1.Determination of nitrite in waters by microplate fluorescence spectroscopy and HPLC with fluorescence detection.
Büldt A1, Karst U. Anal Chem. 1999 Aug 1;71(15):3003-7.
A selective and versatile fluorescence spectroscopic method for the determination of nitrite in waters has been developed. Nitrite reacts in the presence of mineral acids with the nonfluorescent N-methyl-4-hydrazino-7-nitrobenzofurazan forming N-methyl-4-amino-7-nitrobenzofurazan, which can be detected by fluorescence spectroscopy with an excitation maximum at lambda = 468 nm and an emission maximum at lambda = 537 nm in acetonitrile. Three new methods based on this reaction have been developed: Direct fluorescence spectroscopy, HPLC/fluorescence, or HPLC with UV/vis detector may be selected as detection techniques. On microplates, high-throughput fluorescence spectroscopy is achieved, while HPLC/fluorescence provides lower limits of detection, and HPLC with UV/vis detection enables evaluation of the reaction with standard instrumentation. Different water samples were investigated using all detection modes, and a photometric standard procedure was successfully employed to validate the new methods with an independent technique.
2.N-Methyl-4-hydrazino-7-nitrobenzofurazan as a New Reagent for Air Monitoring of Aldehydes and Ketones.
Büldt A1, Karst U. Anal Chem. 1999 May 1;71(9):1893-8. doi: 10.1021/ac980946f.
The synthesis of N-methyl-4-hydrazino-7-nitrobenzofurazan (MNBDH) and its application as a new reagent for the determination of aldehydes and ketones are described. MNBDH reacts with carbonyl compounds in acidic media to the corresponding MNBD-hydrazones. In contrast to the established reagent 2,4-dinitrophenylhydrazine (DNPH), MNBDH is oxidized by both ozone and nitrogen dioxide quantitatively to only one product, N-methyl-4-amino-7-nitrobenzofurazan (MNBDA). This can easily be separated from the hydrazones of lower aldehydes by means of HPLC. Due to larger molar absorptivities and absorption maxima at wavelengths over 470 nm, selectivity is higher and limits of detection are lower for the new reagent compared to DNPH. MNBDH reacts slightly faster than DNPH with carbonyl compounds and significantly faster than other N-alkylated hydrazine reagents.
3.Characterization of chemical interferences in the determination of unsaturated aldehydes using aromatic hydrazine reagents and liquid chromatography.
Schulte-Ladbeck R1, Lindahl R, Levin JO, Karst U. J Environ Monit. 2001 Jun;3(3):306-10.
A systematic investigation on interferences in the determination of unsaturated aldehydes and ketones using the 2,4-dinitrophenylhydrazine (DNPH) method is described. Acrolein, crotonaldehyde, methacrolein and 1-buten-3-one are derivatized with DNPH in the presence of an acidic catalyst to form the respective hydrazones. The unstable hydrazones react with excess reagent to form adducts. These are identified by high-performance liquid chromatography (HPLC)-mass spectrometry and spectroscopic techniques after cryogenic fraction collection of the adducts. The quantification of the unsaturated carbonyls with the DNPH method remains difficult. N-Methyl-4-hydrazino-7-nitrobenzofurazan (MNBDH) was used as an alternative reagent for this purpose. As with DNPH, the formation of a side product is observed. In contrast to DNPH, the alteration of the pH immediately after sampling leads to only one reaction product, which is stable and storable in solution at 4 degrees C for 2 days.
4.Determination of the dialdehyde glyoxal in workroom air-development of personal sampling methodology.
Olsen R1, Thorud S, Hersson M, Ovrebø S, Lundanes E, Greibrokk T, Ellingsen DG, Thomassen Y, Molander P. J Environ Monit. 2007 Jul;9(7):687-94. Epub 2007 Apr 4.
The dialdehyde glyoxal (ethanedial) is an increasingly used industrial chemical with potential occupational health risks. This study describes the development of a personal sampling methodology for the determination of glyoxal in workroom air. Among the compounds evaluated as derivatizing agents; N-methyl-4-hydrazino-7-nitrobenzofurazan (MNBDH), 1,2-phenylenediamine (OPDA), 1-dimethylaminonaphthalene-5-sulfonylhydrazine (dansylhydrazine, DNSH) and 2,4-dinitrophenylhydrazine (DNPH), DNPH was the only reagent that was suitable. Several different samplers were evaluated for sampling efficiency of glyoxal in workroom air using DNPH as derivatizing agent; in-house DNPH coated silica particles packed in two different types of glass tubes, impingers containing acidified DNPH solution, filter cassettes containing glass fibre filters coated with DNPH, a commercially available solid phase cartridge sampler originally developed for formaldehyde sampling (Waters Sep-Pak DNPH-silica cartridge), and the commercially available SKC UMEx 100 passive sampler originally developed for formaldehyde sampling.