2-4-dinitrophenylhydrazine and phosphoric-acid

A novel and neutral anion sensor bearing a urea group as binding sites and 2,4-di nitrophenylhydrazine unit as a molecular architecture and a chromophore was synthesized and the visible color changes, the UV-vis and (1)H NMR spectral responses toward anions were assessed.

Topics: Anions; Colorimetry; Kinetics; Magnetic Resonance Spectroscopy; Phenylhydrazines; Phosphoric Acids; Solutions; Spectrophotometry, Ultraviolet

This project has arisen from the need to produce GFFs (glass fiber filters) bearing a thin and evenly distributed coating of a selected reagent in the equatorial plane for breakthrough studies. However, it has been discovered that today's two general techniques for coating GFFs (total immersion and application of reagent solution to GFFs) have usually produced unevenly distributed coatings of reagent in the equatorial plane. In addition, quantities of reagent on GFFs from commercial sources may vary widely in the same lot of coated GFFs. Consequences are variability in capacity of coated filters at the point of breakthrough and, perhaps, wasted reagent. Although today's reagent-coated filters may be satisfactory for routine air sampling, such filters may be unacceptable for precise breakthrough studies. Research has been conducted successfully to produce nearly evenly distributed coatings of reagents in the equatorial plane of GFFs by application of reagent solutions to the centers of GFFs which are resting on crisscrossing, fine, stainless-steel wire. Distributions of coatings have been determined by punching out twenty-one 5-mm circles from each GFF and analyzing each circle by flow-injection with a UV detector. Lowest achievable relative standard deviations of measurement (RSDs) for reagents in 5-mm circles have been 5 to 7%. Reagents studied have included 1-(2-pyridyl)piperazine (1-2PP), 2,4-dinitrophenylhydrazine (DNPH), and 1-(9-anthracenylmethyl)piperazine (MAP). Factors affecting the distribution of such coatings include choice of reagent and choice of solvent for the reagent solution.

Topics: Air; Anthracenes; Environmental Monitoring; Filtration; Glass; Indicators and Reagents; Membranes, Artificial; Phenylhydrazines; Phosphoric Acids; Piperazines; Solutions; Wettability

A new method for the simultaneous determination of aliphatic carboxylic acids and aldehydes in air is described. In this work, carboxylic acids were allowed to react with 2,4-dinitrophenylhydrazine (DNPH) to form the corresponding carboxylic 2,4-dinitrophenylhydrazides. These derivatives have excellent thermal stability, with melting points higher than those of the corresponding hydrazones by 32-50 degrees C. C1-C4 carboxylic acid 2,4-dinitrophenylhydrazides exhibited maximum absorption wavelengths of 331-334 nm and molar absorption coefficients of 1.4 x 10(4) L/mol/cm. They were completely separated by high-performance liquid chromatography (HPLC) with an RP-Amide C16 column. Cartridges packed with DNPH-coated silica particles (DNPH cartridge) were used for sampling formic acid and aldehydes. Formic acid was physically adsorbed on the silica particles as the first step of the sampling mechanism. Gradual reaction with DNPH followed. Formic acid reacted very slowly with DNPH at room temperature (20 degrees C), but reacted completely at 80 degrees C over 4 h. In field measurements, the sample air was drawn through a DNPH cartridge. After sampling, the cartridges were heated at 80 degrees C for 5 h and extracted with acetonitrile for HPLC analysis. Under these optimized conditions, the LOD is 0.4 ug/m(3) for an air sample collected for 24 h at 100 mL/min (144 L).

Topics: Air Pollutants; Aldehydes; Carbon; Carboxylic Acids; Chromatography, High Pressure Liquid; Formates; Molecular Structure; Phenylhydrazines; Phosphoric Acids; Silica Gel; Silicon Dioxide; Spectrum Analysis

This work describes a device that permits the use of a small glass impinger for the automatic sampling and enrichment of air pollutants "on-line" with high-performance liquid chromatographic separation. The impinger is mounted in a modified autoinjector instead of in the vial rack which, using appropriately modified software, permits the automatic sampling of the pollutants by bubbling air through an adequate reaction solution. This solution with the trapped/reacted compounds is then transferred by the autosampler syringe from the impinger to a high-performance liquid chromatography (HPLC) column. After several steps to clean the impinger, using the mobile phase or a specially chosen solvent, the impinger is ready for a new analysis. With a tandem configuration, which allows the first sample to be analysed during the sampling of a second one, a higher analysis frequency is obtained. The technique was tested by determining ng/l concentrations of aldehydes and ketones in an urban environment, sucking air through solutions of 2,4-dinitrophenylhydrazine (DNPH) and phosphoric acid in triethylphosphate. The resulting DNP-hydrazones were injected automatically into a 250 x 4.6 mm I.D. reversed-phase C18 HPLC column (3 microns) and were separated using an isocratic acetonitrile-water (70:30, v/v) mobile phase and then they were detected with a UV monitor at 360 nm. All sampling parameters, such as DNPH and acid concentrations, impinger air flow, sampling time, derivatization speed, blank values, etc., are discussed.

Topics: Air Pollutants; Aldehydes; Chromatography, High Pressure Liquid; Ketones; Online Systems; Osmolar Concentration; Phenylhydrazines; Phosphoric Acids; Specimen Handling; Spectrophotometry, Ultraviolet; Time Factors