Studies on the separation of hydronium ion using surfactant-modified reversed-phase stationary phases and eluents containing an acidified electrolyte

A further investigation of a chromatographic system allowing determination of hydrogen ions is reported. For this purpose an octadecylsilica column dynamically modified with sodium dodecylsulfate (SDS) or lithium dodecylsulfate (LDS) was used as stationary phase and a slightly acidified electrolyte (usually KCl)-SDS solution was used as the eluent. The concentration of SDS, KCl and the acidity of the eluent affected the structure of aggregates formed by the molecules of dodecylsulfate at the surface of the stationary phase. These aggregates of dodecylsulfate were found to be responsible for the appearance of a chromatographic peak attributed to the presence of H3O+ ions in a sample. Other cations in the sample could be separated in the same manner, permitting the simultaneous separation of monovalent cations from H3O+. The detection limit for H3O+ ions was 2.25 x 10(-6) M using an eluent comprising 0.3 mM LDS, 50.0 mM KCl and 0.10 mM H2SO4. The proposed method is shown to be applicable for the determination of free H3O+ ions in aqueous solutions of strong acids.     

A novel ion chromatographic method based on cation-exchange and acid-base interactions for the simultaneous determination of total alkalinity and monovalent cations in samples of microliter volume

An ion chromatographic (IC) method based on the use of titrant (strong acid) as the stationary phase was developed for simultaneous determination of total alkalinity (TA) and monovalent cations. The titrant used in this study was obtained by initially loading lithium dodecylsulfate (Li-DS) onto a reversed-phase material and then conditioning the column with a slightly acidified aqueous LiCl solution (a mixture of 50.0 mM LiCl and 0.1 mM H2SO4). When a small amount of a basic sample was injected onto a column prepared in this way, the basic species (Bn-) reacted predominantly with H+ on the stationary phase and the reaction with the eluent phase was negligible due to the very low concentration of eluent H+ (in the eluent, a molar ratio of [Li+]/[H+] = 250:1 applied). The stationary phase H+ consumed in the acid-base reaction was then re-supplied by H+ from the eluent. By monitoring the conductance of the eluent using conductivity, an induced peak resulting from the basic species was observed. Calibration graphs of peak areas vs. molar concentration of the basic species for OH-, HCO3- and H2PO4- were found to be identical. CO3(2-), HPO4(2-), and B4O7(2-) also gave identical calibration curves but their slope values were twice those for HCO3-. The detection limit for HCO3- was less than 3.2 microM and the calibration curve was linear up to 12.3 mM (injection volume, 100 microL). Seawater was directly analyzed and its total alkalinity was found to be 2.87 mM (RSD 0.53%, n = 5), which was in good agreement with the result of 2.88 mM (RSD 3.2%, n = 5) obtained using auto-potentiometric titration. Na+ and K+ were determined simultaneously and the concentrations were 481.6 and 10.6 mM, respectively.     

Monolithic octadecylsilyl-silica gel column for the high-speed ion chromatographic determination of acidity

A monolithic ODS-silica gel column modified by saturating it with lithium dodecylsulfate (Li-DS) was used to demonstrate the high-speed separation of H+ from other mono- and divalent cations, such as Na+, NH4+, K+, Mg2+ and Ca2+ using ion chromatography (IC). Using a 5 mM EDTA-2K solution containing 0.10 mM Li-DS (pH 4.80) as eluent, H+ was eluted with a sharp and symmetrical peak within 1.0 min before other cations at a flow-rate of 1.5 ml min(-1). The rapid elution of H+ and its conductimetric detection could be attributed to the presence of EDTA (HY2-), which can convert H+ ions as anions. i.e. H(+) + H2Y(2-) --> H3Y(-). The acidity of rainwater and deionized water samples was determined using this IC system with satisfactory results.     

同时测定无机离子的改良离子色谱法在河水和废水质量监控中的应用（英文）

In this study,our recent work on advanced ion chromatographic methods for the simultaneous determination of inorganic ionic species such as common anions(SO2-4,Cl-and NO-3) and cations(Na+,NH+4,K+,Mg2+,and Ca2+),nutrients(phosphate and silicate) and hydrogen ion/alkalinity are summarized first.Then,the applications using these methods for monitoring environmental water quality are also presented.For the determination of common anions and cations with nutrients,the separation was successfully performed by a polymethacrylate-based weakly acidic cation-exchange column of TSKgel Super IC-A/C(Tosoh,150 mm×6.0 mm i.d.) and a mixture solution of 100 mmol/L ascorbic acid and 4 mmol/L 18-crown-6 as acidic eluent with dual detection of conductivity and spectrophotometry.For the determination of hydrogen ion/alkalinity,the separation was conducted by TSKgel ODS-100Z column(Tosoh,150 mm×4.5 mm i.d.) modified with lithium dodecylsulfate and an eluent of 40 mmol/L LiCl/0.1 mmol/L lithium dodecylsulfate/0.05 mmol/L H2SO4 with conductivity detector.The differences of ion concentration between untreated and treated wastewater showed the variation of ionic species during biological treatment process in a sewage treatment plant.Occurrence and distribution of water-quality conditions were related to the bioavailability and human activity in watershed.From these results,our advanced ion chromatographic methods have contributed significantly for water quality monitoring of environmental waters.     

Determination of total acidity and of divalent cations by ion chromatography with n-hexadecylphosphocholine as the stationary phase

An ion chromatographic (IC) method is reported for simultaneous determination of total acidity (H+), Ba2+, Ca2+, and Mg2+ in aqueous samples. A standard ODS silica column modified by coating with n-hexadecylphosphocholine was used as the separation column. Water alone was used as the eluent, with conductivity detection of the sample ions. An excess of sodium iodide was added to each sample so that both H+ and divalent cations were always eluted with iodide as the counterion. The elution order was Ba2+, Mg2+, Ca2+, and H+ with H+ being eluted much later than the divalent cations. Acetic acid and several other weak acids could also be separated because all the protons were transposed from acetic acid (HAc) to HI by the sodium iodide. Detection limits for 100 microl injection, S/N=3 were in the low micromolar range for the divalent cations and approximately 0.3 mM for H+/I-. This method was used successfully for simultaneous determination of total acidity, magnesium and calcium in HCl-type of hot-spring water.     

离子色谱法测定高氯、高钠油田回注水中的阴、阳离子及有机酸

建立了高氯、高钠油田回注水中痕量无机阴、阳离子和有机酸的离子色谱分析方法。对高钠基质中痕量阳离子的测定,选用IonPac CS12A分析柱、H2SO4溶液梯度淋洗、电导检测器检测;对高氯基质中阴离子及有机酸的测定,选用对OH-具有高选择性的高容量的IonPac AS11-HC柱、KOH梯度淋洗、电导检测器检测。在优化的梯度淋洗条件下,高氯或高钠的存在不影响痕量阴离子或阳离子的测定。该方法具有良好的线性(r=0.9926~0.9990)和精密度(测定组分峰面积的相对标准偏差(n=7)在8.0%以下),回收率     

Dodecylsulfate-coated monolithic octadecyl-bonded silica stationary phase for high-speed separation of hydrogen, magnesium and calcium in rainwater

The high-speed determination of hydrogen, magnesium and calcium ions by ion chromatography (IC) is demonstrated on a monolithic octadecyl-boned silica (ODS) column coated with lithium dodecylsulfate (Li-DS). This stationary phase, when used in conjunction with a 2 mM ethylenediamine and 0.1 mM Li-DS solution as eluent at pH 6.0, was found to be suitable for the rapid and efficient separation of hydrogen and magnesium and calcium in the order H+ < Mg2+ < Ca2+ within 4 min at a flow rate of 4.0 ml/min. Under the conditions, linear calibration plots of conductivity versus concentration were obtained for the cations over about three orders of magnitude, and the detection limits were 1 microM for H+, 2 microM for Mg2+ and Ca2+. Rainwater was analyzed directly using this IC system with satisfactory results.     

Chloride analysis in magnesium metal using ion chromatography with conductometric detection

A simple, rapid and accurate method for the determination of chloride in magnesium metal has been developed. The quantitative determination of chloride was accomplished by anion exchange chromatography with conductometric determination. A Metrosep Anion Dual 2 analytical column connected in series with a Metrosep RP guard column was used for chloride separation. A solution containing a mixture of 1.3 mM Na2CO3 and 2 mM NaHCO3 was used as eluent. The method requires a sample dissolution using nitric acid. The limit of detection for the determination of chloride is 50 mg kg(-1) and the relative standard deviation was 5% for the overall method. The recovery of chloride added was 99-102%. No interference was observed from either the closely eluting "system peak" or the nitrate peak in the determination of chloride.     

离子色谱法同时测定离子液体中的三氟乙酸根、氟硼酸根及卤素离子

采用离子色谱-直接电导检测法同时测定了离子液体中的三氟乙酸根(CF3COO~)、氟硼酸根(BF4~)及卤素离子(F~、Cl~、Br~)。实验采用Shim-pack IC-A3阴离子交换色谱柱,分别选用邻苯二甲酸氢钾、邻苯二甲酸+三(羟甲基)氨基甲烷、对羟基苯甲酸+三(羟甲基)氨基甲烷+硼酸为淋洗液,考察了淋洗液种类和浓度、乙腈浓度、色谱柱温度对分离测定三氟乙酸根、氟硼酸根及卤素离子的影响。确定的最佳色谱条件为: 以1.2 mmol/L邻苯二甲酸氢钾为淋洗液,柱温45 ℃,流速1.0 mL/min。在此条件下,可同时分离上述5种阴离子,且色谱峰形对称。所测阴离子的检出限(以信噪比为3计)为0.01～0.50 mg/L,保留时间和峰面积的相对标准偏差(n=5)分别不大于0.2%和1.2%。将方法应用于测定离子液体中的三氟乙酸根、氟硼酸根及卤素离子,加标回收率为98.0%～103.2%。该方法简单、准确、可靠,具有较好的实用性。     

High-resolution determination of H+ by ion chromatography. Application to the simultaneous determination of H+, Na+, NH4+ and K+ in acid rain.

An ion chromatographic (IC) method was developed for the high-resolution determination of a sample's free hydrogen ion concentration (H+). Highly purified lithium dodecyl sulfate was used as the stationary phase, a slightly acidified aqueous LiCl solution was used as the mobile phase and conductivity was used for analyte detection. An electrical double layer (EDL) containing H+ was established on the stationary phase by using a slightly acidified electrolyte solution as the eluent. H+ in the EDL protonated any weak acid groups (i.e., silanols) on the stationary phase so that H+ from the sample could be retained/separated purely by dodecyl sulfate. The optimum molar ratio of H+:Li+ in the EDL for this IC system was obtained by using an aqueous solution containing 40.0 mM LiCl and 0.07 mM H2SO4 as the eluent. After separation, H+ was detected by direct conductimetric measurement. An H+ detection limit of better than 8.2 x 10(-6) M was obtained from the analysis of standard aqueous H2SO4 solutions. Other monovalent cations could also be separated with this method, giving detection limits of 7.4 x 10(-5), 4.3 x 10(-5) and 4.2 x 10(-5) M for Na+, NH4+ and K+, respectively. The method was applied to the simultaneous determination of H+, Na+, NH4+ and K+ in acid rain. The results obtained showed a significant improvement in reproducibility when compared with those from a conventional pH-meter. Acid rain samples with a pH < 5 could be analyzed with this IC system.     

离子色谱-抑制电导法分别测定海水中阴离子和阳离子

采用离子交换-抑制电导法测定海水中阴、阳离子。采用抑制电导可以降低淋洗液的背景电导,又可以增加被测离子的电导值,改善信噪比。采用的电化学自身再生抑制器,由连续电解水产生抑制淋洗液所需要的H^＋或者OH^-,加上电场引力,能用于高客量分离柱所用的淋洗液浓度和梯度淋洗。在试验条件下,利用阴离子和阳离子分离柱,配合抑制电导检测,可以同时分离和测定海水中7种阴离子和6种阳离子。且都可以得到很好的线性和较低的检出限。     

A robust multisyringe system for process flow analysis. Part II. A multi-commuted injection system applied to the photometric determination of free acidity and iron(III) in metallurgical solutions

A new software-controlled volume-based system for sample introduction in process flow injection analysis was developed. By using a multi-syringe burette coupled with one or two additional commutation valves, the multi-commuted injection of precise sample volumes was accomplished. Characteristics and performance of the injection system were studied by injecting an indicator in a buffered carrier. Three configurations were implemented in order to achieve two different tasks: the single injection of a sample in a two- or three-channels manifold, and the dual injection into different streams. The two channel flow system using the single injection was applied to the determination of free acidity in diluted samples containing high levels of iron(III), by employing the single point titration methodology. The precipitation of ferric hydroxide was prevented using the ammonium and sodium salts of oxalate and acetate as buffer titrant. Methyl Red was employed as indicator. The procedure allows determination of acid concentration in solutions with a Fe(III)/H+ molar ratio up to 0.2. Samples with higher Fe(III)/H+ molar ratios were spiked with a known strong acid at dilution. The three-channel configuration was applied to the determination of ferric ions, using, as reagent, a merging mixture of sulfuric acid and potassium thiocyanate. The double injection system was implemented in series in a single (three-channel) manifold in such a way that a different injection volume and a changed reagent were used for each analyte. It was applied to the separated or sequential determination of free acidity and ferric ions. In this configuration, iron(III) was determined using 0.5-0.7% (w/v) sodium salicylate solution as reagent. The systems can operate at up to 100, 84 and 78 injections per hour, respectively. Determinations on synthetic and process samples compared well with the reference values and procedures. Recoveries of 95-102% with a maximum RSD value of 5.4% were found for acidity. The respective values obtained for iron determinations were 96-105% and 4.3%.     

离子液体中卤素离子杂质的离子色谱-直接电导检测法分析

研究了离子色谱-直接电导检测法分离测定离子液体中的卤素离子(F~-、Cl~-、Br~-)杂质.采用Shim-pack IC-A3阴离子交换色谱柱,考察了淋洗液种类及浓度、流速和色谱柱温度对分离测定的影响.最佳色谱条件为:以1.25 mmol/L邻苯二甲酸氢钾为淋洗液,流速1.5 mL/min,色谱柱温45 ℃.在此条件下可以基线分离卤素离子,且NO~-_3、BF~-_4、SO~(2-)_4不干扰测定.该法测定卤素离子的检出限(S/N=3)为0.02 ～0.11 mg/L,峰面积的相对标准偏差(n=5)不大于0.7%,F~-、Cl~- 和Br~- 的标准曲线的线性范围分别为0.1 ～50、0.1 ～50、0.5 ～100 mg/L.将方法用于烷基咪唑四氟硼酸盐离子液体中卤素离子杂质的测定,加标回收率为98% ～102%.     

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.     

Highly selective ion chromatographic determination of ammonium ions in waters with a suppressor as postcolumn reactor

A highly selective ion chromatographic method for the determination of ammonium ions using an anion-exchange separation column with a bipolar ion exchanger was developed. The method is based on the reaction in a suppressor column between ammonium ions and nitrous acid formed from the eluent components followed by the negative conductimetric signal. The determination of more than 0.1 ppm of NH₄⁺ in water is possible in the presence of 100-fold amounts of alkali metals and inorganic anions.     

碱化底液消除水负峰离子色谱法测定水中F~–,Cl~–等7种阴离子

在研究消除水负峰的基础上,建立离子色谱法测定水中F–,Cl–,NO2–,H2PO4–,Br–,NO3–,SO42–7种阴离子的方法。经实验确定淋洗液为4.5 mmol/L NaHCO3–4.0 mmol/L Na2CO3,淋洗液流量为1.0 mL/min,柱箱温度为35℃。在底液中加入与淋洗液同浓度的Na2CO3–NaHCO3可有效消除水负峰。该方法对7种阴离子的检出限为0.004~0.034 mg/L,测定结果的相对标准偏差为0.69%~3.57%(n=6),加标回收率为95%~105%。该法能有效消除水负峰及其对F–测定的影响,操作简便、测定结果准确可靠,适用于水中F–、Cl–等7种阴离子的测定。     

P204萃取色谱法对Co~(2+)的分离研究

对萃取色谱法分离钴与铜、镉、锰、锌、铁等金属离子进行了研究。用含Ｐ２０４萃取剂的萃淋树脂,经过ｐＨ４．０的ＮａＡｃ溶液转型后,只需用ｐＨ２．５的氯乙酸－氯乙酸钠缓冲溶液作为流动相淋洗,就可将钴与其它金属离子分离。方法分离效果好,操作简单方便,是分离分析钴的一种新方法。     

阴离子交换色谱法测定硫磺熏制姜中亚硫酸盐

建立了阴离子交换色谱分离、抑制型电导检测分析硫磺熏制生姜(简称硫磺姜)中亚硫酸盐的方法。使用NJ-SA-4A阴离子交换分析柱,淋洗液为1.92mmol/L Na2CO3-1.80mmol/L NaHCO3-2%(体积分数)丙酮。通过在样品提取液中加入三乙醇胺,有效地维持了亚硫酸盐的稳定性、并能提高方法的选择性。SO23-在0.02～2.00mg/L范围内线性良好,相关系数为0.9998,峰面积的相对标准偏差为1.9%。方法的检出限为0.015mg/L,加标回收率为84.0%～93.5%。该方法为生姜的市场监测提供了有效的方法。     

Ion chromatographic separation of hydrogen ion and other common mono- and divalent cations

We introduced an approach to the ion chromatographic determination of common mono- and divalent cations including hydrogen ion and demonstrated the ability of a C30 column dynamically coated first with dodecylsulfate and then with 18-crown-6 ether to separate the cations by ion-exchange mechanism. Using an ethylenediamine solution containing a small concentration of 18-crown-6 ether and lithium dodecylsulfate at pH 6.2 as eluent, the cations were eluted in the order Li < Na+ < NH4+ < H+ < K+ < Mg2+ < Ca2+ with symmetrical peaks. The conductivity vs. concentration plots were linear about three orders of magnitude, from millimolar to micromolar; and the detection limits were all < 0.6 microM. Rainwater was analyzed directly using this ion chromatographic system with satisfactory results.     

Fast determination of tetrafluoroborate by high-performance liquid chromatography using a monolithic column

Fast determination of tetrafluoroborate by high-performance liquid chromatography using a silica-based monolithic column and direct conductivity detection was carried out. Chromatographic separation was performed on a Chromolith Speed ROD RP-18e column (50 mm x 4.6 mm i.d.) with tetrabutylammonium hydroxide (TBA-OH)+ phthalic acid as eluent. The effects of eluent concentration, eluent pH, column temperature and flow rate on retention time of tetrafluoroborate were investigated. The optimized chromatographic conditions for determination of tetrafluoroborate were using 0.5mM TBA-OH + 0.31 mM phthalic acid (pH 5.5) as eluent, column temperature of 30 degrees C and flow rate of 6.0 mL/min. Retention time of tetrafluoroborate was less than 1min under the conditions. Common anions (Cl(-), Br(-), NO3(-) and SO4(2-)) did not interfere with the determination of tetrafluoroborate. Detection limit (S/N = 2) for tetrafluoroborate was 1.4 mg/L. The linear range of calibration curve between peak area and the concentration of tetrafluoroborate was from 1.4 to 100.0 mg/L. The reproducibility was 0.09% and 1.8% (n = 5) relative standard deviation (RSD) for retention time and peak area, respectively. The method has been applied to the determination of tetrafluoroborate in ionic liquids. Recoveries of tetrafluoroborate after spiking were 98.2-101.5%.