The effects of eluent mixing on TLS detection in gradient elution HPLC

Abstract

The effects of changing solvent composition on the LOD of TLS detection in gradient elution HPLC have been studied from the perspective of thermo-optical properties of the solvent. Hyphenated gradient high-performance liquid chromatography (HPLC)-thermal lens spectrometry (TLS), was used to separate and detect 13 carotenoid compounds and two chlorophylls. Utilization of mixing coils into the system reduces the inhomogeneities during eluent changes and therefore enables the application of thermal lens detection in the gradient HPLC method. For gradient chromatographic conditions in which the thermo-optical properties and related enhancement factor change as much as 50% over 10 min, the LODs for the TLS detector were enhanced by as much as three times in comparison with UV-Vis detection. For the isocratic part of the chromatogram, up to a tenfold improvement of LODs was achieved with TLS detection.

Simultaneous analysis of circulating 25-hydroxy-vitamin D3, 25-hydroxy-vitamin D2, retinol, tocopherols, carotenoids, and oxidized and reduced coenzyme Q10 by high performance liquid chromatography with photo diode-array detection using C18 and C30 columns alone or in combination

“…Use of Cookson reaction products of 25(OH)D were not a feasible option to improve signal strength either since pre-column derivatization of the vitamin D compounds would affect and alter all carotenoids while post-column derivatization was not possible due to the reagent being fluorescent [63,64]. TLSD using laser light at 476 nm was found to result in up to 100-fold lower detection limits for carotenoids vs. absorbance monitoring at 450 nm in conventional HPLC systems [65] but this was reduced to 2–10 fold better detection limits with gradient elution [66]. TLSD is currently very difficult to implement owing to its commercial unavailability.…”

Thermal Lens Spectrometry as Analytical Tool

“…Thus, the authors have demonstrated the viability of on-line detection for supercritical fluid extraction with a pulse thermal lens spectrometer. Logar et al 6 have investigated the possibilities of improving the performance of TLS detection and to analyze the changes of thermo-optical parameters during the gradient elution HPLC. The authors have selected pigments (13 carotenoids and two chlorophylls) as model compounds, LODs for gradient separation with TLS detection are 1.3-to 10-fold lower than for the UV-Vis detection.…”

“…However, despite these problems thermal lens spectrometry has consolidated its positions, proving its viability. The method is more sensitive that conventional transmission spectrometry 6 because the photothermal effect amplifies the measured optical signal (relative change in the beam intensity). The enhancement depends on the thermal and optical properties of the sample and the properties of the pump and probe laser beam.…”

Synthesis of hydrochloric acid solution for total mercury determination in natural waters

“…Considering the very low concentrations of mercury (Hg) in natural waters (0.05-5.00 ng L -1 ), important loss and contamination problems can arise in sampling, sampling treatment and analysis processes [1][2][3][4][5][6][7]. The main mercury loss is due to Hg adsorption on bottle walls, but it is now recognized that the addition of acid (e.g.…”

“…HCl) or oxidant (e.g. BrCl) allowed stabilisation of water samples for total dissolved Hg determination after filtration [4][5][6][7]. About contaminations, the routes are numerous and can lead to obtain erroneously high total mercury (Hg T ) concentrations [8].…”