A target screening method for detection of organic pollutants in fruits and vegetables by atmospheric pressure gas chromatography quadrupole-time-of-flight mass spectrometry combined with informatics platform.

This study employed an atmospheric pressure gas chromatography quadrupole-time-of-flight mass spectrometry (APGC-QTOF-MS) combined with UNIFI scientific platform to establish a scientific screening library for the screening of 104 organic contaminants in fruits and vegetables. The developed approach shortened the analysis time in comparison with the traditional gas chromatography mass spectrometer (GC-MS/MS). All compounds can be separated by using the three-dimensional (3D) acquisition mode supported by UNIFI platform. The percentage of organic contaminants detected with the tolerance ( ± 5 ppm mass accuracy and ± 0.2 min retention time) was in the range 71.4 ± 8.7%-93.3 ± 1.03% at the 10 µg kg-1 and 94.3 ± 1.2%-99.0 ± 3.4% at the 50 µg kg-1. The estimated limit of detection (LODs) of the 104 organic contaminants in different matrixes was between 0.02 and 6.00 µg kg-1. The scientific screening library and UNIFI informatics platform were successfully applied to monitor the target analytes in fruit and vegetable samples.

Evaluation of multiple alternative instrument platforms for targeted and non-targeted dioxin and furan analysis.

The use of gas chromatography coupled to high-resolution magnetic sector mass spectrometers (GC-HRMS) is well established for dioxin and furan analysis. However, the use of gas chromatography coupled to triple quadrupole (MS/MS) and time of flight (TOF) mass spectrometers with atmospheric pressure ionization (API) and traditional electron ionization (EI) for dioxin and furan analysis is emerging as a viable alternative to GC-HRMS screening. These instruments offer greater versatility in the lab for a wider range of compound identification and quantification as well as improved ease of operation. The instruments utilized in this study included 2 API-MS/MS, 1 traditional EI-MS/MS, an API-quadrupole time of flight mass spectrometer (API-QTOF), and a EI-high-resolution TOF (EI-HRTOF). This study compared these 5 instruments to a GC-HRMS using method detection limit (MDLs) samples for dioxin and furan analysis. Each instrument demonstrated acceptable MDL values for the 17 chlorinated dioxin and furans studied. The API-MS/MS instruments provide the greatest overall improvement in MDL value over the GC-HRMS with a 1.5 to 2-fold improvement. The API-QTOF and EI-TOF demonstrate slight increases in MDL value as compared with the GC-HRMS with a 1.5-fold increase. The 5 instruments studied all demonstrate acceptable MDL values with no MDL for a single congener greater than 5 times that for the GC-HRMS. All 5 instruments offer a viable alternative to GC-HRMS for the analysis of dioxins and furans and should be considered when developing new validated methodologies.

Assessment of Ah receptor transcriptional activity mediated by halogenated dibenzo-p-dioxins and dibenzofurans (PXDD/Fs) in human and mouse cell systems.

Polybrominated and mixed bromo/chloro dibenzo-p-dioxins and dibenzofurans (PXDD/Fs) are emerging environmental contaminants of concern. Thus far, an understanding of the toxicological behavior of these chemical species and their impact upon human health is incomplete. Here we utilized human and mouse hepatocellular carcinoma cell lines to examine the ability of differentially halogenated PXDD/F congeners to induce aryl hydrocarbon receptor (AHR)-mediated transcriptional activity. Dose-response experiments in reporter cell lines identified varied potencies among differentially halogenated PXDD/F isomers by comparison of EC50 values relative to the prototypical AHR agonist, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Brominated PXDD/F species displayed reduced capacity to activate the mouse AHR, compared to TCDD. Only BrCl3 dibenzo-p-dioxin was found to have a greater relative potency than TCDD to induce human AHR transcriptional activity. Human cells required ∼10-29-fold higher ligand concentrations to induce analogous AHR activity, relative to mouse cells. Decreased sensitivity of the human AHR to brominated dibenzofuran congeners directly corresponded to the number of bromine functional groups. Mixtures of these compounds exhibited an additive effect on AHR activation. The data also support the inclusion of mixed halogenated dibenzo-p-dioxins and dibenzofurans into routine environmental screening procedures as well as more thorough toxicological characterization of PXDD/Fs.

Quantitative Analysis of Mixed Halogen Dioxins and Furans in Fire Debris Utilizing Atmospheric Pressure Ionization Gas Chromatography-Triple Quadrupole Mass Spectrometry.

Residential and commercial fires generate a complex mixture of volatile, semivolatile, and nonvolatile compounds. This study focused on the semi/nonvolatile components of fire debris to better understand firefighter exposure risks. Using the enhanced sensitivity of gas chromatography coupled to atmospheric pressure ionization-tandem mass spectrometry (APGC-MS/MS), complex fire debris samples collected from simulation fires were analyzed for the presence of potentially toxic polyhalogenated dibenzo-p-dioxins and dibenzofurans (PXDD/Fs and PBDD/Fs). Extensive method development was performed to create multiple reaction monitoring (MRM) methods for a wide range of PXDD/Fs from dihalogenated through hexa-halogenated homologue groups. Higher halogenated compounds were not observed due to difficulty eluting them off the long column used for analysis. This methodology was able to identify both polyhalogenated (mixed bromo-/chloro- and polybromo-) dibenzo-p-dioxins and dibenzofurans in the simulated burn study samples collected, with the dibenzofuran species being the dominant compounds in the samples. Levels of these compounds were quantified as total homologue groups due to the limitations of commercial congener availability. Concentration ranges in household simulation debris were observed at 0.01-5.32 ppb (PXDFs) and 0.18-82.11 ppb (PBDFs). Concentration ranges in electronics simulation debris were observed at 0.10-175.26 ppb (PXDFs) and 0.33-9254.41 ppb (PBDFs). Samples taken from the particulate matter coating the firefighters' helmets contained some of the highest levels of dibenzofurans, ranging from 4.10 ppb to 2.35 ppm. The data suggest that firefighters and first responders at fire scenes are exposed to a complex mixture of potentially hundreds to thousands of different polyhalogenated dibenzo-p-dioxins and dibenzofurans that could negatively impact their health.

Comparison of Atmospheric Pressure Ionization Gas Chromatography-Triple Quadrupole Mass Spectrometry to Traditional High-Resolution Mass Spectrometry for the Identification and Quantification of Halogenated Dioxins and Furans.

The goal of this study was to qualify gas chromatography coupled to atmospheric pressure ionization tandem mass spectrometry (APGC-MS/MS) as a reliable and valid technique for analysis of halogenated dioxins and furans that could be used in place of more traditional gas chromatography coupled to high-resolution mass spectrometry (GC-HRMS) analysis. A direct comparison of the two instrumental techniques was performed. APGC-MS/MS system sensitivity was demonstrated to be on the single femtogram level. The APGC-MS/MS analysis also demonstrated method detection limits (MDLs) in both sediment and fish that were 2-18 times lower than those determined for the GC-HRMS. Inlet conditions were established to prevent issues with sample carry-over, due largely to the enhanced sensitivity of this technique. Additionally, this work utilized direct injection for sample introduction through the split/splittless inlet. Finally, quantification of both sediment and fish certified reference materials were directly compared between the APGC-MS/MS and GC-HRMS. The APGC-MS/MS performed similarly to, if not better than, the GC-HRMS instrument in the analysis of these samples. This data is intended to substantiate APGC-MS/MS as a comparable technique to GC-HRMS for the analysis of dioxins and furans.

Comprehensive characterization of the halogenated dibenzo-p-dioxin and dibenzofuran contents of residential fire debris using comprehensive two-dimensional gas chromatography coupled to time of flight mass spectrometry.

A comprehensive approach was taken to characterize the polyhalogenated dibenzo-p-dioxin and dibenzofuran contents of fire debris. Household and electronics fire simulations were performed to create samples representative of those firefighters most typically come in contact with. Sample analysis was performed using GC×GC-TOFMS to provide a comprehensive profile of the halogenated dioxins and furans present among the two types of fire debris. Both the household fire and electronics fire simulations produced a significant amount of polybrominated dibenzofurans. Only the electronics rich fire simulation produced mixed halogenated (Br/Cl) dibenzofurans in amounts above the limit of detection of the analytical method. Of the mixed halogenated dibenzofurans identified, a majority were those having no commercially available standard to allow for specific congener identification. GC×GC-TOFMS was extremely beneficial for the identification of compound classes due to the manner in which compounds classify in the two-dimensional chromatographic plane, thus aiding data reduction for these materials.