Sensitive quantification of iodide by ion-exchange chromatography with electrochemical detection at a modified platinum electrode

A rapid and very sensitive method for the accurate determination of free iodide in real samples is described. The method is based on anion-exchange chromatographic separation coupled with amperometric detection at a modified platinum electrode under constant applied potential (+0.85 V vs. Ag AgCl). An experimental setup with an in-line and very effective method of electrode modification is proposed using an amperometric thin-layer cross-flow detector and a flowing solution 300 mg/L of iodide; the working electrode is polarised to the limiting current for oxidation of iodide to iodine in acidic solutions with the consequent formation of an iodine-based film. The results indicated that the modified electrode exhibits high analytical response for iodide electrooxidation with good stability and long-life. The signal intensity of daily experimental sessions (8 h), during which standards and real samples were repeatedly injected, exhibits a moderate lowering (i.e. <6%). Using a mixture of 25 mM HNO₃ and 50 mM NaNO₃ as an eluent phase in ion-exchange chromatography, the detection limit of iodide was estimated to be 0.5 g/L (S/N=3) with an injection volume of 50 L. This method was applied successfully to quantify the iodide content of milk samples and in wastewaters as well as trace amounts in common vegetables and solutions containing high chloride levels.     

Pulsed electrochemical detection of orotic acid by an activated potential waveform at a gold working electrode following anion-exchange chromatography

The application of activated pulsed amperometric detection (APAD) for the determination of orotic acid (OrA) in real samples at a gold working electrode in alkaline solutions, in combination with anion-exchange chromatography, is reported. Such an activated potential waveform was designed with an initial step that involves the formation of redox active species (e.g., adsorbed AuOH/AuO), which in turn is halted upon lowering the applied potential at the detection value while the adsorbed gold hydroxide/oxide species are still catalytically active. A direct comparison between the activated potential waveform and the more commonly used pulsed amperometric detection showed roughly a 20-fold increase in sensitivity. The chromatographic separation of OrA was accomplished by using a microbore anion-exchange column eluted with an isocratic mobile phase composed of 100 mM NaOH+40 mM NaNO(3). Orotic acid was determined at the concentration ranges of 0.2-30 microM (r=0.9997) with an absolute detection limit of 80 pg (10 microL injected). The levels of OrA in cows' milk samples evaluated by standard additions, using 5-aminoorotic acid as an internal standard, ranged from 56 to 126 mg/L. Lower levels were found in raw sheep's milk (<20 mg/L). The assay is shown to be very useful in clinical investigations where relatively high levels of OrA in human urine are correlated to metabolic diseases.     

Determination of mono- and disaccharides in milk and milk products by high-performance anion-exchange chromatography with pulsed amperometric detection

A simple and sensitive liquid chromatographic method for the separation and quantification of mono- and disaccharides in raw- and processed-milk is described. Samples of cows’, buffalos’, sheeps’ and goats’ milk were analyzed upon clarification and appropriate dilution for the quantification of lactose, galactose, glucose and N-acetylglucosamine (GlcNAc). The separation was accomplished by high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD), using a gold working electrode and dilute alkaline eluents modified by a millimolar concentration of barium acetate. The eluent composition employed was designed to provide optimum separation with respect to the selected sample, without interference from the matrix components. The analytical method was successfully employed for the determination of mono- and disaccharides naturally occurring in dairy milk, mozzarella cheese and whey samples, with high sensitivity and accuracy.     

Development of capillary electrophoresis methods for quantitative determination of taurine in vehicle system and biological media

CE methods have been developed for the determination of taurine in pharmaceutical formulation (microemulsion) and in biological media such as sweat. The CE system with end-column pulsed amperometric detection has been found to be an interesting method in comparison with UV and fluorescence detection for its simplicity and rapidity. A gold-disk electrode of 100 mm diameter was used as the working electrode. The effects of a field decoupler at the end of the capillary, separation voltage, injection and pressure times were investigated. A detection limit of 4 x 10(-5) mol/L was reached using integrated pulsed amperometric detection, a method successfully applied to taurine analysis of the biological samples such as sweat. For taurine analysis of oil-in-water microemulsion, fluorescence detector was the favored method, the detection limit of which was 4 x 10(-11) mol/L.     

二维离子色谱法同时测定4种无机阴离子和葡萄糖酸根离子

建立了一种新的二维离子色谱分析模式,应用阀切换技术并联抑制电导和脉冲安培双检测体系,同时测定Cl^-、NO₂^-、SO₄^2-、NO₃^-和葡萄糖酸根离子。第一维色谱采用Ionpac AG18+Ionpac AS18阴离子分析柱,分别以5和20 mmol/L的NaOH溶液等度淋洗,流速为1.0 mL/min,进样量为25 μL,抑制电导检测Cl^-、NO₂^-、SO₄^2-和NO₃^-。第二维色谱采用CarboPac PA1+CarboPac PA20两保护柱串联,以90 mmol/L NaOH溶液、0.8 mL/min的流速洗脱,由AG15柱分离富集葡萄糖酸根,脉冲安培检测器检测。结果表明:无机阴离子在0.1~5.0 mg/L、葡萄糖酸根在0.0856~4.2825 mg/L范围内有良好的线性关系,RSD在1.05%~1.94%之间,相关系数(R²)在0.9945以上;无机阴离子的方法检出限为0.615~2.17 μg/L,葡萄糖酸根的方法检出限为24.24 μg/L;回收率在90.3%~102.8%之间。该方法并联两种检测模式,有良好的准确度和精密度,适用于复杂样品的分离分析。     

Influence of Modifier-Free Hydroxide Eluents on the Separation of Carbohydrates by Anion Exchange Chromatography

Eluents based on low hydroxide concentrations are favourable in terms of selectivity for the separation of selected carbohydrates with anion exchange chromatography (AEC) and pulsed amperometric detection. The order of retention of many carbohydrates such as sucrose can be changed simply by selecting the appropriate hydroxide concentration.Instable retention times and weak detection efficiency were observed for hydroxide concentrations below 30mM without modifier. The time dependence of this retention loss was studied by step-changes of the eluent concentration. Linear behaviour with time is observed for all carbohydrates investigated. The slope of the relative decrease of retention is dependent on column capacity and presumably on its carbonate contents.The decrease in retention can be effectively suppressed by using a scavenger column filled with a high-capacity, strong anion exchanger. The variation of retention times were lowered from up to 100% to typically less than 1% during 72h of operation for a 10mM NaOH eluent without any modifier.     

高效阴离子交换色谱-脉冲安培检测法测定烤烟中的水溶性葡萄糖、果糖和蔗糖

用高效阴离子交换色谱-脉冲安培检测法（HPAEC-PAD）测定了烤烟中的水溶性葡萄糖、果糖和蔗糖。采用水浸取及膜过滤法处理烤烟样品,以Dionex CarboPac PA-1阴离子交换柱为色谱柱,0.2 mol/L NaOH水溶液为淋洗液进行分离测定。葡萄糖、果糖和蔗糖的含量与其峰面积的线性关系良好,回收率均在97%以上。方法简便易行,灵敏度高,重现性良好,可以实现对烟草中单糖的快速分离和测定。     

Application of Graphene as Solid Phase Extraction Absorbent for the Determination of Parabens in Cosmetic Products by Capillary Electrophoresis

A graphene-based solid phase extraction (SPE) technique was developed for the extraction of parabens (methylparaben, ethylparaben, propylparaben, and butylparaben) in cosmetic samples, followed by determination by capillary electrophoresis (CE). The SPE extraction parameters such as eluent reagent and eluent volume, washing solution, sample pH, and flow-rate of sample loading, were investigated for satisfied recoveries. The running buffer, consisting of 25 mM borate solution (pH 10.0), was used for the separation of four parabens with the CE method within 10 min. The limits of detection were 0.14 mg/L, 0.13 mg/L, 0.15 mg/L, and 0.10 mg/L for methylparaben, ethylparaben, propylparaben, and butylparaben, respectively, and the mean recoveries obtained were between 62.6% and 100.4%. The developed method was used for the determination of parabens in real cosmetic products.     

安培检测-离子色谱法测定乳品中的微量碘

 用安培检测 离子色谱法检测了乳品中的微量碘。以NaOH作淋洗液 ,直接进样 ,优化了碘的离子色谱分离和测定条件 ,方法的检测限达 1μg/L(3倍信噪比 )。测定了婴儿奶粉、孕产妇专用奶粉和鲜牛奶中的微量碘 ,加标回收率分别为 89 0 % ,86 0 %和 84 1%。     

Non-suppressed conductivity and indirect UV detection of carboxylic acids in environmental samples by ion-exclusion chromatography using 2,6-pyridinedicarboxylic acidic eluent

2,6-Pyridinedicarboxylic acid (PDCA) was evaluated as an eluent for indirect UV and non-suppressed conductivity detection of carboxylic acids in ion-exclusion chromatography. The effect of PDCA concentration on the separation and detection sensitivity was investigated. The reasonable resolutions between carboxylic acids were achieved using 1 mM PDCA eluent. Detection limits were 1.0-7.0 microM for conductivity detection and 8-30 microM for UV detection. Compared to the eluent containing 1 mM sulfuric acid, the method offers a high resolution and high detection sensitivity for both detectors due to its high molar absorptivity and low background conductance. The proposed method was demonstrated to be useful for the determination of carboxylic acids in environmental samples with direct sample injection.     

固相萃取-高效阴离子交换色谱-积分脉冲安培法检测人体尿液中的异黄蝶呤

建立了固相萃取-高效阴离子交换色谱-积分脉冲安培法(SPE-HPAEC-IPAD)测定人体尿液中异黄蝶呤的分析方法。尿液经ENVI-18与732型阳离子交换柱串联萃取后,除去了大量干扰物质。采用IonPac AS21分析柱(250 mm×2 mm),以0.025 mol/L NaOH溶液为淋洗液,流速为0.40 mL/min,在优化的安培检测波形条件下,异黄蝶呤的质量浓度在0.005～0.200 mg/L范围内与峰面积呈良好的线性关系,相关系数为0.998 4,检出限为0.003 mg/L。健康人及癌症病人尿液在2 mg/L和5 mg/L两个添加水平的平均回收率在95.4%～96.8%之间,相对标准偏差小于5%。此方法环保、快速、准确,可用于健康人与癌症病人尿液中异黄蝶呤的测定。     

Serial separation of cations and anions by ion chromatography using the peak parking technique and sulfosalicylic acid as the eluent

An improvement of the peak parking technique is described for the serial determination of cations (Na⁺, , K⁺, Mg²⁺, and Ca²⁺) and anions (Cl⁻, , and ) using a single pump, a single eluent and a single detector. The present system used commercially-available unmodified cation exchange and anion exchange columns, which were attached to each switching valve. When 1.75 mM 5-sulfosalicylic acid was used as the eluent, serial separation of the above cations and anions was achieved in less than 20 min. The proposed ion chromatographic method was successfully applied to the serial determination of cations and anions in tap water and river water samples. The limits of detection at S/N=3 for an injection of 20 μl were 16–68 ppb (μg/l) for cations and 15–28 ppb for anions.     

HPLC-MS/MS法测定婴幼儿配方乳粉中胆碱、左旋肉碱、牛磺酸与肌醇

建立了一种同时测定婴幼儿配方乳粉中4种可选择成分(胆碱、左旋肉碱、牛磺酸和肌醇)的高效液相色谱-串联三重四极杆质谱(HPLC-MS/MS)分析方法。样品经温水溶解后用亚铁氰化钾和乙酸锌沉淀蛋白,上清液过滤后采用HSS T3色谱柱分离,三重四极杆质谱仪检测,胆碱和左旋肉碱使用内标法定量,牛磺酸和肌醇使用外标法定量。在最优化条件下,胆碱和左旋肉碱在0.01~2.0 mg/L范围内,牛磺酸和肌醇在0.1~2.0 mg/L范围内呈良好的线性关系,相关系数均大于0.997;胆碱和左旋肉碱的检出限均为1.5 mg/kg,牛磺酸和肌醇的检出限均为15 mg/kg。4种化合物的回收率为87.5%~102.4%,相对标准偏差(RSD,n=6)为3.0%~7.3%。该方法灵敏度高、净化效果好、定量准确,适用于婴幼儿配方乳粉中胆碱、左旋肉碱、牛磺酸和肌醇的同时快速检测。     

离子色谱法测定大肠癌患者尿液中的甘露醇和乳果糖

建立了大肠癌患者尿液中甘露醇和乳果糖的高效阴离子交换分离-脉冲积分安培(HPAEC-PAD)检测方法.样品经稀释、净化、过滤后进行色谱分析,采用Carbopac PA1(250 mm×4mm)阴离子交换柱分离,以NaOH-乙酸钠梯度淋洗液为流动相,流速1.0 mL/min,脉冲积分安培检测器(PAD)检测,外标法定量.结果表明,甘露醇和乳果糖的的线性范围为0.2～20 mg/L,相关系数分别为0.9995和0.9998,回收率为91.7％～102.6％,相对标准偏差均小于2.1％,检出限为0.05和0.06 mg/L(S/N=3).本方法前处理简便、灵敏度高、重现性好,可用于大肠癌患者尿液中的甘露醇和乳果糖的测定.     

Poly(dimethylsiloxane) microchip capillary electrophoresis with electrochemical detection for rapid measurement of acetaminophen and its hydrolysate

Poly(dimethylsiloxane) microchip capillary electrophoresis with amperometric detection has been used for rapid separation and determination of acetaminophen and its hydrolysate, i.e. p-aminophenol. A Pt ultramicroelectrode with a diameter of 10 m positioned at the outlet of the separation channel was used as a working electrode for amperometric detection. Factors influencing separation and detection were investigated and optimized. Results show that acetaminophen and p-aminophenol can be well separated within 35 s with RSD<1% for migration time and <7% for detection current for both analytes. Detection limits for both analytes are estimated to be 5.0 mol L^–1 (approximately 0.1 fmol) at S/N=3. This method has been successfully applied to the detection of traces of p-aminophenol in paracetamol tablets.     

阀切换-离子色谱法测定难溶性药物中的氯离子和三氟乙酸根

建立了头孢克肟、月桂酰吲达帕胺、布地奈德等难溶性药物中氯离子和三氟乙酸根的阀切换-离子色谱检测方法。分离柱为IonPac AS23柱,通过考察阴离子保留情况,选择3.5 mmol/L碳酸钠+1.0 mmol/L碳酸氢钠作淋洗液,对难溶性药物中氯离子和三氟乙酸根进行了分析。在上述条件下,氯离子和三氟乙酸根能很好地分离,并在质量浓度为0.10~10.00 mg/L时与对应色谱峰面积之间的线性关系良好,检出限分别为0.006 mg/L和0.06 mg/L,回收率为90%~94%。该方法简便、快速、准确,可用于实际样品的测定。     

Speciation of iodate and iodide in seawater by non-suppressed ion chromatography with inductively coupled plasma mass spectrometry

A non-suppressed ion chromatography (IC) with inductively coupled plasma mass spectrometry (ICP-MS) has been developed for simultaneous determination of trace iodate and iodide in seawater. An anion-exchange column (G3154A/101, provided by Agilent) was used for the separation of iodate and iodide with an eluent containing 20 mM NH₄NO₃ at pH 5.6, which reduced the build-up of salts on the sampler and skimmer cones. The influences of competing ion (NO₃⁻) in the eluent on the retention time and detection sensitivity were investigated to give reasonable resolution and detection limits. Linear plots were obtained in a concentration range of 5.0–500 μg/L and the detection limit was 1.5 μg/L for iodate and 2.0 μg/L for iodide. The proposed method was used to determinate iodate and iodide in seawaters without sample pre-treatment with exception of dilution.     

Determination of sulfur-containing inorganic anions by dual ion chromatography and capillary electrophoresis – application to the characterization of bacterial sulfur degradation

An analytical characterization of microbiological oxidation and reduction of sulfur anions has been performed with dual ion chromatography. The apparatus consisted of two chromatographic lines combined by a sample injection valve that allows the simultaneous introduction of a sample solution to both systems. With system 1 non-suppressed conductivity detection of sulfite and sulfate after separation in phthalate eluent was performed. For sulfide, thiosulfate and thiocyanate amperometric detection using a carbonate eluent was carried out on system 2. Parallel runs were possible for these species which could not be separated with one system. Optimizing separation and detection, limits of quantification of 0.02–0.3 mg/L could be obtained. The on-line coupling of a reaction vial to the injection valve was used to investigate the bacterial conversions, because the samples could be taken without contamination and air introduction. Thiosulfate was detected as a metabolite in both sulfur reduction and oxidation. Capillary electrophoresis with conductivity detection was applied as a complimentary technique for monitoring the bacterial sulfur oxidation. The results showed good correlation to the concentration values obtained by ion chromatography. Received: 14 May 1999 / Revised: 7 July 1999 / Accepted: 10 July 1999     

高效阴离子交换色谱-脉冲安培检测法测定乳粉中的低聚果糖

建立了测定乳粉中低聚果糖的高效阴离子交换色谱-脉冲安培检测(HPAEC-PAD)方法。样品经50%(v/v)乙醇水溶液提取,On Guard RP柱除脂,CarboPac PA200阴离子交换色谱柱(250 mm×3 mm)分离。采用水、0.2 mol/L NaOH溶液和0.4 mol/L NaAc溶液三元梯度淋洗,流速为0.4 mL/min,柱温为30 ℃,进样量为25 μL,脉冲安培检测器检测。蔗果三糖、四糖、五糖在0.05~10 mg/L范围内线性关系良好,相关系数(r²)> 0.9993;定量限分别为0.02、0.005和0.02 mg/L。在0.5、1.0、5.0 mg/L添加水平下,蔗果三糖、四糖、五糖的平均回收率为86.0%~114.0%。该方法处理简单、结果准确、灵敏度高,适用于乳粉中低聚果糖的测定。     

Determination of clotiazepam by HPLC with spectrophotometric and amperometric detection

Summary Spectrophotometric and amperometric detectors were compared for the determination of clotiazepam by HPLC. Methanol-water (6040) containing 0.01 mol/l ammonium acetate and methanol-water (7030) containing 0.01 mol/l acetate buffer pH 4 were used as mobile phase in the spectrophotometric and amperometric detection, respectively. The minimum detectability for the spectrophotometric detection was 20 ng injected and the method was applied for the determination of clotiazepam in serum, whereas for the amperometric detection a limit of detection of 2.5 g injected was obtained, using this technique for clotizepam determination in tablets.

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Bestimmung von Clotiazepam durch HPLC mit spektralphotometrischer und amperometrischer Detektion