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Quantitative Mass Spectrometry Independence from Matrix Effects and Detector Saturation Achieved by Flow Injection Analysis with Real-Time Infinite Dilution
journal contribution
posted on 2013-12-17, 00:00 authored by Sergio C. NanitaA high-throughput
quantitative analysis method is presented to determine analyte concentrations
at the infinite dilution limit, where the presence and effects of
matrix become null, achieving mathematical independence from the detrimental
phenomenon of matrix effects. Dilution is achieved online, reproducibly
and in seconds by diffusion/mixing that occurs in flow injection analysis,
while analyte concentration measurements are made by electrospray
ionization tandem mass spectrometry. Because of matrix effects, the
measured analyte concentration (Am) was
inaccurate at high matrix concentrations, but accuracy consistently
improved as matrix concentration was reduced by dilution. The method
provides a practical solution around the decades-long matrix effects
problem in quantitative analytical chemistry without separation of
analytes from the matrix (e.g., chromatography) or use of corrective
procedures, such as matrix-matched standards or isotopically labeled
internal standards. Broad applications were demonstrated for part-per-billion
quantitation of bioactive molecules (pesticides) in extracts of food,
plant tissues, and body fluids by coupling the method to a high-throughput
sample extraction/cleanup based on salting out with ammonium formate.
The technique provides an assessment of matrix effects with remarkable
comprehensiveness, simplicity, and speed. A limit of quantitation
of 10 ng/g, a level appropriate for pesticide residue analysis and
bioanalytical applications, was demonstrated. The method is also independent
of detector saturation; this feature increased the applicable concentration
range 20–100-fold above that of conventional techniques. In
the abstract graphic, the measured analyte concentration (Am) approaches the accurate value (A0) when matrix effects disappear as measurements are conducted
while lowering the normalized sample concentration (Snorm) by real-time dilution.