On-line Spectroscopic Analysis Research Articles

Immunosuppressant flavonoids from Scutellaria baicalensis

Some plants used in Traditional Chinese Medicine serve as treatment for disease states where a suppression of the cellular immune response is desired. However, the compounds responsible for the immunosuppressant effects of these plants are not necessarily known.The immunosuppressant compounds in the roots of Scutellaria baicalensis, one of the most promising plants identified in a previous screening, were tracked by HPLC activity profiling and concomitant on-line spectroscopic analysis. Compounds were then isolated by preparative chromatography, and structures elucidated by spectroscopic methods. Twelve flavonoids (5–16) were identified from the active time windows, and structurally related flavones 2, 4, and 17, and flavanones 1 and 3 were isolated from adjacent fractions. All flavonoids possessed an unusual substitution pattern on the B-ring, with an absence of substituents at C-3 and C-4. Compounds 11, 13, 14, and 16 inhibited T-cell proliferation (IC50 values at 12.1–39 μM) at non-cytotoxic concentrations. The findings may support the use of S. baicalensis in disorders where a modulation of the cellular immune response is desirable.

Millisecond-Timescale Monitoring of PbS Nanoparticle Nucleation and Growth Using Droplet-Based Microfluidics.

The early-time kinetics (<1 s) of lead sulfide (PbS) quantum dot formation are probed using a novel droplet-based microfluidic platform, which allows for high-throughput and real-time optical analysis of the reactive process with millisecond time resolution. The reaction platform enables the concurrent investigation of the emission characteristics of PbS quantum dots and a real-time estimation of their size and concentration during nucleation and growth. These investigations reveal a two-stage mechanism for PbS nanoparticle formation. The first stage corresponds to the fast conversion of precursor species to PbS crystals, followed by the growth of the formed particles. The growth kinetics of the PbS nanoparticles follow the Lifshitz-Slyozov-Wagner model for Ostwald ripening, allowing direct estimation of the rate constants for the process. In addition, the extraction of absorption spectra of ultrasmall quantum dots is demonstrated for first time in an online manner. The droplet-based microfluidic platform integrated with online spectroscopic analysis provides a new tool for the quantitative extraction of high temperature kinetics for systems with rapid nucleation and growth stages.

Characterisation of the Degradation of Salvianolic Acid B Using an On‐line Spectroscopic Analysis System and Multivariate Curve Resolution

Chinese herbal medicines contain complex ingredients that are unstable during the manufacturing process. Current off-line methods are usually time-consuming and inaccurate. The aim of this study was to develop a continuous-flow-based on-line spectroscopic system for monitoring the degradation of unstable compounds in Chinese herbal medicines. An on-line spectroscopic analysis system in the evaluation of the degradation of unstable compounds was implemented, using salvianolic acid B from Danshen (Radix Salviae Miltiorrhizae) as a model compound. Resolution of the mixture spectra obtained during the reaction was performed with multivariate curve resolution (MCR), and the pure spectra and kinetic profiles of reactant species were reconstructed. The degradation process of salvianolic acid B is probably a consecutive two-step reaction of the form A → B → C, where A is salvianolic acid B, and B and C are the intermediate and final products, respectively. The intermediate and final products were suggested to be a mixture of lithospermic acid and danshensu [3-(3, 4-dihydroxyphenyl) lactic acid], and a mixture of danshensu and salvianolic acid A, respectively. The findings suggested that the combined use of on-line spectroscopic analysis and MCR might be a cheap, readily available, sensitive tool to monitor the transformation of unstable components of Chinese herbal medicines.

Reversed-phase HPLC of polymer additives with multiple on-line spectroscopic analysis (UV, IR, (1)H NMR and MS).

The reversed-phase chromatography of a number of polymer additives has been undertaken with on-line characterisation via a combination of diode array UV, (1)H NMR, IR spectroscopy and mass spectrometry. This combination of spectrometers enabled the on-flow collection of full UV, (1)H NMR, IR and mass spectra for a range of common polymer additives in amounts ranging from ca. 230 to 900 micro g on-column. The practical difficulties associated with multiple hyphenation and potential future developments are discussed.

HPLC analysis of ecdysteroids in plant extracts using superheated deuterium oxide with multiple on-line spectroscopic analysis (UV, IR, 1H NMR, and MS).

HPLC, using superheated D20 as the mobile phase, combined with on-line characterization via a combination of diode array UV, 1H NMR, FT-IR spectroscopy, and mass spectrometry has been used for the analysis of a standard of 20-hydroxyecdysone- and ecdysteroid-containing plant extracts. This combination of spectrometers enabled the on-flow collection of UV, 1H NMR, IR, and mass spectra not only for pure 20-hydroxyecdysone (100-400 microg on column) but also the major ecdysteroids present in crude extracts of Silene otites, Silene nutans, and Silene frivaldiskyana. The ecdysteroids unequivocally identified in these extracts included 20-hydroxyecdysone, polypodine B, and integristerone A.

Flow injection analysis with multiple on-line spectroscopic analysis (UV, IR, 1H-NMR and MS).

Studies on the capabilities of flow injection analysis (FIA) combined with on-line characterisation of model compounds via a combination of diode array UV, 1H-NMR, FT-IR spectroscopy and mass spectrometry are described. Using this combination of spectrometers enabled the on-flow collection of UV, 1H-NMR, IR and MS for a range of model compounds. Samples were introduced into the system as solutions in deuterium oxide in concentrations ranging from 1.4 to 8.4 mg ml(-1). A sample volume of 100 microl was used for FIA at a flow rate of 1 ml min(-1). From these studies a practical working quantity of ca. 140 microg/sample of analyte was determined which provided characteristic spectra.

High temperature reversed-phase HPLC using deuterium oxide as a mobile phase for the separation of model pharmaceuticals with multiple on-line spectroscopic analysis (UV, IR, 1H-NMR and MS)

The reversed-phase chromatography of a number of model pharmaceuticals using deuterium oxide (D2O) as the mobile phase at elevated temperatures, including superheated conditions (greater than 100 °C), is described. Following elution the analytes were characterised on-line via a combination of diode array UV, 1H-NMR, FT-IR spectroscopy and mass spectrometry. This combination of spectrometers enabled the on-flow collection of full UV, 1H-NMR, IR and mass spectra for a range of compounds in amounts ranging from 46 to 500 μg on-column. The advantages of the use of D2O alone as mobile phase for chromatography with multiple spectroscopic characterisation of analytes is discussed.

Free‐radical polymerization kinetics in extended ranges of temperature, pressure and monomer conversion

AbstractFree‐radical polymerizations have been studied within extended ranges of pressure, temperature, and monomer conversion, including reactions in supercritical phase, where polymerization rate and polymer properties may be continuously tuned. The methods by which propagation (kp) and termination (kt) rate coefficients of homopolymerizations may be determined as a function of P and T, partly up to 3000 bar and 250 °C, are based on using pulse lasers for inducing polymerization (PLP) either in conjunction with size exclusion chromatography (SEC), for kp measurement, or in conjunction with online spectroscopic analysis of monomer conversion, for kt/kp measurement. With kp from PLP‐SEC, the kt/kp data allow to deduce also individual rate coefficients for the termination step. kp primarily depends on temperature and pressure with the values being close to each other within a monomer family, such as the acrylic ester or the methacrylic ester family. Termination rate, which refers to a radical‐radical process, depends on P, T, monomer conversion, solvent type, and on chain length. The major changes of kt with conversion are illustrated using a model that takes segmental diffusion, translational diffusion, and reaction diffusion into account.

Separation of phycobiliprotein subunits by reverse-phase high-pressure liquid chromatography

Baseline separation of subunits of diverse phycobili-proteins was achleved by a reverse-phase HPLC gradient method with a C 4 large-pore column and a solvent system consisting of 0.1% trifluoroacetic acid (TFA) in water and 0.1% TFA in 2:1 (v/v) acetonitrile:isopropanol. The procedure was successfully applied to cyanobacterial allophycocyanin and C-phycocyanins, an unusual phycocyanin from a marine cyanobacterium, red algal B- and R-phycoerythrins, and a cryptomonad phycoerythrin. The subunit sizes in these proteins range from about 7.5 to 30 kDa. Sample recovery was in excess of 85% in all cases. On-line spectroscopic analysis with a multiple diode array detector allowed determination of the type and number of bilins carried by each subunit.