Simultaneous spectrophotometric determination of phenanthridine, phenanthridinone and phenanthridine N-oxide using multivariate calibration methods

The multivariate calibration methods, partial least squares (PLS) and principle component regression (PCR) have been used to determine phenanthridine, phenanthridinone and phenanthridine N-oxide in spiked human plasma samples. Resolution of binary and ternary mixtures of analytes with minimum sample pre-treatment and without analyte separation has been successfully achieved analyzing the UV spectral data. The net analyte signal (NAS) concept was also used to calculate multivariate analytical figures of merit such as limit of detection, selectivity and sensitivity. The simultaneous determination of three analytes was possible by PLS and PCR processing of sample absorbance in the 210–355 nm region. Good recoveries were obtained for both synthetic mixtures and spiked human plasma samples.     

Mesoporous nanocrystalline MgAl2O4: A new heterogeneous catalyst for the synthesis of 2,4,6-triarylpyridines under solvent-free conditions

In this paper, one-pot synthesis of 2,4,6-triarylpyridine by condensation of subsisted acetophenone (II), aromatic aldehydes (I), and ammonium acetate (III) in the presence of nanocrystalline MgAl₂O₄ as a new heterogeneous catalyst under solvent-free conditions is reported. Advantages of this method are the use of spatially-hindered aldehydes such as 2-methoxy-, 2-fluoro-, and 2-chlorobenzaldehydes, a new nanocatalyst with high surface area, shorter reaction time, easier workup, higher yield, and its environmental friendliness. The performance of this reaction under solvent free conditions using heterogeneous catalysts like MgAl₂O₄ could enhance its efficiency from an economic as well as green chemistry point of view.     

Trans‐3,5‐dihydroperoxy‐3,5‐dimethyl‐1,2‐dioxalane/HBr System as New,Effective, Mild and Non‐toxic Reagent for Synthesis of 2‐Aryl‐1H‐benzothiazoles and 2‐Aryl‐1‐arylmethyl‐1H‐benzimidazoles

Ttrans‐3,5‐dihydroperoxy‐3,5‐dimethyl‐1,2‐dioxalane has been used as new, effective, solid, inexpensive and nontoxic oxidant for in situ generation of Br⁺ from HBr. This system has been applied as catalyst for synthesis of 2‐aryl‐1H‐benzothiazoles and 2‐aryl‐1‐arylmethyl‐1H‐benzimidazoles at room temperature in excellent yields and high purity.     

Noncontact optogalvanic signal detection in DC discharge CO<Subscript>2</Subscript> lasers

A new noncontact method for detecting optogalvanic signals in DC discharge CO₂ lasers is reported. The presented technique is based on the detection of potential difference variations through a capacitor comprised of a discharge plasma column and a coaxial or parallel conductor. The obtained optogalvanic signals exhibit better responsivity and pulse shape in comparison with other conventional techniques; in addition, they are detectable as far as 3 m from a signal source.     

Development of a dispersive liquid–liquid microextraction method for determination of palladium in water samples using dicyclohexano-18- crown-6 as extracting agent

A new separation procedure for determination of palladium using dispersive liquid–liquid microextraction with dicyclohexano-18-crown-6 as complexing reagent was developed. In this method, potassium–dicyclohexano-18-crown-6 was used as a hydrophobic complex for the microextraction of palladium as PdCl₄ ^2? complex ion. The main factors affecting DLLME efficiency, such as type and volume of extractant and disperser solvent, concentration of chelating reagent, concentration of KCl and pH were optimized. Under the optimal conditions, the limit of detection for palladium was 16.0 ng mL^?1 with enrichment factor of 138. The present method was applied to the determination of palladium in water samples with satisfactory analytical results. The method was simple, rapid, cost efficient and sensitive for the extraction and preconcentration of palladium.     

Ambient analysis by thermal desorption atmospheric pressure photoionization

Ambient mass spectrometry has attracted substantial attention in recent years. Among ambient ionization methods, thermal desorption ionization stands out because of two attributes: (1) simplicity, rendering the technique suitable for in-field applications, and (2) ability to couple with a variety of gas-phase ionization methods thereby broadening the range of molecules that can be analyzed with this method. Here, we report on improving the performance of a direct analysis in real time (DART) source by implementing atmospheric pressure photoionization (APPI) downstream of the desorption region. At identical desorption and ion sampling conditions, APPI leads to detection of radical molecular ions from non-polar compounds that are absent from the spectra generated by DART alone. Moreover, a factor of 3–5 improvement in sensitivity is observed using APPI for positive ions commonly detected by DART and DART-APPI. Using helium and nitrogen as desorption gases, APPI shows identical performance regardless of desorption gas type. In contrast, a dramatic decrease in sensitivity is observed for DART operated with nitrogen compared to DART with helium. Comparable performance for DART and DART-APPI are observed in negative ion mode, although both show a drastic improvement in the absence of the Vapur interface. This interface creates a differentially pumped chamber prior to inlet of the mass spectrometer and reduces the mass spectrometer gas load when helium is used as desorption gas.