Simultaneous determination of antazoline and naphazoline by the net analyte signal standard addition method and spectrophotometric technique

A novel net analyte signal standard addition method (NASSAM) was used for simultaneous determination of the drugs anthazoline and naphazoline. The NASSAM can be applied for determination of analytes in the presence of known interferents. The proposed method is used to eliminate the calibration and prediction steps of multivariate calibration methods; the determination is carried out in a single step for each analyte. The accuracy of the predictions against the H-point standard addition method is independent of the shape of the analyte and interferent spectra. The net analyte signal concept was also used to calculate multivariate analytical figures of merit, such as LOD, selectivity, and sensitivity. The method was successfully applied to the simultaneous determination of anthazoline and naphazoline in a commercial eye drop sample.     

Determination of creatine kinase activity using a co-immobilized auxiliary enzyme reactor coupled on-line with a flow injection system

Two flow injection methods (based on spectrophotometric and spectrofluorimetric detection) were developed for the determination of over-all creatine kinase activity. Despite the complexity of the reactions involved (both include three enzyme-catalysed steps), the manifold is very simple because the two auxiliary enzymes which catalyse the two-step indicator reaction are co-immobilized on controlled-pore glass. The features of the proposed methods (calibration ranges between 0.1 and 2.0 and 0.01 and 1.0 U l-1, relative standard deviation 0.93 and 0.53% for the spectrophotometric and spectrofluorimetric methods, respectively) allow the successful determination of the analyte activity in serum samples (recoveries better than 95-105% for both methods).     

New spectrophotometric and spectrofluorimetric methods for the determination of angiotensin II receptor antagonists in tablets and plasma

Spectrophotometric and spectrofluorimetric methods for the determination of five Angiotensin II type 1 receptor antagonists in tablets and plasma have been developed and optimized. The spectrophotometric method involves the addition of a measured excess of bromate-bromide in HCl medium and subsequent estimation of the residual bromine by reacting with a fixed amount of methyl orange. The spectrofluorimetric method depends on the oxidation of the drugs with cerium(IV) and subsequent monitoring of the fluorescence of the induced cerium(III) at 365 nm with excitation at 255 nm. Both of the proposed methods were successfully applied to the determination of the investigated drugs in their pure forms and pharmaceutical preparations. Besides, the spectrofluorimetric method was applied to the determination of irbesartan and telmisartan in biological fluids with good accuracy and precision.     

Application of Net Analyte Signal Standard Addition Method (NASSAM) for Simultaneous Determination of Lead and Tin by Differential Pulse Polarography

Differential pulse polarography was used for simultaneous determination of Sn²⁺ and Pb²⁺. But there is a problem for simultaneous determination and it is high overlapped DPPs of mentioned cations that their determination is impossible in the presence of each other, so multivariate calibration methods as chemomatrics methods were used for this determination. There are some disadvantageous for multivariate calibration methods that can be solved by a new and simple method called net analyte signal standard addition method. This method has some advantages, such as: the use of a full voltammogram, realization in a single step, therefore it does not require calibration and prediction steps and only a few measurements are required for the determination.     

New methodology for checking of absence of the systematic errors in the determination of sulphate ion in MgCl2·6H2O

A new methodology is proposed for obtaining analytical results free from bias errors, it is based on a modification of the standard addition method. Bias or systematic errors are taken as the differences between the amounts of analyte in the test portion and the image of the analytical signal on a calibration relationship where the amounts of added analyte act as the predictors. The constant component of the error, the matrix interactive effect and the direct matrix interference are jointly discussed as the main sources of bias. The latter two are considered to be different forms of interference. As an example, the new methodology was applied to the determination of sulphate ion in a magnesium chloride sample (Merck AR) using a spectrophotometric and an atomic absorption spectrophotometric procedure. No direct matrix interference or interactive matrix effect on the analytical results was found.     

Spectrophotometric simultaneous determination of cobalt, copper and nickel using nitroso-R-salt in alloys by partial least squares

Partial least squares modeling as a powerful multivariate statistical tool applied to spectrophotometric simultaneous determination of cobalt, copper, and nickel in aqueous solutions. The concentration range for cobalt, copper and nickel were 0.4-2.6, 0.6-3.4, 0.5-5.5 ppm, respectively. The experimental calibration set was composed with 36 sample solutions using a mixture design for three component mixtures. The absorption spectra were recorded from 470 to 600 nm. The effect of pH on the sensitivity and selectivity was studied according to net analyte signal (NAS). The values of root mean square difference (RMSD) for cobalt, copper and nickel using partial least squares (PLS) were 0.0192, 0.0263 and 0.0446 ppm, respectively. The effects of various cations and anions were investigated. The method was used to determination of cobalt, copper and nickel in two sample alloys based on copper, nickel and cobalt (known as cunico) and based on cobalt, nickel and iron (known as conife).     

Spectrophotometric and spectrofluorimetric methods for the determination of pregabalin in bulk and pharmaceutical preparation

Two new, sensitive and selective spectrofluorimetric and spectrophotometric methods have been developed for the determination of the gamma-amino-n-butyric acid derivative pregabalin (PGB) in bulk drug and capsule. Pregabalin, as a primary amine compound, reacts with 7-chloro-4-nitrobenzofurazon (NBD-Cl) which is a highly sensitive fluorogenic and chromogenic reagent used in many investigations. According to this fact, spectrophotometric and spectrofluorimetric methods for the determination of pregabalin in capsules were developed for the first time. The relation between the absorbance at 460 nm and the concentration is rectilinear over the range 0.5-7.0 microg mL(-1). The reaction product was also measured spectrofluorimetrically at 558 nm after excitation at 460 nm. The fluorescence intensity was directly proportional to the concentration over the range 40-400 ng mL(-1). The method was applied successfully to the determination of this drug in pharmaceutical dosage form. The mean recovery for the commercial capsules was 99.93% and 99.96% for spectrophotometric and spectrofluorimetric study, respectively. The suggested procedures could be used for the determination of PGB in pure and capsules being sensitive, simple and selective.     

Use of partial least-squares regression for multicomponent determinations based on kinetic spectrofluorimetric data. Simultaneous determination of canrenone and spironolactone in urine

A new spectrofluorimetric method for the simultaneous determination of canrenone and spironolactone in urine is proposed. The method is based on the different rates at which the two analytes react with hot sulfuric acid to form a trienone. The kinetic spectrofluorimetric data are processed by partial least-squares regression. The effects of sulfuric acid concentration and temperature on the system under study were also evaluated and the optimum values for carring out the reaction were 50% and 50 degrees C, respectively. The method was checked by analyzing urine samples that they contained both diuretics. The accuracy and the precision of the method were tested. The relative standard errors in the quantification of each analyte in all tested samples were 3.69 and 3.59%. The proposed method was validated by comparison with a high performance liquid chromatographic method for urine samples.     

Estimation of Performance Characteristics of an Analytical Method Using the Data Set Of The Calibration Experiment

Abstract

A model to calculate the analytical sensitivity, limit of detection, limit of determination and precision of a method of instrumental analysis through a data set obtained by calibration experiment using the statistical analysis of linear regression, is proposed. This model has been applied to spectrophotometric, spectrofluorimetric and chromatographic methods. The values obtained are independent of the instrument used and can be applied as a criterion of comparison between different methods proposed for the same analyte. Also, these characteristics have been calculated using the IUPAC suggested model and both results have been compared.     

Simultaneous Spectrophotometric Determination of Sunset Yellow and Quinoline Yellow in a Single Step

In this work a new modified standard addition method for simultaneous spectrophotometric determination of Sunset yellow (SY) and Quinoline yellow (QY) is used. The generalized Net Analyte Signal Standard Addition Method (GNASSAM) was introduced for simultaneous standard addition of analytes. By applying this method the concentrations of analytes are determined in a single step. The applicability of new method was used for the simultaneous determination of strongly overlapped spectra of SY and QY in a real sample without using any separation step. GNASSAM was also used to calculate figures of merit. Moreover, good limits of detection (SY=0.13 and QY=0.16 mg L ^?1) and suitable selectivity and sensitivity were determined. HPLC method was applied for finding subspace in binary mixtures of real samples. The results of investigated method for real sample were compared with HPLC results. The obtained results were in a good agreement with those of HPLC method.     

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.     

Simultaneous kinetic-spectrophotometric determination of hydrazine and acetylhydrazine in micellar media using the H-point standard addition method.

The H-point standard addition method (HPSAM), based on a spectrophotometric measurement for the simultaneous determination of hydrazine and acetylhydrazine, is described. This method is based on the difference between the rates of their reactions with N,N-dimethylaminobenzaldehyde (DAB) in the presence of sodium dodecyl sulfate (SDS) in acidic media. The results showed that hydrazine and acetylhydrazine could be determined simultaneously in the range of 0.020 - 0.70 and 0.20 - 5.0 mg L(-1), respectively. Under the working conditions, the proposed method was successfully applied to the simultaneous determination of hydrazine and acetylhydrazine in several synthetic mixtures and plasma and water samples.     

Spectrophotometric and spectrofluorimetric methods for analysis of tramadol, acebutolol and dothiepin in pharmaceutical preparations

Sensitive spectrophotometric and spectrofluorimetric methods are described for the determination of tramadol, acebutolol and dothiepin (dosulepin) hydrochlorides. The two methods are based on the condensation of the cited drugs with the mixed anhydrides of malonic and acetic acids at 60 degrees C for 25-40 min. The coloured condensation products are suitable for the spectrophotometric and spectrofluorimetric determination at 329-333 and 431-434 nm (excitation at 389 nm), respectively. For the spectrophotometric method, Beer's law was obeyed from 0.5 to 2.5 microg ml(-1) for tramadol, dothiepin and 5-25 microg ml(-1) for acebutolol. Using the spectrofluorimetric method linearity ranged from 0.25 to 1.25 microg ml(-1) for tramadol, dothiepin and 1-5 microg ml(-1) for acebutolol. Mean percentage recoveries for the spectrophotometric method were 99.68+/-1.00, 99.95+/-1.11 and 99.72+/-1.01 for tramadol, acebutolol and dothiepin, respectively and for the spectrofluorimetric method, recoveries were 99.5+/-0.844, 100.32+/-0.969 and 99.82+/-1.15 for the three drugs, respectively. The optimum experimental parameters for the reaction has been studied. The validity of the described procedures was assessed. Statistical analysis of the results has been carried out revealing high accuracy and good precision. The proposed methods were successfully applied for the determination of the selected drugs in their pharmaceutical preparations with good recoveries. The procedures were accurate, simple and suitable for quality control application.     

Determination of trace amounts of cobalt by solvent extraction--second derivative spectrophotometry

A sensitive derivative spectrophotometric method is described for the determination of microamounts of cobalt based on the integration of liquid-liquid separation and reaction, in dichloroethane, of the analyte with 3-(4-phenyl-2-pyridinyl)-5-phenyl-1,2,4-triazine (PPT) and 2,4,6-trinitro-phenol (picric acid). Cobalt was thus determined in the range 7.2-500 ng/ml. The method has a high selectivity with a detection limit of 2.2 ng/ml. The relative standard deviations were 3.2 and 1.5% for 20 and 100 ng/ml cobalt, respectively. The proposed method was applied to the determination of the analyte in vitamins.     

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.     

Simultaneous kinetic-spectrophotometric determination of periodate-bromate and iodate-bromate mixtures using the H-point standard addition method

The H-point standard addition method (HPSAM), based on spectrophotometric measurement, for simultaneous determination of periodate-bromate and iodate-bromate mixtures is described. This method is based on the difference between the rates of their reactions with iodide in acidic media. The results showed that simultaneous determinations could be performed with the ratio 1:15-12:1 for periodate-bromate and 15:1-1:15 for iodate-bromate. The proposed method was successfully applied to the simultaneous determination of periodate-bromate and iodate-bromate in water and synthetic samples.     

Spectrophotometric and spectrofluorimetric methods for analysis of acyclovir and acebutolol hydrochloride

Simple and sensitive spectrophotometric and spectrofluorimetric methods are described for analysis of acyclovir and acebutolol hydrochloride. The proposed methods are based on oxidation of the selected drugs with cerium(IV) ion in acidic medium with subsequent measurement of either the decrease in absorbance at 320nm or the fluorescence intensity of the produced cerous(III) ion at 361-363nm (excitation at 250nm). Beer's law obeyed from 2 to 8, 0.25 to 2.5microgcm-1 acyclovir, 1 to 7 and 0.25 to 2.5microgml-1 acebutolol hydrochloride, using the spectrophotometric and spectrofluorimetric method, respectively. The proposed method were successfully applied for determination of the selected drugs in their pharmaceutical preparations with good recoveries.     

H-point standard addition method for simultaneous determination of Fe(II), Co(II) and Cu(II) in micellar media with simultaneous addition of three analytes

H-point standard addition method, HPSAM, with simultaneous addition of three analytes is proposed for the resolution of ternary mixtures. It is a modification of the previously described H-point standard addition method that permits the resolution of three species from a unique calibration set by making the simultaneous addition of the three analytes. The method calculates the analyte concentration from spectral data at two wavelengths where the two species selected as interferents present the same absorbance relationship. These wavelength pairs are easily found, and can be selected to give the most precise results. Diethyldithiocarbomate (DDC) in a cationic micellar solution of cetyltrimethylammonium bromide (CTAB) was used for determination of Fe(II), Co(II) and Cu(II) at pH 5.50. The results showed that simultaneous determination of Fe(II), Co(II) and Cu(II) could be preformed in the range of 0.0–6.0, 0.0–8.0 and 0.0–12.0 μg ml⁻¹, respectively. The proposed method was successfully applied to the simultaneous determination of Fe(II), Co(II) and Cu(II) in several synthetic mixtures containing different concentration of Fe(II), Co(II) and Cu(II).     

Contributions to accuracy improvement of simultaneous ICP atomic emission spectrometry using multi-line measurements of analyte and internal standard elements Applications for the analysis of permalloy

For successful application of simultaneous ICP atomic emission spectrometry for major component determinations in multi-component materials the accuracy of the method has to be improved. As a contribution to solve this problem a combined procedure for multi-component standard sample preparation, optimum calibration and different variations of internal standard corrections is described. Variance-weighted multi-line calibrations give most accurate results. Internal standard corrections are effective, if the time-dependent spectral line intensity fluctuations of the standard and the analyte elements are well correlated. Their sensitivities against some responsible device parameter variations are investigated. On the basis of multi-line measurements of the analyte and internal standard elements a “group-selected internal standard correction” (GS-ISC) method is applied and results in relative errors of less than 1% even for extreme fluctuations of the raw intensities. For rapid routine determination methods of materials with variable element compositions the added line intensities of the internal standard element can be used to correct the added analyte line raw intensities (“intensity addition internal standard correction” (IA-ISC) method). These accuracy optimization procedures are applied for the analysis of the soft magnetic material permalloy using the internal standard element In.