Determination of DMF modified DNA base N4-methylcarbamoylcytosine in human urine using off-line sample clean-up, two-dimensional LC and ESI-MS/MS detection.
A sensitive internal standard method for the analysis of a DNA-adduct of N,N-dimethylformamide (N4-methylcarbamoylcytosine, NMC-C) in human urine has been developed. A sample pre-treatment involving an acidic hydrolysis is followed by the sample clean-up performed with solid-phase extraction (SPE) technique using a cation-exchange resin. A two-dimensional liquid chromatography is used to separate the target analyte from the matrix using first a C18 reversed phase column with incorporated hydrophilic moieties and then a C8 bonded reversed phase column for the final separation. Quantification is carried out by positive electrospray ionisation and mass spectrometry detection of the transitions from molecule ions to product ions (169-->112 and 172-->115) for the analyte and the labelled internal standard, respectively. The detection limit in urine reaches down to 8 ng/L (48 pmol/L). In the general population NMC-C could not be detected. In 10 out of 32 urine samples of occupationally to DMF exposed subjects NMC-C could be detected. The concentrations ranged up to 172 ng/L (1023 pmol/L) with a 95th percentile of 121 ng/L (720 pmol/L).
Hennebrüder
Kristina
K
Institute and Outpatient Clinic of Occupational, Social and Environmental Medicine, University of Erlangen-Nuremberg, D-91054 Erlangen, Germany. k.hennebrueder@gmx.de
Angerer
Jürgen
J
D000395:Air Pollutants, Occupational / Q000009:adverse effects; D002138:Calibration; D002853:Chromatography, Liquid / Q000379:methods*; D003596:Cytosine / Q000031:analogs & derivatives* / Q000652:urine; D018736:DNA Adducts / Q000652:urine*; D004126:Dimethylformamide / Q000009:adverse effects / Q000737:chemistry*; D006801:Humans; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*
D000395:Air Pollutants, Occupational; D018736:DNA Adducts; C504127:N4-methylcarbamoylcytosine; D004126:Dimethylformamide; D003596:Cytosine