Development and validation spectroscopic methods for the determination of lomefloxacin in bulk and pharmaceutical formulations

Four simple, sensitive spectrophotometric and spectrofluorimetric methods (A-D) for the determination of antibacterial drug lomefloxacin (LMFX) in pharmaceutical formulations have been developed. Method A is based on formation of ternary complex between Pd(II), eosin and LMFX in the presence of methyl cellulose as surfactant and acetate-HCl buffer pH 4.0. Spectrophotometrically, under the optimum conditions, the ternary complex showed absorption maximum at 530 nm. Methods B and C are based on redox reaction between LMFX and KMnO₄ in acid and alkaline media. In indirect spectrophotometry method B the drug solution is treated with a known excess of KMnO₄ in H₂SO₄ medium and subsequent determination of unreacted oxidant by reacting it with safronine O in the same medium at λ_max = 520 nm. Direct spectrophotometry method C involves treating the alkaline solution of LMFX with KMnO4 and measuring the bluish green product at 604 nm. Method D is based on the chelation of LMFX with Zr(IV) to produce fluorescent chelate. At the optimum reaction conditions, the drug-metal chelate showed excitation maxima at 280 nm and emission maxima at 443 nm. The optimum experimental parameters for the reactions have 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 drug in pharmaceutical preparations with good recoveries.     

Colorimetric microdetermination of captopril in pure form and in pharmaceutical formulations

A simple, rapid, accurate, precise and sensitive colorimetric method for the determination of captopril (CAP) in bulk sample and in dosage forms is described. The method is based on oxidation of the drug by potassium permanganate in acidic medium and determination of the unreacted oxidant by measuring the decrease in absorbance for five different dyes; methylene blue (MB); acid blue 74 (AB), acid red 73 (AR), amaranth dye (AM) and acid orange 7 (AO) at a suitable λ_max (660, 610, 510, 520, and 485 nm), respectively. Regression analysis of Beer's plots showed good correlation in the concentration ranges (0.4-12.5, 0.3-10, 0.5-11, 0.4-8.3 and 0.5-9.3 μg ml⁻¹), respectively. The apparent molar absorbtivity, Sandell sensitivity, detection and quantitation limits were calculated. For more accurate results, Ringbom optimum concentration ranges were 0.5-12, 0.5-9.6, 0.6-10.5, 0.5-8.0 and 0.7-9.0 μg ml⁻¹, respectively. The validity of the proposed method was tested by analyzing in pure and dosage forms containing CAP whether alone or in combination with hydrochlorothiazide. Statistical analysis of the results reflects that the proposed procedures are precise, accurate and easily applicable for the determination of CAP in pure form and in pharmaceutical preparations. Also, the stability constant was determined and the free energy change was calculated potentiometrically.     

Spectrophotometric and Fluorimetric Methods for the Determination of Methoxamine Hc1 in Bulk Drugs and in Ampoules

Abstract

Three simple and sensitive methods for the determination of methoxamine HCl in bulk drugs and in ampoules were proposed. The methods are based on the oxidation of methoxamine HCl by sodium periodate, potassium permanganate and cerium(IV)sulphate. The first two reactions are followed spectrophotometrically by measuring the absorbance at 352 &; 608 nm for the periodate and permanganate methods, respectively. The third method is based on measuring the relative fluorescence intensity of Ce(III)arising from Ce(IV) at 348 nm with excitation wavelength at 257 nm. The different experimental parameters were carefully studied. Under the described conditions the proposed methods were applicable over the concentration ranges 10.0 - 40.0, 2.0-10.0 and 0.05-0.30 μg ml^?1 for the three methods, respectively.     

Fluorimetric Determination of Ketorolac in Urine by Stopped-Flow Sequential Injection Analysis

ABSTRACT

An automatic fluorescence method was developed for the determination of ketorolac tromethamine. The method is based on the direct oxidation of the analyte by an acidic solution of permanganate, being the resulting fluorescence measured at 227 nm/320 nm (λ_ex/λ_em). The reaction is carried out online due to the use of the Sequential Injection Analysis methodology. A detection limit of 0.12 µ g mL^?1 and a R.S.D. lower than 3% (n = 10) were obtained under optimum conditions. The analyte was satisfactorily determined in pharmaceuticals and urine samples. Recovery experiments were carried out on human urine, with recoveries in the range 92–108%.     

酸性高锰酸钾体系荧光分光光度法测定多塞平新方法研究

硫酸介质中,多塞平可以还原高锰酸钾,生成强荧光产物,其在激发波长336nm,发射波长465nm处的荧光强度与多塞平浓度有良好的线性关系,拟定了测定多塞平的荧光分析新方法。该方法操作简便,灵敏度高,背景低,选择性好,测定多塞平的线性范围为0.1—40mg/L,检出限为0.026mg/L,用于药物中多塞平的测定,获得了令人满意的结果,并对反应机理进行了探讨。     

鲁米诺-高锰酸钾流动注射化学发光体系测定头孢呋辛钠

在碱性介质中,鲁米诺与高锰酸钾反应产生化学发光,头孢呋辛钠能增强其化学发光强度,据此,建立了流动注射化学发光测定头孢呋辛钠的新方法。在最佳实验条件下,相对发光强度与头孢呋辛钠的质量浓度在2.0×10-7—8.0×10-5g/mL范围内,呈良好的线性关系,方法的检出限为3.0×10-8g/mL;对8.0×10-6g/mL头孢呋辛钠进行11次平行测定,相对标准偏差为1.1%。该方法用于合成样品及尿样的测定,结果满意。     

A sensitive amperometric detection of dopamine agonist drug pramipexole at functionalized multi-walled carbon nanotubes (f-MWCNTs) modified electrode

The electrochemical detection of dopaminergic agonist drug pramipexole dihydrochloride monohydrate (PPX) has been investigated by cyclic voltammetric (CV) and amperometric i–t techniques at functionalized multi-walled carbon nanotubes-modified glassy carbon electrode. For the first time, a sensitive and rapid electrochemical method was developed for the determination of PPX. The surface morphological characteristics of the proposed electrode have been studied by using transmission electron microscopy (TEM); further, electrochemical impedance spectroscopy (EIS) and Fourier transform infrared spectroscopy (FTIR) have been employed. PPX shows an irreversible anodic peak, which may be ascribed to the oxidation of the –NH groups of PPX. The proposed method was showing good sensitivity of 0.993 μA μM^?1 cm^?2 with a linear range of 5 to 340 μM by amperometric i–t and CV technique shows a linear range of 12.5 to 313 μM with a sensitivity of 1.92 μA μM^?1 cm^?2. The recovery of PPX from blood serum samples was found 100.6 and 98.9 %, respectively. Furthermore, the proposed method has been demonstrated for the determination of PPX in commercially available pharmaceutical samples and good agreement of results obtained.     

氢化物发生-原子荧光光谱法间接测定牛奶中Cr(Ⅲ)和Cr(Ⅵ)

在盐酸浓度为3.0 mol·L-1介质中,Cr(Ⅵ)把As(Ⅲ)氧化成As(Ⅴ),利用氢化物发生-原子荧光光谱法(HG-AFS)测定剩余As(Ⅲ)的含量,间接得到Cr(Ⅵ)的含量。基于相同原理,结合高锰酸钾氧化Cr(Ⅲ)来测定Cr(Ⅲ)含量。研究了溶样方法和共存离子可能引起的干扰,优化了仪器工作条件、酸度及其他影响因素。在最佳条件下,铬含量在4.0～20 μg·L-1范围内线性关系良好,方法检出限为2.5 μg·L-1;将方法应用于牛奶样品分析,相对标准偏差(RSD,n=6)为1.6%～2.7%。加标回收率为96.5%～104.2%。     

Oxidation of Si(1 1 1) promoted by K multilayers: K and SiO2 islands

In the context of the alkali-metal promotion of Si oxidation, high-pressure oxidation of potassium multilayers on cooled Si(111) has been investigated using SEM, micro-AES and AFM. The oxidation process at high pressure turns the potassium islands observed at high coverage into potassium oxides islands. A subsequent potassium desorption at moderate temperature (900 K) yields SiO₂ islands (height of 20 nm and lateral dimensions of 10 m) surrounded by a thin continuous SiO₂ overlayer. Other conditions such as potassium multilayer coverage exposed to a low O₂ pressure, potassium monolayer or simultaneous potassium/oxygen adsorption yield a uniform SiO₂ overlayer.     

Use of Cerium (IV) in the Spectrophotometric and Spectrofluorimetric Determinations of Penicillins and Cephalosporins in Their Pharmaceutical Preparations

Spectrophotometric and spectrofluorimetric procedures for the quantitative determination of four penicillins [Amoxycillin (AMX), Bacampicillin (BAC), Piperacillin (PPN) and Sultamcillin (SULT)] and ten cephalosporins [Cefadroxil (CDL), Cefamandole nafate (MAN), Cefuroxime axetil or sodium (CFX), Cefaclor (CFCR), Ceftazidime (CZD), Ceftizoxime (CTIZ), Ceftriaxone (CTRX), Cefoperazone (CPZ), Cefixime (CXIM) and Cefpodoxime proxetil (CFPD)] are described. Both methods are based on the acidic oxidation of the antibiotics with cerium (IV) at elevated temperature. The effect of the reagent concentration, volume of the acid,and the heating temperature were studied to optimize the reaction conditions. Each antibiotic was determined by either measuring the absorbance difference at 317 nm or the cerous inherent fluorescence at 256 and 356 nm for excitation and emission wavelengths, respectively. The two procedures have been successfully applied to the assay of these antibiotics in their pharmaceutical dosage forms. The obtained results have been statistically compared with those obtained by the official methods.     

Specular X-ray reflectivity study of interfacial SiO2 layer in thermally annealed NiO/Si assembly

Present report details an analysis of X-ray reflectivity (XRR) for solution processed NiO thin films on Si (100) substrates. The films were annealed at 700–1,000 °C for 1 h in air. XRR data indicated growth of SiO₂ layer from ~8 nm at 700 °C to ~66 nm at 1,000 °C along with significant variation of electron density profile. X-ray photoelectron spectroscopy and X-ray diffraction studies were used as supporting studies for phase purity and oxidation states of the NiO thin films as well as interfacial SiO₂ layer.     

碘-淀粉分光光度法测定空气中甲醛浓度的影响因素

基于在硫酸介质中,痕量甲醛与过量重铬酸钾反应,剩余重铬酸钾在酸性条件下与碘化钾反应生成单质碘,利用碘与淀粉显色,生成蓝色络合物在596nm处有最大吸收,建立了碘-淀粉分光光度法测定甲醛含量,并讨论了反应介质、试剂用量、反应温度、反应时间及共存离子的影响,确定了最佳反应条件。实验结果表明:体系褪色程度与溶液中甲醛量在0.225—7.875μg/mL范围内时符合朗伯-比耳定律,线性回归方程为A596=0.1476C(μg/mL)+0.00199,相关系数为0.9994,表观摩尔吸光系数为4.428×103L·mol-1.cm-1。该法用于空气中的甲醛含量测定,结果与酚试剂法测定结果一致,RSD小于2.0%。     

Laser generated Ag and Ag–Au composite nanoparticles for refractive index sensor

Localized surface plasmon resonance (LSPR) wavelength of metal nanoparticles (NPs) is highly sensitive to size, shape and the surrounding medium. Metal targets were laser ablated in liquid for preparation of spherical Ag and Ag@Au core–shell NP colloidal solution for refractive index sensing. The LSPR peak wavelength and broadening of the NPs were monitored in different refractive index liquid. Quasi-static Mie theory simulation results show that refractive index sensitivity of Ag, Ag–Au alloy and Ag@Au core–shell NPs increases nearly linearly with size and shell thickness. However, the increased broadening of the LSPR peak with size, alloy concentration and Au shell thickness restricts the sensing resolution of these NPs. Figure-of-merit (FOM) was calculated to optimize the size of Ag NPs, concentration of Ag–Au alloy NPs and Au shell thickness of Ag@Au core–shell NPs. The refractive index sensitivity (RIS) and FOM were optimum in the size range 20–40 nm for Ag NPs. Laser generated Ag@Au NPs of Au shell thickness in the range of 1–2 nm showed optimum FOM, where thin layer of Au coating can improve the stability of Ag NPs.     

Preparation of n-ZnO/p-Si solar cells by oxidation of zinc nanoparticles: effect of oxidation temperature on the photovoltaic properties

In this study, n-ZnO/p-Si solar cells were fabricated by spraying ZnO nanoparticles (NPs) film synthesised by dissolving of high purity zinc in hydrogen peroxide H₂O₂ followed by thermal oxidation in air on p-type silicon substrates. The oxidation was carried out at different temperatures (200–500) °C. The crystalline structure of the ZnO NPs films was investigated by X-ray diffraction which indicated wurtzite structure films along (100) plane. The morphology of the NPs was studied by atomic force microscopy and scanning electron microscopy. The result showed an average grain size of ZnO NPs in the range of (72.7–95.8) nm and the surface roughness increasing with oxidation temperature. Three peaks located at ultraviolet, violet and green emission regions were noticed in the photoluminescence spectra of ZnO NPs. From optical studies, it was shown that the direct optical band gap is found to be in the range of (3.85–3.96) eV depended on the oxidation temperature. The synthesised ZnO films have n-type conductivity, and the mobility was in the range of (7–24) cm² V^?1 s^?1. Current–voltage I–V and capacitance–voltage C–V of ZnO NPs/Si heterojunction solar cell were investigated as function of oxidation temperature. The spectral response of n-ZnO NPs/p-Si solar cell showed two peaks of response and its maximum value approaching 0.62 mA W^?1 at λ = 800 nm. Solar cell oxidized at 500 °C gave open circuit voltage V _OC of 375 mV, short circuit current density J _SC of 25 mA cm^?2, a fill factor FF of 0.72, and conversion efficiency η of 6.79 % under illumination of 100 mW cm^?2.     

Application of potassium permanganate to spectrophotometric assay of metoclopramide hydrochloride in pharmaceuticals

Two simple, sensitive, and cost-effective spectrophotometric methods are described for the determination of metoclopramide hydrochloride (MCP) in pharmaceutical dosage forms. The methods are based on a redox reaction between MCP and KMnO₄ in alkaline and acid media. Direct spectrophotometry (method A) involves treating MCP with permanganate in an NaOH medium and measuring a bluish green product at 610 nm. In indirect spectrophotometry (method B), MCP is treated with a fixed concentration of KMnO₄ in an H₂SO₄ medium, and after a specified time, the unreacted KMnO4 is measured at 545 nm. Under optimum assay conditions, Beer’s law is obeyed over the ranges of 0.75–12.0 and 2.5–30.0 g/ml for methods A and B, respectively. Molar absorptivity values are calculated to be 2.33∙10⁴ and 2.66∙10⁴ l/mol cm for methods A and B, respectively, and corresponding Sandell’s sensitivity values are 0.015 and 0.013 g/cm². Limits of detection (LOD) and quantification (LOQ) are also reported. The applicability of the developed methods was demonstrated by the determination of MCP in tablet and injection forms. The accuracy and reliability of the proposed methods were further ascertained by recovery studies via standard addition technique.     

Emitting Species in Chemiluminescence Reactions with Acidic Potassium Permanganate: A Re-Evaluation Based on New Spectroscopic Evidence

The reaction of acidic potassium permanganate with a wide range of compounds is known to produce a broad red emission, and there is strong evidence for an excited manganese(II) emitting species. Nevertheless, numerous researchers have proposed other emitters for reactions with acidic potassium permanganate, particularly for systems where fluorescent compounds were present, either as enhancers or reaction products. We have examined many reactions of this type and found that, in most cases, the same red emission was produced. There were, however, some exceptions, including the oxidation of dihydralazine, certain thiols and sulphite (each in the presence of an enhancer).     

Modified Spectrophotometric Method for the Determination of Some Important Antibiotics Through Charge - Transfere Complexation Reaction with Chloranil

Abstract

A new modified Spectrophotometric procedures are presented for the determination of three pharmaceutical antibiotic compounds through charge-transfere complexation reaction with chloranil. The complex shows an absorption mAxima at 550 nm, having a molar absorptivity coefficient of 5.55×10³,7.81×10³ and 1.38×10⁴ 1. mol^?1cm^?1 for ampicillin, amoxycillin and neomycin, respectively. Optimization of the reaction conditions has been investigated Obediance to Beer's law (40μg/ml) permitted the assay of thes drugs in its dosage forms A variety of pharmaceutical dosage forms containing ampicillin, amoxycillin and neomycin are successfully analysed by the proposed procedure.     

A high efficiency label-free photonic biosensor based on vertically stacked ring resonators

In this paper we propose an optical biosensor based on two vertically stacked Silicon on Insulator (SOI) micro-ring resonators interacting with a microfluidic ring channel. This device behaves as a resonant optical coupler and it is very sensitive to the variation of the coupling coefficient between the two vertically stacked ring resonators. A ring microfluidic channel is proposed in the coupling region between the two vertically stacked ring resonators. The inner walls of the channel are funzionalized in order to the trap a specific biological species. Assuming a biotin-streptavidin system, the straptividin trapping gives rise to a change of the biological thickness of about 3 nm. This thickness increase of the deposited layer leads to a consequent change in the coupling strength between the two rings. These theoretical predictions have been validated by using both 3D Finite-Difference Time-Domain (FDTD) and 3D full-vectorial Finite Element Method (FEM) approaches. Moreover, by appropriately choosing the design parameters of the micro-resonant structure, we evaluate a sensitivity of the spectral response to the streptavidin adlayer variation of about 20% nm^?1 for TE polarization and 34% nm^?1 for TM polarization, which represents an important achievement to obtain selective SOI bio-sensors with ultra-high resolution.     

Photoemission electron microscopy of arrays of submicron nickel rods in a silicon dioxide matrix

Arrays of Ni rods (～500 nm diameter) formed by the ion-track technology in combination with electrochemical deposition into a SiO₂ matrix on the surface of single-crystal silicon plates have been investigated using photoemission electron microscopy with high-intensity synchrotron (undulator) radiation. An analysis of the Ni L _2,3 X-ray absorption near-edge structure (XANES) spectra has demonstrated that rod-like structures in pores and connecting bridges between the rods are formed by a metallic nickel phase, which is stable to oxidation by atmospheric oxygen. No formation of intermediate compound phases (nickel silicides and oxides) is observed at the Ni/SiO₂ heterojunction, whereas oxidized nickel(II) species are identified on the surface of the SiO₂ matrix, which presumably can be attributed to nickel silicate and hydroxide compounds formed upon nickel(II) chemisorption in electrochemical deposition electrolytes.