Spectrophotometric determination of some antihistaminic drugs using 7,7,8,8-tetracyanoquinodimethane (TCNQ)

A simple and sensitive spectrophotometric method is suggested for analysis of 3 antihistaminic drugs, acrivastine (I), mequitazine (II), and dimethindene maleate (III). The method is based on reaction of the drugs with 7,7,8,8-tetracyanoquinodimethane (TCNQ) in acetonitrile to form highly stable colored products that are measured at 750, 766, and 844 nm for I and II, and 480 and 618 nm for III. Beer's law is obeyed in the ranges of 5-60 microg/mL for 1, 5-50 microg/mL for II, and 10-70 microg/mL for III. The optimum assay conditions and their applicability to the determination of the cited drugs in pharmaceutical formulations are described. The method is statistically analyzed as compared with the European Pharmacopoeia (2001) method for the analysis of dimethindene maleate and reference methods for acrivastine and mequitazine drugs revealing good accuracy and precision.     

Utility of iodine and 7,7,8,8-tetracyanoquinodimethane for determination of terfenadine

Simple and sensitive spectrophotometric methods for the assay of terfenadine are described. The first is based on the reaction of terfenadine with iodine to give a molecular charge-transfer complex, the terfenadine acting as an n-electron donor and iodine as a sigma-electron acceptor. The second depends on the formation of a highly coloured stable radical anion between terfenadine and 7,7,8,8-tetracyanoquinodimethane (TCNQ) as a pi-electron acceptor. Beer's law is obeyed over the terfenadine concentration range 0.2-1.2 mg/100 ml. The proposed methods have been successfully applied to the analysis of commercial terfenadine tablets.     

Complexes of arenechromium compounds with 7,7,8,8-tetracyanoquinodimethane

Conclusions For the first time complexes of arenechromium compounds with 7,7,8,8-tetracyanoquinodimethane were obtained.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2124–2125, September, 1968.     

7,7,8,8-tetracyanoquinodimethane microsheets for hydrogen peroxide reduction

In this Letter, we demonstrate for the first time that 7,7,8,8-tetracyanoquinodimethane microsheets (TCNQMSs) can effectively catalyze the reduction of H₂O₂ because TCNQ is a strong electron acceptor, TCNQMSs modified glass carbon electrode (GCE) is prepared by a simple casting method. This H₂O₂ sensor shows a fast amperometric response time of less than 3 s, and the corresponding linear range is estimated to be from 3 to 238 mM (r = 0.992) and a detection limit of 4.76 μM at a signal-to-noise ratio of 3. Our present study is important because it provides us a new structure for H₂O₂ detection application.     

Synthesis and structure of complex of 2,3,7,8-tetramethoxythianthrene with 7,7,8,8-tetracyanoquinodimethane

Conclusions The compound of 2,3,7,8-tetramethoxytianthrene with 7,7,8,8-tetracyanoquinodimethane was obtained, which is a charge-transfer complex, and its structure was determined.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 208–211, January, 1977.     

Spectrofluorimetric study of the charge-transfer complexation of certain fluoroquinolones with 7,7,8,8-tetracyanoquinodimethane

Simple, rapid and sensitive spectrofluorimetric methods are described, for the first time, for the determination of ciprofloxacin (CIP), norfloxacin (NOR), pefloxacin (PEF) and fleroxacin (FLE). The methods are based on the charge-transfer (CT) reaction of these drugs as n-electron donors with 7,7,8,8-tetracyanoquinodimethane (TCNQ) as pi-electron acceptor. TCNQ was found to react with these drugs to produce intensely transfer reaction complexes and the fluorescence intensity of the complexes was enhanced in 21-35 fold higher than that of the studied fluoroquinolones itself. The formation of such complexes was also confirmed by both infrared and ultraviolet-visible measurements. The different experimental parameters that affect the fluorescence intensity were carefully studied. At the optimum reaction conditions, the drug-TCNQ complexes showed excitation maxima ranging from 277 to 284 nm and emission maxima ranging from 451 to 458 nm. Rectilinear calibration graphs were obtained in the concentration range of 0.03-0.9, 0.04-1.2, 0.04-1.3 and 0.08-2.4 microg ml(-1) for CIP, NOR, PEF and FLE, respectively. The developed methods were applied successfully for the determination of the studied drugs in their pharmaceutical dosage forms with a good precision and accuracy compared to official and reported methods as revealed by t- and F-tests.     

Ion-radical salt of 2-tert-butyltetrathiatetracene with 7,7,8,8-tetracyanoquinodimethane (2∶1)

Conclusions We synthesized 2-tert-butyltetrathiatetracene and its 2:1 complex with 7,7,8,8-tetra-cyanoquinodimethane, which has an ion-radical nature.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 696–697, March, 1977.The authors express their gratitude to L. I. Buravov for measuring the electrical conductivity.     

Chemical stability and electroconductivity of 7,7,8,8-tetracyanoquinodimethane salts containing polycation polymers

The chemical and electrical stabilities of 7,7,8,8-tetracyanoquinodimethane (TCNQ) salts composed of neutral TCNQ (TCNQ^?), anion radicals of TCNQ(TCNQ^?·), and polycation polymers were studied by measuring their electronic spectra and resistivities (ρ). The results of spectral and chemical analyses confirmed that TCNQ^?· in TCNQ salts was decomposed to α,α-dicyano-p-toluoylcyanide (DTC^?) as the final product by the intermediate formation of TCNQ^? and p-phenylenediamalononitrile (H₂TCNQ) and that H₂O played an important part in the reaction. From these results it was concluded that TCNQ salts are decomposed by two reaction processes: The resistivity of TCNQ salts increases with the decomposition of TCNQ^?·. Studies on electroconductivity of TCNQ salts assume that the change in resistivity arises from the loss of unpaired electrons which become conduction carriers and also from the disintegration of the TCNQ^? and TCNQ^?· complex which forms the conduction path.     

Spectrophotometric determination of some vic-diols

Conditions have been established for the determination of mannitol and sorbitol (0.4–14 μg), mannose (3.6–18 μg), myoinositol (1.5–6 μg) and pinacol (11–70 μg) by periodate oxidation. The iodate formed is determined spectrophotometrically by reaction with iodide to form tri-iodide. Exce'ss of periodate is masked with molybdate.     

Spectrophotometric determination of some dithiocarbamates

A procedure has been developed for the determination of six dithiocarbamates [sodium dimethyldithiocarbamate (dibam), sodium diethyldithiocarbamate (NaDDC), tetramethylthiuram disulphide (thiram), zinc dimethyldithiocarbamate (ziram), sodium N-methylpiperazinecarbodithioate and potassium morpholine-4-carbodithioate] in microgram quantities by converting them into selenium dithiocarbamate complexes, which are then extracted into chloroform and measured at 430 nm against a reagent blank. The method is sensitive and can be used for the determination of dithiocarbamates in commercial samples and synthetic mixtures.     

Utility of 7,7,8,8-tetracyanoquinodimethane charge transfer reagent for the spectrophotometric determination of trazodone, amineptine and amitriptyline hydrochlorides

A simple and rapid spectrophotometric method has been developed for the determination of tricyclic anti-depressant drugs such as trazodone (TZH), amineptine (APH) and amitriptyline (ATPH) hydrochlorides in pure form and in different pharmaceutical preparations. The charge transfer (CT) reaction between TZH, APH and ATPH as electron donors and TCNQ as electron acceptor was utilized for their spectrophotometric determination. The optimum experimental conditions, like time, temperature, stoichiometry, solvents, for the CT complex formation are established. The method permits the determination of TZH, APH and ATPH over a concentration range of 10-400, 10-440 and 10-300 microg ml(-1), respectively. The sensitivity (S) is found to be 0.09, 0.087 and 0.069 g cm(-2) for TZH, APH and ATPH, respectively. The SD values are found to be 0.146-0.293, 0.154-0.285 and 0.091-0.212 and RSD values are 0.142-1.92, 0.297-1.92 and 0.212-0.915 for TZH, APH and ATPH, respectively. The low values of the relative standard deviation indicate the high accuracy and precision of the method. The mean recovery values obtained together with a high correlation coefficient values, amount in the range 98-101.5, 98.7-102.9 and 93-101.9 for TZH, APH and ATPH, respectively. The method is applicable for the assay of the investigated drugs in different dosage forms and the results are in good agreement with those obtained by the official method.     

Reactions of hexamethyldilead with 7,7,8,8-tetracyanoquinodimethane (TCNQ) and tetracyanoethylene (TCNE)

Hexamethyldilead reacts with TCNQ to give Pb(TCNQ)₂ and tetramethyllead and with TCNE to give Pb(TCNE).