Silica nanoparticles for separation of biologically active amines by capillary electrophoresis with laser‐induced native fluorescence detection

Abstract

This paper describes the analysis of biologically active amines by capillary electrophoresis (CE) in conjunction with laser-induced native fluorescence detection. In order to simultaneously analyze amines and acids as well as to achieve high sensitivity, 10 mM formic acid solutions (pH < 4.0) containing silica nanoparticles (SiNPs) were chosen as the background electrolytes. With increasing SiNP concentration, the migration times for seven analytes decrease as a result of increase in electroosmotic flow (EOF) and decrease in their electrophoretic mobilities against EOF. A small EOF generated at pH 3.0 reveals adsorption of SiNPs on the deactivated capillary wall. The decreases in electrophoretic mobilities with increasing SiNP concentration up to 0.3x indicate the interactions between the analytes and the SiNPs. Having a great sensitivity (the limits of detection at a signal-to-noise ratio (S/N) = 3 of 0.09 nM for tryptamine (TA)), high efficiency, and excellent reproducibility (less than 2.4% of the migration times), this developed method has been applied to the analysis of urinal samples with the concentrations of 0.50 +/- 0.02 microM, 0.49 +/- 0.04 microM, and 74 +/- 2 microM for TA, 5-hydroxytryptamine, and tryptophan, respectively. The successful examples demonstrated in this study open up a possibility of using functional nanoparticles for the separation of different analytes by CE.

Electrophoretic Separation of Proteins in Capillaries Filled with Poly(ethylene oxide)-stabilized Silver Nanoparticles

“…Silica nanoparticles and organically modified silica nanoparticles were employed in capillary electrochromatography (CEC) separation of polycyclic aromatic hydrocarbons (PAHs), 18 aromatic acids 19,20 and catecholamines. 21 Colloidal gold nanoparticles were synthesized and added to CE buffers for separation of toluidines. 22 Molecularly imprinted polymer (MIP) nanoparticles were synthesized and employed to separate enantiomers of propranolol.…”

Capillary electrophoretic separation of biologically active amines and acids using nanoparticle‐coated capillaries

“…Although HPLC is still the most common method for the analysis of biogenic amines and their metabolites, CZE, MEKC, and CEC have recently become attractive [7][8][9][10][11]. CZE is easy but does not provide enough resolving power for the separation of the analytes.…”

“…To optimize separation resolution of amines and acids by CZE, buffer pH value close to 4.0 is favorable. In addition, the analytes are more stable and also possess strong intrinsic fluorescence characteristics at low pH when excited by using a UV laser at 266 nm [7,8]. In order to increase EOF mobility at low pH, strategies such as use of CTAB as well as anionic and cationic polymers to form bilayers or multilayers on the capillary wall have been suggested [12][13][14][15][16].…”

“…We have recently demonstrated the use of formic acid solutions (pH,4.0) containing silica nanoparticles (SiO 2 NPs) for the separation of biogenic amines and their metabolites by CE with LIF detection [7]. As a result of adsorption of SiO 2 NPs on the capillary wall, a small and constant EOF at high electric field was generated, and analyte adsorption was minimized.…”

“…Although SiO 2 NP-t treated capillaries provide improved efficiency for amines, they are unsuitable for simultaneous separation of biogenic amines and their metabolites as a result of small EOF at low pH [7]. In order to generate EOF with desired directions and magnitudes, we treated capillaries with a positively charged polyelectrolyte -poly(L-lysine) (PLL) -and SiO 2 NPs by a layer-by-layer assembly technique.…”