Use of zwitterionic micelles in the eluent II: a new approach to ion chromatographic analysis of inorganic cations in biological fluids with direct sample injection

A new ion chromatographic (IC) technique has been developed for the determination of inorganic cations in biological fluids with direct sample injection. This involved the use of a mixed zwitterionic-micelle/electrolyte solution as an eluent. The proteins in the sample became bound to the zwitterionic micelles in the eluent and were thus eliminated from the column. The cations were separated by cation exchange. This method is ideal for the online, simultaneous determination of common inorganic cations (Na+, NH4+, K+, Mg2+, and Ca2+) in urine and serum samples. Such an application was demonstrated experimentally. Non-suppressed conductivity was used for analyte detection. The detection limits obtained using this IC system were 2.94, 5.22, 34.9, 32.6, and 56.7 microg/L for Na+, NH4+, K+, Mg2+, and Ca2+, respectively.     

Determination of bromide, bromate and other anions with ion chromatography and an inductively coupled plasma mass spectrometer as element-specific detector

An implementation of the Dionex IonPac AS12A analytical column with an element-specific ICP-MS detection is described for the simultaneous determination of halogen and oxyhalogen anions, sulfate, phosphate, selenite, selenate and arsenate. The chromatographic separation was achieved in less than 4 min with an aqueous 11 mM (NH4)2CO3 (pH 11.2, adjusted with aqueous ammonia) as eluent. Special emphasis was given to optimize the ICP-MS detection conditions for the reliable detection (RSD<5%) of bromate and bromide at a bromine concentration level of 1.0 microg l(-1) with 50 microl sample injection volume. In order to achieve the highest detector response for bromine species an ultrasonic nebulizer equipped with a membrane desolvator had to be employed. The detection limits (S/N=3, sample injection volume 50 microl) obtained with the IC-ICP-MS after the optimization were 0.67 microg l(-1) for BrO3-, 0.47 microg l(-1) for Br-, 69 microg l(-1) for ClO2-, 4 microg l(-1) for Cl-, 47 microg l(-1) for ClO3-, 13 microg l(-1) for SO4(2-), 36 microg l(-1) for PO4(3-), 0.4 microg l(-1) for SeO3(2-), 0.3 microg l(-1) for SeO4(2-), and 0.4 microg l(-1) for AsO4(3-).     

Determination of copper, nickel, zinc, cobalt and manganese in seawater by chelation ion chromatography

Preconcentration and determination of trace elements in seawater by chelation ion chromatography (CIC) was studied. For the retention of metal ions (0.25–0.30 M), ammonium acetate (at pH 4.8–5.1) and macroporous iminodiacetate chelating resin were used. This system (CIC) permits trace and ultra-trace determination of metals in a variety of complex matrices, in particular those with a high content of alkali and alkaline earth metals. Detection limits range from 0.1 to 0.5 ng. Satisfactory results are obtained in the range 0.05–0.5 μg/1 when 60 ml of sample are preconcentrated. In this work the contents of zinc, copper, nickel, cobalt and manganese in seawater from the Venice lagoon are presented. The results obtained by chelation ion chromatography are compared with those obtained using preconcentration of metals with dithizone and ammonium pyrrolidinedithiocarbamate in chloroform and analysed by graphite furnace atomic absorption spectrometry.     

芳香酸淋洗液的单柱阳离子色谱法测定碱金属,铵离子和烷基胺

研究了邻苯二甲酸、苯甲酸和对羟基苯甲酸３种芳香酸分别做淋洗液的单柱阳离子色谱法分离测定Ｌｉ＋、Ｎａ＋、ＮＨ４＋、Ｋ＋、甲胺、乙胺和正丙胺７种物质。３种芳香酸做淋洗液均可将７种物质分离开，且分离结果差异不大。在淋洗液浓度相同的条件下，邻苯二甲酸做淋洗液测定的检出限较低。选择３．０ ｍｍｏｌ／Ｌ邻苯二甲酸做淋洗液测得了上述７种物质的检出限和线性范围，并进行了叶面肥试样分析，７种物质的加标回收率在９６．４％～９８．６％之间。     

On-line preconcentration,ion chromatographic separation and spectrophotometric determination of palladium at trace level

A new method for the determination of Pd by ion chromatography and spectrophotometric detection has been developed. The technique is based on the separation of palladium as PdCl4(2-) by anion exchange and on the detection, at a wavelength of 407 nm, of metal as PdI4(2-) after a post-column reaction with KI. The column used was an IonPac AS4 with HCl and HClO4 eluents. The eluent concentration and composition of post-column reagent were optimised in order to obtain the best separation and sensitivity for Pd. In order to reduce the detection limit, an on-line preconcentration step, has been optimised. The method, as developed, was suitable for palladium determination within a 300 ng/l D.L. value. The method applied to a BCR reference material (CRM 277, estuarine sediment) gave satisfactory results in agreement with the certified value within a D.L. value of 1.3 microg/l for the real sample.     

Determination of low thiourea concentrations in industrial process water and natural samples using reversed-phase high-performance liquid chromatography.

A rapid LC method was developed to determine thiourea in natural samples and freshly prepared as well as used tin-baths from the galvanic industry, with LC on a C18-bonded silica column and with doubly distilled water as eluent. The retention time of thiourea is 1.35 min +/- 5%. UV detection is at 236 nm. Small sample volumes of 10-50 microl allow detection down to 2 microg/l thiourea without any interference by heavy metals or organic compounds and in the case of marine samples by mineral salts. The presented technique should be highly useful for industrial purposes.     

Improved method for the determination of trace perchlorate in ground and drinking waters by ion chromatography

Ammonium perchlorate, a key ingredient in solid rocket propellants, has been found in ground and surface waters in a number of U.S. states, and perchlorate contamination of public drinking water wells is now a serious problem in California. Perchlorate poses a health risk and preliminary data from the U.S. EPA reports that exposure to less than 4-18 microg/l provides adequate human health protection. An improved ion chromatographic method was developed for the determination of low microg/l levels of perchlorate in ground and drinking waters based on a Dionex IonPac AS16 column, an hydroxide eluent generated using an EG40 automated eluent generator, large loop (1000 microl) injection, and suppressed conductivity detection. The method is free of interferences from common inorganic anions, linear over the range of 2-100 microg/l perchlorate, and quantitative recoveries are obtained for low microg/l levels of perchlorate in spiked ground and drinking water samples. The MDL of 150 ng/l permits quantification of perchlorate below the levels that ensure adequate health protection.     

亲水作用色谱柱与阳离子交换树脂柱结合分离无机离子（英文）

A combination of hydrophilic interaction chromatographic(HILIC) column and a weakly acidic cation-exchange resin(WCX) column was used for simultaneous separation of inorganic anions and cations by ion chromatography(IC).Firstly,the capability of HILIC column for the separation of analyte ions was evaluated under acidic eluent conditions.The columns used were SeQuant ZIC-HILIC(ZIC-HILIC) with a sulfobetaine-zwitterion stationary phase(ZIC-HILIC) and Acclaim HILIC-10 with a diol stationary phase(HILIC-10).When using tartaric acid as the eluent,the HILIC columns indicated strong retentions for anions,based on ion-pair interaction.Especially,HILIC-10 could strongly retain anions compared with ZIC-HILIC.The selectivity for analyte anions of HILIC-10 with 5 mmol/L tartaric acid eluent was in the order of I-> NO-3 > Br-> Cl-> H2PO-4.However,since HILIC-10 could not separate analyte cations,a WCX column(TSKgel Super IC-A/C) was connected after the HILIC column in series.The combination column system of HILIC and WCX columns could successfully separate ten ions(Na+,NH+4,K+,Mg2+,Ca2+,H2PO-4,Cl-,Br-,NO-3 and I-) with elution of 4 mmol/L tartaric acid plus 8 mmol/L 18-crown-6.The relative standard deviations(RSDs) of analyte ions by the system were in the ranges of 0.02%-0.05% in retention times and 0.18%-5.3% in peak areas through three-time successive injections.The limits of detection at signal-to-noise ratio of 3 were 0.24-0.30 μmol/L for the cations and 0.31-1.2 μmol/L for the anions.This system was applied for the simultaneous determination of the cations and the anions in a vegetable juice sample with satisfactory results.     

Determination of beryllium in a stream sediment by high-performance chelation ion chromatography

High-performance chelation ion chromatography (HPCIC), involving a chelating silica substrate bonded with aminomethylphosphonic acid, has been developed as a novel technique for the quantitative determination of beryllium in complex matrices. An isocratic separation method, using an eluent containing 1 M KNO3, 0.5 M HNO3 and 0.08 M ascorbic acid, allowed the Be2+ to elute away from the sample matrix peak in under 6 min in a sample containing in excess of 800 mg l(-1) matrix metals. A detection limit of 35 microg l(-1) Be(II) was found using a post-column reaction involving Chrome Azurol S (CAS), 1 M hexamine and 10 mM EDTA buffered at pH 6. The standard addition curve gave excellent linearity (R2>0.999). The procedure was applied to the determination of trace beryllium in a certified sediment sample. The results obtained compared well with the certified value for beryllium.     

On-line preconcentration and determination of Zn in natural water samples employing a styrene-divinylbenzene functionalized resin and flame atomic absorption spectrometry.

In this work, flame atomic absorption spectrometry (FAAS) was used as a detector for the determination of zinc in natural water samples with a flow-injection system coupled to solid-phase extraction (SPE). In order to promote the on-line preconcentration of zinc from samples a minicolumn packed with 35 mg of a styrene-divinylbenzene resin functionalized with (S)-2-[hydroxy-bis(4-vinylphenyl)methyl]pyrrolidine-1-carboxylic acid ethyl esther was utilized. The system operation was based on Zn(II) ion retention at pH 9.5 +/- 0.5 in such a minicolumn with analyte elution, at the back flush mode, with 1 mol L(-1) HCl directly to the FAAS nebulizer. The influence of the chemical (sample pH, buffer concentration, HCl eluent concentration and effect of the ionic strength) and flow (sample and eluent flow rates and preconcentration time) parameters that could affect the performance of the system were investigated as well as the possible interferents. At the optimum conditions, for 2 min of preconcentration time (9.9 ml of sample volume), the developed methodology presented a detection limit of 1.1 microg L(-1), a RSD of 3.5% at 10 microg L(-1) and an analytical throughput of 24 h(-1). Whereas, for 4 min of the preconcentration time (19.8 ml of sample volume) a detection limit of 0.98 microg L(-1), a RSD of 6.5% at 5 microg L(-1) and a sampling frequency of 13 h(-1) are reported.     

Improved coupled-column liquid chromatographic method for the determination of glyphosate and aminomethylphosphonic acid residues in environmental waters

An existing method for the determination of glyphosate and its main metabolite aminomethylphosphonic acid (AMPA) in water has been improved. It is based on precolumn derivatization with the fluorescent reagent 9-fluorenylmethylcloroformate (FMOC) followed by large-volume injection in a coupled-column LC system using fluorescence detection (LC-LC-FD). The derivatization step was slightly modified by changing parameters such as volume and/or concentration of sample and reagents to decrease the limits of quantification (LOQ) of glyphosate and AMPA to 0.1 microg/l. Additionally, the use of Amberlite IRA-900 for preconcentration of glyphosate, prior to the derivatization step, was investigated; the LOQ of glyphosate was lowered to 0.02 microg/l. Drinking, surface and ground water spiked with glyphosate and AMPA at 0.1-10 microg/l concentrations were analysed by the improved LC-LC-FD method. Recoveries were 87-106% with relative standard deviations lower than 8%. Drinking and ground water spiked with glyphosate at 0.02 and 0.1 microg/l were analysed after preconcentration on the anion-exchange resin with satisfactory recoveries (94-105%) and precision (better than 8%).     

Development of a novel rhodamine-type fluorescent probe to determine peroxynitrite

A flow injection (FI) method with on-line preconcentration using a mini-column loaded with 8-hydroxyquinoline immobilized on controlled pore glass (CPG-8HQ) is described for the determination of trace metals by ion chromatography (IC) with pyridine-2-6-dicarboxylic acid (PDCA) as the eluent. Copper, cadmium, lead, zinc, nickel and iron were determined at ppb level after post-column derivatization with 4-(2-pyridylazo)-resorcinol (PAR). The detection limits (3sigma) for the FI/IC system were 8.27, 0.89, 0.09, 0.06, 0.09 and 0.07 g l(-1) for Pb(2+), Cd(2+), Cu(2+) Ni(2+), Zn(2+) and Fe(3+), respectively, using 5 ml sample volume. The method was applied to the analysis of Malaysian natural waters.     

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

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

Solid-phase extraction of some heavy metal ions on a double-walled carbon nanotube disk and determination by flame atomic absorption spectrometry

A new preconcentration method was developed for the determination of trace amounts of Cu(II), Fe(III), Pb(II), Ni(II), and Cd(II) on a double-walled carbon nanotube disk. 4-(2-Thiazolylazo) resorcinol was used as a complexing reagent. The effects of parameters, including pH of the solutions, amounts of complexing reagent, eluent type, sample volume, flow rates of solutions, and matrix ions were examined for quantitative recoveries of the studied analyte ions. The retained metal ions were eluted by 2 M HNO3. The LOD values for the analytes were in the range of 0.7-4.4 microg/mL. Natural water samples and standard reference materials were analyzed by the presented method.     

Use of ion chromatography for the determination of heavy and transition metals in biochemical samples.

A novel, highly sensitive method for simultaneous separation and determination of Cu2+, Ni2+, Zn2+, Cd2+, Co2+, Mn2+ and Pb2+ in biochemical samples was developed and evaluated by ion chromatography. All of these metals were well separated on a bifunctional ion-exchange column by a concentration gradient of oxalic acid and sodium chloride eluents, coupled with spectrophotometric detection after post-column derivatization with 2-[(5-bromo-2-pyridyl)azo]-5-diethylaminophenol at 560 nm. The method detection limits (signal-to-noise 3:1) were at microg l(-1) levels. The calibration graphs were linear (r2>0.999) over two-orders of magnitude. This technique was optimized and validated by analyzing five standard biochemical references.     

Determination of mercury in agroindustrial samples by flow-injection cold vapor atomic absorption spectrometry using ion exchange and reductive elution

A flow-injection system with a Chelite-S(R) cationic resin packed minicolumn is proposed for the determination of trace levels of mercury in agroindustrial samples by cold vapor atomic absorption spectrometry. Improved sensitivity and selectivity are attained since mercuric ions are on-line concentrated whereas other potential interferents are discarded. With on-line reductive elution procedure, concentrated hydrochloric acid could be replaced by 10% w/v SnCl(2), in 6 M HCl as eluent. The reversed-intermittent stream either carries the atomic mercury to the flow cell in the forward direction or removes the residue from reactor/gas-liquid separator to a discarding flask in the opposite direction. Concentration and volume of reagent, acidity, flow rates, commutation times and potential interfering species were investigated. For 120 s preconcentration time, the proposed system handles about 25 samples h(-1) (50.0-500 ng l(-1)), consuming about 10 ml sample and 5 mg SnCl(2) per determination. The detection limit is 0.8 ng l(-1) and the relative standard deviation (RSD) (n=12) of a 76.7 ng l(-1) sample is about 5%. Results are in agreement with certified value of standard materials at 95% confidence level and good recoveries (97-128%) of spiked samples were found.     

Optimization of a field flow pre-concentration system by experimental design for the determination of copper in sea water by flow-injection-atomic absorption spectrometry

A Plackett–Burman 2^7×3/32 design for seven factors (sample pH, sample flow rate, eluent volume, eluent concentration, eluent flow rate, ethanol percentage in the eluent and mini-column diameter) was carried out in order to find the significant variables affecting the field flow pre-concentration system (FFPS) and the flow injection elution manifold for copper determination in seawater samples by flame atomic absorption spectrometry. By using the optimized flow systems, seawater samples were collected and pre-concentrated in situ by passing them with a peristaltic pump through a mini-column packed with Amberlite XAD-4 impregnated with the complexing agent 4-(2-pyridylazo) resorcinol. Thus, copper is pre-concentrated without the interference of the saline matrix. Once in the laboratory, the mini-columns loaded with copper are incorporated into a flow injection system and eluted with a small volume of a 40% (v/v) ethanolic solution of 3 mol l⁻¹ hydrochloric acid into the nebulizer-burner system of a flame atomic absorption spectrometer. Analysis of certified reference materials (SLEW-3 and NASS-5) showed good agreement with the certified value.     

Highly sensitive spectrofluorimetric determination of trace amounts of lead with a new fluorescent reagent, 2-hydroxy-1-naphthaldehydene-8-aminoquinoline

A new fluorescent reagent, 2-hydroxy-1-naphthaldehydene-8-aminoquinoline (HNAAQ), was synthesized. The fluorescent reaction of this reagent with lead was also studied. Based on this chelation, a highly sensitive spectrofluorimetric method was developed for the determination of trace amounts of lead in a water-ethanol (5 + 1, v/v) medium at pH = 9.4. Under these conditions, the Pb-HNAAQ complex has excitation and emission maxima at 398 and 450 nm, respectively. The linear range of the method is from 0 to 100 microg l(-1) and detection limit is 0.28 microg l(-1) of lead. Interference of other ions was studied. In strongly basic media most interfering metal ions form precipitates of hydroxides or oxides and can be removed efficiently through filtration while the residual cations can be removed with a cation-exchange resin. Hence, the selectivity of the method can be increased considerably. The procedure can easily be performed and affords good precision and accuracy. The method was successfully applied to the determination of lead in wheat and rice flour.     

Determination of iodide in seawater samples by ion chromatography with chemically-bonded poly(ethylene glycol) stationary phase

An ion chromatographic method for the rapid and direct determination of iodide in seawater is reported. Poly(ethylene glycol) (PEG) groups were chemically bonded onto silica gel or C30-bonded silica gel via diol groups. PEG-bonded C30 binary phases allowed determination of iodide in seawater samples without any interference. Effects of eluent composition on retention behavior of inorganic anions have been investigated. Both cation and anion of the eluent affected the retention of analyte anions. The retention time of anions increased with increasing eluent concentration. The detection limit for iodide obtained by injecting 0.2 microl of sample was 13 microg l(-1) (S/N=3) while the limit of quantitation was 43 microg l(-1) (S/N=10). The present method was successfully applied to the rapid and direct determination of iodide in seawater with long-term durability.     

Determination of tocopherols,tocopherolquinones and tocopherolhydroquinones by gas chromatography-mass spectrometry and preseparation with lipophilic gel chromatography

A method has been developed for the simultaneous determination of a range of aromatic amines using cation-exchange chromatography performed on a standard ion chromatography column using d.c. amperometric detection. The analytes separated were 2,4- and 2,6-toluenediamine (2,4- and 2,6-TDA), aniline, o-toluidine, benzidine, p-chloroaniline, 4,4'-diaminodiphenyl (4,4'-DDP), m-nitroaniline and 1-naphthylamine. A Dionex CS12 column was used with gradient elution from an initial eluent of 5% CH3CN+35 mM H2SO4 to 27% CH3CN+35 mM H2SO4 (at 35 min). Detection limits in the range 2.6-22.6 microg/l were observed for all analytes except m-nitroaniline, for which the detection limit was 201 microg/l. Linear calibrations and good precision were observed and the method was applied to the determination of benzidine, p-chloroaniline and 1-naphthylamine in wastewater samples. Further, the separation was also used (after some modification of the eluent conditions) for the determination of 2,4- and 2,6-toluene diisocyanate (2,4- and 2,6-TDI) and 4,4'-methylenediphenyl diisocyanate (4,4'-MDI) after their hydrolysis to 2,4-TDA, 2,6-TDA and 4,4'-DDP. Detection limits for 2,6- and 2,4-TDI and 4,4'-MDI were 3.8, 8.2, and 11.2 microg/l, respectively. The method was applied to the determination of diisocyanates in air.