High-sensitivity spectrophotometry

Photothermal refraction as a microbore liquid chromatography detector in femtomole amino acid determination

“…On the other hand, it is interesting to consider the absorbance across the detector cuvette at the detection limit, corresponding to an absorbance of 1 X 10™7. Considering our definition of detection limit, this absorbancé level is better than any other reported absorbance technique (22). Furthermore, if the path length of the measurement is defined as the pump beam spot size, 2 µ , then the absorbance detection limit is improved by 2 orders of magnitude.…”

Pulsed laser induced thermal diffraction for absorption measurements in small volumes

“…While the limit of detection in absorbance per unit pathlength is not spectactular, the corresponding absorbance across the entire grating interaction length given by eq 7 is Amin = 1.5 X 10~4 which was achieved in a total probe volume of 38 nL. The aqueous sample medium, chosen for this study because it provided a convenient, stable absorption standard (18), represents the most difficult case for thermooptical methods of detection, due to the small (dn/dT) and the large specific heat of water compared to other solvents (5,22). By changing the solvent to carbon tetrachloride, for example, one would expect an 18-fold increase in the square root of the diffraction efficiency based on eq 9 and the thermooptical properties of the two solvents (23,24).…”

Thread-based microfluidic three channel device in combination with thermal lens detection for the determination of copper and zinc

“…where E represents the so-called enhancement factor compared to conventional transmission measurements, A is the absorbance of sample, P is the excitation laser power and l is the laser wavelength. 8,9 Spectra measurements were obtained using a UV-2550 UV-Vis spectrophotometer (Shimadzu, Japan). An atomic absorption spectrophotometer (AAS) was used for comparing the determination results.…”

“…The intensity of the thermal lens is investigated by its effect on the divergence of the same laser beam (single TLS) or on the divergence of another probe laser beam (dual laser TLS). TLS offers high sensitivity (up to 10 À8 mol L À1 ) 9 and good spatial resolution, and it is suitable for the detection of a micro-volume sample. It is also easy to combine it with the hyphenation method and preconcentration procedures.…”