Comparison of a variety of gas chromatographic columns with different polarities for the separation of chlorinated dibenzo-p-dioxins and dibenzofurans by high-resolution mass spectrometry

Detection Method and Common Characteristics of Waste Solvent from Semiconductor Industry

The recycling of organic solvents is a widely discussed topic. The waste organic solvents from thin-film-transistor liquid-crystal display (TFT-LCD) production is characterized by large quantities, multiple types, and complex compositions. Thus, the unified and compatible component analysis method is important for studying the recovery of waste organic solvents. In our work, based on the study of existing analytical methods, we designed a compatible method for the analysis of moisture using Karl Fischer analysis, for the analysis of organic compounds using gas chromatography, and for the analysis of the photoresist and other solids by evaporation. These were specific methods for analyzing the components of near-total formulation thin-film-transistor liquid-crystal display waste organic solvent. The organic matter content was analyzed via gas chromatography with a CP-Sil8CB column and flame ionization detector. The initial temperature of the column was 90 °C and the holding time was 1 min. The heating rate was 30 °C/min. The temperature was raised to 270 °C for 7 min. The internal standard method and the external standard method were used to determine the content of the main components of organic compounds. The relative standard deviation of the analytical results was 1.14~2.93%, 1.21~4.74% and 0.61%, respectively. The analytical results had good accuracy, but the external standard method was better; the recoveries were 99.76~107.60%, 95.86~107.70%, and 95.23~96.88%, respectively. Based on the composition analysis, the composition rule of the waste organic solvent was summarized. Through the exploration of the effect of the waste solvent, the common characteristics of the waste solvent were obtained. This study provides a good strategy and an optimized method for improving the efficiency of organic solvent recovery.

Comprehensive two-dimensional gas chromatography thermodynamic modeling and selectivity evaluation for the separation of polychlorinated dibenzo-p-dioxins and dibenzofurans in fish tissue matrix

Comprehensive two-dimensional gas chromatography (GC×GC) is a powerful tool for complex separations. The selectivity and sensitivity benefits from thermally modulated GC×GC were applied to the analysis of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). Thermodynamic indices of 50 PCDD/Fs, including the 17 toxic 2378-substituted congeners, were collected and used to model one-dimensional and two-dimensional separations with the Rtx-Dioxin2 and Rxi-17SilMS capillary GC columns. Thermodynamic modeling was used to determine the optimal conditions to take advantage of the selectivity differences between the Rxi-17SilMS and Rtx-Dioxin2 to separate all PCDD/Fs congeners from the 2378-substituted compounds by GC×GC. The modeled elution order patterns closely matched the experimental elution order in 40 of the 45 tetrachlorinated through hexchlorinated compounds analyzed. The heptachlorinated and octachlorinated congeners were not included in the elution order modeling as they are readily resolved from other dioxin congeners. The Rxi-17SilMS crossed with the Rtx-Dioxin2 was able to separate all 2378-substituted compounds in a single separation in a fish matrix. Thirty-three additional PCDD/F congeners were added to the fish matrix that coelute with the 2378-substituted congeners. The Rxi-17SilMS crossed with the Rtx-Dioxin2 was able to fully resolve 11 of the 2378-substituted congeners with the other six congeners exhibiting coelutions with only one other congener.

The Rtx-Dioxin2 and Rxi-17SilMS as Alternative Gas Chromatographic Confirmation Columns for Dioxin Analysis

Polychlorinated dibenzo-p-dioxins and furans are environmentally persistent and highly toxic compounds. 136 chlorinated dioxins and furan congeners contain at least four chlorine atoms and pose a complex separation challenge in environmental and biological matrixes. The complexity arises from the dioxin and furan molecules with substitutions at positions 2, 3, 7, and 8, which are toxicologically relevant but are not easily separated from the other non-/less toxic congeners. Many regulatory methods require the use of two columns with different polarities or selectivity for dioxin analysis. The most common confirmation column pair is a (5% phenyl)-methylpolysiloxane and a (biscyanopropyl-/ cyanopropylphenyl)-methylpolysiloxane. These phases are required in USEPA-1613 for 2,3,7,8-tetrachlorodibenzo-p-dioxin and 2,3,7,8-tetrachlorodibenzofuran specificity. However, other column phases, such as the Rxi-17SilMS and the Rtx-Dioxin2, offer alternatives to the traditional column pairing and provide a similar or better separation of 2,3,7,8-substituted congeners. This study compares four columns for dioxin analysis: the Rtx-Dioxin2, Rxi-17SilMS, Rxi-5SilMS, and Rtx-2330. All columns used in this study are capable of meeting the requirements for dioxin analysis required by USEPA-1613. However, the Rtx-Dioxin2 demonstrated improved selectivity for a wider range of dioxin compounds than the Rxi-5SilMS. The Rtx-Dioxin2 is capable of resolving 2,3,7,8-tetrachlorodibenzo-p-dioxin and 2,3,7,8-tetrachlorodibenzofuran from common interferants better than the Rxi-5SilMS and can be used as a confirmation column with either the Rtx-2330 or Rxi-17SilMS.

Emissions of 2,3,7,8-substituted and non-2,3,7,8-substituted polychlorinated dibenzo-p-dioxins and dibenzofurans from secondary aluminum smelters

The secondary aluminum smelting industry is an important source of polychlorinated dibenzo-p-dioxin and dibenzofurans (PCDD/Fs). However, the formations and emissions of non-2,3,7,8-PCDD/Fs have rarely been studied. Non-2,3,7,8-PCDD/Fs may also be metabolically toxic to mammalians. In this study, four typical secondary aluminum smelters were selected as demonstration smelters and the composition of the raw material they used was adjusted to investigate the influence on PCDD/F emissions and profiles. In addition to 17 congeners of 2,3,7,8-PCDD/Fs, 64 congeners of non-2,3,7,8-PCDD/Fs were firstly reported. Strong, positive correlations were found between non-2,3,7,8-PCDD/Fs and 2,3,7,8-PCDD/Fs. The concentrations of 2,3,7,8-PCDD/Fs in stack gas and fly ash samples were 120.7-870.4 pg/Nm³ and 13.40-292.9 ng/g, respectively. Those of non-2,3,7,8-PCDD/Fs in the stack gas and fly ash samples were 84.03-1183.7 pg/Nm³ and 7.20-344.7 ng/g, respectively. The raw material composition was a key factor affecting PCDD/F emissions and profiles. An analysis of Gibbs free energies (ΔG_f) showed that non-2,3,7,8-PCDD/Fs could be transformed into 2,3,7,8-PCDD/Fs, which would increase the PCDD/F environmental risks. The emission inventories of 2,3,7,8-PCDD/Fs, non-2,3,7,8-PCDD/Fs, and International Toxic Equivalents from Chinese secondary aluminum smelters in 2013 were 8247 g, 7253 g, and 608.6 g, respectively. The results of this study could contribute to potential risk evaluations and effective reduction of non-2,3,7,8-PCDD/Fs.

The polychlorinated dibenzofuran fingerprint of iron ore sinter plant: Its persistence with suppressant and alternative fuel addition

An earlier demonstration that the relative concentrations of isomers of polychlorinated dibenzofuran do not vary as the flamefront of an iron ore sinter plant progresses through the bed, and profiles are similar for two sinter strands has been widened to include studies of the similarity or otherwise between full scale strand and sinter pot profiles, effect of addition of suppressants and of coke fuel substitution with other combustible materials. For dioxin suppressant addition, a study of the whole of the tetra- penta- and hexaCDF isomer range as separated by the DB5MS chromatography column, indicates no significant change in profile: examination of the ratios of the targeted penta- and hexaCDF isomers suggests the profile is similarly unaffected by coke fuel replacement. Addition of KCl at varied levels has also been shown to have no effect on the 'fingerprint' and there is no indication of any effect by the composition of the sinter mix. The recently published full elution sequence for the DB5MS column is applied to the results obtained using this column. It is confirmed that isomers with 1,9-substitution of chlorine atoms are invariably formed in low concentrations. This is consistent with strong interaction between the 1 and 9 substituted chlorine atoms predicted by DFT thermodynamic calculations. Non-1,9-substituted PCDF equilibrium isomer distributions based on DFT-derived thermodynamic data differ considerably from stack gas distributions obtained using SP2331 column separation. A brief preliminary study indicates the same conclusions (apart from the 1,9-interaction effect) hold for the much smaller content of PCDD.

Formation of dioxins during exposure of pesticide formulations to sunlight

Chlorinated pesticides can contain impurities of dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), and their precursors, as a result of various manufacturing processes and conditions. As precursor formation of PCDD/Fs can also be mediated by ultraviolet light (UV), this study investigated whether PCDD/Fs are formed when currently used pesticides are exposed to natural sunlight. Formulations containing pentachloronitrobenzene (PCNB; n=2) and 2,4-dichlorophenoxyacetic acid (2,4-D; n=1) were exposed to sunlight in quartz tubes, and the concentration of 93 PCDD/F congeners were monitored over time. Considerable formation of PCDD/Fs was observed in both PCNB formulations (by up to 5600%, to a maximum concentration of 57000 μg ∑PCDD/F kg(-1)) as well as the 2,4-D formulation (by 3000%, to 140 μg ∑PCDD/F kg(-1)). TEQ also increased by up to 980%, to a maximum concentration of 28 μg kg(-1) in PCNB, but did not change in the 2,4-D formulation. Assuming similar yields as observed in the present study as a worst case scenario the use of PCNB in Australia may result in the formation of 155 g TEQ annum(-1), contributed primarily by OCDD formation. This warrants detailed evaluations on the contemporary release of PCDD/Fs to the environment after the use of pesticides. Changes in congener profiles (including the ratio of PCDDs to PCDFs (DF ratio)) suggest that pesticide sources of PCDD/Fs after sunlight exposure may not be recognized based on matching source fingerprints established from manufacturing impurities. These changes also provide preliminary insights into the possible formation routes and types of precursors involved.

Retention time profiling of all 136 tetra- through octa- chlorinated dibenzo-p-dioxins and dibenzofurans on a variety of Si-Arylene gas chromatographic stationary phases

The applicability of three different Silphenylene Silicone co-polymer (Si-Arylene) GC stationary phases (J&W Scientific DB-5ms, Varian VF-5ms, and VF-Xms) has been evaluated for the separation of all 136 tetra- through the octa- chlorinated dibenzo-p-dioxins (PCDD) and chlorinated dibenzofurans (PCDF) from closely eluting isomers using gas chromatography/high resolution mass spectrometry (GC/HRMS). Their relative performance data are compared to the "conventional" 5% diphenyl 95% dimethylpolysiloxane GC column (Supelco Equity-5) and to each other based on absolute retention times, visualized mass chromatograms, and the separation of 2,3,7,8-substituted isomers. VF-Xms GC column was able to demonstrate a better performance towards separation of 2,3,7,8-substituted PCDD/PCDF compared to other Si-Arylene GC columns tested, where only 2,3,4,7,8-PnCDF can not be resolved from 1,2,3,6,9-PnCDF and 2,3,4,6,7,8-/1,2,3,6,8,9-HxCDF and 1,2,3,7,8,9-/1,2,3,4,8,9-HxCDF can be at least partially resolved. These data suggest that the development of a single GC column for the separation of all 17 2,3,7,8-substituted dioxins and furans is feasible, which therefore could be used as a standard tool for the PCDD/PCDF methods globally including USEPA methods 1613b, 8290A, 8280B, European Standard Method EN 1948, Canadian methods DFPCB-E3418, EPS 1/RM/19, Japanese methods JIS K0311 and JIS K0312. Having one specific GC column to separate all 2,3,7,8-substituted PCDD/PCDF will significantly improve the data quality, comparability by the various methods and assessment techniques while simultaneously leading to a more cost and time efficient operation.

The analysis of dioxins and related compounds

The analysis of polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, polychlorinated biphenyls, and other related compounds requires complex sample preparation and analytical procedures using highly sensitive and selective state-of-the-art instrumentation to meet very stringent data quality objectives. The analytical procedures (extraction, sample preparation), instrumentation (chromatographic separation and detection by mass spectrometry) and screening techniques for the determination of dioxins, furans, dioxin-like polychlorinated biphenyls and related compounds with a focus on new approaches and alternate techniques to standard regulatory methods are reviewed.

Serum concentrations of chlorinated dibenzo-p-dioxins and dibenzofurans among former New Zealand trichlorophenol workers

This study examined serum levels of 2,3,7,8-substituted chlorinated dioxins and furans, and 15 PCBs for 346 New Zealand employees who worked at a site that manufactured 2,4,5-trichlorophenol (TCP) and 2,4,5-trichlorophenoxy acetic acid (2,4,5-T). Participants with potential TCP or 2,4,5-T exposures had mean lipid-adjusted 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) levels of 9.9 ng kg(-1) lipid compared to 4.9 ng kg(-1) for workers with no exposure at the site. Among exposed workers, we found evidence of differences in 2,3,7,8-TCDD levels by department and duties. Workers involved in an accidental release had the highest mean 2,3,7,8-TCDD levels, 37.9 ng kg(-1), followed by workers in the trichlorophenol plant, 23.4 ng kg(-1). Workers with potential intermittent exposures to 2,3,7,8-TCDD in construction, maintenance, mechanics, and transport had 2,3,7,8-TCDD levels above New Zealand background levels of 3.9 ng kg(-1), indicating workplace exposures. Among participants with work history indicating no 2,3,7,8-TCDD exposures, we observed some individuals with 2,3,7,8-TCDD levels above background levels. However, in most cases, these workers reported workplace exposures not recorded on their work histories or held other jobs with the potential for 2,3,7,8-TCDD exposures outside the plant. All other dioxin, furan, and PCB levels were similar among the exposed and unexposed workers.