ascorbic-acid and hydromethylthionine

A capillary electrophoresis method for the determination of the dye methylene blue (tetramethylthionine, MB) in human urine depending on liquid/liquid-extraction and diode array detection has been developed, validated, and applied to samples of healthy individuals, who had been dosed with methylene blue within clinical studies. After extraction with dichloromethane and sodium hexanesulfonate, sample extracts were measured on an extended light path capillary. The dye was detected simultaneously at 292 and 592 nm using methylene violet 3 RAX as internal standard. The limit of quantification was 1.0 microg/ml. The accuracy of the method varied between -15.2 and +0.8% and the precision ranged from 2.0 to 12.0%. The method was linear at least within 1.0 and 60 microg/ml. In contrast to earlier indirect determinations no leuco methylene blue (LMB) was directly detected in urine, whereas in aqueous test solutions containing surplus amounts of ascorbic acid leuco methylene blue was well separated from MB in a single run.

Topics: Ascorbic Acid; Calibration; Chromatography, Micellar Electrokinetic Capillary; Electrophoresis, Capillary; Humans; Methylene Blue; Oxidation-Reduction; Sensitivity and Specificity; Spectrometry, Mass, Electrospray Ionization; Urine

The kinetics of methylene blue reduction by ascorbic acid in acetonitrile was investigated by cavity ring-down spectroscopy. Because of our high sensitivity we were able to use very low concentrations (1-10 nM) of the dye. Under these conditions, we observed a second-order loss of dye as well as a competing back reaction with dissolved oxygen. The use of an inexpensive diode laser and a relatively simple setup should make ultratrace kinetic studies more accessible.

Topics: Acetonitriles; Ascorbic Acid; Kinetics; Lasers; Methylene Blue; Optics and Photonics; Oxidation-Reduction; Sensitivity and Specificity; Spectrum Analysis

Identification and preservation of the facial nerve during extirpative and reconstructive surgery represents a challenge even for the experienced surgeon. We present an experimental intraoperative technique for staining the facial nerve and its branches that is safe, accurate, and inexpensive. Leucomethylene blue is injected into the precise region of the facial nerve. Staining of the surrounding tissues is efficiently reduced by irrigation with ascorbic acid solution, leaving only the facial nerve stained. This technique has been encouraging in rabbits, and with additional experience, we anticipate its use for intraoperative staining of the facial nerve in humans.

Topics: Animals; Ascorbic Acid; Facial Nerve; Facial Nerve Injuries; Intraoperative Period; Methylene Blue; Models, Biological; Rabbits; Staining and Labeling; Surgery, Plastic; Therapeutic Irrigation; Time Factors