Reductive amination of aldehyde 2,4-dinitorophenylhydrazones using 2-picoline borane and high-performance liquid chromatographic analysis.
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 C(1)-C(10) 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 C(1)-C(10) 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 x 10(4) (C(1)) to 2.2 x 10(4) L/mol/cm (C(10)). Complete separation between C(1)-C(10) 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 x 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.
Uchiyama
Shigehisa
S
Department of Environmental Health, National Institute of Public Health, 2-3-6, Minami, Wako City, Saitama 351-0197, Japan. uchiyama@niph.go.jp
Inaba
Yohei
Y
Matsumoto
Mariko
M
Suzuki
Gen
G
D016902:Air Pollution, Indoor / Q000032:analysis; D000447:Aldehydes / Q000032:analysis* / Q000737:chemistry; D000586:Amination; D001880:Boranes / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D006835:Hydrazones / Q000737:chemistry*; D010084:Oxidation-Reduction; D010659:Phenylhydrazines / Q000737:chemistry; D010847:Picolines / Q000737:chemistry*; D015203:Reproducibility of Results; D013056:Spectrophotometry, Ultraviolet / Q000379:methods
C001072:2,4-dinitrophenylhydrazone; D000447:Aldehydes; D001880:Boranes; D006835:Hydrazones; D010659:Phenylhydrazines; D010847:Picolines; C004787:2,4-dinitrophenylhydrazine; C530793:2-picoline