Atmospheric-Pressure Dielectric Barrier Discharge as an Elemental Ion Source for Gas Chromatographic Analysis of Organochlorines

Abstract

Atmospheric-pressure dielectric barrier discharge (AP-DBD) plasma has emerged in recent years as a versatile plasma for molecular ionization and elemental spectroscopy. However, its capabilities as an elemental ion source have been less explored, partly because of difficulties in the detection of positive elemental ions from this low-gas-temperature plasma. In this work, we investigate the detection of negative elemental ions to enable elemental mass spectrometry (MS) using AP-DBD. A gas chromatograph is coupled to a helium AP-DBD apparatus and positioned in front of an atmospheric-pressure-sampling mass spectrometer with no modifications to the ion sampling interface. We demonstrate that Cl ions are detected with a compound-independent efficiency, enabling elemental quantification of organochlorines. Further, addition of oxygen at low concentration (11 ppm, v/v) to the helium plasma improves the analytical performance by reducing postcolumn peak broadening, whereas high oxygen concentrations (>110 ppm, v/v) lead to loss of the compound-independent response. The optimized GC-AP-DBD-MS setup shows close to 2 orders of magnitude of linearity for its compound-independent Cl response and offers detection limits of 0.5-1 pg of Cl on column (0.6 pg/s), suitable for analysis of organochlorines in food samples. We demonstrate this capability by analyzing orange juice spiked with pesticides at 9 μg/L and a single internal standard. Importantly, we demonstrate that a quick, easy, cheap, effective, rugged, and safe (QuEChERS) extraction followed by GC-AP-DBD-MS quantification using the single standard provides acceptable recoveries (80-120%). These results highlight uniform QuEChERS extraction of a range of compounds and the compound-independent response of AP-DBD for Cl, making the combination of the two methods desirable for the rapid quantification of organochlorines. Furthermore, we discuss ionization matrix effects in AP-DBD for chlorine detection and offer strategies to flag matrix-impacted analytes. These results suggest that AP-DBD has the potential to become a unified ion source for both elemental quantification and molecular identification of GC eluents on a single MS platform.

Facile Removal of Phytochromes and Efficient Recovery of Pesticides Using Heteropore Covalent Organic Framework-Based Magnetic Nanospheres and Electrospun Films

“…An important step of nontargeted analysis is sample pretreatment. An ideal sample pretreatment strategy should remove interfering matrices as much as possible, while achieving the highly efficient recovery of potential chemical hazards. , To date, commonly used sample pretreatment techniques include QuEChERS, , ultrasound-assisted liquid–liquid extraction, and solid–liquid micro-extraction . QuEChERS has attracted special attention among these techniques because of the merits of being “quick, easy, cheap, effective, rugged, and safe”.…”

Point Discharge Optical Emission Spectrometer as a Gas Chromatography (GC) Detector for Speciation Analysis of Mercury in Human Hair

“…Therefore, microplasma OES can be used as a potentially alternative GC detector to AAS/AFS/ICP-OES/ICP-MS, which can connect the GC column as close as possible, thus improving sensitivity, minimizing analyte loss and reducing power consumption. Most recently, we have successfully used DBD-OES as a multichannel and elemental-specific GC detector for the determinations of halohydrocarbons, volatile carbon-containing compounds, and mercury species. ,− The DBD-OES system significantly reduced instrumental and analytical cost and alleviated other disadvantages of conventional atomic-spectrometer-based GC detectors.…”

Elemental Fluorine Detection by Dielectric Barrier Discharge Coupled to Nanoelectrospray Ionization Mass Spectrometry for Nontargeted Analysis of Fluorinated Compounds

“…One mechanism for Na 2 F + formation is the production of F − by DBD and subsequent conversion of this ion to Na 2 F + via interactions with nano-ESI droplets. Although Cl − has been readily detected from DBD reactions of organochlorines, 20 proton-transfer reactions of F − with acidic plasma products such as HNO 3 make the survival of F − to the ionization region an unlikely scenario. Nevertheless, we evaluated the potential contribution of F − to Na 2 F + formation by implementing postplasma ion deflection via inserting a wire electrode into the center of the postplasma steel tube (see Figure S3).…”

“…Importantly, the ionization approach is versatile and provides an avenue to use a wide range of plasmas. In particular, we utilize a dielectric barrier discharge (DBD), a nonthermal plasma with tunability from a reactive plasma for dissociating chemical bonds to soft ionization, offering facile operation and coupling to MS platforms. − We employ dissociative properties of the DBD to create fluorine-specific plasma products from GC-separated fluorochemicals. The plasma products are then ionized using nanoelectrospray ionization (nano-ESI), providing a general and nontargeted elemental detection scheme for fluorinated compounds.…”