Determination of amino acids by capillary electrophoresis-electrospray ionization-mass spectrometry: an evaluation of different protein hydrolysis procedures.

In this work, a CE equipment, online hyphenated to an IT MS analyzer by a linear sheath liquid interface promoting ESI, was used to develop a method for quantitative determination of amino acids. Under appropriate conditions (BGE composition, 0.8% HCOOH, 20% CH3OH; sheath liquid composition, 0.8% HCOOH, 60% methanol; V ESI, +4.50 kV), analytical curves of all amino acids from 3 to 80 mg/L were recorded presenting acceptable linearity (r >0.99). LODs in the range of 16-172 micromol/L were obtained. BSA, a model protein, was submitted to different hydrolysis procedures (classical acid and basic, and catalyzed by the H+ form of a cation exchanger resin) and its amino acid profiles determined. In general, the resin-mediated hydrolysis yields were overall similar or better than those obtained by classical acid or basic hydrolysis. The resulting experimental-to-theoretical BSA concentration ratios served as correction factors for the quantitation of amino acids in Brazil nut resin generated hydrolysates.

Performance of an ultraviolet light-emitting diode-induced fluorescence detector in capillary electrophoresis.

The performance of a fluorescence detector in capillary electrophoresis (CE) using a light-emitting diode (LED) as excitation source is reported. An ultraviolet LED pulsed at a repetition rate of 500 Hz, combined with a time-discrimination and averaging acquisition system, was used. Limits of detection of 3 and 18 fmoles (at a signal-to-noise ratio equal to 3) were achieved for fluorescamine-derivatized bradykinin and lysine, respectively. This system exhibited a linear response for a concentration range between 54 and 417 microM for derivatized lysine, and between 1.81 and 23.58 microM for derivatized bradykinin. This detection system showed to be very convenient for routine analytical applications.

Use of capillary electrophoresis in the characterization of sulfonated metallophthalocyanines: a comparative evaluation of purification procedures following synthesis by the condensation method.

Capillary electrophoresis has been presented as a resourceful technique for monitoring the purity of synthetic metallophthalocyanines and evaluating comparatively purification procedures. In this study, the tetrasulfonated cobalt(II) phthalocyanine was synthesized by the condensation method and submitted to several purification procedures such as continuous Soxhlet extraction with ethanol and dioxane, percolation through a gel-filled chromatographic column, and salting-out precipitation in acid medium followed by washing with alkaline solution. The efficiency of each procedure, or combined procedures, was then evaluated by capillary electrophoresis in citrate buffer solution under constant voltage conditions and direct UV-VIS detection at 630 nm and 260 nm. The inorganic anion and cation composition of the purified fractions was also investigated by indirect UV analysis in chromate/cetyltrimethylammonium bromide (CTAB) and imidazole/hydroxyisobutyric acid (HIBA) electrolyte systems, at 254 nm and 214 nm, respectively. The electropherograms obtained at 630 nm showed a high-intensity peak surrounded by satellite peaks of small intensity with migration time of approximately 5-6 min. This profile is indicative of the formation of positional isomers under the synthesis conditions. The electropherograms obtained at 260 nm were useful to monitor contaminants, such as reaction by-products or unreacted starting materials. The salting-out precipitation of the crude product led to a good-quality product with 80% purity (elemental analysis based on nitrogen content), which is comparable to the purity of commercially available tetrasulfonated derivatives. Both UV and infrared (IR) spectra of the purified product resemble that of standards. The capillary electrophoresis ion analysis of the treated product revealed the presence of sodium carbonate as the major contaminant. The combined treatment of salting-out precipitation followed by percolation in a Sephadex column (Pharmacia, São Paulo, Brazil) was successful for the removal of carbonate ion. However, the percolation procedure seemed to cause minor demetallation of the macrocycle ring, as confirmed by the presence of free cobalt(II) in the electropherogram of the column eluted fraction.

Capillary electrophoresis-laser-induced fluorescence detection of amphetamine in the brain.

Prefrontal cortex microdialysis was done in rats that had received intraperitoneal amphetamine (AMPH). Samples were derivatized with 10(-4) M fluorescein isothiocyanate and incubated for 18 h. AMPH was separated by capillary electrophoresis (CE) and detected by laser-induced fluorescence detection (LIFD) from 30 to 150 min after injection. The limit of mass detection was 3 amol, which is three orders of magnitude lower than that in gas chromatography-mass spectrometry, and the limit of concentration detection was 3 x 10(-9) M. The results showed that CE-LIFD is a good method for detecting AMPH in brain dialysates of rats.