First Derivative Mode Research Articles

SIMULTANEOUS QUANTIFICATION OF ACETYLSALICYLIC ACID AND CAFFEINE IN TABLETS BY FIRST-ORDER DERIVATIVE SPECTROSCOPY

Objective: To develop an apply a new and easy UV-derivative method for the simultaneous quantification of acetylsalicylic acid (ASA) and caffeine (CAF) in commercial tablets. Derivative spectroscopy is an analytical methodology used to identify drugs in a mixture of two or more compounds without use of toxic dissolvents that are involved in chromatographic determinations. Methods: Standard solutions of ASA (40-120 µg/ml) and CAF (5-25 µg/ml) were prepared with 0.1 M phosphate buffer pH 7.4. The zero-order spectra were determined from 200-300 nm. The method was validated according to International Conference on Harmonization (ICH) guidelines. An USP Apparatus 2 at 75 rpm with 900 ml of 0.1 M phosphate buffer pH 7.4 was used. For each drug, common dissolution data as the amount of drug released at 60 min (Q60), mean dissolution time (MDT), dissolution efficiency (DE), t50% and t85% were calculated. Results: ASA was identified at 245 nm and CAF at 295 nm in the first-derivative mode. The method was linear (R2>0.99, *P<0.05). The precision and accuracy of the method were within acceptable limits. Q60, MDT, DE, t50%, and t85% values for ASA were 102.09%, 8.18 min, 88.15%, 2.91 min, and 11.98 min, respectively. Same parameters for CAF were 99.17%, 5.21 min, 90.54%, 1.09 min, and 5.70 min, respectively. Conclusion: The proposed UV-derivative method is rapid and simple and can be easily adopted to determine the in vitro release curves of ASA and CAF from commercial tablets. The method generates reliable information that can be compared with published data.

Characteristic losses in metals: Al, Be, and Ni

Information about the occupied portion of the surface density of states of materials can be derived from electron-excited Auger electron spectroscopy (AES), which is a standard experimental technique in most surface science laboratories. Surface sensitive experimental techniques that provide information regarding the unoccupied portion of the surface density of states are often not standard and are not so readily available. Here we explore the possibility of utilizing the same experimental equipment as in AES to derive information about the unoccupied portion of the surface density of states from a characteristic loss spectroscopy, in particular, from core-level inelastic electron-scattering spectroscopy (CLIESS). An important application of this technique is in comparative studies. CLIESS spectra from clean surfaces of aluminum, beryllium and nickel are presented. These data were taken in the first-derivative mode using the reflection of monoenergetic primary beams of 450 eV energy for Be, and 300 eV for Al and Ni. The Al and Be spectra had to be extracted from overlapping plasmon signals using synthesized plasmon spectra based on the behavior of these spectra between the elastic peak energy and the respective core level threshold energies. After applying loss-deconvolution techniques to remove secondary loss spectral distortions, integral spectra were obtained which compared well to corresponding experimental soft x-ray absorption and transmission electron-energy loss data as well as to theoretical calculations of the unoccupied density-of-states for these materials. Comparison similarities as well as some differences are discussed. Finally, in order to illustrate the potential these signals have in serving as “fingerprints” of surface chemistry, derivative metal-CLIESS curves for the three oxide surfaces of the metals are also presented.

Simultaneous determination of aluminium and iron in glasses,phosphate rocks and cement using first- and second-derivative spectrophotometry.

First- and second-derivative spectrophoto-metric methods for the simultaneous determination of aluminium and iron in their mixtures are described. The methods are based on the colored complexes formed by aluminium and iron with hematoxylin in the presence of cetyltrimethylammonium bromide as a surfactant. The zero-crossing method has been utilized to measure the first- and second-derivative value of the derivative spectrum. Aluminium (0.05-1 microg ml(-1)) could be determined in the presence of iron (0.09-1.6 microg ml(-1)) and vice versa. The detection limits of aluminium and iron are 0.01 and 0.09 microg ml(-1), respectively in the first-derivative mode and 0.014 and 0.1 microg ml(-1) in the second-derivative mode. The proposed method has been applied to the simultaneous determination of aluminium and iron in glasses, phosphate rocks, cement and magnesite alloy.

Flow injection–Fourier transform infrared spectrometric determination of paracetamol in pharmaceuticals

A procedure for the direct FTIR spectrometric determination of paracetamol in pharmaceuticals is described. The method is based on the solubilization of paracetamol in a 10% v/v ethanol in CH2Cl2 solution and direct absorbance measurement at 1515 cm–1, using the baseline established at 1900 cm–1 for measurement correction. The procedure can be carried out in both the stopped-flow and flow injection (FI) modes. In both instances the sensitivity is approximately 0.09 A ml mg–1, the limit of detection being 8 µg ml–1 in the stopped-flow mode and 33 µg ml–1 in the FI mode. Caffeine, acetylsalicylic acid, propyphenazone and ascorbic acid do not interfere with the FTIR determination of paracetamol, and the interference of citric acid can be eliminated by using measurements between 1518 and 1509 cm–1 in the first-derivative mode. The FI-FTIR methodology provides a fast and appropriate technique for the routine analysis of pharmaceuticals with a throughput of 45 samples h–1.

Determination of ternary mixtures of antibiotics, by ratio-spectra zero-crossing first- and third-derivative spectrophotometry

The ratio-spectra zero-crossing first- and third-derivative spectrophotometry have been used for determining ternary mixtures of penicillin-G sodium, penicillin-G procain and dihydrostreptomycin sulphate salts. The procedures are accurate, nondestructive and do not require resolutions of equations. In both methods, calibration graphs are linear, with zero-intercept, up to 30 μg ml −1 of penicillin-G sodium and penicillin-G procain, and up to 42 μg ml −1 of dihydrostreptomycin sulphate. r = 0.9999 in each instance. Working wavelengths, 218.5, 211 and 236 nm, respectively, in the first-derivative mode, and 222.5, 311.5 and 242 nm in the third-derivative mode. Detection limits for each drug at p = 0.01 level of significance were calculated to be 0.058, 0.010 and 0.014 μg ml −1 and 0.14, 0.012 and 0.34 μg ml −1, in the first- and third-derivative methods, respectively. Both methods apply favourably to either laboratory mixtures or commercial injections.

Simultaneous determination of clopamide-pindolol combination in tablets by zero-crossing derivative spectrophotometry

A first-derivative spectrophotometric method, using a ‘zero-crossing’ technique of measurement has been used for determining clopamide-pindolol mixture in tablets. In the first-derivative mode the zero-crossing points of clopamide and pindolol occur at 272.6 and 262.4 nm, respectively. The relative ease offered by this technique for the quantification of these drugs with closely overlapping bands was demonstrated. The linearity of the calibration curves was satisfactory ( r = 0.9998) and the precision (RSD%) better than 1.89. Detection limits were 0.50 and 0.44 μg ml −1 for pindolol and clopamide, respectively. No spectral interferences from tablet excipients were found. Applications are given for the assay of commercial tablets and content uniformity test. The procedures proved to be suitable for rapid and reliable quality control.

First- and second-derivative spectrophotometric determination of imipenem and cilastatin in injections.

First- and second-derivative spectrophotometry has been used for the quantitation of mixtures of imipenem and cilastatin sodium, compounds that have closely overlapping spectral bands. Beer's law was obeyed at concentrations up to 100 micrograms ml-1 of imipenem in both the first- and second-derivative modes and up to 75 micrograms ml-1 of cilastatin in the first-derivative mode. Detection limits at the P = 0.05 level of significance were calculated to be 0.40 and 0.52 micrograms ml-1 of imipenem and cilastatin sodium, respectively, in the first-derivative mode, and in a range from 0.45 to 0.68 micrograms ml-1 for imipenem in the second-derivative mode. The method, which is rapid, simple and does not require a separation step, has been successfully applied to the assay of commercial injections.

The magic size determined by valence fluctuation in germanium atom clusters

When the size of solids becomes smaller than the critical size of the nanometre scale, their bonding states and atom periodicity are influenced. As a result, the properties of materials are changed remarkably [1]. Such functional ultrafine particles are here named "atom clusters". The interatomic bondings, particularly in atom clusters, differ from those in bulk crystals because the size of the region affected by the long-range interaction force among the constitutive atoms is close to or larger than the cluster size. We call such a cluster size the "magic size". The behaviour of semiconducting materials in the size below the magic size, particularly relating to structural fluctuations, has been observed as follows. The relationship between the crystalline size and lattice constant of silicon measured by X-ray diffraction suggested that amorphization occurs with decreasing crystalline size [2]. In addition, the Raman spectra of silicon and germanium ultrafine particles changed to amorphous-like spectra with decreasing particle sizes [3-5]. These results show that the magic size is 2-10 nm in covalent materials, such as silicon and germanium. The purpose of this work was to determine the magic size of germanium on the basis of a fluctuation of the valence electronic states in germanium atom clusters by Auger valence-electron spectroscopy (AES). Germanium atom clusters were prepared by the vacuum vapour deposition method. Germanium was first evaporated on a film-substrate of amorphous carbon from a tungsten filament under a base pressure below 4.0 x 10 -8 Pa at room temperature. The germanium deposition here became an amorphous film. Therefore, in order to form atom clusters, these films were heated by electron bombardment at 573 K for 1.8 ks (the formation of atom clusters under this condition was ascertained by in situ observation under heating in a transmission electron microscope (TEM)). The cluster sizes were controlled by the germanium coverages. After the preparations, the Ge Auger valence spectra were measured in the first-derivative mode with the resolution of A E / E = 0.3% by summing up more than 30 scans and processing by numerical integrations. The electron gun was operated at the primary acceleration voltage of 3 kV and the primary specimen current of 0.2 ~tA. The size distributions of clusters in the same specimen as that measured by AES were estimated by TEM observation. The average diameters were calculated from histograms. In addition, the germanium atom dusters were formed on MgO single crystals under the same conditions to observe the profile images of the clusters. The microstructures were observed by the many-beam lattice image method. The TEM used was operated at 200 and 300 kV. It was confirmed that the specimen was not damaged by the primary electron beam from 200 to 300 kV. Fig. 1 shows the Ge (M2,3Mn5V) Auger valence spectra as a function of the cluster size, where V indicates the Ge 4s(N1) and 4p(N23) valence states. As the Auger lineshape fluctuates variously in clusters below about 7 nm in size, a typical one (i.e.

Derivative Spectrophotometric Determination of Levodopa and Benserazide Hydrochloride

Abstract First-derivative spectrophotometry is used to evaluate a mixture containing levodopa and benserazide hydrochloride. Levodopa is determined by zero-crossing measurement at 267 nm. The height of the valley at 232 nm is used to calculate the amount of benserazide hydrochloride in mixture. Second-derivative mode is also used to estimate the amount of levodopa. Both drugs are successfully determined in Madopar capsules using first-derivative mode.

Zero-Crossing Derivative Spectrophotometry for the Determination of Mixtures of Cephaloridine and Cephalothin in Pure and Dosage Forms

AbstractFirst-and second-derivative Spectrophotometry, with a zero-crossing technique of measurement, has been used for the quantitation of two-component mixtures of cepnaloridine and cephalothin Na, which are cephalosporins with closely overlapping spectral bands. Beer's Law is followed for up to 28 and 36 μg/mL of cephaloridine in the first- and second-derivative modes, respectively, and up to 36 μg/mL of cephalothin Na in both modes. Detection limits at the 0.05 level of significance were calculated to be 0.13 and 0.37 μg/mL of cephaloridine and cephalothin Na, respectively, in the first-derivative mode, and 0.25 and 0.29 μg/mL, respectively, in the second-derivative mode. The recovery of these antibiotics in mixtures of injectable dosage forms Is also reported.

"Zero-crossing" derivative spectrophotometric determination of mixtures of cephapirin sodium and cefuroxime sodium in pure form and in injections.

Two-component mixtures of cephapirin Na and cefuroxime Na were assayed by first- and second-derivative spectrophotometric methods using a “zero-crossing” technique of measurement. The relative ease offered by this technique for the quantification of these drugs with closely overlapping spectral bands was clearly demonstrated. Beer's law holds up to 40 µg ml–1 for both cephalosporins. The detection limits of cephapirin Na and cefuroxime Na, at a 0.05 level of significance, were calculated to be 0.34 and 0.85 µg ml–1, respectively, in the first-derivative mode and 0.37 and 0.64 µg ml–1 in the second-derivative mode. The results of the determination of these antibiotics in mixtures of injectable dosage forms are also presented.