculosis drugs and metabolites in biological tissues have been discussed in this review. Depending upon the analytical methodology selected, limits of detection range from microgram to picogram levels. A number of examples have been given of the correlation between different types of assay procedures. The metabolism and pharmacokinetics have been described along with some of the commonly associated problems of sample collection and storage.

A number of non-chromatographic and chromatographic methods for analysis of GAD avtivity in biological tissues have been described. The majority of these chromatographic methods utilize the analysis of GABA formed from incubation homogenates. Depending upon the analytical technique selected, limit of detection range from nanogram to pictogram levels of GABA. Also discussed have been some of the commonly associated problems and their resolution with sample collection, postmortem changes and alternative pathways of Co 2 and GABA production which can lead to errors in accurate determination of GAD activity in biological samples.

Determination experimentale des energies de resonance et des chaleurs d'atomisation en combinant combustion et calorimetrie differentielle a balayage