Identifying an unknown compound in flue gas of semiconductor industry - Forensics of a perfluorocarbon.

This study investigated the source of a false positive signal in the measurement of total non-methane organic compounds (TNMOCs) by an on-line analyzer based on flame ionization detection (FID) in the flue gas released from a semiconductor fabrication plant. Since no release of volatile organic compounds (VOCs) into the waste gas stream in acid/base ventilation was assured by the plant authority, the positive detection of VOCs became a subject of dispute. In addition to the TNMOC analysis of 5 samples, the investigation used the method that coupled thermal desorption (TD) with gas chromatography mass spectrometry (GC/MS), dubbed TD-GC/MS, to identify the substance that produced the FID signals of TNMOCs. The waste gas was collected with sampling canisters and analyzed by in-laboratory TD-GC/MS. However, mass scanning from 45 to 250 m/z to remove interference from air matrix of O2, N2 and CO2 forbid detecting any ion fragments smaller than 45 m/z and, thus, led to poor match in mass (MS) library search. As a result, a highly retentive porous layer open tubular (PLOT) capillary column was employed to separate the unknown away from the air peak. The success of acquiring all key ion fragments of 31, 50, 69, and 131 m/z resulted in an excellent match with octafluorocyclobutane (C4F8) in the NIST database. A gas standard was then prepared and injected to confirm the identity of C4F8 by the identical mass spectrum and GC retention time. The concentrations of C4F8 found in the 5 flue gas samples varying from 3.32 to 6.21 ppmv were very close to the NMOC range of 3.48-6.62 ppmv as reported by the TNMOC analyzer, proving that the FID signals observed from TNMOC method were mostly produced from C4F8. Consequently, the method of TD-GC/MS would be an ideal method to pre-screen the presence of PFCs before a non-distinguishable TNMOC analyzer is applied to approximate the VOC level as part of the integrated effort to monitor VOC in flue gas.

Anti-angiogenic activity of Gracilaria coronopifolia J.G. Agardh extract by lowering the levels of trace metals (iron, zinc and copper) in duck chorioallantoic membrane and in vitro activation of AMP-kinase.

AMP-activated protein kinase (AMPK) is an intracellular energy sensor important in metabolic regulation, cell growth, and survival. However, the specific role of AMPK signaling pathway in the inhibition of angiogenesis remains unclear. The study highlights the activity on AMP activated protein kinase signaling pathways of a marine algae, Gracilaria coronopifolia, and its effects on angiogenesis. It was found that the most potent extract, GCD, inhibited angiogenesis significantly in the duck chorioallantoic membrane assay and also activated the enzyme AMP-kinase, in vitro. The dichloromethane extract was found most active in inhibiting angiogenesis in the duck chorioallantoic membrane (IC50 = 1.21 µg/mL) followed by GCH (IC50 = 3.08 µg/mL) (p = 0.479) and GCM (IC50 = 8.93 µg/mL) (p = 0.042). Benferroni post hoc analysis revealed that there was no significant difference between the percent inhibitions of GCH and GCM extracts (p = 0.479). Consequently, angiogenic inhibition caused lowering of iron, zinc, and copper levels in the duck CAM. Thin layer chromatography and gas chromatography-mass spectrometry revealed the components of each extracts. Notably, this is the first report on the kinase activity of a red algae G. coronopifolia extracts and a colorimetric-based quantification of angiogenesis based on metal content of CAM. Our data also suggest a novel therapeutic approach for inhibiting angiogenesis through the AMPK pathway.

Degradation of lindane and hexachlorobenzene in supercritical carbon dioxide using palladium nanoparticles stabilized in microcellular high-density polyethylene.

Palladium nanoparticles stabilized in microcellular high-density polyethylene prepared through supercritical foaming, supercritical impregnation, and H2 reduction are used for the hydrodechlorination of lindane and hexachlorobenzene in supercritical carbon dioxide below 100 °C. Both lindane and hexachlorobenzene can be almost 100% transformed to cyclohexane in 1 h. Reaction intermediates, such as lower chlorinated products or benzene, are not observed or exist in trace amount indicating that most of them may undergo reactions without leaving the metal surface.

Simultaneous speciation of iron(II) and iron(III) by ion chromatography with chemiluminescence detection.

This study reports on a method for the speciation of iron in aqueous samples by the simultaneous analysis of divalent and trivalent iron ions with ion chromatography equipped with chemiluminescence detection (IC-CLD). Ferrous and ferric ions are first chelated by pyridine-2,6-dicarboxylic acid (PDCA) to form complexed anions, and separated by a mixed-bed ion-exchange column. The separated complexed ions are then detected with a CLD system containing luminol and hydrogen peroxide in a basic solution. This luminescence system has a linear dynamic range of ca. 3 orders of magnitude, with method detection limits as low as 7 µg L(-1) for Fe(II) and 3 µg L(-1) for Fe(III), measured in the simultaneous detection mode. This system resists interferences from common cations such as Cd, Ca, Cr, Cu, Mg, Ni, Pb, and Zn. Evaluation by analyzing real samples shows that this method is rapid, accurate, sensitive, and selective.

Removing perfluorooctane sulfonate and perfluorooctanoic acid from solid matrices, paper, fabrics, and sand by mineral acid suppression and supercritical carbon dioxide extraction.

The removal of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) from solid matrices has received considerable attention because of the environmental persistence, bioaccumulation, and potential toxicity of these compounds. This study presents a simple method using concentrated HNO(3) as a suppression agent, and methanol-modified supercritical carbon dioxide (Sc-CO(2)) extraction for removing PFOS and PFOA from solid matrices. The optimal conditions were 16 M HNO(3) and 20% (v/v) methanol containing Sc-CO(2), under a pressure of 20.3 MPa and a temperature of 50 °C. Extraction time was set at 70 min (40 min for static and 30 min for dynamic extraction). PFOA and PFOS were identified and quantitated by liquid chromatography/mass spectrometry. The extraction efficiencies (with double extractions) were close to 100% for PFOA and 80% for PFOS for both paper and fabric matrices. The extraction efficiencies for sand were approximately 77% for PFOA and 59% for PFOS. The results show that this method is accurate, and effective, and that it provides a promising and convenient approach to remediate the environment of hazardous PFOA and PFOS contamination.

Determination of polybrominated diphenyl ethers (PBDEs) in fish samples from rivers and estuaries in Taiwan.

Polybrominated diphenyl ethers (PBDEs) have been used extensively over the past two decades as flame retardants in many types of polymers, and have been found to be a class of contaminants of concern. Measurements of PBDEs in various environmental matrices from Sweden, Holland, Japan, North America, and elsewhere have been reported. We report data of PBDEs in fish samples taken from six rivers and three estuaries in Taiwan. Seven PBDE congeners were observed in all sixty samples. BDE-47 was found to be the dominant congener in all waters, and BDE-154 contributed more than BDE-99 and BDE-100. Nonetheless, BDE-154 and BDE-183 were the predominant congeners in some species studied. These results are somewhat different from those from other countries, where the pattern is typically BDE-47 > 99 >100 >154, 153, and is postulated to be due to the extensive use of octa-BDE rather than penta-BDE in Taiwan. The average concentration distribution across all samples of the sum of PBDE congeners ranged from 30.6 ng/g lipid to 281 ng/g lipid. The concentrations of PBDEs in fishes reported here are higher than those reported from European countries, but lower than those from the United States.

Dry ice-originated supercritical and liquid carbon dioxide extraction of organic pollutants from environmental samples.

Packed in a high-pressure vessel and under calculated conditions, dry ice can be used as a source of carbon dioxide for supercritical CO(2) extraction or liquid CO(2) of organic compounds from environmental samples. Coupled with a fluid modifier such as toluene, dry ice-originated supercritical CO(2) (Sc CO(2)) achieves quantitative extraction of many volatile organic compounds (VOCs) and semivolatile organic compounds (SOCs) including polycyclic aromatic hydrocarbons (PAHs), n-alkanes, and polychlorinated biphenyls (PCBs) from solid matrices. Compared to contemporary manual or automated supercritical fluid extraction (SFE) technologies, this novel technique simplifies SFE to a minimum requirement by eliminating the need of a high-pressure pump and any electrical peripherals associated with it. This technique is highly suitable to analytical areas where sample preservation is essential but difficult in the sampling field, or where sample collection, sample preparation, and analysis are to be done in the field.

Selective extraction of strontium with supercritical fluid carbon dioxide.

Strontium (Sr(2+)) can be selectively extracted from aqueous solutions into supercritical fluid CO(2) at 60 °C and 100 atm with dicyclohexano-18-crown-6 (DC18C6) using CF(3)(CF(2))(6)CO(2) (-) (PFOA(-)) or CF(3)(CF(2))(6)CF(2)SO(3) (-) (PFOSA(-)) as a counter anion; at a mole ratio of Sr(2+) : DC18C6 : PFOA(-) = 1:10:50, the extraction of Sr (5.6 × 10(-5) M) from water at pH 3 is near quantitative whereas Ca(2+) and Mg(2+) at equal concentration are only extracted to a level of 7 and 1%, respectively; PFOSA(-) is an effective counter anion for selective extraction of Sr(2+) from 1.3 M HNO(3) with DC18C6 in supercritical CO(2).