Coupling supercritical fluid chromatography to positive ion atmospheric pressure ionization mass spectrometry : Ionization optimization of halogenated environmental contaminants

• Currently used analytical techniques for halogenated aromatic environmental contaminants such as polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), and biphenyls (PCBs), also known as legacy persistent organic pollutants, are based on gas chromatographic separation of target analytes and detection by mass spectrometry. The coupling of packed column supercritical fluid chromatography (SFC) to atmospheric pressure ionization mass spectrometry (API/MS) could allow for the concurrent analysis of thermally labile and legacy halogenated environmental contaminants if ionization can be sufficiently optimized. The evaluation of positive ion atmospheric pressure chemical ionization (APCI) and atmospheric pressure photoionization (APPI) as well as possible charge transfer dopants for the generation of molecular ion isotopomeric clusters of halogenated environmental contaminants with minimal fragmentation has been completed. Using the investigated parameters, positive ion APPI was found to be the more sensitive technique. Of the aromatic and cycloalkane dopants investigated, only fluorobenzene and trifluorotoluene were found to be effective dopants for the halogenated aromatic target analytes (PCDDs, PCDFs, and PCBs). Experiments involving deuterated dopants confirmed that reactive species generated by cycloalkanes were quenched by the SFC eluent rendering them unusable in conjunction with the investigated separation technique. Alternatively, aromatic dopants were found to be less susceptible to quenching by the SFC eluent and fluorobenzene was determined to be the most effective charge transfer dopant for PCDDs, PCDFs, and PCBs. To demonstrate the applicability of the optimized ionization conditions, SFC-API/MS has been used for the concurrent analysis of legacy halogenated aromatic environmental contaminants (PCDDs, PCDFs, and PCBs) and thermally labile analytes (alpha, beta, and gamma isomers of hexabromocyclododecane).

Ämnesord

NATURVETENSKAP  -- Fysik -- Atom- och molekylfysik och optik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Atom and Molecular Physics and Optics (hsv//eng)

Nyckelord

SFC

Positive APPI-MS

Environmental contaminants

PCDD

PCDF

PCB

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