Hamilton PRP-X100 Anion-exchange Column Research Articles

Speciation analysis of arsenic compounds in seafood by ion chromatography-atomic fluorescence spectrometry

Ion chromatography-ultra violet-hydride generation-Atomic Florescence Spectrometry was applied to detect 5 arsenic species in seafoods. The arsenic species studied include arsenobetaine (AsB), arsenite (As(III)), dimethylarsinic acid (DMA), monomethylarsonic acid (MMA), and arsenate (As(V)), which were extracted from samples using 2% formic acid. Gradient elution using 33 mmol L−1 CH3COONH4 and 15 mmol L−1 Na2CO3 with 10 mL CH3CH2OH at pH 8.4 allowed the chromatographic separation of all the species on a Hamilton PRP-X100 anion-exchange column in less than 8 min. In this study, an ultrasound extraction method was used to extract arsenic species from seafood. The extraction efficiency was good and the recoveries from spiked samples were in the range of 72.6%–109%; the precision between sample replicates was higher than 3.6% for all determinations. The detection limits were 3.543 μg L−1 for AsB, 0.426 μg L−1 for As(III), 0.216 μg L−1 for DMA, 0.211 μg L−1 for MMA, and 0.709 μg L−1 for As(V), and the linear coefficients were greater than 0.999. We also developed an application of this method for the determination of arsenic species in bonito, Euphausia superba, and Enteromorpha with satisfactory results. Therefore, it was confirmed that this method was appropriate for the detection of arsenic species in seafood.

HPLC‐ICP‐MS method development to monitor arsenic speciation changes by human gut microbiota

Inorganic arsenic (iAs) has been classified as a type 1 carcinogen and has also been linked to several noncancerous health effects. Prior to 1995, the As(V) methylation pathway was generally considered to be a detoxification pathway, but cellular and animal studies involving MMA(III) (mono metyl arsonous acid) and DMA(III) (dimethyl arsinous acid) have indicated that their toxicities meet or exceed that of iAs, suggesting an activation process. In addition, thiolated arsenic metabolites were observed in urine after oral exposure of inorganic arsenic in some studies, for which the toxicological profile was not yet fully characterized in human cells. Studies have revealed that microorganisms from the gut environment are important contributors to arsenic speciation changes. This presystemic metabolism necessitates the development of protocols that enable the detection of not only inorganic arsenic species, but also pentavalent and trivalent methylated, thiolated arsenicals in a gastrointestinal environment. We aim to study the biotransformation of arsenic (As) using a Simulator of the Human Intestinal Microbial Ecosystem (SHIME). To be able to analyze the arsenicals resulting from biotransformation reactions occurring in this system, a method using liquid chromatography hyphenated to an inductively coupled plasma mass spectrometer (HPLC-ICP-MS) was developed. A Hamilton PRP-X100 anion exchange column was used. The method allowed separation, identification and quantification of As(III) (arsenite), As(V) (arsenate), DMA(V) (dimethylarsinicacid), MMA(V) (monomethylarsonicacid) and MMMTA (monomethylmonothioarsenate). Attempts to optimize the same method for also separating MMA(III) and DMA(III) did not succeed. These compounds could be successfully separated using a method based on the use of a Zorbax C₁₈ column. The properties of the column, buffer strength, pH and polar nature of mobile phase were monitored and changed to optimize the developed methods. Linearity, sensitivity, precision, accuracy and resolution of both methods were checked. The combination of the two methods allowed successful quantification of arsenic species in suspensions sampled in vitro from the SHIME reactor or in vivo from the human colon and feces.

Determination of tranexamic acid in cosmetic products by high-performance liquid chromatography coupled with barrel plating nickel electrode

Tranexamic acid (TA) is an important reagent in cosmetic skin-whitening formulation and a drug for the inhibition of plasminogen to plasmin in blood. Since there is no chromophore in tranexamic acid molecule to enable direct analysis by UV–visible absorption spectrophotometry, derivatization is thus required by excluding use of UV or fluorescence detection. We report here a relatively simple electrochemical TA detection method by using a barrel plating nickel electrode. Chromatographic separation was performed on a Hamilton PRP-X100 anion-exchange column (150 mm × 4.1 mm i.d., 10 μm particle size) with a (85:15, v/v) mixture of 0.1 mol l −1 NaOH and acetonitrile as mobile phase and pumped at a flow rate of 0.9 ml min −1. By detecting at +0.55 V vs. Ag/AgCl, the calibration plot was linear in the concentration window of 3–1000 ppm with regression coefficient and detection limit (S/N = 3) of 0.9993 and 0.13 ppm (0.84 μmol l −1), respectively. Successive injections ( n = 10) of 50 ppm tranexamic acid showed a R.S.D. value of only 0.3% indicating good reproducibility of the proposed system. The method was successfully applied to the analysis of the content of tranexamic acid in cosmetic products and proved to be suitable for rapid and reliable quality control.

Sample pre-treatment to eliminate cationic methylated arsenic for determining arsenite on an anion-exchange column by high performance liquid chromatography–inductively coupled plasma mass spectrometry

Co-elution of cationic methylated arsenic, e.g. arsenobetaine may interfere with the determination of arsenite on the Hamilton PRP-X100 anion-exchange column using a phosphate buffer isocratically. Therefore, a sample pre-treatment method with self-packed AG MP-50 cation-exchange cartridges was proposed, which enables the arsenite determination in samples containing arsenobetaine on a PRP-X100 column using a phosphate buffer (pH 5.6) isocratically. Methylated arsenic, including dimethylarsinic acid, trimethylarsine oxide, tetramethylarsonium ion, arsenobetaine and arsenocholine, with concentrations below 1000 μg As L −1, may be completely retained in the AG MP-50 cartridge without any changes of arsenite, arsenate and monomethylarsonic acid speciation. Such retention was independent of the pH and matrix. It is proposed to be based on hydrophobic interaction. With the help of AG MP-50 cartridges, 11 arsenic species were detected in fish (DORM-2), mussels (BCR-477) and red algae ( Porphyra tenera) in 10 min on the PRP-X100 column using a phosphate buffer isocratically. Arsenite was the only minor species (up to 0.9%) among all water extractable arsenic species in fish, mussel and red algae.

Arsenic Species Determination in Biological Tissues by HPLC - ICP - MS and HPLC - HG - ICP - MS

The use of high-pressure liquid chromatography coupled directly or by a hydride generation system to an inductively coupled plasma mass spectrometer for the unambiguous measurement of 13 arsenic species in marine biological extracts is described. The use of two chromatography systems; a Supelcosil LC-SCX cation-exchange column eluted with a 20 mM pyridine mobile phase adjusted to pH 2.2 and 2.6 with formic acid, with a flow rate of 1.5 mL min−1 at 40°C, and a Hamilton PRP-X100 anion-exchange column eluted with 20 mM NH4H2PO4 buffer at pH 5.6, with a flow rate of 1.5 mL min−1 at 40°C, was required to separate and quantify cation and anion arsenic species. Under these conditions, arsenous acid could not be separated from other arsenic species and required the use of an additional hydride generation step. Arsenic species concentrations in a locally available Tasmanian kelp (Durvillea potatorum), a certified reference material (DORM-2), and a range of commercially available macroalgae supplements and sushi seaweeds have been measured and are provided for use as in-house quality control samples to assess the effectiveness of sample preparation, extraction, and measurement techniques.

Coupled high performance liquid chromatography–microwave digestion–hydride generation–atomic absorption spectrometry for inorganic and organic arsenic speciation in fish tissue

A high performance liquid chromatography–microwave digestion–hydride generation–atomic absorption spectrometry (HPLC–MW–HG–AAS) coupled method is described for As(III), As(V), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), arsenobetaine (AsB) and arsenocholine (AsC) determination. A Hamilton PRP-X100 anion-exchange column is used for carrying out the arsenic species separation. As mobile phase 17 mM phosphate buffer (pH 6.0) is used for As(III), As(V), MMA and DMA separation, and ultrapure water (pH 6.0) for AsB and AsC separation. Prior to injection into the HPLC system AsB and AsC are isolated from the other arsenic species using a Waters Accell Plus QMA cartridge. A microwave digestion with K 2S 2O 8 as oxidizing agent is used for enhancing the efficiency of conversion of AsB and AsC into arsenate. Detection limits achieved were between 0.3 and 1.1 ng for all species. The method was applied to arsenic speciation in fish samples.

Urinary antimony speciation by HPLC-ICP-MS

This is the first study to report on the determination of Sb species in urine. To this end, HPLC was coupled online to an ICP-MS instrument using ultrasonic nebulization (USN) or hydride generation (HG) for sample introduction into the ICP-MS. The high chloride concentration in urine seriously hampered the chromatographic separation of Sb(V) and Sb(III) on the Dionex AS14 anion exchange column. Distinct signal suppression, shifting of retention times and severe peak broadening did not allow the application to urine samples. Progress to avoid these problems in HPLC-USN-ICP-MS could be made by employing a Hamilton PRP-X100 anion-exchange column. However, Na eluting in the void volume of the column gave rise to a Na-induced peak overlapping with the Sb(V) signal when USN was used to aspirate the HPLC eluents into the plasma. Therefore, a HG system was placed between the HPLC and ICP-MS instrumentation to overcome this dilemma. Thus, Sb(V) and Sb(III) were separated in urine with the PRP-X100 column using 20 mM EDTA at pH 4.7 as the mobile phase. Similarly, an ION-120 anion-exchange column was employed to separate trimethylantimony dichloride (TMSbCl2) and Sb(V) with a mobile phase containing 2 mM NH4HCO3 and 1 mM tartaric acid at pH 8.5. Detection limits of 20 ng l−1, 12 ng l−1 and 8 ng l−1 for Sb(V), TMSbCl2 and Sb(III), respectively, could be established in a 1 + 2 diluted urine matrix. The developed HPLC-HG-ICP-MS method was applied to the speciation of Sb in the urine of occupationally exposed and non-exposed subjects. Additionally, two lyophilised urine reference materials were investigated. Sb(V) was by far the predominant Sb species, followed by TMSbCl2. Only ultratraces of Sb(III), if any detectable, could be found. The sum of the concentrations of Sb(V), Sb(III) and TMSbCl2 in urine samples ranged between 51 and 78% of their total Sb concentrations.

Determination of 'arsenosugars' in algae with anion-exchange chromatography and an inductively coupled plasma mass spectrometer as element-specific detector.

The retention behavior of four naturally occurring dimethylarsinoylribosides with -CH2-CHOH-CH2X (X = OH, HO3POCH2CHOHCH2OH, SO3H, OSO3H) as aglycones, of arsenous acid, arsenic acid, methylarsonic acid, and dimethylarsinic acid was investigated on a Hamilton PRP-X100 anion-exchange column with aqueous solutions of ammonium dihydrogen phosphate (20 mmol/L) in the pH range of 3.8-9.0 as mobile phase. A HP 4500 inductively coupled plasma mass spectrometer (ICP-MS) served as arsenic-specific detector. The influence of pH, temperature, and the concentration of methanol in the mobile phase on the retention times of these arsenic compounds was explored. An aqueous 20 mM ammonium dihydrogen phosphate solution at pH 5.6 at a column temperature of 40 degrees C was considered optimal as it allowed the separation of seven of the arsenic compounds within 16 min. Only arsenous acid and the ribose with the glycerol aglycone have overlapping signals with both migrating almost with the solvent front. At a concentration of 0.50 ng As mL(-1) the relative standard deviations (n = 3) of the signal areas of the eight arsenic compounds was in the range from 3.5 to 8.1%. The linear calibration curves (peak areas) from 0.5 to 10 ng/mL had correlation coefficients > 0.997. Extracts obtained from the brown algae Fucus spiralis and Halidrys siliquosa were chromatographed under the optimized conditions. Both species contained the sulfate riboside as the major arsenic compound (approximately 55% of total extractable arsenic) together with the sulfonate- and phosphate riboside. Arsenic acid was a significant constituent of Halidrys siliquosa (approximately 6.5%), but was not detected in Fucus spiralis.

The separation of dimethylarsinic acid, methylarsonous acid, methylarsonic acid, arsenate and dimethylarsinous acid on the Hamilton PRP-X100 anion-exchange column

In order to separate the potential arsenite metabolites methylarsonous acid and dimethylarsinous acid from arsenite, arsenate, methylarsonic acid and dimethylarsinic acid, the pH-dependent retention behaviour of all six arsenic compounds was studied on a Hamilton PRP-X100 anion-exchange column with 30 mM phosphate buffers (pH 5, 6, 7, 8 and 9) containing 20% (v/v) methanol as mobile phase and employing an inductively coupled plasma atomic emission spectrometer (ICP–AES) as the arsenic-specific detector. Baseline separation of dimethylarsinic acid, methylarsonous acid, methylarsonic acid, arsenate and dimethylarsinous acid was achieved with a 30 mmol dm−3 phosphate buffer (pH 5)–methanol mixture (80:20, v/v) in 25 min. Arsenite is not baseline-separated from dimethylarsinic acid under these conditions. Copyright © 1999 John Wiley & Sons, Ltd.

Arsenic Speciation in Human Urine Reference Materials Using High-Performance Liquid Chromatography with Inductively Coupled Plasma Mass Spectrometric Detection

Six arsenic compounds including arsenocholine, arsenobetaine, dimethylarsinic acid, methylarsonic acid, arsenous acid and arsenic acid were separated by high-performance liquid chromatography (HPLC) on a Hamilton PRP-X100 anion-exchange column using isocratic elution and detected by inductively coupled plasma mass spectrometry (ICP-MS). This analytical procedure was applied to the speciation of arsenic compounds in human urine. The influence of urine matrix on the separation of arsenic compounds was evaluated and the determination of arsenic compounds was not hampered by the ArCl interference which has often been encountered in ICP-MS. Three human urine reference materials, SRM 2670 normal level, SRM 2670 elevated level and Lyphocheck urine metal control 1, were analyzed with respect to arsenic compounds by HPLC-ICP-MS. The results were found to be in good agreement with the certified total arsenic concentration in the reference materials. Six arsenic compounds were detected. Arsenobetaine was found to be present in all of the investigated human urine reference materials.

Chromatographic Ion-Exchange Simultaneous Separation of Arsenic and Selenium Species with Inductively Coupled Plasma--Mass Spectrometry On-Line Detection

The high-performance liquid chromatographic (HPLC) simultaneous separation of arsenite, arsenate, monomethylarsonic acid, dimethylarsinic acid, selenite, and selenate is studied. The dependence of the retention times of these species on the pH of the mobile phase and on the concentration and chemical composition of buffer solutions (acetate, carbonate, and phosphate) is investigated using a Merck Polyspher IC AN2 and a Hamilton PRP-X100 anion exchange column. With a flame atomic absorption spectrometric detector (FAAS) and arsenic or selenium concentrations of at least 100 mg/L, the best simultaneous separation of these species is achieved on the PRP-X100 column using 0.015M ammonium phosphate buffer at pH 8.5, a 1-mL/min flow rate, and a 20-min analysis time. In a second study, these separation conditions are optimized by using an inductively coupled plasma—mass spectrometric (ICP—MS) detector. The use of a 12.5mM ammonium phosphate buffer adjusted to pH 8.5 with ammonia and a flow rate of 1.5 mL/min is found to be optimal for HPLC—ICP—MS studies with the PRP-X100 column. The analysis time is about 16 min; absolute detection limits are estimated in the range of 11–21 pg for arsenic species and 200 and 417 pg for SeIV and SeVI, respectively. Reproducibility ranges from 2.1 to 3.2%, and the linearity is verified in the 0–200-ng/mL range.

Computer-assisted predictions of resolution, peak height and retention time for the separation of inorganic anions by ion chromatography

A computer-assisted method, designed to determine the combined effects of mobile phase variables, was applied in an experimental study in which both an inorganic anion-exchange chromatographic system and a reversed-phase ion-interaction chromatographic system were tested. A Hamilton PRP-X100 anion-exchange column and a Partisil 10 ODS-3 reversed-phase column were used in these studies. Direct resolution, sensitivity (peak height) and retention time modelling were used to predict the total analysis time and the resolutions and peak heights of some critical peaks in the search area of the mobile phase composition. The relationship between resolution, retention time and peak height and the mobile phase variables was approximated by a quadratic polynomial function. In this work, the results of computer plotting of some three-dimensional response surfaces are presented. These graphical illustrations not only helped us to provide a detailed understanding of the chromatographic processes, but also enabled us to define more precisely the location of the optimum conditions.