Pressurized hot water extraction (PHWE, also known as subcritical water extraction) is commonly considered to be an environmentally friendly extraction technique that could potentially replace traditional methods that use organic solvents. Unfortunately, the applicability of this technique is often limited by the very low water solubility of the target compounds, even at high temperatures. In this paper, the scope for broadening the applicability of PHWE by adjusting the pH of the water used in the extraction is demonstrated in the extraction of curcumin (which exhibits very limited water solubility) from untreated turmeric (Curcuma longa L.) rhizomes. Although poor extraction yields were obtained, even at high temperatures when using degassed water or neutral phosphate buffer as the extraction medium, yields exceeding those obtained by Soxhlet extraction were achieved using highly acidic pH buffers due to curcumin protonation. The influence of the temperature, pH, and buffer concentration on the extraction yield were investigated in detail by means of a series of designed experiments. Optimized conditions for the extraction of curcumin from turmeric by PHWE were estimated at 197 °C using 62 g/L buffer concentration at pH 1.6. The relationships between these variables were subjected to statistical analysis using response surface methodology.
A molecularly imprinted polymer was prepared using (E)-resveratrol as template and was evaluated for multicomponent multiclass analysis of polyphenolic compounds in complex matrices such as natural and alcoholic beverages. Chromatographic evaluation of the polymer exhibited high selectivity for (E)-resveratrol and its structural analogues, quercetin, and other flavonoids. An analytical procedure based on molecularly imprinted solid phase extraction (MISPE) and high-performance liquid chromatography coupled to UV detector was developed and validated for determination of (E)-resveratrol and quercetin in wine and fruit juice samples. The specific binding capacity of the MIP was estimated as 80 μg g(-1) polymer by the cartridge test. MISPE sample pretreatment allows an excellent sample cleanup, enormously decreasing the number of coextracted potentially interfering compounds. Under the described conditions, by extracting 2 mL samples a clean extract is obtained and (E)-resveratrol and quercetin could be easily identified at concentration levels of, respectively, 1.5 and 7.0 μg L(-1).
Gentamicin C antibiotics are important because they are active against many multidrug-resistant Gram-negative bacilli. Unfortunately, their clinical usefulness is limited by their toxicity. Because of the difficulty involved in separating its different components, the US and European pharmacopeias both specify that the composition of gentamicin C should be determined by liquid chromatography with pulsed electrochemical detection. Here, we assess the usefulness of a porous graphitic carbon (PGC) HPLC column for separating the components of gentamicin C, and report chromatographic conditions that enable its direct characterization by PGC chromatography directly coupled to electrospray mass spectrometry. Native major components of gentamicin and impurities in commercial formulations were retained and separated on the PGC column without any need for derivatization, using mobile phases basified with ammonium hydroxide. When coupled with detection by conventional electrospray ion trap mass spectrometry (ESI-IT-MS), several previously reported impurities were detected easily, including the most polar gentamicin impurity, garamine. When operating in full-scan mode, it was possible to identify and quantitate gentamicin-related compounds using injected samples of only a few picograms. Under the described conditions, all analytes were eluted in less than 10 min and the LC-MS analyses exhibited excellent stability and linearity. The method's effectiveness was evaluated by analyzing commercial gentamicin batches and in-house formulations. When the PGC chromatographic system was coupled to an evaporative light-scattering detector, detection limits of 40-70 ng were achieved for various major gentamicin components. The chromatographic method was applied on a semi-preparative scale to purify the five major components.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.