Analytical Chemistry Chemical Cytometry Quantitates Superoxide

ment. Therefore, the long-time dreamed of chromatographic
detection allowing generic quantification and complete characterization
of organic compounds in a single instrument is
realized. In addition, the proposed method turned out to be
very cost-effective because expenses associated with the use
of isotopically labeled 13 CO2 are negligible and there is no need
for external calibration, resulting in considerable savings in time
and money (e.g., cost of analytical standards). Beyond its
potential use for quantitative quality control in a wide range of
standard laboratories (e.g., environmental ones), a powerful
application of our approach can be foreseen in oil-spill fingerprinting
and in pharmaceutical analysis, for which the number
of target organic analytes is increasing exponentially (so it is
virtually impossible to have standards for each compound, even
if they exist).
In addition, the unique compound-independent calibration
capabilities of the approach proposed could be advantageously
exploited for the assessment of sample introduction procedures
in GC. In the present work, we have selected HS-SPME to
illustrate this promising ability of our approach. Quantitative data
obtained for BTEX compounds in different water samples have
demonstrated that quantitative assessment of HS-SPME procedures
in terms of absolute absorption yields is successful (the
analytical features of different fiber coatings could be evaluated
and critically compared in this way), opening its use to assess
the performance of many other reported sample preparation and
preconcentration methods.
ACKNOWLEDGMENT
Financial support was provided by the Spanish Ministry of
Education (CTQ2006-05722) and FICYT (PC06-016) and technical
support by KONIK-TECH. J.R.E. acknowledges the MEC (European
Social Fund) for a Ramon y Cajal contract, and S.C.D.
acknowledges the FICYT for a PhD grant.
SUPPORTING INFORMATION AVAILABLE
The mass spectrum obtained for the mass range 43-47 when
1 mL/min of the spike flow was introduced directly to the ion
source (Figure SI-1). The optimization of the integration time for
the 44/45 isotope ratio measurement (Figure SI-2). The short term
(30 min) and long term (9 h) stability of the 12 CO2/ 13 CO2 isotope
ratio (Figures SI-3 and SI-4, respectively). The quantification
results of a mixture of different families of compounds containing
saturated, insaturated and functionalized compounds (Table SI-
1). The Kfs values obtained for reliable comparison between the
different fibers used (Table SI-2). The multiple headspace
experiment carried out for internal validation of the approach,
comparing the sum of the amount obtained in each single
extraction to the total amount initially present in the spiked
solution (Table SI-3). This material is available free of charge via
the Internet at http://pubs.acs.org.
Received for review April 12, 2010. Accepted July 2, 2010.
AC101103N
Analytical Chemistry, Vol. 82, No. 16, August 15, 2010
6869