Determination of Aldehydes and Ketones in Fuel Ethanol by High-Performance Liquid Chromatography with Electrochemical Detection

A new methodology was developed for analysis of aldehydes and ketones in fuel ethanol by high-performance liquid chromatography (HPLC) coupled to electrochemical detection. The electrochemical oxidation of 5-hydroxymethylfurfural, 2-furfuraldehyde, butyraldehyde, acetone and methyl ethyl ketone derivatized with 2,4-dinitrophenylhydrazine (DNPH) at glassy carbon electrode present a well defined wave at +0.94 V; +0.99 V; +1.29 V; +1.15 V and +1.18 V, respectively which are the basis for its determination on electrochemical detector. The carbonyl compounds derivatized were separated by a reverse-phase column under isocratic conditions with a mobile phase containing a binary mixture of methanol / LiClO_4(aq) at a concentration of 1.0 × 10⁻³ mol L⁻¹ (80:20 v/v) and a flow-rate of 1.1mL min⁻¹ . The optimum potential for the electrochemical detection of aldehydes-DNPH and ketones-DNPH was +1.0 V vs. Ag/AgCl. The analytical curve of aldehydes-DNPH and ketones-DNPH presented linearity over the range 5.0 to 400.0 ng mL⁻¹, with detection limits of 1.7 to 2.0 ng mL⁻¹ and quantification limits from 5.0 to 6.2 ng mL⁻¹, using injection volume of 20 μL. The proposed methodology was simple, low time-consuming (15 min/analysis) and presented analytical recovery higher than 95%.     

A New Application of Hexamethylenetetramine‐Bromine Supported onto Wet Alumina as an Efficient Reagent for Cleavage of Phenylhydrazones under Classical Heating and Microwave Irradiation

2,4‐Dinitrophenylhydrazones were converted to their parent carbonyl compounds using hexamethylenetetramine‐bromine complex supported onto wet alumina under classical heating and microwave irradiation.     

E/Z isomerism in monoalkylated derivatives of [Pt2(µ-S)2(PPh3)4] containing 2,4-dinitrophenylhydrazone substituents

Alkylation of [Pt₂(µ-S)₂(PPh₃)₄] with 2,4-dinitrophenylhydrazone-functionalized alkylating agents XC₆H₄C{=NNHC₆H₃(NO₂)₂}CH₂Br (X?=?H, Ph) gives monoalkylated cations [Pt₂(µ-S){µ-SCH₂C{=NNHC₆H₃(NO₂)₂}C₆H₄X}(PPh₃)₄]⁺. An X-ray diffraction study on [Pt₂(µ-S){µ-SCH₂C{=NNHC₆H₃(NO₂)₂}Ph}(PPh₃)₄]BPh₄ shows the crystal to be the Z isomer, with the phenyl ring and NHC₆H₃(NO₂)₂ groups mutually trans. ¹H- and ³¹P{¹H} NMR spectroscopic methods indicate a mixture of Z (major) and E (minor) isomers in solution, which slowly convert mainly to the E isomer. Reaction of [Pt₂(µ-S)₂(PPh₃)₄] with the dinitrophenylhydrazone of chloroacetone [ClCH₂C{=NNH(C₆H₃(NO₂)₂}Me] and NaBPh₄ gives [Pt₂(µ-S){µ-SCH₂C{=NNHC₆H₃(NO₂)₂}Me}(PPh₃)₄]BPh₄, which exists as a single (E) isomer.     

Quantification of 2,4-dinitrophenyl-hydrazones of low molecular mass aldehydes and ketones using HPLC

Summary This study was undertaken to evaluate the HPLC separation and quantification of several low molecular mass aldehydes and ketones, which may be produced during combustion in alcohol-fueled automobiles, by means of their dinitrophenylhydrazone derivatives. Stationary phases (ODS), mobile phase components (acetonitrile or methanol with water) and detection sensitivity at 254 and 365 nm were evaluated. Separation of eight dinitrophenylhydrazones could be achieved in approximately 20 minutes using a Zorbax ODS or a Supelcosil LC-PAH column with a MeOH:H₂O (7525 v/v) mobile phase. Complete separations were not obtained with either a Nova-Pack C-18 or an Ultrasphere ODS column. The use of acetonitrile-water mobile phases produces poorer resolution at all compositions tested. Quantification of the compounds by several methods was compared, with the lowest standard deviations being seen with the external than 1.5 pmol for each of the 2,4-dinitrophenylhydrazones in the test solution. The method is being applied to the analysis of aldehydes and ketones in the exhaust of automobile engines fueled by ethanolgasoline mixtures.Presented at the 19th ISC. Aix-en-Provence, France, September 13–18, 1992.