Spectrophotometric and Atomic Absorption Spectroscopic Determination of Some Fluoroquinolone Antibacterials by Ion‐pair Complex Formation with Bismuth (III) Tetraiodide

New simple spectrophotometric and atomic absorption spectrometric (AAS) methods have been developed for the determination of levofloxacin (I), norfloxacin (II), and ciprofloxacin (III) in pure form, tablet formulations, and spiked human urine. The methods are based on the formation of ion‐pair associates between the drugs and the inorganic complex, bismuth (III) tetraiodide. The reaction occurs in acidic medium to form orange‐red ion‐pair associates which are instantaneously precipitated. The formed precipitates are then filtered off and the residual unreacted metal complex in the filtrate is determined either spectrophotometrically at 453 nm or by AAS at 223.1 nm. Also, the precipitates may be dissolved in acetone and quantified spectrophotometrically at 469 nm or decomposed by hydrochloric acid, and the bismuth content is determined by AAS at 223.1 nm. The methods permit the determination of the three studied drugs in the range of 5–80 μg mL^?1. The proposed methods were successfully applied to determine these drugs in their tablet formulations and spiked urine samples without any evidence for interference from pharmaceutical additives or biological matrix. The results were in good agreement with those obtained by the reference methods. The proposed methods, especially if automated, can be confidently applied for quality control and routine analysis of the studied drugs.     

Molecular Structure,Vibrational Spectra,and Hydrogen Bonding of the Ionic Liquid 1‐Ethyl‐3‐methyl‐1H‐imidazolium Tetrafluoroborate

The IR and Raman spectra and conformations of the ionic liquid 1‐ethyl‐3‐methyl‐1H‐imidazolium tetrafluoroborate, [EMIM] [BF₄] ( 6 ), were analyzed within the framework of scaled quantum mechanics (SQM). It was shown that SQM successfully reproduced the spectra of the ionic liquid. The computations revealed that normal modes of the EMIM⁺?BF ion pair closely resemble those of the isolated ions EMIM⁺ and BF , except for the antisymmetric BF stretching vibrations of the anion, and the out‐of‐plane and stretching vibrations of the H? C(2) moiety of the cation. The most plausible explanation for the pronounced changes of the latter vibrations upon ion‐pair formation is the H‐bonding between H? C(2) and BF . However, these weak H‐bonds are of minor importance compared with the Coulomb interactions between the ions that keep them closely associated even in dilute CD₂Cl₂ solutions. According to the ‘gas‐phase’ computations, in these associates, the BF anion is positioned over the imidazolium ring of the EMIM⁺ cation and has short contacts not only with the H? C(2) of the latter, but also with a proton of the Me? N(3) group.     

Evaluation of Manganese(II) and Manganese(VII) Speciation in Water Samples by Ion Pair High-performance Liquid Chromatography-inductively Coupled Plasma Mass Spectrometry

The speciation of Mn(II) and Mn(VII) is reported by ion pair chromatography. To optimize the separation, sample pH, ion pair reagent, Mn(II) complexing agent, and composition of mobile phase were characterized. The separation of Mn(II) and Mn(VII) was performed using ethylenediamine tetraacetic acid to complex Mn(II), tetrabutylammonium hydroxide as an ion pair reagent, and a C8 column. The separation of the manganese species was demonstrated by high-performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC ICP-MS). The conversion of Mn(VII) to Mn(II) occurred during the separation and influenced the quantification; hence, the factors affecting this process including the storage time, manganese species ratio, and sample matrix composition were evaluated and suitable calibration was demonstrated. The method was validated by characterization of the selectivity, specificity, linearity, limits of detection and quantification, repeatability, and intermediate precision. The detection limit for Mn(II) was 0.22 µg?L^?1, while for Mn(VII), the value was 1.55 µg?L^?1.     

Extraction of platinum with Astrafloxin FF from aqueous-organic solutions: Separative extraction-spectrophotometric determination of platinum(II) and platinum(IV) species

The optimum conditions of the extraction of the ion associates of platinum with the thiocyanate ions and the polymethine basic dye Astrafloxin FF by aromatic hydrocarbons and acetic acid esters from aqueous and aqueous-organic solutions were studied. The introduction of water-soluble donor-active solvents (hexamethylphosphoric triamide, N,N-diethylacetamide, N,N-dimethylformamide, and N,N-diethylformamide) leads to a considerable increase in the extraction of the ion associates of platinum and the simultaneous suppression of the extraction of the simple dye salt. The molar absorption coefficients of the extracts of ion associates are as high as (8.1?C13.3) × 10⁴. 84?C96% platinum is extracted in the form of ion associates by a single extraction. The conversion of platinum into ion associates makes it possible to separate platinum from many elements, including Cu, Cd, Ni, Co, Cr, Pb, In, Ag, Pd, Ir, Rh, and Ru, by extraction. In this case, platinum(II) is extracted in the form of ion associates under standard conditions, whereas platinum(IV) is extracted only after the preliminary thermal treatment of the test sample. A new procedure was developed for the extraction-spectrophotometric determination of the trace amounts of platinum(II) and platinum(IV), in particular, in their mixtures.     

Spectrophotometric Determination of Dextromethorphan Hydrobromide and Ketamine Hydrochloride in Pure and Dosage Forms

Three simple, sensitive and accurate spectrophotometric methods have been developed for the determination of dextromethorphan hydrobromide (DEX) and ketamine hydrochloride (KET) in dosage forms. These methods are based on the formation of ion‐pair complexes with bromocresol green (BCG), bromocresol purple (BCP), and bromophenol blue (BPB) in acidic medium. The coloured ion‐pair products are measured at 419, 409 and 417 nm for DEX and at 417, 408 and 416 nm for KET using BCG, BCP and BPB, respectively. Beer's law was obeyed in the range of 2.0–22 μg mL^?1 for DEX and 2.0–16 μg mL^?1 for KET. The composition of the ion‐pair was established by continuous variation and molar ratio methods. The proposed methods were applied successfully for the determination of DEX and KET in dosage forms applying the standard addition technique and compared statistically with the official methods. The molar absorptivity, Sandell sensitivity, detection and quantification limits were also calculated.     

Novel Dicyanoargentate Polymeric Membrane Sensors for Selective Determination of Cyanide Ions

The construction and general performance characteristics of three novel potentiometric PVC membrane sensors responsive to dicyanoargentate anion are described. The sensors are based on the use of magnesium(II)‐ and iron(II)‐phthalocyanines as neutral ionophores and iron(II)‐bathophenanthroline dicyanoargentate ion‐pair complex as an ion exchanger in plasticized PVC matrices. These sensors exhibit fast, stable and near‐Nernstian response (54–59 mV/decade) for the singly charged dicyanoargentate anion over the concentration range 1×10^?2–5.8×10^?6 M. Potentiometric responses of sensors based on metal phthalocyanines and iron(II)‐bathophenanthroline are stable over the pH ranges 5–7 and 5–12, respectively. The selectivity of the sensors are fairly good over most common anions. Use of the sensors for potentiometric determination of microgram quantities of cyanide ion after conversion into dicyanoargentate anions shows an average recovery of 99.5% and a mean standard deviation of ±0.5%. Determination of cyanide ions in some exhausted electroplating bath samples gives results that compare favourably well with data obtained using the solid‐state cyanide electrode.     

On‐line Liquid‐liquid Extraction Coupled to a Reversed Micellar‐mediated Chemiluminescence Detection System: Application to the Determination of Amino/Nitroaromatic Compounds

A simple and fast flow method for the trace level determination of p‐toluidine, 2‐methyl‐5‐nitroaniline, and 2,4‐dinitroaniline in aqueous samples is reported. These amino/nitroaromatics are related to trinitrotoluene (TNT) and appear during the degradation process of the explosive. The chemical principles of ion‐pair formation and liquid‐liquid extraction are applied: In aqueous acidic medium, the protonated analyte [HA]⁺ makes an ion‐pair with the tetrachloroaurate(III) ion, followed by on‐line ion‐pair extraction into the dichloromethane carrier used. After membrane separation, the CH₂Cl₂ containing the ion‐pair, [HA]⁺[AuCl₄]⁻, is mixed with the reversed micellar luminescent reagent of luminol (in 0.3 M Na₂CO₃) prepared from cetyl‐trimethylammonium chloride in CH₂Cl₂‐cyclohexane and the [AuCl₄⁻‐luminol chemiluminescence (CL) output is recorded. The detection limits (S/N> 3) are: p‐toluidine, 1.0 × 10⁻⁴M; 2‐methyl‐5‐nitroaniline, 1.0 × 10⁻⁷ M; 2,4‐dinitroaniline, 1.0 × 10⁻⁷ M, while the calibration curves are linear between 1.0 × 10⁻⁴ — 1.0 × 10⁻² M for all the compounds. Although spectral studies indicated the formation and extraction of a very small amount of the ion‐pair species, the reversed micellar‐mediated CL detection system provides an alternative procedure for the determination of degradation products of the explosive TNT in environmental aqueous samples.     

基于T-T碱基错配的荧光传感器特异性检测汞离子

在本文中,我们研制了一种基于T-T碱基错配特异性键合汞离子的荧光传感器用于汞离子的检测。该传感器由两条分别标记了荧光基团（F）和淬灭基团（Q）的DNA探针组成,并且含有两对用于结合汞离子的T-T错配碱基。当汞离子存在时,两条探针之间形成T-Hg2+-T结构,作用力增强,从而拉近了荧光基团与淬灭基团之间的距离,发生能量转移,使荧光信号在一定程度上被淬灭。在优化的条件下,我们使用该传感器对汞离子进行检测,动力学响应范围为50nM到1000nM,线性相关方程为y= 5281.13 - 1650.56 lg[Hg2+] ( R2 = 0.985),检测下限为79nM。此外,我们还考察了该传感器的选择性,当用其它干扰离子（浓度都为1.0µM）代替待测离子进行实验时,没有发生明显的荧光淬灭,说明该传感器具有较高的选择性。该传感器的构建为汞离子的检测提供了一条快速、简便的新途径。     

High Sensitive and Selective Spectrophotometric Determination of Aluminium after Collection on a Membrane Filter Using 2,3‐Dichloro‐6‐(3‐carboxy‐2‐hydroxy‐1‐naphthylazo)quinoxaline and Zephiramine

Abstract

A high sensitive and selective spectrophotometric method for the determination of aluminium(III) using 2,3‐dichloro‐6‐(3‐carboxy‐2‐hydroxy‐1‐naphthylazo)quinoxaline (DCHNAQ) and zephiramine (zeph) is described. The formed ion pair precipitate between zephiramine and perchlorate ions is effective for the enrichment of aluminium(III) on a membrane filter as its ternary complex with DCHNAQ and zephiramine. The solid–state absorbance of the complex on the membrane filter is measured at 655 nm against a blank thin layer and the difference is calculated. The colour system obeys Beer's law from 5.0–150 ng ml^?1 of aluminium. The detection and quantification limits were calculated. The relative standard deviation for 60 ng of aluminium(III) in 20‐ml sample volume amounts 0.84% (n=10). A ligand buffer solution, composed of transcyclohexane‐1,2‐diaminetetraacetic acid with an excess of zinc(II), is effective for masking interferences from foreign ions, particularly iron(III). The proposed method was applied successfully to tap and environmental water, biological (human blood, urine, and gallstone), and soil samples.     

Self‐Assembled Mercapto‐Compound‐Gold‐Nanoparticle‐Modified Carbon Paste Electrode for Potentiometric Determination of Cadmium(II)

A new modified carbon paste electrode (CPE) based on a recently synthesized ligand [2‐mercapto‐5‐(3‐nitrophenyl)‐1,3,4‐thiadiazole] (MNT), self‐assembled to gold nanoparticles (GNP) as suitable carrier for Cd(II) ion with potentiometric method are described. The proposed electrode exhibits a Nernstian slope of 29.4±1.0 mV per decade for Cd(II) ion over a wide concentration range from 3.1×10^?8 to 3.1×10^?4 mol L^?1. The detection limit of electrode was 2.0×10^?8 mol L^?1 of cadmium ion. The potentiometric responses of electrode based on MNT is independent of the pH of test solution in the pH range 2.0–4.0. It has quick response with response time of about 6 s. The proposed electrode show fairly good selectivity over some alkali, alkaline earth, transition and heavy metal ions. Finally, the proposed electrode was successfully employed to detect Cd(II) ion in hair and water samples.     

Determination of Cyanuric Acid in Milk Powder and Swimming Pool Water by Ion‐pair Reversed‐phase Liquid Chromatography

An ion‐pair reversed‐phase high‐performance liquid chromatographic method, using tetrabutylammonium bromide (TBAB) as ion‐pair reagent, has been developed for the analysis of cyanuric acid (CA) in milk powder and swimming pool water. It was found that the effect of the concentrations of ion‐pair reagent on the retention of cyanuric acid was different for standard solution and different real samples. The separation was carried out on a reversed‐phase C₁₈ column with 85:15 (V/V) water‐acetonitrile (ACN) containing different concentration of TBAB as mobile phase for different samples. The linear range of the calibration curve for CA was 0.1–100 mg·L^?1. The detection limits calculated at S/N=3 was 0.11 mg·L^?1 for the analysis of milk powder and 0.31 mg·L^?1 for the analysis of swimming pool water, respectively. The method was successfully applied to the analysis of CA in milk powder and swimming pool water.     

2,3‐Dihydro‐1,3‐benzothiazol‐2‐iminium monohydrogen sulfate and 2‐iminio‐2,3‐dihydro‐1,3‐benzothiazole‐6‐sulfonate: a combined structural and theoretical study

The 2‐aminobenzothiazole sulfonation intermediate 2,3‐dihydro‐1,3‐benzothiazol‐2‐iminium monohydrogen sulfate, C₇H₇N₂S⁺·HSO₄⁻, (I), and the final product 2‐iminio‐2,3‐dihydro‐1,3‐benzothiazole‐6‐sulfonate, C₇H₆N₂O₃S₂, (II), both have the endocyclic N atom protonated; compound (I) exists as an ion pair and (II) forms a zwitterion. Intermolecular N—H...O and O—H...O hydrogen bonds are seen in both structures, with bonding energy (calculated on the basis of density functional theory) ranging from 1.06 to 14.15 kcal mol⁻¹. Hydrogen bonding in (I) and (II) creates DDDD and C(8)C(9)C(9) first‐level graph sets, respectively. Face‐to‐face stacking interactions are observed in both (I) and (II), but they are extremely weak.     

Poly(N‐acetyl‐α‐acrylic acid): Synthesis,Characterization and Chelation Properties through Liquid Phase Polymer‐Based Retention Technique

The synthesis and characterization of the water‐soluble poly(N‐acetyl‐α‐acrylic acid) by radical polymerization were carried out. The polymer was characterized by Fourier Transform Infrared (FT‐IR), ¹H NMR and ¹³C NMR spectroscopies, and thermogravimetric analysis (TGA). The metal ion binding properties for the metals Cu(II), Co(II), Ni(II), Cd(II), Zn(II), Pb(II), Hg(II), Cr(III) in the aqueous phase were studied using the liquid‐phase polymer‐based retention technique. The metal ion interactions with the hydrophilic polymer were determined as a function of pH and of the filtration factor. The polychelatogen showed a high affinity for metal ions and higher selectivity for Cr(III) at pH = 3.     

Spectrophotometric Determination of Metoclopramide and Oxybuprocaine Through Ion Pair Formation with Thiocyanate and Molybdenum(V) or Cobalt(II)

Abstract

Two spectrophotometric methods involve the formation of two different ion pairs between the drug and inorganic complexes, Mo(V) and Co(II) thiocyanates followed by their extraction with dichlor?methane and o-nitrotoluene, respectively. The optimum conditions for the ion pair formation are established. The methods permit the determination of metoclopramide and oxybuprocaine hydrochlorides over a concentration range of 1-20 μg ml^?1 and 20–240 μg ml^?1 using Mo(V) and Co(II) thiocyanates, respectively. Molar ratio of drug to Mo(V) or Co(II) indicates a 2:1 ratio for the two drugs studied in the presence of excess thiocyanate concentration. Results of the analysis of drug substances and their dosage forms by the proposed methods are in good agreement with those obtained by the official methods.     

Spectrophotometric Determination of Some Fluoroquinolone Derivatives in Dosage Forms and Biological Fluids Using Ion‐Pair Complex Formation

Abstract

A simple, rapid, sensitive, and reproducible procedure for assaying norfloxacin (NOR), ciprofloxacin (CIP), and ofloxacin (OFL) was investigated. The procedure is based on the reaction of selected drugs with Sudan II (I), Congo red (II), and Gentian violet (III) in universal buffer to give soluble ion‐pair complexes. The effects of various parameters have been studied. Beer's law plots were obeyed in the concentration ranges 0.5–11 µg ml^?1, whereas Ringbom optimum ranges were 0.7–9.5 µg ml^?1. The apparent molar absorptivity (6.4×10⁴ L mol^?1 cm^?1), Sandell sensitivity (4.99 ng cm^?2), detection (0.13 µg ml^?1), and quantification (0.44 µg ml^?1) limits were calculated. The relative standard deviation for ten determinations, for samples containing 4.0 µg ml^?1, was found to be 1.40%. The influence of commonly employed excipients in the determination of the studied drugs was examined. There was no interference from degradate product results from thermal and hydrolytic treatments. The results obtained by the proposed procedure were statistically validated. The developed procedure was successfully applied to the determination of the studied drugs in dosage forms and biological fluids.     

Identification and extraction—spectrophotometric or extraction—fluorimetric determination of organic nitrogen-containing triiodides, new biologically active compounds

A method for the identification of organic triiodides is proposed, and rapid, highly sensitive procedures for the extraction-spectrophotometric and extraction-fluorometric determination of medicinal preparations as ion associates with hydroxyxanthene (Eosin) and triphenylmethane (Bromothymol Blue) dyes. The formation of 1 : 1 ion associates with an absorption maximum at 545 nm (430 nm for ion associates with Bromothymol Blue) and a fluorescence maximum at 560 nm was detected. The ion associates were extracted with chloroform from a water-ethanol solution at pH 6.86 and 9.18. The detection limits were c_min ≈ 4.3 × 10^-7 M for the extraction-spectrophotometric and c_min ≈ 8.6 sx 10^-8 M for the extraction-fluorimetric procedure; RSD ≤2%. The developed procedures can be used for controlling medicinal preparations and monitoring biological materials     

Chelating properties of poly(N‐acryloyl piperazine) by liquid‐phase polymer‐based retention (LPR) technique

The synthesis of poly(N‐acryloylpiperazine) was carried out by radical polymerization giving a yield of 90%. The polymer was soluble in water and was characterized by FTIR, ¹H NMR, ¹³C NMR spectroscopy, and TGA. The metal ability binding properties for the Ag(I), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Pb(II), and Cr(III) metal ions in the aqueous phase were investigated using the liquid‐phase polymer‐based retention (LPR) method. The metal ion interactions with the hydrophilic polymers were determined as a function of pH and filtration factor.     

Indirect Atomic Absorption Determination of Cocaine via Formation and Liquid‐liquid Extraction of the Iron(III)‐cocaine Complex

The principles of metal‐alkaloid ion‐pair formation and liquid‐liquid extraction are applied to the development of a sensitive and convenient atomic absorption spectrophotometery (AAS) method for the indirect determination of cocaine. In an aqueous medium of 5 M hydrochloric acid, cocaine is protonated and is associated with tetrachloro ferrate (III) anion prior to its extraction into 1,2‐dichloroethane. The critical experimental variables were identified and optimized. The method is simple and reproducible with a detection limit (DL) of 0.1 ng cm^?3 cocaine in water, a relative standard deviation of 0.07 (n = 12), and the calibration graph was linear up to 50 ng cm^?3 cocaine.     

A spectrophotometric method for manganese determination in water samples based on ion pair formation and dispersive liquid–liquid microextraction

In this work, a simple, inexpensive, and environmentally friendly extractive spectrophotometric method for the determination of manganese is suggested. The method is based on the formation and dispersive liquid–liquid microextraction (DLLME) of a violet-coloured ion pair of Mn(II) with 1,3,3-trimethyl-2-[3-(3-methyl-3H-benzothiazol-2-ylidene)-propenyl]-3H-indolium (BTIC) in the presence of 1-nitroso-2-naphthol (HL) as ligand, and subsequent UV-VIS spectrophotometric detection at 560?nm of the ion pair formed. The appropriate experimental conditions for the DLLME procedure were found to be: a pH of 9.5; 0.12?mmol?L^?1 of BTIC; extraction solvent – toluene containing 1.75?mmol?L^?1 of HL; disperser solvent – methanol; auxiliary solvent – tetrachloromethane. Beer's law is obeyed in the range 0.055–0.88 µg?mL^?1 of Mn(II). The limit of detection (LOD), calculated based on three times of the standard deviation of the blank test (n?=?10), was found to be 0.004?µg?mL^?1 of Mn(II). The precision (as relative standard deviation, RSD%) and accuracy (as recovery percentage, R%) of the method were examined by performing five replicate determinations at four concentration levels over two days and varied between 1.2 and 3.8, and 97.7 and 104.5, respectively. The suggested method was successfully applied to the analysis of various water samples (mineral water, spring water and drinking water).     

Multidrug analysis of pharmaceutical and urine matrices by on‐line coupled capillary electrophoresis and triple quadrupole mass spectrometry

The present work illustrates potentialities of CE hyphenated with MS/MS for the simultaneous determination and identification of a mixture of simultaneously acting drugs in pharmaceutical and biological matrices. Here, the hyphenation was provided by ESI interface, while the MS/MS technique was based on the triple quadrupole configuration. Three drugs, namely pheniramine, phenylephrine, and paracetamol were determined and identified with high reliability due to their characterization in three different dimensions, i.e. electrophoresis and MS/MS, that prevented practically any interference. Appropriately selected transitions of the analytes (parent ion‐quantifier product ion‐qualifier product ion) provided their selective determination at maximum S/N. The proposed CE‐MS/MS method was validated (LOD/LOQ, linearity, precision, recovery, accuracy) and applied for (i) the multidrug composition pharmaceuticals, namely Theraflu®, and (ii) human urine taken after per‐oral administration of the same pharmaceutical preparation. The method was applied also for the investigation of potential weak associates of the drugs and monitoring of predicted (bio)degradation products of the drugs. Successful validation and application of the proposed method suggest its routine use in highly effective and reliable advanced drug control and biomedical research.