Application of Doehlert design in optimizing the determination of degraded products of nerve agents by ion-pair liquid chromatography electrospray ionization tandem mass spectrometry

A qualitative method was developed for the determination of degraded products of nerve agents by using ion-pair liquid chromatography electrospray ionization tandem mass spectrometry (IP-LC-ESI-MS(n)). Generally, alkylphosphonic acids (APAs) and O-alkyl alkylphosphonic acids (AAPAs) give deprotonated molecular ion [M-H](-) in negative mode. Interestingly, first time we obtained the molecular radical anion [M](.-) of phosphonic acids in negative mode by using tri-n-butyl amine as an ion-pairing agent. We interpreted this observation as an indication of electrochemical reduction of phosphonic acids in electrospray needle. Three variables such as sheath gas flow, electrospray needle voltage and pH of the mobile phase were investigated to enhance the molecular radical anion [M](.-) signal of each analyte. The Doehlert design was used to obtain the region in which the optimum value of such variables is simultaneously achieved. Limit of detection achieved was 0.5 microg mL(-1) for AAPAs and 10 microg mL(-1) for APAs. Excellent precision was observed with less than 8.61% RSD. Finally, the method was applied for the detection of ethyl methylphosphonic in aqueous extract of soil sample.     

Development and validation of rapid ion-pair RPLC method for simultaneous determination of certain B-complex vitamins along with vitamin C

A rapid, simple, and accurate ion-pair RPLC method has been developed for simultaneous analysis of vitamin C and major B-complex vitamins. An RP C18 column thermostated at 30 degrees C was used with gradient elution of mobile phase comprising 10 mM potassium dihydrogen phosphate buffer (containing 3 mM sodium hexane-1-sulfonate, adjusted to pH 2.80 with o-phosphoric acid) and methanol at a flow rate of 1.0 mL/min to achieve the best possible separation and resolution of all vitamins in about 11.00 min. The detection was performed at 274 nm. The method has been implemented successfully for simultaneous determination of vitamins present in 12 multivitamin/multimineral pharmaceutical preparations, as well as in human urine. Typical validation characteristics were evaluated in accordance with International Conference on Harmonization guidelines. Good linearity over the investigated concentration levels was observed. Intraday repeatability was < or = 2.0%, and interday variation was < or = 2.6%, for all vitamins. The method can be used for assay of these vitamins over a wide concentration range with good precision and accuracy; hence, it would be appropriate for routine QC as well as in clinical analysis.     

Crystal Structure of Mononuclear Non-Heme Nikel(II) Octahedral Complex: [Ni(bqenH<Subscript>2</Subscript>)(bpy)](ClO<Subscript>4</Subscript>)<Subscript>2</Subscript>·0.125H<Subscript>2</Subscript>O

The crystal structure of a mononuclear Ni(II) complex [Ni(bqenH₂)(bpy)](ClO₄)₂·0.125H₂O 1 (where bqenH₂ is N,N′-bis(8-quinolyl)ethane-1,2-diamine, bpy = 2,2′-bipyridine) is reported here. The crystallographic data for 1 are as follows: monoclinic crystal system, P2_1/n space group, a = 17.3255(11), b = 10.6110(7), c = 34.328(2) Å, α = 90°, β = 93.9480(13)°, γ = 90°, V = 6295.8(7) ų, Z = 4, d_x = 1.541 mg/m³. The nickel(II) ion coordinates four N atoms of the tetradentate ligand bqenH₂ and two N atoms of the auxiliary bidentate 2,2′-bipyridine ligand, resulting in a slightly distorted NiN6 octahedron with two perchlorates serving as charge balancing counter anions. The overall structure of 1 is stabilized by the presence of water of crystallization in the crystal lattice. The crystal structure shows two symmetrically identical octahedral NiN6 units in its asymmetric unit. The extensive hydrogen bonding network resulting in a supramolecular architecture is observed due to the N–H?O, O–H?O, O–H?Cl, and N–H?Cl interactions.     

The complexes of aluminium,gallium, and indium with calmagite: Evaluation of stepwise stability constants

Summary Calmagite [1-(1-hydroxy-4-methyl-2-phenyl azo)-2-naphthol sulphonic acid], dissociates in two steps. It forms violet complexes with Al³⁺, Ga³⁺ and In³⁺. The stepwise proton-ligand stability constants of calmagite and stepwise metal-ligand stability constants of these complexes were evaluated by potentiometric titration technique ofBjerrum andIrving andRossotti. The order of the stabilities of complexes is In³⁺ > Ga³⁺ > > Al³⁺.

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Zusammenfassung Camalgit [1-(1-Hydroxy-4-methyl-2-phenylazo)-2-naphtholsulfonsäure] dissoziiert in zwei Stufen und bildet violette Komplexe mit Al(III), Ga(III) und In(III). Die Konstanten der Dissoziationsstufen der freien Säure und die der Metallkomplexe wurden potentiometrisch nachBjerrum bzw.Irving undRossotti ermittelt. Die Stabilität der Komplexe nimmt in der Reihe In(III) > Ga(III) > Al(III) ab.

     

Organotellurium derivatives : IV. Synthesis of some diaryltellurium dihalides and pseudohalides

Iodine monohalides (ICl, IBr), cyanogen halides (CNBr, CNI) and thiocyanogen (SCN)₂ add oxidatively to diaryltellurium(II), R₂Te (R = Ph, p-Ch₃OC₆H₄) under mild conditions ( °C). The resulting organotellurium(IV) derivatives react metathetically with silver pseudohalides to yield several new diaryltellurium(IV) pseudohalide derivatives.     

Application of INAA for phyto-accumulation study of selenium by chickpea plant

The phyto-accumulation efficacy of selenium (Se) from soil by chickpea plant is reported. Chickpea plants were grown in soil having different concentrations (1–4 mg kg^?1) of Se. Samples of soil and different parts of chickpea plants in Se rich soil were analyzed for determination of Se concentrations by instrumental neutron activation analysis (INAA). Samples were irradiated in self-serve facility of CIRUS reactor, BARC, Mumbai at a neutron flux of the order of 10¹³ cm^?2 s^?1. The gamma activity at 264.7 keV of ⁷⁵Se (119.8 d) was measured using a 45% relative efficiency HPGe detector coupled to MCA. Dependence of Se distribution in soil and plants on its spiking concentration was evaluated in this work. The Se concentrations determined in plant parts grown in control soil and in soil spiked with Se (4 mg kg^?1) are in the range of 0.6–0.8 and 65–68 mg kg^?1 respectively.     

Polymeric Gene Carriers Bearing Pendant β‐Cyclodextrin: The Relevance of Glycoside Permethylation on the “In Vitro” Cell Response

The incorporation of cyclodextrins (CDs) to nonviral cationic polymer vectors is very attractive due to recent studies that report a clear improvement of their cytocompatibility and transfection efficiency. However, a systematic study on the influence of the CD derivatization is still lacking. In this work, the relevance of β‐CD permethylation has been addressed by preparing and evaluating two series of copolymers of the cationic N‐ethyl pyrrolidine methacrylamide (EPA) and styrenic units bearing pendant hydroxylated and permethylated β‐CDs (HCDSt and MeCDSt, respectively). For both cell lines, CDs permethylation shows a strong influence on plasmid DNA complexation, “in vitro” cytocompatibility and transfection efficiency of the resulting copolymers over two murine cell lines. While the incorporation of the hydroxylated CD moiety increased the cytotoxicity of the copolymers in comparison with their homopolycationic counterpart, the permethylated copolymers have shown full cytocompatibility as well as superior transfection efficiency than the controls. This behavior has been related to the different chemical nature of both units and tentatively to a different distribution of units along the polymeric chains. Cellular internalization analysis with fluorescent copo­lymers supports this behavior.

     

Metal-free,PTSA catalyzed facile synthesis of β-ketoacetal from β-chlorocinnamaldehyde

A toluene solution of β-chlorocinnamaldehyde and dihydroxy alcohols in the catalytic presence of para-toluenesulphonic acid (PTSA) yield the β-ketoacetal in good to outstanding amount. The catalyst (PTSA), first selectively protect the aldehydic group to form the β-chloroacetal and the subsequent dechlorination by H₂O result the β-ketoacetal. Significant transformation was achieved with electron donating substituent attached at the para-position of cinnamaldehyde. The selective formation of β-keto-1,3-acetal was also obtained with a mixture of 1, 2- and 1, 3- diol. The present reaction consists of a metal-free, economical, robustly feasible, sizeable functional group tolerance and high yield properties. Moreover, the use of different dihydroxy alcohols made this process more benign and valuable towards the metal-free development of ketones. First, of its kind, a rare and unusual multitasking nature of PTSA is observed.