Soluble manganese (IV); a new chemiluminescence reagent

The oxidations of twenty five organic and inorganic species, with solublised manganese(IV), were found to elicit analytically useful chemiluminescence with detection limits (3 × S/N) for Mn(II), Fe(II), morphine and codeine of 5 × 10^–8 M, 2.5 × 10^–7 M, 7.5 × 10^–8 M and 5 × 10^–8 M, respectively. Additionally, the corrected spectra from four different analytes gave wavelengths of maximum emission in the range from 733 nm up to 740 nm suggesting that all these chemiluminescence reactions shared a common emitting species.

Chemically induced phosphorescence from manganese(II) during the oxidation of various compounds by manganese(III), (IV) break and (VII) in acidic aqueous solutions

Chemiluminescence was observed during the manganese(III), (IV) and (VII) oxidations of sodium tetrahydroborate, sodium dithionite, sodium sulfite and hydrazine sulfate in acidic aqueous solution. From the corrected chemiluminescence spectra, the wavelengths of maximum emission were 689±5 and 734±5 nm when the reactions were performed in sodium hexametaphosphate and sodium dihydrogenorthophosphate/ orthophosphoric acid environments, respectively. The corrected phosphorescence spectrum of manganese(II) sulfate in a solution of sodium hexametaphosphate at 77 K exhibited two peaks with maxima at 688 and 730 nm. The chemical and spectroscopic evidence presented strongly supported the postulation that the emission was an example of solution-phase chemically induced phosphorescence of manganese(II) thereby, confirming earlier predictions that the chemiluminescence from acidic potassium permanganate reactions originated from an excited manganese(II) species.

Comparison of soluble manganese(IV) and acidic potassium permanganate chemiluminescence detection using flow injection and sequential injection analysis for the determination of ascorbic acid in vitamin C tablets

The limits of detection (3s) for ascorbic acid were 5×10⁻⁸ M with acidic potassium permanganate using both flow injection analysis (FIA) and sequential injection analysis (SIA) whereas the soluble manganese(IV) afforded 1×10⁻⁸ M and 5×10⁻⁹ M for FIA and SIA, respectively. Determinations of ascorbic acid in Vitamin C tablets were achieved with minimal sample pretreatment using a standard additions calibration and gave good agreement with those of iodimetric titration.

Soluble manganese(IV) as a chemiluminescence reagent for the determination of opiate alkaloids, indoles and analytes of forensic Interest

We present the results of our investigations into the use of soluble manganese(IV) as a chemiluminescence reagent, which include a significantly faster method of preparation and a study on the effect of formaldehyde and orthophosphoric acid concentration on signal intensity. Chemiluminescence detection was applied to the determination of 16 analytes, including opiate alkaloids, indoles and analytes of forensic interest, using flow injection analysis methodology. The soluble manganese(IV) reagent was less selective than either acidic potassium permanganate or tris(2,2′-bipyridyl)ruthenium(III) and therefore provided a more universal chemiluminescence detection system for HPLC. A broad spectral distribution with a maximum at 730 ± 5 nm was observed for the reaction between the soluble manganese(IV) and a range of analytes, as well as the background emission from the reaction with the formaldehyde enhancer. This spectral distribution matches that reported for chemiluminescence reactions with acidic potassium permanganate, where a manganese(II) emitting species was elucidated. This provides further evidence that the emission evoked in reactions with soluble manganese(IV) also emanates from a manganese(II) species, and not bimolecular singlet oxygen as suggested by previous authors.

Manganese dioxide allylic and benzylic oxidation reactions in ionic liquids

Ionic liquids 1-butyl-3-methylimidazolium tetrafluoroborate [bmIm][BF₄] and 1-butyl-3-methylimidazolium hexafluorophosphate [bmIm][PF₆] were evaluated as reaction media for allylic and benzylic oxidation reactions using manganese dioxide. The use of ionic liquids as an extractant in the reaction work-up was also investigated. Procedures for recycling of the [bmIm][PF₆] ionic liquids used in these MnO₂ oxidation reactions were also developed.

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.

Manganese (III) and manganese (IV) as chemiluminescence reagents : a review

Although potassium permanganate [Mn(VII)] has been used extensively as a chemiluminescence reagent for many decades, other manganese-based oxidants have only recently been explored for this purpose. There is strong evidence to suggest that, like permanganate, manganese(III) and manganese(IV) oxidants react with many molecules to produce an excited manganese(II) species that emits light. However, these reagents differ markedly in terms of selectivity, and possess characteristics that provide new avenues for detection, such as the immobilisation of solid manganese dioxide, the production of ‘soluble’ manganese(IV) nanoparticles, and the electrochemical generation of manganese(III). In this review we examine the emergence of these alternative manganese oxidants as chemiluminescence reagents.

Photocatalytic activity of manganese-doped ZnO nanocrystalline powders

ZnO nanocrystalline powders doped with up to 5 at% manganese were synthesized and their photocatalytic activity was studied. Doped ZnO powders were prepared using a sol-gel process. The crystal structure and grain size of the particles were characterized by X-ray diffractometry and optical properties were studied using UV-Vis spectroscopy. The photoactivity of undoped and doped ZnO nanocrystalline powders was evaluated by monitoring the photo-bleaching of the aqueous solutions of Rhodamine B dye in the presence of ZnO under simulated sunlight. The results showed that up to 3 at% manganese were successfully doped into the nanocrystalline ZnO and that manganese-doping reduced the photocatalytic activity of ZnO.

Effects of undoped and manganese-doped zinc oxide nanoparticles on the colour fading of dyed polyester fabrics

This paper describes the effects of applying coatings of an acrylic polymer containing nanoparticles of zinc oxide (ZnO) on the fading rate in artificial sunlight of polyester fabrics dyed with disperse dyes containing anthraquinone and benzopyran chromophores. Factors affecting the transparency and UV absorbance of the coatings are discussed. Removing the UV component of sunlight with ZnO nanoparticles markedly decreased the fading rate of the dyes, provided the polymer/ZnO film was not in direct contact with the fabric. When the treatment was applied directly to the fabrics, however, the protection against colour fading was different for the two dyes studied. Whereas the rate of colour fading of a benzopyran dye, of relatively low lightfastness, was decreased by the polymer-ZnO film, the treatment increased the fading rate of the dye of higher lightfastness, based on anthraquinone. This effect has been attributed to the generation of reactive oxygen species (ROS) when ZnO is exposed to UV. The effect of decreasing the photoactivity of ZnO by doping with manganese has been examined. For the benzopyran dye, the UV protection was greatly increased, whereas a much smaller improvement was found for the anthraquinone-based dye.

Biobsorbent properties of biosolids for aqueous zinc, manganese and cyanide removal

Biosolids were used to remove zinc, manganese and cyanide from mining wastewaters. The effect of aqueous parameters and reaction variables on contaminant biosorption was quantified. The mechanism of removal was adsorption onto amine and carboxyl functional groups. Immobilisation was investigated to overcome problems of swelling and disintegration of the biosolids.

Investigations into reactions involving manganese(IV) chemiluminescence

The reactivity and characterisation of solubilised manganese(IV) as a chemiluminescence reagent were systematically investigated. The analytical utility of this reagent was established for the determination of various alkaloids, pharmaceuticals and compounds of forensic interest. The methodology was then successfully applied to industrial process monitoring, clinical and illicit drug samples.

Surface-Enhanced Infrared Spectra of Manganese (III) Tetraphenylporphine Chloride Physisorbed on Gold Island Films

Surface-enhanced infrared absorption (SEIRA) spectra of manganese (III) tetraphenylporphine chloride (Mn(TPP)Cl) on metal island films were measured in transmission mode. Dependences of the enhancement factor of SEIRA on both the sample quantity and the type of evaporated metal were investigated by subsequently increasing the amount of Mn(TPP)Cl on gold and silver substrates. The enhancement increases nonlinearly with the amount of sample and varies slightly with the thickness of metal islands. In particular, the SEIRA transmission method presents an anomalous spectral enhancement by a factor of 579, with substantial spectral shifts, observed only for the physisorbed Mn(TPP)Cl that remained on a 3-nm-thick gold film after immersion of the substrates into acetone. A charge-transfer (CT) interaction between the porphyrinic Mn and gold islands is therefore proposed as an additional factor in the SEIRA mechanism of the porphyrin system. The number of remaining porphyrin molecules was estimated by calibration-based fluorescence spectroscopy to be 2.36×1013 molecules (i.e., ~2.910-11 mol/cm2) for a 3-nm-thick gold film, suggesting that the physisorbed molecules distributed very loosely on the metal island surface as a result of the weak van der Waals interactions. Fluorescence microscopy revealed the formation of microcrystalline porphyrin aggregates during the consecutive increase in sample solution. However, the immersion likely redistributed the porphyrin to be directly attached on the gold surface, as evidenced by an absence of porphyrinic microcrystals and the observed SEIRA enhancement. The distinctive red shift in the UV-visible spectra and the SEIRA-enhanced peaks indicate the presence of a preferred orientation in the form of the porphyrin ring inclined with respect to the gold surface.