Isotachophoretic Separations on a Microchip. Normal Raman Spectroscopy Detection

• Published in: Analytical chemistry (Washington) Vol. 70; no. 18; pp. 3766 - 3769
• Main Authors: Walker, Patrick A, Morris, Michael D, Burns, Mark A, Johnson, Brian N
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 15.09.1998
• Subjects: Analytical chemistry; Chemistry; Chromatographic methods and physical methods associated with chromatography; Diquat - analysis; Electrophoresis - instrumentation; Electrophoresis - methods; Exact sciences and technology; Herbicides - analysis; Herbicides - isolation & purification; Indicators and Reagents; Miniaturization; Other chromatographic methods; Paraquat - analysis; Paraquat - isolation & purification; Scientific imaging; Spectrum Analysis, Raman - instrumentation; Spectrum Analysis, Raman - methods; Trace analysis; Chemical analysis; Multicomponent analysis; Nitrogen heterocycle; Coupled method; Paraquat; Diquat; Raman spectrometry; Isotachophoresis; Microminiaturization; Herbicide
• ISSN: 0003-2700; 1520-6882
• DOI: 10.1021/ac980195h

Isotachophoretic separations of the herbicides paraquat and diquat are performed in a glass microchip etched channel and monitored on-chip by normal Raman spectroscopy. The 40-μm-wide and 75-μm-deep separation channels are chemically etched in a serpentine design to 21-cm total length. A 120-μm-thick glass cover slip is used to seal the channels. Separation field strengths up to 380 V/cm are used. The microchip is directly coupled to a Raman microprobe. No interfacing is required. Raman spectra are generated with a 2-W, 532-nm NdYVO4 laser and collected at 8-cm-1 resolution with a holographic transmissive spectrograph and a cryogenically cooled CCD. Data acquisition is at 2−5 spectra/s. Raman isotachopherograms of the pesticides at starting concentrations as low as 2.3 × 10-7 M (60 ppb paraquat/80 ppb diquat) are presented.