Second-order Derivative Spectrophotometry Research Articles

Derivative spectrophotometry allows quantitative determination of essential oils in dispersible powders of spray-dried nanocapsules

This study aimed to develop and validate an analytical methodology based on derivative spectrophotometry to determine the true concentration of ginger (ZEO) and rosemary (REO) essential oils in nanocapsule redispersible powder formulations. Second-order derivative spectrophotometry made it possible to nullify the interference of nanocapsule components at 240 and 245 nm wavelengths for ZEO and REO, respectively. The validated method was linear in the range 0.01-0.04 mg mL−1 for ZEO and 0.6-0.96 mg mL−1 for REO. It is also accurate with RSD of 1.82 and 1.44 for ZEO and REO respectively, and shows recovery rates close to 100% in both essential oils when assessing accuracy. The methodology used allowed the determination of the essential oils in the presence of the formulation components, simply and quickly, showing to be an option to be used for quantification of OEs in these nanometric systems.

Method Transfer Evaluation for Digital Derivative Spectrophotometry Through its Resolution Parameter Comparison of Different Computer Programs.

The application assessment of different programs was performed with equivalence tests for method transfer pro second-order derivative spectrophotometry. The digital second-order derivative spectra were calculated on different instruments; GBC Scientific Equipment Cintra 20 (Cintral v.2.6 and Spectral v.1.70 software programs) and Thermo Scientific Evolution 300 (VISIONPro software) were analyzed using the amplitude A/B ratio (A = 2D265,263; B = 2D263,261). Amplitude A/B ratio is the resolution parameter for derivative spectrophotometry prescribed in European Pharmacopoeia. The obtained values for A/B ratio were either very similar or significantly different among programs: 0.669 (Cintral v.2.6), 0.549 (Spectral v.1.70), 0.556 (medium indirect VISIONPro), 0.557 (one-step Savitzky-Golay 7 VISIONPro), 0.689 (two-step Savitzky-Golay 7 VISIONPro). Method transfer was possible between Spectral v.1.70 and VISIONPro (medium indirect and one-step Savitzky-Golay 7), but the values obtained in Cintral v.2.6 were not comparable to the other programs. The absorbance data exported from both instruments were additionally calculated in OriginPro8 which provided almost the same mean A/B values (0.627 Cintral v.2.6; 0.624 VISIONPro), confirming that the two instruments recorded the same zero-order spectra. The calculation of resolution parameter could be used for verification of program comparison, which would enable transfer between sender and receiver laboratory. The accordance between program algorithms was confirmed when acceptable differences for values of resolution parameter (A/B ratios) were achieved.

Temperature dependence of the optical absorption spectra of InP/ZnS quantum dots

The optical-absorption spectra of InP/ZnS (core/shell) quantum dots have been studied in a broad temperature range of T = 6.5–296 K. Using the second-order derivative spectrophotometry technique, the energies of optical transitions at room temperature were found to be E 1 = 2.60 ± 0.02 eV (for the first peak of excitonic absorption in the InP core) and E 2 = 4.70 ± 0.02 eV (for processes in the ZnS shell). The experimental curve of E 1(T) has been approximated for the first time in the framework of a linear model and in terms of the Fan’s formula. It is established that the temperature dependence of E 1 is determined by the interaction of excitons and longitudinal acoustic phonons with hω = 15 meV.

Temperature-induced shift of the exciton absorption band in InP/ZnS quantum dots

Using the second-order derivative spectrophotometry method, we have determined the energy of optical transitions of colloidal InP/ZnS core-shell quantum dots at room temperature: E1 = 2.60 eV corresponds to a first exciton absorption peak of the InP core, E2 = 4.70 eV appears to meet the processes in the ZnS shell. We have investigated E1(T) temperature dependence within 6.5 – 296 K range for the first time. The obtained experimental data have been approximated by means of a linear model and Fan’s expression. Also, it has been shown that the interaction between excitons and longitudinal acoustic phonons causes the energy E1 to change with temperature. In this case, the peak’s FWHM remains invariant and amounts to 0.39 eV, which indicates the inhomogeneous broadening character and a high degree of static disorder in the ensemble of the quantum dots studied.

High-performance liquid chromatography and derivative spectrophotometry for simultaneous determination of pravastatin and fenofibrate in the dosage form

High performance liquid chromatography (HPLC) and second-order derivative spectrophotometry have been used for simultaneous determination of pravastatin (PS) and fenofibrate (FF) in pharmaceutical formulations. HPLC separation was performed on a phenyl HYPERSIL C18 column (125 mm × 4.6 mm i.d., 5 μm particle diameter) in the isocratic mode using a mobile phase acetonitrile/0.1 % diethyl amine (50:50, V/V, pH 4.5) pumped at a flow rate of 1.0 mL min-1. Measurement was made at 240 nm. Both drugs were well resolved on the stationary phase, with retention times of 2.15 and 5.79 min for PS and FF, respectively. Calibration curves were linear (R = 0.999 for PS and 0.996 for FF) in the concentration range of 5-50 and 20-200 µg mL-1 for PS and FF, respectively. Pravastatin and fenofibrate were quantitated in combined preparations also using the second-order derivative response at 237.6 and 295.1 nm for PS and FF, respectively. Calibration curves were linear, with the correlation coefficient R = 0.999 for pravastatin and fenofibrate, in the concentration range of 5-20 and 3-20 µg mL-1 for PS and FF, respectively. Both methods were fully validated and compared, the results confirmed that they were highly suitable for their intended purpose.

Competitive adsorption of methylene blue and brilliant green onto graphite oxide nano particle following: Derivative spectrophotometric and principal component-artificial neural network model methods for their simultaneous determination

In this work, the competitive adsorption of methylene blue (MB) and brilliant green (BG) onto graphite oxide (GO) nanoparticles followed by their accurate and reproducible determination by second order derivative spectrophotometry (SODS) and principal component–artificial neural network model (PCA–ANN) model has been studied. The evaluation of kinetic and isotherm studies was investigated at optimum experimental conditions set as pH=7.0, 8mg of GO and 14min contact time in binary systems. The equilibrium amounts of MB and BG dyes in binary mixture adsorbed onto GO-NP has opposite correlation with their initial concentration. Principal component analysis (PCA) used to minimize the dimensionality of large data sets via reducing the number of spectral data by a three-layered feed-forward artificial neural network (ANN) trained by Levenberg–Marquardt back-propagation algorithm. The ANN model was able to predict the concentrations of both dyes in mixtures with a tangent sigmoid transfer function (tansig) at hidden layer with 20 neurons and a linear transfer function (purelin) at output layer. Several isotherm models were applied to experimental data and the isotherm constants were calculated for BG and MB dyes. Among the applied models, the extended Freundlich isotherm model adequately predicts the multi-component adsorption equilibrium data at moderate ranges of concentration.

SIMULTANEOUS DETERMINATION OF PIPERACILLIN AND TAZOBACTAM IN THE PHARMACEUTICAL FORMULATION TAZONAM® BY DERIVATIVE SPECTROPHOTOMETRY

ABSTRACT In this paper, a simple and rapid method was developed for the simultaneous determination of Piperacillin (PIP) and Tazobactam (TAZ) by second-order derivative spectrophotometry. Water was selected as a solvent for extraction and determination of both analytes. Further studies of photo-stability and forced degradation for both drugs were also performed. The spectral variables were optimized, a smoothing factor of 8•10 3 and a scaling factor of 1•10 4 were selected and the analytical signals were evaluated at 296.3 nm and 233.3 nm for PIP and TAZ, respectively.The detection and quantification limits for PIP and TAZ were: 3.2•10 -7 to 9.5•10 and 2.7•10 -7 to 8.9•10 -7 mol/L, respectively. The levels of repeatability (RSD) were 1.5% and 2.4% for PIP and TAZ respectively.The method was applied to the pharmaceutical formulation TAZONAM NF® Wyeth. USA, with a nominal content of 4.0 g of PIP, 0.5 g of TAZ, 0.139 g of citric acid and 1 mg of EDTA. A study of excipients was carried out and it was found that they do not interfere with quantification. By applying this method, a content of 3.96 ± 0.04 g and 0.57 ± 0.01 g was found of PIP and TAZ, respectively.

A Rapid, Simple, and Sensitive Spectrophotometric Determination of Traces of Vanadium (V) in Foodstuffs, Alloy Steels, and Pharmaceutical, Water, Soil, and Urine Samples

A rapid, simple, sensitive, and selective spectrophotometric method is investigated for the determination of traces of vanadium (V) in foodstuffs, alloy steels, and pharmaceutical, water, soil, and urine samples in aqueous DMF medium. The metal ion forms a green colored complex with 2-hydroxy-3-methoxy benzaldehyde thiosemicarbazone (HMBATSC) in an acidic buffer of pH 6.0. The green colored solution, having an absorbance maximum at 380 nm, is stable for more than 72 hours. Beer's law is obeyed in the range of 0.051–2.037 µg ml−1. The molar absorptivity and Sandell's sensitivity of the method are found as 2.75 × 104 l mol−1 cm−1 and 0.0018 µg cm−2, respectively. The green colored complex has 1:2 [V(V)-HMBATSC] stoichiometry. The stability constant of the complex is determined as 3.267 × 1011 by Job's method. The optimum reaction conditions and other analytical parameters are studied. A sensitive and selective second-order derivative spectrophotometry has also been proposed for the determination of V(V). The interference of various cations and anions are studied. The present method is successfully applied to the determination of vanadium (V) in foodstuffs, alloy steels, and pharmaceutical, water, soil, and urine samples.

Simultaneous determination of montelukast and loratadine by HPLC and derivative spectrophotometric methods

In this study, high performance liquid chromatography (HPLC) and second derivative spectrophotometry have been used and described for the simultaneous determination of montelukast and loratadine in pharmaceutical formulations. HPLC separation was achieved with a Symmetry C18 column and sodium phosphate buffer (pH adjusted to 3.7): acetonitrile (20:80, v/v) as eluent, at a flow rate of 1.0 ml/min. UV detection was performed at 225 nm. The LC method is simple, rapid, selective and stability indicating for the determination of montelukast. 5-Methyl 2-nitrophenol was used as internal standard for the purpose of quantification of both the drugs in HPLC. In the second-order derivative spectrophotometry, for the determination of loratadine the zero-crossing technique was applied at 276.1 nm, but for montelukast peak amplitude at 359.7 nm (tangent method) was used. Both methods were fully validated and a comparison was made for assay determination of selected drugs in formulations. The results confirm that the methods are highly suitable for its intended purpose.

Spectra interference between diquat and paraquat by second derivative spectrophotometry

A rapid and accurate method, combining solid-phase extraction and second-order derivative spectrophotomety approaches, is developed for the simultaneous determination of diquat (DQ) and paraquat (PQ) in blood, tissue and urine samples. Supernatant resulting from the precipitation of protein (with trichloroacetic acid) in plasma and tissue or Amberlite IRA-401 resin treated urine are passed through a mini-column packed with Wakogel gel (Silica gel). Analytes are then eluted with a non-organic solvent, 0.2 mol/l HCl solution containing 2 mol/l NH 4Cl. UV spectrum of the eluent in 220–350 nm range provides effective screen to detect the presence of DQ and/or PQ. In the presence of DQ or PQ alone, the analyte present is quantitated by conventional zero- or second-order derivative spectrophotometry. The calibration curve in the 0.1–5.0 mg/l range for either analyte obeys Beer’s law. When both DQ and PQ are present, their concentrations are determined by the peak amplitudes of their respective second-derivative spectra after the addition of alkaline dithionite reagent. Interference is negligible when the DQ/PQ concentration ratio is within the 5.0–0.2 range. Using a 2-ml of sample size, the detection limits for DQ and PQ in plasma are 0.02 and 0.005 mg/l. The corresponding detection limits for urine samples (10 ml sample size) are 0.004 and 0.001 mg/l. Recoveries of DQ and PQ in triplicate plasma and urine samples spiked with 0.5 mg/l of analytes are 93 and 85%. The precision of the proposed method resulting from triplicate study of spiked urine samples varies from 3.2 to 4.6% at 0.5 mg/l of DQ and PQ, respectively.

A Plackett-Burnam screening design directs the efficient formulation of multicomponent DRV liposomes.

A computer-based technique was applied for the optimization of recently described multicomponent protective liposomal formulations. These formulations contain riboflavin in either free form or complexed with gamma-cyclodextrin as a model drug, sensitive to photochemical degradation, as well as various light absorbers and antioxidants incorporated into the lipid bilayer and/or the aqueous phase of liposomes. During the liposomal preparation, a series of 11 factors were isolated as important to affect their effectiveness as stabilization systems. These factors were related, first, to the composition of liposomes and, second, to variations during the preparation procedure. The Plackett--Burnam design described in this study was applied for the isolation of the significant factors in order to concentrate more on them. The stabilization ratio of the vitamin was the response variable of the system to be optimized. In order to assure the presence of the examined components in liposomes, the entrapment values were calculated for all the materials, either spectrophotometrically or using second-order derivative spectrophotometry. The optimum formulation should be characterized from the higher protection of the drug.

Simultaneous determination of benazepril hydrochloride and hydrochlorothiazide in tablets by second-order derivative spectrophotometry

A second-order derivative spectrophotometric method for the simultaneous determination of benazepril hydrochloride and hydrochlorothiazide in pharmaceutical dosage forms is described. The determination of benazepril hydrochloride in the presence of hydrochlorothiazide was achieved by measuring the second-order derivative signals at 253.6 and 282.6 nm, while the second-order derivative signal at 282.6 nm was measured for the determination of hydrochlorothiazide. The linear dynamic ranges were 14.80–33.80 μg ml −1 for benazepril hydrochloride and 18.50–42.20 μg ml −1 for hydrochlorothiazide, the correlation coefficient for the calibration graphs were better than 0.9998, n=5, the precision (%RSD) was better than 1.43% and the accuracy was satisfactory ( E r<0.99%). The detection limits were found to be 2.46 and 1.57 μg ml −1 for benazepril hydrochloride and hydrochlorothiazide, respectively. The method was applied in the quality control of commercial tablets and proved to be suitable for rapid and reliable quality control.

Rapid simultaneous determination of ruthenium and osmium in aqueous solutions of their tetroxides by second-order derivative spectrophotometry

Direct and simple spectrophotometric methods for the simultaneous determination of ruthenium and osmium in aqueous solutions of their tetroxides are described. The methods are based on the calculation of derivative spectra of RuO 4and OsO 4 in water. The second-order derivative values of RuO 4 at 310 nm (the ‘zero-crossing’ point of osmium) and of OsO 4 at 250 nm (the ‘zero-crossing’ point of ruthenium) can be used for the determination of the concentration of ruthenium and osmium, respectively. Beer's law is obeyed up to 32 μg Ru ml −1 and 40 μg Os ml −1 in the examined solutions. Using the developed methods 97.3 μg Ru ml −1 and 95.8 μg Os ml −1 in a plasma standard solution of the noble metals were determined.

2(k-p) fractional factorial design via fold over: application to optimization of novel multicomponent vesicular systems.

A computer-based technique based on a 2(k-p) fractional factorial design was applied for the optimization of recently described multicomponent protective liposomal formulations. These formulations contain riboflavin (vitamin B2) as a model, photosensitive drug, in addition to Oil Red O, deoxybenzone, oxybenzone and beta-carotene as oil-soluble light absorbers and antioxidants incorporated into the lipid bilayer, and sulisobenzone as a water-soluble light absorber incorporated into the aqueous phase of liposomes. The presence or absence of these five different light absorbers in multilamellar liposomes containing the vitamin free or complexed with gamma-cyclodextrin comprised the six factors of the system, each one examined at two levels. The stabilization ratio of the vitamin and its percentage entrapment in liposomes were the two response variables of the system to be optimized. The entrapment values were calculated for all the materials, either spectrophotometrically, using second-order derivative spectrophotometry, or fluorimetrically. The response variables were predicted by multiple regression equations comprising combinations of the six formulation factors. Higher entrapment and higher protection for the drug should characterize the optimum formulation.

Formulation optimization of novel multicomponent photoprotective liposomes by using response surface methodology

A computer optimization technique based on response surface methodology has been applied for the optimization of recently described multicomponent photoprotective liposomal formulations. These formulations contain riboflavin as a model photosensitive drug as well as oil red O as an oil-soluble light absorber incorporated into the lipid bilayer, and sulisobenzone as a water-soluble light absorber incorporated into the aqueous phase of liposomes. The presence of these two different light absorbers and the molar ratio between the liposome components, egg phosphatidylcholine and cholesterol, comprise the three factors of the system; each one has been examined in three levels. The percentage entrapment of the photosensitive riboflavin and its photodegradation rate constant were the two response variables of the system to be optimized. The entrapment values were calculated for all the materials, either spectrofluorimetrically or by using second-order derivative spectrophotometry. The photodegradation rate constant was calculated spectrofluorimetrically. The response variables were predicted by multiple regression equations comprising combinations of the three formulation factors. The regression equations for the two response variables were examined as a simultaneous optimization problem and predicted response values were successfully validated. The optimum formulation should be characterized from both the higher entrapment and the higher photoprotection for the drug.

Determination of Americium in a Nitric Acid Medium Using Second-Order Derivative Spectrophotometry.

A second-order derivative spectrophotometric method has been developed for the determination of microgram quantities of trivalent americium in a nitric acid medium containing plutonium and uranium. The second-order derivative absorbance of the americium at 503.5nm is used for the quantitative analysis. In the determination of 5.8μg/ml and 3.9μg/ml of americium, the presence of a 100-fold amount of plutonium and a 600-fold amount of uranium could be tolerated, respectively. The trivalent americium, in the concentration range of 1-11μg/ml has been determined with good precision. The detection limit was 0.3μg/ml at 3 times the standard deviation (3σ). The relative standard deviation was less than 2.1% for a sample of uranium-plutonium mixed oxide. The proposed method does not require the complicated separation step of plutonium and uranium.

Determination of Ruthenium and Osmium with Tin(II) Chloride by Second-Order Derivative Spectrophotometry

Ruthenium and osmium can be determined in the same solution by second-order derivative spectrophotometry after a conversion into complexes with tin(II) chloride. In a mixed solution containing 5 M (1 M=1 mol dm-3) HCl and 0.05 M SnCl2 ruthenium is quantitatively converted, from various oxidation states and various forms, into the complex RuCl2(SnCl3)22- after heating for 45 min. The value of the second-derivative for the anionic complex with SnCl3 ligands at 22250 cm”1 (zero-crossing point of osmium) is a measure of ruthenium concentration. Osmium can be determined after heating the solution containing 2 M HCl and 0.4 M SnCl2 for 1.5 h. At 25900 cm-1 the value of second-derivative is dependent only on osmium concentration (zero-crossing point of ruthenium). Ruthenium, in the concentration range 2-35 μg/ml (in the presence up to 450 μgOs/ml), and osmium, in the concentration range 7.5 - 90 μg/ml (in the presence up to 45 μgRu/ml), can be determined with good precision and accuracy, without separation.

Determination of amiodarone hydrochloride in pharmaceutical formulations by derivative UV spectrophotometry and high-performance liquid chromatography (HPLC).

Assay procedures based on derivative ultraviolet spectrophotometry and high-performance liquid chromatography (HPLC) have been developed for the specific determination of amiodarone hydrochloride in pharmaceutical dosage forms. The use of first- and second-order derivative spectrophotometry was found to have suppressed the background absorption from the excipients with comparable accuracy and precision to the reversed-phased HPLC reference method. A conventional UV absorption method (lambda = 242 nm) is subject to possible interference by formulation excipients.