Determination of platinum, palladium and rhodium in biological and environmental samples by low temperature electrothermal vaporization inductively coupled plasma atomic emission spectrometry with diethyldithiocarbamate as chemical modifier

A novel method for inductively coupled plasma atomic emission spectrometry (ICP-AES) determination of trace amounts of Pt(II), Pd(II) and Rh(III), based on gaseous compounds introduction into the plasma as their diethyldithiocarbamate complexes by electrothermal vaporization (ETV), was developed. At the temperature of 1100 °C, the trace amounts of Pt, Pd and Rh were vaporized into plasma. The factors affecting the formation of the chelates and their vaporization behaviors, such as ashing temperature and time, vaporization temperature and time, pH and the concentration of chelating reagents were studied in detail. Under the optimized conditions, the limits of detection (LODs) (3σ) of Pt, Pd and Rh for tested solutions were 5.4, 1.4 and 0.8 ng ml⁻¹, and for actual sample (auto-catalyst NIST SRM 2557) were 0.27, 0.07 and 0.04 μg g⁻¹, respectively. The relative standard deviations (RSDs) for Pt, Pd and Rh were 1.4, 2.6 and 2.4% (C_Pt=0.5 μg ml⁻¹, C_Pd,Rh=0.25 μg ml⁻¹, n=7), respectively. The linear ranges of calibration graphs for Pt, Pd and Rh cover three orders of magnitude. Compared with conventional electrothermal vaporization technique, using the reagent of diethyldithiocarbamate as chemical modifier could not only enhance the analytical sensitivities, but also reduce the vaporization temperature. By combination with a separation/preconcentration step, the proposed method had been successfully applied to the analysis of the artificial seawater, tap water and urine with recoveries ranging from 91 to 106%. The two certified reference material meager platinpalladium ore GBW 07293 and auto-catalyst NIST SRM 2557 was also analyzed for validation, and the determined values obtained were in good agreement with the certified values.     

Systematic and statistical errors in quantitative evaluation using TLC and HPTLC. 2. Internal and external standard methods

The error propagation is given for routine analysis by in situ evaluation in TLC using the methods with internal or external standard. The internal standard method will need four different measurements of peak height or area, while the external standard method uses only two measurements. Therefore in the latter case the error of the spotting volume will cause errors in the determined concentration. By error propagation it can be shown, that the internal standard method gives better results, if the error in measuring peak height or area is less than the error of the spotting volume.     

Systematic and statistical errors in quantitative evaluation in TLC and HPTLC. 1. Evaluation by graphic methods

The paper discusses errors and error propagation in respect of graphic methods in quantitative in situ measurements in TLC. An error of 0.3% is possible by measuring only peak height if optimal conditions are chosen. This is in good agreement with analysis done practically which gives errors in the order of 0.3–0.6%. If the peak area is evaluated using the approximation peak height × half width, the error is in the order of 0.6%, but in real experiments only 1.5% had been found. Systematic errors in determining peak heights are introduced by the time constant of the amplifiers and the recorder.     

H2 production with low CO selectivity from photocatalytic reforming of glucose on metal/TiO2 catalysts

H₂ with low CO concentration is produced via photocatalytic reforming of glucose (as a representative of biomass component) on metal/TiO₂ catalyst (metals: Pt, Rh, Ru, Ir, Au, Ni, Cu). It is shown that the loaded metals generally enhance the rate of H₂ production, while they depress the CO selectivity. Both H₂ production and CO selectivity are strongly dependent on the kind of deposited metals on TiO₂. For example, Rh/TiO₂ catalyst is found to be most active for H₂ production while with the most extremely low CO concentration from the photocatalytic reforming of glucose. Supported by the National Natural Science Foundation of China (Grant No. 20403018, 20503034), National Basic Research Program of China (Grant No. 2003CB214504), and Knowledge Innovation Program of the Chinese Academy of Sciences (DICP K2006E2)     

Separation of nebramycin components by ion-exchange thin-layer chromatography

A thin-layer chromatographic method on chromatoplates coated with Dowex 50 × 8 ion-exchange resin, suitable for the separation of 5 nebramycin components, was developed.     

Studies of correlation between chemical structure and Rf-value in high performance TLC

Correlation between chemical structure and Rf-values was studied in the case of aniline and its derivatives using high performance TLC and a U-chamber. The characteristic group constants referring to each substituent were determined by chromatographing derivatives with one substituent and aniline in toluene and dibutyl ether respectively. On the basis of these constants the R_M and Rf values of derivatives with more substituents were calculated. Comparing the calculated and measured values good agreement was found.     

HPLC of fatty acid esters of mono- and polyhydric alcohols. Part 1: Analytical separation

This paper shows how simply and yet very rapidly fatty acid esters of monohydric alcohols, but particularly partial and full fatty acid esters of fully hydric alcohols can be separated and determined by means of high-pressure liquid chromatography on LiChrosorb RP-8 with methanol/water. We have separated quantitatively the methylesters of the fatty acids C_8:0 to C_22:0 and C_24:0, the i-propyl-, i-butyl-, n-hexyl- and i-octyl-esters of the even-numbered fatty acids C_8:0 to C_18:0, mono- and difatty acid esters of the 1,3-bis-(2-hydroxyethyl)-5,5-dimethyl-hydantoin, mono-, di- and triesters of the trimethylolpropane as well as the tetraesters of the penta-erythrite.     

Comparison of optical in-situ scanning of conventional and high-performance thin-layer chromatograms

Conventional TLC, linear and circular HPTLC are compared by using In-situ reflectance measurements. Chromatographic resolution, time requirement and reproducibility of quantitative scanning of the different TLC methods are investigated by means of three separation problems: benzodiazepines, corticosteroids, polycyclic aromatic hydrocarbons. In all three application examples, which were chosen without prejudice, the circular developing mode with subsequent quantitative scanning showed certain advantages over the corresponding linear HPTLC techniques. These were in the case of

• Benzodiazepines: Better reproducibility of quantitative assessment.
• Corticosteroids: Better resolution and slightly better quantitative reproducibility.
• Polycyclic aromatic hydrocarbons: Chromatography considerably faster.

     

Use of blotting-paper collectors for the separation and X-ray fluorescent determination of traces of heavy metals (Cu, Hg, Ag) in water and waste water

Summary Traces of Hg, Ag and Cu were separated in the range of 0.5–500 g with blotting-paper collectors and were subsequently determined directly with energy dispersive X-ray fluorescence. For comparison, spectrophotometric determinations were carried out as well. The results were in good agreement. The collectors contained 0.2 mM ZnS, in case of Ag a thioureide collector was also employed. Limits of detection were 0.2 g Hg, 0.4 g Cu and 0.15 g Ag for the ZnS collector and 0.13 g Ag for the thioureide collector.

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Verwendung von Flie\papier-Kollektoren zur Abtrennung und röntgenfluorescenzspektrometrischen Bestimmung von Schwermetallspuren (Cu, Hg, Ag) in Wasser und Abwasser

Zusammenfassung Hg, Ag und Cu im Bereich von 0,5–500 g wurden auf Flie\papier-Kollektoren abgetrennt und direkt durch energiedispersive Röntgenfluorescenzanalyse bestimmt. Die Ergebnisse wurden durch Spektralphotometrie überprüft. Die Kollektoren enthielten 0,2 mM ZnS, für Ag statt dessen auch Thioureid. Alle Ergebnisse waren in guter übereinstimmung. Die Nachweisgrenzen für den ZnS-Kollektor betrugen 0,2 g Hg, 0,4 g Cu, 0,15 g Ag; für den Thioureid-Kollektor 0,13 g Ag.

     

Rapid biosynthesis of silver nanoparticles from Bacillus megaterium (NCIM 2326) and their antibacterial activity on multi drug resistant clinical pathogens

The notion to fight against multi drug resistant pathogens is a great deal in the field of nanomedicine. The identifiable antimicrobial action of metal bionanoparticles on many microorganisms is reported earlier. As silver bionanoparticles (Ag-BNPs) are known to have efficient antibacterial properties they are synthesized in ecofriendly and biocompatible way. The present study is focused on the extracellular biosynthesis of highly stable Ag-BNPs from bacterial strain Bacillus megaterium (NCIM 2326) by bio-reduction of silver ion using the culture supernatant, and to determine the antibacterial efficacy on multi drug resistant clinical pathogens such as Streptococcus pneumoniae and Salmonella typhi. The biosynthesis process is rapid and Ag-BNPs are formed within few minutes if AgNO(3) comes to contact with cell filtrate. Furthermore the synthesized Ag-BNPs are characterized by UV-vis spectroscopy, Atomic Force Microscopy (AFM), Thin Layer Chromatography (TLC) and Fourier Transform Infrared Spectroscopy (FTIR).     

Advanced separation methods of food anthocyanins,isoflavones and flavanols

In recent years, increasing knowledge of the positive health effects of food polyphenols has prompted the need to develop new separation techniques for their extraction, fractionation and analysis. This article provides an updated and exhaustive review of the application of counter-current chromatography, high performance liquid chromatography, capillary electrophoresis, and their hyphenation with mass spectrometry to the study of food polyphenols. Flavonoids constitute the largest class of polyphenols, widely spread in the plant kingdom and common in human diet which has been the most widely studied with respect to their antioxidant and biological activities. The main subgroups are anthocyanins, catechins, isoflavones, flavonols and flavones. They are reported to exhibit antioxidant, anti-carcinogenic, anti-inflammatory, anti-atherogenic, anti-thrombotic, and immune modulating functions, among others. Since red fruit anthocyanins, soy isoflavones and flavanols from grapes and teas are currently the most used phenolic compounds for producing new nutraceuticals and functional foods, this review is focused on these three flavonoid groups.     

Glyoxal dithiosemicarbazone as a complexing and chromogenic spray reagent in inorganic TLC

Summary Systematic TLC separations, identification of cations and the determination of the limits of their identification on microcrystalline cellulose layers, incorporating glyoxal dithiosemicarbazone (H₂-GDTS) as a spray reagent have been worked out. Metal-GDTS complexes have also been separated on silica gel G support. Detection called for no spray reagent, owing to the intense and characteristic colours of the complexes.     

MBAMT,a new locating and chelating agen in TLC and ring colorimetric determination of Cu(II), Co(II), Ni(II), Pd(II), Pt(IV), and Rh(III)

Summary Synthesis of MBAMT (3-methyl-4-benzylideneamino-5-mercapto-1,2,4-triazole) and its IR and NMR spectral data are reported. The high stability of the characteristically coloured chelates with Cu(II), Co(II), Ni(II), Pd(II), Pt(IV) and Rh(III) has been made the basis for their efficient ascending TLC separations on silica gel G layers, when present together. Results of four different solvent systems are included to assess efficient resolution of the chelates along with their limits of identification and separation. TLC separations, followed by the ring colorimetric determination of the six metal ions (as ternary mixtures) are tabulated.MBAMT=3-methyl-4-benzylideneamino-5-mercapto-1,2,4-triazole.