Second Derivative Spectrophotometry Research Articles

Inclusion complexes of N-sulfamoyloxazolidinones with β-cyclodextrin

A study of inclusion complexes of six N-sulfamoyloxazolidinone derivatives with β-cyclodextrin is described. The inclusion complexes were prepared in solution and in solid state with stoichiometry host–guest 1:1, and characterized. In solution, the complexation was carried out by spectrophotometric measurements at 25 °C. The stoichiometries and stability constants of complexes at various pHs have been determined using second-derivative spectrophotometry UV–vis. Hydrophobic properties of N-sulfamoyloxazolidinones are improved following their inclusion into β-CD.

Effects of Phosphatidylserine and Phosphatidylethanolamine Content on Partitioning of Triflupromazine and Chlorpromazine between Phosphatidylcholine-Aminophospholipid Bilayer Vesicles and Water Studied by Second-Derivative Spectrophotometry

To assess the affinity of psychotropic phenothiazine drugs, triflupromazine (TFZ) and chlorpromazine (CPZ), for the membranes of central nervous system and the other organs in the body, the partition coefficients (Kps) of these drugs to phosphatidylcholine (PC)-phosphatidylserine (PS) and PC-phosphatidylethanolamine (PE) small and large unilamellar vesicles (SUV, LUV) were examined by a second-derivative spectrophotometric method, since PS is abundantly contained in the membranes of the central nervous system and PE is distributed widely in the membranes of the organs in the body. Size and preparation methods of the vesicles did not affect the Kp values at each aminophospholipid content suggesting that the partition of the phenothiazine drugs was not affected by the structural differences in the vesicles such as their curvature or asymmetric distribution of the phospholipids between the outer and inner layers of the bilayer membranes. However, the Kp values of both drugs increased remarkably according to the PS content in the bilayer membranes, i.e., the Kp values for the vesicles of 30 mol% PS content were about 3 times of that for the vesicles of PC alone, while both Kp values slightly reduced with the increase in the content of PE in the bilayer membranes of PC-PE vesicles. The results indicate that both drugs have higher affinity for the PC-PS bilayer membranes than for the PC and PC-PE membranes, which can offer an evidence for the fact that TFZ and CPZ are predominantly distributed and accumulated in the brain and nerve cell membranes that contain PS abundantly.

Determination of Attapulgite and Nifuroxazide in Pharmaceutical Formulations by Sequential Digital Derivative Spectrophotometry

A new method for the sequential determination of attapulgite and nifuroxazide in pharmaceutical formulations by first- and second-derivative spectrophotometry, respectively, has been developed. In order to obtain the optimal conditions for nifuroxazide stability, studies of solvent, light, and temperature effects were performed. The results show that a previous hydrolysis of 2 h in 1.0 x 10(-1)M NaOH solution is necessary in order to obtain stable compounds for analytical purposes. Subsequently, the first- and second-derivative spectra were evaluated directly in the same samples. The sequential determination of the drugs can be performed using the zero-crossing method; the attapulgite determination was carried out using the first derivative at 278.0 nm and the nifuroxazide determination, using the second derivative at 282.0 nm. The determination ranges were 5.7 x 10(-6)-1.0 x 10(-4) and 3.7 x 10(-8) -1.2 x 10(-4)M for attapulgite and nifuroxazide, respectively. Repeatability (relative standard deviation) values of 1.2 and 3.0% were observed for attapulgite and nifuroxazide, respectively. The ingredients commonly found in commercial pharmaceutical formulations do not interfere. The proposed method was applied to the determination of these drugs in tablets. Further, infrared spectroscopy and cyclic voltammetry studies were carried out in order to obtain knowledge of the decomposition products of nifuroxazide.

COMPARATIVE STUDY OF MICROENCAPSULATION OF CASEIN HYDROLYSATES IN LIPOSPHERES AND LIPOSOMES

The encapsulation in lipospheres and in liposomes was used with the aim of masking the bitterness of casein hydrolysates for dietetic of pharmaceutical purposes. Papain was used for preparing three casein hydrolysates, employing different temperatures and E:S ratios. The percentage of encapsulation of these preparations was measured by second derivative spectrophotometry (SDS). Lipid oxidation over a period of 60 days, was followed by quantifying the 2-thiobarbituric acid reactive substances (TBARS). Other analysis were performed for characterizing these vesicles, including the sensory evaluation and the measure of hydrophobicity. The results showed that these two encapsulation systems were equally efficient in reducing the hydrophobicity and the bitterness of casein hydrolysates. SDS was a useful tool in the characterization of these preparations. It is a quick and relatively low-cost method, and indicated that the encapsulation rate in lipospheres (65%) was higher than in liposomes (59%). The TBARS method revealed the chemical stability of these preparations over the period of study (60 days).

Second and first-derivative spectrophotometry for efficient simultaneous and individual determination of palladium and cobalt using 1-(2-pyridylazo)-2-naphthol in sodium dodecylsulfate micellar media.

1-(2-Pyridylazo)-2-naphthol (PAN) has been used for the simultaneous and individual determination of palladium and cobalt at trace levels. PAN complexes of palladium and cobalt at neutral pH form green-color neutral complexes, which are soluble in aqueous SDS micellar media. Under optimum conditions, calibration graphs for individual determinations by zero and first-derivative spectrophotometry, and also for simultaneous determinations by second-derivative spectrophotometry were obtained. A zero-crossing method using second-derivative spectrophotometry at 628 or 578 and 614 nm, respectively, for cobalt and palladium was used for simultaneous determinations. The method is able to determine the cobalt-to-palladium ratio, 5:1 to 1:10 (Wt/Wt), accurately. The accuracy and reproducibility of the determination method for various known amounts of cobalt and palladium in their binary mixtures were tested. The effects of diverse ions on the determination of cobalt and palladium to investigate the selectivity of the method were also studied. The recommended procedures were applied to a synthetic binary alloy, cobalt in vitamin B12 and B-complex ampoules, a Co2O3-Co3O4 laboratorial chemical mixture, some synthetic cobalt-alloy samples, a Pd-charcoal catalyst, and some synthetic palladium alloys.

Stability-indicating methods for the determination of sumatriptan succinate

Four stability-indicating methods were developed for the determination of sumatriptan succinate in the presence of its degradation products. The first method depends on the quantitative densitometric evaluation of thin-layer chromatography of sumatriptan succinate in the presence of its degradation products without any interference. Cyclohexane–dichloromethane–diethylamine (50:40:10 v/v/v) was used as a mobile phase and the chromatogram was scanned at 228 nm. This method determines sumatriptan succinate in the concentration range l–8 μg per spot with mean percentage recovery 100.52±1.23%. The second and third methods depend on the use of first-derivative (D 1) and second-derivative (D 2) spectrophotometry at 234 and 238 nm, respectively. These methods determine the drug in the concentration range 1.25–10 μg ml −1 with mean percentage recovery 99.91±1.01% and 99.96±1.13% for (D 1) and (D 2), respectively. The fourth method depends on the use of ratio derivative spectrophotometric technique. The amplitude in the first derivative of the ratio spectra at 235 nm was selected to determine the cited drug in the presence of its degradation products. Calibration graph is linear in the concentration range 1.25–10 μg ml −1 with mean percentage recovery 100.19±1.19%. The suggested methods were successfully applied for determining sumatriptan succinate in bulk powder, laboratory-prepared mixtures and pharmaceutical dosage forms (Imigran tablet) with good accuracy and precision. The results obtained by applying the proposed methods were statistically analyzed and compared with those obtained by the reported method.

Determination of binary mixtures of analgesic and spasmolytic drugs in pure and dosage forms by derivative spectrophotometry

Binary mixtures of dipyrone and pitophenone hydrochloride are assayed by zero-crossing second- and third-derivative spectrophotometry and by ratio-spectra first- and second-derivative spectrophotometry. In the first method, calibration plots are linear at 266.5 and 302.5 nm (dipyrone, second derivative), and 257 and 286 nm (pitophenone second derivative) and 242 and 278.3 nm (dipyrone third derivative), and 228.5 and 300 nm (pitophenone, third-derivative). By the second method, lines of regression are linear at 235 and 262 nm (dipyrone, first derivative), and 229.5 and 288.5 nm (pitophenone, first-derivative), and 249.7 and 268 nm (dipyrone, second derivative), and 280.5 and 300 nm (pitophenone, second-derivative). In all methods calibration curves follow the Beer's law up to 40 μg/ml of each drug. LOD and LOQ values were calculated. The developed derivative spectrophotometric methods were applied to laboratory mixtures and to vials for these drugs. The procedures are simple, rapid, and did not require any preliminary separation or treatment of the samples.

Thermodynamics of partitioning of phenothiazine drugs between phosphatidylcholine bilayer vesicles and water studied by second-derivative spectrophotometry.

The partition coefficients (Kps) of phenothiazine drugs (trifluoperazine, triflupromazine, chlorpromazine and promazine) between phosphatidylcholine (PC) small unilamellar vesicles (SUV) and water were determined over the temperature range of 10-40 degrees C by a second-derivative spectrophotometric method. The second derivative spectra of each drug solution containing various amounts of SUV showed distinct derivative isosbestic points confirming the entire elimination of the residual background signal effects of the SUV. The Kp values were calculated from the derivative intensity change of the drugs induced by the addition of SUV to the drug buffer solutions (pH 7.4) and obtained with the R.S.D. below 10% (n=3). The van't Hoff analysis of the temperature dependence of Kp values revealed negative deltaH(w-->l) and positive deltaS(w-->l), suggesting an enthalpy/entropy driven mechanism for the phenothiazine partitioning. The negative deltaH(w-->l) implies that the electrostatic interaction, positively charged alkyl amino groups of phenothiazine drugs with negatively charged phosphate groups on the surface of PC SUV, partly contributes to the partitioning. The existence of halogen atom(s) on the phenothiazine ring at position C-2 enhanced the Kp value (H<Cl<CF3). This enhancement can be accounted for by an increase in the deltaS(w-->l) value (H<Cl<CF3), and the deltaS(w-->l) increase is considered to be enhancement of disorder in the hydrophobic acyl chain regions of PC SUV membranes derived from the phenothiazine ring insertion and thus depends on the bulkiness of the substituent. The enthalpy-entropy correlation analysis yielding a good linear relationship also suggests that the phenothiazine drugs studied have identically an enthalpy-entropy compensation mechanism for the partitioning.

Microencapsulamento de hidrolisados de caseína em lipoesferas para mascarar o sabor amargo: avaliação físico-química e sensorial

A hidrolise enzimatica de proteinas pode levar ao desenvolvimento de sabor amargo, associado a liberacao de grupos hidrofobicos. Neste trabalho, desenvolveu-se uma nova metodologia, baseada no encapsulamento em lipoesferas, para mascarar o sabor amargo de hidrolisados de caseina obtidos pela acao da papaina. Alem disso, utilizou-se a espectrofotometria derivada segunda (EDS), como metodo de determinacao da taxa de encapsulamento de hidrolisados enzimaticos de proteinas, e as amostras analisadas apresentaram valores em torno de 66%. Este microencapsulamento mostrou ser uma tecnologia eficiente para reduzir a hidrofobicidade e o sabor amargo de hidrolisados de caseina. A analise por microscopia eletronica de varredura revelou a morfologia esferica das microcapsulas e a medida da oxidacao lipidica mostrou boa estabilidade quimica por periodo de ate 60 dias.

Simultaneous Determination of Estradiol and Medroxyprogesterone Acetate in Pharmaceutical Formulations by Second-Derivative Spectrophotometry

This paper reports a simple and fast method for the simultaneous determination of estradiol (ED) and medroxyprogesterone acetate (MP) in pharmaceutical formulations by second-derivative spectrophotometry. Methanol was used to extract the drugs from formulations, and subsequently the extracts were evaluated directly by derivative spectrophotometry. The drugs were determined simultaneously by using the graphic method at 297.4 nm for ED and the zero-crossing method at 273.4 nm for MP. If both compounds are present together in a sample, it is possible to quantitate one in the presence of the other. The best signal-to-noise ratio was found when the second derivative of the spectrum was used. The linear ranges for determination of the drugs were 4.7 x 10(-6) to 1.6 x 10(-4) and 7.2 x 10(-6) to 2.0 x 10(-4) mol/L for ED and MP, respectively. The ingredients commonly found in commercial pharmaceutical formulations do not interfere with the determination. Chemical and spectral variables were optimized for the determination of both analytes. Good levels of repeatability (relative standard deviation), 1.4 and 1.9%, were obtained for ED and MP, respectively. The proposed method was applied to the determination of these drugs in pharmaceutical formulations.

Derivative spectrophotometry in the determination of phenyl-beta-naphthylamine used as an antioxidant in rubber mixtures.

A method for the determination of phenyl-beta-naphthylamine (PBN) in ternary mixtures by second-derivative spectrophotometry is described. The procedure works without any separation step of PBN from the other polymer additives. By applying the second-derivative spectrophotometry, Beer's law was valid over the range 0.25-10 micro g mL(-1). The proposed method has been applied to the determination PBN in synthetic ternary mixtures and rubber samples. A comparative study of the results obtained using the second and the third-derivative spectrophotometric methods is presented and evaluated. The derivative spectrophotometric method indicated that the amount of PBN found after extraction from the rubber samples was 0.97+/-0.02 g/100 g of sample.

Padronização de método analítico para avaliação do grau de exposição da fenilalanina em hidrolisados de caseína, por espectrofotometria derivada segunda

Hidrolisados proteicos com baixo teor ou isentos de fenilalanina (Phe) tem sido empregados em formulacoes para fenilcetonuricos. Varias condicoes de hidrolise enzimatica tem sido propostas na literatura para promover a liberacao de Phe e, assim, facilitar sua remocao posterior. Neste trabalho, a espectrofotometria derivada segunda (EDS), um metodo analitico rapido, simples e de custo relativamente baixo, foi utilizada, inicialmente, para a caracterizacao dos aminoacidos aromaticos e, em seguida, para a determinacao do grau de exposicao da Phe em diferentes hidrolisados de caseina, obtidos pela acao da papaina. Os resultados obtidos indicam que o hidrolisado preparado a temperatura de 37 oC, relacao enzima/substrato de 4%, pH 7,5, foi o que apresentou o maior grau de exposicao da Phe, sendo o mais indicado para a preparacao de dietas para fenilcetonuricos. Com relacao a caracterizacao dos aminoacidos aromaticos, o emprego da EDS permitiu a separacao dos picos de tirosina (Tyr) e triptofano (Trp), em pH 13,0. Alem disso, observou-se semelhanca entre os espectros de derivada segunda das solucoes contendo somente os aminoacidos aromaticos e dos hidrolisados de caseina.

Second-Derivative Spectrophotometric Determination of Trace Copper after Preconcentration with the Ion Pair of 2-Nitroso-1-Naphthol-4-Sulfonic Acid and Tetradecyldimethylbenzylammonium Chloride on Microcrystalline Naphthalene or a Column

Copper is quantitatively retained by 2-nitroso-1-naphthol-4-sulfonic acid and tetradecyldimethylbenzylammonium chloride on microcrystalline naphthalene in the pH range 7.1–10.7 from large volumes of aqueous solutions of various samples. After filtration, the solid mass consisting of a copper complex and naphthalene is dissolved with 5 mL of dimethylformamide, and the metal is determined by second-derivative spectrophotometry. The copper complex can alternatively be quantitatively adsorbed on tetradecyldimethylbenzylammonium–naphthalene adsorbent packed in a column and determined similarly. About 1.5 μg of copper can be concentrated in a column from 300 mL of aqueous sample, where its concentration is as low as 5 ng/mL. The effects of pH, the volume of the aqueous phase, and interferences from a number of metal ions on the determination of copper have been studied in detail to optimize the conditions for its determination in standard alloys and biological samples.

Determination of acidity constants of acid–base indicators by second-derivative spectrophotometry

A method for calculation of acid–base dissociation constants of monoprotic weak organic acids whose acid and base species have overlapping spectra from absorptiometric and pH measurements is described. It has been shown that the second-derivative spectrophotometry can effectively be used for determining the dissociation constants, when dissociation constants obtained for methyl orange and bromothymol blue were compared with the values given in the literature.

Evaluation of a second derivative UV/visible spectroscopy technique for nitrate and total nitrogen analysis of wastewater samples

A method for nitrate analysis based on second derivative UV/Visible spectroscopy was developed by Simal et al. (1985: Simal J., Lage M. A., and Iglesias I. (1985) Second derivative ultraviolet spectroscopy and sulfamic acid method for determination of nitrates in water. J. Assoc. Analyt. Chem. 68, 962–964) and Suzuki and Kuroda (1987: Suzuki, N. and Kuroda R. (1987) Direct simultaneous determination of nitrate and nitrite by ultraviolet second-derivative spectrophotometry. Analyst 112, 1077–1079), and later modified for the analysis of total nitrogen in aqueous samples of varying nitrate:organic nitrogen ratios ( Crumpton et al., 1992 : Crumpton W. G., Isenhart T. M. and Mitchell P. D. (1992) Nitrate and organic N analyses with second-derivative spectroscopy. Limnol. Oceanogr. 37, 907–913). The procedure uses the second derivative of the absorption spectrum for nitrate (NO − 3), which has a peak at ∼224 nm that is proportional to the NO − 3 concentration. Samples for total N analysis are first oxidized to NO − 3 by persulfate digestion. The objectives of this study were to: (1) test the accuracy and precision of the second derivative method through the use of NIST-traceable wastewater check samples; (2) determine whether the second derivative method for nitrate analysis can be used for wastewater samples and whether the method compares favorably with other currently used nitrate analysis methods; and (3) use the method to analyze wastewater samples containing a range of nitrate and total nitrogen concentrations. Our results indicated that the method needed to be modified to include a longer digestion time (60 min) and dilution of samples prior to digestion (if needed). With the modified method, nitrogen recoveries were not significantly different ( P≥0.05) from samples with known N concentrations. In addition, nitrate concentrations in constructed wetland and wastewater samples analyzed by both second derivative spectroscopy and ion chromatography were not significantly different. Total nitrogen concentrations in wastewater samples also compared favorably to the same samples analyzed by Kjeldahl digestion. The method is faster, simpler, requires smaller sample volumes, and generates less waste than many EPA-approved methods of N analysis, and may offer a suitable alternative to current methods for analysis of nitrate and total N in wastewater samples.

Evaluation of lipid ultraviolet absorption as a parameter to measure lipid oxidation in dark chicken meat.

The application of lipid UV absorption (235, 269, and 280 nm) to follow up lipid oxidation in dark chicken meat has been evaluated using raw and cooked samples with different alpha-tocopherol contents (modulated by dietary supplementation). To this purpose, when absorption was measured at 235 nm, second-derivative spectrophotometry did not show any significant advantage over nonderivative spectrophotometry. For absorption at 269 and 280 nm, nonderivative spectrophotometry more sensitively monitored lipid oxidation than second- and third-derivative spectrophotometry. In addition, only direct measurements at 235 and 269 nm and second-derivative measurements at 235 nm showed a limited usefulness to follow up lipid oxidation in our samples. However, these UV absorption parameters were much less effective than lipid hydroperoxide values measured through a ferrous oxidation-xylenol orange method and 2-thiobarbituric acid values determined by a third-derivative spectrophotometric method with acid aqueous extraction.

The Second-Derivative Spectrophotometric Assay of a Multicomponent Analgetic Mixture

In this paper the second-derivative spectrophotometric method for the simultaneous determination of some analgetic ingredients was described. Optimal conditions for the quantitative analysis of the three-component analgetic mixture of Dalivon® tablets were settled. The second-derivative order of the spectra in sodium hydroxide with the wavelength modulation was used. For the determination of paracetamol the “zero-crossing” technique was applied, but for propyphenazone and caffeine the characteristic peak amplitude had to be corrected. The authors propose this second-derivative spectrophotometry for a rapid, simple, precise and accurate determination of the Dalivon® tablets or a corresponding multicomponent mixture.

Simultaneous determination of manganese and zinc in mixtures using first- and second-derivative spectrophotometry

A new direct spectrophotometric determination of manganese with 5,8-dihydroxy-1,4-naphthoquinone (naphthazarin,NAZA) is reported. Absorption maximum, molar absorptivity and Sandell’s sensitivity of 1:2 (M:L) complex are 695 nm, 1.88×10 4 l mol −1 cm −1 and 2.92 ng cm −2, respectively. A linear calibration graph is obtained up to a concentration of 7.2 μg ml −1 of manganese. The optimum range for determination (Ringbom) is between 0.20 and 6.8 μg ml −1. A rapid method for simultaneous determination of manganese and zinc in their mixture using derivative spectra is described. The range 0.28–5.6 μg ml −1 manganese could be determined in the presence of 0.33–6.8 μg ml −1 zinc and vice versa. The developed method was applied to the simultaneous spectrophotometric determination of manganese and zinc in some synthetic mixtures and was found to give satisfactory results.

Simultaneous determination of tinidazole, furazolidone and diloxanide furoate in a combined tablet preparation by second-derivative spectrophotometry

A second-derivative spectrophotometric procedure has been developed for the simultaneous determination of tinidazole (TD), furazolidone (FD) and diloxanide furoate (DF) in a commercial preparation. The method consists of the utilization of second-derivative absorption spectra of tablet extract in distilled water and then determination of the analyte concentration in the mixture was carried out using zero-crossing (ZC) and ratio-compensation (RC) techniques. Calibration graphs constructed at their wavelengths of determination were linear in the concentration range of TD (5–20 μg ml −1), FD (2.5–10 μg ml −1) and DF (7.5–15 μg ml −1). The results were found to be accurate and free from interference. The details of the statistical treatment of analytical data are also presented.

Effects of Particle Size and Cholesterol Content on the Partition Coefficients of Chlorpromazine and Triflupromazine between Phosphatidylcholine–Cholesterol Bilayers of Unilamellar Vesicles and Water Studied by Second-Derivative Spectrophotometry

Phosphatidylcholine(PC)–cholesterol (0–30 mol%) unilamellar vesicles of several sizes (20–600 nm) were prepared in buffer (pH 7.4) solutions by sonication or extrusion methods. The vesicle size was measured by a dynamic light-scattering method. Absorption spectra of chlorpromazine (CPZ) and triflupromazine (TFZ) in the presence of these vesicles showed a bathochromic shift according to the increase in vesicle concentration, but the counterbalance of the baseline was incomplete due to the intensive light scattering by the vesicles; thus, no isosbestic point could be observed. In the second-derivative spectra, the residual background signal effects were eliminated and three derivative isosbestic points were clearly observed for both drugs. The derivative intensity change (ΔD) induced by the addition of the vesicles was measured at the λmax of each drug. From the relationship between the ΔD value and the lipid concentration, the partition coefficients (Kp) of CPZ and TFZ between these vesicles and water (buffer) were calculated. The results revealed that the vesicle size (20–600 nm) and preparation method do not affect the Kp values, and although the incorporation of cholesterol into the PC bilayers induces a decrease of the Kp values, the vesicle size also did not affect the Kp values in vesicles of the same cholesterol content.