Complementary mass spectrometric approaches and scanning electron microscopy to study the structural stability of polyurethane tunneled dialysis catheters after exposure to ethanol solutions.

RATIONALE: Ethanol lock is an emerging therapeutic option for preventing and/or controlling catheter-associated infection. A previous study of silicone catheters showed they underwent no polymer degradation when kept in 60% ethanol for 15 days at 37 °C. The stability of the more widely used polyurethane catheters was studied here in the same way. METHODS: A qualitative and quantitative study of the stability of Carbothane® catheters was performed following their immersion at 37 °C in different solvents (0.9% sodium chloride as control medium and 40%, 60%, 95% ethanol solutions) for different periods of time (from 5 min to 15 days) using scanning electron microscopy and complementary mass spectrometry techniques. RESULTS: Electron ionization analysis of the 95% ethanol storage solutions revealed the release of about 45 products (8 of which were major) subdivided into two groups according to their fragmentation patterns. Combining all the mass spectrometric data made it possible to propose structures. Group I (major) originated from the polycarbonate diol component (soft segment) and group II (minor) from the dicyclohexylmethane-4,4'-diisocyanate component (rigid segment). Semi-quantitative gas chromatography/mass spectrometry (GC/MS) analysis showed that no significantly higher release was observed after immersion for 30 min at 37 °C in 40% ethanol (mean ratio = 0.677 ± 0.068) than after immersion in reference 0.9% sodium chloride solution for 15 days (0.837 ± 0.127). CONCLUSIONS: A 30 min-40% (v/v) ethanol solution can be considered as safe for preventing the infectious complications of Carbothane® dialysis catheters, and a 30 min-60% (v/v) ethanol treatment can be occasionally used to eradicate established biofilm.

Mechanism of enzymatic degradation of the azo dye Orange II determined by ex situ 1H nuclear magnetic resonance and electrospray ionization-ion trap mass spectrometry.

Removal of azo dye effluents generated by textile photography industries is a main issue in wastewater treatment. Enzymatic treatment of dyes appears to be one of the most efficient processes for their degradation. The elucidation of degradation pathways is of special interest considering health and environmental priorities. Ex situ nuclear magnetic resonance (NMR) spectroscopy and electrospray ionization (ESI)-ion trap mass spectrometry performed directly on incubation medium have been used for the first time to follow kinetics of sulfonated azo dye Orange II enzymatic degradation. Nine transformation products were identified using these complementary analyses performed ex situ without any prior treatment. Three types of cleavage are proposed for the degradation pathway: (i) a symmetrical splitting of the azo linkage that leads to the formation of 4-aminobenzenesulfonate (and 1-amino-2-naphthol, not detected); (ii) an asymmetrical cleavage on the naphthalene side that generates 1,2-naphthoquinone and 4-diazoniumbenzenesulfonate as products, with the latter one being transformed into 4-hydroxybenzensulfonate; and (iii) a third degradation pathway that leads to 2-naphthol and 4-hydroxybenzenesulfonate. Moreover, three other intermediates have been identified. This study, which constitutes the first concomitant use of (1)H NMR spectroscopy and ESI-ion trap mass spectrometry in this field, illustrates the indubitable interest of the ex situ approach.