High Resolution Mass Spectrometry of Polyfluorinated Polyether-Based Formulation

High resolution mass spectrometry (HRMS) was successfully applied to elucidate the structure of a polyfluorinated polyether (PFPE)-based formulation. The mass spectrum generated from direct injection into the MS was examined by identifying the different repeating units manually and with the aid of an instrument data processor. Highly accurate mass spectral data enabled the calculation of higher-order mass defects. The different plots of MW and the nth-order mass defects (up to n = 3) could aid in assessing the structure of the different repeating units and estimating their absolute and relative number per molecule. The three major repeating units were -C2H4O-, -C2F4O-, and -CF2O-. Tandem MS was used to identify the end groups that appeared to be phosphates, as well as the possible distribution of the repeating units. Reversed-phase HPLC separated of the polymer molecules on the basis of number of nonpolar repeating units. The elucidated structure resembles the structure in the published manufacturer technical data. This analytical approach to the characterization of a PFPE-based formulation can serve as a guide in analyzing not just other PFPE-based formulations but also other fluorinated and non-fluorinated polymers. The information from MS is essential in studying the physico-chemical properties of PFPEs and can help in assessing the risks they pose to the environment and to human health

Characterization of 3‑Aminopropyl Oligosilsesquioxane

The synthesis routes in the production of polysilsesquioxanes have largely relied upon <i>in situ</i> formations. This perspective often leads to polymers in which their basic structures including molecular weight and functionality are unknown [Lichtenhan, J. D.; et al. Silsesquioxane-siloxane copolymers from polyhedral silsesquioxanes Macromolecules, 1993, 26, 2141−2142, http://dx.doi.org/10.1021/ma0060a053]. For a better understanding of the polysilsesquioxane properties and applications, there is a need to develop more techniques to enable their chemical characterization. An innovative method was developed to determine the molecular weight distribution (MWD) of an oligosilsesquioxane synthesized in-house from (3-aminopropyl)­triethoxysilane. This method, which can be applied to other silsesquioxanes, siloxanes, and similar oligomers and polymers, involved separation using high performance liquid chromatography (HPLC) and detection using mass spectrometry (MS) with electrospray ionization (ESI). The novelty of the method lies on the unique determination of the absolute concentrations of the individual homologues present in the sample formulation. The use of absolute concentrations is necessary in estimating the MWD of the formulation when relative percentage, which is based solely on mass spectral ion intensities, becomes irrelevant due to the disproportionate response factors of the homologues. Determination of absolute concentration requires the use of single-homologue calibration standards. Because of commercial unavailability, these standards were prepared by efficient fractionation of the original formulation

Microextraction of polychlorinated biphenyls (PCBS) from soil samples

The standard method of polychlorinated biphenyl (PCB) analysis in soil samples requires Soxhlet extraction of gram amount of sample, considerable amounts of hazardous solvents, and a clean-up and extraction time of 3 days per sample. An efficient microextraction procedure has been developed for the trace quantitative analysis of PCBs in soil samples that will only necessitate a small fraction of the Soxhlet extraction requirements ad still achieve good recoveries for PCB congeners. The microextrcation procedures requires only 0.1g amount of sample and is relatively inexpensive extraction technique, which can be completed within 18 hours. The technique uses standard glassware and only minimal amount of solvent. In this work, parameters such as the type and amount of extracting solvent were evaluated. The congener-specific recoveries of the 20 target PCBs were compared using hexane and heptane as extracting solvents. When compared to the certified concentrations of the 20 congeners in the soil standard reference material (SRM) from the National Institute of Standards and Technology (NIST), the proposed microextraction method using heptane showed excellent recoveries for 10 of the congeners. The other 10 target congeners were found with other PCB congeners or contaminants. Moreover, the recoveries of the 2 surrogate internal standards, PCB #30 and 112, were also within the acceptable limit of ±30% even at 25 ng/g

Trace organic chemical pollutants from the lake waters of San Pablo City, Philippines by targeted and non-targeted analysis

More than half of the freshwater lakes in the Philippines are small with surface areas of \u3c2 km2. The dynamics in these lakes are different from those in the bigger lakes. This study was conducted to determine the organic pollutants and their sources in three of the seven lakes of San Pablo City in Laguna, Philippines: lakes Palakpakin, Sampaloc, and Pandin. Gas Chromatography-Mass Spectrometry (GC–MS) and Liquid Chromatography - Tandem Mass Spectrometry (LC-MS/MS) were used in the targeted and non-targeted analysis of the lake water samples. The three lakes are all volcanic crater lakes but are exposed to different anthropogenic activities, which includes domestic activities, livelihood (farming and aquaculture) and eco-tourism. Due to the presence of rice fields and fruit plantations, chlorpyrifos was detected in the three lakes while other pesticides like cypermethrin, picolinafen and quinoxyfen were additionally found in Lake Sampaloc, which is the biggest of the three lakes and located within the urbanized section of the city. Traces of different surfactants (linear alkylbenzene sulfonates, secondary alkyl sulfonates, alkyl sulfates, alkyl ether sulfates), biocide benzalkonium chloride, insect repellent diethyltoluamide, antibiotics (sulfadiazine and sulfamethoxazole), hypertension drug telmisartan, phosphate-based fire retardants, and artificial sweeteners (acesulfame, cyclamate, saccharin and sucralose) were detected in lakes Sampaloc and Palakpakin. The same surfactants, artificial sweeteners, insect repellant and phosphate-based fire retardants were also found in Lake Pandin, which is mainly used for eco-tourism activities like swimming and boating. The results of this study suggest that the organic pollutants present in the small lakes can be linked to the various human activities in the immediate lake environment. Because small lakes are more prone to environmental stresses, human activities in the said lakes must be regulated to ensure sustainable development