Capillary ion chromatography of inorganic anions on octadecyl silica monolith modified with an amphoteric surfactant

A reversed-phase monolithic silica based capillary column (Onyx C(18), 150 mm x 0.1 mm) was modified with the amphoteric surfactant, N-dodecyl-N,N-(dimethylammonio)undecanoate (DDMAU) and evaluated for the separation and determination of inorganic anions using on-column capacitively coupled contactless conductivity detection (C(4)D). The chromatographic performance of the column was evaluated and under optimal conditions separation efficiencies of 56,200 plates per meter or 7025 plates per column (at detection point) were observed (for iodide). Direct plumbing of the capillary column to the micro-injector and on-column detection eliminated extra-column band broadening, thus allowing accurate analysis of van Deemter curves obtained for the monolithic capillary column. The calculated value for the C-term in the obtained van Deemter curve was between 3 and 4 ms for inorganic anions, allowing for the utilisation of relatively high flow rates without significant losses in efficiency. The performance of the C(4)D detector was investigated and compared for detection on an open tubular capillary column and on the modified monolithic silica capillary column. The on-column detection approach did not result in any significant decrease in peak sensitivity for the monolith compared to responses recorded for open tubular capillary columns, and in addition meant the system could be applied to rapid separations by simple variation in apparent column length. The proposed chromatographic system allowed for detection of common anions at sub-ppm level with a 10 nL injection volume. Additionally, on-column detection allowed visualisation of the development of the separation at any point in time and evaluation of the longitudinal uniformity of the ion-exchange coating.     

Simultaneous determination of inorganic anions and cations in explosive residues by ion chromatography

A non-suppressed ion chromatographic method by connecting anion-exchange and cation-exchange columns directly was developed for the separation and determination of five inorganic anions (sulfate, nitrate, chloride, nitrite, and chlorate) and three cations (sodium, ammonium, and potassium) simultaneously in explosive residues. The mobile phase was composed of 3.5mM phthalic acid with 2% acetonitrile and water at flow rate of 0.2 mL/min. Under the optimal conditions, the eight inorganic ions were completely separated and detected simultaneously within 16 min. The limits of detection (S/N=3) of the anions and cations were in the range of 50-100 microg/L and 150-320 microg/L, respectively, the linear correlation coefficients were 0.9941-0.9996, and the R.S.D. of retention time and peak area were 0.10-0.29% and 5.65-8.12%, respectively. The method was applied successfully to the analysis of the explosive samples with satisfactory results.     

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   

Separation of inorganic anions on a triazole-functionalized ion exchanger in ion chromatography

The retention behavior of inorganic anions on a triazole-based stationary phase was first examined in ion chromatography. It was initially designed for hydrophilic interaction liquid chromatography and was simply prepared by introducing the triazole groups onto the surface of silica gel via click chemistry. Effective separation of common inorganic anions, including iodate, chloride, bromide, nitrate and iodide, was achieved with Na(2)SO(4) eluent. The logarithm of the retention factor of analytes was observed to be linear with the logarithm of the eluent concentration, and the slopes of the plots were almost the same as those of the ideal theoretical value. The eluent pH value in the range of 3.4-7.0 had little effect on the separation. The utility of the column was demonstrated for the determination of UV-absorbing anions in saliva and tap water.     

Separation of inorganic anions by unsuppresed ion chromatography

The elution behaviour of 11 inorganic anions is investigated by unsuppressed ion chromatography with PRP-X100 a macroporous poly(styrene-divinylbenzene) strong-base anion-exchanger. Weak acids (cyanide and sulfide) can be separated and detected at pH 9 with sodium p-hydroxybenzoate as the eluent.     

Determination of trace inorganic anions in seawater samples by ion chromatography using silica columns modified with cetyltrimethylammonium ion

Conventional silica columns dynamically modified with cetyltrimethylammonium ions were evaluated for the determination of UV-absorbing bromide, nitrate, and nitrite in seawater samples. Cetyltrimethylammonium, which is a quaternary ammonium ion, was dynamically introduced onto silica surfaces. The first layer of the modifier was introduced by electrostatic interaction, whereas the second layer was introduced by hydrophobic interaction. The latter layer worked as the anion-exchange sites. The modified conventional silica columns could be used for separation of inorganic anions. Separation of authentic mixture of five anions was achieved within 17 min. The addition of 0.1 mM cetyltrimethylammonium ion to the eluent improved the repeatability of the retention time. Seawater samples could be directly injected onto the prepared conventional silica columns, and bromide, nitrate, and nitrite levels were determined to be 69, 0.13, and 0.016 ppm, respectively.     

Rapid separation of inorganic anions by capillary ion chromatography using monolithic silica columns modified with dilauryldimethylammonium ion.

The rapid separation of inorganic anions was determined by capillary ion chromatography using monolithic silica capillary columns modified with dilauryldimethylammonium bromide. The stability of the modified stationary phase was satisfactory owing to a strong hydrophobic interaction between the lauryl groups of the reagent, even if the eluent did not contain dilauryldimethylammonium ion. Bromide in seawater samples could be determined by the present system. The repeatability of a retention time of bromide for six successive measurements was around 1.8% when a 500 mM sodium chloride aqueous solution was used as the eluent. Seawater samples were directly injected onto the prepared column without any interference of matrix ions, because an aqueous solution of high-concentration sodium chloride could be used as the eluent. Bromide in seawater samples could be determined within 2 min.     

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。     

Simultaneous separation and detection of anions and cations in ion chromatography

An overview of new possibilities for the simultaneous determination of anions and cations by ion chromatography is presented. A short comparison of the characteristics of separation and detection methods for simultaneous anion–cation determinations of ions is given and applications are discussed.     

Ion chromatography on a latex-coated silica monolith column

A silica monolith column (Merck Chromolith, 100 mm x 4.6 mm) has been coated with Dionex AS9-SC latex nanoparticles to convert the column into an anion-exchange stationary phase. For comparison purposes, a reversed-phase silica monolith was also converted into an anion-exchange column by coating with the cationic surfactant didodecyldimethylammonium bromide (DDAB). Separations of common inorganic anions were carried out using 7.5 or 5.0 mM 4-hydroxybenzoic acid at pH 7.0 along with suppressed conductivity detection. Direct comparisons were then made between the two columns in terms of selectivity, efficiency and stability. The latex-coated column was on average 50% more efficient than the DDAB-coated column. A 10% decrease in retention times was observed on the DDAB column over 11 h of continuous eluent flow, while the latex coating exhibited <1% change in retention even after 2.5 months of periodic use.     

Separation of inorganic anions on hydrophobic stationary phases in ion chromatography

Inorganic anions were separated on hydrophobic stationary phases such as triacontyl-functionalized silica. Eluent conditions were examined in detail, and iodate, nitrate, iodide, and thiocyanate could be separated by using aqueous solutions. The effect of the eluent concentration on the retention of analyte anions was examined for a wide range of sodium sulfate concentrations of up to 1 M. The retention factor of hydrophobic anions decreased with increasing sodium sulfate concentration in the lower concentration region, while it increased with increasing sodium sulfate concentration in the higher concentration region. The addition of a small amount of an organic substance such as acetonitrile and tetraethylene glycol increased the retention of iodide and thiocyanate, while the addition of alcohols decreased their retention. Operating at lower temperature also increased the retention of analyte anions. It was expected that inorganic anions were retained on the stationary phase via hydrophobic interactions. The retention mechanism was discussed, considering the results obtained.     

Simultaneous separation of inorganic anions and cations by using anion-exchange and cation-exchange columns connected in tandem in ion chromatography

Inorganic anions and cations in environmental waters were determined by ion chromatography. Stationary and mobile phases were examined for the simultaneous separation of both anions and cations. Cations detection by UV detection requires a mobile phase with a UV absorbing additive, which indirectly visualizes cations as negative peaks. Simultaneous separation of anions and cations were achieved when using an eluent that consists of inorganic acid with weak basic amino acid as additives. It was convenient to separate both anions and cations by coupling anion-exchange and cation-exchange columns in tandem. The order of the separation columns connected affected the elution profiles. When the eluent comprises of multiple anions and a single cation, the anion-exchange column should be connected in the upper stream, whereas when the eluent comprises multiple cations and a single anion, the cation-exchange column should be connected in the upper stream. Use of switching valves also allowed simultaneous separation of anions and cations in a single chromatographic run. In the present work, operating conditions were optimized for the simultaneous separation of anions and cations.     

Advances in the determination of inorganic anions by ion chromatography

The time period covered for this review includes articles published from 1997 to 1999, with the addition of a few classic references. The purpose of the review is to include the most relevant works from each topic area of the determination of inorganic anions by ion chromatography, including new sample pretreatments, new separation methods, new detection systems and the latest applications in the field of environmental, water, foods, etc. samples. Experimental conditions such as stationary phase, eluent, detection mode, as well as matrix are summarized in a table.     

Determination of inorganic cations and anions by ion-exchange chromatography with evaporative light-scattering detection

Evaporative light-scattering detection (ELSD) was investigated for the direct determination of alkali and alkaline-earth cations by cation-exchange chromatography. Successful single run analysis of Na+, K+, Mg2+ and Ca2+ was achieved in 11 min on the Hamilton PRP-X200 column using an aqueous solution of ammonium formate as mobile phase under a salt concentration step gradient mode (20 mM and 100 mM). Surprisingly the use of ELSD reveals a weak retention of inorganic anions (Cl-, NO3-, SO4(2-)) onto the polymeric cation exchanger, which enables the simultaneous determination of inorganic anions (C1- and NO3-) associated with the cations analysed (Na+ and K+).     

Rapid, low pressure, and simultaneous ion chromatography of common inorganic anions and cations on short permanently coated monolithic columns

Short permanently coated reversed-phase silica based monolithic columns have been investigated for the rapid separation of inorganic anions and cations. One 2.5 x 0.46 cm column was permanently coated with didodecyldimethylammonium (DDAB), for anion analysis; and a second 5.0 x 0.46 cm column was coated with dioctylsulphosuccinnate (DOSS), for cation analysis. The use of a single combined eluent of 2.5 mM phthalate/1.5 mM ethylenediamine, at flow rates of between 4.0 and 8.0 mL/min, resulted in the rapid separation of 8 anions (in under 100 s) and 5 cations (in under 100 s) on the above columns when used individually, with detection limits for common anions ranging from approximately 0.25 to 5 mg/L, and between 2.5 and 50 mg/L for alkaline earth metals, by direct and indirect conductivity detection, respectively. However, with both columns subsequently connected in parallel, with the eluent delivered using a flow splitter from a single isocratic pump, the simultaneous analysis of anions and cations was also possible, based on a single conductivity detector. The potential of this system for the rapid, complete screening of water samples for multiple common anions and cations is shown.     

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.     

Determination of inorganic cations in brine solutions by ion chromatography

The method for analysis of inorganic cations in brine solutions was developed. Ion chromatography is a well-established and accepted technique in the determination of a variety of inorganic ions. However, there are significant complications when ion chromatography is used to determine trace concentrations of inorganic ions in brine matrices. The brine solution in our study was made to simulate the solution from the Waste Isolation Pilot Plant. Instrumental parameters such as eluent composition, flow-rates, and sample loop volumes were investigated to arrive at the optimum condition for the determination of the cations with minimal dilution. Separation was carried out in a Dionex CG12A/CS12A with 8.25 mM H2SO4 as eluent at 1.2 ml/min flow-rate. Our results indicated that ion chromatography is an accurate and a good alternative method for the analysis of cations in brine solution.     

离子色谱法测定乙二醇中微量有机酸和无机阴离子

建立了以YSA-8阴离子交换柱的离子色谱法分析乙二醇中微量有机酸和无机阴离子的方法,比较了进样乙二醇浓度对F-及有机酸测定结果的影响,进样乙二醇质量分数低于8.5%时,能够得到较准确的数据.用本法对所测的有机酸和无机阴离子检出限均在8.9 μg/L以下,线性相关系数r在0.996～0.999范围内,标准样中各物质的离子峰面积的相对标准偏差(RSD)在4.2%以下(n＝11),对乙二醇质量分数约为8.5%的样品中F-及有机酸的加标回收率在91.6%～100.0%之间,乙二醇含水料直接测定无机阴离子的加标回收率在91.8%～104.8%之间.