Reductive Amination of Aldehyde 2,4-Dinitorophenylhydrazones Using 2-Picoline Borane and High-Performance Liquid Chromatographic Analysis

• Published in: Analytical chemistry (Washington) Vol. 81; no. 1; pp. 485 - 489
• Main Authors: Uchiyama, Shigehisa, Inaba, Yohei, Matsumoto, Mariko, Suzuki, Gen
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.01.2009
• Subjects: Absorption; Air Pollution, Indoor - analysis; Aldehydes; Aldehydes - analysis; Aldehydes - chemistry; Amination; Analytical chemistry; Boranes - chemistry; Carbonyl compounds; Chemical compounds; Chemistry; Chromatographic methods and physical methods associated with chromatography; Chromatography; Chromatography, High Pressure Liquid - methods; Exact sciences and technology; Hydrazones - chemistry; Liquid chromatography; Measurement; Other chromatographic methods; Oxidation-Reduction; Phenylhydrazines - chemistry; Picolines - chemistry; Reproducibility of Results; Spectrophotometry, Ultraviolet - methods; Wavelengths; Phosphoric acid; Carbonyl compounds; Borane; Peak resolution; HPLC chromatography; Absorption coefficient; Air; Aldehyde; Carbonyl; Organic hydrazine; Amination; Acetonitrile; Geometrical isomer; Hydrazone; Room temperature
• ISSN: 0003-2700; 1520-6882; 1520-6882
• DOI: 10.1021/ac802163y

A new method for the determination of carbonyls in air using 2,4-dinitrophenylhydrazine (DNPH) has been developed. The traditional method for the measurement of carbonyl compounds, using DNPH to form the corresponding 2,4-dinitrophenylhydrazone (DNPhydrazone) derivatives, is subject to analytical errors because DNPhydrazones form both E- and Z-geometrical isomers as a result of the CN double bond. To overcome this issue, a method for transforming the CN double bond into a CN single bond, using reductive amination of DNPhydrazone derivatives, has been developed. Reductive amination of aldehyde DNPhydrazones was carried out by adding 2-picoline borane acetonitrile solution in eluate through the DNPH-cartridge. The amination reactions of C1−C10 aldehyde DNPhydrazones were completely converted into the reduced forms within 40 min in the presence of 1 mmol/L 2-picoline borane and 20 mmol/L of phosphoric acid. These reduced forms were very stable and did not change when stored for 2 weeks at room temperature. The absorption maximum wavelengths of the reduced forms from C1−C10 aldehyde DNPhydrazones were 351−352 nm and shifted 6−7 nm toward shorter wavelengths when compared to the corresponding DNPhydrazones, and the molar absorption coefficients were 1.5 × 104 (C1) to 2.2 × 104 L/mol/cm (C10). Complete separation between C1−C10 aldehyde DNPhydrazones and the corresponding reduced forms can be achieved by operating the HPLC in gradient mode using an Ascentis RP-Amide column (150 mm × 4.6 mm i.d.). The RSDs of DNPhydrazone (Z + E) peak areas ranged from 0.40−0.66 and those of the corresponding reduced forms ranged from 0.26−0.41. It was shown that the reductive amination method gave improved HPLC analytical precision because of the absence of isomers.