Evaluation of Behavioral Differences between Native Polycyclic Aromatic Hydrocarbons and 13C-Labeled Internal Standards during Clean-up Steps of Analysis

Abstract

We confirmed that concentrations of polycyclic aromatic hydrocarbons (PAHs) obtained by isotope dilution mass spectrometry (IDMS) using the corresponding 13 C-labeled internal standards are reliable even after clean-up steps. Change in the ratio of phenanthrene to 13 C6-phenanthrene was less than 0.2%, although the recovery yield of 13 C6-phenanthrene decreased to 60%. Since changes in the ratios were commonly within the relative standard deviations of the concentrations (1.5 -5.4%) obtained using gas chromatography-mass spectrometry in combination with pressurizedliquid extraction, concentrations obtained by IDMS with 13 C-PAHs should be reliable.

Evaluation of minimal 13C-labelling for stable isotope dilution in organic analysis

“…The experimental isotope abundances at a given mass were calculated by dividing the peak area of that mass in the mixture by the sum of all areas. The molar fractions x nat and x lab were calculated using eqns (7) and (8). Matrix A corresponded to the values shown in Table 2 and Fig.…”

“…In general, the concentration of the labelled compound will be calculated from reverse isotope dilution experiments and its final uncertainty will show a contribution of the uncertainty in the concentration of the natural abundance standard. The second important source of uncertainty in the multiple linear regression procedure is the isotope composition of both natural abundance and labelled compounds which are used to construct the matrix A in eqns (7) and (8). In our case, the uncertainties in the isotope composition of the natural and labelled compounds should take into account also the uncertainties in the fragmentation factors as shown in Table 2.…”

“…3 However, when multiple labelling of a molecule is performed, differences in its physicochemical properties in comparison with the natural abundance compound have been observed. [8][9][10][11] This is particularly true with deuterated compounds, because of slightly different hydrogen bonding capabilities, resulting in slightly different extraction and derivatisation yields from those observed for the natural abundance compounds. 8 Also, undesired changes in retention times both in GC 9 and LC 10 separations have been reported.…”

“…[8][9][10][11] This is particularly true with deuterated compounds, because of slightly different hydrogen bonding capabilities, resulting in slightly different extraction and derivatisation yields from those observed for the natural abundance compounds. 8 Also, undesired changes in retention times both in GC 9 and LC 10 separations have been reported. Most of these isotopic effects are small and can be compensated for when the calibration graph is constructed following the analytical procedure used for the samples.…”

Differences in the Yields of Polycyclic Aromatic Hydrocarbons by Pressurized Liquid Extraction and the Japanese Official Method

“…[11][12][13] Although one study found that ultrasonic extraction can obtain comparable yields to those obtained by other techniques, 14 another found that this procedure is not as efficient at extracting BaP as Soxhlet extraction. 15 Although both Soxhlet extraction [16][17][18][19] and PLE 20 have also been used to determine PAHs in sediments collected in Japan, differences in the yields of PAHs obtained by PLE and the Japanese official method can be expected to be the largest among extraction methods if they occur. 20 In this study, we optimized the temperature and pressure of extraction by PLE.…”