An Interface for Direct Analysis of ¹⁴C in Nonvolatile Samples by Accelerator Mass Spectrometry

Abstract

We describe here apparatus and methods for direct analysis of (14)C in biological specimens by accelerator mass spectrometry (AMS). Liquid samples, including plasma and urine, are deposited by pipet into a bed of CuO powder that fills a space within a rigid, refractory support. Volatile components are removed under reduced pressure prior to analysis. The CuO matrix is locally heated with an infrared laser while it is contained within a sealed chamber that is swept with He carrier gas. Heating induces combustion of the applied sample, and the carrier gas transports the CO(2) that is formed to the AMS instrument's ion source, which is appropriately modified for use with CO(2). A rodent study of drug clearance with [(14)C]-acetaminophen was performed to provide plasma and urine specimens, which were analyzed with this overall approach and by liquid scintillation counting for comparison. Results presented here confirm the potential utility of laser-induced sample combustion as an alternative to graphite production for AMS analysis of (14)C. Anticipated benefits of the present approach include reduced risk of sample cross-contamination, decreased analysis time, and greater compatibility with robotics.

How to Convert Biological Carbon Into Graphite for AMS

“…Figures 4 to 6 show some characteristic difficulties and advantages associated with nutritional and biological samples. Specifically, the scientist must work with a large series of similar, relatively homogenous samples to obtain useful data, but the samples are good candidates for batch processing, automation, and potentially, direct injection of combustion CO 2 into a gas-accepting ion source (Liberman, et al 2004). The results from these studies were used to construct a kinetic model of folate metabolism, which indicated that the absorbed fraction of the administered dose ranged from 65 to 97% with mean value of 79 %, and there was no correlation between fractional absorption and intake of folate.…”

DNA adducts formed by a novel antitumor agent 11β-dichloro in vitro and in vivo

“…The amount of 11h-dichloro covalently bound to proteins was assessed by determining the 14 C activity in aliquots of the supernatant (organic soluble phase) and precipitate.…”

“…Cells were detached by trypsin/EDTA after 36 hours and the number of cells in control and 11h-dichloro-treated wells determined using a Coulter Counter. The percent growth inhibition is the ratio of cell number in treated and control wells multiplied by 100. mct.aacrjournals.org Downloaded from described in detail elsewhere (14). DNA concentrations were determined by UV absorption at 260 nm using a Beckman DU-65 UV-Vis Spectrophotometer.…”

“…The high sensitivity of the accelerator mass spectrometry technique permitted us to detect and quantify the levels of covalently bound 14 C that were present in cellular DNA. We first established a dose-response relationship for adduct formation by treating LNCaP cells with 2.5, 5, or 10 Amol/L [ 14 C]-11h-dichloro for 4 hours.…”

Development of Novel Bifunctional Compounds That Induce Apoptosis in Prostate Cancer Cells

“…Using a radiolabeled analog that incorporated one 14 C atom into the linker of our molecule we have used the technique of Accelerator Mass Spectrometry (AMS) to detect and quantify [ 14 C]-11β-DNA adducts in treated cells. This permitted us to define the doseresponse relationship between the concentration of 11β in cell culture media and the level of total DNA adducts in cells (Fig.2).…”