High-performance liquid chromatography versus solid-phase extraction for post-derivatization cleanup prior to gas chromatography-electron-capture negative-ion mass spectrometry of N1,N3-bis-(pentafluorobenzyl)-N7-(2-[pentafluorobenzyloxy]ethyl)xanthine, a product derived from an ethylene oxide DNA.
J Chromatogr A 1993 Jan; 629(1):35-40
A post derivatization cleanup technique for use during the analysis of N7-(2-hydroxyethyl)guanine (NOHEtGua) in physiological samples was developed. The program was based on determining NOHEtGua, an ethylene-oxide (75218) DNA adduct, by gas chromatography/electron capture negative ionization mass spectrometry (GC/ECNIMS). N7-(2- Hydroxyethyl)xanthine (N7HEX), the reaction product of NOHEtGua and nitrous-acid, was used as the test substance. N7HEX was derivatized by reacting it with pentafluorobenzyl-bromide (PFBB) to form N1,N3- (pentafluorobenzyl)-N7-(2-(pentafluorobenzyloxy)ethyl)xanthine (PFBB/N7HEX). As little as 1.3 attomoles of PFBB/N7HEX could be detected by GC/ECNIMS; however, when reaction blanks were run through the GC/ECNIMS system, many interferent peaks appeared. To remove these, PFBB/N7HEX was dissolved in 50 microliters of 1:1 hexane/ethyl-acetate and applied to the top of solid phase extraction (SPE) columns prepared by packing 200 milligrams silica- gel into a 5.25 inch borosilicate Pasteur pipet containing silanized glass wool that had been prewashed with 1:1 ethyl-acetate/hexane. After washing sequentially with 4 milliliters (ml) hexane and 8ml 90:10 hexane/ethyl-acetate, the columns were eluted with 2ml ethyl- acetate. The eluates were analyzed by GC/ECNIMS. The technique was compared with a standard high performance liquid chromatography (HPLC) cleanup procedure by determining the percentage recovery of PFBB/N7HEX and examining samples containing no PFBB/N7HEX (reaction blanks) for interferents. The percentages of PFBB/N7HEX recovered after the SPE and HPLC cleanup were 56 and 60%, respectively. An interfering peak was observed in the ionchromatogram following the HPLC cleanup procedure, but not after the SPE cleanup. The detection limit was 95 picograms when the SPE cleanup procedure was used. The authors conclude that the SPE cleanup procedure is convenient and can be utilized in a technique for determining N7HEX.
NIOSH-Publication; NIOSH-Grant; Grants-other; Chemical-extraction; Chemical-reactions; Analytical-methods; Sample-preparation; Chromatographic-analysis; DNA-adducts; Biological-monitoring;
Medicinal Chemistry Northeastern University 360 Huntington Avenue Boston, MA 02115
Other Occupational Concerns; Grants-other;
Journal of Chromatography A
Northeastern University, Boston, Massachusetts