Development of a compound-specific isotope analysis method for acetone via 2,4-dinitrophenylhydrazine derivatization

Gas chromatography/combustion/isotope ratio mass spectrometric analysis of the stable carbon composition of tetrols

The stable carbon isotope compositions of tetrols, erythritol and threitol were determined by gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS). Using four tetrols with various delta(13)C values derivatized by methylboronic acid, the carbon isotope analysis method achieved excellent reproducibility and high accuracy. There was no carbon isotopic fractionation during the derivatization processes. The differences in the carbon isotopic compositions of methylboronates between the measured and calculated ranged from -0.20 to 0.12 per thousand, within the specification of the GC/C/IRMS system. It was demonstrated that delta(13)C values of tetrols could be calculated by a simple mass balance equation between tetrols, methylboronic acid, and methylboronates. The analogous 2-methyltetrols, marker compounds of photooxidation products of atmospheric isoprene, should have similar behavior using the same derivatization reagent. This method may provide insight on sources and sinks of atmospheric isoprene.

Carbon isotope effects of DDTs in carrot during the digestion process using an in vitro test

Compound-specific carbon isotope ratio analysis is a promising tool to assess the origins and fates of organic contaminants in many fields. The present study aims to investigate the isotope effects of dichloro-diphenyl-trichloroethane (DDT) and its degradates in carrots during digestion processes simulating the human gastrointestinal tract. To accurately interpret isotopic data obtained for unreleased DDTs (p,p-DDT, p,p-DDD and p,p-DDE) from carrots during digestion, spiked carrots with known delta(13)C values of DDTs were incubated in simulated gastric and intestinal solutions using a static in vitro model of the human gut. The delta(13)C values and concentrations of DDTs remaining in the carrot and in the digestive solutions were measured. The difference in the delta(13)C values of the added DDTs and the matrix-bound DDTs after digestion was always <0.50 per thousand, which is within the technical specification of the analytical system, although the released DDTs increased or decreased under the digestion conditions. The study demonstrated that there were no significant carbon isotopic fractionations during digestion. To our knowledge, this is the first report demonstrating the isotope effect of organic compounds during stomach and small intestine digestion, and the first reported isotope analyses of DDTs.

Improvement of 2,4-dinitrophenylhydrazine derivatization method for carbon isotope analysis of atmospheric acetone

Through simulation experiments of atmospheric sampling, a method via 2,4-dinitrophenylhydrazine (DNPH) derivatization was developed to measure the carbon isotopic composition of atmospheric acetone. Using acetone and a DNPH reagent of known carbon isotopic compositions, the simulation experiments were performed to show that no carbon isotope fractionation occurred during the processes: the differences between the predicted and measured data of acetone-DNPH derivatives were all less than 0.5 per thousand. The results permitted the calculation of the carbon isotopic compositions of atmospheric acetone using a mass balance equation. In this method, the atmospheric acetone was collected by a DNPH-coated silica cartridge, washed out as acetone-DNPH derivatives, and then analyzed by gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS). Using this method, the first available delta13C data of atmospheric acetone are presented.