Recent developments in optical detection methods for microchip separations

Abstract

This paper summarizes the features and performances of optical detection systems currently applied in order to monitor separations on microchip devices. Fluorescence detection, which delivers very high sensitivity and selectivity, is still the most widely applied method of detection. Instruments utilizing laser-induced fluorescence (LIF) and lamp-based fluorescence along with recent applications of light-emitting diodes (LED) as excitation sources are also covered in this paper. Since chemiluminescence detection can be achieved using extremely simple devices which no longer require light sources and optical components for focusing and collimation, interesting approaches based on this technique are presented, too. Although UV/vis absorbance is a detection method that is commonly used in standard desktop electrophoresis and liquid chromatography instruments, it has not yet reached the same level of popularity for microchip applications. Current applications of UV/vis absorbance detection to microchip separations and innovative approaches that increase sensitivity are described. This article, which contains 85 references, focuses on developments and applications published within the last three years, points out exciting new approaches, and provides future perspectives on this field.

Paired emitter–detector diode detection with dual wavelength monitoring for enhanced sensitivity to transition metals in ion chromatography with post-column reaction

“…The optical pathlength represented by the channel depth is generally shorter than 30 µm. 6 Light emitting diodes (LEDs) have become increasingly popular as light sources in separation systems [7][8][9][10] due to their advantageous characteristics such as low power consumption, low cost, increasing spectral range coverage (247 nm -1550 nm 11,12 ), size, intensity and efficiency. [13][14][15] Previously we demonstrated the use of a paired emitter-detector diode (PEDD) system as a highly sensitive photometric detector in liquid chromatography.…”

Detection of immunoglobulins in a laser induced fluorescence system utilizing polydimethysiloxane microchips with advanced surface and optical properties

“…The fluorescence detection is still the most popular optical method exploited in bioassays due to superior selectivity and sensitivity. 1 A variety of fluorescence excitation sources is available: ͑i͒ laser sources that produce coherent and low divergence beams, which are crucial in low volume detection ͓laser a͒ Author to whom correspondence should be addressed. Tel.…”

“…12 Recent progress in the laser technology has produced stable laser sources that cover a wide range of wavelengths from ultraviolet to infrared region. 1 Modern lasers can be focused into very small detection volumes. This fact gives them a great advantage in the microscale detection.…”

Design and optimization of a double-enzyme glucose assay in microfluidic lab-on-a-chip

“…18 This assay involves a two-reaction enzymatic assay with nicotinamide adenine dinucleotide phosphate ͑NADPH͒ as end product. Vermeir et al 16 performed this assay in a microplate with a volume of 200 l; the assay required 2 l of enzyme solution and took about 30 min to complete.…”