On-line determination of carboxylic acids, aldehydes and ketones by high-performance liquid chromatography-diode array detection-atmospheric pressure chemical ionisation mass spectrometry after derivatization with 2-nitrophenylhydrazine.
2-Nitrophenylhydrazine (2-NPH) is widely used for the derivatization of carboxylic acids, aldehydes and ketones, in industrial and biological samples. These compounds react with 2-NPH to form derivatives, which are separated by high-performance liquid chromatography (HPLC) and detected with diode array detection (DAD). The UV spectra give information about the functionality of the compounds: carboxylic acid or ketone/aldehyde. Most of the eluting compounds in "known" samples are well characterised by the retention time (comparison with those of standards) of the 2-NPH derivative and their UV spectrum. The identification of different unknown 2-NPH derivatives of carboxylic acids, ketones and/or aldehydes, in industrial or biological samples, based on retention time and/or UV spectrum is not sufficient. These unknown 2-NPH compounds can be identified with on-line atmospheric pressure chemical ionisation mass spectrometry (APCI-MS) based on the molecular mass or/and the fragmentation of the derivative. A novel and specific on-line HPLC-DAD-APCI(-)-MS method is described for the determination of carboxylic acids, ketones and aldehydes, after on-line pre-column derivatization with 2-NHP. The fragmentation of different 2-NPH derivatives were investigated and the possibilities of APCI(-)-MS detection were demonstrated by the on-line identification of an unknown derivative, which turned out to be a side product between 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and 2-NPH in the presence of high concentrations of a cyclic amide in the sample solution.
Peters
R
R
DSM Research, Competence Center Molecular Identification & Quantification, P.O. Box 18, MD 6160, Geleen, The Netherlands. ron.peters@dsm.com
Hellenbrand
J
J
Mengerink
Y
Y
Van der Wal
Sj
S
D000447:Aldehydes / Q000032:analysis* / Q000302:isolation & purification; D002264:Carboxylic Acids / Q000032:analysis* / Q000302:isolation & purification; D002851:Chromatography, High Pressure Liquid; D003626:Data Display; D006834:Hydrazines / Q000737:chemistry*; D007202:Indicators and Reagents; D007659:Ketones / Q000032:analysis* / Q000302:isolation & purification; D013058:Mass Spectrometry; D009862:Online Systems; D010659:Phenylhydrazines; D012997:Solvents; D013056:Spectrophotometry, Ultraviolet
D000447:Aldehydes; D002264:Carboxylic Acids; D006834:Hydrazines; D007202:Indicators and Reagents; D007659:Ketones; D010659:Phenylhydrazines; D012997:Solvents; C060574:2-nitrophenylhydrazine