In-situ UV-Visible spectrometry as an alternative to determine solute concentrations at high temporal frequency in organic-rich stream waters

<p>In-situ monitoring of the temporal variation of solutes’ (nutrients and metals) concentrations as tracers can enhance knowledge of the hydrological and biogeochemical behavior of catchments. UV-Visible spectrometry represents a relatively inexpensive and easily used tool to explore how those concentrations vary in time at high temporal frequency. However, it is not yet clear which are the best calibration methods and which solutes can be modeled with this approach. In this investigation we explored the relationship between solutes’ concentrations and wavelength absorbance in the UV-Visible range to find the best calibration method and to identify solutes that could be effectively predicted. To this end, we installed a UV–Visible spectrometer probe in a high-altitude and organic-rich tropical Andean (Páramo) stream to record the wavelength absorbance at a 5-min temporal resolution from December 2017 to March 2019. Simultaneously, we sampled stream water at 4-hour frequency for subsequent determination of solutes via ICP-MS in the laboratory. Our results show that multivariate statistical methods outperformed simpler calibration strategies to model the solutes’ concentrations that could be effectively predicted using calibration and validation datasets. Eleven out of 21 evaluated solutes (Al, DOC, Ca, Cu, K, Mg, N, Na, Rb, Si and Sr) were successfully calibrated (NSE > 0.50). This finding suggests the possibility of calibrating solutes (i.e., metals) that had not previously been calibrated through UV-Visible spectrometry in the field. Interestingly, the calibration was feasible for all solutes that presented a statistically significant correlation with dissolved organic carbon. The findings of this research provide insights into the value of in-situ operation of spectrometers to monitor water quality in organic-rich streams (e.g., peatlands). This research contributes to our understanding of aquatic ecosystems alongside assessing catchment hydrological functioning and also can enhance the protection of human water supplies.</p>

BORON-SILICA BASED MESOPOROUS FOR CURCUMINOID ISOLATION FROM TURMERIC EXTRACT

Objective: The purpose of this study was to develop the isolation method for curcuminoid from turmeric extract using boron-silica based mesoporous as an adsorbent. Methods: The formation of mesoporous materials were conducted using the sol-gel technique. The characterization of mesoporous materials was analyzed using a scanning electron microscope (SEM), transmission electron microscope (TEM), and Fourier transforms infrared spectrometry (FTIR). The extraction of turmeric was done by solvent extraction using ethanol 96 %. The isolation of curcuminoid was achieved by the adsorption method using mesoporous materials, both for silica-based mesoporous (MCM) and boron-silica based mesoporous (BMCM). The elution of curcuminoid-loaded mesoporous was conducted using various solvents. The concentration of total curcuminoid and its compounds was measured by visible spectrometry and high-performance liquid chromatography (HPLC). Results: Morphology of MCM and BMCM shows the homogenous regular spherical shape, but having a different size. MCM has a smaller diameter particle size (500-600 nm) compared to BMCM (700-900 nm). On the other hand, BMCM has a smaller pore size (1-5 nm) compared to MCM (5-20 nm). The FTIR spectra of BMCM shows the additional vibration at 1400-1600 cm for B-O-H bond. Visible spectrometry measurement shows that the highest concentration of curcuminoid eluted from BMCM is 65.411±0.056 ppm by using ethyl acetate as a solvent, while the concentration of curcuminoid eluted from MCM is 11.503±0.054 ppm by using the same solvent. The results of curcuminoid adsorption and elution, indicating that ethyl acetate is the best solvent to elute curcuminoid due to its 98.83 % purity using HPLC analysis. Conclusion: It was concluded that boron-silica based mesoporous showed stronger curcuminoid adsorption than silica-based mesoporous therefore found to be a potential adsorbent for curcuminoid isolation from turmeric extract.