Matrix Normalized MALDI-TOF Quantification of a Fluorotelomer-Based Acrylate Polymer

The degradation of fluorotelomer-based acrylate polymers (FTACPs) has been hypothesized to serve as a source of the environmental contaminants, perfluoroalkyl carboxylates (PFCAs). Studies have relied on indirect measurement of presumed degradation products to evaluate the environmental fate of FTACPs; however, this approach leaves a degree of uncertainty. The present study describes the development of a quantitative matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry method as the first direct analysis method for FTACPs. The model FTACP used in this study was poly­(8:2 FTAC-<i>co</i>-HDA), a copolymer of 8:2 fluorotelomer acrylate (8:2 FTAC) and hexadecyl acrylate (HDA). Instead of relying on an internal standard polymer, the intensities of 40 poly­(8:2 FTAC-<i>co</i>-HDA) signals (911–4612 Da) were normalized to the signal intensity of a matrix-sodium cluster (659 Da). We termed this value the normalized polymer response (<i>P</i>_<i>N</i>). By using the same dithranol solution for the sample preparation of poly­(8:2 FTAC-<i>co</i>-HDA) standards, calibration curves with coefficient of determinations (<i>R</i>²) typically >0.98 were produced. When poly­(8:2 FTAC-<i>co</i>-HDA) samples were prepared with the same dithranol solution as the poly­(8:2 FTAC-<i>co</i>-HDA) standards, quantification to within 25% of the theoretical concentration was achieved. This approach minimized the sample-to-sample variability that typically plagues MALDI-TOF, and is the first method developed to directly quantify FTACPs

Electrochemical Oxidation of the Sulfide Ion in Synthetic Geothermal Brines in Batch Cells Using Coke Electrodes

The oxidation of the sulfide ion occurs efficiently in batch cells at massive coke electrodes. At all currents studied, the products included a low yield of elemental sulfur, which deposited on the anode; the yields of sulfate were also low, except at the highest current. The remaining products were soluble organosulfur species, indicating that the coke anodes acted sacrificially. The reaction displayed unusual kinetic behavior with respect to the disappearance of sulfide: a two-stage reaction was observed in which the loss of sulfide was faster in the early stages of reaction, while elemental sulfur deposited on the anode. A subsequent slower current-controlled reaction was associated with the formation of the remaining products

Industrial Coke as an Electrode Material for Environmental Remediation

Industrial coke was evaluated as a low-cost electrode material for environmental remediation, using the dye Orange II as an example substrate. Coke was used as massive pieces in batch cells or in the ground form for use in a packed-bed reactor. The loss of Orange II was faster when the supporting electrolyte contained chloride ion, and under these conditions the reaction involved hypochlorination. In the batch reactor, the current efficiency for mineralization was only modest (4−14%). In the packed-bed reactor, the loss of both starting material and intermediates was fastest at high current and low flow rate, and a near-quantitative current efficiency was achieved. The high current efficiency was explained by the greater surface area of the electrodes in the packed-bed reactor compared with the batch reactor, and better contact between the solution to be remediated and the coke particles. A drawback to the use of coke electrodes for the remediation of aqueous wastes is their tendency to increase the total organic carbon content of an aqueous solution, especially under anodic polarization

Investigating the Biodegradability of a Fluorotelomer-Based Acrylate Polymer in a Soil–Plant Microcosm by Indirect and Direct Analysis

Fluorotelomer-based acrylate polymers (FTACPs) are a class of side-chain fluorinated polymers used for a variety of commercial applications. The degradation of FTACPs through ester hydrolysis, cleavage of the polymer backbone, or both could serve as a significant source of perfluoroalkyl carboxylates (PFCAs). The biodegradation of FTACPs was evaluated in a soil–plant microcosm over 5.5 months in the absence/presence of wastewater treatment plant (WWTP) biosolids using a unique FTACP determined to be a homopolymer of 8:2 fluorotelomer acrylate (8:2 FTAC). Although structurally different from commercial FTACPs, the unique FTACP possesses 8:2 fluorotelomer side chain appendages bound to the polymer backbone via ester moieties. Liberation and subsequent biodegradation of the 8:2 fluorotelomer appendages was indirectly determined by monitoring for PFCAs of varying chain lengths (C6–C9) and known fluorotelomer intermediates by liquid chromatography tandem mass spectrometry (LC–MS/MS). A FTACP biodegradation half-life range of 8–111 years was inferred from the 8:2 fluorotelomer alcohol (8:2 FTOH) equivalent of the unique FTACP and the increase of degradation products. The progress of FTACP biodegradation was also directly monitored qualitatively using matrix-assisted laser desorption/ionization (MALDI-TOF) time-of-flight mass spectrometry. The combination of indirect and direct analysis indicated that the model FTACP biodegraded predominantly to perfluorooctanoate (PFOA) in soils and at a significantly higher rate in the presence of a plant and WWTP biosolids

Decades-Scale Degradation of Commercial, Side-Chain, Fluorotelomer-Based Polymers in Soils and Water

Fluorotelomer-based polymers (FTPs) are the primary product of the fluorotelomer industry. Here we report on a 376-day study of the degradability of two commercial acrylate-linked FTPs in four saturated soils and in water. Using an exhaustive serial extraction, we report GC/MS and LC/MS/MS results for 50 species including fluorotelomer alcohols and acids, and perfluorocarboxylates. Modeling of seven sampling rounds, each consisting of ≥5 replicate microcosm treatments, for one commercial FTP in one soil yielded half-life estimates of 65–112 years and, when the other commercial FTP and soils were evaluated, the estimated half-lives ranged from 33 to 112 years. Experimental controls, consisting of commercial FTP in water, degraded roughly at the same rate as in soil. A follow-up experiment, with commercial FTP in pH 10 water, degraded roughly 10-fold faster than the circum-neutral control suggesting that commercial FTPs can undergo OH^–-mediated hydrolysis. 8:2Fluorotelomer alcohol generated from FTP degradation in soil was more stable than without FTP present suggesting a clathrate guest–host association with the FTP. To our knowledge, these are the only degradability-test results for commercial FTPs that have been generated using exhaustive extraction procedures. They unambiguously show that commercial FTPs, the primary product of the fluorotelomer industry, are a source of fluorotelomer and perfluorinated compounds to the environment

<i>C</i>⁸‑Heteroaryl-2′-deoxyguanosine Adducts as Conformational Fluorescent Probes in the <i>Nar</i>I Recognition Sequence

The optical, redox, and electronic properties of <i>C</i>⁸-heteroaryl-2′-deoxyguanosine (dG) adducts with <i>C</i>⁸-substituents consisting of furyl (^FurdG), pyrrolyl (^PyrdG), thienyl (^ThdG), benzofuryl (^BfurdG), indolyl (^InddG), and benzothienyl (^BthdG) are described. These adducts behave as fluorescent nucleobase probes with emission maxima from 379 to 419 nm and fluorescence quantum yields (Φ_<i>fl</i>) in the 0.1–0.8 range in water at neutral pH. The probes exhibit quenched fluorescence with increased solvent viscosity and decreased solvent polarity. The ^FurdG, ^BfurdG, ^InddG, and ^BthdG derivatives were incorporated into the G₃ position of the 12-mer oligonucleotide 5′-CTCG₁G₂CG₃CCATC-3′ that contains the recognition sequence of the <i>Nar</i>I Type II restriction endonuclease. This sequence is widely used to study the biological activity (mutagenicity) of <i>C</i>⁸-arylamine–dG adducts with adduct conformation (<i>anti</i> vs <i>syn</i>) playing a critical role in the biological outcome. The modified <i>Nar</i>I­(X = ^FurG, ^IndG, ^BfurG, or ^BthG) oligonucleotides were hybridized to the complementary strand containing either C (<i>Nar</i>I′(C)) or G (<i>Nar</i>I′(G)) opposite the probe. The duplex structures were characterized by UV melting temperature analysis, fluorescence spectroscopy, collisional fluorescence quenching studies, and circular dichroism (CD). The emission of the probes showed sensitivity to the opposing base in the duplex, and suggested the utility of fluorescence spectroscopy to monitor probe conformation