Simultaneous Spectrophotometric Determination of Paracetamol and P‐Aminophenol by Using Mean Centering of Ratio Kinetic Profiles

A specific spectrophotometric method was developed for simultaneous determination of paracetamol (PCT) and p‐aminophenol (PAP) in water samples without prior separation steps. The method is based on the mean centering of ratio kinetic profiles. Paracetamol and P‐aminophenol react with Fe(III)/hexacyanoferrate(III) complex and result in the formation of colored complex, i.e. Prussian Blue. The differences in the rate of reaction of PCT and PAP with reagents make their simultaneous determination feasible by using mean centering of ratio kinetic profiles. The experimental parameters, such as reagent concentrations and pH were optimized for getting results with minimum errors. The analytical characteristics of the method such as detection limit, accuracy, precision, relative standard deviation (R.S.D.) and relative standard error (R.S.E.) for the simultaneous determination of binary mixtures of p‐aminophenol and acetaminophen were calculated. The results show that the method was capable of simultaneous determination of 0.5–21.0 μg mL⁻¹ and 0.1–15.0 μg mL⁻¹ of PCT and PAP, respectively. The proposed method was successfully applied to the simultaneous determination of paracetamol and p‐aminophenol in several pharmaceutical products and synthetics mixtures.     

Mean centering of ratio spectra as a new spectrophotometric method for the analysis of binary and ternary mixtures

In this paper a new and very simple method was developed for the simultaneous determination of binary and ternary mixtures, without prior separation steps. This method is based on the mean centering of ratio spectra. The mathematical explanation of the procedure is illustrated. After modeling procedure, the method has been successfully applied to the simultaneous analysis of binary mixtures of mefnamic acid and paracetamol and ternary mixtures of acetylsalysilic acid, ascorbic acid and paracetamol. The analytical characteristics of the method such as detection limit, accuracy, precision, relative standard deviation (R.S.D.) and relative standard error (R.S.E.) was calculated. The results showed that the proposed method is simple, rapid, accurate and precise method for analysis of binary and ternary mixtures.     

Simultaneous Spectrophotometric Determination of Aluminum and Iron in Micellar Media by Using the H‐Point Standard Addition Method

A very simple spectrophotometric method for simultaneous determination of aluminum(III) and iron(III) based on formation of their complexes with pyrocatechol violet (PCV) in micellar media, using the H‐point standard addition method (HPSAM), is described. In micellar media, the metal complexes of Al‐PCV and Fe‐PCV are formed very fast. Formation of both of the complexes was complete within 5 min at pH 8.5. The linear ranges for aluminum and iron were 0.05‐2.50 and 0.10‐4.00 μg mL^?1, respectively. The relative standard deviation (R.S.D.) for the simultaneous determination 0.40 μg mL^?1 of Al(III) and 0.20 μg mL^?1 of Fe(III) were 3.24% and 4.22%, respectively. Interference effects of common anions and cations were studied. The method was applied to simultaneous determination of Al(III) and Fe(III) in standard reference material and alloy samples.     

H-point standard addition method for simultaneous spectrophotometric determination of Co(II) and Ni(II) by 1-(2-pyridylazo)2-naphthol in micellar media

A very simple and selective spectrophotometric method for simultaneous determination of Co(II) and Ni(II) by 1-(2-pyridylazo) 2-naphthol (PAN), in micellar media, using H-point standard addition method (HPSAM) is described. The ligand and its metal complexes (Co(II)-PAN and Ni(II)-PAN) were made water-soluble by the neutral surfactant Triton X-100, and therefore, no extraction with organic solvents was required. Formation of both the complexes was complete within 10 min at pH 9 (adjusted by ammonia buffer). The linear range was 0.10-2.00 microg ml(-1) for Co(II) and 0.05-1.50 microg ml(-1) for Ni(II). The relative standard deviation (R.S.D.) for the simultaneous determination of 0.50 microg ml(-1) each of Co(II) and Ni(II) was 2.32 and 3.13%, respectively. Interference effects of common anions and cations were studied and the method was applied to simultaneous determination of Co(II) and Ni(II) in alloy samples. The method was compared with derivative spectrophotometric method.     

Flow-injection catalytic kinetic determination of manganese using stopped-flow and gradient calibration

Based on the principle of Mn(II) catalysis of the Tiron-hydrogen peroxide reaction, a catalytic kinetic spectrophotometric determination of traces of manganese (ca. 10^?7 M) by flow injection was established. In combination with a microcomputer, by using gradient dilution and the stopped-flow method, onlya single standard solution was needed for calibration. The method has a high selectivity and a sampling rate of 40 h^?1. Traces of manganese in natural water were determined with a maximum relative standard deviation of 5.5% (n = 6).     

Spectrophotometric study of reactions of scandium,ytrium and lanthanum ions with some triphenylmethane dyes in the presence of cationic surfactants

Optimum conditions for the formation of ternary complexes of scandium, ytrium and lanthanum ions with chrome azurol S, eriochrome cyanine R and pyrocatechol violet in the presence of cetyltrimethylammonium, cetypyridinium and tetradecyldimethylbenzyl-ammonium (zephiramine) ions are described. The spectrophotometric determination of scandium with chrome azurol S and zephiramine exhibits the greatest sensitivity (? = 1.50 × 10⁵ l mol^?1 cm^?1 at 610 nm). In the spectrophotometric determination of scandium with eriochrome cyanine R and cetylpyridinium ion (? = 9.2 × 10⁴ at 600 nm), the interference caused by yttrium is the least. In the best method for yttrium (with pyrocatechol violet and zephiramine), the molar absorptivity is 3.3 × 10⁴ at 660 nm. Lanthanum does not form ternary complexes of analytical interest in these systems. Some aspects of the formation of ternary complexes with cationic surfactants are discussed.     

Simultaneous kinetic determination of beryllium and aluminium by spectrophotometric H-point standard addition method.

The H-point standard addition method (HPSAM), based on spectrophotometric measurements for simultaneous determination of beryllium and aluminium, is described. This method is based on the difference between their rates of reactions with Chrome Azurol S (CAS) in cetyltrimethylammonium bromide (CTAB) micellar media. The results showed that beryllium and aluminium could be determined simultaneously in the ranges of 10-200 and 10-300 ng mL(-1), respectively. Under working conditions, the proposed method was successfully applied to the simultaneous determination of beryllium and aluminium in environmental, geochemical and alloy samples.     

Flow-injection spectrophotometric determination of methyldopa in pharmaceutical formulations

A flow-injection spectrophotometric procedure is proposed for methyldopa determination in pharmaceutical preparations. The determination is based on formation of a yellow product (measured at 410 nm) after complexation of methyldopa with molybdate. Under optimal conditions, Beer's law is obeyed in a concentration range of 50-200 mg l⁻¹ methyldopa. Typical correlation between absorbance and analyte concentration was 0.9999. Usual excipients used as additives in pharmaceuticals do not interfere with the proposed method. The analytical frequency was 210 h⁻¹ and the relative standard deviation (R.S.D.) was ≤2% for sample solution containing 150 mg l⁻¹ methyldopa (n = 11). The analytical results obtained in commercial formulations by applying the proposed FIA method were in good agreement with labeled values and those obtained by the Brazilian Pharmacopoeia procedure at 95% confidence level.     

Simultaneous spectrophotometric determination of Fe(III), Al(III) and Cu(II) by partial least-squares calibration method

A spectrophotometric method for simultaneous determination of Fe(III), Al(III) and Cu(II) using Alizarin Red S as a chelating agent was developed. The parameters controlling behavior of the system were investigated and optimum conditions were selected. A partial least-squares multivariate calibration method was used for the analysis of ternary mixtures of Fe(III), Al(III) and Cu(II) over the range of 450-6000, 140-4000 and 450-15000 ng ml(-1), respectively. Absorbance data were taken between 400 and 800 nm. Applying this method to simultaneous determination of these metal ions in several synthetic alloy solutions with total relative standard error of less than 5% validated the proposed method.     

Flow injection spectrophotometric method for chloride determination in natural waters using Hg(SCN)(2) immobilized in epoxy resin

A flow injection (FI) spectrophotometric method was proposed for the determination of chloride ion in natural waters. The determination of chloride was carried out by reaction with Hg(SCN)₂ immobilized in an epoxy resin bead in a solid-phase reactor (SPR) and the thiocyanate ions released were determined spectrophotometrically at 480 nm after complexing reaction with Fe(III). The analytical curve for chloride was linear in the concentration range from 5.6 × 10⁻⁵ to 2.2 × 10⁻⁴ mol l⁻¹ with a detection limit of 1.4 × 10⁻⁵ mol l⁻¹. The relative standard deviation (R.S.D.) was 2.2% for a solution containing 2.2 × 10⁻⁴ mol l⁻¹ (n = 10). The simple manifold allows a routine analytical frequency of 100 determinations per hour. The main advantage of the developed method is the 400% reduction of the Hg waste solution generated when compared to conventional methods for chloride determination based on the same spectrophotometric reaction.     

H-point standard addition method for simultaneous determination of phenylephrine hydrochloride,chlorpheniramine maleate,and paracetamol as a ternary mixture in pharmaceutical formulations

The simultaneous analysis of a ternary mixture containing paracetamol (PAR), phenylephrine hydrochloride (PHE), and chlorpheniramine maleate (CPM) was conducted without prior separation and using an advanced spectrophotometric method. The H-point standard addition and absorbance correction methods were selected to determine the compounds, which are highly overlapped spectra in pharmaceutical formulations. The method is based on the use of three different wavelengths of 296, 272, and 227 nm for the ternary mixture. The concentration of PAR was calculated directly at 296 nm because no interferences existed. Absorbance correction method was used to remove the role of PAR at 272 and 227 nm. The concentrations of the PHE and CPM compounds in the mixture were determined by using the H-point standard addition method. The results showed that simultaneous determination of PAR, PHE, and CPM could be conducted within the range of 1–33 μg/mL, 1–23 μg/mL, and 1–36 μg/mL, respectively. The relative standard deviations for the simultaneous determination of PHE, CPM, and PAR were 0.617, 2.76, and 1.71, respectively. The proposed method was implemented successfully for the simultaneous determination of PAR, PHE, and CPM in pharmaceutical formulations.     

Determination of hydrogen peroxide by using a flow injection system with immobilized peroxidase and long pathlength capillary spectrophotometry

The development of a highly sensitive method for the determination of nanomolar concentrations of hydrogen peroxide in the liquid phase is described. This paper demonstrates for the first time a flow injection analysis (FIA) system with immobilized enzyme reactor combined with a total internal reflective cell (a liquid waveguide capillary cell (LWCC)) and spectrophotometric detection, for the development of an improved procedure for the determination of hydrogen peroxide. Moreover, the newly synthesized 4-aminopyrazolone derivative, 4-amino-5-(p-aminophenyl)-1-methyl-2-phenyl-pyrazol-3-one (DAP), is used as a color coupler in its oxidative condensation with the sodium salt of N-ethyl-N-sulphopropylaniline sodium salt (ALPS) which acts as a hydrogen donor. Immobilization of peroxidase is achieved by coupling the periodate-treated enzyme to aminopropyl controlled-pore glass (CPG) beads. The determination of hydrogen peroxide is carried out in a 0.1 M phosphate buffer and the product is monitored at 590 nm with a charge-coupled device (CCD) detector equipped with fiber optics in a fully computerized system. The interference of different species, mainly ionic, was investigated.The method permits detection down to 4 nmol l⁻¹ hydrogen peroxide (signal-to-noise ratio=3). A linear calibration graph was obtained over the range 20-700 nmol l⁻¹. The relative standard deviation (R.S.D.) at 300 nmol l⁻¹ H₂O₂ is 1.7% (n=7). The method was successfully applied for the determination of hydrogen peroxide in samples from a vat-cleaning process.     

Sequential injection spectrophotometric determination of ritodrine hydrochloride using 4-aminoantipyrine

A sequential injection spectrophotometric determination of ritodrine hydrochloride is described. The method is based on the condensation of aminoantipyrine with phenols in the presence of an alkaline oxidizing agent to yield a pink coloured product the absorbance of which is monitored at 503 nm. Different sequential injection analysis (SIA) parameters including reagent concentrations have been optimised and used to obtain the analytical figures of merit. A linear concentration range of 3.1-123.5 μmol L⁻¹ and a detection limit (as 3σ-value) of 1.0 μmol L⁻¹ were obtained. The precision was 2.4 and 2.3% relative standard deviation (R.S.D.) at 6.2 and 15.4 μmol L⁻¹, respectively. This method is superior over previously reported ones in terms of linear range, short analysis time, high sample throughput, excellent reagent economy and minimum waste generation.     

Simultaneous determination of aliphatic and aromatic amines in indoor and outdoor air samples by gas chromatography-mass spectrometry

A gas chromatography-mass spectrometry (GC-MS) method has been proposed for the simultaneous determination of aliphatic and aromatic amines in indoor and outdoor air samples. The method includes pre-concentration of the compounds by percolating the air samples through the acidic solution, ion-pair extraction with bis-2-ethylhexylphosphate (BEHPA), derivatisation of compounds with isobutyl chloroformate (IBCF) and their GC-MS analysis. Aliphatic and aromatic amines were isolated from aqueous samples using BEHPA as ion-pair reagent and derivatised with IBCF for their chromatographic analysis. Aliphatic and aromatic amines were then analysed with GC-MS in both electron impact (EI) and positive and negative ion chemical ionisation (PNICI) mode as their isobutyloxycarbonyl (isoBOC) derivatives. The obtained recoveries ranged from 75.6 to 96.8% and the precision of this method, as indicated by the relative standard deviations (R.S.D.) was within the range of 1.0-4.4%. The detection limits obtained from calculations by using GC-MS results based on S/N: 3 were within the range of 0.08-0.01 ng/m³.     

Simultaneous Spectrophotometric Determination of Levodopa and Benserazide in a Pharmaceutical

ABSTRACT

A method based on a partial least-squares calibration (PLS) for the simultaneous spectrophotometric determination of levodopa (I) and benserazide (II) in a commercially available pharmaceutical preparation is proposed. The calibration procedure was developped by using laboratory made mixtures of I and II, and optimized by selecting the most suitable wavelength range and spectral mode. The relative standard error of prediction (RSEP %) was 0.5% and 0.9% with a limiting reproducibility (R) of 4 10^?6 M and 1.5 10^?6 M for levodopa and benserazide, respectively The proposed method is straightforward, expeditious and precise. Its results are consistent with those provided by HPLC for the two analytes.     

Flow injection spectrophotometric determination of europium using chlortetracycline

A flow injection (FI) spectrophotometric determination of europium (III) is described, based on the complexation between europium (III), and chlortetracycline (CTC) in a Tris-buffer pH 8.0 medium. The resulting yellow-coloured complex is measured at its absorption maximum of 400 nm after 100 μl of sample or standard solution containing europium (III) are injected into the merged streams of CTC and Tris-buffer solutions. Optimum conditions for determining μg amounts of europium (III) are achieved by univariate method. Various types of reactors are also investigated. It is shown that the use of a single bead string reactor gives rise to the enhancement of peak height. A linear calibration curve over the range of 0.10-0.60 μg ml⁻¹ europium (III) is established with the regression equation (n=6) Y=34.93X+0.01 and the correlation coefficient of 0.9994 is obtained. A detection limit (3σ) of 0.01 μg ml⁻¹ of europium (III) and the relative standard deviation (R.S.D.) of 4.32% for determining 1.0 μg ml⁻¹ of europium (III) (n=7) are obtained. The recommended method has been applied to the quantitation of europium (III) in spiked water and stream sediment samples with average recoveries of 99.9 and 97.5%, respectively. The sampling rate is found to be 85 h⁻¹.     

Catalytic spectrophotometric determination of trace amount of cerium(IV)

Based on a property that in dilute hydrochloric acid hydrogen peroxide oxidizes Ponceau S to fade and cerium(IV) has a catalytic effect on the reaction, a new spectrophotometric method was developed for the determination of trace cerium(IV). At 450 nm, the cerium(IV) concentration presents a good linear relationship over the range of 0.08?4 μg/mL with the fading degree ΔA. Its linear regression equation is ΔA = 0.0475c (μg/mL) + 0.0007, with a correlation coefficient of 0.9991. The detection limit of method is 0.05 μg/mL. The method has been successfully applied to the determination of cerium in water and molecular sieve samples with good results. The relative standard deviations of eleven determinations were 0.97?1.11 and 0.19?1.01%, respectively. The recoveries of standard additions were 99.4?99.9 and 99.2?101.0%, respectively. The reliability of this method was certified by parallel determination against the dibromo-p-chlorochlorophosphonazo spectrophotometry.     

Determination of dye precursors in hair coloring products by liquid chromatography with electrochemical detection

The simultaneous determination of seven aminophenols, resorcinol and p-phenylenediamine in hair coloring products was performed by liquid chromatography (HPLC) with amperometric detection (ED). The aminophenols were separated on a ODS C18 reversed-phase column by isocratic elution with a mobile phase based on 0.1 M acetate buffer pH 4.5-methanol (90:10%, v/v) at a flow rate 0.8 mL min⁻¹. The limit of detection (S/N = 3) for the aminophenols was in the 15-40 pg (injected mass) range at an applied potential of 0.950 V versus Ag/AgCl. Peak heights for the aminophenols and the two others compounds were found to be linearly related to the amount injected, from 0.3 to 300 ng (r > 0.994-0.999).The relative standard deviation (R.S.D., n = 10) for 1 ng injected was comprised in the range from 2.5 to 6.2%, depending on the aminophenol tested. The present method minimizes troublesome and time-consuming pretreatment procedures and it was applied to the determination of aminophenols, resorcinol and phenylenediamine in hair coloring formulations.     

Simultaneous spectrophotometric determination of hydrazine and phenylhydrazine based on their condensation reactions with different aromatic aldehydes in micellar media using H-point standard addition method

H-point standard addition method (HPSAM) was applied to the simultaneous determination of hydrazine and phenylhydrazine. The method is based on the hydrazone formation reactions of hydrazine and phenylhydrazine in the presence of micellar sodium dodecyl sulfate (SDS). Mixed reagents of p-(dimethylamino)benzaldehyde (DAB) and p-nitrobenzaldehyde (NB) was used as selective chromogenic reagents for hydrazine and phenylhydrazine. Hydrazine and phenylhydrazine can be determined simultaneously in the range 0.020-0.50 and 0.20-10.0 μg ml⁻¹, respectively. The results allowed that simultaneous determination could be performed with the ratio 1:500 to 1:10 hydrazine-phenylhydrazine. Under working conditions, the proposed method was successfully applied to the simultaneous determination of hydrazine and phenylhydrazine in several synthetic mixtures and plasma and water samples.     

Application of continuous wavelet transformation to the simultaneous kinetic determination of binary mixtures

Wavelet transformation of kinetic profiles as a new and simple method was developed for the simultaneous determination of binary mixtures without prior separation steps. The mathematical explanation of the procedure is illustrated. Daubechies (db), symlet (sym) and discrete meyer wavelet (meyr) from the family of wavelet transforms were selected and applied under the optimal conditions for the resolution of binary mixtures. A model data as well as experimental data were tested. The results from the experimental data relating to the simultaneous spectrophotometric determination of phosphate and silicate based on the formation of phospho- and silico-molybdenum blue complexes in the presence of ascorbic acid, and also simultaneous determination of Co²⁺ and Ni²⁺ based on their complexation reactions with 1-(2-pyridylazo)-2-naphthol (PAN) in micellar media at pH 6.0 were presented as real models. The proposed method was validated by simultaneous determination of phosphate and silicate in detergent and tap water and also Co²⁺ and Ni²⁺ in tap water samples.