A miniature and field-applicable multipumping flow analyzer for ammonium monitoring in seawater with fluorescence detection

In this article, a simple, economic, and miniature flow analyzer for ammonium in seawater based on the solenoid micropumps is presented. A single reagent of sodium tetraborate, ortho-phthaldialdehyde (OPA), and sodium sulfite was used and optimized applying the modified SIMPLEX method. A special-made detection cell for fluorescence detection of the reaction product isoindol-1-sulfonat was made and combined with a commercial photomultiplier tube, a long-pass optical filter, and an UV-LED as excitation light source. A LOD down to 13 nmol/L was achieved. The fabrication and application of a miniature reaction coil heating device for reaction rate enhancement is further described. The system featured an injection frequency of 32 h⁻¹ at average standard deviation of 3%.     

Contribution from a hole-conducting dye to the photocurrent in solid-state dye-sensitized solar cells

The hole transporting medium in solid-state dye-sensitized solar cells can be utilized to harvest sunlight. Herein we demonstrate that a triphenylamine-based dye, used as hole-transporting medium, contributes to the photocurrent in a squaraine-sensitized solid-state dye-sensitized solar cell. Steady-state photoluminescence measurements have been used to distinguish between electron transfer and energy transfer processes leading to energy conversion upon light absorption in the hole-transporting dye.     

Influence of Gold Nanoparticle Film Porosity on the Chemiresistive Sensing Performance

The porosity of 1‐hexanethiol‐functionalised gold nanoparticle films was assessed and utilised as chemiresistor sensors. Electrochemical capacitance measurements showed that the accessibility of electrolytes of different ionic strengths into the pores depended on the thickness of the electric double layer formed. A large variation in capacitance was measured in 0.01–1000 mM NaClO₄, implying a wide pore size distribution. The change in morphology of the nanoparticle films upon storage in air, water and ethanol for two weeks was investigated. There was a significant decrease in the electrochemical capacitance at high electrolyte concentrations for the ethanol‐stored films compared to the freshly‐prepared films suggesting a decrease in the number of small pores of radii in the range of 0.3–3 nm. This was further supported by optical topographical measurements where a decrease in the thickness of ethanol‐stored films was observed relative to the freshly‐prepared films. The porous nature of the nanoparticle films was found to have an effect on the chemical sensing behaviour. When used as chemiresistor sensors, for the detection of heptane in water, the ethanol‐stored films provided larger resistance changes and longer response times. This suggests that the more densely packed ethanol‐stored films provided more sites that enabled film swelling, and that diffusion of the analyte occurred through the narrower water‐filled pores. This demonstrates the effect of different storage conditions on film morphology and subsequently sensor response.     

Metabolism of levamisole and kinetics of levamisole and aminorex in urine by means of LC-QTOF-HRMS and LC-QqQ-MS

The antihelminthic drug Levamisole can enhance cocaine effects by conversion into the amphetamine-like drug aminorex. We describe an LC-MS method for the determination of levamisole and its metabolite aminorex in human urine. Selectivity is given, calibration curves were linear within the calibration range 2.5–250 ng/mL; limits of the method were LoD 0.51 ng/mL, LoQ 1.02 ng/mL for levamisole and LoD 0.65 ng/mL, LoQ 0.76 ng/mL for aminorex. Precision data was in accordance with the guidelines (intraday precision for aminorex ranged between 5.75 and 11.0 % for levamisole between 8.36 and 10.9 %; interday precision for levamisole 10.9–16.9 % and for aminorex 7.64–12.7 %; accuracy data for levamisole ?1.96 to –14.3 % and for aminorex?11.9 to–18.5 %). The validated method was successfully applied to study the urinary excretion of levamisole after the administration of 100 mg of levamisole orally. Levamisole and aminorex could be detected in post-administration urine samples. Levamisole could be detected up to 39 h after ingestion, while aminorex was detectable up to 54 h. Maximum aminorex concentrations were 45 ng/mL urine. Further metabolites of levamisole after oral ingestion by means of liquid chromatography hybrid quadrupole time-of-flight high-resolution mass spectrometry (LC-QTOF-HRMS) were identified. Only 0.5 % of the ingested drug was quantified as unchanged levamisole in urine. Besides aminorex, five isomers of aminorex and 4 hydroxy-metabolites of aminorex or its isomers were found. Furthermore, levamisole is also hydroxylated and eliminated free or conjugated with sulfate or glucuronide into urine.     

Eosin Y (EY) Photoredox‐Catalyzed Sulfonylation of Alkenes: Scope and Mechanism

Alkyl‐ and aryl vinyl sulfones were obtained by eosin Y (EY)‐mediated visible‐light photooxidation of sulfinate salts and the reaction of the resulting S‐centered radicals with alkenes. Optimized reaction conditions, the sulfinate and alkene scope, and X‐ray structural analyses of several reaction products are provided. A detailed spectroscopic study explains the reaction mechanism, which proceeds through the EY radical cation as key intermediate oxidizing the sulfinate salts.     

Stereoselective Michael Addition of Carbonyl Compounds to ( E )-β-Nitrostyrene Catalysed by N -Toluensulfonyl-l -proline Amide in Ionic Liquids

Summary. N-Toluensulfonyl-l-prolin amide was tested as catalyst in the enantioselective Michael addition of carbonyl compounds to (E)-β-nitrostyrene in nine ionic liquids under different reaction conditions. The reaction rates and enantioselectivities were strongly dependent on the ionic liquids. Change of enantioselectivity was observed too and it is attributed to both the cation and the anion of ionic liquid. The best yields (up to 98%) and enantioselectivity (70% ee) of product were obtained in a basic ionic liquid [bmim]BF₄ at room temperature.     

Tumor selectivity at short times following systemic administration of a liposomal temoporfin formulation in a murine tumor model

Meso-tetra(hydroxyphenyl)chlorin (mTHPC) (INN: Temoporfin) is one of the most potent photodynamically active substances in clinical use. Treatment protocols for Temoporfin-mediated photodynamic therapy often rely on drug-light intervals of several days in order for the photosensitizer to accumulate within the target tissue, though tumor selectivity is limited. Here, the mTHPC localization was studied at 2-8 h following systemic administration of a liposomal Temoporfin formulation (0.15 mg kg(-1) b.w.) in HT29 human colon adenocarcinoma in NMRI nu/nu mice. Photosensitizer distribution within tumor and internal organs was investigated by means of high performance liquid chromatography following chemical extraction, as well as in situ fluorescence imaging and point-monitoring fluorescence spectroscopy. For tumor tissue, the Temoporfin concentrations at 4 h (0.16+/-0.024 ng mg(-1)) and 8 h (0.18+/-0.064 ng mg(-1)) were significantly higher than at 2 h (0.08+/-0.026 ng mg(-1)). The average tumor-to-muscle and the tumor-to-skin selectivity were 6.6 and 2, respectively, and did not vary significantly with time after photosensitizer injection. In plasma, the Temoporfin concentration was low (0.07+/-0.07 ng mg(-1)) and showed no significant variation with time. Our results indicate a rapid biodistribution and clearance from the bloodstream. Within the same type of organ, data from both fluorescence methods generally exhibited a significant correlation with the extraction results.     

Synthesis and peptide-binding properties of a luminescent pyrimidine zinc(II) complex

The synthesis and peptide-binding properties of a Zn(II)nitrilotriacetate complex substituted with pyrimidine hydrazine amides are reported. The metal complex provides millimolar binding affinity in aqueous buffer to peptides bearing N-terminal His. The pyrimidine heterocycles intermolecularly interact with the bound peptide and quench the emission of nearby Trp residues by energy transfer.