Titrimetric estimation of phosphate, molybdate, tungstate and sulphate with lead nitrate solution, using 1,2-naphthoquinone-2-semicarbazone-4-sulphonic acid (NQS-4S) and 1,2-naphthoquinone-2-thiosemicarbazone-4-sulphonic acid (NQTS-4S) as visual indicators

The use of 1,2-naphthoquinone-2-semicarbazone-4-sulphonic acid and 1,2-naphtho-quinone-2-thiosemicarbazone-4-sulphoic acid as indicators in the titrimetric estimation of phosphate, molybdate, tungstate and sulphate with lead has been examined. The precision, accuracy and applicability of the methods have been evaluated.     

Reaction of some sympathomimetic amines with sodium 1,2-naphthoquinone-4-sulphonate

Summary The condensation products of 4 sympathomimetic amines with 1,2-naphthoquinone-4-sulphonic acid have been prepared and examined. A spectrophotometric procedure based on the chloroform-soluble orange-red condensation product is described. The same products were investigated fluorimetrically after reduction with sodium borohydride. The results obtained are satisfactory.

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Zusammenfassung Die Kondensationsprodukte vier sympathicomimetischer Amine mit 1,2-Naphthochinon-4-sulfonsäure wurden dargestellt und untersucht. Ein spektralphotometrisches Verfahren auf der Grundlage des chloroformlöslichen, orangeroten Kondensationsproduktes wurde beschrieben. Die gleichen Produkte wurden auch fluoreszenzanalytisch nach ihrer Reduktion mit Natriumborhydrid untersucht. Die Ergebnisse sind befriedigend.

     

Determination of vigabatrin in human plasma and urine by high-performance liquid chromatography with UV-Vis detection

A simple and reliable high-performance liquid chromatographic (HPLC) method with UV-Vis detection has been developed and validated for the determination of vigabatrin (VG) in human plasma and urine. The samples were pre-column derivatizated with 1,2-naphthoquinone-4-sulphonic acid sodium salt (NQS). A good chromatographic separation was achieved on a C18 column with a mobile phase consisting of acetonitrile and 10 mM orthophosphoric acid (pH 2.5) gradient elution. Tranexamic acid was used as an internal standard (I.S.). The method was linear over the concentration range of 0.8-30.0 microg/ml for both samples. The method is precise (relative standard deviation (R.S.D.) <9.13%) and accurate (relative mean error (RME) <-8.75%); analytical recoveries were 81.07% for plasma and 83.05% for urine. The assay was applied to pharmacokinetic study in a healthy volunteer after a single oral administration of 1 g of vigabatrin.     

In Process Citation

Aromatic nitro compounds are reduced to aromatic amines by iron(II) in alkaline medium. The dye obtained by reacting the amine with 1,2-naphthoquinone-4-sulphonic acid is extractable into methylene chloride. Reduction by potassium borohydride yields a fluorescent o-diphenol, thus allowing the fluorimetric estimation of aromatic nitro compounds on the microgram scale.

Zusammenfassung

Aromatische Nitroverbindungen werden durch Eisen(II) in alkalischem Medium zu aromatischen Aminen reduziert. Setzt man das Amin mit 1,2-Naphthochinon-4-sulfonsäure um, so läßt sich der erhaltene Farbstoff in Methylenchlorid extrahieren. Reduktion mit Kaliumborhydrid liefert ein fluoreszierendes o-Diphenol; damit wird die fluorimetrische Bestimmung aromatischer Nitroverbindungen im Mikrogramm-Maßstab möglich.     

A spectral study of tautomerism in 4-arylamino-1,2-naphthoquinones

The tautomerism of 4-arylamino-1,2-naphthoquinones in aqueous solutions has been investigated by UV-visible absorption spectroscopy. It has been demonstrated that in strongly acidic solutions (Ph 0·8), protonation of the 2-keto group leads to 2-hydroxy-1,4-naphthoquinone-4-arylimine as the more stable tautomer. However, weakly acidic or alkaline solutions (Ph 4–13) contain 4-arylamino-1,2-naphthoquinone as the more stable tautomer.     

衍生化分光光度法测定依诺沙星和诺氟沙星

碱性介质中,依诺沙星和诺氟沙星均能与1,2-萘醌-4-磺酸钠(NQS)发生反应而生成橙红色的物质,并使最大吸收波长发生大幅度的红移。据此建立了测定这两种药物的分光光度新方法。依诺沙星和诺氟沙星的浓度分别在0.8~16 mg.L-1和0.9~18 mg.L-1范围内符合比耳定律;衍生物在454 nm和462 nm波长处的表观摩尔吸光系数分别为1.86×104L.mol-1.cm-1和1.93×104L.mol-1.cm-1;两种药物的检出限分别为0.13 mg.L-1和0.19 mg.L-1。该方法已成功用于药物制剂中依诺沙星和诺氟沙星含量的测定。其回收率为96.63%~99.55%,相对标准偏差为0.56%~0.89%。     

The preparation,spectra and tautomerism of some 4(n-arylamino)-1,2-naphthoquinones

Twelve 4(N-arylamino)-1,2-naphthoquinones (1) have been prepared by the direct addition of substituted anilines to 1,2-naphthoquinone, and their spectra have been studied. In the solid and in ethanol solution the 1,2-naphthoquinone tautomer (1a) predominates, but in trifluoroacetic acid the 2-hydroxy-1,4-naphthoquinone-4-aryliminium (2a) is the major species.     

Spectrophotometric determination of aminomethylbenzoic acid using sodium 1,2-naphthoquinone-4-sulfonate as the chemical derivative chromogenic reagent

A new method has been established for the determination of aminomethylbenzoic acid using sodium 1,2-naphthoquinone-4-sulfonate as the chemical derivative chromogenic reagent. This method is based on the formation of a pink compound from the reaction of aminomethylbenzoic acid and sodium 1,2-naphthoquinone-4-sulfonate. The nucleophilic substitution reaction proceeds quantitatively in pH 12.0 buffer solution. The stoichiometric ratio of the reaction, maximum absorption wavelength and the value of epsilon(430) were 1:1, 430 nm, and 2.87 x 10(3)L mol(-1)cm(-1), respectively. Beer's law was obeyed in the range of 0.80-80 mg/L of aminomethylbenzoic acid. The data have been filled to a linear regression equation A=0.03183+0.01658C (mg/L), with a correlation coefficient of 0.9996. The detection limit is 0.11 mg/L, R.S.D. is 0.54%, and average recovery is over 99.6%. This paper further improves the determination of aminomethylbenzoic acid compared to the previous methods. The kinetic property and reaction mechanism have also been discussed. This proposed method has been successfully applied to the determination of aminomethylbenzoic acid in injection of aminomethylbenzoic acid with satisfactory results.     

Spektrofluorometrische bestimmung von hydrazinen und deren anwendung zur quantitativen bestimmung von benzylhydrazin in biologischen proben

A spectrofluorometric determination of strong reducing substances such as hydrazine and alkylhydrazines is described. It is based on the reduction of 1,2-naphthoquinone-4-sulfonic acid to the fluorescent 1,2-dihydroxynaphthalene-4-sulfonic acid. The assay of microgram quantities of hydrazines in blood plasma and of benzylhydrazine in animal organs and urine is reported.     

Complexometric Determination of Trivalent Metal Ions Using 1,2-Naphthoquinone-4-Sulphonic Acid-2-Thiosemicarbazone as Metallochromic Indicator

1,2-Naphthoquinone-4-sulphonic acid-2-thiosemicarbazone (NQTS-4S) has been used as visual indicator in the complexometric determination of trivalent metal ions, aluminium, gallium, indium, bismuth and iron. Simultaneous determination of aluminium and iron and of aluminium and copper has also been carried out. The standard deviation and percentage errors have also been calculated.     

Rapid estimation of trace amounts of ethylenimine by high-pressure liquid chromatography.

A rapid procedure utilizing high-pressure liquid chromatography is described for determining trace quantities of ehtylenimine down to 0.01 ppm. The basis for the method is the quantitative reaction of ethyleneimine with the 1,2-naphthoquinone-4-sulphonate ion (Folin's reagent) to give 4-(1-aziridinyl)-1,2-naphthoquinone. Compared with the spectrophotometric procedure, this method provides a high degree of specificity and sensitivity. The method has been employed to determine ethylenimine in the pyrolysis products of polyethylenimine.     

Determination of thermodynamic parameters and equilibrium constants for complexation reactions involving lanthanon(III) ions with 1,2-naphthoquinone-2-semicarbazone-4-sulphonic acid (sodium salt) (NQS · 4S)

The thermodynamic parameters and equilibrium constants of complexation reactions of 1,2-naphthoquinone-2-semicarbazone-4-sulphonic acid (sodium salt) (NQS · 4S) involving lanthanon ions were evaluated by potentiometric estimation of [H⁺], in aqueous medium at various ionic strengths (0.02, 0.05, 0.10 and 0.20 M NaClO₄) and at different temperatures (20, 30, 40 and 50±0.5°C). The −n and pL values calculated by the method of Bjerrum and Calvin, as modified by Irving and Rossotti, were used for the calculation of the equilibrium constants on an HCL Busy Bee PC/AT computer using the weighted least-squares method. The values of S_min were also evaluated. The order of equilibrium constants was found to be Ho(III) > Dy(III) > Tb(III) > Y(III) > Eu(III) > Sm(III) > Gd(III) > Nd(III) > Pr(III) > Ce(III) > La(III). The thermodynamic parameters ΔG, ΔH and ΔS were also calculated at a fixed temperature (30±0.05°C) and ionic strength (0.10 M NaClO₄).     

衍生化-离子液体萃取分光光度法测定盐酸美西律

盐酸美西律与1,2-萘醌-4-磺酸钠在pH=9.0的介质中反应生成一种橙红色衍生物,该衍生物能被离子液体所萃取,其最大吸收波长发生较大幅度红移,吸光度显著增强。据此建立了高选择性的测定盐酸美西律的衍生化-离子液体萃取分光光度法。萃取后的衍生物在448 nm处的表观摩尔吸光系数ε为2.69×104L·mol-1·cm-1。盐酸美西律浓度在0.2～5.4μg·mL-1范围内符合比耳定律,相关系数为0.9994,检出限为0.067μg·mL-1。该方法已用于药物制剂及尿样中盐酸美西律的测定,其回收率分别为99.5%～100.7%和96.6%～101.5%。     

Continuous flow derivatization system coupled to capillary electrophoresis for the determination of amino acids

A derivatization system coupled to capillary electrophoresis for the determination of amino acids using 1,2-naphthoquinone-4-sulfonate as a labeling agent is described. In this system, amino acids are derivatized on-line in a three-channel flow manifold for sample, reagent and buffer solutions. The reaction takes place in a PTFE coil heated at 80 degrees C. The resulting solution, which contains the amino acid derivatives, is introduced into the electrophoretic system by means of an appropriate interface. Subsequently, amino acid derivatives are separated at 25 kV using a 40 mM sodium tetraborate aqueous solution with 30% (v/v) isopropanol solution as a running buffer. The electropherograms are monitored spectrophotometrically at 230 nm. The method has been applied to the determination of amino acids in feed samples and pharmaceutical preparations. A good concordance of the predicted values with those given by a standard amino acid analyzer is shown.     

The use of naphthalene derivatives in inorganic analysis : V. further applications of the nitroamino-naphthalene monosulphonic acids to the flourimetric detection of stannous tin

Three new reagents, viz 5-nitro-1-aminonaphthalene-2-sulphonic acid,4-nitro-1-aminonaphthalene-5-sulphonic acid and 4-nitro-1-aminonaphthalene-6-sulponic acid, have been found to be of use as fluorimetric spot tests on filter paper for stannous tin. The orientation of the sulphonic acid group does not appear to appreciably affect the sensitivity of the test, approximately one microgram of stannous tin being capable of detection by all isomers     

Study of methanol catalyzed reaction between sodium 1,2-naphthoquine-4-sulfonate and hydroxyl ion and its application in the determination of methanol

A novel and simple spectrophotometric method for the direct determination of methanol with 1,2-naphthoquinone-4-sulfonate (NQS) is developed in this paper. It is based on the fact that methanol can catalyze the reaction between 1,2-naphthoquinone-4-sulfonate and hydroxyl ion to form 2-hydroxy-1,4-naphthoquinone in buffer solution of pH 13.00. Beer's law is obeyed in a range of 0.26-15.8 mg/ml at the maximal absorption wavelength of 454 nm. The equation of linear regression is A = 0.01998 + 0.05944C (mg/ml), with a linear regression correlation coefficient of 0.9977. The detection limit is 0.25mg/ml (3sigma/k), while R.S.D. is 2.0% and the recovery rate is in a range of 96.5-103%. The detailed mechanism for the formation of the products is proposed and discussed.     

Allgemeine Basenkatalyse der Azokupplung von o-Diazophenolen. 19. Mitteilung zur Kenntnis der Azokupplungsreaktion

1. The kinetics and the mechanism of the diazo coupling reaction of 2-diazophenol-4-sulphonic acid with 1-naphthol-2-sulphonic acid have been investigated at 0° and ionic strength I=0.45. 2. The pK_a-value of the hydroxyl group in 2-diazophenol-4-sulphonic acid has been determined: pK_a=- 0.04 ± 0.10. It is the diazonium-phenolate anion which actually enters into the diazo coupling reaction. 3. The reaction is subject to general base catalysis. It is shown that no intermediate is enriched during the reaction at pH 11.3–11.6 which proceeds by a two-step mechanism with a steady state intermediate.     

Studies on oxine and its derivatives : The sensitivity and selectivity of some 7-substituted 8-hydroxyquinoline-5-sulphonic acids and some 2-substituted 8-hydroxyquinoline-4-carboxylic acids towards certain metals

A number of new derivatives of 8-hydroxyquinoline containing both solubilising groups and groups which might sterically hinder chelation have been prepared, viz. 8-hydroxy-7-morpholino-methylquinoline-5-sulphonic acid, 8-hydroxy-7-piperidinomethylquinoline-5-sulphonic acid, 8-hydroxy-2-(3,4-dimethoxyphenyl)-quinoline-4-carboxylic acid, 8-hydroxy-2-n-hexylquinoline-4-carboxylic acid and 8-hydroxy-2-(i-ethylpropyl)-quinoline-4-carboxylic acid. The limiting sensitivities of the reactions of these reagents towards copper, nickel, aluminium, zinc, magnesium, gallium, indium, thallium, yttrium, cadmium, cobalt and iron have been investigated     

The use of naphthalene derivatives in inorganic analysis : A new reagent for the fluorimetric detection of tin

The use of 6-nitro-2-hydroxy-naphthalene-8-sulphonic acid as a new fluorimetric reagent for the detection of tin has been reported. This reagent is capable of detecting 10^-8 g stannous tin under the conditions of the test and is slightly more sensitive for this purpose than the previously recommended 6-nitro-2-aminonaphthalene-8-sulphonic acid.     

Synthesis, Characterization and Antiproliferative Activity of 1,2-Naphthoquinone and Its Derivatives

In the present study substituted 1,2-naphthoquinones were synthesized, purified and characterized by spectroscopic studies (UV, FT-IR, ¹H NMR, ¹³?C NMR and elemental analysis). These compounds were evaluated for cytotoxicity against a panel of human cancer cell lines (Hep-G₂ for liver sarcoma_, MG-63 for osteosarcoma and MCF-7 for human breast cancer). The cells were dosed with these ortho-naphthoquinone derivatives at varying concentrations, and cell viability was measured by a 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay with doxorubicin as positive control. Significant anticancer activities were observed in vitro for some members of the series, and compounds 1,2-naphthoquinone 2-thiosemicarbazone (3), 1,2-naphthoquinone-2-semicarbazone (4), 4-amino-1,2-naphthoquinone 2-thiosemicarbazone (7) and 4-amino-1,2-naphthoquinone-2-semicarbazone (8) are active cytotoxic agents against different cancer cell lines with IC₅₀ values in the range of 5.73?C17.67???M. The obtained data suggested that better anticancer activity was linked with introduction of thiosemicarbazone and semicarbazone moiety in 1,2-naphthoquinone ring system. Outcomes of experimentation also reveal that incorporation of amino group in 1,2-naphthoquinone moiety contributes positively for cytotoxic action of compounds. Docking experiments showed a good correlation between their calculated interaction energies with the topoisomerase-II and the observed IC₅₀ values of all these compounds.