Analysis of trace inorganic anions in weak acid salts by single pump cycling‐column‐switching ion chromatography

The application of ion chromatography with the single pump cycling‐column‐switching technique was described for the analysis of trace inorganic anions in weak acid salts within a single run. Due to the hydrogen ions provided by an anion suppressor electrolyzing water, weak acid anions could be transformed into weak acids, existing as molecules, after passing through the suppressor. Therefore, an anion suppressor and ion‐exclusion column were adopted to achieve on‐line matrix elimination of weak acid anions with high concentration for the analysis of trace inorganic anions in weak acid salts. A series of standard solutions consisting of target anions of various concentrations from 0.005 to 10 mg/L were analyzed, with correlation coefficients r ≥ 0.9990. The limits of detection were in the range of 0.67 to 1.51 μg/L, based on the signal‐to‐noise ratio of 3 and a 25 μL injection volume. Relative standard deviations for retention time, peak area, and peak height were all less than 2.01%. A spiking study was performed with satisfactory recoveries between 90.3 and 104.4% for all anions. The chromatographic system was successfully applied to the analysis of trace inorganic anions in five weak acid salts.     

整体柱离子相互作用色谱快速分析无机阴离子

研究了用硅胶整体柱和直接电导检测的离子相互作用色谱快速分析常见无机阴离子的方法。实验采用氢氧化四丁铵和邻苯二甲酸为淋洗液,讨论了包括淋洗液浓度、流速和pH对分离的影响。当以1.5 mmol/L氢氧化四丁铵和1.1 mmol/L邻苯二甲酸为淋洗液(pH 5.5),流速6 mL/min时,可以在1 min内分离Cl-、NO2-、Br-、NO3-、ClO3-、SO42-和I-7种阴离子。方法的检出限为0.3~1.9 mg/L,峰面积、峰高的相对标准偏差(RSD,n=5)分别为0.4%~2.2%和0.1%~1.5%。将该法用于测定矿泉水和地下水中的阴离子,加标回收率在97.9%~100.3%之间。     

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。     

Silica‐particle‐supported zwitterionic polymer monolith for microcolumn liquid chromatography

A silica‐particle‐supported zwitterionic polymeric monolithic column, shortened as supported column (S‐column), was prepared by the in situ polymerization of methacrylic acid, ethylene dimethacrylate, and 2‐(dimethylamino)ethyl methacrylate in the presence of a ternary porogenic solvent containing water, methanol, and cyclohexanol in a 250 μm id fused‐silica capillary prepacked with 5 μm bare silica particles. In the S‐column, a thin layer of the polymers was formed around the silica particles in the form of nanoglobules, leaving the interstitial spaces between the particles free for liquid flow. The effects of the preparation conditions on the morphology of the monolith were investigated by scanning electron microscopy and backpressure measurements. The selected volumetric ratio of porogens, monomer concentration, polymerization time, and temperature are 1:1:8 (water/methanol/cyclohexanol), 25% v/v, 5 h, and 60°C, respectively. The S‐column was evaluated by comparison with its conventional organic counterpart in terms of morphology, mechanical stability, permeability, swelling–shrinking behavior, capacity, and efficiency. The results demonstrate that the S‐column is superior to its counterpart in all the terms with the exception of permeability. The above merits and zwitterionic property of the S‐column were further confirmed by separate separations of four inorganic anions and three organic cations.     

Development of a sequential injection chromatography (SIC) method for determination of simazine,atrazine, and propazine

This paper describes the development of a sequential injection chromatography (SIC) procedure for separation and quantification of the herbicides simazine, atrazine, and propazine exploring the low backpressure of a 2.5 cm long monolithic C₁₈ column. The separation of the three compounds was achieved in less than 90 s with resolution >1.5 using a mobile phase composed by ACN/1.25 mmol/L acetate buffer (pH 4.5) at the volumetric ratio of 35:65 and flow rate of 40 μL/s. Detection was made at 223 nm using a flow cell with 40 mm of optical path length. The LOD was 10 μg/L for the three triazines and the quantification limits were of 30 μg/L for simazine and propazine and 40 μg/L for atrazine. The sampling frequency is 27 samples per hour, consuming 1.1 mL of ACN per analysis. The proposed methodology was applied to spiked water samples and no statistically significant differences were observed in comparison to a conventional HPLC–UV method. The major metabolites of atrazine and other herbicides did not interfere in the analysis, being eluted from the column either together with the unretained peak, or at retention times well‐resolved from the studied compounds.     

Determination of common inorganic anions and cations by non-suppressed ion chromatography with column switching

An ion chromatography (IC) method has been proposed for the determination of seven common inorganic anions (F(-), H(2)PO(4)(-), NO(2)(-), Cl(-), Br(-), NO(3)(-), and SO(4)(2-)) and/or five common inorganic cations (Na(+), NH(4)(+), K(+), Mg(2+), and Ca(2+)) using a single pump, a single eluent and a single detector. The present system used cation-exchange and anion-exchange columns connected in series via a single 10-port switching valve. The 10-port valve was switched for the separation of either cations or anions in a single chromatographic run. When 1.0mM trimellitic acid (pH 2.94) was used as the eluent, the seven anions and the five cations could be separated on the anion-exchange column and the cation-exchange column, respectively. The elution order was found to be F(-)相似文献   

Determination of cyanobacterial cyclic peptide hepatotoxins in drinking water using CE

Four cyanobacteria hepatotoxins microcystin LR, microcystin RR, microcystin YR, and nodularin were simultaneously determined in drinking water using CZE and MEKC coupled with UV detection. The toxins were satisfactorily separated in both CZE and MEKC modes. Detection limits were in the range of 0.82–4.81 μg/mL, with R² values of 0.994–0.999. The linearity range tested for the standards was 5–100 μg/mL and RSD percentages were in the range of 1.0–2.5% for retention time and 3.0–10.2% for peak area. When a known amount of standard was spiked into a known volume of water and extracted, recoveries were 90.3% (RR), 101.5% (nodularin), 90.6% (YR), and 88.2% (LR). The use of SPE enabled cleanup and pre‐concentration of a real sample to achieve a 100‐fold concentration factor. Detection limits after SPE of the real sample spiked with microcystins were 0.090 μg/L (RR), 0.076 μg/L (YR), and 0.110 μg/L (LR), with RSD percentage values of 9.9–11.7% for peak area and 2.2–3.3% for retention time. The technique developed provides an alternative method for determining microcystins at levels of concentration that will be able to meet WHO drinking water guidelines for microcystins.     

Determination of monovalent inorganic anions in high-ionic-strength samples by electrostatic ion chromatography with suppressed conductometric detection

A new ion chromatographic (IC) system has been established by using micelles of 3-(N,N-dimethylmyristylammonio)propanesulfonate (Zwittergent 3-14) loaded onto a reversed-phase packed column as the separation column with an electronic rotary switching valve packed-bed suppressor for conductometric detection of inorganic anions. An aqueous H3BO3-Na2B4O7 solution has been demonstrated to be the most desirable eluent for this IC system. The relationship between retention time and the concentration of the borate eluent was determined for a series of model anionic analytes and this relationship was found to be opposite to that exhibited in a conventional anion-exchange IC system. The rapid elution and complete separation of monovalent inorganic anions were obtained by initially using a high-concentration borate solution as the eluent for a short-period, and then switching to a lower-concentration borate eluent to complete the separation. Detection limits for nitrite, bromide, nitrate, and chlorate were 0.85, 0.88, 0.95 and 4.8 microM, respectively, when a 7.0 mM Na2B4O7 eluent was used. Moreover, the ability to directly detect these monovalent anions in samples containing high concentrations of sulfate and/or chloride ions provided a major advantage of this approach.     

亲水作用色谱柱与阳离子交换树脂柱结合分离无机离子（英文）

A combination of hydrophilic interaction chromatographic(HILIC) column and a weakly acidic cation-exchange resin(WCX) column was used for simultaneous separation of inorganic anions and cations by ion chromatography(IC).Firstly,the capability of HILIC column for the separation of analyte ions was evaluated under acidic eluent conditions.The columns used were SeQuant ZIC-HILIC(ZIC-HILIC) with a sulfobetaine-zwitterion stationary phase(ZIC-HILIC) and Acclaim HILIC-10 with a diol stationary phase(HILIC-10).When using tartaric acid as the eluent,the HILIC columns indicated strong retentions for anions,based on ion-pair interaction.Especially,HILIC-10 could strongly retain anions compared with ZIC-HILIC.The selectivity for analyte anions of HILIC-10 with 5 mmol/L tartaric acid eluent was in the order of I-> NO-3 > Br-> Cl-> H2PO-4.However,since HILIC-10 could not separate analyte cations,a WCX column(TSKgel Super IC-A/C) was connected after the HILIC column in series.The combination column system of HILIC and WCX columns could successfully separate ten ions(Na+,NH+4,K+,Mg2+,Ca2+,H2PO-4,Cl-,Br-,NO-3 and I-) with elution of 4 mmol/L tartaric acid plus 8 mmol/L 18-crown-6.The relative standard deviations(RSDs) of analyte ions by the system were in the ranges of 0.02%-0.05% in retention times and 0.18%-5.3% in peak areas through three-time successive injections.The limits of detection at signal-to-noise ratio of 3 were 0.24-0.30 μmol/L for the cations and 0.31-1.2 μmol/L for the anions.This system was applied for the simultaneous determination of the cations and the anions in a vegetable juice sample with satisfactory results.     

Determination of inorganic anions in natural water by microcolumn ion chromatography with on-column enrichment.

An on-column enrichment method was developed for the rapid determination of inorganic anions in natural water. The system was assembled from a syringe pump, a six-port switching valve with a sample-enrichment loop, a separation column and a UV detector. The enrichment efficiency of the system was tested by using inorganic anions as samples. The limits of detection were between 0.6 and 7.7 microg/L. The system was applied to the determination of anions in river and pond-water samples.     

Effect of Column Temperature on the Retention of Inorganic Anions and Organic Acids in Non-Suppressed Anion-Exchange IC

An investigation has been conducted into the effect of column temperature on the retention of inorganic anions and organic acids in non-suppressed ion chromatography on an anion-exchange column. Potassium biphthalate and p-hydroxybenzoic acid–tris–boric acid were used as mobile phases. The column temperature was from 25 to 50 °C. Endothermic and exothermic retention of inorganic anions were both observed when potassium biphthalate was used as mobile phase. When p-hydroxybenzoic acid–tris–boric acid was used as mobile phase, however, endothermic behavior only was observed. Moreover, for the two mobile phases, variation of the retention time of the system peaks with changing temperature was reversed. For retention of the organic acids, only endothermic behavior was observed with the two mobile phases. Variation of retention time was greater when p-hydroxybenzoic acid–tris–boric acid was used as mobile phase than when potassium biphthalate was used. These results indicated the exchange reaction in anion-exchange chromatography could be either endothermic or exothermic, depending on the solute and mobile phase ions involved. Different relative changes of retention time were observed for individual inorganic anions and organic acids with increasing column temperature. In general, variation of retention time with increasing temperature was greater for strongly retained inorganic anions and organic acids than for weakly retained species. Van’t Hoff plots for inorganic anions, organic acids, and system peaks were linear. Selectivity variation of the retention of inorganic anions and organic acids was achieved by changing the temperature. In achieving optimum separation of inorganic anions and organic acids, temperature was a valuable tool. To reduce the retention times of the ions and avoid interference from system peaks in non-suppressed anion-exchange ion chromatography with the two mobile phases, a low column temperature, for example, 35 °C, was best.     

A single pump column-switching technique coupled with polystyrene-divinylbenzene-carbon nanotubes column for the determination of trace anions in different concentrated organic matrices by ion chromatography

An ion chromatographic method with on-line sample pretreatment was developed for the trace analysis of seven common anions in concentrated matrices. The pretreatment column used in this study consisted of polystyrene-divinylbenzene (PS-DVB) and multi-walled carbon nanotubes (MWCNTs). It was too hydrophobic to retain different inorganic anions, but it showed a strong affinity for organic compounds. Thus, this chromatographic system could be used to detect trace anions in organic solvents, organic acids and relevant salts. The addition of MWCNTs decreased the surface areas of stationary phases and the retention times of organic matrices were shortened. Compared with conventional column-switching technique, only a single instrument (ICS2100) was needed in this system, including a pump, a conductivity detector, an eluent generator, a six-port valve and a ten-port valve. An electrochemical self-generating suppressor (ESGS) was adopted to convert the eluent of KOH into water for the matrix elimination. Two different eluent were employed in the chromatographic system, one for separation and the other for matrix elimination. The sample pretreatment and analysis were realized simultaneously. After optimization of this system, a calibration study was conducted by preparing and analyzing eight concentrations (between 5 and 5000 μg L(-1)) of mixture standards of seven anions in deionized water. The linearity was between 0.9990 and 0.9998, and the detection limits ranged from 0.41 to 3.17 μg L(-1). A spiking study was performed on three representative organic chemicals with satisfactory recoveries between 88.1% and 118.5% when the concentrations of the matrices did not exceed 10 g L(-1).     

High‐resolution peptide separations using nano‐LC at ultra‐high pressure

We report on the optimization of nano‐LC gradient separations of proteomic samples that vary in complexity. The gradient performance limits were visualized by kinetic plots depicting the gradient time needed to achieve a certain peak capacity, while using the maximum system pressure of 80 MPa. The selection of the optimal particle size/column length combination and corresponding gradient steepness was based on scouting the performance of 75 μm id capillary columns packed with 2, 3, and 5 μm fully porous silica C18 particles. At optimal gradient conditions, peak capacities up to 500 can be obtained within a 120 min gradient using 2 μm particle‐packed capillary columns. Separations of proteomic samples including a cytochrome c tryptic digest, a bovine serum albumin tryptic digest, a six protein mix digest, and an Escherichia coli digest are demonstrated while operating at the kinetic‐performance limit, i.e. using 2‐μm packed columns, adjusting the column length and scaling the gradient steepness according to sample complexity. Finally, good run‐to‐run retention time stability (RSD values below 0.18%) was demonstrated applying ultra‐high pressure conditions.     

Trace determination of perchlorate using electromembrane extraction and capillary electrophoresis with capacitively coupled contactless conductivity detection

Electromembrane extraction (EME) and CE with capacitively coupled contactless conductivity detection (CE‐C⁴D) was applied to rapid and sensitive determination of perchlorate in drinking water and environmental samples. Porous polypropylene hollow fiber impregnated with 1‐heptanol acted as a supported liquid membrane (SLM) and perchlorate was transported and preconcentrated in the fiber lumen on application of electric field. High selectivity of perchlorate determination and its baseline separation from major inorganic anions was achieved in CE‐C⁴D using background electrolyte solution consisting of 7.5 mM L ‐histidine and 40 mM acetic acid at pH 4.1. The analytical method showed excellent parameters in terms of reproducibility; RSD values for migration times and peak areas at a spiked concentration of 15 μg/L of perchlorate (US EPA recommended limit for drinking water) were below 0.2 and 8.7%, respectively, in all examined water samples. Linear calibration curves were obtained for perchlorate in the concentration range 1–100 μg/L (r²≥0.999) with limits of detection at 1 μg/L for tap water and at 0.25–0.35 μg/L for environmental and bottled potable water samples. Recoveries at 15 μg/L of perchlorate were between 95.9 and 106.7% with minimum and maximum recovery values for snow and bottled potable water samples, respectively.     

Simultaneous Determination of Palladium and Platinum by On‐Line Enrichment Followed by Rapid Column High Performance Liquid Chromatography

In this paper, a new method for the simultaneous determination of palladium and platinum ions was developed using a rapid column high performance liquid chromatograph equipped with an on‐line enrichment technique. The palladium and platinum ions were pre‐column derivatized with 5‐(p‐aminobenzylidene)‐thiorhodanine (ABTR) to form colored chelates. The Pd‐ABTR, Pt‐ABTR chelates can be absorbed onto the front of an enrichment column when they were injected into the injector and sent to the enrichment column [ZORBAX Stable Bound, 4.6 × 10 mm, 1.8 μm] with a buffer solution of 0.05 mol/L sodium acetate‐acetic acid buffer solution (pH 3.5) as mobile phase. After the enrichment had finished, by switching the six‐ports switching valve, the retained chelates were back‐flushed by mobile phase and traveled towards the analytical column. These chelates separation on the analytical column [ZORBAX Stable Bound, 4.6 × 50 mm, 1.8 μm] was satisfactory with 65% methanol (containing 0.05 mol/L of pH 3.5 sodium acetate‐acetic acid buffer salt and 0.01 mol/L of tritonX‐100) as mobile phase. The palladium and platinum were separated completely within 2 min. The detection limits (S/N = 3) of palladium and platinum are 1.4 ng/L and 1.6 ng/L, respectively. This method was applied to the determination of palladium and platinum in water and urine samples with good results.     

Development of packed-column suppressor system for capillary ion chromatography and its application to environmental waters

A novel suppressor unit for capillary ion chromatography was designed to reduce the background conductivity and at the same time to increase the analyte signal. Regeneration of the suppressor was carried out on-line by passing an appropriate acidic solution through the column to displace the accumulated eluent cations. By using two 6-port microswitching valves and two packed capillary column suppressors, the background conductivity of sodium carbonate-bicarbonate mobile phase was maintained at low conductivity for continuous chromatographic runs, and the detection limits at low ppb levels were achieved. The relative standard deviations (RSDs) for the retention time, peak area and peak height of six common inorganic anions (0.05mM each of F(-), Cl(-), NO(2)(-), Br(-), NO(3)(-) and SO(4)(2-)) were between 0.5-0.9, 1.1-4.6 and 0.7-4.9%, respectively. The present system was successfully applied to the determination of inorganic anions in river water and tap water samples.     

离子交换色谱法同时测定啤酒中有机酸和无机阴离子

建立了用亲水性阴离子交换分离柱,KOH为淋洗液等浓度泵作梯度淋洗,电导检测,同时分离和检测16种无机阴离子和低分子量有机酸的离子色谱法。方法对所测无机阴离子和有机酸检出限在9．3～32μg/L之间;线性范围均在2个数量级以上;回收率在90．2％～107．2％之间。方法用于啤酒样品的分析,结果满意,样品的RSD小于5．3％(n=7)。     

Determination of iodide in seawater using C30 column modified with polyoxyethylene oleyl ether in ion chromatography

An ion chromatographic method for rapid and direct determination of iodide in seawater samples is reported. Separation was achieved using a laboratory-made C30 packed column (100 mm × 0.32 mm i.d.) modified with polyoxyethylene oleyl ether, with an aqueous solution of 300 mM sodium chloride as eluent and using UV detection at 220 nm. Samples containing iodate, nitrate, iodide and thiocyanate were eluted within 8 min, and the relative standard deviations of the retention time, peak area and peak height were all smaller than 4.19% for all of the analyte anions. Effects of eluent composition on retention behavior of inorganic anions have been investigated. Both cation and anion of the eluent affected the retention time of analytes. When inorganic eluents, such as ammonium chloride, ammonium sulfate, lithium chloride, sodium chloride, sodium sulfate, magnesium chloride and magnesium sulfate were used, the retention time of analytes increased with increasing eluent concentration. The limit of detection of iodide was 19 μg l⁻¹ (S/N = 3), while the limit of quantitation was 66 μg l⁻¹ (S/N = 10). The present method was successfully applied to the rapid and direct determination of iodide in seawater samples.     

Tunable separation of anions and cations by column switching in ion chromatography

A convenient ion chromatography method has been proposed for the routine and simple determination of anions (Cl⁻, SO₄²⁻ and NO₃⁻) and/or cations (Na⁺, NH₄⁺, K⁺, Mg²⁺ and Ca²⁺) using a single pump, a single eluent and a single detector. The present system used cation-exchange and anion-exchange columns connected in series via two 6-port switching valves or a single 10-port valve. The connection order of the ion-exchange columns could be varied by switching the valve(s). The present system therefore allowed the separation of either cations or anions in a single chromatographic run. While one ion-exchange column is being operated, the other ion-exchange column is being conditioned, i.e., the columns are always ready for analysis at any time. When 2.4 mM 5-sulfosalicylic acid was used as the eluent, the three anions and the five cations could be separated on the anion-exchange column and cation-exchange column, respectively. In order to obtain the separations of the target ions, the injection valve was placed between the two columns. Complete separations of the above anions or cations were demonstrated within 10 min each. The detection limits at S/N = 3 were 19-50 ppb (μg/l) for cations and 10-14 ppb for anions. The relative standard deviations of the analyte ions were less than 1.1, 2.9 and 2.8% for retention time, peak area and peak height, respectively. This proposed technique was applied to the determination of common anions and cations in river water samples.     

原子转移自由基聚合法制备新型亲水作用色谱固定相及其性能评价

以自制的6.0μm单分散大孔交联聚氯甲基苯乙烯-二乙烯基苯(Poly(4-vinylbenzylchloride-co-divi-nylbenzene),PCMS/DVB)微球为基质和引发剂,CuCl和自行合成的三[(2-二甲基氨基)乙基]胺(Tris[2-(dimeth-ylamino)ethyl]amine,Me6TREN)组成混合催化体系,使4-乙烯基吡啶(4-Vinyl pyridine,4-VP)在甲苯中进行原子转移自由基聚合,制得4-乙烯基吡啶聚合物,单体4-乙烯基吡啶的接枝率为8.55%。将该聚合物与正溴丁烷反应制得新型亲水色谱固定相。在亲水作用色谱模式下,流速1 mL/min,乙腈-水为流动相可分离5种芳胺化合物和4种酚类化合物。在离子交换色谱模式下,6 mmol/L Na2CO3-5.5 mmol/L NaHCO3为淋洗液可分别分离5种无机阴离子和4种短链有机酸。结果表明,此固定相对极性化合物和无机阴离子具有良好的分离性能,是一种性能优异的亲水作用色谱固定相。