Analysis of perfluorinated compounds in sewage sludge by pressurized solvent extraction followed by liquid chromatography-mass spectrometry

Perfluorinated compounds (PFCs) are widely used in everyday life and one of the main recipients of these compounds is waste water treatment plants (WWTPs). Due to the structure and physicochemical properties of PFCs, these compounds could be redistributed from influent water to sludge. This work reports a new validated protocol for the analysis of 13 perfluorinated acids, 4 perfluorosulfonates and the perfluorooctanesulfonamide. The present work has been focused to develop a sensitive and robust method for the analysis of 18 PFCs in sewage sludge, based on pressurized solvent extraction (PSE) followed by solid phase extraction (SPE) clean-up, analytes separation by liquid chromatography and analysis in a hybrid quadrupole-linear ion trap mass spectrometer (LC-QLiT-MS/MS) working in single reaction monitoring (SRM) mode. The final methodology was validated using a blank sewage sludge fortified at different concentration levels. The method limits of detection were ranging in general from 15 to 79 ng/kg. These values were comparable to the decision limit (CCα) and the detection capability (CCβ), which were 17-1134 ng/kg and 18-1347 ng/kg, respectively. The percentage of recovery was from 79 to 111% in the most cases at different spiked levels. Finally, the repeatability of the method was in the range 4% (PFOS and PFOA) to 25% (RSD %). In order to evaluate the applicability of the method, 5 sludge samples were analyzed. The results showed that the 18 PFCs were present in all samples. However, the concentrations for most of them were below the limits of quantification. The compound present at higher concentrations was perfluorooctanesulfonate (PFOS), which was in concentrations from 53.0 to 121.1 μg/kg. The other PFCs were at concentrations between 0.3 and 30.3 μg/kg.     

Liquid chromatography-tandem mass spectrometric analysis and regulatory issues of polar pesticides in natural and treated waters

Pesticides are among the most detected contaminants in the aquatic environment. This is mainly due to their use in agriculture and their physico-chemical properties that enable transportation and a persistent or pseudo-persistent existence in the water media. Several directives and guidelines set maximum levels of pesticides in water in order to protect the human and environmental health. A brief discussion of the existing directives and guidelines concerning pesticides in water is presented, e.g., the new regulatory framework for the Registration, Evaluation and Authorisation of Chemicals (REACH), and the Directive 91/414/EEC concerning the placing of plant protection products on the market. Up-to-date analytical tools to support the REACH program are of prime importance to ensure its complete implementation. Since liquid chromatography (LC) coupled to mass spectrometry (MS) is considered the most appropriate technique for determination of most modern pesticides in environmental waters, the most recent developments and applications in this field are discussed in detail in this review.     

Solid phase extraction of Pb(II) in water samples using a new hybrid inorganic-organic mesoporous silica prior to its determination by FAAS

A mesoporous silica has been chemically modified with 5-mercapto-1-methyltetrazole. The newly synthesized material was characterized by powder X-ray diffraction, N₂ adsorption, FT-IR, ¹³C-NMR spectroscopy and elemental analysis, and used to preconcentrate Pb(II) from aqueous solutions. The effect of several variables on the adsorption capacity (i.e. stirring time, pH, interfering ions, presence of other heavy metals in the medium, etc.) has been studied using batch and column techniques. The adsorption capacity of the material followed the order: Pb(II) >> Cu(II) > Cd(II) >>Mn(II) > Ni(II) > Co(II). In column experiments a pre-concentration factor of 200 was obtained for Pb(II). Spiked tap water, mineral water and river water were used for the preconcentration and determination of Pb(II) by flame atomic absorption spectrometry, and a 101–103% recovery was obtained. The limit of detection and quantification values of the method were found to be 2.22·10^?6 mM and 8.20·10^?6 mM, respectively. The relative standard deviation for four preconcentration experiments was found to be ≤9% in all cases.     

On local convergence of sequential quadratically-constrained quadratic-programming type methods,with an extension to variational problems

We consider the class of quadratically-constrained quadratic-programming methods in the framework extended from optimization to more general variational problems. Previously, in the optimization case, Anitescu (SIAM J. Optim. 12, 949–978, 2002) showed superlinear convergence of the primal sequence under the Mangasarian-Fromovitz constraint qualification and the quadratic growth condition. Quadratic convergence of the primal-dual sequence was established by Fukushima, Luo and Tseng (SIAM J. Optim. 13, 1098–1119, 2003) under the assumption of convexity, the Slater constraint qualification, and a strong second-order sufficient condition. We obtain a new local convergence result, which complements the above (it is neither stronger nor weaker): we prove primal-dual quadratic convergence under the linear independence constraint qualification, strict complementarity, and a second-order sufficiency condition. Additionally, our results apply to variational problems beyond the optimization case. Finally, we provide a necessary and sufficient condition for superlinear convergence of the primal sequence under a Dennis-Moré type condition. Research of the second author is partially supported by CNPq Grants 300734/95-6 and 471780/2003-0, by PRONEX–Optimization, and by FAPERJ.     

Simultaneous determination of hexabromocyclododecane, tetrabromobisphenol A, and related compounds in sewage sludge and sediment samples from Ebro River basin (Spain)

This paper describes the development of a methodology for the simultaneous determination and quantification of hexabromocyclododecane (HBCD), tetrabromobisphenol A (TBBPA), and related compounds (bisphenol A, monobromobisphenol A, dibromobisphenol A, and tribromobisphenol A) in sludge and sediment samples. The selected method is based on an extraction with dichloromethane: methanol followed by purification via SPE C₁₈ cartridges. Instrumental determination was carried out by liquid chromatography–quadrupole linear ion trap mass spectrometry (LC-QqLIT-MS), with quantification based on isotopic dilution method. Analyte recoveries were in the range of 39–120% and 88–126% for spiked sewage and sediment, respectively. Repeatability of replicate extractions was better than 13% relative standard deviation. Linearity was checked in the range of 0.05 and 25 injected nanograms. Limits of detection (LODs) and limits of quantification (LOQs) were in the range of 0.6 and 2.7 ng/g and 1.4 and 66 ng/g for sediment and sludge samples, respectively. The developed method was applied to sewage sludge and sediment samples collected along the Ebro River and Cinca River, one of its tributaries (northeast of Spain). TBBPA levels in sewage sludge ranged from not quantified to 1,329 ng/g dw, whereas levels in sediment samples were lower, between not detected and 15 ng/g dw. As regards HBCD, concentrations were between not detected and 375 ng/g for sludge samples and 0.8 and 1850 ng/g for sediments.     

On Jacobi fields

We define curves on a Riemannian manifold as integrals of generalized Jacobi fields. We show that the force term that deviates the trajectory from the geodesic motion can be constructed as a functional of the metric tensor. These curves can be interpreted as particles (observers) coupled nonminimally with gravitation that can provide a class of residual observers for the inevitable singularity—as shown in the text.This essay received an honorable mention (1976) from the Gravity Research Foundation-Ed.     

Homoclinic phenomena in the gravitational collapse

A class of Bianchi IX cosmological models is shown to have chaotic gravitational collapse, due to Poincaré's homoclinic phenomena. We can program such models so that for any given positive integer N (N=∞ included) the universe undergoes N non-periodic oscillations (each oscillation requiring a long time) before collapsing. For N=∞ the universe undergoes periodic oscillations.     

Multi-residue analytical methods using LC-tandem MS for the determination of pharmaceuticals in environmental and wastewater samples: a review

Multi-residue analytical methodologies are becoming the preferred and required tools against single group analysis, as they provide wider knowledge about the occurrence of pharmaceuticals in the environment necessary for further study of their removal, partition and ultimate fate. However, simultaneous analysis of compounds from different groups with quite different physico-chemical characteristics requires a compromise in the selection of experimental conditions, which in some cases are not the best conditions for all the analytes studied. In this article, an overview of analytical methodologies focusing on the simultaneous determination of acidic, neutral and basic compounds belonging to different therapeutical classes is presented. The state-of-the-art of LC-MS/MS for multi-class analysis is reviewed, highlighting the specific requirements for such analysis.