Determination of synephrine in weight-loss products using high performance liquid chromatography with acidic potassium permanganate chemiluminescence detection

Adrenergic amines found in extracts of Citrus aurantium (bitter orange) evoke analytically useful chemiluminescence with acidic potassium permanganate in the presence of polyphosphates. From corrected chemiluminescence spectra, the wavelength of maximum intensity for these reactions was 680 ± 5 nm and, using flow injection analysis methodology, limits of detection for synephrine, octopamine, tyramine and hordenine were found to be between 1 × 10⁻⁹ and 1 × 10⁻⁸ M. We have applied this method of detection to the rapid determination of synephrine in dietary supplements using monolithic column chromatography.

Novel 10- and 20- membered tin- and silicon-containing rings: synthesis, complexation behavior and conversion into a lewis acidic polymer

Reaction of the dimethylsilylmethyl-substituted tetraorganotin derivative CH₂[CH₂Sn(Ph₂)CH₂Si(H)Me₂]₂ (1) and CH₂[CH₂Sn(Ph₂)CH₂Si(i-PrO)Me₂]₂ (3), respectively, with mercuric chloride afforded the novel silicon- and tin-containing 10- and 20-membered rings cyclo-CH₂[CH₂Sn(Cl₂)CH₂Si(Me₂)]₂O (4) and cyclo-CH₂[CH₂Sn(Cl₂)CH₂Si(Me₂)OSi(Me₂)CH₂Sn(Cl₂)CH₂]₂CH₂ (5). Both compounds 4 and 5 can be converted into the soluble Lewis acidic polymer poly-[Si(Me₂)CH₂Sn(Cl₂)(CH₂)₃Sn(Cl₂)CH₂Si(Me₂)O] (8). ¹¹⁹Sn NMR studies indicate that 4 acts as a bidentate Lewis acid toward chloride ions, exclusively forming the 1:1 complex [cyclo-CH₂[CH₂Sn(Cl₂)CH₂Si(Me₂)]₂O·Cl]-[(Ph₃P)₂N]⁺ (7). The molecular structures as determined by single-crystal X-ray diffraction analysis of 4 and 7 are reported.

The characteristic red chemiluminescence from reactions with acidic potassium permanganate : further spectroscopic evidence for a manganese(II) emitter

A direct comparison of the laser-induced photoluminescence of manganese(II) with the chemiluminescence from the reaction between acidic potassium permanganate and sodium borohydride was used to confirm that the characteristic red emission from this widely used chemiluminescence reagent emanates from an electronically excited manganese(II) species.

Bronsted acidic ionic liquids derived from alkylamines as catalysts and mediums for Fischer esterification : study of structure–activity relationship

Esterification of acetic acid with 1-octanol was studied using a series of alkylammonium salts as Brønsted acidic ionic liquids. The following
ionic liquids were prepared and used as catalysts and mediums in the esterification reaction; [Et₃NH][HSO₄], [Et₃NH][H₂PO₄], [Et₃NH][BF₄],
[Et₃NH][p-CH₃C₆H₄SO₃], [Et₂(PhCH₂)NH][HSO₄], [n-Bu₃NH][HSO₄], [n-Oct₃NH][HSO₄], [Et₂NH₂][HSO₄], [Et₂NH₂][H₂PO₄], [Et₂NH₂]
[BF₄], [i-Pr₂NH₂][HSO₄], [EtNH₃][HSO₄], [EtNH₃][H₂PO₄], and [EtNH₃][BF₄]. Higher acidity of the anion in the ionic liquid resulted in high yield of the ester. Yield of the ester decreased with increase in the size of the cation. There was no phase separation in the reactions where size of anion and/or cation was bigger

Chemiluminescence from reactions with bis-cyclometalated iridium complexes in acidic aqueous solution

Chemical reactions between certain bis-cyclometalated iridium complexes, cerium(IV) and organic reducing agents in aqueous solution produce an emission of light which in some cases is more intense than that from analogous reactions with conventional ruthenium-based reagents, thus providing a new avenue for chemically-initiated luminescence detection.

Emitting species in chemiluminescence reactions with acidic potassium permanganate : a re-evaluation based on new spectroscopic evidence

The reaction of acidic potassium permanganate with a wide range of compounds is known to produce a broad red emission, and there is strong evidence for an excited manganese(II) emitting species. Nevertheless, numerous researchers have proposed other emitters for reactions with acidic potassium permanganate, particularly for systems where fluorescent compounds were present, either as enhancers or reaction products. We have examined many reactions of this type and found that, in most cases, the same red emission was produced. There were, however, some exceptions, including the oxidation of dihydralazine, certain thiols and sulphite (each in the presence of an enhancer).

Correlation between acidic potassium permanganate chemiluminescence and in vitro cell culture assay : physiologically meaningful antioxidant activity

There is great interest in the activity of antioxidant molecules, including polyphenols, from food and plant sources. Acidic potassium permanganate chemiluminescence signal intensity was shown to predict the ability of polyphenols to positively act on cellular redox state and attenuate oxidative stress in cultured skeletal muscle cells.

Structure and properties of biomedical films prepared from aqueous and acidic silk fibroin solutions

Silk fibroin films are promising materials for a range of biomedical applications. To understand the effects of casting solvents on film properties, we used water (W), formic acid (FA), and trifluoroacetic acid (TFA) as solvents. We characterized molecular weight, secondary structure, mechanical properties, and degradation behavior of cast films. Significant degradation of fibroin was observed for TFA-based film compared to W and TA-based films when analyzed by SDS-PAGE. Fibroin degradation resulted in a significant reduction in tensile strength and modulus of TFA-based films. Compared to water, TFA-based films demonstrated lower water solubility (19.6% vs. 62.5% in 12 h) despite having only a marginal increase in their ß-sheet content (26.9% vs. 23.7%). On the other hand, FA-based films with 34.3% ß-sheet were virtually water insoluble. Following solubility treatment, ß-sheet content in FA-based films increased to 50.9%. On exposure to protease XIV, water-annealed FA-based films lost 74% mass in 22 days compared to only 30% mass loss by ethanol annealed FA films. This study demonstrated that a small variation in the ß-sheet percentage and random coil conformations resulted in a significant change in the rates of enzymatic degradation without alteration to their tensile properties. The film surface roughness changed with the extent of enzymatic hydrolysis.

Determination of intracellular glutathione and glutathione disulfide using high performance liquid chromatography with acidic potassium permanganate chemiluminescence detection

Measurement of glutathione (GSH) and glutathione disulfide (GSSG) is a crucial tool to assess cellular redox state. Herein we report a direct approach to determine intracellular GSH based on a rapid chromatographic separation coupled with acidic potassium permanganate chemiluminescence detection, which was extended to GSSG by incorporating thiol blocking and disulfide bond reduction. Importantly, this simple procedure avoids derivatisation of GSH (thus minimising auto-oxidation) and overcomes problems encountered when deriving the concentration of GSSG from ‘total GSH’. The linear range and limit of detection for both analytes were 7.5 × 10−7 to 1 × 10−5 M, and 5 × 10−7 M, respectively. GSH and GSSG were determined in cultured muscle cells treated for 24 h with glucose oxidase (0, 15, 30, 100, 250 and 500 mU mL−1), which exposed them to a continuous source of reactive oxygen species (ROS). Both analyte concentrations were greater in myotubes treated with 100 or 250 mU mL−1 glucose oxidase (compared to untreated controls), but were significantly lower in myotubes treated with 500 mU mL−1 (p < 0.05), which was rationalised by considering measurements of H2O2 and cell viability. However, the GSH/GSSG ratio in myotubes treated with 100, 250 and 500 mU mL−1 glucose oxidase exhibited a dose-dependent decrease that reflected the increase in intracellular ROS.

Extending the analytical utility of acidic potassium permanganate chemiluminescence

The purpose of this work was to improve the analytical usefulness of acidic potassium permanganate chemiluminescence for the determination of various analytical compounds. This thesis also examined the fundamental chemistry involved with these types of reactions.