Rapid spectrophotometric determination of manganese(II) with 4-(2-thiazolylazo)-resorcinol

Summary Manganese forms a red chelate with 4-(2-thiazolylazo)-resorcinol at pH 8.8 (borate buffer), and absorbance is measured after 30 s, at 540 nm in the presence of 20%tert-butyl alcohol (by volume). The 12 complex obeys Beer's law for manganese concentration of 0.04–1.4g per ml, has molar absorptivity 4.176 x 10⁴ and Sandell sensitivity 0.0013g cm^–2. The formation constant (logK) is found to be 9.32, and relative standard deviation ±0.22%. Of the 48 ions studied for interference, only Co(II), Zn(II), Cd(II), Pb(II) and EDTA^2– are found to interfere. This method has been applied for the determination of manganese content in alloy steels.

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Spektrophotometrische Bestimmung von Mangan(II) mit 4-(2-Thiazolylazo)-resorcin

Zusammenfassung Mangan bildet bei pH 8,8 (Boratpuffer) mit 4-(2-Thiazolylazo)-resorcin ein rotes Chelat, dessen Absorbanz nach 30 sec bei 540 nm in Gegenwart von 20% tert. Butylalkohol gemessen wird. Dieser 12-Komplex entspricht bei einer Mangan-Konzentration von 0,04–1,4g/ml dem Beerschen Gesetz; seine molare Absorption beträgt 4,176 x 10⁴, die Empfindlichkeit nach Sandell 0,0013g·cm^–2. Die Bildungskonstante (log K) beträgt 9,32, die rel. Standardabweichung ±0,22%. Unter 48 untersuchten Ionen erwiesen sich nur Co(II), Zn(II), Cd(II), Pb(II) und EDTA als störend.-Das Verfahren wurde zur Bestimmung des Mangangehaltes in Stahl verwendet.

     

Rapid spectrophotometric determination of thorium(IV) with 1-(2′-thiazolylazo)-2-naphthol

Thorium(IV) reacts with 1-(2-thiazolylazo)-2-naphthol (TAN) in the presence of antipyrine to form a sparingly soluble red-coloured chelate, soluble in 36% methanol (v/v). Complexation takes place instantaneously at pH 2.4–2.8, maintained by glycine buffer. Antipyrine is found to enhance sensitivity of the complex, which is stable for 19 hours. The 12 complex exhibits maximum absorbance at 555 nm, obyes Beer's law in the concentration range from 0.32 to 6.56 g of thorium(IV) per ml, has a molar absorptivity of 3.14·10⁴ dm³/mol^–1·cm^–1 and a Sandel sensitivity of 7.4 ng·cm^–2. The formation constant (log K) is found to be 8.62 and 8.45. Interference of 57 anions and cations in the determination of thorium(IV) has been studied. From ten repeated determinations, the coefficient of variation was found to be ±0.98%. The method was successfully applied for determination of thorium content in a sample of monazite.     

Discovery and Biosynthesis of Bolagladins: Unusual Lipodepsipeptides from Burkholderia gladioli Clinical Isolates**

Two Burkholderia gladioli strains isolated from the lungs of cystic fibrosis patients were found to produce unusual lipodepsipeptides containing a unique citrate-derived fatty acid and a rare dehydro-β-alanine residue. The gene cluster responsible for their biosynthesis was identified by bioinformatics and insertional mutagenesis. In-frame deletions and enzyme activity assays were used to investigate the functions of several proteins encoded by the biosynthetic gene cluster, which was found in the genomes of about 45 % of B. gladioli isolates, suggesting that its metabolic products play an important role in the growth and/or survival of the species. The Chrome Azurol S assay indicated that these metabolites bind ferric iron, which suppresses their production when added to the growth medium. Moreover, a gene encoding a TonB-dependent ferric-siderophore receptor is adjacent to the biosynthetic genes, suggesting that these metabolites may function as siderophores in B. gladioli.     

Spectrophotometric determination of chromium(III) with 4-(2-thiazolylazo)-resorcinol

Summary The red complex formed between chromium(III) and 4-(2-thiazolylazo)-resorcinol (1 2) at pH 5.0, on heating the reactants to 90° for 45 minutes, is used for Spectrophotometric determination of chromium, the absorbance being measured at 525 nm. Beer's law is obeyed for chromium concentration of 0.06 to 1.1g per ml. Molar absorptivity is 4.98×10⁴ and Sandell sensitivity 0.001g cm^–2. This method has been applied to the determination of chromium content in steel samples.

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Zusammenfassung Der 1 2-Komplex von Chrom(III) mit 4-(2-Thiazolylazo)resorcin bildet sich bei pH 5,0 und 90° C in 45 min. Er eignet sich zur spektrophotometrischen Chrombestimmung. Die Extinktion wird bei 525 nm gemessen. Das Beersche Gesetz ist zwischen 0,06 und 1,1g Cr/ml erfüllt. Die molare Extinktion beträgt 4,98 · 10⁴, die Empfindlichkeit nach Sandell 0,0001g · cm^–2. Die Methode wurde zur Chrombestimmung in Stahlproben angewandt.

     

Measurement of tobramycin by reversed-phase high-performance liquid chromatography with mass spectrometry detection

Analysis of tobramycin faces challenges owing to its significant basicity, hydrophilicity and lack of a UV absorbing chromophore. Chromatographic methods, coupled with derivatization to introduce chromophores for tobramycin analysis, were extensively studied. A direct reversed-phase HPLC method for tobramycin analysis has not been reported. Here, we would like to report a simple LC/MS method for quantitative analysis of tobramycin in pharmaceutical formulations. Reversed-phase HPLC analysis of tobramycin was achieved using a pH stable C18 column with basic (pH 11) aqueous mobile phase (ammonium hydroxide buffer), while direct detection was carried out employing a single quadruple mass detector in negative mode via electrospray ionization. This unique separation-detection combination provided simple and specific determination of tobramycin. This method was found to be linear at a tobramycin concentration range of 0.2-0.8 mg/mL with a correlation coefficient value of 0.999. The quantitation limit and detection limit were calculated as 0.210 and 0.063 μg/mL, respectively, with 99.994% confidence. This method was successfully applied to measure tobramycin content in matrices containing tobramycin and other pharmaceutical formulation ingredients. Recoveries of 101.8, 97.8 and 106.7% were obtained for tobramycin spiked in the pharmaceutical formulation at concentrations of 1.68, 1.0 and 0.35 mg/mL, respectively. The relative standard deviations for six injections of spiked samples ranged from 0.2 to 3.2%, indicating good method repeatability.     

Analysis of trace amount of bank dye and lachrymators from exploding bank devices by solid-phase microextraction and gas chromatography-mass spectrometry

Solid-phase microextraction (SPME) is a fast, solvent-free alternative to conventional sample preparation techniques. This technique involves exposing a fused silica fiber that has been coated with a stationary phase to an aqueous solution or its headspace to selectively extract compounds from their matrix. The fiber is then removed, and the analytes are thermally desorbed in the injector of a gas chromatograph. By sampling from the headspace above sample matrices, SPME can be used to extract target analytes from very complex matrices. In this study, SPME in the headspace is used in developing a method for the dye 1-methylaminoanthraquinone (MAAQ) and two lachrymators: orthochlorobenzalmalononitrile (CS) (tear gas) and 2-chloroacetophenone (CN) (tear gas). The focus is to develop a robust method to minimize sample preparation and to reduce matrix interferences encountered by other extraction techniques. In developing the method, several fibers are studied for their affinity for the compounds of interest. Although this method is developed for qualitative analysis, the extraction time and temperature profile are thoroughly investigated to provide the optimal conditions. The use of a salt solution is evaluated to increase the partitioning of MAAQ into the headspace. Using this method, qualitative extraction is achieved for the analysis of CN, CS, and MAAQ from its matrices. CN and CS are extracted in less than 5 min, though MAAQ needed more than 15 min to achieve a reasonable response. If more sensitivity is required, the use of a salt solution increases the response of MAAQ by 90-fold.