Optimization of chemical and instrumental parameters in hydride generation laser-induced breakdown spectrometry for the determination of arsenic,antimony, lead and germanium in aqueous samples

A laser induced breakdown spectrometry hyphenated with on-line continuous flow hydride generation sample introduction system, HG-LIBS, has been used for the determination of arsenic, antimony, lead and germanium in aqueous environments. Optimum chemical and instrumental parameters governing chemical hydride generation, laser plasma formation and detection were investigated for each element under argon and nitrogen atmosphere. Arsenic, antimony and germanium have presented strong enhancement in signal strength under argon atmosphere while lead has shown no sensitivity to ambient gas type. Detection limits of 1.1 mg L⁻¹, 1.0 mg L⁻¹, 1.3 mg L⁻¹ and 0.2 mg L⁻¹ were obtained for As, Sb, Pb and Ge, respectively. Up to 77 times enhancement in detection limit of Pb were obtained, compared to the result obtained from the direct analysis of liquids by LIBS. Applicability of the technique to real water samples was tested through spiking experiments and recoveries higher than 80% were obtained. Results demonstrate that, HG-LIBS approach is suitable for quantitative analysis of toxic elements and sufficiently fast for real time continuous monitoring in aqueous environments.     

The Pharmacokinetic Profiles of Pre-Operative Prophylactic Cefepime Application in Pregnant and Non-Pregnant Women Undergoing Surgical Interventions Using a Fully Validated Liquid Chromatographic Method

Pregnancy alters pharmacokinetic profile of many drugs, because of altering body volume and metabolism rate. Therefore, dosage rates and concentrations of drugs must be controlled during pregnancy. Here, we identified the pharmacokinetic profile of pre-operatively given cefepime in caesarean section and gynecological operations using a simple, rapid, cost-effective and valid liquid chromatographic method. The chromatographic separation was performed using 40 mM, pH 3.2 phosphate buffer containing 6 % methanol as mobile phase at 0.30 mL min^?1 flow rate. Gradient elution with methanol was applied to get shorter analysis time without any interference from plasma endogens. During analyses, temperature of column, autosampler and detector were set as 30, 10 and 40 °C, respectively. The detection wavelength was 260 nm and ceftizoxime was used as internal standard. At the optimum conditions, the cefepime analysis from plasma samples was completed in 7 min. Cefepime was extracted from plasma samples using perchloric acid with a very high recovery rate (99.3 %). The method was fully validated according to the Food and Drug Administration guidelines for bioanalytical method validation, and found to be selective, linear, repeatable, reproducible and robust. After validation studies, the method was applied to five caesarean-sectioned and four non-pregnant sectioned women treated with pre-operative, prophylactic single intravenous dose of cefepime (1 g Maxipime^®) in order to determine pharmacokinetic profile of cefepime. Peak serum concentrations of cefepime in caesarean-sectioned women at the arterial port after infusion was 70.11 ± 10.74 μg mL^?1. The mean elimination half-life, volume of distribution and calculated area under the concentration–time curve (AUC)_0–∞ were 1.10 ± 0.23 h, 14.22 ± 2.29 L and 101.55 ± 10.99 μg h mL^?1 for caesarean-sectioned women; and 1.14 ± 0.21 h, 14.76 ± 2.92 L and 104.71 ± 36.34 μg h mL^?1 for non-pregnant sectioned women, respectively. The area under curve, elimination half-life, maximum plasma concentration and the mean distribution volume of cefepime were not changed in case of pregnancy.     

Heterogenous Oxidation of [2.2.1] Bridged Bicyclic Alkenes with KMnO4-CuSO4.5H2O: An Alternative Ozonolysis

Seven [2.2.1] bridged alkenes were cleaved to the corresponding dialdehyde products by neutral heterogenous oxidation with KMnO₄-CuSO₄.5H₂O. While endo, endo-dimethyl bicyclo[2.2.2]oct-5-ene-2,3-dicarboxylate, [2.2.2] bridged alkene, gave the corresponding α-hydroxy ketone, endo, endo-dimethyl bicyclo[3.2.2]non-8-ene-6,7-dicarboxylate afforded a diketone product.     

Beckmann Fragmentation of Diphenylcarbamoylated N-Aryldiphenacylamine Dioximes. New Method for the Synthesis of Imidazooxadiazolones

N-Aryl-N,N-diphenacylamine dioximes were prepared by the reaction of corresponding arylamines with α-bromoacetophenone oxime in ethanol-water at room temperature. These compounds reacted with aryl isocyanates in acetonitrile to give imidazooxadiazolones 9. The probable mechanism of the reaction is discussed.     

Stereoconvergent Generation of a Contrasteric syn‐Bicyclopropylidene (=syn‐Cyclopropylidenecyclopropane) by Stille‐Like Coupling

Stereoisomerically pure endo‐ and exo‐7‐halo‐7‐(trimethylstannyl)benzonorcar‐3‐enes (=endo‐ and exo‐(1‐halo‐1a,2,7,7a‐tetrahydro‐1H‐cyclopropa[b]naphthalen‐1‐yl)trimethylstannane) 4 and 6 were selectively obtained by lithium? tin or magnesium? tin transmetalation in good yields (Scheme 2 and 3). The reaction of these compounds with copper(I) thiophene‐2‐carboxylate (CuTC) produced in both cases the corresponding C_S‐symmetric bicyclopropylidene (=cyclopropylidenecyclopropane) syn‐ 1 , a single diastereoisomer (Schemes 5 and 6). The structure of syn‐ 1 was undoubtedly elucidated by X‐ray single crystal diffraction. The coupling mechanism of the carbenoid cyclopropane is discussed (Scheme 7).     

Facile Method for 1,3‐Dipolar Cycloaddition Reaction of Azomethine Ylides: Highly Stereoselective Synthesis of Substituted Pyrrolidine Derivatives

The substituted pyrolidine derivatives with high stereoselectivity were obtained through cycloaddition reaction in the presence of a Lewis acid namely diethylzinc by solvent‐free grinding method.     

Synthesis of N,N‐Dimethylamines via Barbier–Grignard‐Type Electrophilic Amination

Aryl Grignard reagents react with N,N‐dimethyl O‐(mesitylenesulfonyl)hydroxylamine in THF under Barbier conditions at room temperature and give N,N‐dimethylanilines with high yields in a 2‐h reaction. The amination yield of in situ Grignard reagents were not lower than those of preformed aryl Grignard reagents. In situ cycloalkyl‐, allyl‐, and benzylmagnesium bromides did not react with N,N‐dimethyl O‐(mesitylenesulfonyl)hydroxylamine, except that amination of in situ n‐hexylmagnesium bromide resulted in a medium yield. Grignard–Barbier‐type amination of aryl bromides with N,N‐dimethyl O‐(mesitylenesulfonyl)hydroxylamine provides a new alternative route for the synthesis of N,N‐dimethylanilines.     

Functional silver nanostructured surfaces applied in SERS and SIMS

Present article deals with functionality of silver nanostructured surfaces prepared by potentiostatic electrochemical deposition on the paraffin impregnated graphite electrode as template‐free substrates. The effect of the electrodeposition conditions on two silver surface functions: analytical signal enhancement in Surface‐enhanced Raman spectroscopy and pre‐ionization function, applied in secondary ion mass spectrometry (SIMS) is reported. Functional silver nanostructured substrate was prepared at a potential ?850 mV with a deposition duration of 20 min. Analytical signal enhancement factors of 3.2 ×10⁵ for Raman peak at 649 cm^?1, 3.0×10⁵ for peak at 810 cm^?1 and 2.7×10⁵ for peak at 1539 cm^?1 were determined for Rhodamine 6G at deposited surface. Slight pre‐ionization effect has been observed in SIMS, and 1.2×10⁵ fold signal enhancement was established for fragment of Rhodamine 6G with m/z 429 (M‐CH₃‐Cl). Electrochemical preparation of nanostructures represents a step towards surface integration directly into miniaturized systems and sensors. Copyright © 2013 John Wiley & Sons, Ltd.     

Investigation of radiocesium biokinetics in Manila clam (Ruditapes philippinarum)

This study was carried out to better understand the biokinetics of radiocesium in clams living in sediment. The accumulation and depuration kinetics of ¹³⁴Cs were investigated in the Manila clam (Ruditapes philippinarum) under controlled laboratory conditions. The concentration factor was found to be 3.0 for ¹³⁴Cs in the whole body; however, the concentration factor in the soft part of the clams (12) was significantly higher than those in the whole body and shell (0.80). The depuration kinetics of the radionuclide were described by a two-component exponential model for the whole body. The biological half-lives in the fast and slow components were found to be 0.63 and 22.1 days, respectively. The depuration kinetics for ¹³⁴Cs in the soft parts were described by a single-component exponential model with a resultant the biological half-life of 18.0 days.