Normal Raman spectroscopy is used as an on-line detector for capillary isotachophoresis (ITP) of adenosine 5'-triphosphate, adenosine 5'-diphosphate, and adenosine 5'-monophosphate in phosphate buffers. Preconcentration is from a 1 x 10(-2) M phosphate buffer (pH 7.5) into a leading electrolyte of 0.1 M KCl or Na2SO4, with a terminating electrolyte of 0.1 M 4-morpholinepropane-sulfonic acid. The ribonucleotides are concentrated to above 10(-2) M at the detection window, allowing measurement of Raman spectra with 1 s integration, from starting concentrations of 5 x 10(-6) M or higher.
Normal Raman spectroscopy is used as an on-line detector for capillary electrophoresis (CE) to detect sub-ppm mixtures of nitrate and perchlorate in water. Field-amplified injection, a form of sample stacking, into a running electrolyte of 0.1 M KCl increases the analyte concentration at the detection window by up to 1800 times its starting value. Raman bands of nitrate (1047 cm−1) and perchlorate (934 cm−1) are measured in a total separation time of less than 3 min, with only 1-s integration times. The Raman spectroscopy of solutions originally 1 × 10−5 M nitrate (620 ppb) and perchlorate (1 ppm) is demonstrated.
The formation of 3.5% T, 3.3% C cross-linked polyacrylamide is monitored in 75-microns-i.d. electrophoresis capillaries by Raman microprobe spectroscopy. The disappearance of the acrylamide 1292-cm-1 band is followed with 60-s time resolution for 30 min, and 2-4 min resolution for up to 10 h. Polymerization is 98% complete in 1.5 h and greater than 99% complete after 2 h. In the 900-1700-cm-1 region no bands attributable to cross-linking are observable. Reaction in the capillary follows second-order kinetics. The reaction is faster in the bulk system because heat dissipation is not sufficient to maintain a constant temperature.
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