2.4- Dinitrophenylhydrazones acid-sensitive

Cleavage of tosylhydrazones. A mixture of phenylacetone tosylhydrazone and Am-berlyst 15 in 10 1 acetone/water stirred at room temp, for 24 h phenylacetone. Y 91%. The method is applicable to aldehydes (especially in the presence of 10 eqs. of paraformaldehyde) as well as ketones it is simple and cheap furthermore, acid-sensitive groups such as furyl derivs., esters or ethers are not affected. F.e. incl. cleavage of oximes, 2,4-dinitrophenylhydrazones and semicarbazones, s. R. Ballini, M. Petrini, J. Chem. Soc. Perkin Trans. I 1988, 2563-5. 

The dinitrophenylhydrazones of the fission products of sugars are detectable with sodium hydroxide.160 Also, a wide variety of sugars and their acetates, and uronic acid lactones may be detected with sodium hydroxide followed by heating,161 Sensitivity is poor, however. After paper electrophoresis, chondroitinsulfate may be distinguished from proteins by means of Toluidine Blue.162... 

Colorometric procedures involving reaction of aldehydes with hydrazines, semicarbazide, or piperidine/nitroprusside solutions are also non-specific and lack sensitivity (15, 35, 36). Schmidt et al. (33) have proposed an HPLC method for analyzing the 2,4-dinitrophenylhydrazone (DNPH) derivatives of specific aldehydes. This procedure allows for a number of ddehydes to be separated and measured simultaneously, however, HPLC methods in general suffer from poor resolving power and may have low sensitivity (37). In addition, hydrazine derivatizations are often performed under acidic conditions for maximal reactivity these conditions would not provide quantitative information on total aldehyde content. 

Detection systems for GC are chosen for their sensitivity and selectivity for a particular class of VOCs. Detectors for GC include FID, the BCD, the photoionization detector (PID), the pulsed discharge detector (PDD), and the reduction gas detector (RGD). A variety of mass spectrometers can also be interfaced with a GC for confirmation of molecular structure and quantitation. Singlewavelength ultraviolet-visible detectors (190 to 600 nm) and diode array detectors are used to detect carbonyls as their 2,4-dinitrophenylhydrazone derivatives. The absorption maxima for aliphatic carbonyls, aromatic carbonyls, and dicarbonyls are near 360 nm, 385 to 390 nm, and 415 to 430 nm, respectively. Formic, acetic, and pyruvic acid are detected by ion conductivity. 

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