RESUMO
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.
Assuntos
Aminoácidos/análise , Eletroforese Capilar/métodos , Proteínas/química , Espectrometria de Massas por Ionização por Electrospray/métodos , Aminoácidos/normas , Animais , Bovinos , Eletroforese Capilar/instrumentação , Eletroforese Capilar/estatística & dados numéricos , Concentração de Íons de Hidrogênio , Hidrólise , Resinas de Troca Iônica , Nozes/química , Padrões de Referência , Soroalbumina Bovina/química , Espectrometria de Massas por Ionização por Electrospray/instrumentação , Espectrometria de Massas por Ionização por Electrospray/estatística & dados numéricosRESUMO
CE-ESI-MS with a liquid sheath interface and IT mass analyzer was used for analysis of siderophores from different strains of Methylobacterium spp. citrus endophyte extracts. Three Methylobacterium strains were investigated according to positive bioassay tests. Bacteria cultures were grown under Fe(III) absence (siderophore producing cultures) and under Fe(III) presence (control cultures). Siderophores were extracted from culture supernatant with polystyrene resins. BGE and sheath-liquid composition were optimized, respectively, in order to assure both, best peak resolution and ESI-MS sensitivity. The best analysis conditions were obtained with 100 mmol/L ammonium bicarbonate at pH 8 as BGE and methanol:H(2)O 25:75 + 0.05% formic acid as sheath liquid. CZE-ESI-MS analysis revealed two possible siderophores, according to bacterium species, presenting M(r) of 1004.3 and 798.3 Da.
