Non-suppressed Ion Chromatography Research Articles

Determination of boric acid and silicic acid in mineral water by nonsuppressed ion chromatography

Determination of boric acid and silicic acid in mineral water by nonsuppressed ion chromatography

Implementation of a conductivity cell electrode as an ion chromatography detector.

This technical note illustrates the possibility of using a conductivity cell electrode (CCE) as an ion chromatography (IC) detector to extend the application fields of this analytical technique. A conventional non-suppressed IC system consists of an eluent delivery pump, a separation column, column oven, and conductivity detector (CD). In this study, the conventional CD, which is one of the expensive parts of the instrument, is replaced with a relatively inexpensive CCE, leading to comparable peak resolution, detection sensitivity, and relative standard deviation. The separation effectiveness was retained and the developed IC-CCE system was successfully applied to the simultaneous separation of inorganic anions (SO42-, Cl-, and NO3-) and cations (Na+, NH4+, K+, Mg2+, and Ca2+) in three natural mineral water samples, with good accordance between the monitored values obtained using the CCE and CD. The commercially available CCE is potentially suitable for application as an IC detector for monitoring ionic components with overall IC cost reduction.

An ion chromatography tandem mass spectrometry (IC-MS/MS) method for glyphosate and amino methyl phosphoric acid in serum of occupational workers

A non-suppressed ion chromatography tandem mass spectrometry (IC-MS/MS) has been established to measure glyphosate (GLY) and amino methyl phosphoric acid (AMPA) in serum of the occupational workers. After the inhibition of metal-chelating with EDTA aqueous solution and protein precipitation with acetonitrile, the samples were purified with a modified liquid–liquid extraction method and separated on an ion chromatographic column (250 mm × 2.1 mm) by using a gradient program of 0.4 mol/L methylamine aqueous solution and acetonitrile as mobile phase. Multiple reactions monitoring (MRM) model was used to obtain the sensitivity of the method, and the isotopically labelled internal standards were applied in the calibration process. Good linearities and recoveries were obtained in the validation process. The recovery experiment provided satisfied results with a range of 91%~101% for GLY and 92%~99% for AMPA in human serum and RSD values for both two analytes were <4%. The limits of detection for GLY and AMPA were 0.6 ng/mL and 1.2 ng/mL, respectively. The association between the posts in workplace and the concentration of two contaminants in serum samples was investigated throughout the analysis of the 307 worker serum samples. The data analysis results indicated the distribution of compounds in human serum was significantly related to the exposure probability and duration during the manufacture process of GLY.

Rapid determination of trace haloacetic acids in water and wastewater using non-suppressed ion chromatography with electrospray ionization-tandem mass spectrometry

A simple and rapid method employing non-suppressed ion chromatography with electrospray ionization tandem mass spectrometry has been developed for the direct determination of trace-level haloacetic acids (HAAs) in water samples. Using 70/30 (v/v) acetonitrile/1 M aqueous methylamine as the mobile phase, three IC columns – AS16, AS18 and AS24 from Thermo-Scientific – were tested, respectively, with the AS16 column exhibiting the best overall performance with respect to resolution and retention time. To assess the effects of mobile phase composition on retention time of HAAs, the AS16 column was further tested using (i) different proportions of acetonitrile to aqueous methylamine, (ii) different proportions of acetonitrile to aqueous solution at fixed methylamine concentrations, and (iii) different concentrations of methylamine at fixed proportions of acetonitrile to aqueous solution. With a low proportion of aqueous solution, van der Waals and/or hydrogen-bonding interactions appeared to play an important role in governing HAA retention, i.e., HAAs with relatively higher apparent logKow* caused by elevated solvent sspKa exhibited longer retention times; whereas with a high proportion of aqueous solution, ionic interactions appeared to dominate retention of HAAs, with the more polarizable HAAs exhibiting longer retention times. Using 70/30 (v/v) acetonitrile/1 M aqueous methylamine, the method detection limits were in the range of 0.090–0.216 μg/L for the 11 selected chloro-, bromo- and iodoacetic acids. Finally, this method was applied to monitor HAAs yields in laboratory chlorination experiments and to determine concentrations of HAAs in tap water and wastewater effluent samples.

Simultaneous determination of acetamiprid and 6-chloronicotinic acid in environmental samples by using ion chromatography hyphenated to online photoinduced fluorescence detector.

This study aims to introduce a simple, sensitive, and cost-effective method for the simultaneous determination of acetamiprid and its main metabolite 6-chloronicotinic acid in environmental samples by using a nonsuppressed ion chromatography hyphenated with an online postcolumn photoinduced fluorescence detection system. The fluorescence detector wavelengths λex /λem =257/382nm was set for up to 6.0min for acetamiprid, while λex /λem =231/370nm programmed for 6-chloronicotinic acid for the rest of the analysis time. Both samples were treated by applying miniaturized quick, easy, cheap, effective, rugged, and safe method before the separation of analytes on an IonPac® AS11-HC column by pumping 40mM NaOH having minuscule content of acetonitrile (5%, v/v) as an eluent. Both intrinsically nonfluorescent analytes were turned-on by online postcolumn photoinduced derivatization, avoiding the need for complex chemical derivatization or addition of a postcolumn extra pump. The developed method was appraised for the analysis of environmental samples, exhibiting excellent linearity (0.050-10μg/mL) with a correlation coefficient greater than 0.9993 for both analytes. Whereas, obtained limit of detection (0.025-0.0072μg/mL), recoveries (98.02-116.00%), and inter- and intraday precision (≤3.02 %) were satisfactory for both compounds in environmental samples.

Simultaneous determination of nine atmospheric amines and six inorganic ions by non-suppressed ion chromatography using acetonitrile and 18-crown-6 as eluent additive

Atmospheric amines contribute to the nucleation and initial growth of new particles as well as secondary organic aerosol formation, influencing the radiative balance of the Earth's atmosphere. In this study, we develop an ion chromatography (IC) method for separating and quantifying the nine most abundant amines (methylaminium (MMAH+), dimethylaminium (DMAH+), trimethylaminium (TMAH+), ethylaminium (MEAH+), diethylaminium (DEAH+), propylaminium (MPAH+), butylaminium (MBAH+), ethanolaminium (MEOH+), and triethanolaminium (TEOH+)) from six common inorganic species in atmospheric aerosols. The retention times of the amines were altered by the addition of acetonitrile to the eluent because acetonitrile can reduce the adsorption of hydrophobic amines on the stationary phase. The developed method achieved the successful separation of DEAH+ and TMAH+ from inorganic cations, which often coelute with each other in established IC methods. The interference of K+ on the determination of MEAH+ was eliminated by the complexation of K+ with 18-crown-6, which prolonged the retention time of K+. Finally, 9 target amines and 6 common inorganic cations were separated, with a resolution Rs ≥ 1.2 for DEAH+ and MPAH+ and Rs > 1.5 for other species. The detection limits varied in the range of 0.34-1.48 ng for the 9 amines and 0.19-0.56 ng for the inorganic cations. The developed method was successfully applied for the determination of low molecular weight amines and inorganic cations in PM2.5 collected from an urban site in Shanghai and an isolated coast of Chongming Island. Eight amines were detected in the urban samples, in which MMAH+ and DMAH+ dominated. The average amine concentration in the urban aerosols was 76.3 ± 38.4 ng m−3, which is approximately 4-fold higher than those in the marine samples collected from the coast.

Determination of Cisplatin and Carboplatin Anticancer Drugs by Non-suppressed Ion Chromatography with an Inductively Coupled Plasma Atomic Emission Detector

ABSTRACTTwo non-suppressed ion chromatographic (IC) methods, one with an anion and one with a cation separation column, were investigated for first time to determine cisplatin and carboplatin anticancer drugs using inductively coupled plasma–atomic emission spectrometry as a detector. The Shodex IC YK-421 (4.6 × 125 mm2) column was considered as the preferred separation column. The mobile phase in this case consisted of tartaric acid and boric acid. The flow rate was 1 mL/min and the injection volume was 20 μL. Separation was carried out in about 2 min with column temperature at 30°C after optimization. With cationic separation, the cisplatin elutes first, as opposed to the anionic one, where it elutes second. In addition, with both columns, a second peak for cisplatin appears which is attributed to a hydrolysis product of the drug. For the cation chromatographic method, the repeatability ranged from 3.1 to 5.9%, whereas the inter-day precision was 13.3 and 16.3% for cisplatin and carboplatin, respectively. The detection limits were 0.1 mg/ L Pt for both compounds. The proposed method was applied to the analysis of human urine with satisfactory recoveries indicating that there are no matrix effects.

Physicochemical properties of silica gel coated with a thin layer of polyaniline (PANI) and its application in non-suppressed ion chromatography

Physicochemical properties of a new sorbent and its potential application in non-suppressed ion chromatography (IC) have been investigated. The sorbent was obtained in a process of covering silica gel particles with a film of polyaniline (PANI).The properties of silica modified with polyaniline such as particle size, porosity, average quantity of polyaniline covering carrier and density of sorbent were determined. In our study the following methods were used: microscopic analysis, laser diffraction technique, combustion analysis, mercury porosimetry and helium pycnometry. Column with the newly obtained packing was used for the separation of inorganic anions. Optimized chromatographic system was successfully employed for analysis of iodide and bromide in selected pharmaceutical products (Bochnia salt and Iwonicz salt) applied in chronic respiratory disease. Analysis was carried out using 0.1M solution of HCl in mixture of methanol/water (50:50v/v) as a mobile phase; the flow rate was 0.3mLmin−1, temperature was 24°C and λ=210nm. Validation parameters such as correlation coefficient, RSD values, recovery, detection and quantification limits were found to be satisfactory.

Synthesis and properties of a newly obtained sorbent based on silica gel coated with a polyaniline film as the stationary phase for non-suppressed ion chromatography

The new sorbent for non-suppressed ion chromatography based on silica gel coated with a film of polyaniline (PANI) was obtained in a process of in situ polymerization of aniline by oxidation with ammonium peroxydisulfate. Raman analyses performed using a Thermo Scientific DXR confocal Raman Microscope equipped with the Omnic 8 software from Thermo Fisher Scientific have proved a uniform distribution of PANI on the surface of chromatographic beads and in the pores of the particle.The obtained stationary phase was packed into a stainless steel HPLC column. The quality of the prepared column was verified on the basis of hydrodynamic parameters such as column efficiency index (Ip) and separation impedance (E). The potential application of silica gel modified with polyaniline for separation and determination of selected anions using non-suppressed ion chromatography was also investigated. Chromatographic analyses were performed using of the ion chromatograph Dionex DX-500. The best results were obtained for the mobile phase consisting of an aqueous or methanolic solution of hydrochloric acid. The tested column and optimized chromatographic system were successfully used for the analysis of nitrate, bromide and iodide in waters samples.

Prepared Polymethacrylate-Based Monoliths for the Separation of Cations by Non-Suppressed Capillary Ion Chromatography

This paper describes a novel analytical system for non-suppressed capillary ion chromatography. Methacrylate monolithic columns were prepared from silanized fused-silica capillaries of 320 µm i.d. by in situ polymerization of glycidyl methacrylate and ethylene dimethacrylate in the presence of 1,4-butanediol, 1-propanol and water as the porogen solvents. The introduction of cation-exchange sites was achieved by sulfonating the matrix with sodium sulfite to produce total cation-exchange capacities in the range of 45-105 μequiv/mL for a 25 cm column. The conditions (concentrations of sodium sulfite solution, reacting time and modified flow rate) of sulfonation were optimized. The hydrodynamic and chromatographic performances were estimated. Coupled with a conductivity detector, a capillary ion chromatography system was set up with the prepared column. Finally, the resultant column was used for the separations of five common univalent cations (Li(+), Na(+), NH4(+), K(+) and Cs(+)) using methanesulfonic acid as the eluent and four divalent cations (Mg(2+), Ca(2+), Sr(2+) and Ba(2+)) by non-suppressed capillary ion chromatography; the chromatographic parameters were further researched.

Simultaneous determination of choline, carnitine and betaine in premixes by non-suppressed ion chromatography

A simple, highly sensitive ion chromatographic method for the simultaneous determination of betaine, choline and carnitine in feed premixes is described. Premixes were extracted via ultrasonication in water for 20 min and extracts were analyzed by ion chromatography using an aqueous 3.0 mmol L−1 methane sulfonic acid solution containing 15% (v/v) acetonitrile as the eluent and an IonPac SCS1 column. The composition of the mobile phase was optimized for the efficient separation of the three main analytes from each other as well as from common inorganic cations and trimethylamine, which is an ingredient for the synthesis of the analytes. The recoveries of choline, carnitine and betaine spikes added to premixes were all greater than 90% with replicate relative standard deviations of less than 10%. The limits of detection of this method for these analytes in premixes were calculated to be 10, 6 and 20 mg kg−1, respectively.

Discovery and Early Development of Non-Suppressed Ion Chromatography

This year marks the 30th anniversary of the publication of Non-Suppressed Ion Chromatography, which is a method for the rapid separation of anions with on-line conductimetric detection. In this method, the separation column is connected directly to the conductimetric detector. This single-column method is a simpler technique than the original suppressed ion chromatography method, which requires a large suppressor column to reduce the background conductance. In the new method, the background signal is reduced to a manageable level simply by using an ion-exchange separation column of low exchange capacity that lowers the eluent concentration needed for separation. The eluent ion used for separation is chosen based on having large, bulky structure, which lowers the equivalent conductance and facilitates detection of the sample anions. This is a personal account of the initial discovery and early development of non-suppressed ion chromatography. The circumstances for the discovery are recounted by the two authors. Methods are described for determination of anions, cations with indirect detection, and techniques for increasing detection sensitivity. A fundamental equation for the prediction of ion chromatography detector response is given, and the development of several types of detection schemes for ion chromatography is discussed. Finally, the impact of non-suppressed ion chromatography is discussed together with comments on the discovery process.

Nonsuppressed ion chromatographic determination of total calcium in milk

A novel approach for measuring calcium in milk by the use of high performance nonsuppressed ion chromatography is proposed. Total calcium as well as the calcium present in the colloidal and salt state in milk can be quantified. Because the presence of citrate in the milk serum interferes with the measurement of calcium by the conductivity detector, the free and chelated calcium can also be distinguished. By using a sample preparation procedure using Amberlite resin (Fluka, Steinheim, Germany), the amount of soluble calcium in milk can be determined. Because the quantification of calcium in milk and milk derivatives is becoming increasingly important in order to understand the functionality of the milk proteins, better methods need to be developed to determine, with a high level of accuracy, the amount of calcium present in milk in various forms.

Determination of methylamines and trimethylamine- N-oxide in particulate matter by non-suppressed ion chromatography

An ion chromatography method with non-suppressed conductivity detection was developed for the simultaneous determination of methylamines (methylamine, dimethylamine, trimethylamine) and trimethylamine- N-oxide in particulate matter air samples. The analytes were well separated by means of cation-exchange chromatography using a 3 mM nitric acid/3.5% acetonitrile (v/v) eluent solution and a Metrosep C 2 250 (250 mm × 4 mm i.d.) separation column. The effects of the different chromatographic parameters on the separation were also investigated. Detection limits of methylamine, dimethylamine, trimethylamine, and trimethylamine- N-oxide were 43, 46, 76 and 72 μg/L, respectively. The relative standard deviations of the retention times were between 0.42% and 1.14% while the recoveries were between 78.8% and 88.3%. The method is suitable for determining if methylamines and trimethylamine- N-oxide are a significant component of organic nitrogen aerosol in areas with high concentration of these species.

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.

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 2PO 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 1.0 mM 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 − < H 2PO 4 − < NO 2 − < Cl − < Br − < NO 3 − < SO 4 2− for the anions and Na + < NH 4 + < K + < Mg 2+ < Ca 2+ for the cations. Complete separation of the above anions or cations was demonstrated within 35 min each. Detection limits calculated at S/N = 3 were 0.05–0.58 ppm (mg/l) for the anions and 0.05–0.38 ppm for the cations, whereas repeatability values were below 2.26, 2.76, and 2.90% for peak height, peak area and retention time, respectively. The method was successfully applied to the determination of inorganic anions and cations in river water samples.

How to Analyze Ionic Liquid Anions? Investigation into the Application of Suppressed and Non-Suppressed Ion Chromatography

In the present study, two reliable and accurate methods have been developed for the quantitative and qualitative determination of ionic liquid anions based on suppressed and non-suppressed ion chromatography. They were applied to the separation and analysis of chloride, bromide, p-tosylate, tetrafluoroborate, hexafluorophosphate, dicyanamide, and bis(trifluoromethanesulfonyl)imide. In the non-suppressed mode, the influence of the concentration of phthalic acid, acetonitrile, and pH of the mobile phase on the retention and separation of analytes were investigated; 8 mM solution of phthalic acid with 20% v/v of acetonitrile (pH = 4) can be regarded as the optimal mobile phase in this separation mode. In the suppressed mode, various compositions of a carbonate/bicarbonate buffer solution with and without acetonitrile were also assessed; 3.2 mM Na2CO3/1 mM NaHCO3 and 25% acetonitrile were found to act as the optimal mobile phase. Under the analytical conditions developed, both methods provided very good separation and symmetrical peak shapes of all compounds within the reasonable time-frame of 30 min. The analytical performance parameters of both methods were good; however sensitivity will be further improved in future studies. Moreover, the suppressed separation mode was successfully applied to the analysis of tetrafluoroborate in a soil aquifer.

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 NH 4NO 3 at pH 5.6, which reduced the build-up of salts on the sampler and skimmer cones. The influences of competing ion (NO 3 −) 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.

Ion chromatographic determination of organic acids in food samples using a permanent coating graphite carbon column

From the viewpoint of a graphite carbon column with excellent durability, it was applied to the ion chromatography (IC) of several organic acids. The carbon column was permanently coated with the cetyltrimethylammonium (CTMA) ion, and the elution behaviors of several organic acids (acetic acid, lactic acid, succinic acid, malic acid, tartaric acid, citric acid) and inorganic anions (Cl −, NO 2 −, NO 3 −, SO 4 2−) were examined according to a non-suppressed IC coupled with conductivity detector, when an ion-exchange ability was given to the graphite carbon column. When salicylic acid and sodium salicylate were used as a mobile phase, each organic acid are analyzed approximately 10 min. But the separation of malic acid, chloride and nitrite was difficult. When benzoic acid and 2-amino-2-hydroxymethyl-1,3-puropanediol (tris aminomethane) were used as a mobile phase, tartaric acid and citric acid, etc. with large valency showed tendency to which the width of each peaks extended and retention time increased. However, it was possible to separate excellently for the analytes detected within 10 min. The developed method was then applied to the determination of organic acids in several food samples.

Perchlorate in water via US Environmental Protection Agency Method 331: Determination of method uncertainties, lowest concentration minimum reporting levels, and Hubaux-Vos detection limits in reagent water and simulated drinking water

US Environmental Protection Agency (EPA) Method 331 determines perchlorate in drinking water using non-suppressed ion chromatography with tandem mass spectrometry. This study reports the results of calibration and recovery studies in reagent water, as well as of a recovery study in simulated drinking water (i.e., total dissolved solids are 500 mg/mL each of chloride, sulfate, and bicarbonate). The perchlorate concentrations in the study ranged from 0.05 to 64 ng/mL. At 95% confidence, the Hubaux-Vos detection limit (H-V DL) was 0.04 ng/mL for the calibration study and the simulated-drinking-water recovery study, and 0.03 ng/mL for the reagent-water recovery study. The lowest concentration minimum reporting level was 0.03 ng/mL for reagent water and 0.07 ng/mL for simulated drinking water, again at 95% confidence.