Separation,Identification, and Quantification of N-Acetyl Cilastatin in Human Urine

Abstract

A new high-performance liquid chromatographic method coupled with anion-exchange sample extraction has been developed for the isolation and quantification of N-acetyl cilastatin from human urine samples. N-Acetyl cilastatin, isolated from urine after I.V. administration of cilastatin, was converted to dimethyl esters, and characterized by thin-layer chromatography and mass spectrometry. The detection limit of the assay was 5 μg/ml in urine. The method was shown to be linear, reproducible and reliable for the quantification of N-acetyl cilastatin in urine from four human subjects given I.V. doses of cilastatin alone and together with 250 and 1,000 mg of imipenem.     

Elimination De L'Interference Des Salicyles Dans Le Dosage U. V. Du Paracetamol Sanguin

Abstract

Authors propose a simple method for U. V. determination of blood paracetamol in emergency toxicology. First, diethy1-ether extraction allows salicylate elimination (especially salicylic acid which is the most frequently used in therapy). Secondly paracetamol is extracted by ethyl-acetate and measured by U. V. spectrophotometry at 244 nm. The method provides good repeta-bility (C V=3.3 %) and reproducibility (C V u 4.3 %) with a detection limit of 2 mg L^?1 in plasma.     

Syntheses,characterization, and X-ray crystal structures of two cis-dioxovanadium(V) complexes of pyrazole-derived,Schiff-base ligands

Two mononuclear cis-dioxovanadium(V) complexes of pyrazole-derived, Schiff-base ligands have been synthesized and characterized. Single crystal X-ray analyses were performed with N ′-[(3-methyl-1H-pyrazole-5-yl)carbonyl]pyridine-2-carbohadrazonamido cis-dioxovanadium(V), {[VO₂(PzOAP)] · H₂O} (1), and 5-methyl-N-[(1E)-1-(pyridin-2-yl)ethylidene]-1H-pyrazole-3-carbohydrazonate cis-dioxovanadium(V), {[VO₂(PzCAP)]} (2). Both complexes crystallize in monoclinic crystal systems with different space groups. Complex 1 crystallizes in the space group P21/c, 2 in space group C2/C. In each complex, the vanadium sits within a distorted square pyramidal geometry with an N₂O₃ chromophore. The τ parameters of the complexes (0.33 for 1, 0.22 for 2) support their square pyramidal geometry. The interesting finding in the work is that the alkoxide oxygen, imino nitrogen, and pyridine nitrogen take part in the coordination process leaving the pyrazole rings inactive in coordination.     

Determination of Physostigmine in Plasma by Liquid Chromatography with Dual Electrode Amperometric Detection

Abstract

Physostigmine in plasma is determined after solid phase extraction. Ion-pair liquid chromatography is used for the separation and dual electrodes in a series mode are used for the detection. Physostigmine is first oxidized at +1.0 V and the reaction product formed is determined by reduction at +0.10 V versus Ag/AgCl. The solid phase extraction gives a recovery of 62 ± 6% (n=5) from plasma spiked with physostigmine to a concentration of 14 ng/mL. A detection limit of 0.5 ng/mL is obtained from a sample of 2 mL plasma.     

A new trans-dioxorhenium(V) complex with 4-aminopyridine: synthesis,structure, electrochemical aspects,DFT, and TD-DFT calculations

The reaction of 1?:?4.4?M proportion of cis-[ReO₂I(PPh₃)₂] and 4-aminopyridine (ampy) in acetone–water gives trans-[ReO₂(ampy)₄]I·2H₂O (1a) in 85% yield. 1a has been characterized by C, H, and N microanalyses, FT-IR, UV–vis, ¹H NMR spectroscopy, and molar conductivity. The X-ray crystal structure of 1a reveals an octahedral trans dioxorhenium(V) complex with a “N₄O₂” coordination for rhenium. 1a has an orthorhombic space group C2221 with a?=?17.576(4), b?=?19.370(4), c?=?15.730(4) Å, V?=?5355(2) ų, and Z?=?8. Geometry optimization of the trans-O,O complex, 1a and its cis-O,O analog, 1b performed at the level of density functional theory reveal that 1a is more stable than 1b by 25?kcal M^–1 in the gas phase. The electronic spectrum of 1a was also analyzed at the level of time-dependent density functional theory. Excitation of 1a in methanol at 450?nm leads to a fluorescent emission at 505?nm with a quantum yield (Ф) of 0.04. Electrochemical studies of 1a in acetonitrile show a quasi-reversible Re(V) to Re(VI) oxidation at 0.618?V versus Ag/AgCl. This redox potential matches with the calculated redox potential of 0.621?V versus Ag/AgCl.     

A ratiometric fluorescent probe for zinc ions based on the quinoline fluorophore

A ratiometric fluorescent zinc probe 1 of carboxamidoquinoline with a carboxylic acid group was designed and synthesised. Probe 1 exhibits high selectivity for sensing Zn²⁺; about a 13-fold increase in fluorescence emission intensity and an 82?nm red-shift of fluorescence emission are observed upon binding Zn²⁺ in EtOH/H₂O (1?:?1, V/V) solution. The ratiometric fluorescence response is attributed to the 1?:?1 complex formation between probe 1 and Zn²⁺ which has been utilised as the basis for the selective detection of Zn²⁺. The analytical performance characteristics of the proposed Zn²⁺-sensitive probe were investigated. The linear response range covers a concentration range of Zn²⁺ from 2.0?×?10^?6 to 5.0?×?10^?5?mol?L^?1 and the detection limit is 2.7?×?10^?7?mol?L^?1. The determination of Zn²⁺ in both tap and river water samples shows satisfactory results.     

Determination of 1‐Naphthol with Denatured DNA–Modified Pretreated Glassy Carbon Electrode

Abstract

A highly sensitive electrochemical biosensor for the detection of trace amount of 1‐naphthol was designed. Acid‐denatured DNA were immobilized onto the pretreated glassy carbon electrode (GCE(ox)) surface. Two well‐defined oxidation peaks were observed on the denatured DNA‐modified GCE(ox) at about +0.80 V and +1.10 V (vs. Ag/AgCl) in 0.10‐M acetate buffer (pH 5.0). The peak current of the guanine residue decreased with increasing concentration of 1‐naphthol. The optimum experimental conditions for the detection of 1‐naphthol were explored, and the calibration was linear for 1‐naphthol in the range of 1.0×10^?8?1.1×10^?6 M, with a correlation coefficient of 0.998. The limit of detection (LOD) was 5.0×10^?9 M (S/N=3).     

Kinetic Spectrophotometric Determination of Vanadium (V) Based on its Inhibitory Effect on the Thionine – Ascorbic Acid Reaction

ABSTRACT

A simple and sensitive kinetic method for the determination of vanadium(V) based on its inhibitory effect on the reduction of thionine by ascorbic acid at pH=5 is described. The reaction rate is monitored spectrophotometrically by measuring the decrease in absorbance of thionine at 598 nm after a fixed time (10 min). The calibration graph is linear in the range of 10 ? 120 ng ml^?1 of vanadium(V) and the detection limit is 6 ng ml^?1. The relative standard deviation (RSD) for 80 ng ml^?1 of V(V) was 0.96% (n=10). The method was successfully applied to the determination of vanadium in a certified reference sample.     

New Rapid Assay for Nafcillin by Spectrofluorimetry in Pharmaceutical Dosage

Abstract

A method for the spectrofluorimetric determination of nafcillin is proposed (λ_ex = 226 nm, λ_em = 366 nm), for concentrations between 0.10 and 1.0 μg mL^?1. The method was performed in ethanol/water medium (30% V/V), at apparent pH 6.0 provided by adding of phosphate buffer solution with pH = 6.20.

The obtained values of detection and determination limits are 0.016 and 0.054 μg mL^?1, respectively.

The method was successfully applied to assay a commercial injection containing nafcillin sodium monohydrate.     

Determination of Aztreonam by liquid Chromatography with UV and Amperometric Detection

Abstract

A comparative study of UV and amperometric detection of aztreonam after HPLC separation is presented. At pH 2.0 and a detection potential of +1.15 V (vs. Ag/AgCl), the detection limits with amperometric detection are about two times higher (3–5 ng) than those obtained with UV detection (1–3 ng) for aztreonam and its main decomposition products, the E-isomer and open-ring aztreonam. With the advantage of specificity for the aminothiazole group of the aztreonam molecule, amperometry can be used as an alternative or complementary mode to UV detection for the determination of aztreonam in injectable formulations and in human serum.     

Determination of Carbonyl 2,4-Dinitrophenylhydrazones by Liquid Chromatography/Electrochemistry

Abstract

Reductive mode liquid chromatography/electrochemistry was evaluated for use in quantitating 2,4-dinitrophenylhydrazine derivatives of carbonyls. Optimum performance was achieved at an operating potential of-0.75V vs Ag/AgCl. Detection limits for DNPH-formaldehyde, acetaldehyde, acetone, and acrolein were 54, 80, 76, and 99 pg respectively. These detection limits were approximately 20 times lower than obtainable with UV absorbance at 254 nm.     

Binary and ternary oxorhenium(V) complexes: synthesis,characterization, and crystal structure

A series of anionic five-coordinate binary oxorhenium(V) complexes with dithiolato ligands, Bu₄N[ReO(L¹)₂] (1a), Bu₄N[ReO(L²)₂] (1b), and Bu₄N[ReO(L³)₂] (1c), and a series of neutral octahedral ternary oxorhenium(V) complexes of mixed dithiolato and bipyridine ligands, [ReO(L¹)(bpy)Cl] (2a), [ReO(L²)(bpy)Cl] (2b), and [ReO(L³)(bpy)Cl] (2c) (where L¹H₂ = ethane-1,2-dithiol, L²H₂ = propane-1,3-dithiol, L³H₂ = toluene-3,4-dithiol, and bpy = 2,2′-bipyridine), were isolated and characterized by physicochemical and spectroscopic methods. The solid state structure of 1c was established by X-ray crystallography. All the mononuclear oxorhenium(V) complexes are diamagnetic. The redox behavior of all the complexes has been studied voltammetrically.     

The Separation of 12-Molybdophosphoric Acid from 12-Molybdosilicic Acid by Reverse Phase Liquid Chromatography

Abstract

The separation of 12-molybdophosphoric Acid (12-MPA) from 12-molybdosilicic (12-MSA) acid by reverse phase liquid chromatography is described with UV-visible detection. The system utilizes a commercially available styrene-divinylbenzene column (Hamilton PRP-1) and a acetonitrile-water mobile phase which is 0.1 F in HCLO₄ and 1.2 × 10^?2 in molybdate ion. In solutions with acetonitrile concentrations of between 30 and 35% (V/V), 12-MPA is completely retained on the column and 12-MSA has a capacity factor between 1.2 and .6. In solutions with acetonitrile concentrations of between 50 and 60% (V/V) 12-MSA is unretained and 12-MPA has a capacity factor between 2.2 and 1.6.

The detection limit is 5 × 10^?7 M phosphate or silicate anion in 100 uL of injected sample. The linear dynamic range extends to 1.3 × 10^?5 M for either anion. The relative standard deviation of the technique at the 5 × 10^?6 M level is 2% for both silicate and phosphate. The analysis of phosphate in silicate rock is described.     

OH functionalized Multi-Walled Carbon Nanotube modified electrode as electrochemical sensor for the detection of Aceclofenac

ABSTRACT

The rapid electrochemical determination of Aceclofenac (ACF) has been employed by cyclic voltammetry (CV), differential pulse voltammetry (DPV) using developed OH-functionalised multiwalled carbon nanotube carbon paste electrode (OH-MWCNT/CPE). Modified electrode was characterised by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDAX), X-ray diffraction spectroscopy (XRD), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The ACF exhibits two oxidation peaks at +0.4 V, +0.66 V and one reduction peak at +0.3 V. The active surface area of the bare carbon paste electrode (BCPE) and modified electrode have been characterised by using K₃[Fe(CN)₆] solution containing 0.1 M KCl. In DPV mode, variation of ACF gave the limit of detection (LOD = 3s/m) 0.246 μM over the concentration range 1.0 to 190.0 μM (R² = 0.9994). The developed electrode has good stability, reproducibility and could be successfully validated for the detection of ACF in pharmaceutical samples and biological fluids.     

A Crystalline Quartz,Laser-Excited Fluorescence,Photoacoustic, and Two-Photon Photoionization Detector for HPLC

Abstract

A crystalline quartz flow cell has been developed for simultaneous fluorescence, photoacoustic effect, and two-photon photoionization detection of aromatic compounds in HPLC eluents. Excimer laser-excited three mode detection of naphthalene, 7,8-benzoflavone, N-ethylcarbazole, and anthracene in 70/30 v/v acetonitrile/water is exhibited. The flow cell is suitable for use with deoxygenated solvent systems and is orientation independent.     

Crystal Structures of Mono-, Di-, and Triaminoguanidinium Sulfate,as Well as Azidoformamidinium Sulfate: Important Precursors for Syntheses of Nitrogen Rich Ionic Compounds

Bis(1-aminoguanidinium) sulfate monohydrate (AG₂SO₄ … H₂O, 1), bis(1,3-diamino-guanidinium sulfate (DAG₂SO₄, 2), bis(1,3,5-triaminoguanidinium) sulfate dihydrate (TAG₂SO₄ … 2 H₂O, 3) and bis(azidoformamidinium) sulfate (AF₂SO₄, 5) were synthesized and characterized by multinuclear NMR, IR, and Raman spectroscopy and elemental analysis. In the synthesis of 3, double protonated triaminoguanidinium sulfate (HTAGSO₄, 4) was obtained as a byproduct. The molecular structures of 1–5 in the crystalline state were determined by low-temperature single crystal X-ray diffraction. 1: orthorhombic, Pnma, a = 6.7222 (8) Å, b = 14.153 (2) Å, c = 11.637 (1) Å, V = 1107.1(2) ų, Z = 4, ρ_calc.= 1.586 g cm^?3 R₁ = 0.0442, wR₂ = 0.1007 (all data). 2: hexagonal, P6₁22, a,b = 6.6907 (1) Å, c = 43.4600 (8) Å, γ= 120°, V = 1684.86 (5) ų, Z = 6, ρ_calc.= 1.634 g cm^?3, R₁ = 0.0321, wR² = 0.0714 (all data). 3: monoclinic, C2/c, a = 9.6174 (8) Å, b = 22.858 (1) Å, c = 6.7746 (5) Å, β= 109.49 (1), V = 1404.0 (4) ų, Z = 4, ρ_calc.= 1.620 g cm_?3, R₁ = 0.0292, wR₂ = 0.0781 (all data). 4: monoclini c, P2₁/c, a = 8.9998 (9), b = 6.3953 (6), c = 13.3148(12) Å, β= 99.679 (8), V = 755.44 (13) ų, Z = 4, ρ_calc.= 1.778 g cm^?3, R₁ = 0.0305, wR₂ = 0.0809 (all data); 5: orthorhombic, Pbca, a = 11.3855 (9), b = 7.1032 (6), c = 12.807 (1) Å, V = 1035.74 (14) ų, Z = 4, ρ_calc.= 1.720 g cm^?3, R₁ = 0.0389, wR₂ = 0.0862 (all data).     

Analysis of α-Ketocarboxylic Acids by Ion Exchange Hplc With UV and Amperometric Detection

Abstract

Cation exchange high performance liquid chromatography with tandem 200nm spectrophotometric and +1.15V amperometric detection was used for the analysis of severalOt α-ketocarboxylic acids. Derivatization of the α-ketocarboxyiic acids was not necessary. This technique was operable at 2.0 ug/ml concentrations of α-ketocarboxylic acids. The sensitivity limit was not investigated.     

Comparative Study of Fluorometric and Electrochemical Detection of Catecholamine,Serotonin, and Metabolites in Rat Brain by High-Performance Liquid Chromatography

Abstract

A high-performance liquid chromatograph connected to a newly designed fluorometer was used for the simultaneous determination of norepinephrine, dopamine, serotonin, 3-methoxy-4-hydroxyphenylglycol (MHPG), homovanillic acid, and 5-hydroxyindoleacetic acid by measuring native fluorescence. These amines and metabolites extracted from the frontal cortex of a rat were purified by adsorption on alumina and an extraction with ethyl acetate and separated in the chromatograph with an ODS column. The detection limits ranged from 0.5 to 3 pmoles. Compared to the electrochemical (EC) detection at an electrode potential of 0.8 V, the sensitivity was almost the same or somewhat lower, but MHPG was highly fluorescent. In the fluorometry, large front peaks observed in the EC detection did not appear, and interfering peaks were not observed.     

A novel Hg2+ fluorescence sensor TPE-TSC based on aggregation-induced emission

Abstract

A fluorescent sensor TPE-TSC with aggregation induced emission (AIE) characteristic is synthesized for detecting Hg²⁺ by attaching thiosemicarbazide (TSC) unit into tetraphenylethylene (TPE) group. TPE-TSC exhibits intense green emission in DMSO/H₂O (V:V?=?1:9) solution with the formation of the aggregation. TPE-TSC shows outstanding fluorescence quenching toward Hg²⁺ over other metal ions due to the formation of complex TPE-TSC/Hg²⁺ with a 2:1 binding ratio. The detection limit of TPE-TSC for Hg²⁺ is 1?×?10^?5 mol·L^?1.