Simultaneous analysis of selenate and selenite by single-column ion chromatography

Summary A rapid, selective and sensitive method has been developed for the simultaneous determination of selenate [Se(VI)] and selenite [Se(IV)] at trace levels by single-column ion chromatography. p-Hydroxybenzoic acid (4 mM) at pH 8.0 was used as the eluent. A low capacity resin-based anion-exchange column was employed for the separation with conductometric detection for quantification. The method requires minimal sample pretreatment. Resolution (R_s) between Se(VI)/Se(IV) was 6.76. Chloride, nitrate and sulfate did not interfere with selenium separation. The detection limits for Se(VI) and Se(IV) were 0.06 μg/ml and 0.110 μg/ml, respectively. The relative standard deviation using a 500-μl loop was 0.90 to 1.86% for Se(VI) and Se(IV), respectively. The method was applied to analyze seleniferous soil samples.     

Simultaneous quantitative determination of amiloride hydrochloride and hydrochlorothiazide in tablets by high-performance liquid chromatography

Summary A procedure for the simultaneous quantitative determination of amiloride hydrochloride and hydrochlorothiazide by high-performance liquid chromatography is proposed. A reversed-phase LiChrosorb C8 stationary phase is used. The eluent consisted of an acetonitrile/0.1M phosphate buffer pH3 (15∶85) mixture, containing 50mM propylamine hydrochloride. In this system amiloride hydrochloride, a basic drug, eluted with a acceptable asymmetry factor (Asf=2.1). A simple extraction procedure with methanol is used. Relative standard deviations of 0.87% and 1.6% were obtained for amiloride hydrochloride and hydrochlorothiazide respectively. Chlorothiazide, a thiazide diuretic, is a suitable internal standard. Furthermore the method is also specific for other thiazide diuretics, potassium-sparing diuretics and loop diuretics and for the respective hydrolysis productes of both drugs. Analysis time is reduced to a minimum; the chromatographic separation is complete within 6 minutes.     

Simultaneous determination of preservatives,sweeteners and antioxidants in foods by paired-ion liquid chromatography

Summary A paired-ion, reversed-phase high-performance liquid chromatographic method was developed for the simultaneous determination of sweeteners (dulcin, saccharin-Na and acesulfame-K), preservatives (sodium dehydroacetate, sorbic acid, salicyclic acid, benzoic acid, succinic acid, methyl-para-hydroxybenzoic acid, ethylpara-hydroxybenzoic acid, n-propyl-para-hydroxybenzoic acid, isopropyl-para-hydroxybenzoic acid, n-butyl-para-hydroxybenzoic acid, and isobutyl-para-hydroxybenzoic acid), and antioxidants (3-tertiary-butyl-4-hydroxyanisole and tertiary-butyl-hydroquinone). A mobile phase of acetonitrile-50 mM aqueous -hydroxy-isobutyric acid solution (pH 4.5) (2.2 3.4 or 2.4 3.6, v/v) containing 2.5 mM hexadecyltrimethylammonium bromide and a C₁₈ column with a flow rate at 1.0 mL/min and detection at 233 nm were used. This method was found to be very reproducible with detection limits ranged from 0.15 to 3.00 g. The retention factor (k) of each additive could be affected by concentrations of hexadecyltrimethylammonium bromide and -hydroxyisobutyric acid, and pH and ratio of mobile phase. The presence of additives in some food samples was determined.     

离子色谱非梯度洗脱法同时测定7种稀土元素的研究

研究了离子色谱非梯度洗脱法同时测定7种稀土元素的方法,用草酸一元淋洗液,采用非梯度洗脱方式,以PAR为显色荆,在520nm处对7种稀土元素同时进行检测。考察了淋洗液的组成、浓度、pH及流量等因素对被测组分分离和测定的影响,选择了显色剂的浓度、流量和检测波长,并进行了干扰实验,在选定的最佳分离测定条件下,测定了7种稀土元素的线性回归方程、检出限0．04～0．20mg／L,回收率在94．3％～101．5％之间。本方法已用于稀土氧化物的高温氯化产物中稀土元素的测定。     

Simultaneous determination of preservatives,sweeteners and antioxidants in foods by paired-ion liquid chromatography

Summary A paired-ion, reversed-phase high-performance liquid chromatographic method was developed for the simultaneous determination of sweeteners (dulcin, saccharin-Na and acesulfame-K), preservatives (sodium dehydroacetate, sorbic acid, salicyclic acid, benzoic acid, succinic acid, methyl-para-hydroxybenzoic acid, ethyl-para-hydroxybenzoic acid, n-propyl-para-hydroxybenzoic acid, isopropyl-para-hydroxybenzoic acid, n-butyl-para-hydroxybenzoic acid, and isobutyl-para-hydroxybenzoic acid), and antioxidants (3-tertiary-butyl-4-hydroxyanisole and tertiary-butyl-hydroquinone). A mobile phase of acetonitrile-50 mM aqueous α-hydroxyisobutyric acid solution (pH 4.5) (2.2 : 3.4 or 2.4 : 3.6, v/v) containing 2.5 mM hexadecyltrimethylammonium bromide and a C₁₈ column with a flow rate at 1.0 mL/min and detection at 233 nm were used. This method was found to be very reproducible with detection limits ranged from 0.15 to 3.00 μg. The retention factor (k) of each additive could be affected by concentrations of hexadecyltrimethylammonium bromide and α-hydroxyisobutyric acid, and pH and ratio of mobile phase. The presence of additives in some food samples was determined.     

Simultaneous determination of oxalate, thiosulfate, and thiocyanate in urine by ion-exclusion chromatography with electrochemical detection

Summary A sensitive ion-exclusion chromatographic method has been developed for determination of oxalate, thiosulfate, and thiocyanate. The method is based on separation of these anions on a polymethacrylate-based, weakly acidic cation-exchange resin (TSKgel OApak-A) and detection by means of a glassy carbon (GC) electrode electrochemically modified with polyvinylpyridine (PVP), palladium, and iridium oxide (PVP/Pd/IrO₂). The electrochemical behavior of oxalate, thiosulfate, and thiocyanate at this chemically modified electrode (CME) have been investigated by cyclic voltammetry. The results indicated that electrocatalytic oxidation of these anions by the electrode was efficient and that the sensitivity, stability, and lifetime of the electrode were relatively high. Combined with ion-exclusion chromatography the PVP/Pd/IrO₂ electrode was used as the working electrode for amperometric detection of these anions. All linear ranges were over two orders of magnitude and detection limits, defined asS/N=3, were 9.0×10⁻⁷ mol L⁻¹ for oxalate, 6.7×10⁻⁷ mol L⁻¹ for thiosulfate, and 5.6×10⁻⁷ mol L⁻¹ for thiocyanate. Correlation coefficients were all>0.998. Coupled with microdialysis sampling the method has been successfully applied to the determination of oxalate, thiosulfate, and thiocyanate in urine.     

单柱离子色谱法测定过热器管垢和锅炉垢中铁、镁和钙的含量

首先用碱熔融法分解试样,然后加抗坏血酸将试液中的Ｆｅ３＋还原为Ｆｅ２＋,再用离子色谱法测定试液中的Ｆｅ２＋,Ｍｇ２＋和Ｃａ２＋。采用Ｓｈｉｍ－ｐａｃｋＩＣ－Ｃｌ阳离子交换柱分离样品离子,以０．２５ｍｍｏｌ／Ｌ乙二胺－０．５０ｍｍｏｌ／Ｌ柠檬酸（ｐＨ４．５０）为流动相,以ＣＤＤ－６Ａ电导检测器检测,使被测组分得到满意的分离和检测。Ｆｅ,Ｍｇ和Ｃａ的加标回收率均在９０％以上。测定结果与原子吸收光谱法测定结果相近。     

离子色谱法测定地表水氨的条件优化

基于美国Aquion ICS型离子色谱仪,优化离子色谱分析在饮用水氨检测中的应用条件,由实验结果所得的回归方程为A=0.2562ρ+0.008, 相关系数r=0.9998。在精密度检测中0.5 mg/L和10 mg/L的标准溶液所得标准偏差分别为1.130%和0.114%。在加标回收测试中加标量为1mg和2mg时,回收率在98%-102%、98%-100.1%。说明该方法总体准确度较高,可以满足检测需求。     

Simultaneous determination of ascorbic acid,dopamine and uric acid based on tryptophan functionalized graphene

A new type of tryptophan-functionalized graphene nanocomposite (Trp-GR) was synthesized by utilizing a facile ultrasonic method via π–π conjugate action between graphene (GR) and tryptophan (Trp) molecule. The material as prepared had well dispersivity in water and better conductivity than pure GR. The surface morphology of Trp-GR was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. The electrochemical behaviors of ascorbic acid (AA), dopamine (DA), and uric acid (UA) were investigated by cyclic voltammetry (CV) on the surface of Trp-GR. The separation of the oxidation peak potentials for AA–DA, DA–UA and UA–AA was about 182 mV, 125 mV and 307 mV, which allowed simultaneously determining AA, DA, and UA. Differential pulse voltammetery (DPV) was used for the determination of AA, DA, and UA in their mixture. Under optimum conditions, the linear response ranges for the determination of AA, DA, and UA were 0.2–12.9 mM, 0.5–110 μM, and 10–1000 μM, with the detection limits (S/N = 3) of 10.09 μM, 0.29 μM and 1.24 μM, respectively. Furthermore, the modified electrode was investigated for real sample analysis.     

Simultaneous determination of rosiglitazone and metformin in plasma by gradient liquid chromatography with UV detection

A novel, fast and simple liquid chromatographic method was developed and validated for the simultaneous determination of rosiglitazone and metformin in human plasma. The analysis was performed on a phenyl column (250 mm × 4.6 mm i.d., 5 μm) using a gradient method starting with mobile phase composed of acetonitrile:5 mM acetate buffer pH 5.5 (75:25, v/v). The flow rate was 1 mL min⁻¹. UV detection was performed at 245 nm and verapamil was used as internal standard. The total run time was less than 10 min. Sample preparation included a simple protein precipitation step with acetonitrile. Validation experiments were performed to demonstrate stability, specificity, sensitivity, linearity, accuracy, precision and robustness. The limit of quantification was 100 ng mL⁻¹ for rosiglitazone and 250 ng mL⁻¹ for metformin. The extraction recoveries were 100.02-105.0% for rosiglitazone and 105.64-103.88% for metformin. The method was applied with success to plasma samples obtained from diabetic patients undergoing treatment with rosiglitazone and metformin.     

Simultaneous determination of catecholamines by ion chromatography with direct conductivity detection

A simple method for simultaneous determination of three catecholamines using ion chromatography (IC) with direct conductivity detection (CD) based on the ionization of catecholamines in acidic medium without chemical suppression is developed in the present paper. The method could be used for the determination of these catecholamines in pharmaceutical preparations for the purpose of drug quality control. The recovery of catecholamines was more than 97% (n=3) and the relative standard deviation (R.S.D.) (n=11) was less than 2.1%. In a single chromatographic run, norepinephrine (NE), epinephrine (E) and dopamine (DA) can be determined in less than 10 min. The detection limits were found to be 0.001 μg/ml for NE, 0.01 μg/ml for E and DA respectively. Linear ranges were 0.01–50 μg/ml for NE (r²=0.9998), 0.1–50 μg/ml for E (r²=0.9995) and DA (r²=0.9999), respectively.     

阴离子和阳离子的同时离子色谱分析法

本文就单独阴离子或阳离子交换柱，阴阳离子交换柱共用，包覆固定相和混合床固定相离子色谱法同时分析阴阳离子的特点及发展前景作了综述和简要评价。     

Simultaneous determination of water- and fat-soluble vitamins in pharmaceutical preparations by high-performance liquid chromatography coupled with diode array detection

Water- and fat-soluble vitamins were separated on a MetaChem Polaris C18-A (150 mm×4.6 mm, 3 μm particle size) in a single run using combined isocratic and linear gradient elution with a mobile phase consisting of 0.010% trifluoroacetic acid of pH 3.9 (solvent A) and methanol (solvent B) at the flow rate 0.7 ml min⁻¹. A linear gradient profile (A:B) started at 95:5 and was constant in the first 4 min, then linearly decreased up to 2:98 during the next 6 min, then it was constant in the next 20 min and finally linearly increased up to 95:5 ratio of water phase in the last 5 min of the separation. The most suitable detection wavelength for simultaneous vitamin determination was 280 nm. The method was applied for the solid sample of pharmaceutical preparation (B-Komplex), fortified powdered drinks (multi-vitamin) and food samples. The results were in good agreement with the declared values.     

离子色谱法同时测定烟草中6种糖

利用离子色谱法同时测定烟草中鼠李糖、葡萄糖、木糖、果糖、蔗糖和麦芽糖。采用超声浸提烟草中的糖,经Metrosep Carb 1阴离子交换柱分离,以0.100mol·L-1氢氧化钠溶液为淋洗液,采用脉冲安培检测器检测。6种糖的浓度在一定范围内与峰面积呈线性关系,方法的检出限在0.012~0.055mg·L-1之间。样品回收率在92.6%~105%之间,测定值的相对标准偏差(n=6)在0.6%~2.0%之间。方法用于快速分析烤烟的上、中、下部中6种糖的含量。     

多分离模式液相色谱法同时分析阴、阳离子的研究

采用基于纳米聚合物-硅胶混合技术,同时具有反相、阴、阳离子交换的多分离模式色谱分离功能的Acclaim Trinity P1色谱柱,直接电导检测,建立了同时分析Li+,NH+4,K+,HCOO!,NO!2,Cl!,NO!3和Br!8种离子的分析方法。通过探讨淋洗液对离子保留的影响,优化得到实验条件如下:淋洗液:25 mmol/L乙酸钠+50%(V/V)乙腈,用冰醋酸调至pH 5.0;柱温:30℃;流速:0.50 mL/min;直接电导检测。8种阴阳离子(Li+,NH+4,K+,HCOO!,NO!2,Cl!,NO!3和Br!)能够同时被分离和检测。化肥样品经稀释溶解过滤后直接进样,结果表明,8种离子的线性范围为0.5~200 mg/L,线性相关系数均大于0.9997,相对标准偏差RSD(n=9)为1.3%~2.5%,检出限(S/N=3)在0.16~1.70 mg/L之间。将本方法用于化肥中阴阳离子的测定,加标回收率为95.8%~103.8%。     

干灰化–离子色谱法测定木耳标准物质中的钾、钙、镁

采用离子色谱法对木耳标准物质中的K,Ca,Mg进行测定,对样品消解以及离子色谱分离条件进行了优化。在优化实验条件下,该法对木耳中K,Ca,Mg 3种元素测定结果的相对标准偏差小于1.0%(n=7)。采用该方法对NIST西红柿叶标准物质(SRM1573a)进行测定,测定结果与标准值相符,同时与ICP–OES方法比较验证,两者测定结果一致。对该方法测定结果的不确定度进行了评定,K,Ca,Mg测定结果的相对扩展不确定度(k=2)分别为2.3%,3.3%,1.9%。该方法准确可靠,能够满足标准物质定值的要求。     

Simultaneous determination of trace level bromate and chlorinated haloacetic acids in bottled drinking water by ion chromatography

A convenient and sensitive method for the simultaneous determination of trace level of bromate and chlorinated haloacetic acids in bottled drinking water with ion chromatography is presented. With a high capacity anion-exchange column and 11.5 mmol/l Na₂CO₃ eluent, all the 16 analytes could be separated in one injection within 31 min. By employing a microwave based evaporation technique, the bottled drinking water sample could be concentrated tenfold in 10 min. The recoveries of the compounds ranged from 90.6 to 107.2%. With a 500 μl large volume injection and high performance anion Atlas electrolytic suppressor, the detection limits were 0.06, 0.08, 0.06, 0.14 and 0.85 μg/l for BrO₃⁻, ClO₃⁻, monoacetic acid, dichloroacetic acid and trichloroacetic acid, respectively.     

Simultaneous determination of hydroquinone and catechol at PASA/MWNTs composite film modified glassy carbon electrode

A poly-amidosulfonic acid and multi-wall carbon nanotubes composite (PASA/MWNTs) modified electrode has been constructed by electropolymerization on glassy carbon electrode (GCE). The electrochemical behaviors of hydroquinone (HQ) and catechol (CC) were investigated using cyclic and differential pulse voltammetries (DPVs) at the prepared electrode. Separation of the reductive peak potentials for HQ and CC was about 120 mV in pH 6.0 phosphate buffer solution (PBS), which makes it suitable for simultaneous determination of these compounds. In the presence of 1.0 × 10⁻⁴ mol L⁻¹ isomer, the reductive peak currents of DPV are proportional to the concentration of HQ in the range of 6.0 × 10⁻⁶ to 4.0 × 10⁻⁴ mol L⁻¹, and to that of CC in the range of 6.0 × 10⁻⁶ to 7.0 × 10⁻⁴ mol L⁻¹. When simultaneously changing the concentration of both HQ and CC, the linear concentration range of HQ (or CC) is 6.0 × 10⁻⁶ to 1.0 × 10⁻⁴ mol L⁻¹ (or 6.0 × 10⁻⁶ to 1.8 × 10⁻⁴ mol L⁻¹), and the corresponding detection limits are 1.0 × 10⁻⁶ mol L⁻¹. The proposed method has been applied to simultaneous determination of HQ and catechol in water sample, and the results are satisfactory.