A new sensitive and specific test for vanadium with sulphosalicylic acid

A very sensitive and specific test for vanadium^V is described using sulphosalicylic acid as reagent. When this reagent is brought into contact with solid vanadium^V (a drop of the test solution evaporated to dryness on a watch glass) in the presence of concentrated sulphuric acid or 80% syrupy phosphoric acid, a blue colour is developed. Using this colour reaction, it is possible to detect 0.05 μg of vanadium^V in 0.05 ml of test solution. Aluminium^III, arsenic^V, beryllium^II, cadmium^II, chromium^III, chromium^VI, copper^II, iron^III, molybdenum^VI, nickel^VI, tungsten^VI, uranium^VI and vanadium^IV do not interfere with this colour test, although some of them are known to form coloured complexes with sulphosalicylic acid under different conditions. Reducing agents like iron^II, uranium^IV, molybdenum^V and hydroquinone discharge the colour. The colour of the vanadium^V-sulphosalicylic acid compound is also discharged if the temperature is raised to 60°, though it reappears on cooling.     

Miniaturized RPLC for the rapid determination of total tryptophan in pediatric plasma samples

Summary A 8.3cm column packed with 3μm C₁₈ particles was used for the quantitative analysis of total tryptophan in plasma. The plasma samples were deproteinized with cold perchloric acid and 5–20μl of the plasma extract were injected into the RPLC column The tryptophan was readily separated from other plasma components in 5 minutes using isocratic elution. Thus the method can be readily automated. The minimum detection limit was 5pmoles using UV detection, and 1 pmole using fluorescence detection. Since low concentrations of total tryptophan in small volumes (⩽ 500μl) of plasma can be determined reproducibly and rapidly, this fast RPLC method can be used in pharmaceutical and clinical laboratories for newborn, and infant and pediatric samples.     

A concise approach for the total synthesis of pseudolaric acid A

A new strategy for the stereoselective total synthesis of natural product pseudolaric acid A (1) was accomplished in 16 steps from commercially available starting material, featuring a samarium diiodide (SmI(2))-mediated intramolecular alkene-ketyl radical cyclization and a ring-closing metathesis (RCM) reaction to stereoselectively cast the unusual trans-fused [5-7]-bicyclic core of pseudolaric acid A (1).     

A new approach to the effective preparation of plasma samples for rapid drug quantitation using on-line solid phase extraction mass spectrometry.

A procedure that permits rapid development of an optimized solid phase extraction (SPE) method for the analysis of drugs in plasma by on-line solid phase extraction-mass spectrometry (SPE-MS) has been developed. This procedure employs the concept of manipulating the pH and the percentage of organic solvent in the chromatographic mobile phase to affect the retention behaviors of both the matrix components and the analytes of interest. This resulted in the effective removal of matrix interferences from biological samples during SPE. During a the method development, only generic HPLC gradient approaches were needed, and multiple samples were pooled so that several SPE methods could be investigated at once. The analysis time per sample was 1.3 minutes. Thus, the time involved in the entire method development (analysis of a set of samples) was less than one hour. With the knowledge of the retention behaviors of the analytes with respect to the pH and the percentage of organic, it was then possible to compose an optimized SPE-MS method. This method consisted of a base/organic and then an acid/organic washing step, followed by a rapid gradient elution step. Due to the rigorous washing procedure, most matrix interferences were removed, and analytes eluted off the SPE sorbent suffered from very little matrix interference. Thus, quantitation of drugs in plasma by a single quadrupole mass spectrometer could be accomplished, something that was not possible when only a generic gradient was used for on-line SPE-MS. In addition, both external and internal calibration curves could be obtained for the concentration range from 5 to 500 ng/mL with correlation coefficients of 0.99 (using 1/x as a weighting factor) and relative standard deviations (RSDs) less than 10%. The results achieved were comparable to those obtained by the use of a triple quadrupole mass spectrometer. Moreover, the robustness of the method was tested by continuously injecting plasma samples. During 136 runs, the absolute peak area variation for these three basic drugs was less than 15% without taking the signal variation from the mass spectrometer into account. Significantly, the on-line developed method can be directly transferred to a 96-well format SPE plate.     

Electrophoretic separation of tryptophan enantiomers in biological samples.

A method for the determination of D- and L-tryptophan (Trp) in biological samples is described. The amino acid enantiomers were precolumn-derivatized with a fluorescence tagging reagent, naphthalene-2,3-dialdehyde (NDA). In the presence of hydroxypropyl-gamma-cyclodextrin (HP-gamma-CD) as the chiral selector, NDA-tagged Trp enantiomers were well resolved by micellar electrokinetic chromatography (MEKC). Using laser induced fluorescence (LIF) detection, a detection limit of 3.3 x 10(-8) M Trp was obtained. The method was applied to the determination of Trp enantiomers in biological samples including human urine and cerebrospinal fluid (CSF), rat brain tissue, and Aplysia ganglia. No interference from other amino acids or the endogenous compounds in the sample matrices was observed. D-Trp was found at the sub-microM level in human urine samples collected from several healthy subjects. Further, the determination of DL-Trp residues in small quantities (10 microg) of peptides after acid hydrolysis is demonstrated.     

A new approach for the total synthesis of spilanthol and analogue with improved anesthetic activity

A 5-step synthesis of spilanthol (affinin) is reported, where the route features complete control of alkene geometry during the assembling of the double bonds, with the use of a Sonogashira cross-coupling reaction, a Z-selective alkyne semi-reduction and a HWE olefination reaction as the key steps. A simplified analogue was also prepared in 4 steps. Both compounds were found to permeate dermatomed pig ear skin through an in vitro Franz-type diffusion cell. The simplified analogue presented a superior anesthetic effect in vivo, using the tail flick model, when compared to spilanthol and to the commercial standard EMLA^®. These results suggest that both spilanthol and its analogue could be useful as a topical anesthetic in clinical practice.     

Immunoenzyme assay for the determination of prostatic acid phosphatase in plasma samples

Conclusion The determination of PAP in plasma samples with the new IEA improves the analytical specifity and appears to be superior to the serum RIA method. It allows a clearer distinction of prostatic carcinoma patients, especially in earlier stages of the disease, from those with benign prostatic hyperplasia. Although it, too, certainly cannot be regarded as suitable for a general screening for prostatic cancer, it may serve as an useful additional aid in the diagnosis and therapy-monitoring of the disease.

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Immunoenzymtest zur Bestimmung der prostataspezifischen sauren Phosphatase in Plasmaproben

     

A new approach towards acid sensitive copolymer micelles for drug delivery

A new micellar system capable of selective release of its contents under mildly acidic conditions is described.     

A new approach to study cadmium complexes with oxalic acid in soil solution

This study presents a new analytical approach for the determination of heavy metals complexed to low-molecular-weight-organic acids in soil solutions, which combines the sensitivity of differential pulse anodic stripping voltammetry (DPASV) with the molecular insight gained by electrospray ionization mass spectrometry (ESI-MS). The combination of these analytical methods allows the investigation of such complexes in complex matrixes. On the voltammograms of the soil solutions, in addition to the expected complexes of oxalic acid with cadmium and lead, respectively, also peaks belonging to mixed complexes of cadmium, lead, and oxalic acid (OAH(2)) were observed. In order to verify the possible formation of complexes with OAH(2), aqueous solutions of OAH(2) with traces of Cd(II) were investigated as model systems. Signals corresponding to several distinct molecular complexes between cadmium and oxalic acid were detected in the model solutions using negative-ion ESI-MS, which follow the general formula [Cd(n)(X,Y)((2n+1))](-), where n is the number of cadmium atoms, X=Cl(-), and Y=OAH(-). Some of these complexes were also identified in the ESI mass spectra taken from the soil solutions.     

A new laser ablation system for quantitative analysis of solid samples with ICP-MS.

The laser ablation (LA) method is an effective technique for quantitative analysis. In the present work, a new LA system was developed for the high-sensitivity analysis of metal materials using inductively coupled plasma mass spectrometry (ICP-MS). This system consists of a high-frequency Q-switched laser and 2 scanning mirrors for scanning the ablation spot in an adequately large area of the specimen without vacant spaces. The influence of elemental fractionation (non-stoichiometric generation of vapor species) can be eliminated by repetitive irradiation of this pattern on the same area. Particles generated with an average laser power of 0.6 W with the developed LA system gave intensity and stability substantially similar to that of a 500 microg/ml solution steel sample in solution ICP-MS. The analytical performance of the developed LA-ICP-MS was compared with that of a solution ICP-MS using NIST steel SRMs. The performance of the newly-developed system is comparable to that of conventional solution ICP-MS in both accuracy and precision. The correlation coefficients between the contents and the intensity ratios to Fe were over 0.99 for most elements. The relative standard deviation (RSD) obtained by LA-ICP-MS revealed that this system can analyze iron samples with good precision. The results of ultra trace level analysis of high-purity iron showed that developed LA-ICP-MS is capable of analyzing ppm concentration levels with a 20 - 30 ppb level standard deviation. The detection limit was on the order of 10 ppb for most elements.     

A new total synthesis of (±)-clavulanic acid

Regioselective reactions at the terminal double bond of the racemic azetidinone dienylether (4), provides a source of clavulanic acid and several analogues.     

Determination of acid leachable and total plutonium in large soil samples

Global fallout plutonium, most of which was produced by large thermonuclear tests injecting submicron particles into the stratosphere, can be readily extracted from soil by strong acid leaching. Some nuclear tests conducted at the Nevada Test Site (NTS) produced fallout in offsite regions that does not yield its total plutonium content to an acid leach. We theorize that those detonations occurred near the desert surface and incorporated fused silicate soil particles, many >1 m, into the mushroom cloud and stem. We have assembled a radiochemical procedure to insure the complete dissolution of plutonium in 50g of acid leached soil residue. The results of a complete analysis of the leachate and leached residue from soil collected near NTS and the eastern United States illustrate the impact of these particles on the plutonium values obtained by the two methods.     

A new approach for the sequential injection spectrophotometric determination of the total antioxidant activity

A sequential injection system based on the ABTS (2,2′-azino-bis-(3-ethylbenzothiazoline-6-sulphonic-acid) methodology was developed. The proposed method, incorporating a mixing chamber in the side port of the selection valve, was evaluated to measure the total antioxidant activity of several beverages and foods.The ABTS⁺ is generated by oxidation of ABTS with potassium persulfate and is reduced in presence of hydrogen-donating antioxidants converting into a colourless product. The applicability of the developed method was tested by measurement of the antioxidant activity of pure compounds as well as by analysing complex food and beverage samples. The antioxidant activity was presented as l(+) ascorbic acid equivalence. The values obtained by this methodology were not significantly different from the results obtained by the original spectrophotometric ABTS assay. For most of the studied antioxidants, antioxidant activity varied with pH and dilution. The proposed SIA system is suitable for screening direct or diluted total antioxidant activity of pure compounds or food samples.     

A new approach to 3-hydroxyquinoline-2-carboxylic acid

Quinoline-2-carboxylic acid derivatives cap the N-terminal of several natural cyclic peptides with antitumoral activity. A new and convenient route for the preparation of 3-hydroxyquinoline-2-carboxylic acid is discussed. The preparation of the title compound is accomplished by a four-step procedure from 3-hydroxyquinoline via MOM protection of the hydroxyl group, followed by a 1,2-addition of methyllithium to the quinoline ring with concomitant oxidation, and, finally, a two-step oxidation procedure for the transformation of the methyl group to the carboxylic acid along with removal of the MOM group. Furthermore, different attempts to its preparation led to other interesting quinolines, such as 2-chloro-3-hydroxyquinoline-4-carboxylic acid and a protected 3,3′-dihydroxy-2,2′-biquinoline.     

Coupling pervaporation to AAS for inorganic and organic mercury determination. A new approach to speciation of Hg in environmental samples

The design and development of a new approach for Hg speciation in environmental samples is described in detail. This method, consisting of the coupling of pervaporation and atomic absorption spectrometry, is based on a membrane phenomenon that combines the evaporation of volatile analytes and their diffusion through a polymeric membrane. It is proposed here as an alternative to gas chromatography for speciation of inorganic and organic Hg compounds, as the latter compounds are volatile and can be separated by applying the principles mentioned above. The interest of this method lies in its easy handling, low cost, and rapidity for the analysis of liquid and solid samples. This method has been applied to Hg speciation in a compost sample provided by a waste water treatment plant.