A high-sensitive spectrofluorimetric method for the determination of micromolar concentrations of iron(III) in bovine liver with 4-hydroxyquinoline.

A new sensitive, rapid and accurate spectrofluorimetric method, suitable for the determination of micromolar concentrations of iron(III) in bovine liver, using 4-hydroxyquinoline (4-HQ) in an alkaline medium (KOH 2.0 x 10(-2) mol/l) as fluorescent agent, is described. The fluorescence intensity of the working solutions was measured at lambda ex 305 nm and lambda em 380 nm. The observed decrease of the above mentioned intensity was mainly due to the quenching, caused by the interaction between the iron(III) to be analysed and the potentially fluorescent 4-HQ. The accuracy and the precision of the proposed method, after an experimental investigation, could be considered as very satisfactory. Potassium fluoride and triethylenetetramine solutions were successfully used for the masking of those metal cations existing in the bovine liver which interfere seriously with the determination of iron(III).

A new indirect spectrofluorimetric determination of sub-micromolar concentrations of manganese(II) in bovine liver by means of 2-hydroxyquinoline.

A new high-sensitive and at the same time accurate and well documented indirect spectrofluorimetric method for the determination of sub-micromolar concentrations of manganese(II) being as a normal trace element in the bovine liver, was described. The purpose of the experimental work is performed by means of two fluorescence intensity measurements; the measurement of the fluorescence (F1) of a 2.0 x 10(-5) mol/l solution of pure 2-hydroxyquinoline (2-HQ) (lambda ex: 320 nm: lambda em: 375 nm), and that of the fluorescence of the above solution after the addition of Mn(II) to be analyzed (F2). The observed difference of the fluorescence intensities measured (F1-F2) = delta F, is exclusively owed to the quenching of the Mn(II) on the free 2-HQ. The presence of various metal ions considerably interferes with the above described determination of Mn(II). For this reason, the separation and/or masking of these undesirable metal ions it is advisable to apply before any analytical praxis.

Analytical investigation of beta-lactam antibiotics in pharmaceutical preparations. IX. Colorimetric determination of six cephalosporins of second and third generation in the range of micromolar concentrations.

A sensitive, accurate, precise and the same time simple and rapid method for the colorimetric determination of some cephalosporins of the second and third generations, such as: cefoxitin sodium (CFXT), cefaclor (CFCL), cefamandole nafate (CFMD), ceforanide l-lysine (CFRN), cefotaxime sodium (CFTX), and cefurozime sodium (CFRX) was described. The new method proposed is based: a) On the reduction of Fe(III) to Fe(II) by the drug analysed and b) On complexation of Fe(II) formed with o-Phenanthroline (O-Phen) consistently the formation of the well known highly stable orange-red coloured chelate complex [Fe(II)-(o-Phen)3]2+ which exhibits an absorption maximum at lambda = 510 nm (pH 4.50 +/- 0.2). Beer's law is obeyed for: 1.0 - 37.5 microgram mL-1 for CFX, 1.0 - 25.0 microgram mL-1 for CFMD, CFRN, and CFTX and 2.0 - 37.5 microgram mL-1 for CFTX and CFCL, while the apparent molar absorptivity ( epsilon in L mol-1cm-1) and the Sandell's sensitivity in (ngcm-2) both referred to the drug analyzed, are 1.29 x 10(4); 34.7 (CFXT), 7.61 x 10(3); 50.7 (CFCL), 3.33 x 10(4); 15.4 (CFMD), 2.60 x 10(4); 17.6 (CFRN) respectively. The regression line equation for each one of the above studied cephalosporins were calculated with a correlation coefficient 0.9997 < r < 1.0000; the accuracy and the precision of the method was considered as very satisfactory, while the results of a statistical analysis by means of the Student's t-test and the variance ratio F-test prove that no significant difference was observed between the results of the proposed method and those of official one.

Analysis of various very slightly water soluble drugs in micellar mediumII. Potentiometric and visual determination of sulphamethoxazole in pure for.

A potentiometric and/or visual method for the determination of sulphamethoxazole (SULF) in pure form in the range of 5.3 x 10(-5) to 5.0 x 10(-4) mol/L is proposed. To enhance the solubility, the determination has been carried out in a micellar medium formed by an aqueous 5.0 x 10(-2) mol/L N-hexadecyl-N,N,N-trimethyl ammonium bromide (CTAB) solution which increases the dissociation constant K(alpha) of SULF about tenfold. The titration is performed with NaOH (2.5 x 10(-3) or 5.0 x 10(-2) mol/L) and the end-point is determined by the second derivative graph. The results agree with those obtained by the official method of the USP XXIII. The method is simple, accurate, economical and can successfully replace the more complicated, more expensive and time-consuming existent procedures which are carried out in a non-aqueous medium.

Application of ternary complexes in pharmaceutical analysis. IV--Spectrophotometric determination of iron (II) in anti-anaemic formulations, using as chelating ligands in micellar medium three newly developed hydrazones.

The preparation, structural and physicochemical characterisation of three new hydrazones of isoniazid with 2,3-dihydroxy-,3,4-dihydroxy- and 2,3,4-tri-hydroxybenzaldehyde are described. The formation of binary chelates of iron(III) with these hydrazones and ternary complexes with the hydrazones and various surfactants were studied including the optimization of the experimental conditions. The new reagents were successfully used for the spectrophotometric determination of iron(II) in anti-anaemic formulations after its oxidation with hydrogen peroxide to iron(III). The statistical comparison of the results obtained with the new reagents and with the classical o-phenanthroline method is presented.

Spectrophotometric method for the determination of carbidopa using neotetrazolium chloride.

A new high-sensitive spectrophotometric method for the determination of microquantities of carbidopa is described. The method is based on the reduction of neotetrazolium chloride by carbidopa in an alkaline ethanolic medium. The formazan formed exhibits an absorption maximum at lambda = 507 nm, with an apparent molar absorptivity of epsilon = 6.63 x 10(4) M-1 cm-1 and a corresponding Sandell's sensitivity of 3.68 ng cm-2. Beer's law is obeyed over the range of 0.10-6.0 micrograms mL-1 while the optimum concentration range is 0.125-5.0 micrograms mL-1. The regression line equation was calculated as: A = 0.271C + 0.0023 with a correlation coefficient of 1.0000 (n = 28). The accuracy and the precision of the method were considered as very satisfactory. The results obtained from the determination of carbidopa using both the described procedure and the corresponding USP. XXII and BP 1988 clinical methods were statistically compared by means of Student's t-test as well as by the variance ratio F-test, and no significant difference was observed.

A sensitive spectrophotometric determination of acetaminophen.

A sensitive, accurate and precise spectrophotometric method is described for the determination of Acetaminophen (paracetamol, ACTP) in pure form and in pharmaceutical formulations. The principle of the method is the reduction, of Fe(III) to Fe(II) by the ACTP in the presence of o-Phenanthroline (o-Phen), when the orange-red coloured chelate complex [Fe(II)-(o-Phen)3]2+ the ferroin complex was formed, and its absorbance was measured at lambda = 510 nm. The apparent molar absorptivity, referred to ACTP was 3.16 x 10(4) 1 mol-1 cm-1 and the Sandell's sensitivity was calculated as 4.8 ng cm-2. The calibration graph was rectilinear over the range 0.25-10.0 ppm of ACTP and the regression equation was calculated as A = 2.06 x 10(-1) C + 4.78 x 10(-3) with a correlation coefficient of 0.9999 (n = 8). A statistical analysis by means of the Student's t-test as well as by the variance ratio F-test, indicates that the proposed new method is equivalent to the corresponding B. P. 1988 and U. S. P. XXII official methods with regard to accuracy and precision.

Sensitive colorimetric assay of carbidopa and methyldopa using tetrazolium blue chloride in pharmaceutical products.

A colorimetric method for the assay of carbidopa and methyldopa either in pure form or in pharmaceutical preparations is described. The method is based on the reduction of tetrazolium blue chloride in a non-aqueous alkaline medium by the substances analysed, and the measurement of the absorbance of the pink-coloured diformazan solution, which is caused by this reduction. The spectra of the aforesaid solutions exhibit an absorption maximum at lambda = 525 nm. The apparent molar absorptivities and Sandell's sensitivities (in l.mol-1.cm-1 and ng.cm-2, respectively) are 1.2.10(5) and 1.9 for carbidopa and 7.07.10(4) and 3.0 for methyldopa. The solution of diformazan formed obeys Beer's law in the concentration range of 0.05-4.0 ppm for carbidopa and 0.1-6.0 ppm for methyldopa. The slope and intercept of the corresponding regression line equation were obtained with a correlation coefficient of 0.9999 for carbidopa and 0.9994 for methyldopa. The variables affecting the development of the colour are investigated and the conditions are optimized. Compared with other procedures this method showed to be more simple and rapid, highly sensitive, precise and accurate. Results obtained by application of the proposed method and the official one, were in good agreement, while statistical comparison by the Student's t-test shows no significant difference between the two sets of the results.

Spectrophotometric determination of trace amounts of iron(III) with norfloxacin as complexing reagent.

The complexation of iron(III) with norfloxacin in acidic solution at 25 degrees C, at an ionic strength of about 0.3 M and a pH of 3.0 has been studied. The water-soluble complex formed, which exhibits an absorption maximum at 377 nm, was used for the spectrophotometric determination of trace amounts of iron(III). The molar absorptivity was 9.05 x 10(3) I mol-1 cm-1 and the Sandell sensitivity 6.2 ng cm-2 of iron(III) per 0.001 A. The formation constant (Kf) was determined spectrophotometrically and was found to be 4.0 x 10(8) at 25 degrees C. The calibration graph was rectilinear over the range 0.25-12.0 p.p.m. of iron(III) and the regression line equation was A = 0.163c - 0.00042 with a correlation coefficient of 0.9998 (n = 9). Common cations, except cerium (IV), did not interfere with the determination. The results obtained for the determination of iron(III) using the described procedure and the thiocyanate method were compared statistically by means of the Student t-test and no significant difference was found.

Spectrophotometric determination of certain cephalosporins using molybdophosphoric acid. Part II. Determination of cefadroxil, cefapirin, ceforanide and cefuroxime.

The use of molybdophosphoric acid as an oxidising agent for the spectrophotometric determination of four cephalosporin derivatives, viz., cefadroxil monohydrate (I), cefapirin sodium (II), ceforanide L-lysine (III) and cefuroxime sodium (IV), either in the pure form or in pharmaceutical formulations is described. Beer's law is obeyed up to 100 micrograms ml-1 for I, up to 60 micrograms ml-1 for II and IV and up to 80 micrograms ml-1 for III. The molar absorptivities were 4.58 X 10(3), 11.3 X 10(3), 9.8 X 10(3) and 10.9 X 10(3) l mol-1 cm-1 and the Sandell sensitivities were 83.3, 39.3, 53.0 and 41.0 ng cm-2 for I, II, III and IV, respectively. The slopes and intercepts of the equations of the regression line were calculated for each of these drugs with the following correlation coefficients: I, 0.9993; II, 0.9999; III, 1.000; and IV, 0.9999. These antibiotics were determined successfully both in the pure form and in pharmaceutical preparations. The results demonstrated that the proposed procedure is at least as accurate, precise and reproducible as the official methods, while being simpler and less time consuming. A statistical analysis indicated that there was no significant difference between the results obtained by the proposed procedure and those of the official methods.

Spectrophotometric determination of microquantities of Carbidopa, Levodopa and alpha-methyldopa using molybdatophosphoric acid.

A convenient spectrophotometric procedure for the determination of microquantities of Carbidopa (I), Levodopa (II) and alpha-methyldopa (III) was developed. The method was based on the interaction of acidified molybdatophosphoric acid (MPA) solution with (I), (II) and (III). The resulted deep blue solution was measured spectrophotometrically at lambda = 600-900 nm. The molar absorptivities (epsilon) and the Sandell's sensitivity for (I), (II) and (III) were: 2.4 x 10(4) (I), 3.0 x 10(4) (II), 3.1 x 10(4) (III) and 10.2 ng.cm-2 (I), 6.6 ng.cm-2 (II) and 7.7 ng.cm-2 (III), respectively. The calibration curves were conformed to Lambert-Beer's law between 0.5 and 10.0 micrograms.ml-1.