The Ionic Associate of Metamizole as an Electrode-Active Component of a PVC Plasticized Membrane Electrode

The technology for manufacturing a film membrane of the metamizole-selective electrode containing ion associate metamizole-octadecylammonium ODAH+MT− as an electrode active component (EAC) has been proposed. The main potentiometric characteristics of the metamizole-selective electrode have been determined. The expediency of the proposed design of the metamizole selective electrode for the determination of metamizole in dosage forms has been substantiated. The best composition of the membrane (wt.%) of the metamizole-selective electrode has corresponded to: ODAH+MT−—5.3; 2-nitrophenyloctylether—63.1; poly(vinyl chloride)—31.6. Electrode-active component in the membrane phase functions as an ion associate ODAH+MT−. Potentiometric characteristics of metamizole-selective electrode have been determined, which corresponded to: linear range 1 × 10−2–1 × 10−4 with limit of detection 4.58 × 10−5 M, electrode function slope −48.5 mV/dec., working interval pH 4.5–7.3, response time 60 s. The potentiometric coefficients of selectivity of the metamizole-selective electrode with respect to various ions have been determined. The possibility of determining metamizole in a medicinal product has been tested. The results of the analyses show good agreement between the two methods (relative error less than 7.0%) with coefficients of variation less than 5% for MT-SE and iodometric methods.

Organic Ion-Associate Phase Microextraction/Back-Microextraction for Preconcentration: Determination of Nickel in Environmental Water Using 2-Thenoyltrifluoroacetone via GF-AAS

An ion-associate phase (IAP) microextraction/ back-microextraction system was applied for the enrichment, separation, and detection of trace amounts of nickel from environmental water samples. Thenoyltrifluoroacetone (HTTA) acted not only as a chelating reagent for nickel, but also as a component of the extraction phase, i.e., IAP. Nickel in a 40 mL sample solution was pH-adjusted with phenolsulfonate (PS−) and tetramethylammonium hydroxide and converted by chelation reaction in the presence of thenoyltrifluoroacetonate (TTA−). When benzyldodecyldimethylammonium ion (C12BzDMA+) was added, a suspension of IAP formed in the solution. The IAP consisted of TTA−, a chelating reagent, the PS−, a component of pH buffer, and C12BzDMA+, which helps extract the chelating complex. When the solution was centrifuged, the IAP separated from the suspension and the nickel-TTA chelate was extracted into the bottom phase of the centrifuge tube. After the aqueous phase was taken away, 100 µL of nitric acid (2 M) solution containing phosphate was used to back-microextract nickel from the IAP. The acid phase was measured via graphite-furnace atomic-absorption spectrometry (GF-AAS). The proposed method facilitated a 400-fold enrichment. The limit of detection was 0.02 µg L−1. The proposed method was applied for the determination of nickel in river water and seawater samples.

Green and sensitive spectrofluorimetric method for the determination of two cephalosporins in dosage forms

Using two green and sensitive spectrofluorimetric methods, we quantified two cephalosporins, cefepime (CFM) and cefazolin (CFZ), in raw and pharmaceutical formulations. The first method is based on the reaction between CFM and fluorescamine (borate buffer, pH 8), which yields a highly fluorescent product. After excitation at 384 nm, the fluorescent product emits light at 484 nm. At concentration ranges from 12.0 to 120.0 ng ml −1 , the relative fluorescence intensity/concentration curve was linear with a limit of quantification (LOQ) of 2.46 ng ml −1 . The second method relied on measuring the CFZ quenching action on acriflavine fluorescence through formation of an ion-associate complex using Britton–Robinson buffer at pH 8. We measured acriflavine fluorescence at 505 nm after excitation at 265 nm. The decrease in acriflavine fluorescence intensity was CFZ concentration-dependent. Using this method, we quantified CFZ in concentrations ranging from 1 to 10 µg ml −1 with a LOQ of 0.48 µg ml −1 . We studied and optimized the factors influencing reaction product formation. Moreover, we adapted our methods to the investigation of the mentioned drugs in raw and pharmaceutical formulations with greatly satisfying results. We statistically validated our methods according to International Council on Harmonisation Guidelines. The obtained results were consistent with those obtained with the official high-performance liquid chromatography methods.

Extraction-Chromogenic System for Cobalt Based on 5-Methyl-4-(2-thiazolylazo) Resorcinol and Benzalkonium Chloride

The interaction between CoII and 5-methyl-4-(2-thiazolylazo)-resorcinol (MTAR) was studied in a water-chloroform system, in the presence or absence of benzalkonium chloride (BZC) as a cationic ion-association reagent. The optimum pH, concentration of the reagents and extraction time for the extraction of Co were found. In the presence of BZC, the extracted ion-associate could be represented by the formula (BZ+)[CoIII(MTAR2–)2], where MTAR is in its deprotonated form. The following extraction-spectrophotometric characteristics were determined: absorption maximum, molar absorptivity, Sandell’s sensitivity, limit of detection, limit of quantification, constant of extraction, distribution ratio and fraction extracted. In the absence of BZC, the extraction is incomplete and occurs in a narrow pH range. The extracted chelate contains one deprotonated and one monoprotonated ligand: [CoIII(MTAR2–)(HMTAR–)].

Flotation-Dissolution-Spectrophotometric Determination of Phorate in Various Environmental Samples

The proposed method is based on flotation–dissolution an easy, impressible, extractive spectrophotometric determination, explained for easy investigation of the organophosphate pesticide phorate (O,O-diethyl S-[ethylthiomethyl] phosphorodithioate) on trace levels. A molybdophospho complex is generated when prorate is treated with ammonium molybdate in acidic medium. As an ion associate complex with methylene blue the complex is present in between of the water and organic layers which is extracted and then dissolved with acetone. The greenish blue complex produced show absorption maxima at 660 nm. Beer’s law range is found to be 0.5 to 16 µg per 10 ml for phorate. The molar absorptivity is 0.989×103 L mol-1 cm-1 and sandell’s sensitivity is 1.00×10-5 µg cm-2. Also calculated the standard deviation and relative standard deviation for the above method were ±0.006 and 1.95% respectively. The method has been applied and checked for the determination of phorate in water, soil and vegetables.

CATALYTIC INFLUENCE OF NITROGEN-CONTAINING BASE ON COMPLEXATION OF OCTA(m-TRIFLUOROMETHYLPHENYL)PORPHYRAZINE AND HEXA(m-TRIFLUOROMETHYLPHENYL)BENZOPORPHYRASINE

The review presents data on the complexation of octa(m-trifluoromethylphenyl)porphy-razine and hexa(m-trifluoromethylphenyl)benzoporphyrazine with zinc acetate in a system nitrogen-containing base - benzene. It was shown that the investigated porphyrazines, having pronounced acidic properties at the incyclic NH bonds, interact with n-butylamine, tret-butylamine, morpholine and piperidine in benzene with the formation of proton-transfer complexes. In these complexes, the intocyclic protons of the NH-groups associated with the oxygen atom of the dimethyl sulfoxide molecule and the intocyclic nitrogen atoms are located above and below the plane of the macrocycle. In an inert, low-polar benzene, the degree of proton transfer from acid to base is limited by the stage of the H-complex (H-associate) formation or ionic complex (ion-ion) associate. It was found that proton transfer complexes of octa(m-trifluoromethylphenyl)porphyrazine and hexa(m-trifluoromethylphenyl)benzoporphyrazine exhibit low kinetic stability. The role of this acid - base interaction in the complexation reaction of octa(m-trifluoromethylphenyl)-porphyrazine and hexa(m-trifluoromethylphenyl)benzoporphyrazine with zinc acetate is shown. High kinetic stability of zinc complexes with the investigated porphyrazines in contrast to complexes with proton transfer was revealed. Based on the analysis of kinetic data, it was found that the introduction of Zn2+ into the coordination center of octa(m-trifluoromethylphenyl)porphyrazine and hexa(m-trifluoromethylphenyl)benzoporphyrazine is preceded by the stage of interaction of porphyrazine with a nitrogen-containing base. This leads to the formation of an intermediate reactive acid-base complex that differs in composition from complexes with proton transfer of porphyrazines. It was shown that piperidine and n-butylamine exert the maximum catalytic effect on the formation of zinc complexes with the investigated porphyrazines. A decrease in the pKa of the nitrogen-containing base, as well as an increase in the spatial shielding of the nitrogen atom in the amine by alkyl substituents, counteracts the formation of an intermediate acid-base complex and, as a result, reduces the complexation rate of octa(m-trifluoromethylphenyl)porphyrazine and hexa(m-trifluoromethylphenyl)benzoporphyrazine with zinc acetate in benzene.

Spectrophotometric Studies on the Reaction of Diaveridine with Some Sulfonphthalein Dyes Based on Ion-Pair/Ion-Associate Complexes Formation

The ion-associate complexes of diaveridine were prepared in a solution and studied spectrophotometrically. The bulky counter anions such as sulfonphthalein acidic dyes, namely, bromocresol green (I), bromophenol blue (II), bromothymol blue (III), bromocresol purple (IV), bromocresol blue (V), o-cresol red (VI), p-cresol blue (VII), and m-cresol purple (VIII) were used for ion-associate complexes formation. The optimal characteristics for the color formation and the stoichiometry of the reaction were evaluated. Spectral characteristics and stability constants of the formed ion associates are discussed in terms of nature of donor and acceptor molecular structures. The molar absorptivities and association constants for the colored complexes were evaluated using the Benesi-Hildbrand equation. Conformity to Beer’s law enabled the assay of dosage form of the drug. The molar absorptivity, specific absorptivity, Sandell sensitivity, correlation coefficient, and detection and quantification limits were also calculated. The methods were validated in terms of accuracy, specificity, precision, and linearity. Also, spectrophotometric determination of the drug in pure and pharmaceutical preparations was tested.