We propose an instrumental method based on liquid chromatography coupled to negative ion-spray ionization (ISP(-)) tandem mass spectrometry (MS/MS), for the simultaneous analysis of eight hydroxylated brominated diphenyl ethers (OH-PBDEs) in four different environmental matrices (soil, fish, sludge and particulate matter). The reversed-phase chromatographic separation was performed on a 50 mm Xbridge C18 column, and the compounds were well resolved with a gradient consisting of a ternary mixture of 5 mMammonium acetate, methanol and acetonitrile. Detection was performed in the multiple reaction monitoring (MRM) mode using the [M - H](-) ion as base peak. The fragmentation pathways of the OH-PBDEs varied according to the hydroxyl substitution in the benzene rings and produced characteristic MRM transitions needed for resolving isomeric compounds. The method is acceptable for quantification in the high picogram per gram dry weight (dw) level for all matrices analyzed. Repeatability and reproducibility tested at 75 pg microl(-1) were below 10% using internal standard quantification. The ISP (-) enhancement due to matrix effects was in the 76-132% range and the highest values corresponded to sludge samples. The use of the proposed method based on LC-ISP(-)-MS/MS opens a new way to directly determine OH-PBDEs without the need of derivatization.

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Amiloride photostability at different pH values was studied in depth by applying Multivariate Curve Resolution Alternating Least Squares (MCR-ALS) to the UV spectrophotometric data from drug solutions exposed to stressing irradiation. Resolution of all degradation photoproducts was possible by simultaneous spectrophotometric analysis of kinetic photodegradation and acid-base titration experiments. Amiloride photodegradation showed to be strongly dependent on pH. Two hard modelling constraints were sequentially used in MCR-ALS for the unambiguous resolution of all the species involved in the photodegradation process. An amiloride acid-base system was defined by using the equilibrium constraint, and the photodegradation pathway was modelled taking into account the kinetic constraint. The simultaneous analysis of photodegradation and titration experiments revealed the presence of eight different species, which were differently distributed according to pH and time. Concentration profiles of all the species as well as their pure spectra were resolved and kinetic rate constants were estimated. The values of rate constants changed with pH and under alkaline conditions the degradation pathway and photoproducts also changed. These results were compared to those obtained by LC-MS analysis from drug photodegradation experiments. MS analysis allowed the identification of up to five species and showed the simultaneous presence of more than one acid-base equilibrium.