Spectrophotometric Determination of Certain Local Anaesthetics in Pharmaceutical Preparations

Abstract

A direct colorimetric method was described for the rapid, sensitive and accurate determination of dibucaine, lidocaine, bupivacaine, procaine and tetracaine in pharmaceutical preparations. The method involves the use of haematoxylin reagent in the presence of boric acid to give a reddish-violet chromogen (λ_max = 555 nm). Beer's law was obeyed in the range from 2–60 μg/ml. No interference was observed from the commonly present additives or agents in pharmaceutical formulations.     

探究影响碳酸氢钠晶体析出的最佳实验条件

采用正交实验法探究析出“NaHCO3晶体”的外部因素“饱和碳酸钠溶液的体积”“实验温度”“试管内径”“二氧化碳的流速”,得出在课堂上析出NaHCO3晶体的最佳实验条件,实验耗时约5 min就能产生明显的白色浑浊。     

Development and Validation of a LC Method for the Determination of Pramipexole Using an Experimental Design

A rapid and sensitive RP-HPLC method with UV detection for routine control of pramipexole in tablets was developed. Chromatography was performed with mobile phase containing a mixture of acetonitrile/phosphate buffer (60/40; v/v) with a flow rate of 0.8 mL min⁻¹. Quantitation was accomplished with the internal standard method; the procedure was validated by linearity (correlation coefficient = 0.99892), accuracy, robustness and intermediate precision. Limit of quantitation and limit of detection were found to be 4.5 μg and 1.4 μg respectively, which indicates the method is highly sensitive. Experimental design was used during validation to calculate method robustness and intermediate precision, for robustness test three factors were considered; percentage v/v of acetonitrile, flow rate and pH; an increase in the flow rate results in a decrease of concentration found of the drug, while the percentage of organic modifier and temperature have no important effect on the response. For intermediate precision measure the considered variables were: analyst, equipment, days and obtained RSD value (0.56%, n=24) which indicated a good precision of the analytical method. The method was found to be applicable for determination of the drug in tablet formulations and the results of the developed method were compared with those of the UV spectrophotometric method to access the active pramipexole content. Revised: 13 March and 25 April 2006     

Determination of Flavonoid Markers in Honey with SPE and LC using Experimental Design

Determination of flavonoid markers quercetin, hesperetin, and chrysin, found in north Iranian citrus honey samples, was carried out by solid phase extraction (SPE) and isocratic liquid chromatographic separation using central composite design. Optimum conditions for SPE were achieved using 10 mL methanol/water (13:87, v/v, pH = 7) as the washing solvent and 4 mL methanol for elution. Good clean-up and high recovery >90% were observed for all analytes. The use of water/ACN/THF/AcOH (54:36:5:5, v/v) was found to serve as the optimum mobile phase composition and allowed for the separation of analytes from endogenous compounds present in honey. SPE parameters, such as maximum loading capacity and breakthrough volume, were also determined for each analyte. Limit of detection, linear range, recovery, repeatability of retention times, and peak heights were 3.11 × 10⁻⁸–4.44 × 10⁻⁸ g g⁻¹, 0.50–50.0 μg mL⁻¹ (R ² > 0.99), 90.7–96.9%, 3.0–3.6%, and 1.0–2.6%, respectively. Precision of the overall analytical procedure, estimated by five replicate measurements for quercetin, hesperetin and chrysin in citrus honey, as well as the relative standard deviations were 4.3%, 3.8%, and 5.5%, respectively.

     

Determination of Flavonoid Markers in Honey with SPE and LC using Experimental Design

Determination of flavonoid markers quercetin, hesperetin, and chrysin, found in north Iranian citrus honey samples, was carried out by solid phase extraction (SPE) and isocratic liquid chromatographic separation using central composite design. Optimum conditions for SPE were achieved using 10 mL methanol/water (13:87, v/v, pH = 7) as the washing solvent and 4 mL methanol for elution. Good clean-up and high recovery >90% were observed for all analytes. The use of water/ACN/THF/AcOH (54:36:5:5, v/v) was found to serve as the optimum mobile phase composition and allowed for the separation of analytes from endogenous compounds present in honey. SPE parameters, such as maximum loading capacity and breakthrough volume, were also determined for each analyte. Limit of detection, linear range, recovery, repeatability of retention times, and peak heights were 3.11 × 10^?8–4.44 × 10^?8 g g^?1, 0.50–50.0 μg mL^?1 (R ² > 0.99), 90.7–96.9%, 3.0–3.6%, and 1.0–2.6%, respectively. Precision of the overall analytical procedure, estimated by five replicate measurements for quercetin, hesperetin and chrysin in citrus honey, as well as the relative standard deviations were 4.3%, 3.8%, and 5.5%, respectively.     

LC Method for the Determination of the Stability of Levetiracetam Drug Substance under Stressing Conditions

Levetiracetam is used in combination with other medications to treat certain types of seizures in people with epilepsy. Levetiracetam is in a class of medications called anticonvulsants and it works by decreasing abnormal excitement in the brain. A chromatographic separation was achieved on a YMC pack ODS AQ, 250 mm × 4.6 mm, 5 μm column using diluted phosphoric acid and acetonitrile in the ratio 85:15 v/v. Forced degradation studies were performed on the levetiracetam drug substance. The drug substance was degraded to Imp-B during acid and base hydrolysis. When the stress samples were assayed, the mass balance was matching. The sample solution and mobile phase was found to be stable up to 48 h at 25 °C. The developed method was validated with respect to linearity, accuracy, precision and robustness.     

Optimization of Micellar LC Conditions for the Flavonoid Separation

The chromatographic conditions for the separation of a complex set of flavonoids (aglycones and glycosides) by micellar liquid chromatography with spectrophotometric detection were optimized. A good separation for all analytes was obtained and satisfactory peak shapes were achieved by isocratic elution with Ultrasphere ODS column (250 mm × 4.6 mm, 5 μm). The optimal mobile phase range for flavonoids separation is: SDS concentration between 0.014 and 0.018 mol L^?1 and 1-propanol volume fraction between 2.2 and 4.5% (v/v) in a diluted (1:5) phosphate buffer solution pH 6.86. The flavonoids (robinin, rutin, hyperoside, quercitrin, liquroside, luteolin-7O-glucoside, apigenin-7O-glucoside, isosalipurposide, myricetin, fisetin, luteolin, apigenin, quercetin and caempferol) were successfully separated within 40 min with isocratic elution. The developed method is an alternative to reversed-phase LC in the assay of flavonoids in plants, plant extracts and plant extract containing drugs.     

液-液-液微萃取-高效液相色谱法测定人血浆中的局部麻醉剂

建立了液-液-液微萃取与高效液相色谱联用技术同时测定人血浆中3种局部麻醉剂利多卡因、布比卡因和丁卡因的方法。考察了萃取时间、料液pH值和搅拌速度的影响,取佳萃取条件为萃取溶剂为200μL苯,接受相为1.0μL 0.2 mol/L HC l,搅拌速度为250 r/m in,萃取时间为45 m in。在该条件下,获得了高的富集因子(大于305倍)。方法的线性范围为:利多卡因和布比卡因0.025~5 mg/L,丁卡因0.05~5 mg/L,相关系数大于0.996;检出限依次为0.005、0.015和0.025 mg/L;相对标准偏差小于5%。该方法能有效地去除血浆中复杂基体的干扰,萃取效率高,有机溶剂消耗少,是一种有效、灵敏的同时测定血浆中利多卡因、布比卡因和丁卡因的方法。     

LC-DAD Determination of Calcium Channel Blockers by Using an Experimental Design Approach

A high-performance liquid chromatographic method with diode array detection has been developed for the determination of five 1,4-dihydropyridines: amlodipine, nitrendipine, felodipine, lacidipine and lercanidipine. A fractional design and a central composite design were used. The factors considered in the optimisation process were: percentage of organic modifier, pH of the aqueous buffer, buffer concentration and temperature. The chromatographic separation was performed using a Supelcosil LC-ABZ+Plus C18 column. An optimised mobile phase of acetonitrile-water (70:30, v/v), containing 10 mM CH₃COOH-CH₃COONa pH 5 at a flow rate of 1 mL min^?1 was used. The temperature was set at 30 ± 2 °C. The photometic detection was carried out at 237 nm. The method was applied to the determination of these compounds at μg mL^?1 concentration levels, obtaining intraday repeatabilities values lower than 5% in terms of relative standard deviations, accuracies higher than 98% and detection limits ranged from 0.03 (felodipine) to 0.35 μg mL^?1 (lacidipine). The chromatographic method allowed the analysis of the drugs in their pharmaceutical formulations with a total elution time of 12 min.     

An Experimental Design for Simultaneous Determination of Carbendazim and Fenamiphos by Electrochemical Method

This study is aimed to develop an electroanalytical methodology using a boron‐doped diamond electrode (BDD) associated with experimental design in order to determine simultaneously and selectively carbendazin (CBZ) and fenamiphos (FNP) pesticides. In previous studies oxidation peaks were observed at 1.10 V (CBZ) and 1.20 V (FNP), respectively, with characteristics of irreversible processes controlled by diffusion of species (in pH 2.0 (CBZ) and pH 3.5 (FNP)) using a BR buffer 0.1 mol L^?1 as support electrolyte. The differences between the potentials for both pesticides, (about 100 mV) indicate the possibility of selective determination of FNP and CBZ. However, employing an equimolar mixture of analytes, the peaks overlap to form a single oxidation peak. Thus, we used a 3⁴ full factorial design with four parameters to be analyzed in three levels, in order to obtain the optimized parameters for the separation of the peaks. The best separation conditions were pH 5.0, square wave frequency of 300 s^?1, pulse amplitude of 10 mV and scan increment of 2 mV. These parameters were used to obtain the calibration curves of CBZ and FNP. For CBZ the analytical curve was obtained in the concentration range of 4.95×10^?6 to 6.90×10^?5 mol L^?1 with good sensitivity and linearity (0.175 A/mol L^?1 and 0.999, respectively). The limits of detection (LOD) and quantification (LOQ) were 1.6×10^?6 mol L^?1 and 5.5×10^?6 mol L^?1, respectively. For FNP the linear concentration interval was 4.95×10^?6 to 3.67×10^?5 mol L^?1, with a sensitivity of 0,207 A/mol L^?1 and linearity of 0.996. The LOD and LOQ were 4.1×10^?6 mol L^?1 and 13.7×10^?6 mol L^?1, respectively. Using these experimental conditions it was possible to separate the oxidation peaks of CBZ (E_p=1.08 V) and FNP (E_p=1.23 V). The electroanlytical method was applied in lemon juice samples. The recovery values were 110.0 % and 92.5 % for CBZ and FNP, respectively. The results showed that the developed method is suitable for application in foodstuff samples.     

T_(31)环氧树脂固化过程研究——1.动态扭振法确定最佳固化条件

在新设计制造的HLX-1型树脂固化仪上对T_(31)-环氧树脂E51进行了最佳配方和最佳条件的选择。T_(31)含量为20phr的环氧树脂体系,最佳固化温度为333K,固化反应活化能E=52.7KJ/mol。用非平衡态涨落理论也成功地预估了T_(31)-环氧树脂体系的固化行为。     

Applying the Taguchi Robust Design to Optimization of the Experimental Conditions for Synthesis of Lead Chromate Nanorods

Orthogonal array design was employed as statistical method for controllable, simple, and fast synthesis of highly uniform PbCrO₄ nanorods by precipitation method. Lead chromate nanorods were synthesized by addition of lead solution to chromate reagent. Effect of reaction conditions on the width of lead chromate rods were quantitavely evaluated by analysis of variance. Finally, optimum conditions for synthesis of lead chromate nanorods by this simple and fast method were proposed. The results of analysis of variance showed that 0.001 mol/L lead and chromate ion concentrations are optimum conditions for producing lead chromate nanorods with 87 ± 15 nm width.     

一种测定MDR肿瘤细胞内外阿霉素浓度的方法

研究提出K562／A细胞内外阿霉素浓度的反相高效液相色谱-荧光测定法．细胞内阿霉素浓度测定采用Lichrospher C18色谱柱,甲醇-0．01％醋酸(50：50,V／V)流动相,流速1．0mL／min,柱温35℃;细胞外阿霉素浓度测定采用Lichrospher C18色谱柱,甲醇-0．01％醋酸(55：45,V/V)流动相,流速0．8mL／min,柱温35℃．荧光检测器波长λex=495nm,λem=560nm,均以盐酸柔红霉素为内标．研究结果表明,该方法简单、准确、线性范围宽、检测限低,精确度和回收率良好,可用于多药耐药肿瘤细胞内外阿霉素浓度的动态变化规律研究．     

正交试验法优选石墨炉测定大米中镉的实验条件

利用L16(45)正交试验设计,考察了石墨炉原子吸收法测定大米中镉的灰化温度、灰化时间、原子化温度、原子化时间.确定了最佳灰化温度为450℃、灰化时间为15s、原子化温度为1750℃、原子化时间为4s等仪器的最佳参数.     

An LC Method for the Determination of Bupropion and Its Main Metabolite, Hydroxybupropion in Human Plasma

A new LC method has been developed and validated for the direct determination of bupropion and its main metabolite, hydroxybupropion in human plasma. Plasma samples were analyzed after a simple, one step protein precipitation with trichloroacetic acid using a C₈ column and mobile phase, consisting of methanol/acetonitrile/phosphate buffer (10 mM, pH 3.0) (40:10:50, v/v/v) and 20 mM 1-heptane sulfonic acid sodium salt with carbamazepine as the internal standard. UV detection was performed at 214 and 254 nm. The method was validated over the concentration range of 60–2,400 and 150–4,700 ng mL^?1 for bupropion and hydroxybupropion, respectively. The intra- and inter-day assay variability was less than 15% for the two analytes. Limit of detection values were 24.8 and 63.4 ng mL^?1 for bupropion and hydroxybupropion, respectively. The method developed was applied to quantification of bupropion and hydroxybupropion in human plasma.     

An LC Method for the Determination of Bupropion and Its Main Metabolite,Hydroxybupropion in Human Plasma

A new LC method has been developed and validated for the direct determination of bupropion and its main metabolite, hydroxybupropion in human plasma. Plasma samples were analyzed after a simple, one step protein precipitation with trichloroacetic acid using a C₈ column and mobile phase, consisting of methanol/acetonitrile/phosphate buffer (10 mM, pH 3.0) (40:10:50, v/v/v) and 20 mM 1-heptane sulfonic acid sodium salt with carbamazepine as the internal standard. UV detection was performed at 214 and 254 nm. The method was validated over the concentration range of 60–2,400 and 150–4,700 ng mL⁻¹ for bupropion and hydroxybupropion, respectively. The intra- and inter-day assay variability was less than 15% for the two analytes. Limit of detection values were 24.8 and 63.4 ng mL⁻¹ for bupropion and hydroxybupropion, respectively. The method developed was applied to quantification of bupropion and hydroxybupropion in human plasma.

     

An LC Ion-Pairing Method for the Determination of Fe(II) in Ferrous Bisglycinate Pharmaceutical Formulation

A reversed-phase ion-pairing liquid chromatographic method was developed and validated for the assay of Fe(II) in ferrous bisglycinate (Fe-bis-gly) capsules using 4-(2-pyridylazo) resorcinol reagent. The analysis was carried out using a Gemini RP-18 (150 mm × 4.6 mm I.D., particle size 5 μm) analytical column; the mobile phase consisted of a mixture of acetonitrile–water (28:72 v/v) containing 1 mM tetrabutylammonium hydrogensulfate and 1% phosphate buffer (pH 8.0). The flow rate was 1.0 mL min⁻¹ and the detection was achieved with a photodiode array (PDA) detector at 706 nm. The specificity of the method was proved using stress conditions and evaluated using a PDA detector. The data validation showed that the method is specific, fast, accurate, and reproducible for the determination of Fe-bis-gly in dosage form. The response was linear over a range of 1.0–2.6 μg mL⁻¹ (r = 0.9999). The accuracy of the method ranged from 98.02 to 102.75%. The RSD values for intra- and inter-day precision studies were below 1.3 and 1.1%, respectively. There was no interference of the excipients on the determination of the active pharmaceutical ingredient.