Combination of suppressed and non-suppressed ion chromatography with atmospheric pressure ionization mass spectrometry for the determination of anions

Non-suppressed and suppressed ion chromatography in combination with atmospheric pressure ionization mass spectrometry are compared with special respect to sensitivity for the analysis of low-molecular-mass anions. Iodate, bromate, bromide, sulfate, thiosulfate and bromide could be separated by non-suppressed ion chromatography using a low-capacity anion-exchange column and ammonium citrate as mobile phase. Absolute detection limits between 0.4 and 0.7 ng could be achieved; employing a column requiring a flow-rate of 1 ml/min for optimum performance, splitting was necessary so that only 120 μl/min entered the interface of the mass spectrometer resulting in detection limits between 0.03 and 0.06 mg/l. The same stationary phase (packed into a narrow-bore column which allowed operation without splitting) was suitable for the separation of oxyhalides in the suppressed mode with detection limits of 0.5 μg/l (50 pg) with sodium carbonate as eluent. The method was applied to the analysis of drinking water for oxyhalides. The sample pretreatment for the removal of matrix anions (sulfate, chloride and hydrogencarbonate) is described.     

Speciation of halogenides and oxyhalogens by ion chromatography-inductively coupled plasma mass spectrometry

A speciation method utilizing ion chromatography coupled with inductively coupled plasma mass spectrometry is described for simultaneous analysis of eight halogenides and oxyhalogens: chloride, chlorite, chlorate, perchlorate, bromide, bromate, iodide and iodate. The method was applied for the analysis of drinking water samples collected from water treatment plants in areas in Finland, which are known to have high bromine concentrations in ground water. Water samples collected before and after disinfection were analyzed to get information about potential species conversion as a result of purification. Chloride and chlorate were the chlorine species found in these water samples, and iodine existed as both iodate and iodide. In the case of bromine, species conversion had taken place, since total bromine concentrations were increased during disinfection but bromide concentrations were decreased. No bromate was observed in the samples. The detection limits for all the chlorine species studied were 500 μg/l, for bromine species studied 10 μg/l, for iodide 0.1 μg/l and for iodate 0.2 μg/l.     

Comparison of three post-column reaction methods for the analysis of bromate and nitrite in drinking water

Three post-column ion chromatographic methods (i.e., a sodium bromide–sodium nitrite method, an o-dianisidine method, and a potassium iodide–ammonium heptamolybdate method) were compared for bromate and nitrite analysis. Also, the effect of direct mixing of the reagents without ion suppressors for the sodium bromide–sodium nitrite method and the potassium iodide–ammonium heptamolybdate method was investigated. For the analysis of bromate, the three methods showed similar method detection limits (0.17–0.24 μg/l) with pneumatic reagent delivery systems. Direct reagent mixing achieved comparable detection limits to the suppressor configuration. The three methods are also compatible with conductivity detection. When used in combination with conductivity detection, this compatibility allows simultaneous analysis of bromate, nitrite, and other common ions in drinking water, such as bromide. It was found that the o-dianisidine method achieves μg/l-level detection of nitrite and bromate with a simpler configuration than the potassium iodide–ammonium heptamolybdate method, while the sodium bromide–sodium nitrite method was not sufficiently sensitive for nitrite analysis at the μg/l level.     

Simultaneous determination of inorganic disinfection by-products and the seven standard anions by ion chromatography

For the first time, an ion chromatographic method for the simultaneous determination of the disinfection by-products bromate, chlorite, chlorate, and the so-called seven standard anions, fluoride, chloride, nitrite, sulfate, bromide, nitrate and orthophosphate is presented. The separation of the ten anions was carried out using a laboratory-made high-capacity anion-exchanger. The high capacity anion-exchanger allowed the direct injection of large sample volumes without any sample pretreatment, even in the case of hard water samples. For quantification of fluoride, chloride, nitrite, sulfate, bromide, nitrate, orthophosphate and chlorate, a conductivity detection method was applied after chemical suppression. The post-column reaction, based on chlorpromazine, was optimized for the determination of chlorite and bromate. The method detection limit for bromate measured in deionized water is 100 ng/l and for chlorite, it is 700 ng/l. In hard drinking water, the method’s detection limits are 700 ng/l (bromate) and 3.5 μg/l (chlorite). The method’s detection limits for the other eight anions, determined by conductivity detection, are between 100 μg/l (nitrite) and 1.6 mg/l (chlorate).     

Analysis of 500-ng/l levels of bromate in drinking water by direct-injection suppressed ion chromatography coupled with a single, pneumatically delivered post-column reagent

In July 1997, the US Environmental Protection Agency (EPA) began sampling and analyzing drinking water matrices from US municipalities serving populations greater than 100 000 for low-level bromate (>0.20 μg/l) in support of the Information Collection Rule (ICR) using the selective anion concentration (SAC) method. In September 1997, EPA published Method 300.1 which lowered the Method 300.0 bromate method detection limit (MDL) from 20.0 to 1.4 μg/l. This paper describes the research conducted at the EPA’s Technical Support Center laboratory investigating a single post-column reagent, o-dianisidine (ODA), which has been successfully coupled to EPA Method 300.1 to extend the MDL for bromate. Initial studies indicate that this method offers a MDL which approaches the EPA’s SAC method with the added benefit of increased specificity, shortened analysis time and reduced sample preparation. The method provides excellent ruggedness and acceptable precision and accuracy with a bromate MDL in reagent water of 0.1 μg/l, and a method reporting limit of 0.50 μg/l.     

Determination of trace level perchlorate in drinking water and ground water by ion chromatography

Ammonium perchlorate, a key ingredient in solid rocket propellants, has recently been found in ground and surface waters in the USA in a number of states, including California, Nevada, Utah, and West Virginia. Perchlorate poses a health risk and preliminary data from the US Environmental Protection Agency reports that exposure to less than 4–18 μg/l provides adequate human health protection. An ion chromatographic method was developed for the determination of low μg/l levels of perchlorate in drinking and ground waters based on a Dionex IonPac AS11 column, a 100 mM hydroxide eluent, large loop (1000 μl) injection, and suppressed conductivity detection. The method is free of interferences from common anions, linear in the range of 2.5–100 μg/l, and quantitative recoveries were obtained for low μg/l levels of perchlorate in spiked drinking and ground water samples. The method detection limit of 0.3 μg/l permits quantification of perchlorate below the levels which ensure adequate health protection. A new polarizable anion analysis column, the IonPac AS16, and its potential applicability for this analysis is also discussed.     

Simultaneous determination of trace oxyhalides and haloacetic acids using suppressed ion chromatography-electrospray mass spectrometry

A new analytical procedure for the simultaneous determination of trace oxyhalides and haloacetic acids (HAs) in drinking water and aqueous soil extracts is described. The method uses micro-bore ion chromatography (IC) coupled with suppressed conductivity (SC) and electrospray ionization mass spectrometric detection (ESI-MS). The IC-SC-ESI-MS system included a secondary flow of 100% MeOH, which was added to the column eluate (post-suppressor) and resulted in a significant increase in sensitivity for all analytes. All ESI-MS parameters were optimized for HA analysis and sensitivity quantitatively compared to suppressed conductivity. Full analytical performance characteristics for the developed method are presented for monochloro-, monobromo-, dichloro-, dibromo-, trichloro-, bromochloro, chlorodifluoro-, trifluoro-, dichlorobromo- and dibromochloroacetic acid, as well as the oxyhalides iodate, bromate, chlorate and perchlorate. In the case of the HAs, an optimised 25-fold SPE preconcentration method meant all analytes could be readily detected well below the USEPA 60 μg/L regulatory limit using conductivity and/or ESI-MS. The IC-ESI-MS method was applied to the determination of oxyhalides and HAs in both soil extracts and drinking water samples. Soil samples were extracted using ultra pure water with subsequent determination of perchlorate at 1.68 μg/g of soil. A drinking water sample containing HAs was preconcentrated using LiChrolut EN solid phase extraction cartridges with subsequent sulphate and chloride removal. Total HAs were determined at 13 μg/L.     

Preconcentration of triazine herbicides from water by an ion chromatography column and determination by gas chromatography-mass spectrometry

The efficiency of ion chromatography columns packed with styrene-divinylbenzene copolymer containing quaternary ammonium groups to preconcentrate triazine herbicides and their degradation products below μg/l levels has been established. Retention is studied for different types of water. Pure methanol was used in a one-step elution. Enrichment factors of at least 4000 are achieved. Determination was carried out by using gas chromatography-single-ion monitoring mass spectrometry. Recoveries for run-off agricultural water were between 67–100% and close to 100% for ground water. The maximum admissible concentration ion drinking water (0.1 μg/l) and the alert and alarm threshold values in surface water (1 and 3 μg/l, respectively) dictated by the European Union can be measured.     

Determination of trace concentrations of bromate in municipal and bottled drinking waters using a hydroxide-selective column with ion chromatography

The International Agency for Research on Cancer determined that bromate is a potential human carcinogen, even at low micro/l levels in drinking water. Bromate is commonly produced from the ozonation of source water containing naturally occurring bromide. Traditionally, trace concentrations of bromate and other oxyhalides in environmental waters have been determined by anion exchange chromatography with an IonPac AS9-HC column using a carbonate eluent and suppressed conductivity detection, as described in EPA Method 300.1 B. However, a hydroxide eluent has lower suppressed background conductivity and lower noise compared to a carbonate eluent and this can reduce the detection limit and practical quantitation limit for bromate. In this paper, we examine the effect of using an electrolytically generated hydroxide eluent combined with a novel hydroxide-selective anion exchange column for the determination of disinfection byproduct anions and bromide in municipal and bottled drinking water samples. EPA Methods 300.1 B and 317.0 were used as test criteria to evaluate the new anion exchange column. The combination of a hydroxide eluent with a high capacity hydroxide-selective column allowed sub-microg/l detection limits for chlorite, bromate, chlorate, and bromide with a practical quantitation limit of 1 microg/l bromate using suppressed conductivity detection and 0.5 microg/l using postcolumn addition of o-dianisidine followed by visible detection. The linearity, method detection limits, robustness, and accuracy of the methods for spiked municipal and bottled water samples will be discussed.     

Sensitive and selective ion chromatographic method for the determination of trace beryllium in water samples

A selective and sensitive ion chromatographic method has been developed for the determination of beryllium in a number of water samples at low-μg/l concentrations. The separation was performed on a 250×4.0 mm I.D. iminodiacetic acid functionalised silica gel column. Chromatographed Be(II) was detected using visible detection at 590 nm following post-column reaction with chrome azurol S (CAS). The optimum separation and derivatisation conditions were studied in detail. The optimum eluent conditions were found to be 0.4 M KNO₃, adjusted to pH 2.5 using HNO₃, with optimum post-column detection being achieved using a solution containing 0.26 mM CAS, 2% Triton X-100, 50 mM 2-(N-morpholino)ethanesulfonic acid, pH 6.0. Under the above conditions, the concentration detection limit for Be(II) was found to be 3 μg/l in a standard solution and 4 μg/l in a typical tap water sample, using a 250 μl injection. The method was linear over the investigated range of 10 μg/l to 10 mg/l and highly reproducible. The method was successfully applied to a number of water samples of varying matrix complexity, including simulated seawater, and also to a natural freshwater certified reference material NIST 1640.     

Determination of trimethylselenonium iodide, selenomethionine, selenious acid, and selenic acid using high-performance liquid chromatography with on-line detection by inductively coupled plasma mass spectrometry or flame atomic absorption spectrometry

An analytical method has been developed for the determination of selenious acid, selenic acid, trimethylselenonium ion, and selenomethionine. The four selenium compounds were separated by HPLC on a column (25 cm×4 mm I.D.) of the anion-exchanger ESA Anion III with a mobile phase (1.5 ml/min) of 0.0055 M ammonium citrate (pH 5.5). Detection was carried out using an on-line inductively coupled plasma mass spectrometer (ICP-MS) or a flame atomic absorption spectrometer (FAAS) as the selenium-specific detector. The chromatographic parameters and the chemical factors affecting the separation of the selenium species were optimized. The four selenium compounds could be separated within 8 minutes. The detection limits of the coupled HPLC–FAAS system were approximately 1 mg Se/l for each compound (100 μl injection), estimated as three times the base-line noise of the chromatograms. More powerful selenium detection was achieved with an ICP-MS. Selenium was measured at m/z 78. To increase the nebulization efficiency, the Meinhard concentric glass nebulizer was replaced by an ultrasonic nebulizer. The ICP-MS signal intensity was increased with the ultrasonic nebulization by a factor of 7 times for selenious acid and 24 to 31 times for trimethylselenonium ion, selenomethionine, and selenic acid compared to that with the Meinhard nebulization. The detection limits achieved by the HPLC–ICP-MS with the ultrasonic nebulization were 0.08 μg Se/l for trimethylselenonium ion, 0.34 μg Se/l for selenious acid, 0.18 μg Se/l for selenomethionine, and 0.07 μg Se/l for selenic acid, respectively.     

孔雀石绿共振光散射法测定饮用水中痕量BrO3-

在pH3.8的HAc-NaAc缓冲液中,BrO3-氧化I-生成I2,I2与过量的I-反应生成I3-,I3-与孔雀石绿(MG)反应形成缔合微粒,导致体系的共振光散射强度急剧增强,最大共振光散射波长位于465nm处,BrO3-浓度在0～120μg/L范围内有较好线性关系,检出限以3σ计算为3.4ng/mL,据此建立了一种测定微量BrO3-的共振光谱新方法.该法用于饮用水中BrO3-的测定,得到了满意的结果.     

Gas chromatographic determination of nitrite in water by precolumn formation of 2-phenylphenol with flame ionization detection

Nitrite can be determined by its reaction with 2-aminobiphenyl in acidic medium to produce 2-phenylphenol which is quantified by gas chromatography with flame ionisation detection using biphenyl as an internal standard. The hydrolysis of the intermediate diazonium ion avoids many of the problems encountered in the conventional determination of nitrite by the diazotization of an aromatic amine (usually sulphanilamide) and coupling with N-(1-napthyl)ethylenediamine dihydrochloride to yield an azo dye followed by spectrophotometry. Unlike this method, the proposed reaction is rapid and does not suffer from interferences by copper(II), iron(III) and lead(II). The calibration graph was linear over the range 5–1000 μg/l NO₂-N and the limit of detection found to be 0.5 μg/l NO₂-N. A single analysis can be completed within 20 min. The method was not affected by coloured or turbid analyte solutions and has been used to determine nitrite in natural waters.     

On-line microwave sample pretreatment for the determination of mercury in blood by flow injection cold vapor atomic absorption spectrometry

A method for on-line treatment of whole blood in a microwave oven and determination of mercury by flow injection cold vapor atomic absorption spectrometry was developed. After dilution of the whole blood and addition of oxidant, all further treatment and measurement were performed automatically, on-line. Recoveries of five mercury compounds were complete. Good agreement between measured and recommended values of mercury in whole blood reference materials was obtained. Measured mercury values also agreed with results from other accepted methods. Sample throughput was about 45 measurements/hr. Detection limit (3s) in diluted sample was 0.1 μg/l corresponding to 1μg/l Hg in whole blood. The RSD value at 0.5 μg/l Hg in the diluted sample was 6–7% (11 measurements and 0.5 ml sample volume). Mercury concentrations between 1 and 150 μg/l in whole blood can be measured using this method. For three replicate measurements, 0.5 ml of whole blood is required.     

Determination of inorganic oxyhalides in drinking water by on-line coupled capillary isotachophoresis— capillary zone electrophoresis

Some oxyhalides can be found in drinking waters as inorganic disinfection byproducts. An on-line coupled capillary isotachophoresis—capillary zone electrophoresis (CITP-CZE) method was developed for the analysis of chlorate, chlorite and bromate in water. The optimized CITP-CZE electrolyte system consisted of the following: 10 mM—HCl+20 mM—β-Alanine (leading electrolyte), 5 mM—succinic acid (terminating electrolyte), and 10 mM—succinic acid +5 mM—β-Alanine +0.1% HPMC (carrier electrolyte). A clear separation of oxyhalides from other components of drinking water was achieved within 25 min. Method characteristics, i.e., linearity (0–200 ng/mL), accuracy (88–110%), intra-assay (3–5%), quantification limit (5–15 ng/mL), and detection limit (2–5 ng/mL), were determined. Minimum labor requirements, sufficient sensitivity and low running cost are important attributes of this method. It was found that the developed method is useful for the routine analysis of oxyhalides in water.     

Analysis of bromate in drinking water using liquid chromatography-tandem mass spectrometry without sample pretreatment

An analytical method for determining bromate in drinking water was developed using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The (18)O-enriched bromate was used as an internal standard. The limit of quantification (LOQ) of bromate was 0.2 μg/L. The peak of bromate was separated from those of coexisting ions (i.e., chloride, nitrate and sulfate). The relative and absolute recoveries of bromate in two drinking water samples and in a synthesized ion solution (100 mg/L chloride, 10 mg N/L nitrate, and 100 mg/L sulfate) were 99-105 and 94-105%, respectively. Bromate concentrations in 11 drinking water samples determined by LC-MS/MS were <0.2-2.3 μg/L. The results of the present study indicated that the proposed method was suitable for determining bromate concentrations in drinking water without sample pretreatment.     

Spectrophotometric determination of maneb by ternary complex formation with PAR and CTAB

A rapid, simple, direct, and sensitive method has been developed for the determination of maneb (manganese ethylenebisdithiocarbamate) based on the formation of manganese-4-(2′-pyridylazo) resorcinol complex by a ligand displacement reaction, which is rendered water soluble by a cationic surfactant cetyltrimethylammonium bromide (CTAB) by the formation of an ion association complex. Beer's law is obeyed over the concentration range 0.08–2.4 μg/ml of the final solution at 500 nm in pH range 8–12. The molar absorptivity and Sandell's sensitivity are calculated to be 8.84 × 10⁴ l.mol⁻¹.cm⁻¹ and 0.003 μg/cm², respectively. The developed method has been applied to the determination of maneb in commercial formulations, synthetic mixture, grain samples and vegetables.     

Sequential injection spectrophotometric determination of trace amounts of iodide by its catalytic effect on the 4,4'-methylenebis(N,N-dimethylaniline)-chloramine-T reaction

A simple and sensitive sequential injection spectrophotometric procedure is proposed for the determination of trace amounts of iodide in pharmaceutical preparations. The method is based on the catalytic effect of iodide on the (tetra base) 4,4′-methylenebis(N,N-dimethylaniline)-chloramine-T reaction in acidic solution. The method involves a sequential aspiration of 255 μl sample/standard followed by 170 μl tetra base and then 128 μl chloramine-T solutions into a carrier stream to be stacked inside a holding coil and flow reversed through a reaction coil towards a detector. The resulting colored compound is measured at 600 nm using an UV/Vis-spectrophotometer. All the parameters that affect the reaction were evaluated and the calibration curve is linear over a range of 0.1–6.0 μg l⁻¹ of iodide concentration with detection limit of 0.05 μg l⁻¹. A sample throughput of 80 samples per hour and relative standard deviation of less than 2.0% was achieved. The method is successfully applied for the determination of iodide in three different samples (tablets).     

Ultra-pure water for ion chromatography

Water with ionic concentrations substantially below 1 μg/l is an increasing requirement for high sensitivity ion chromatographic analysis. The resistivity of the water is not an adequate guide to impurity levels at less than 1 μg/1 due to the practical limitations in resistivity measurement and to the non-linear variation of resistivity with impurity ion concentration. A water purification system is described using inter-stage monitoring to overcome these limitations and to ensure ultra-trace ionic levels. Some examples of cation analyses are included.     

Automated at-line solid-phase extraction-gas chromatographic analysis of micropollutants in water using the PrepStation

A fully automated at-line solid-phase extraction-gas chromatography procedure has been developed for the analysis of aqueous samples using the PrepStation. The sample extract is transferred from the sample preparation module to the gas chromatograph via an autosampler vial. With flame-ionization detection, limits of determination (S/N=10) of 0.05–0.13 μg/l were obtained for the analysis of HPLC-grade water when modifying the PrepStation by: (i) increasing the sample volume to 50 ml, (ii) increasing the injection volume up to 50 μl, and (iii) decreasing the desorption volume to 300 μl. The HP autosampler had to be modified to enable the automated “at-once” on-column injection of up to 50 μl of sample extract. The amount of packing material in the original cartridge had to be reduced to effect the decrease of the desorption volume. The total set-up did not require any further optimization after having set up the method once. The analytical characteristics of the organonitrogen and organophosphorus test analytes, i.e. recoveries (typically 75–105%), repeatability (2–8%) and linearity (0.09–3.0 μg/l) were satisfactory. The potential of the system was demonstrated by determining triazines and organophosphorus pesticides in river Rhine water at the 0.6 μg/l level using flame-ionization and mass-selective detection. No practical problems were observed during the analysis of more than 100 river water samples.