积分脉冲安培法测定苯乙胺

苯乙胺;金电极;循环伏安;积分脉冲安培法     

Selective detection of metal species in HPLC and FIA by means of pulsed amperometric detection (PAD)

Triple-step pulsed amperometry is used to detect selectively metal complex species after HPLC separation in the presence of coeluting matrix compounds. Optimized pulse parameters enable accurate and selective detection of species even in the presence of electroactive compounds such as phenols or sulfurcontaining peptides. Complexes of tin(IV) with rutin and of platinum(II) with glutathione are presented as examples for these classes of compounds. It is demonstrated that by changing the pulse waveform direct and indirect detection modes can be realized. The method is applied to detect platinum species in a grass extract and iron(II)-lactate in fruit juice. Furthermore it is shown, that pulsed amperometry can be used as a detector in FIA for determining the fraction of metal complex formed after mixing of metal and excess ligand without separation.     

Optimizing the integrated pulsed amperometric multicycle step waveform for the determination of tetracyclines

A method of modified integrated pulsed amperometric detection with multicycle step waveform (Multi-IPAD) following high-performance liquid chromatography (HPLC) was applied for the determination of tetracyclines (TCs) including dimethyltetracycline (DMTC), oxytetracycline (OTC) and tetracycline (TC). The key advantages of the Multi-IPAD are the abilities to enhance sensitivity and reproducibility and the ability to keep working electrode clean through the use of a high-frequent waveform alteration in integration step and the use of a cleaning potential, which is quite different from conventional three-step potential waveform. The analyses were carried out using the mobile phase of acetonitrile-water mixture solution (10:90, v/v) containing 1% perchloric acid on a C(18) column at a flow rate of 0.21 mL/min. The IPAD waveform parameters were optimized to maximize the signal-to-noise ratio (S/N) and successfully applied for the sensitive detection of TCs. The detection limits (S/N=3, 20 microL injected) were 0.07 mg/L for DMTC, 0.08 mg/L for OTC and 0.05 mg/L for TC. The peak height relative standard deviations (RSDs) of every compound for replicate injection (n=15) determined were below 4.6%.     

离子色谱中的安培检测方法及其应用

介绍了离子色谱中的安培检测方法(包括恒电位安培检测法、脉冲安培检测法和积分脉冲安培检测法)的原理和应用。脉冲安培检测法与高效阴离子交换色谱结合(HPAEC-PAD)是一种新的分析糖类化合物的方法;积分脉冲安培检测法与高效阴离子交换色谱结合(HPAEC-IPAD)是一种新的氨基酸分析方法。     

Determination of biogenic amines in alcoholic beverages by ion chromatography with suppressed conductivity detection and integrated pulsed amperometric detection

The determination of biogenic amines in alcoholic beverages is important to assess the potential risks associated with the consumption of high concentrations of these compounds. In addition, product storage conditions and the length of storage can cause the formation of biogenic amines that reduce product quality. We report a new method using cation-exchange chromatography with either suppressed conductivity, integrated pulsed amperometry, UV, or a combination of these detection techniques to determine biogenic amines in alcoholic beverages. The main objective was to provide a direct comparison between IPAD and suppressed conductivity detection for determining biogenic amines in alcoholic beverages. Suppressed conductivity is the simplest detection approach for determining putrescine, cadaverine, histamine, agmatine, phenylethylamine, spermidine, and spermine with good sensitivity (0.004-0.08 mg/l) and was used to evaluate the influence of storage time and conditions on the evolution of biogenic amines in alcoholic beverages. Integrated pulsed amperometric detection (IPAD) detects more biogenic amines than suppressed conductivity detection, enabling the detection of dopamine, tyramine, and serotonin. Tyramine was simultaneously determined by UV detection and IPAD to provide confirmation and ensure the accuracy of the analytical results. The linearity of biogenic amine responses was within 0.1-20 mg/l and peak area precisions were 0.24-4.97% for IPAD, suppressed conductivity-IPAD, and UV detection. The sensitivity for the 10 biogenic amines using the 3 detection techniques varied considerably from 0.004-1.1 mg/l and recoveries were within 85-122%.     

3D amperometry in the liquid chromatographic determination of trace pharmaceutical and herbicide emerging compounds

ABSTRACT

In this work, we innovatively applied the 3D amperometry detection, coupled to liquid chromatography, for the determination of a mixture of chromatographically unresolved compounds (two herbicides—monuron and bentazon, one drug—propranolol and the main metabolite of an antiepileptic drug—5-(4?-hydroxyphenyl)-5-phenylhydantoin). Exploiting the post-chromatographic current integration, a scanning waveform was successfully applied to explore a wide range of potentials (0.0–1.3 V) to find the peculiar oxidative potential value for each compound. This approach allowed us to obtain 3D chromatograms (elution time vs potential vs current) in which coeluted species could be clearly distinguished.

Quantitation was easily obtained by extraction of 2D chromatograms (elution time vs integrated current), from the 3D ones, at the optimised waveform time ranges (800–1,000 msec and 1,500–1,700 msec, corresponding to 0.6–0.8 V and 1.0–1.2, respectively). Validation of the proposed 3D amperometry method was performed in terms of linearity, limits of detection and quantitation and repeatability. Matrix effect was studied by statistical treatment on a wastewater effluent. By coupling an on-line solid phase extraction step prior to separation and detection by 3D amperometry, detection limits were significantly reduced (57 ng/L for bentazon, with recovery yields of 82.9 ± 10.9%). It is worth mentioning that this value fully satisfies the requirements of the 98/83/CE directive for the determination of bentazon in groundwater.     

Use of disposable gold working electrodes for cation chromatography-integrated pulsed amperometric detection of sulfur-containing amino acids

We have prepared disposable thin-film gold working electrodes on polymeric substrates. Our microfabrication process allows for inexpensive and reproducible mass production of such electrodes. We utilize this new type of electrode in flow-through electrochemical cells to replace the conventional non-disposable gold working electrodes for integrated pulsed amperometric detection (IPAD) of compounds separated by high-performance cation-exchange chromatography. Using two S-containing amino acids (homocysteine and cysteine) as test compounds, we have modified a previously reported waveform for optimum performance with disposable gold electrodes. With the help of the same two test substances we have characterized the analytical performance of disposable gold electrodes under the new conditions. Compared to non-disposable working electrodes, the disposable working electrodes generated equal or better results in the limit of detection, linearity of calibration and reproducibility. When used with a new IPAD waveform, the disposable electrodes functioned reproducibly for 3 days. At the end of the specified usage period of 3 days, the disposable electrodes are simply replaced. Reconditioning by polishing is thus no longer required.     

反相高效液相色谱-脉冲电化学检测法测定重组人生长激素中异丙基-β-D-硫代半乳糖苷

采用反相高效液相色谱（RP-HPLC）-脉冲电化学检测（PED）法测定了重组人生长激素（rhGH）中的诱导剂异丙基-β-D-硫代半乳糖苷（IPTG）。rhGH样品经超滤离心后,用超纯水提取,经C18色谱柱分离,用脉冲电化学器检测。结果表明,样品中添加0.02~0.10 mg/L的IPTG,其回收率为100%~102%,相对标准偏差（n=3）小于10%。在优化的条件下,IPTG的检出限可达1 μg/L（0.1 pmol,25 μL）。该方法简便高效,具有良好的灵敏度、回收率和重复性。     

Comparison of pulsed amperometric detection and integrated voltammetric detection for inorganic sulfur compounds in liquid chromatography

A Variety of potential–time waveforms are useful in pulsed electrochemical detection (PED) when applied for the amperometric detection of numerous polar organic compounds following their separation by liquid chromatography (LC). Here, we compare the waveforms for pulsed amperometric detection (PAD) and integrated voltammetric detection (IVD) applied for detection of organosulfur compounds at Au electrodes in acidic media. In PAD waveforms, electrodes response is measured at a constant detection potentials. In IVD waveforms, electrodes current is integrated throughout a fast cyclic scan of the detection potential. As a consequence of this difference in detection strategy, the background signal for IVD is significantly smaller for PAD in the detection of organosulfur compounds whose response mechanisms require the concomitant formation of surface oxides on Au electrodes. Furthermore, in comparison to Pad, IVD has a larger sensitivity and a diminished system peak from 0₂ dissolved in the sample. Use of a preadsorption step increases detection sensitivity in both PAD and IVD. The limit of detection (S/N=3)for cysteine in LC-IVD is ca. 6 nM for a 50-μl injection (i.e., 300 fmol) using a detection waveform that includes a 1000-ms preadsorption period.     

A pulsed potential waveform displaying enhanced detection capabilities towards sulfur-containing compounds at a gold working electrode

Pulsed electrochemical detection of sulfur-containing compounds was successfully investigated by applying a four-step potential waveform at a gold working electrode. This potential waveform called APAD, which stands for activated pulsed amperometric detection, is composed of an activation potential step added to a conventional three-step potential waveform. A key advantage of the APAD at the Au electrode is the ability to enhance sensitivity through the use of a short potential pulse (E(ACT) = +750 mV versus Ag/AgCl and tACT approximately 90 ms) during which the formation of redox active species (presumably OH*) are able to efficiently oxidize organosulfur compounds. The APAD waveform parameters were optimized to maximize the signal-to-noise ratio (S/N) and successfully applied for the sensitive detection of lipoic acid, biotin, iminobiotin, methionine, cystine, cysteine, homocysteine, homocystine, N-acetylcysteine and glutathione, following their separations by high-performance anion-exchange chromatography (HPAEC) using alkaline mobile phases. The detection limits (S/N = 3, 10 microL injected) ranged from 0.3 for cysteine (400 pg) to 0.02 micromol/L for biotin (50 pg) and methionine (30 pg). The response of sulfur-, amine- and alcohol-based compounds was compared by using four selected pulsed potential waveforms. It was found that the APAD exhibits excellent sensitivity for thiocompounds outperforming all other pulsed potential waveforms. Ratios of the peak areas for APAD and the six-step potential integrated waveform increased from 3.2 +/- 0.4 to 13.5 +/- 0.6 for lipoic acid and biotin, respectively.     

Determination of several sugars in serum by high-performance anion-exchange chromatography with pulsed amperometric detection

In this paper, a sensitive, simple and direct method for simultaneous determination of glucose, ribose, isomaltose and maltose in serum sample by high-performance anion-exchange chromatography coupled with integrated pulsed amperometric detection was developed. The four target analytes were easily and completely separated on an anion-exchange column at a flow-rate of 0.25 mL/min by binary step gradient elution in about 16 min and the two eluents were deionized water and 500 mM sodium hydroxide, respectively. The separated four analytes were detected directly by using a gold electrode and quadruple-potential waveform integrated pulsed amperometry without derivatization. Under the optimized conditions, when the injection volume was 25 microL, the detection limits (signal-to-noise ratio equal to 3) for glucose, ribose, isomaltose and maltose were 0.92, 7.50, 12.9 and 10.3 ng/mL, respectively. The calibration graphs of peak area for the four analytes were linear over two to three orders of magnitude with correlation coefficients greater than 0.998. R.S.D. of peak areas of the four analytes for five determinations were no more than 5.6%. The analytical method had been applied to the determination of glucose, ribose, isomaltose and maltose in real serum samples and good results with low relative standard deviation not more than 5.3% were obtained. The accuracy of the proposed method was tested by recovery measurements on spiked samples and good recovery results (98.1-107.9%) were obtained.     

离子色谱-积分脉冲安培法测定肉类产品中鹅肌肽、高肌肽及肌肽

建立了一种离子色谱-积分脉冲安培（IC-IPAD）同时测定肉类样品中鹅肌肽、高肌肽及肌肽的分析方法。方法采用高效阴离子交换色谱柱AminoPac PA10（250 mm×2 mm）分离,以100 mmol/L NaOH为淋洗液,流速为0.2 mL/min,柱温为30℃。结果表明,3种目标化合物在15 min内可实现完全分离,且17种氨基酸对3种目标化合物不存在干扰。在最佳色谱条件下,鹅肌肽、高肌肽及肌肽在0.05~5.0 mg/L范围内呈良好的线性关系,线性相关系数（r）>0.99。3种目标化合物的检出限和定量限分别为8.9~22.1 μg/L和29.6~73.6 μg/L。对鸭胸及鹅胸样品进行分析,加标回收率为92.4%~104.5%。该方法简单方便,无需衍生化,灵敏度高,可用于肉类产品中相关营养成分的测定。     

液相色谱中的安培检测

介绍了液相色谱中直流安培、脉冲安培和积分安培检测的基本原理及使用条件和范围。     

Direct amino acid analysis method for speciation of selenoamino acids using high-performance anion-exchange chromatography coupled with integrated pulsed amperometric detection

Speciation analysis of selenomethylcysteine (SeMeCys), selenomethionine (SeMet) and selenocystine (SeCys) has been performed using a direct amino acid analysis method with high-performance anion-exchange chromatography (HPAEC) coupled with integrated pulsed amperometric detection (IPAD). Three selenoamino acids could be baseline-separated from 19 amino acids using gradient elution conditions for amino acids and determined under new six-potential waveform. Detection limits for SeMeCys, SeMet and SeCys were 0.25, 1 and 20 microg/L (25 microL injection, 10 times of the baseline noise), respectively. The relative standard deviations (RSDs) of 200 microg/L SeMeCys, SeMet and SeCys were 3.1, 4.1 and 2.8%, respectively (n=9, 25 microL injection). The proposed method has been applied for determination of selenoamino acids in extracts of garlic and selenious yeast granule samples. No selenoamino acids were found in garlic. Both SeMet and SeCys were detected in selenious yeast tablet with the content of 45 and 129 microg Se/g, respectively. Selenoamino acids standards were spiked in garlic and yeast granule samples and the recovery ranged from 90 to 106%.     

Determination of zidovudine using anion exchange chromatography with integrated pulsed amperometric detection

A rapid and practical method for direct detection of zidovudine in high performance anion exchange chromatography(HPAEC) has been developed with integrated pulsed amperometric detection(IPAD).Dionex AS 18(250 mm×2 mm) and AG 18 (50 mm x 2 mm) columns and 11 mmol/L NaOH solution were used for separation.Multi-step potential waveform parameters were optimized to maximize the signal-to-noise ratio(S/N).Utilizing an optimized waveform,the repeatability(intra-day) precision and intermediate(inter-day) precision are obtained with relative standard deviation(RSD) of 1.88,2.27,respectively.The limit of quantification(LOQ) and limit of detection(LOD) were found to be 9.70,3.0 ng/mL,respectively,with correlation coefficients of 0.9992 over concentration range 0.01-10μg/mL.The present method was successfully applied to the determination of zidovudine in human plasma.The recoveries of plasma sample spiked by 0.7μg/mL,2.7μg/mL obtained were 95.3-101.5%, with relative standard deviation(RSD) of 2.54%,2.21%,respectively.     

离子色谱积分脉冲安培法同时测定血浆中阿仑膦酸钠、帕米膦酸钠、伊班膦酸钠和利塞膦酸钠

建立了离子色谱积分脉冲安培检测器(IPAD)同时检测血浆中阿仑膦酸钠、帕米膦酸钠、伊班膦酸钠和利塞膦酸钠的方法。采用Dionex AS18 (250 mm×2 mm)和AG18 (50 mm×2 mm)色谱柱在24 mmol/L NaOH溶液中进行分离;对多电位波形参数优化以达到最大信噪比;采用优化后的波形方法对4种双膦酸盐类药物进行检测,具有良好的线性(r2为0.9972～0.9995)和重现性(峰面积的相对标准偏差(RSD)为0.84%～1.37%)及较高的灵敏度(检出限为0.061～0.18 μg/mL)。4种双膦酸盐在该方法中有很好的保留且有较好的分离度,与之前报道的衍生后检测方法相比,该方法不用衍生,更简单而易于操作。将该方法成功地用于人体血浆中双膦酸盐类的检测,其回收率为80.81%～97.32%, RSD为1.46%～3.02%。     

Flow injection analysis of doxycycline or chlortetracycline in pharmaceutical formulations with pulsed amperometric detection

A flow injection with pulsed amperometric detection for determination of doxycycline or chlortetracycline in pharmaceutical formulations is described. Doxycycline or chlortetracycline were studied at a gold rotating disk electrode with cyclic voltammetry as a function of pH of supporting electrolyte solution. The optimized PAD waveform parameters were obtained with a flow injection system. The optimized pulsed conditions of doxycycline were 1150 mV (versus Ag/AgCl reference electrode) detection potential (E_det) for 220 ms (150 ms delay time and 70 ms integration time), 1500 mV (versus Ag/AgCl reference electrode) oxidation potential (E_oxd) for 70 ms oxidation time (t_oxd) and 250 mV (versus Ag/AgCl reference electrode) reduction potentail (E_red) for 400 ms reactivation time (t_red). The optimized pulsed conditions of chlortetracycline were 1050 mV (versus Ag/AgCl reference electrode) detection potential (E_det) for 300 ms (200 ms delay time and 100 ms integration time), 1300 mV (versus Ag/AgCl reference electrode) oxidation potential (E_oxd) for 70 ms oxidation time (t_oxd) and 250 mV (versus Ag/AgCl reference electrode) reduction potentail (E_red) for 400 ms reactivation time (t_red). The optimized PAD waveform was applied to the determination of doxycycline hydrochloride and chlortetracycline hydrochloride standard solution and in pharmaceutical formulations. The linear dynamic ranges of doxycycline hydrochloride and chlortetracycline hydrochloride were 1 μM–0.1 mM. The sensitivity of this method was found to be 23 μA/mM for doxycycline hydrochloride and 33.76 μA/mM for chlortetracycline hydrochloride. The detection limit for both compounds is 1 μM. The doxycycline hydrochloride and chlortetracycline hydrochloride content in commercially available tablet dosage forms by the proposed method was comparable to those specified by the manufacturer.     

Determination of lisinopril using anion exchange chromatography with integrated pulsed amperometric detection

A rapid and practical method for direct detection of lisinopril in anion exchange chromatography(AEC) has been developed with integrated pulsed amperometric detection(IPAD).Dionex AS 18(250 mm×2 mm) and AG 18(50 mm×2 mm) columns and 40 mmol/L NaOH solution were used for separation.Multi-step potential waveform parameters were optimized to maximize the signal-to-noise ratio(S/N).Utilizing the optimized waveform,the repeatability(intra-day) precision and intermediate(inter-day) precision were obtained with relative standard deviation(RSD) of 0.74,0.93,respectively.The limit of quantification(LOQ) and limit of detection(LOD) were found to be 0.37,0.12ng/mL,respectively,with the correlation coefficient of 0.9998 over concentration range 0.01-1μg/mL.The present method was successfully applied to the determination of lisinopril in human plasma.The recoveries of plasma sample spiked by 0.2μg/mL,0.8μg/mL lisinopril were 98.31-103.23%with RSD of 1.41%, 0.61%,respectively.     

Analysis of carbohydrates by anion exchange chromatography and mass spectrometry

A versatile liquid chromatographic platform has been developed for analysing underivatized carbohydrates using high performance anion exchange chromatography (HPAEC) followed by an inert PEEK splitter that splits the effluent to the integrated pulsed amperometric detector (IPAD) and to an on-line single quadrupole mass spectrometer (MS). Common eluents for HPAEC such as sodium hydroxide and sodium acetate are beneficial for the amperometric detection but not compatible with electrospray ionisation (ESI). Therefore a membrane-desalting device was installed after the splitter and prior to the ESI interface converting sodium hydroxide into water and sodium acetate into acetic acid. To enhance the sensitivity for the MS detection, 0.5 mmol/l lithium chloride was added after the membrane desalter to form lithium adducts of the carbohydrates. To compare sensitivity of IPAD and MS detection glucose, fructose, and sucrose were used as analytes. A calibration with external standards from 2.5 to 1000 pmole was performed showing a linear range over three orders of magnitude. Minimum detection limits (MDL) with IPAD were determined at 5 pmole levels for glucose to be 0.12 pmole, fructose 0.22 pmole and sucrose 0.11 pmole. With MS detection in the selected ion mode (SIM) the lithium adducts of the carbohydrates were detected obtaining MDL's for glucose of 1.49 pmole, fructose 1.19 pmole, and sucrose 0.36 pmole showing that under these conditions IPAD is 3-10 times more sensitive for those carbohydrates. The applicability of the method was demonstrated analysing carbohydrates in real world samples such as chicory inulin where polyfructans up to a molecular mass of 7000 g/mol were detected as quadrupoly charged lithium adducts. Furthermore mono-, di-, tri-, and oligosaccharides were detected in chicory coffee, honey and beer samples.     

Coupling Capillary Electrophoresis and Pulsed Electrochemical Detection

Pulsed electrochemical detection (PED) is an excellent method for detection of analytes that normally foul electrodes. In PED, the detection electrode is first cleaned at a high positive potential, then reactivated at a negative potential dissolving the surface oxide, and finally used to oxidize the analyte at a moderate positive potential. Due to the advantages and versatility of PED, many different variations of the detection waveform can be found in literature. This review focuses on application of PED to CE and in particular, the most commonly used modes: pulsed amperometric detection (PAD) and integrated pulsed amperometric detection (iPAD).