[Study on the Effects of Different Ferron System, Ferron Solubility, Experimental Temperature and Other Factors for the Accurate Determination of Mononuclear Aluminum Concentration in Aqueous Solution].

Ferron colorimetric method has been widely used in aluminum speciation analysis. However, some important factors that may affect the accurate determination of mononuclear Al concentration have not been studied yet. Using molar absorption coefficient ε as a key indicator, the critical issues in Al-Ferron coloring reaction system have been investigated experimentally in this paper, including different Ferron system, Ferron solubility, experimental temperature, ionic strength and the reference system. The results show that three vital factors (different Ferron colorimetric system, Ferron solubility and experimental temperature) would significantly affect the accurate measurement of mononuclear Al concentration; whereas, other two factors like ionic strength and the reference have litter influence. Base on our experimental results and statistic analysis of relevant important literatures, we suggest that optimizing colorimetric conditions and standardizing operational procedures should be paid much more attention in Ferron colorimetric assay in order to obtain the accurate measurement results.

[Progress on electrokinetic remediation and its combined methods for POPs from contaminated soils].

Electrokinetic remediation (EK) and its combined methods are emerging technologies to remove POPs from contaminated soils in situ in last decade. This paper reviews the five major kinds of electrokinetic remediation methods for POPs from contaminated soils: (1) Classic electrokinetic method; (2) Electrokinetic-Fenton method; (3) Electrokinetic remediation combining with bioremediation method; (4) Electrokinetic remediation combining with surfactants/cosolvents method; (5) Electrokinetic remediation combining with ultrasonic method. The basic principle, characteristics, application areas and research developments of those five methods are discussed respectively. The future development direction of EK remediation for POPs from contaminated soils is anticipated.

[Study on the effect of aluminum (III) on NADH in the presence of NH4Ac in aqueous solution].

This paper studied the interactions of Al (III ) and dihydronicotinamide adenine dinucleotide (NADH) in nearly neutral aqueous solutions (pH 6.5) by means of UV-Vis and 1H, 13C-NMR techniques. The results suggested that Al (III) interacts with NADH to form Al-NADH complexes by occupying the binding sites of phosphate oxygen atoms O(N)1 and O(A)1 and ribose ring hydroxyl groups, which are the potential recognition sites for substrates, coenzyme and enzyme. In the presence of NH4Ac salt buffer and with Al (III) salt solution, NADH will be marked with structural changes at the nicotinamide moiety in contrast with almost no structural changes in Tris-HCl buffer solution with Al (III) salt.

[UV-Vis spectroscopic study of aluminum-manganese cooperative effect on the melanin formation from DOPA oxidation].

The effect of aluminum and manganese ions on the melanin formation from oxidized DOPA was investigated by UV-Vis spectroscopy. In the weak acidic buffer solution (pH 5.5), aluminum and manganese ions have cooperative effect on the melanin formation. Aluminum is not a transition metal and therefore cannot initiate oxidative effect. However, manganese ions initiate the oxidation of DOPA to yield dopachrome. Aluminum ions can greatly catalyze the conversion reaction of dopachrome to form 5,6-dihydroxyindole, which is a key step in the biosynthesis of melanin. Its product is further oxidized and polymerized immediately to produce melanin. Therefore, the cooperative effect of manganese and aluminum ions increases the melanin formation from DOPA and enhances the oxidative stress.

[Assay of three kinds of aluminum fractions (Al(a), Al(b) and Al(c)) in polynuclear aluminum solutions by Al-Ferron timed spectrophotometry and demarcation of their time limits].

Al-Ferron timed spectrophotometry assay is a basic method in the study on the formation of polynuclear hydroxyl aluminum species and their transformation laws in aqueous systems. In actual working process, this methodology has some dogmatism and arbitrariness in the time limits demarcation of the three kinds of aluminum fractions (Al(a), Al(b) and Al(c)) in polynuclear aluminum solutions, which makes this kind of classification rougher, and the experimental results non-reproducible. The reason for this difference is that the specific species within Al(a), Al(b) and Al(c) have different reaction mechanism and dynamics, and that specific species of Al(b) having different OH/Al ratios have different reaction rates with ferron. In this paper, the ExpAssoc distribution was applied to quantitatively fit the Al-Ferron reaction dynamics curve, and the extrapolation method was used to survey the 1 min measured value [Al(a)] of monomeric Al, which is hard to obtain in manual manipulation. The time demarcation between Al(b) and Al(c) should reach the point of the experimental data curve up to horizontal platform. The microwave-radiated technology was used to fast assay the total aluminum concentration [Al(T)]. With these methods, the contents of monomeric Al(a), polynuclear Al(b) and gel Al(c) can be conveniently and quantitatively measured. It offers a novel method for surmounting the arbitrariness in the measurement of the three kinds of aluminum fractions and the repetitive calculation of Al(a) and Al(b).

[Speciation of aluminum in natural waters by fluorimetry].

Fluorimetric method has been proposed for the speciation of Al in natural waters, based on the different competitive complexation behavior of analytical reagent and natural organic matter to Al. With eriochrome blue black R (EBBR) or morin, the monomeric inorganic Al (Al(i)) was determined, while with 8-hydroxylquinoline, the total monomeric Al (Al(a)) was obtained. The analytical results of Al speciation in natural water are close to those by Driscoll's method. The method is simple and reliable. Fractionation of Al was realized by selecting appropriate reagents under the pH of natural water determined. The merits of this novel strategy are that the disturbance to original equilibrium of Al species is minimized and the results conform to the actual situation of natural waters.

Morin applied in speciation of aluminium in natural waters and biological samples by reversed-phase high-performance liquid chromatography with fluorescence detection.

A reversed-phase high-performance liquid chromatographic method with fluorescence detection for the determination of labile monomeric aluminium has been developed through pre-column complexation using morin as the analytical reagent. The highly fluorescent aluminium-morin complex (excitation wavelength 418 nm, emission wavelength 490 nm) was separated on a Spherisorb ODS 2 column with an eluent consisting of 30% methanol and 70% water (pH 1.0 with perchloric acid). The most remarkable point of this protocol was that only the most toxic aluminium species, that is, free aqua-aluminium ion and its monomeric hydroxo complex ions, selectively respond among various aluminium complexes. This strategy has been successfully applied to direct fractionation of the toxic aluminium in natural waters and biological samples without any pretreatment.

Determination of aluminum in environmental and biological samples by reversed-phase high-performance liquid chromatography via pre-column complexation with morin.

Morin was used as a pre-column reagent for the determination of aluminum by RP-HPLC with fluorescence detection. This method has been successfully applied to direct determination of trace Al in environmental and biological samples. The response was linear from 6 x 10(-9) to 6 x 10(-5) M with a detection limit of 2 x 10(-9) M. In addition, the different Al complexes with morin were separated by the proposed HPLC procedure and their coordination ratios were depicted by molar-ratio method. The results showed that 1:1 and 2:1 Al-morin complexes formed.