Phthalate Eluent Research Articles

Ion chromatograph with three-dimensional printed absorbance detector for indirect ultraviolet absorbance detection of phosphate in effluent and natural waters.

An ion chromatography system employing a low-cost three-dimensional printed absorbance detector for indirect ultraviolet detection towards portable phosphate analysis of environmental and industrial waters has been developed. The optical detection cell was fabricated using stereolithography three-dimensional printing of nanocomposite material. Chromatographic analysis and detection of phosphate were carried out using a CS5A 4 × 250mm analytical column with indirect ultraviolet detection using a 255nm light-emitting diode. Isocratic elution using a 0.6mM potassium phthalate eluent combined with 1.44mM sodium bicarbonate was employed at a flow rate of 0.75mL/min. A linear calibration range of 0.5 to 30mg/L PO4 3- applicable to environmental and wastewater analysis was achieved. For retention time and peak area repeatability, relative standard deviation values were 0.68 and 4.09%, respectively. Environmental and wastewater samples were analyzed with the optimized ion chromatography platform and the results were compared to values obtained by an accredited ion chromatograph. For the analysis of environmental samples, relative errors of<14 % were achieved. Recovery analysis was also carried out on both freshwater and wastewater samples and recovery results were within the acceptable range for water analysis using standard ion chromatography methods.

Ion-chromatography of inorganic selenium species with a preliminary preconcentration step

The essential as well as toxic character of selenium is related to its chemical forms and oxidation states. This study presents a method for the determination of Se(IV) and Se(VI) in aqueous solution by ion chromatography with UV detection. Several chromatographic parameters, including mobile phase concentration, pH and methanol content were optimised. The influence of other anions commonly present in water samples was also tested. The best results were obtained on a Hamilton PRP-X-100 column with a 1 mM phthalate eluent at pH 6 with 2.5% methanol. The linear calibration range was from 0.5 to 20 mg L−1. LOD were 60 and 40 μg · L−1 for Se(IV) and Se(VI), respectively. Because this range was not sufficient for the determination of selenium in natural samples, a preconcentration step using solid-phase extraction with an Al2O3 microcolumn was added for the enrichment of the analytes. To improve the sensitivity and selectivity of the measurements, electrothermal AAS was also used as a detection method. This method was applied to the determination of selenium in thermal waters and extracts of pharmaceutical supplements.

Fast ion chromatography of common inorganic anions on a short ODS column permanently coated with didodecyldimethylammonium bromide

Fast ion-exchange chromatography has been developed and applied to the separation of common inorganic anions. Using a didodecyldimethylammonium bromide (DDAB) coated short (30 mm×4.6 mm) ODS analytical column (3-μm particle size) and a 5 m M phthalate eluent (pH 7.5) the isocratic separation of nine common anions in 160 s was possible, with the first seven anions, including phosphate, chloride and sulphate, separated within 65 s. Detection was achieved using indirect UV at 279 nm. The high capacity, highly hydrophobic ion-exchange coating demonstrated excellent stability over time, even at elevated temperatures (45 °C) and exhibited unusual selectivity for common anions (retention order=fluoride, carbonate, phosphate, chloride, bromate, nitrite, sulphate, bromide and nitrate). The developed chromatography was successfully applied to the rapid analysis of river water and seawater samples.

Determination of sulfur-containing inorganic anions by dual ion chromatography and capillary electrophoresis - application to the characterization of bacterial sulfur degradation

An analytical characterization of microbiological oxidation and reduction of sulfur anions has been performed with dual ion chromatography. The apparatus consisted of two chromatographic lines combined by a sample injection valve that allows the simultaneous introduction of a sample solution to both systems. With system 1 non-suppressed conductivity detection of sulfite and sulfate after separation in phthalate eluent was performed. For sulfide, thiosulfate and thiocyanate amperometric detection using a carbonate eluent was carried out on system 2. Parallel runs were possible for these species which could not be separated with one system. Optimizing separation and detection, limits of quantification of 0.02–0.3 mg/L could be obtained. The on-line coupling of a reaction vial to the injection valve was used to investigate the bacterial conversions, because the samples could be taken without contamination and air introduction. Thiosulfate was detected as a metabolite in both sulfur reduction and oxidation. Capillary electrophoresis with conductivity detection was applied as a complimentary technique for monitoring the bacterial sulfur oxidation. The results showed good correlation to the concentration values obtained by ion chromatography.

Ion chromatography of nitrite at the ppb level with photometric measurement of iodine formed by post-column reaction of nitrite with iodide

The difficulty in ion-chromatographic determination of nitrite in aqueous solutions containing a high concentration of chloride arises mainly from incomplete resolution of the peaks for these anions on the separation column whose efficiency is not high. A photometric measurement of iodine formed by a reaction of nitrite with iodide has been found to make it possible to determine, chromatographically, trace amounts of nitrite without any interference from chloride; chloride does not oxidize iodide to produce iodine. The proposed method was based on the separation of nitrite from matrix anions on a silica-based anion-exchange column with a 1.5·10 −3 M phthalate eluent (pH 5.0), followed by photometric measurement of the iodine (as triiodide) formed via a post-column reaction of the separated nitrite with iodide. The optimal conditions for the post-column reaction were established by varying the concentrations of iodide, copper(II) and nitric acid in a post-column-reaction solution and the length of a reaction tube. A calibration graph for nitrite, plotted as peak heights versus concentrations, was linear up to 1.50·10 −5 M (690 ppb). The detection limit, defined at S/N=3, was 1.00·10 −7 M (4.60 ppb) nitrite. The presence of chloride ions up to 0.01 M did not give any interference to the determination of nitrite. This method was successfully applied to the determination of nitrite in lake water, river water, sewage works water and snow samples without any pretreatment.

Simultaneous separation of inorganic ions and neutral organics on ion-exchange stationary phases

Mixtures of inorganic ions and neutral organics (polars, polynuclear aromatics) were simultaneously separated on several ion-exchange stationary phases that contained both exchange- as well as reversed-phase functionality. An 8-quinolinol silica gel column and a commercial C 8/anion exchange phase were used for inorganic anion/neutral organic mixtures. Commercial C 8/weak-acid and benzene sulfonate strong-acid cation-exchange columns were employed for metal cation/neutral organic mixtures. Mobile phases were a blend of those normally used for ion-exchange separation with those generally used for reversed-phase high-performance liquid chromatography (HPLC). Both UV and conductivity detectors were used, in series. Indirect UV detection of anions on the C 8/anion column was effected with a phthalate eluent. The indirect detection could be switched off by operating at 306 nm, just above the range where phthalate absorbs; it could be switched back on again at 299 nm. Retention of metal ions on the C 8/cation column decreased with increasing mobile-phase concentration of ethylenediammonium and tartrate, as well as with increasing amounts of methanol in the mobile phase. A study of retention factor versus pH indicated that the p K a of the bound carboxylic acid is about 6.3. Efficiency was found to be better on the strong acid column than on the weak-acid C 8/cation phase. Quantitation of cations and organics was acceptable on both cation-exchange phases. Overall, this work shows the viability of simultaneous ion/neutral separation both on phases designed for mixed-mode work as well as on those intended only for ion-exchange separations. These phases permit good separation of neutral organics at lower methanol concentrations than on conventional reversed-phase columns.

Separation behavior of inorganic anions on an octadecyl-bonded silica column coated with cetyltrimethylammonium by phthalate and salicylate eluents

The separation behavior of seven common inorganic anions on an octadecyl-bonded silica (ODS) column coated with cetyltrimethylammonium (CTA +) by phthalate and salicylate eluents was examined with indirect UV detection. The separation became better with increasing anion-exchange capacity for the phthalate eluent, but not for the salicylate eluent. The CTA +-coated column, equilibrated with 1 m M CTA + in water–methanol (MeOH) (80:20, v/v) (anion-exchange capacity, 0.26 mequiv./column) and 1.5 m M sodium phthalate eluent (pH 6.8) was effective for the determination of inorganic anions in river and pond water samples.

Determination of sulphite and sulphate by ion chromatography using a weakly basic phthalate eluent

A simple ion chromatographic method was developed for the determination of sulphite and sulphate using an ODS column dynamically coated with cethylpyridinium bromide and 0.5 mmol 1 −1 phthalate–0.01% triethanolamine–5% methanol at pH 8.5 as eluent. Many inorganic and organic anions had little effect on the determination. The analytical results for sulphite in wine obtained by the proposed method agreed with those obtained by the iodimetric method.

Retention Behavior of the Second System Peak in Ion-Exchange Chromatography with Dibasic Acid Eluent Systems.

The origin and characteristics of the system peaks appearing in ion chromatography with dibasic acid eluent systems were extensively studied by computer simulation, theoretical considerations, and experiments. The functional relationships between the retention volume of the second system peak and chromatographic parameters have been derived for dibasic acid eluent systems. The functional relations reproduced the results by computer simulation of the chromatographic processes for dibasic acid eluent systems based on the plate theory and multiple chemical equilibria in each theoretical plate. Sample injection perturbs not only the partition equilibrium of the eluent acid between the mobile phase and the stationary phase, but also the concentration ratio of monovalent and divalent eluent ions on the ion-exchange site in the stationary phase. Therefore, the second system peak is caused mainly by the perturbation of the partition of the acid molecules in dibasic acid eluent systems, as in monobasic acid eluent systems. In addition, the ion-exchange reaction between HB- and B2- is another cause of the second system peak in dibasic acid eluent systems. The retention volume of the second system peak has been explicitly related to the elution parameters. The complicated retention of the second system peak observed by Jackson and Haddad with phthalate eluent was elucidated for the first time. By using the derived functional relationships, we can easily obtain the partition isotherm for the eluent acid from the retention volume data of the second system peak in the chromatographic measurements.

Computer optimization in ion chromatography : II. A systematic evaluation of linear retention models for anions

Extensive retention for non-suppressed ion chromatography of anions have been acquired for 17 analytes (halides, oxohalides, nitrite, nitrate, sulfite, sulfate, bisulfite, thiosulfate, phosphate, thiocyanate, carbonate, acetate and oxalate) on three stationary phases (Waters IC Pak A, Hamilton PRP-X100 and Vydac 302.IC 4.6) using 7 eluent types (benzoate, phthalate, hydroxide, carbonate/bicarbonate, gluconate/borate, p-toluenesulfonate and phosphate). These retention data are used to assess the validity of retention models which predict a linear relationship between the logarithm of solute capacity factor and the logarithm of the activity of the eluent competing anion. The linearity of these plots is uniformly good, but the slopes differ markedly from those predicted from theory. When the eluent contains two competing anions neither the dominant equilibrium approach nor the effective charge approach give reliable prediction of the slopes. Optimization of one eluent parameter at a time ( e.g. the concentration of the competing anion in the eluent) can be successful if the slope of the retention plot is determined by measurement of analyte retention times at two eluent compositions falling at the extremes of the range of eluent compositions under consideration. An example of this “end points” method is provided, in which the concentration of a phthalate eluent is optimized.

Single-column ion chromatography of passive monitors for atmospheric pollution

Nitrite, nitrate and sulfate anions deposited on passive monitors were determined by using single-column ion chromatography. These monitors were exposed outdoors for various periods of time in an atmosphere with a very low degree of pollution, and they were used to evaluate the rate of deposition of some corrosive species on metallic materials. Two types of passive monitors were studied, namely sulfation and nitration plates. Comparison of the results obtained by using the classical turbidimetric method and single-column ion chromatography shows that turbidimetry is inappropriate for low sulfate concentrations (<2.5 mg/plate) deposited on sulfation plates. Thus, ion chromatography should be used to obtain a representative value of sulfate deposition because it allows the determination of sulfate in amounts as low as 200 μg/plate without further preconcentration. For nitration plates, ion chromatography permits simultaneous determination of nitrite, nitrate and sulfate from the same plate, whereas only nitrite can be determined by the classical colorimetric method. Both gluconate/borate and phthalate eluents were investigated and the results show that phthalate eluent is more appropriate for these plates. It was found that the pH of the sample has an important effect on the area of the sulfate peak. For both eluents, the area increases when the sample pH is lower than 6. This demonstrates the importance of an adequate sample treatment before injection in order to obtain reproducible and accurate values.

Retention and separation of inorganic anions by reversed-phase ion-interaction chromatography on octadecyl silica

The retention behaviour of chloride, nitrite, bromide, nitrate and sulphate was investigated using Partisil 10 ODS-3 as the stationary phase and a solution of tetrabutylammonium in aqueuos phthalate or phosphate buffer as the eluent. The quaternary ammonium ion adsorption behaviour and the influence of the quatenary ammonium concentration, the pH and the buffer concentration on the retention of the inorganic anions is discussed. The major adsorption and ion-exchange equilibria in the retention process were studied and used to develop a retention model for the different analytes. This retention model was verified experimentally. Ion-interaction reversed-phase chromatography with an octadecyl-bonded silica stationary phase and tetrabutylammonium iodide—phthalate eluent was found to be successful system for the separation and determination of inorganic anions and when conductivity detection is used.

Performance characteristics of some commercially available low-capacity anion-exchange columns suitable for non-suppressed ion chromatography

Five commercial low-capacity anion-exchange columns (Vydac 302 IC 4.6, Interaction ION-100, Hamilton PRP-X1OO, Bio-Gel TSK IC-Anion-PW and Waters IC Pak A) were compared in terms of their performance characteristics when used for non-suppressed ion chromatography with conductivity detection. Chromatograms were obtained with the manufacturer's recommended eluent and a phthalate eluent designed to give optimal chromatographic performance within the constraints of reasonable run times and acceptable peak shapes for later eluting peaks. These chromatograms were used to provide data on column efficiency, peak asymmetry and resolution of three critical solute pairs. With the exception of the Interaction column, all columns gave acceptable resolution of a standard mixture of seven anions. Choice between columns should be based on such factors as the types and relative concentrations of sample anions, the sample and eluent pH, the percentage of organic modifier to be used in the eluent and the cost of the columns.

Determination of anions by non-suppressed ion chromatography using an amine column

The Synchropak AX300 column has been used to separate a wide range of anions. A standard solution containing F−, Cl−, NO 2 − , NO 3 − , HPO 4 2− , SO 4 2− ions can be analysed in 8–14 minutes using a phthalate or phthalate/citrate eluent at pH 6–7. Addition of citrate to a phthalate eluent has a pronounced effect on the times of analysis. Detection by direction and indirect UV absorption enables the analysis of a wide range of anions. Application of the technique range from rain water to ash pond liquor analysis.