Highly resolved separation and sensitive amperometric detection of amino acids with an assembled microfluidic device.

An assembled microfluidic device (AMD) was constructed for highly resolved separation and sensitive amperometric detection of amino acids. In the AMD three polymer retainers were integrated with a quartz capillary and a copper microdisk electrode. A facile ultrasonic method was suggested for the preparation of sampling fracture on the capillary. The fracture led to separation efficiency up to 340,000 plates/m and improved greatly the sensitivity for amino acid detection in an 8 cm long quartz capillary. At a sampling voltage of 100 V for 2 s and a separation voltage of 1800 V (225 V/cm) within 300 s, the linear ranges of 12 amino acids determination at +0.8 V (versus Ag/AgCl) were from 12, 20, 17, 27, 31, 44, 25 and 45 to 750 microM for tryptophan, phenylalanine, methionine, valine, threonine, alanine, serine and glycin, and 4.6, 17, 16 and 49 microM to 1.0 mM for lysine, proline, leucine and tyrosine with the detection limit (S/N=3) down to 1.4 microM for lysine. The designed AMD could be successfully applied to analyze amino acids in beverage samples with recovery from 97.8 to 105.2%, indicating its advantages and potential analytical application in different fields.