Mass spectrometry and scanning electron microscopy study of silicone tunneled dialysis catheter integrity after an exposure of 15 days to 60% ethanol solution.

Anti-infectious lock is an emerging therapeutic option for preventing and/or controlling catheter-associated infection. Ethanol has widespread bactericidal activity, limited side effects, and low risk of inducing antimicrobial resistance. However, concerns have been raised about ethanol-induced catheter structural degradation. In this study, silicone catheters were immersed at 37 degrees C in three different solvents: 0.9% sodium chloride, 60% ethanol, and 95% ethanol for 4 h, 15 days and 15 days after a first storage of 4 h. Scanning electron microscopy (magnification 1000-20 000 times) of the inner surface of the catheter revealed no damage to the lumen surfaces of catheters immersed in 95% ethanol for 15 days compared with the reference catheter. Gas chromatography/mass spectrometry (GC/MS) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) analysis of the storage solutions revealed a significant release of polydimethylsiloxanes having a number of dimethylsiloxane units lower than 30 in the 95% ethanol solution and a structure highly consistent with a cyclic structure. Most release occurred within the first 4 h of exposure. In contrast, there was no difference in the small amounts of silicone released in 0.9% sodium chloride as reference and 60% ethanol solution, whatever the exposure time. These results should allow the development of clinical trials to assess the efficacy of the 60% ethanol lock technique in preventing or controlling the infectious complications of silicone dialysis catheters.

Ion-pair reversed-phase liquid chromatography-electrospray mass spectrometry for the analysis of underivatized small peptides.

The single run analysis of 23 small peptides (principally glycyl and lysyl dipeptides) is performed by ion-pair reversed-phase liquid chromatography coupled with evaporative light scattering detection or electrospray (tandem) mass spectrometry. Several perfluorinated carboxylic acid homologues are evaluated with an octadecyl silica stationary phase (Supelcosil ABZ+ Plus). Among the perfluorocarboxylic acids tested the nonafluoropentanoic acid and the tridecafluoroheptanoic acid gave the best results. Special attention was paid to the separation of isomer/isobar dipeptides (e.g., Gly-Ile, Gly-Leu, Leu-Gly, as well as Gly-Gln, Gly-Lys, etc.) which is usually necessary in spite of the high specificity of mass spectrometry. Before LC-MS analysis, ion-spray fragmentation as well as optimization of MS parameters of the analysed peptides was investigated. The optimum collision energy of glysyl peptides, Ala-Gln, Asp-Asp and Asp-Asp-Asp (13-18 eV) was different from that of the lysyl peptides, Tyr-Glu and oxidised glutathione (25-32 eV). Limits of detection varied from 0.1 to 1.2 mg l(-1) for simple MS and 0.05 to 25 mg l(-1) for tandem MS.