Simultaneous determination of glucose, 1,5-anhydro-d-glucitol and related sugar alcohols in serum by high-performance liquid chromatography with benzoic acid derivatization

A new, simple and sensitive pre-column high-performance chromatographic method for the determination of diabetes marker d-glucose, 1,5-anhydro-d-glucitol and related compounds is reported. Sugars (d-glucose, d-galactose, d-mannose, sucrose and arabinose) were derivatized with benzoic acid (BA) at 80 degrees C for 60 min. l-Fucose, fructose, d-lactose, l-rhamnose, arabinose and ascorbic acid were not reacted. Sugar alcohols (xylitol, erythritol, mannitol, sorbitol myo-inositol) were also derivatized with BA at 80 degrees C for 60 min. The fluorescence derivatives were separated on a TSK amide 80 column (4.6 mm i.d. x 250 mm, 5 microm) with acetonitrile-50 mm acetate buffer (pH 5.6; 4:96, v/v) as the mobile phase. The detection wavelength of beizoic acid derivatives was lambda(ex) 275 nm and lambda(em) 315 nm. The detection limits of sugars were 10-80 microg/mL. The calibration graphs were linear up to 10 mg/mL. The relative standard deviations of 500 microg/mL sugars were 7.0-7.3%. The proposed method was compared with the enzymatic photometric glucose analysis method (Glucose B-Test II Wako). The correlation coefficient was 0.83 (n = 20) and y = 0.82x + 5.91, where y and x are concentrations in microg/mL obtained by the proposed pre-column HPLC and enzyme-photometric method, respectively. The detection limits of sugar alcohols were 100-1000 ng/mL. The calibration graphs were linear to 50 microg/mL and relative standard deviations of 10 microg/mL were 7.2-8.2%. The 1,5-AG data by the proposed method was also compared with the enzymatic photometric 1,5-AG analysis method (Rana AG 1,5-AG determination kit, Nihon Kayaku) and good correlation (r = 0.91, n = 20) was also obtained. The proposed method was applied to the simultaneous determination of d-glucose, 1,5-AG and related sugar alcohols in serum from healthy males.     

流动注射化学发光法测定安痛定注射液中的氨基比林

在甲醛存在下 ,高锰酸钾与氨基比林能够发生化学发光反应 ,产生很强的化学发光 ,据此采用流动注射技术建立了一种测定氨基比林的化学发光分析法。方法的检出限为 3 .0× 10 -8g/mL ,相对标准偏差为 1.3 % (4 .0× 10 -6g/mL氨基比林 ,n =11) ,线性范围为 1.0× 10 -7～ 8.0× 10 -5g/mL氨基比林。该法已用于安痛定注射液中氨基比林含量的测定。     

Kinetic spectrophotometric determination of ethamsylate in dosage forms

A simple and sensitive kinetic method has been developed for the determination of ethamsylate (ESL) in its pharmaceutical preparations. The method is based upon oxidation of ESL with 3-methyl-2-benzothiazolinone hydrazone hydrochloride in presence of cerium (IV) ammonium sulfate at room temperature for 20 min. The absorbance of the reaction product is measured at 514 nm. The absorbance-concentration plot was rectilinear over the range of 4-30 microg/mL (r = 0.9999). The lower detection limit was 0.267 microl/mL (9.110 x 10(-6) M) and the lower quantitation limit was 0.808 microg/mL. The different experimental parameters affecting the development and stability of the reaction product were studied and optimized. The proposed method was applied to the determination of ESL in formulations, and the results obtained were in good agreement with those obtained using a reference method. The proposed method was also used for the in vitro detection of ESL in spiked human plasma at its therapeutic concentration level.     

基于碳纳米管修饰电极的甲醛生物传感器

利用甲醛脱氢酶和羧基化多壁碳纳米管修饰的丝网印刷电极,制备了基于还原型辅酶Ⅰ检测的甲醛生物传感器,并优化了传感器的检测条件.结果表明,此传感器对甲醛有较好的电催化氧化作用,显著降低了甲醛的氧化峰电位.在0.001～11nmol/L范围内,响应电流与甲醛的浓度线性相关,其线性回归方程为z(μA)=0.944c(mmol/L,) +0.0623,相关系数为0.9934,响应时间约为20 s,检出限为0.2 μmol/L( S/ N=3).     

Flow-injection chemiluminescence determination of formaldehyde with a bromate-rhodamine 6G system.

In this paper, a novel flow-injection chemiluminescence (CL) system for the determination of formaldehyde is described. It is based on a strong enhance effect of formaldehyde on the weak CL emission of the reaction between potassium bromate and rhodamine 6G in a sulfuric acid medium. A possible mechanism for this CL reaction is proposed. A CL calibration graph was linear in the range of 0.8 - 200 microg l(-1) and the detection limit was 0.3 microg l(-1) (3sigma). The relative standard deviation was less than 3% for 10 microg l(-1) formaldehyde (n = 11). The method has been applied to determine formaldehyde in the air samples.     

Separation of purine and pyrimidine bases by ion chromatography with direct conductivity detection

A simple, rapid and accurate method for the simultaneous determination of four purine and pyrimidine bases (cytosine, 5-methylcytosine, adenine and N6-methyladenine) has been developed. The quantitative determination of these bases was accomplished by ion chromatography (IC) with direct conductivity detection (CD) based on their ionization in acidic medium without chemical suppression. The recovery of cytosine, 5-methylcytosine, and adenine in calf thymus DNA was more than 98% (n=3) and the relative standard deviation (RSD, n=5) less than 2.4%. In a single chromatographic run, the four bases could be separated and determined in less than 10 min. The detection limits were found to be 0.05 microg/mL for cytosine, 0.08 microg/mL for 5-methylcytosine, 0.07 microg/mL for adenine, and 0.07 microg/mL for N6-methyladenine. Linear ranges were 0.2-95.1 microg/mL for cytosine (r2=0.9996), 0.3-196.6 microg/mL for 5-methylcytosine (r2=0.9994), 0.3-105.5 microg/mL for adenine (r2=0.9998), and 0.3-159.1 microg/mL for N6-methyladenine (r2=0.9999). With the proposed method, purine and pyrimidine bases could be successfully detected in calf thymus DNA. We also determined these bases in calf thymus DNA using RP-HPLC. Compared to RP-HPLC, the IC method offers advantages such as high selectivity and simple mobile phase.     

Development and validation of a high performance liquid chromatography-diode array detection method for the determination of aging markers in tequila

A solid-phase extraction procedure followed by analysis by high performance liquid chromatography (HPLC) with UV-vis photodiode array detection (DAD) is proposed to simultaneously determine 11 aging markers in tequila. The method showed good intraday (n=5) and interday (n=3) precision, RSD<1.6% in both cases, for each of the identified compounds. The calibration curves were linear at the tested ranges (R(2)>0.999). Good recoveries (84.2-108.5%) were obtained for 10 of the 11 compounds studied; and the LOD and LOQ ranged from 0.62 to 4.09 microg/mL and 1.9-12.4 microg/mL, respectively. The proposed methodology was applied to a set of 15 authentic tequila samples grouped by aging state (blanco, reposado and a?ejo). An ANOVA analysis combined with discriminant analysis with stepwise backward variable selection was used to differentiate between the various aging groups based on their oak related compounds content.     

Determination of formaldehyde in foodstuffs by flow injection spectrophotometry using phloroglucinol as chromogenic agent

A spectrophotometric method for the determination of formaldehyde in foodstuffs was described by using phloroglucinol as the chromogenic agent. The reaction between formaldehyde and phloroglucinol could occur rapidly at room temperature under mild conditions. The spectrophotometric measurements were conducted at 474nm of an unstable intermediate orange product of the reaction, which greatly increased the sample throughput. Flow injection technique was used to control the merging and reaction timing of the reagents and sample. A detection limit (3sigma) of 0.023microg ml(-1) was achieved. The relative standard deviation was 0.29% for the determination of 7microg ml(-1) formaldehyde (n=11). The proposed method was applied to the analyses of formaldehyde in several preserved foodstuffs and the results were in good agreement with those obtained by a standard method.     

Preconcentration and determination of lead, cadmium and nickel from water samples using a polyethylene glycol dye immobilized on poly(hydroxyethylmethacrylate) microspheres.

A simple and sensitive preconcentration analysis-atomic absorption spectrometric procedure is described for the determination of lead, cadmium and nickel. The method is based upon on-line preconcentration of metal ions on a minicolumn of Cibacron Blue F3-GA immobilized on poly(hydroxyethylmethacrylate), poly(HEMA). The enrichment factors obtained were 42 for lead, 52 for cadmium and 63 for nickel (sample volume 10 mL and sample flow rate 5 mL/min). The relative standard deviations (n = 10), in 10 mL sample solutions containing 100 microg/L Pb(2+), 10 microg/L Cd(2+) and 100 microg/L Ni(2+) were 8.9, 3.7 and 3.5%, respectively. The limits of detection (blank + 3s) (n = 10), were found to be 12.01 microg/L for Pb(2+), 1.34 microg/L for Cd(2+) and 28.73 microg/L for Ni(2+). The accuracy of the system was checked with certified and tap water samples spiked with known amounts of metal ions. No significant difference was found between the achieved results and the certified values.     

Photodegradation and flow-injection determination of simetryn herbicide by luminol chemiluminescence detection

A novel and simple flow injection chemiluminescence method is reported for the determination of simetryn, a common herbicide. The method is based on the direct oxidation of luminol by the photoproducts of the simetryn in alkaline medium in the absence of catalyst/oxidant. The linear concentration range was 0.01 - 2 microg mL(-1) simetryn with a correlation coefficient (r(2)) of 0.9997 and relative standard deviations (RSD; n = 4) in the range of 0.9 - 2.3%. The limit of detection (S/N = 3) was 7.5 ng mL(-1) with a sample throughput of 100 h(-1). The proposed method has been applied to determine simetryn in natural waters using Sep-Pak C(18) cartridges for solid phase extraction (SPE) procedure. The recoveries were in the range of 97 +/- 1 to 104 +/- 2%. The mechanism of chemiluminescence reaction has also been discussed briefly.     

Stability indicating method for famotidine in pharmaceuticals using porous graphitic carbon column

A simple, sensitive and rapid HPLC method was developed and validated for the simultaneous determination of famotidine (FMT) and related impurities in pharmaceuticals. Chromatographic separation was accomplished within 10 min on a porous graphitic carbon (PGC) column using 50:50 v/v ACN-water containing 0.5% pentane sulphonic acid (PSA) as the mobile phase. Separation was achieved with a flow rate of 1 mL/min and a detection wavelength of 265 nm. The calibration curves were linear over a concentration range of 1.5-100 microg/mL. The intra- and interday RSDs (n = 5) for the retention times and peak area were all less than 2%. The method was sensitive with an LOD (S/N = 3) of 0.1 microg/mL for FMT, imp. C and 0.05 microg/mL for imp. 2, A and D. All recoveries were greater than 98%. The method was demonstrated to be precise, accurate and specific with no interference from the tablet ingredients and separation of the drug peak from the peaks of the degradation products (oxidative degradation and acid and base degradation). The results indicated that the proposed method could be used for the determination of FMT in commercial dosage forms and as a stability-indicating assay.     

Determination of formaldehyde by staircase voltammetry based on its electrocatalytic oxidation at a nickel electrode

In this paper, a novel method for detection of formaldehyde (HCHO), based on its electrocatalytic oxidation of HCHO at a nickel electrode, is reported. The mechanism of electrocatalytic oxidation and quantification of HCHO have been investigated by cyclic and staircase voltammetry, respectively. The electrocatalytic oxidation peak potential of HCHO is at about 475 mV vs. Ag/AgCl electrode; the peak current responds proportionally to concentrations of HCHO in alkaline solution. The linear range of detection is from 46.8 to 1640 μg/L (1.56 × 10⁻⁶ to 5.46 × 10⁻⁵ M) with a correlation coefficient of 0.996 and a detection limit of 23.4 μg/L (7.80 × 10⁻⁷ M). The relative standard deviation (RSD) is less than 6% (n = 5), and the recovery is in the range 98–106% for real samples. The result is consistent with that from the spectrophotometry. The text was submitted by the authors in English.     

Spectrofluorometric determination of fluvoxamine in dosage forms, spiked plasma, and real human plasma by derivatization with fluorescamine

A sensitive, simple, and selective spectrofluorometric method was developed for the determination of fluvoxamine (FXM) in pharmaceutical formulations and biological fluids. The method is based upon the reaction between the drug and fluorescamine in borate buffer of pH 8.0 to yield a highly fluorescent derivative that is measured at 481 nm after excitation at 383 nm. The different experimental parameters affecting the development and stability of the reaction product were carefully studied and optimized. The method was applied for the determination of the drug over the concentration range of 0.1-1.1 microg/mL with a detection limit of 0.01 microg/mL (2 x 10(-8) M). The proposed method was successfully applied to the analysis of commercial tablets. The results obtained were in good agreement with those obtained using a reported spectrophotometric method. The method was applied for the determination of FXM in spiked human plasma with recovery (n=4) of 97.32 +/- 1.23%, while that in real human plasma (n=3) was 90.79 +/- 2.73%. A proposal for the reaction pathway is presented.     

Flow injection determination of formaldehyde by its catalytic effect on the oxidation of sulfonazo III by bromate with spectrophotometric detection.

A simple and sensitive flow injection method with spectrophotometric detection was developed for the determination of formaldehyde. The method is based on the catalytic effect of formaldehyde on the oxidation of sulfonazo III with bromate in acidic media. The decrease in absorbance of the reaction mixture was measured at 566 nm. The calibration graph was linear in the range of 0.005 to 2.80 microg ml(-1) formaldehyde at a rate of 38 +/- 4 samples h(-1). The limit of detection was 4 ng ml(-1). The relative standard deviations for ten replicate measurements of 0.20, 0.50 and 1.00 microg ml(-1) formaldehyde were 1.3, 0.8 and 0.7%, respectively. The method was applied to the determination of formaldehyde in river water, shampoo and melamine-formaldehyde resin.     

Development of HPTLC-UV absorption densitometry method for the analysis of alprazolam and sertraline in combination and its application in the evaluation of marketed preparations

A new simple, sensitive, and reproducible high-performance thin-layer chromatography method for the estimation of alprazolam and sertraline in combination is developed using silica gel plates with fluorescent indicators. The system is equipped with an automated sample applicator, and the detection was performed at 254 nm by using UV absorption densitometry. The mobile phase consists of carbon tetrachloride, methanol, acetone, and ammonia in the ratio 12:3:5:0.1. The retention factor values for alprazolam and sertraline are found to be 0.52 and 0.70, respectively. The limit of detection of alprazolam and sertraline in the mixture of given proportion is observed to be 0.05 microg/mL and 2.5 microg/mL and the limit of quantitation is 0.2 microg/mL and 10 microg/mL, respectively. The method has shown good linearity in the range of 0.2 microg/mL to 0.65 pg/mL for alprazolam (R2 > 0.9953) and 10 pg/mL to 32.5 microg/mL for sertraline (R2 > 0.9942). The intra- and inter-assay (n=5) variations in the linear range are less than 4% for alprazolam and 6% for sertraline. Three pharmaceutical products containing this combination are analyzed to test the applicability of the new method. The percentage of alprazolam and sertraline in the tablets studied range from 97.7% to 102.82% and 96.5% to 99.9%, respectively.     

Electrocatalytic oxidation of formaldehyde and methanol on Ni(OH)2/Ni electrode

A nickel hydroxide-modified nickel electrode (Ni(OH)₂/Ni) was successfully prepared by the cyclic voltammetry (CV) method and the electrocatalytic properties of the electrode for formaldehyde and methanol oxidation have been investigated respectively. The Ni(OH)₂/Ni electrode exhibits high electrocatalytic activity in the reaction. A new method has been developed for formaldehyde determination at the nickel hydroxide-modified nickel electrode and the experimental parameters were optimized. The oxidation peak current is linearly proportional to the concentration of formaldehyde in the range of 7.0 × 10^?5 to 1.6 × 10^?2 M with a detection limit of 2.0 × 10^?5 M. Recoveries of artificial samples are between 93.3 and 103.5%. The effect of scan rate and methanol concentration on the electrochemical behavior of methanol were investigated respectively.     

沙丁胺醇在SDBS现场自组装膜与［BnMIM］PF6复合修饰碳糊电极上的电催化氧化及电分析方法

研究了沙丁胺醇(SAL)在表面活性剂十二烷基苯磺酸钠(SDBS)现场自组装膜与离子液体1-苄基-3-甲基咪唑六氟磷酸盐([BnMIM]PF6)复合修饰碳糊电极(SDBS-[BnMIM]PF6/CPE)上的电催化氧化行为和电化学动力学性质。实验结果表明,SDBS-[BnMIM]PF6/CPE对SAL的电化学氧化具有良好的催化作用。用循环伏安法(CV)和计时电流法(CA)测得SAL在SDBS-[BnMIM]PF6/CPE上的电极反应过程动力学参数。用方波伏安法(SWV)测得SAL氧化峰电流(Ipa)与其浓度在9.0×10-5～1.0×10-3mol.L-1范围内呈良好的线性关系,检出限(S/N=3)为1.08×10-6mol.L-1。运用该方法对市售吸入用沙丁胺醇溶液中SAL的含量进行了测定,结果满意。     

抗坏血酸在聚对羟基苯甲酸(poly-PHB)修饰玻碳上的电催化

过循环伏安制备了聚对羟基苯甲酸修饰的玻碳电极。考察了该电极对抗坏血酸的电催化性能。结果显示,聚对羟基苯甲酸修饰玻碳电极对抗坏血酸有很好的电催化作用。在修饰后的电极上产生的峰电流比修饰前的电极产生的峰电流大4倍,氧化峰电位负移189 mV。其氧化峰电流与抗坏血酸浓度在2.6×10-5~3.68 ×10-4mol/L范围内呈线性关系,相关性系数为0.9984,检测限为5×10-6 mol/L(S /N = 3)。在AA与UA共存的体系中,能排除多巴胺对抗坏血酸测定的干扰。     

Second derivative synchronous fluorescence spectroscopy for the simultaneous determination of metoclopramide and pyridoxine in syrup and human plasma

A rapid, simple, and highly sensitive second derivative synchronous fluorometric method has been developed for the simultaneous determination of metoclopramide (MT) and pyridoxine (PY) in a binary mixture. The method is based on measurement of the native fluorescence of these drugs at delta lambda = 80 nm in methanol. The different experimental parameters affecting the native fluorescence of the drugs were carefully studied and optimized. The fluorescence-concentration plots were rectilinear over the ranges of 0.02-0.4 and 0.1-2 microg/mL for MT and PY, respectively. The limits of detection were 0.003 and 0.007 microg/mL and the limits of quantification were 0.008 and 0.02 microg/mL for MT and PY, respectively. The proposed method was successfully applied to the determination of MT and PY in synthetic mixtures and in commercial syrup. The results were in good agreement with those obtained with a reported method. The high sensitivity attained by the proposed method allowed the determination of MT in spiked and real human plasma samples. The mean percent recoveries of MT from spiked and real human plasma (n = 3) were 93.72 +/- 3.15 and 89.72 +/- 2.19 respectively.     

Synthesis of Ruthenium Xanthate Complex and Its Electrocatalytic Activity for Tryptophan Oxidation

A new ruthenium complex containing bidentate xanthate ligands was synthesized in a good yield. This complex was characterized by elemental analysis, proton nuclear magnetic resonance(¹H NMR), Fourier transform infrared(FTIR) and UV-Vis spectroscopies. The cyclic voltammetry of the complex revealed one quasi-redox wave centered at Ru(Ⅲ)/ Ru(Ⅱ) couple, indicating its catalytic potential. So the preparation of a glass carbon electrode modified with ruthenium xanthate complex and its electrocatalytic activity toward the oxidation of tryptophan(Trp) were also studied. The experimental results show that the modified electrode had excellent electrocatalytic activity for the oxidation of tryptophan. Moreover, under the optimized conditions, the oxidation peak current was proportional to tryptophan concentration in a range of 2.5×10^-7 to 5.0×10^-5 mol/L with a correlation coefficient of 0.9928 and a detection limit of 8.3×10^-8 mol/L(S/N=3). Using the proposed method, tryptophan was successfully determined in pharmaceutical samples with standard addition method.