Determination of menadione sodium bisulfite in pharmaceutical preparations by flow-injection on-line photochemical spectrofluorometry.

A flow-injection on-line photochemical spectrofluorometry (FI-PF) was developed for the determination of menadione sodium bisulfite (MSB) using acetone and sodium sulfite as sensitizing reagents. An injected sample band carried by a water stream was on-line merged with a mixed NaOH, Na2SO3 and acetone solution in a "T" connector. It was then driven to pass a knotted PTFE photochemical reactor (0.5 mm i.d. x 200 cm, KR) that was freely coiled around a 6-W low-pressure mercury lamp. While passing the KR, MSB was derived into an intensively fluorescent compound that was on-line delivered into a flow-through cell and detected therein at an emission wavelength of 459 nm and an excitation wavelength of 336 nm. Under optimized conditions a detection limit of 0.38 microg l(-1) was achieved at a sampling rate of 90 h(-1). Eleven determinations of 0.5 mg l(-1) and 0.05 mg l(-1) MSB standard solution gave RSDs of 0.75% and 1.3%, respectively. The calibration curve was linear in the MSB concentration range 0.005-1.5 mg l(-1). The proposed method was successfully applied to assay the MSB content in MSB injection.     

A simple and sensitive flow-injection on-line preconcentration coupled with hydride generation atomic fluorescence spectrometry for the determination of ultra-trace lead in water, wine, and rice.

A simple and sensitive flow-injection on-line separation and preconcentration system coupled to hydride generation atomic fluorescence spectrometry (HG-AFS) was developed for ultra-trace lead determination in water, wine, and rice samples, with the salient advantages of its minimization of transition-metal interferences and tolerance to an ethanol matrix. A lead hydroxide precipitate was achieved by the on-line merging of a sample and an ammonium buffer solution and collected onto the inner walls of a knotted reactor (KR). Removal of the residual solution from KR was achieved by air flow, and dissolution of the precipitate was carried out by using 0.2 mol l(-1) HCl. With a sample consumption of 11.7 ml, an enhancement factor of 16 was obtained at a sample throughput of 30 h(-1). The limit of detection (3s) was 16 ng l(-1) and the precision (RSD) for 1.0 microg l(-1) Pb was 3.4%.     

Photochemical reactivity of sulfamethoxazole and other sulfa compounds with photodiode array detection

The photochemical activities of six sulfa compounds [sulfacetamide (CET), sulfadiazine (DIA), sulfaguanidine (GUA), sulfamerazine (MER), sulfamethoxazole (SMX), and sulfamethizole (MET)] under different experimental conditions such as photolysis time, solvent and buffer pH are investigated by photodiode array (PDA) spectrophotometry. With no photolysis, the sulfa drugs CET and DIA show no absorbance at 332 nm and the other compounds only modest absorbance. Upon photolysis for 4 min, absorbance enhancements at 332 nm of three to four times for GUA and MET and 12-15 times for SMX and MER are observed. For CET and DIA after photolysis, the (absorbance) l/mg is now approximately 0.01-0.02 units. Although two pH optima of approximately 3-4 and 7 are noted, the optimum solvent for photolysis is ethanol without pH adjustment. For flow injection (FI) with on-line photolysis and PDA detection, a mobile phase of 100% ethanol with a step flow rate from 0.1 to 1 ml/min is used providing a 4-min reaction time. The FI detection limit for SMX with photolysis at 330 nm is 1 mg/l. The relative standard deviation data (n=4) of seven individual points in a calibration curve from 5 to 150 mg/l are 0-4%. The recovery of SMX from pharmaceutical tablets is 99.7% indicating no interference from trimethoprim which is not photochemically active.     

Fluorescent quenching method for determination of trace hydrogen peroxide in rain water

A simple and sensitive fluorescent quenching method for the determination of trace hydrogen peroxide (H(2)O(2)) has been proposed to determine hydrogen peroxide in rain water sample. The method is based on the reaction of H(2)O(2) with 3,3'-diethyloxadicarbocyanine iodide (DI) to form a compound which has no fluorescence in acetate buffer solution (pH 3.09). The maximum emission wavelength of the system is located at 604 nm with excitation at 570 nm. Under the optimal conditions, the calibration graph was obtained between the quenched fluorescence intensity and hydrogen peroxide concentration in the range of 5.0 x 10(-7) to 9.0 x 10(-4) mol L(-1). The proposed method was applied to determine H(2)O(2) in rain water samples, and the result was satisfactory. The mechanism involved in the reaction was also studied.     

Electro-organic synthesis and characterization of new dihydroxybenzene dinitrile derivatives with fluorescent properties

Novel fluorescent molecules were synthesized by designing an environmentally friendly method involving the bulk electrolysis technique. This electrochemical treatment process helps protect the environment by minimizing the toxic waste component of effluent. The electrochemical oxidation of 3,6-dihydroxybenzene-1,2-dinitrile (DBD) in the presence of benzenesulfinic acids was studied in an aqueous solution (H(2)O : AN, 90 : 10), which included an acetate buffer (pH=5.0). This research utilized a variety of experimental techniques, including cyclic voltammetry, controlled-potential electrolysis as well as spectroscopic identification of compounds produced as products. In addition, our fluorescent studies offered results in line with existing findings. At the wavelength of 205 nm, DBD and compound (6) were excited and their fluorescent emissions were monitored.     

The fluorescence study of the inclusion coordinated compound of beta-cyclodextrin and p-hydroxyphenolacetamide and its analytical applications

The inclusion coordinated compound fluorescence of p-hydroxyphenolacetamide (PHPA) with beta-cyclodextrin was studied and a high sensitive analytical method to determine the content of PHPA was established based on the increased fluorescence intensity of the coordinated compounds in Britton-Robinson buffer solution (pH 7). The wavelength of the excited emission are 282 and 310 nm, respectively. The enhanced coordinated compounds fluorescence intensity is proportional to the concentration of PHPA in the range 0.030-11.0 mg/l. The relative standard deviation (R.S.D.) were within 0.66-4.2%. Correlation coefficient and inclusion binding constant Kf are obtained within 0.9950-0.9996 and 4.67 x 10(2), respectively. Meanwhile, a linear increase of the resonance light scattering (RLS) with the inclusion coordinated compounds concentration was noticed at a synchronous wavelength of 584 nm. The forming reasons of inclusion coordinated compounds were investigated. The 1:1 molar ratio composition of inclusion compound was measured with DTA and elemental analysis. The method is simple, rapid and has a good reproducibility. The method was used for determination of PHPA in an artificial sample with satisfactory results.     

流动注射在线氧化荧光法结合透析采样研究盐酸硫利达嗪与牛血清白蛋白的结合作用

利用流动注射在线氧化结合在线透析采样技术建立了荧光法测定血浆中游离盐酸硫利达嗪的新方法, 并将其应用于盐酸硫利达嗪与牛血清白蛋白作用机制的研究. 将盐酸硫利达嗪与牛血清白蛋白以不同比例混合并在37 ℃下培养, 以流动注射透析采样技术从混合液中分离出游离盐酸硫利达嗪, 在线氧化为强荧光化合物后测定其浓度; 应用Scrathard方程分析所测数据, 求得盐酸硫利达嗪和牛血清白蛋白的结合常数为1.2×104 L/mol, 结合位点数为0.98; 根据热力学参数推断, 盐酸硫利达嗪与牛血清白蛋白之间以疏水作用力为主; 进一步基于荧光猝灭现象和Fster非辐射能量转移理论, 得到盐酸硫利达嗪小分子与牛血清白蛋白之间的能量转移效率(E=0.497)和结合距离(r0=3.27 nm).     

Rapid determination of sulphonamides in milk using liquid chromatographic separation and fluorescamine derivatization.

A simple and selective method is presented for the multiple residue determination of eight sulphonamides in consumers' milk. The drugs are sulphisomidine (ID), sulphadiazine (DZ), sulphamerazine, sulphadimidine, sulphamonomethoxine, sulphamethoxazole, sulphadimethoxine and sulphaquinoxaline (SQ). The milk sample was deproteinized with the same volume of 2 M hydrochloric acid and filtered. A 1-ml volume of the filtrate was mixed with 1 ml each of 1.25 M sodium acetate solution and a buffer (pH 3.0) for derivatization with 0.6 ml of 0.02% fluorescamine solution in acetone. A high-performance liquid chromatographic analysis was carried out on a C18 column with a mobile phase of acetonitrile-2% acetic acid (3:5) at 55 degrees C using a fluorescence detector at an excitation wavelength of 405 nm and an emission wavelength of 495 nm. Average recoveries at fortification levels of 2, 5 and 10 ng/ml were 114%, 109% and 106%, respectively. Relative standard deviations were 1-4% at 10 ng/ml for ID, 5 ng/ml for DZ and SQ and 2.5 ng/ml for the other five sulphonamides. The method was applied to 25 milk samples and all appeared to be free from the drugs.     

Spectrofluorimetric study of the beta-cyclodextrin:vitamin K3 complex and determination of vitamin K3

Vitamin K(3) (menadione) is an oil-soluble vitamin and not naturally fluorescent but yields fluorescence when it is reduced. However, it is possible to yield a fluorescent derivative in the region of 407 nm in aqueous medium when complexed to beta-cyclodextrin (CD). A 1:1 stoichiometric ratio and a formation constant of 373+/-34 l mol(-1) were obtained for the binary inclusion complex between menadione and beta-CD. The measurements were performed at pH 6.2 adjusted by adding 0.1 mol l(-1) citrate buffer solution and 6.4 x 10(-3) mol l(-1) of beta-CD concentration. The calibration graph was linear over the range 0.1-2.0 mg l(-1) with a repeatability of 2.2%; the detection limit was 0.022 mg l(-1) and the limit of quantification limit was 0.073 mg l(-1). The procedure was applied to pharmaceutical formulations.     

Solid-phase reactor flow-injection on-line oxidizing spectrofluorimetry for determination and dissolution studies of folic acid

A simple, sensitive and specific flow-injection spectrofluorimetric method has been developed for the determination of folic acid in pharmaceuticals. The method is based on use of a lead dioxide solid-phase reactor for on-line oxidation of folic acid into a strongly fluorescent compound with a maximum excitation wavelength of 281 nm and an emission wavelength of 450 nm. Under optimum conditions the fluorescence intensity of oxidation product is proportional to the concentration of folic acid over the range 0.008–2.5 g mL^–1. The detection limit is 0.0001 g mL^–1, the relative standard deviation is 0.85% for 11 replicate determinations of 0.05 g mL^–1 folic acid, and the sample throughput is 20 h^–1. In combination with an on-line filter and dilution, an automated drug-dissolution system was established. The proposed method has been successfully applied to the determination of folic acid in pharmaceutical preparations and dissolution testing.     

8-Phenyl-(4-oxy-acetic acid N-hydroxysuccinimidyl ester)-4,4-difluoro-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene as a new highly fluorescent-derivatizing reagent for aliphatic amines in disease-related samples with high-performance liquid chromatography

A novel fluorescent-activated ester, 8-phenyl-(4-oxy-acetic acid N-hydroxysuccinimidyl ester)-4,4-difluoro-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene (TMPAB-OSu) has been designed and synthesized for amine labeling in HPLC. Being used 11 aliphatic amines as the models, the derivatization conditions were optimized. In 0.2 mol/l borate buffer (pH 8.8), amines reacted with TMPAB-OSu at 30 °C to form the derivatives in 10 min. The fluorescent quantum yield of TMPAB-OSu and its amine derivatives are high even compared with fluorescein. The separation of these amine derivatives was achieved with a C₈ column and gradient elution by using 0.1 mol/l sodium acetate buffer (pH 5.0) and methanol. With fluorescence detection at an emission wavelength of 509 nm and an excitation wavelength of 497 nm, the detection limits of aliphatic amines were 2–18 fmol, at a signal-to-noise ratio of 3:1. The proposed TMPAB-OSu-based HPLC method has been applied to the analysis of urine samples of health, hepatic and renal patients and lake water. Recoveries from different matrices are from 96 to 104%, depending on the sample investigated.     

Determination of Thiamethoxam residues in honeybees by high performance liquid chromatography with an electrochemical detector and post-column photochemical reactor

A method for the determination of Thiamethoxam in bee samples was set up by means of high performance liquid chromatography with an electrochemical detector and post-column photochemical reactor (HPLC-h nu-ED). Analytical method was based on a rapid sample extraction procedure with acetone, followed by chromatographic separation into a C18-RP column isocratically operated by 60 mM phosphate buffer/acetonitrile (75/25) mobile phase at pH 2.7. A photochemical reactor was used as a tool to verify and eventually quantify the presence of Thiamethoxam in the samples by distinguishing it from interference contribution. Detection was performed with a potential of 880 mV after a photoactivation with a 254 nm light. The least detectable dose was 0.002 mg kg(-1). Recovery rates ranged between 59.88 and 71.62%.     

Automated sequential injection fluorimetric determination and dissolution studies of Ergotamine Tartrate in pharmaceuticals

A fully automated flow system for drug-dissolution studies based on the sequential injection analysis (SIA) was described and used for monitoring dissolution profiles of Ergotamine Tartrate (ET) in pharmaceutical formulations. 50 μl of dissolution medium was taken for each measurement at a flow rate of 40 μl s⁻¹ and detected by fluorescence detector using λ_ex=236 nm (λ_em≥390 nm). The calibration curve was linear over the range 0.03–0.61 mg l⁻¹ of ET (sufficient for the dissolution tests). Equation of the calibration curve was calculated giving the following values: F=117.7 c+0.80 (n=6); r=0.9998. Detection limit was 0.01 mg l⁻¹ of ET. The R.S.D. is less than 0.54 and 0.86% (n=10) when determining 0.61 and 0.03 mg l⁻¹ of ET in standard solution, respectively. The dissolution test of Bellaspon tablets (0.3 mg of ET in 1 tablet) was programmed for 20 min, with a continuous sampling rate of 120 h⁻¹ under conditions required by BP 1993.     

Flow-injection system for automated dissolution testing of isoniazid tablets with chemiluminescence detection

A simple and sensitive flow-injection chemiluminescence (CL) system for automated dissolution testing is described and evaluated for monitoring of dissolution profiles of isoniazid tablets. The undissolved suspended particles in the dissolved solution were eliminated via on-line filter. The novel CL system of KIO(4)-isoniazid was also investigated. The sampling frequency of the system was 120 h(-1). The dissolution profiles of isoniazid fast-release tablets from three sources were determined, which demonstrates the stability, great sensitivity, large dynamic measuring range and robustness of the system.     

ESIPT inspired fluorescent 2-(4-benzo[d]oxazol-2-yl)naphtho[1,2-d]oxazol-2-yl)phenol: experimental and DFT based approach to photophysical properties

ESIPT inspired fluorescent 2-(4-benzo[d]oxazol-2-yl)naphtho[1,2-d]oxazol-2-yl)phenol was synthesized from 1-amino-3-(1,3-benzoxazol-2-yl)naphthalen-2-ol. Photophysical behavior of the synthesized compound was studied using UV–visible and fluorescence spectroscopy in polar and non-polar solvents. The synthesized naphthoxazolyl benzoxazole is fluorescent and very sensitive to the micro-environment. It shows a single absorption and dual emission in non-polar solvents with large Stokes shift originating from Excited State Intramolecular Proton Transfer while in polar solvents only a single short wavelength emission is observed. Experimental absorption and emission wavelengths are in good agreement with those predicted using the Time-Dependent Density Functional Theory (TD-DFT) [B3LYP/6-31G(d)]. The largest wavelength difference between the experimental and computed absorption maxima was 16 nm (acetonitrile) and 7 nm (ethyl acetate, THF, and 1,4-dioxane) in the short and long wavelength regions, respectively. A largest difference of 25 nm was observed for the short wavelength emission in DMF and 22 nm for the longer wavelength emission in chloroform.     

Repetitive determination of calcium ion and regeneration of a chromogenic reagent using chlorophosphonazo III and an ion exchanger in a circulatory flow injection system.

The spectrophotometric determination of Ca2+ with chlorophosphonazo III (CPN) has been carried out by a circulatory flow injection (FI) method. A cation-exchange mini-column for the on-line regeneration of the main reagent was incorporated in this FT system, allowing a repetitive determination of Ca2+. A solution of 4.0 x 10(-5) M CPN in a 0.05 M acetate buffer (pH 5.0) in a single reservoir (50 ml) was continuously circulated at a constant flow rate of 1.5 ml min(-1). Into the stream, an aliquot (20 microl) of a sample containing Ca2+ was quickly injected by means of a 6-way valve. The complex formed was monitored spectrophotometrically at 670 nm in the flow system. Then, the stream passed through a cation-exchange column, which was introduced after the flow-through cell. A successful ligand-exchange reaction of Ca2+ between the CPN reagent and a cation exchanger, as well as a simultaneous regeneration of the free reagent took place. The stream then returned to the reservoir. The regeneration and recycling of the CPN reagent allowed as many as 300 repetitive determinations of 2.5 mg l(-1) Ca2+ solutions with the same 50 ml circulating solution.     

毛细管区带电泳法快速测定复方布洛芬片的有效成分

 研究了用毛细管区带电泳法快速测定复方布洛芬片中布洛芬和伪麻黄碱含量的方法。在０．０２５ｍｏｌ／Ｌ的磷酸盐缓冲液（ｐＨ８．１）中，上述两组分可在３ｍｉｎ内得以完全分离，用紫外检测器在２１０ｎｍ处检测，并以外标法定量。１１次测定含有９．５ｍｇ／Ｌ盐酸伪麻黄碱和６６．７ｍｇ／Ｌ布洛芬的试样溶液，相对标准偏差为２．９％（伪麻黄碱）和１．９％（布洛芬），回收率为１０３．１％（伪麻黄碱）和９７．６％（布洛芬）。应用毛细管区带电泳法测定复方布洛芬片剂的含量，所得结果与ＨＰＬＣ法一致。     

流动注射-氢化物发生-原子荧光光谱法测定天然水中痕量镉

基于编结反应器,提出了流动注射-氢化物发生-原子荧光光谱法测定水中痕量镉含量的方法。样品与氨水-氯化铵缓冲溶液在线混合,产生的沉淀收集到编结反应器内壁,引入空气除去编结反应器内残留的溶液,泵入盐酸(3+97)溶液溶解沉淀,与硼氢化钾合并后用原子荧光光谱仪测定。在优化的试验条件下,当样品消耗15.6mL时,富集倍数为14倍,方法检出限(3S/N)为2.9ng.L-1,相对标准偏差(n=11)为3.4%。方法用于国家标准物质和天然水样中痕量镉的测定,测定值与标准值相符,天然水样的回收率在91.5%～107.5%之间。     

Simultaneous determination of aceclofenac, paracetamol, and chlorzoxazone by RP-HPLC in pharmaceutical dosage form

A simple, rapid, and precise reversed-phase liquid chromatographic method is developed for simultaneous determination of paracetamol, aceclofenac, and chlorzoxazone in their ternary mixtures of commercial pharmaceutical preparation. This method uses a Zorbax SB C18, 250 x 4.6 mm, 5 microm analytical column. Mobile phase is acetonitrile and buffer (40:60, v/v), buffer containing 50 mM orthophosporic acid; pH of the buffer is adjusted to 6 with 10% w/v sodium hydroxide solution. The instrumental settings are at a flow rate of 1 mL/min; the column temperature is 25 degrees C, and detector wavelength is 270 nm. The sample concentrations are measured on weight basis to avoid the internal standard. The method is validated and shown to be linear. The correlation coefficients for paracetamol, aceclofenac, and chlorzoxazone are 0.9981, 0.9990, and 0.9986, respectively. The recovery values for paracetamol, aceclofenac, and chlorzoxazone ranged from 100.7-101.4%, 100.4-101.0%, and 100.5-101.3%, respectively. The relative standard deviation for six replicates is always less than 2%. This HPLC method is successfully applied to the simultaneous quantitative analysis of the title drugs in tablets and can be applied for assay and dissolution test of tablets for the estimation of paracetamol, aceclofenac, and chlorozoxazone in their commercial samples.     

毛细管区带电泳法快速测定复方布洛芬片的有效成分

研究了用毛细管区带电泳法快速测定复方布洛芬片中布洛芬和伪麻黄碱含量的方法。在０．０２５ｍｏｌ／Ｌ的磷酸盐缓冲液（ｐＨ８．１）中，上述两组分可在３ｍｉｎ内得以完全分离，用紫外检测器在２１０ｎｍ处检测，并以外标法定量。１１次测定含有９．５ｍｇ／Ｌ盐酸伪麻黄碱和６６．７ｍｇ／Ｌ布洛芬的试样溶液，相对标准偏差为２．９％（伪麻黄碱）和１．９％（布洛芬），回收率为１０３．１％（伪麻黄碱）和９７．６％（布洛芬）。应用毛细管区带电泳法测定复方布洛芬片剂的含量，所得结果与ＨＰＬＣ法一致。