Combining Photodegradation in a Liquid-Core-Waveguide Cell with Multiple-Heart-Cut Two-Dimensional Liquid Chromatography

Abstract

Photodegradation greatly affects everyday life. It poses challenges when food deteriorates or when objects of cultural heritage fade, but it can also create opportunities applied in advanced oxidation processes in water purification. Studying photodegradation, however, can be difficult because of the time needed for degradation, the inaccessibility of pure compounds, and the need to handle samples manually. A novel light-exposure cell, based on liquid-core-waveguide (LCW) technology, was embedded in a multiple-heart-cut two-dimensional liquid chromatography system by coupling the LCW cell to the multiple-heart-cut valve. The sample was flushed from the heart-cut loops into the cell by an isocratic pump. Samples were then irradiated using different time intervals and subsequently transferred by the same isocratic pump to a second-dimension sample loop. The mixture containing the transformation products was then subjected to the second-dimension separation. In the current setup, about 30–40% of the selected fraction was transferred. Multiple degradation products could be monitored. Degradation was found to be faster when a smaller sample amount was introduced (0.3 μg as compared to 1.5 μg). The system was tested with three applications, that is, fuchsin, a 19th-century synthetic organic colorant, annatto, a lipophilic food dye, and vitamin B complex.

Characterization of Dye-Loaded Poly(lactic-co-glycolic acid) Nanoparticles by Comprehensive Two-Dimensional Liquid Chromatography Combining Hydrodynamic and Reversed-Phase Liquid Chromatography

“…Retention modeling could be applied in future work to predict optimal trapping conditions and facilitate method development. 41 Optimized HDC × RPLC Separation of Dye-Loaded Polymeric NPs. The HDC × RPLC system was applied under the optimized conditions for the analysis of the four different NP samples (Figure 4).…”

Sample transformation in online separations: how chemical conversion advances analytical technology

“…149 Following upon this work, we demonstrated the implementation of an LCW in (mD-)LC systems in several recent works. [150][151][152] The initial system used a multiple heart-cutting approach where a mixture of analytes can be separated in the first dimension and several analytes may be selected to be subjected to light degradation. 151 The degradation products can subsequently be analyzed by a second-dimension separation.…”

An Introduction and Recent Advances in the Analytical Study of Early Synthetic Dyes and Organic Pigments in Cultural Heritage

“…The knowledge of the precise chemical formulation of reference materials and the creation of exhaustive databases is fundamental for the correct description of dye degradation pathways [20,21]. Several studies on dye degradation and the identification of the photo-oxidation products have been conducted by HPLC-DAD-MS/MS under photo-accelerated conditions in solution [26,62,173,197,200,211,213] or in painting/textile matrices [65,208,210] as well as with attention to other mechanisms not related to light exposure [212]. Some of the observations gathered are summarised in the following sections.…”

“…Dealkylation is a known photodegradation pathway of various classes of synthetic colourants [28], especially those containing N-alkylated functionalities, such as some triarylmethane dyes (Methyl Violets, Diamond Greens, Patent Blues, etc.) [20,173,197,211,213], as well as Rhodamines [187,208] and some azines [20,21]. These colourants are often detected as mixtures of differently alkylated molecules.…”

“…The sample is flushed from the heart-cut loops into the cell by an isocratic pump. It is then irradiated using different time intervals and subsequently transferred by the same isocratic pump to a second-dimension sample loop to be separated the second dimension [197]. The analytical performance of the new system was validated [198] and tested on dye references [199,200].…”