Determination of trace anions in concentrated weak acids by ion chromatography

Ion-exclusion chromatography (ICE) followed by ion chromatography (IC) was used for the determination of trace anionic contaminants in concentrated weak acids. The ICE separation was used as a pretreatment step to isolate the contaminant anions of strong acids from the excess of matrix ions. Then a fraction containing the analyte ions was separated using IC with suppressed conductivity detection. Microbore–ion-exchange columns were chosen to address the increased purity requirements for use of these concentrated acids in semiconductor applications. The chromatographic conditions were optimized for determining trace chloride, sulfate, phosphate, and nitrate in concentrated 24.5% (v/v) hydrofluoric acid; trace chloride, sulfate, and nitrate in concentrated 85% (w/w) phosphoric acid and trace chloride and sulfate in concentrated 0.7% (v/v) glycolic acid. Method detection limits for the anions of interest were below 100 μg/l.     

Trace anion determination in concentrated hydrofluoric acid solutions by two-dimensional ion chromatography II. Method performance study with a hydroxide eluent and a low noise suppressor

The two-dimensional ion exclusion chromatography/ion chromatography (ICE-IC) approach is considered to be the method of choice for the determination of trace anions in concentrated hydrofluoric acid (48-50%, w/w). In order to achieve lower detection limits, this method was for the first time used with electrolytically generated and purified hydroxide eluents in combination with a low noise electrochemical suppressor. Compared to carbonate based eluents, the achieved gain in peak height sensitivity for chloride, sulfate, nitrate and phosphate is a factor of 6, 7, 16 and 13, respectively. The instrumental detection limits, based on the background noise, are 2, 0.2, 0.4 and 1.4 microg/kg HF 50% (w/w) for the same anions. Their method detection limits, calculated according to SEMI, are all within the 6-10microg/kg HF 50% (w/w) range and thus at least 10 times lower than the current Tier C grade requirements. The chromatographic run time could be shortened with some 10 min by the use of a relatively fast high-capacity hydroxide selective anion exchange column.     

Determination of glyphosate and phosphate in water by ion chromatography--inductively coupled plasma mass spectrometry detection

Quantitative determination of trace glyphosate and phosphate in waters was achieved by coupling ion chromatography (IC) separation with inductively coupled plasma mass spectrometry (ICP-MS) detection. The separation of glyphosate and phosphate on a polymer anion-exchange column (Dionex IonPac AS16, 4.0 mm x 250 mm) was obtained by eluting them with 20 mM citric acid at 0.50 mL min(-1), and the analytes were detected directly and selectively by ICP-MS at m/z = 31. Parameters affecting their chromatographic behaviors and ICP-MS characteristics were systematically examined. Based on a 500-microL sample injection volume, the detection limits were 0.7 microgL(-1) for both glyphosate and phosphate, and the calibrations were linear up to 400 microgL(-1). Polyphosphates, aminomethylphosphonic acid (the major metabolite of glyphosate), non-polar and other polar phosphorus-containing pesticides showed different chromatographic behaviors from the analytes of interest and therefore did not interference. The determination was also interference free from the matrix anions (nitrate, nitrite, sulphate, chloride, etc.) and metallic ions. The analysis of certified reference material, drinking water, reservoir water and Newater yielded satisfactory results with spiked recoveries of 97.1-107.0% and relative standard deviations of < or = 7.4% (n = 3). Compared to other reported methods for glyphosate and phosphate, the developed IC-ICP-MS method is sensitive and simple, and does not require any chemical derivatization, sample preconcentration and mobile phase conductivity suppression.     

Coupled ion chromatography for the determination of chloride, phosphate and sulphate in concentrated nitric acid

A coupled ion chromatography (IC) system was used for the determination of chloride, sulphate and phosphate in high-purity nitric acid. Such a high ionic strength matrix causes a selectivity problem in single IC systems. The first part of the system is used for a pre-separation of the analytes from the nitrate matrix. A specially designed high-capacity anion exchanger with low retention for the analytes and high retention for nitrate was developed. The eluent stream containing the analytes was transferred to the second part of the system via a heart-cut valve and a pre-concentration column. The second system utilizes a high performance anion exchanger and is used to quantify the analytes. Recoveries of the analytes are 80-100% for phosphate, and around 100% for sulphate and chloride. Detection limits for chloride, sulphate and phosphate in concentrated nitric acid (69% w/w) are 0.1, 1 and 5 mg/l, respectively.     

Determination of trace anions in high-nitrate matrices by ion chromatography

An ion chromatography method was developed to determine trace anionic contamination in matrices that have a high concentration of nitrate ion. Contaminant anions of interest were separated on an IonPac AS15 high-capacity anion-exchange column and detected by suppressed conductivity detection. An EG40 eluent generator was used to prepare high-purity and carbonate-free potassium hydroxide. Using the EG40, performance at trace levels was enhanced because background conductivity decreased and retention time reproducibility improved. Trace anionic contamination from the mobile phase was minimized when using the eluent generator compared to using conventionally prepared sodium hydroxide eluents. The signal-to-noise ratio was also improved with the use of a temperature controlled conductivity cell and chromatography hardware in the microbore (2-mm) format. The eluent concentration was optimized to separate the contaminant anions from the excess of the nitrate matrix ions. The procedure was demonstrated for a solution of reagent-grade sodium nitrate and high-purity 0.7% nitric acid. Method detection limits for chloride, sulfate and phosphate of 150 μg/l and lower were achieved.     

离子色谱法同时分析果蔬中5种阴离子

建立了离子色谱法同时测定果蔬中Cl^-,NO2^-,SO42^-,NO3^-,PO43^-5种阴离子含量的方法。通过对前处理条件以及离子色谱条件的优化,确定最优超声提取时间为40 min,温度为30℃,超声提取剂为0.5 mL 1.0 mol/L KOH溶液,最佳流动相为30 mmol/L KOH。结果表明:Cl^-,NO2^-,SO42^-,NO3^-,PO43^-的线性相关系数在0.9995~0.9999之间,回收率范围为89.5%~105.6%,相对标准偏差小于8.2%。该方法对多种样品适应性好。     

Determination of glycerophosphate and other anions in dentifrices by ion chromatography

Simple, reliable and sensitive analytical methods to determine the anions, such as fluoride, monofluorophaosphate, glycerophosphate related to anticaries are necessary for basic investigations of anticaries and quality control of dentifrices. A method for the simultaneous determination of organic acids, organic anions and inorganic anions in the sample of commercial toothpaste is proposed. Nine anions (fluoride, chloride, nitrite, nitrate, sulfate, phosphate, monofluorophaosphate, glycerophosphate and oxalic acid) were analyzed by means of ion chromatography using a gradient elution with KOH as mobile phase, IonPac AS18 as the separation column and suppressed conductivity detection. Optimized analytical conditions were further validated in terms of accuracy, precision and total uncertainty and the results showed the reliability of the IC method. The relative standard deviations (RSD) of the retention time and peak area of all species were less than 0.170 and 1.800%, respectively. The correlation coefficients for target analytes ranged from 0.9985 to 0.9996. The detection limit (signal to noise ratio of 3:1) of this method was at low ppb level (<15 ppb). The spiked recoveries for the anions were 96-103%. The method was applied to toothpaste without interferences.     

离子色谱测定口腔含漱剂中的多种成分

建立了离子色谱法对口腔含漱剂中抗龋剂如氟离子、单氟磷酸根、甘油磷酸根、防腐剂山梨酸、甜味剂糖精以及氯离子、硫酸根、磷酸根等同时测定的方法。采用AS11色谱分析柱和KOH梯度淋洗,抑制电导检测。被测物质的保留时间和峰面积重现性分别小于1.51%和6.02%;被测物的线性相关系数为0.9990~0.9999;加标回收率为89.4%~102.5%。本方法可用于商品化含漱剂和牙棒液体多种组分的同时测定。     

Determination of free and total sulfate and phosphate in glycosaminoglycans by column-switching high-performance size-exclusion and ion chromatography and single-column ion chromatography

Analytical procedures for the determination of free and total sulfate and phosphate in glycosaminoglycans by high-performance liquid chromatography were studied. A column-switching method coupling high-performance size-exclusion chromatography (HPSEC) and ion chromatography (IC) is proposed for the determination of free anions. Good run-to-run and day-to-day precision values (RSD) of < 4.7% were obtained for both anions. Total anion contents were determined after wet acid hydrolysis with nitric acid-hydrogen peroxide (5 + 1) by single-column IC and ICP-AES elemental analysis in order to validate the results. Recoveries ranging from 94.6 to 99.0% for sulfate and from 80.8 to 94.0% for phosphate were obtained. Both HPSEC-IC and single-column IC methods were applied to the analysis of a low molecular mass heparin, a non-fractionated heparin and a chondroitin 4-sulfate. From the free and total sulfate determinations, the content of linked sulfur was calculated and ranged from 5.1 to 12.2% m/m.     

Determination of inorganic and organic anions in one run by ion chromatography with column switching

A method for the simultaneous determination of low-molecular-mass organic and inorganic anions in aqueous solutions was developed using isocratic ion chromatography (IC) with suppressed conductimetric detection and column switching. Owing to the large differences in distribution coefficients between sulphate, nitrate and phosphate and the other species, these ions are separated in the first stage on a medium-capacity anion exchanger, whereas the other anions are led through a second column packed with a high-capacity anion-exchange resin via a column-switching valve. After optimization of the switching procedure a spiked drinking water sample was analysed. Fluoride, acetate, butyrate, formate, nitrate, nitrite and phosphate could be determined in addition to the main anions (chloride and sulphate). The time for a complete analysis is less than 20 min and the method can easily be automated. The precision and detection limit are as usual in IC with background suppression.     

Biodegradation studies of 4-fluorobenzoic acid and 4-fluorocinnamic acid: an evaluation of membrane inlet mass spectrometry as an alternative to high performance liquid chromatography and ion chromatography

The biodegradation of 4-fluorobenzoic acid (4-FBA) and 4-fluorocinnamic acid (4-FCA) has been monitored by membrane inlet mass spectrometry (MIMS) using a hollow-fibre silicone membrane. A novel in-membrane pre-concentration/thermal desorption (IMP-MIMS) technique was employed for MIMS analysis using an oven temperature profile that allowed semi-volatile organic compounds to be accumulated in the membrane and then released by rapid heating. Air drying of the membrane between the analyte pre-concentration and thermal desorption stages improved mass spectrometric performance by removing residual water from the membrane. The concentrations of 4-FBA and 4-FCA determined by MIMS compare well with data obtained by high performance liquid chromatography (HPLC). Stoichiometric amounts of fluoride were monitored using ion chromatography (IC). Intermediates in the biodegradation pathway were identified by liquid chromatography/mass spectrometry (LC/MS). These data establish the potential of MIMS as an alternative to chromatographic methods for monitoring the biodegradation of semi-volatile organic compounds.     

Determination of carbon dioxide and acid components in exhaust gas by suppressed ion chromatography.

Although anions are usually determined by suppressed ion chromatography (IC), carbonate and bicarbonate ions can not be determined, because a mixed solution of sodium carbonate and sodium hydrogencarbonate is used as the eluent. This paper describes an IC method for the determination of carbonate ion and common anions using an IonPac AG17/AS17 column, an EG 40 eluent generator and a conductivity detector. The proposed IC method could determine carbonate ion and anions within 6 min. The relative standard deviations (n = 5) for chloride (0.4 mg L(-1)), nitrite (0.8 mg L(-1)), carbonate (100 mg L(-1)), nitrate (1.0 mg L(-1)) and sulfate (2.0 mg L(-1)) ions were 5.1%, 1.1%, 4.2%, 5.1% and 1.1%, respectively. In addition, the absorbing solution of carbon dioxide was examined, and 2-amino-2-methyl-1-propanol was found to be a good absorbing solution. The proposed IC method was applied to the determination of carbon dioxide and acid components in flue gas and automobile exhaust gas.     

Ion chromatography/inductively coupled plasma mass spectrometry for simultaneous determination of glyphosate, glufosinate, fosamine and ethephon at nanogram levels in water

This paper describes the first approach that simultaneously quantifies four polar, water-soluble organophosphorus herbicides, i.e., glyphosate, glufosinate, fosamine and ethephon, at nanogram levels in environmental waters. The target herbicides were separated completely by ion chromatography (IC) on a polymer anion-exchange column, Dionex IonPac AS16 (4.0 mm x 250 mm), with 30 mM citric acid flowing at 0.70 mL min(-1) as the eluent. On-line inductively coupled plasma mass spectrometry (ICP-MS) using a quadrupole mass spectrometer was employed as a sensitive and selective detector of the effluents. Various parameters affecting the separation and detection were systematically examined and optimized. Detection limits of the herbicides achieved with the proposed IC/ICP-MS method were 1.1-1.4 microg L(-1) (as compound) based on a 500-microL sample injection. Matrix anions, metal ions, phosphate, polyphosphates, non-polar and other polar organophosphorus pesticides showed no interference. The developed method was validated using reservoir water, treated water and NEWater samples spiked at the level of 10-25 microg L(-1) with satisfactory recoveries (95-109%). It is applicable to the simultaneous determination of microg L(-1) concentrations of the herbicides in polluted water.     

Preparation and characterization of polyalkene membranes modified with four different ion-exchange groups by radiation-induced graft polymerization

An ion chromatographic method was developed for the determination of nine inorganic and organic acid anions at sub- to low-microg/l levels in power plant water samples. In this method, samples were injected using a large-volume direct injection technique, the analyte anions were separated on a hydroxide-selective anion-exchange column using high-purity hydroxide eluents generated by an on-line electrolytic eluent generator and detected using the suppressed conductivity detection method. The method performance was evaluated by analyzing synthetic water samples containing additives encountered in the power plant water samples and four water samples from a fossil fuel power plant. The relative standard deviations of retention times of analyte ions separated on the hydroxide-selective anion-exchange column were less than 0.4%. The recoveries of analyte ions spiked into the synthetic water samples at concentrations of 0.13-1.0 microg/l were in the range of 70-120%. The method detection limits for analyte ions in deionized water were 0.0099, 0.0056, 0.019, 0.057, 0.0084, 0.023, 0.067, 0.037, and 0.079 microg/l for fluoride, acetate, formate, chloride, nitrite, sulfate, bromide, nitrate, and phosphate, respectively.     

Critical comparison of retention models for the optimisation of the separation of anions in ion chromatography: II. Suppressed anion chromatography using carbonate eluents

Seven theoretical retention models, namely the linear solvent strength model (using the dominant equilibrium approach and competing ion effective charge approach), the dual eluent species model, the Kuwamoto model, the extended dual eluent species model, the multiple species eluent/analyte model and the empirical end-points model, were used to describe the retention behaviour of anions in suppressed ion chromatography (IC). An extensive set of experimental retention data was gathered for 24 anions (fluoride, formate, bromate, chloride, hexanesulfonate, bromide, chlorate, nitrate, iodide, thiocyanate, perchlorate, sulfite, succinate, sulfate, tartrate, selenate, oxalate, tungstate, phthalate, molybdate, chromate, thiosulfate and phosphate) on a Dionex AS4A-SC column using carbonate eluents of varying concentration and HCO₃⁻:CO₃²⁻ ratios. Statistical comparison of the predicted and experimentally obtained retention factors showed that the performance of the theoretical models improved with the complexity of the model. However the empirical model (in which a linear relationship is assumed between the logarithm of retention factor and the logarithm of eluent strength, but the slope is determined empirically) gave the most consistent performance across the widest range of anions. The empirical end-points model was also shown to be the most satisfactory model due to its low knowledge requirements and easy solution. Compared with non-suppressed IC (see Part I), the retention behaviour in suppressed IC was found to be easier to model by all retention models.     

Reversed-phase liquid chromatography/electrospray ionization/mass spectrometry with isotope dilution for the analysis of nitrate and nitrite in water

A new method was developed for the analysis of nitrate and nitrite in a variety of water matrices by using reversed-phase liquid chromatography/electrospray ionization/mass spectrometry in the negative ion mode. For this direct analysis method, nitrate and nitrite anions were well separated under the optimized LC conditions, detected by monitoring m/z 62 and m/z 46 ions, and quantitated by using an isotope dilution technique that utilized the isotopically labeled analogs. The method sensitivity, accuracy, and precision were investigated, along with matrix effects resulting from common inorganic matrix anions. The isotope dilution technique, along with sample pretreatment using barium, silver, and hydrogen cartridges, effectively compensated for the ionization suppression caused by the major water matrix anions, including chloride, sulfate, phosphate, and carbonate. The method detection limits, based on seven reagent water replicates fortified at 0.01 mg N/L nitrate and 0.1 mg N/L nitrite, were 0.001 mg N/L for nitrate and 0.012-0.014 mg N/L for nitrite. The mean recoveries from the replicate fortified reagent water and lab water samples containing the major water matrix anions, were 92-103% for nitrate with an imprecision (relative standard deviation, RSD) of 0.4-2.1% and 92-110% for nitrite with an RSD of 1.1-4.4%. For the analysis of nitrate and nitrite in drinking water, surface water, and groundwater samples, the obtained results were generally consistent with those obtained from the reference methods. The mean recoveries from the replicate matrix spikes were 92-123% for nitrate with an RSD of 0.6-7.7% and 105-113% for nitrite with an RSD of 0.3-1.8%.     

Bromide/bromate speciation by NTI-IDMS and ICP-MS coupled with ion exchange chromatography

 Two different mass spectrometric methods, negative thermal ionization isotope dilution mass spectrometry (NTI-IDMS) and inductively coupled plasma mass spectrometry (ICP-MS), off-line and on-line coupled with anion exchange chromatography, have been developed for simultaneous bromide and bromate determinations in water samples. The detection limits of these methods are in the range of 0.03–0.09 μg/L using a 50 mL sample.The results are independent of the content of other anions, which could be demonstrated by the analyses of six mineral waters containing chloride and sulfate of up to 160 mg/L and 1500 mg/L, respectively. Bromide has been analyzed by the NTI-IDMS method in the range of 10–500 μg/L and bromate in the range of 1–50 μg/L with relative standard deviations of 0.3–1.2% and 0.4–6%. Quantification for the ICP-MS method was carried out by the standard addition technique, which resulted in relative standard deviations of 5.5% for bromide at the 500 μg/L level and of 13% for bromate at the level of about 3 μg/L. These results are compared with those described in the literature for ion chromatographic (IC) and other methods and those obtained in this work by IC using UV detection, which allows high concentrations of chloride in the bromate fraction. The detection limits of this IC method are 6 μg/L for bromide and 30 μg/L for bromate. NTI-IDMS and ICP-MS therefore fit the recommendations of the European Union (detection limit<2.5 μg/L; precision and accuracy better than 25% at the 10 μg/L level) for methods analyzing the carcinogenic bromate much better than IC and other methods applied up to now. As a definitive but time consuming method, NTI-IDMS is preferably applicable as a calibration technique, whereas ICP-MS, with relatively short analysis times, due to on-line coupling with chromatography, can be used as a sensitive and powerful routine method for trace bromide and bromate species in water samples. Received: 5 July 1996/Accepted: 7 August 1996     

Flow injection dialysis for the determination of anions using ion chromatography

Flow injection dialysis (FID) coupling with ion chromatography (IC) is proposed for simultaneous determination of some anions (bromide, chloride, fluoride, nitrate, nitrite, phosphate and sulfate). A standard or sample containing the anions is injected into a donor stream of a mixture (0.022 M Na(2)CO(3) and 0.028 M NaHCO(3)) flowing into a dialysis cell. The bolus of the dialysate containing the anions, in the acceptor stream of water, flows to the IC injection valve where a portion of the bolus is injected into the IC and analysed under normal IC conditions, with a conductivity detector. FID provides on-line separation and dilution of the analytes from matrix especially from some species such as proteins, surfactant, particulates which may cause damage to the IC columns. Prolongation of life-time of the IC columns is an additional advantage to others which will be discussed. On-line dialysis-IC was also investigated.     

Bromide/bromate speciation by NTI-IDMS and ICP-MS coupled with ion exchange chromatography

 Two different mass spectrometric methods, negative thermal ionization isotope dilution mass spectrometry (NTI-IDMS) and inductively coupled plasma mass spectrometry (ICP-MS), off-line and on-line coupled with anion exchange chromatography, have been developed for simultaneous bromide and bromate determinations in water samples. The detection limits of these methods are in the range of 0.03–0.09 μg/L using a 50 mL sample.The results are independent of the content of other anions, which could be demonstrated by the analyses of six mineral waters containing chloride and sulfate of up to 160 mg/L and 1500 mg/L, respectively. Bromide has been analyzed by the NTI-IDMS method in the range of 10–500 μg/L and bromate in the range of 1–50 μg/L with relative standard deviations of 0.3–1.2% and 0.4–6%. Quantification for the ICP-MS method was carried out by the standard addition technique, which resulted in relative standard deviations of 5.5% for bromide at the 500 μg/L level and of 13% for bromate at the level of about 3 μg/L. These results are compared with those described in the literature for ion chromatographic (IC) and other methods and those obtained in this work by IC using UV detection, which allows high concentrations of chloride in the bromate fraction. The detection limits of this IC method are 6 μg/L for bromide and 30 μg/L for bromate. NTI-IDMS and ICP-MS therefore fit the recommendations of the European Union (detection limit<2.5 μg/L; precision and accuracy better than 25% at the 10 μg/L level) for methods analyzing the carcinogenic bromate much better than IC and other methods applied up to now. As a definitive but time consuming method, NTI-IDMS is preferably applicable as a calibration technique, whereas ICP-MS, with relatively short analysis times, due to on-line coupling with chromatography, can be used as a sensitive and powerful routine method for trace bromide and bromate species in water samples. Received: 5 July 1996/Accepted: 7 August 1996     

Application of indirect photometric chromatography to pharmaceutical analysis

Indirect photometric chromatography, which couples analyte separation by ion exchange with indirect photometric detection, is applied to the analysis of complex solutions encountered in the pharmaceutical industry. Applications of primary interest include simultaneous acetate, lactate, chloride, or phosphate determinations, a bisulfite/sulfate assay, and quantitation of trace levels of chloride in deionized water. Three commercially available ion chromatography columns are studied for their suitability in these applications. Due primarily to (A) the acid-base chemistry of the phosphate and bisulfite ions, (B) the need to stabilize the readily oxidized bisulfite, and (C) resin stability at high pH, the column packed with a polymer-based resin is capable of producing analytically superior separations of Cl-, HPO4-2, and matrix components and of SO3-2/SO4-2 in the samples of interest. Under rigid relative concentration conditions, the columns packed with a silica backbone resin are capable of separating acetate, lactate, Cl-, and H2PO4- with baseline resolution and are effective for determining Cl- levels at concentrations of less than one part-per-million.