Nora M. Vizioli

Study of peptide–ligand interactions in open‐tubular capillary columns covalently modified with porphyrins

The inner surface of fused silica capillaries has been covalently modified with different porphyrins (deuteroporphyrin, complexes of deuteroporphyrin with metal ions Fe(III), Cu(II), Zn(II), Ni(II), and Cu(II)–meso–tetra (carboxyphenyl) porphyrin) and it was applied for the separation of biologically active peptides by open‐tubular capillary electrochromatography. Separations were performed in a mobile phase composed of 25 mM potassium phosphate, pH 4.0, 5% v/v ACN and 10 mM hydroquinone. Changes in the effective electrophoretic mobility of peptides were studied concerning porphyrin central metal atom, attachment geometry, and the presence of coordinating or aromatic amino acid residues in the peptide sequence. The results showed that differences in metal core on the porphyrin and the spatial conformation of attached porphyrin result in changes in the analyte interaction with the stationary phase.

On-line solid phase extraction CZE for the simultaneous determination of lanthanum and gadolinium at picogram per liter levels.

A non‐specific on‐line method is presented for the extraction and preconcentration of two rare earth elements using a microcartridge containing C18‐derivatized silica particles prior to their analysis by CZE. The microcartridge, named analyte concentrator, was coupled on‐line to the inlet of the separation capillary (fused‐silica (FS) capillary, 75 μm id ×12 cm from the inlet to the microcartidge and 37 cm from the microcartridge to the detector). The reversed‐phase sorbent quantitatively retained gadolinium (Gd) and lanthanum (La) as 2‐(5‐bromo‐2‐pyridylazo)‐5‐diethylaminophenol complexes in the presence of non‐ionic micelles of polyethylene glycol tert‐octylphenyl ether, enabling sample clean‐up and concentration enhancement with minimum sample handling. The rare earth elements chelates were released from the sorbent with methanol and then analyzed by CZE with diode array detection. A background electrolyte of 20 mM sodium tetraborate containing 8% ACN, pH 9.0, was found to be optimal for the separation of metal chelates. The concentration limits of detection were lowered to picogram per liter levels (20 pg/L for La and 80 pg/L for Gd). A 1000‐fold improvement in concentration sensitivity for La‐ and Gd‐2‐(5‐bromo‐2‐pyridylazo)‐5‐diethylaminophenol complexes with respect to CZE without preconcentration was reached.

A rapid and simple method for the determination of psychoactive alkaloids by CE-UV: application to Peganum Harmala seed infusions.

The β-carboline alkaloids of the harmala (HAlks) group are compounds widely spread in many natural sources, but found at relatively high levels in some specific plants like Peganum harmala (Syrian rue) or Banisteriopsis caapi. HAlks are a reversible Mono Amino Oxidase type A Inhibitor (MAOI) and, as a consequence, these plants or their extracts can be used to produce psychotropic effects when are combined with psychotropic drugs based on amino groups. Since the occurrence and the levels of the HAlks in natural sources are subject to significant variability, more widespread use is not clinical but recreational or ritual, for example B. caapi is a known part of the Ayahuasca ritual mixture. The lack of simple methods to control the variable levels of these compounds in natural sources restricts the possibilities to dose in strict quantities and, as a consequence, limits its use with pharmacological or clinical purposes. In this work, we present a fast, simple, and robust method of quantifying simultaneously the six HAlks more frequently found in plants, i.e., harmine, harmaline, harmol, harmalol, harmane, and norharmane, by capillary electrophoresis instruments equipped with the more common detector UV. The method is applied to analyze these HAlks in P. Harmala seeds infusion which is a frequent intake form for these HAlks. The method is validated in three different instruments in order to evaluate the transferability and to compare the performances between them. In this case, harmaline, harmine, and harmol were found in the infusion samples. Copyright

Separation of peptides by open‐tubular capillary electrochromatography using Fe(III)‐deuteroporphyrin as a covalently attached stationary phase

The separation of seven biologically active peptides was attempted by open‐tubular capillary electrochromatography in fused‐silica capillaries chemically modified with iron (III)‐deuteroporphyrin using UV‐absorption detection at 214 nm. The effect of BGE pH and content of organic solvent modifier was investigated. The best separations were obtained in 25 mM phosphate (BGE), pH 4.0, containing 5% v/v ACN and 10 mM hydroquinone, which was added to prevent gas bubble formation. Considering the method sensitivity, lower concentration LODs were obtained for all peptides in their open‐tubular capillary electrochromatography separation as compared with their CZE separation in bare fused‐silica capillary. The iron (III)‐deuteroporphyrin column proved to be highly stable over time and showed acceptable precision of migration times and corrected peak areas (RSD in the range 2–4%).