Flow Rate Of Sample Solution Research Articles

Determination of nickel in natural waters by FAAS after sorption on octadecyl silica membrane disks modified with a recently synthesized Schiff’s base

A simple, highly sensitive, accurate and selective method for the determination of trace amounts of Ni 2+ ions in water samples is proposed. The method is based on the separation and preconcentration of Ni 2+ on an octadecyl-bonded silica (ODBS) membrane disk modified by a recently synthesized Schiff’s base N, N′-bis (3-methylsalicylidene) ortho phenylene diamine (MSOPD) at pH 7. The synthesis of this extractant ligand is also described. The retained nickel on the membrane was eluted with 2×5 ml 0.5 M HNO 3 and measured by flame atomic absorption spectrometry (FAAS) at 232.0 nm. The extraction efficiency and the influence of the type and least amount of eluent for the stripping of Ni 2+ from the disks, pH, flow rates of sample solution and eluent, amount of MSOPD, effect of other ions, and breakthrough volume were evaluated. The maximum capacity of the membrane disks modified by 3 mg of MSOPD was found to be 146±4 μg Ni 2+. The 3 σ limit of detection of the method was 30 ng per 1000 ml and also an enrichment factor of 250 was obtained. The proposed method has been applied to the determination of nickel in several water samples with satisfactory results.

Solid Phase Extraction and Flame Atomic Absorption Spectrometric Determination of Trace Amounts of Zinc and Cobalt Ions in Water Samples

A simple and rapid method for the preconcentration of Co2+ and Zn2+ as their 2-guanidino-benzimidazole chelates is proposed using an octadecyl silica cartridge. The retained analytes were recovered with a mixture of 5 mL of 0.01 M HNO3 and 5 mL of methanol. The metal ions in the effluent were determined by flame atomic absorption spectrometry. The effect of different parameters, such as sample matrix, amount of ligand, type of eluent for elution of ions from cartridge, flow rates of sample solution and eluent, breakthrough volume, and limit of detection, were evaluated. The effects of various cationic and anionic interferences on the percent recovery of Co2+ and Zn2+ were also studied. Quantitative extraction efficiencies were obtained by elution of the cartridge with a minimal amount of solvent. Hence, with a typical preconcentration factor of 50, the limits of detections of the proposed method are 0.26 and 1.62 ng mL−1 for Zn2+ and Co2+, respectively. The method was applied to the determination of zinc and cobalt ions in different water samples.

Studies on Solvent Sublation of Trace Heavy Metals by Continuous Flow System as Ternary Complexes of 1,10-Phenanthroline and Thiocyanate Ion

A continuous flow system has been developed to determine trace Cu(II), Mn(II), Ni(II) and Zn(II) in a large volume of water samples by a solvent sublation technique. The mixed solution of 1,10-phenanthroline(phen) and thiocyanate ion was used as ligands for the formation of their ternary complexes. The continuous system was constructed in this laboratory with a peristaltic pump, a mini shaker, three mixing bottles and a flotation cell by connecting each part with a polyethylene tube. The flotation conditions such as the flow rate of sample solution and the injection rates of ligand, buffer and su rfactant solutions have been investigated to obtain the best sublation efficiencies. Each so lution flowed into the flotation cell through each polyethylene tube by the peristaltic pumps. The ternary complexes were floated and extracted into MIBK in a flotation cell of 2 L by bubbling a nitrogen gas. The absorbances of extracted analytes in MIBK were directly measured by graphite furnace-AAS. The concentrations of 1,10-phenanthroline and thiocyanate ion were 2.6 × 10 −3 M and 2.3 × 10 −2 M in the mixed solution, respectively. The pH of sample solution was adjusted to 5.0 with a buffer solution and 1%(m/v) sodium lauryl sulphate solution was added as a surfactant to support the effective flotation of the complexes. The N2 gas was bubbled at 30 mL/min for 90 minutes for 20 L of sample. Reproducible results of less than 10% RSD and recoveries of 80-120% could be obtained in real samples.

Mass Spectrometric Characterization of Organosulfur Compounds Using Palladium(II) as a Sensitivity-Enhancing Reagent

Electrospray ionization/ mass spectrometry (ESI/MS) experiments were performed on several polyaromatic sulfur heterocycles (PASH) in the presence of Pd(II) in order to promote charge transfer and radical cation formation. Critical experimental parameters, i.e., Pd(II)/organosulfur mole ratio, the effect of polyaromatic hydrocarbon interferences and sample solution flow rate, and MS2 collision energy, were optimized. PASH compounds in a spiked hydrogenated oil were then identified to determine matrix effects. Selected peaks from a PASH-enriched aromatic fraction obtained from the heavy distillate of an Arabian crude were then analyzed in order to demonstrate the applicability of the method.

Solid Phase Extraction and Simultaneous Spectrophotometric Determination of Trace Amounts of Copper and Iron Using Mixture of Ligands

A novel sensitive and simple method for rapid and selective extraction, preconcentration and determination of iron (as its bathophenanthroline complex) and copper (as its neocuproine complex) using octadecyl silica cartridges and dual wavelength spectrophotometry is presented. The dual wavelength method (533 nm for the iron-bathophenanthroline and 454 nm for the copper-neocuproine as the analytical wavelength) is used to eliminate spectral interferences. Extraction efficiency and the influence of flow rates of sample solution and eluent, pH, amount of neocuproine, bathophenanthroline and hydroxylamine hydrochloride, type and least amount of eluent for elution of iron and copper complexes from cartridge, break-through volume and limit of detection are evaluated. The effects of various cationic and anionic interferences on percent recovery of iron and copper are also studied. Extraction efficiencies >95% are obtained by elution of cartridges with minimal amount of organic solvent. Iron and copper were determined in the range of 3–100 ng mL−1. The limits of detection are 0.98 and 1.13 ng mL−1 for iron and copper, respectively. The proposed method is applied successfully to the determination of both analytes in river, tap and well water samples.

Solid phase extraction of gold by sorption on octadecyl silica membrane disks modified with pentathia-15-crown-5 and determination by AAS

A simple and selective method for rapid and efficient concentration and determination of μg l −1 levels of Au(III) ions in aqueous solution using octadecyl silica membrane disks modified by pentathia-15-crown-5 and flame atomic absorption spectrometry is presented. The influence of flow rates of eluent and sample solution, amount of ligand, types and least amount of eluent for elution of Au from disks were investigated. Break through volume and limit of detection of the membrane disks modified by 5 mg of the thiacrown ether was found to be 2.0 l and 1.0 μg l −1, respectively. The effects of various cationic interferences on percent recovery of gold were studied. The method was successfully applied for the determinations of gold in some pharmaceutical samples and for the recovery of trace Au 3+ ions from synthetic and water samples.

Separation and Preconcentration of Palladium(II) on Octadecyl-Silica Membrane Disks

A simple and selective method for rapid extraction and determination of Pd(II) ions was developed based on sorption on octadecyl-bonded silica membrane disks of an ion associate of PdBr42− anion with 1-hexadecylpyridinium cation. The sample containing Pd(II) in the presence of 0.15 M of NaBr and 10 mg 1-hexadecylpyridinium bromide was passed through the membrane disk by applying a slight vacuum. Elution was accomplished using 6 ml of acetonitrile. Extraction efficiency and the influence of flow rates of sample solution and eluent, pH, amount of 1-hexadecylpyridinium bromide, type and least amount of eluent for elution of Pd(II) from disks, break through volume and limit of detection were evaluated. Also the effect of various ions on percent recovery of Pd(II) was studied. Extraction efficiencies > 99% were obtained by elution of the disks with minimal amount of solvent. The extraction efficiencies do not depend on the pH (1–10) of solutions nor on the sample solution flow rate in the range of 1–25 ml/min. Hence, with a typical preconcentration factor of 200 the limit of detection of the proposed method is 0.6 µg (for 1000 ml of sample solution). The method was applied to the recovery and determination of Pd(II) in Al–Si–Pd catalysts.

ON-LINE SOLID PHASE EXTRACTION SYSTEM FOR CHROMIUM DETERMINATION IN WATER SAMPLES BY FLOW INJECTION-FLAME ATOMIC ABSORPTION SPECTROMETRY

ABSTRACT An on-line solid phase extraction system has been established for flow injection flame atomic absorption spectrometric determination of chromium on Chromotrope 2R coated Amberlite XAD-1180 (2R-1180) resin. Some parameters such as pH, flow rates of sample and elution solution, matrix effects on the quantitative recoveries of chromium from the resin were examined. The detection limit (3σ) was 2.59 µg/L for preconcentration at 6.5 mL/min. The method was applied for the determination of traces chromium in natural water samples with satisfactory results (relative standard deviations below 5%, recoveries >95%).

Multi-charged Oligonucleotide Ion Formation in Sonic Spray Ionization

An oligonucleotide tends to release hydrogen atoms from a phosphoric acid group and to form negative ions that can be detected by mass spectrometry. Usually, with a solution-spray based ionization technique, the negative ions are present in different charge states. Ion formation for the nucleotide is quite complicated and is easily influenced by matrix and other constituents in a sample solution, as well as by the operating parameters for a mass spectrometer. In this work, we studied oligonucleotide ion formation by using an ion trap mass spectrometer combined with a sonic spray ionization (SSI) source. An oligonucleotide with 20 bases was measured. Effects from contaminants and parameters affecting the ion production, such as a high voltage applied to the ionization source and sample solution-flow rate, were investigated. Our results showed that an ion with about one charge for every three bases was most abundant. However, the signal intensity and the mass spectrum pattern were sensitive to the matrix and operating parameters. One of the reasons for such sensitivity is that there are various ion states for an oligonucleotide. Any change in the matrix or an operating parameter may shift the balances between the ion states. Adding Tris, or (hydroxymethyl)aminomethane, enhanced the signal intensity of the oligonucleotide and promoted formation of the oligonucleotide ion with higher charges, while adding acetic acid favored the ions with lower charges, compared with that obtained in the medium without adding Tris and acetic acid. The effects on charged droplets and chemical enhancement were investigated. The mechanism for oligonucleotide ion formation is discussed.

Preconcentration of trace amounts of beryllium in water samples on octadecyl silica cartridges modified by quinalizarine and its determination with atomic absorption spectrometry

A simple method has been developed for rapid and selective extraction, preconcentration and determination of trace amounts of beryllium. The extraction is carried out by octadecyl silica cartridge, modified with quinalizarine as a chelating agent. The effect of different parameters, such as sample matrix, flowrates of sample solution and eluent, pH, type and least amount of eluent for elution of Be +2 ions from cartridge, breakthrough volume and limit of detection, were evaluated. Also, the effects of various cationic and anionic interferences on percent recovery of Be +2 were studied. Be +2 was extracted from solution at pH 6–6.6 and was eluted from modified cartridge with 5 ml of 0.5 M HNO 3. Extraction efficiencies >99% were obtained by elution of the cartridges with minimal amount of eluent. A preconcentration factor of 200 and a detection limit of 200 ng per 1000 ml were obtained. The method was applied to the recovery and determination of Be +2 in different water and alloy samples.

Solid-Phase Extraction, Separation, and Visible Spectrophotometric Determination of Trace Amounts of Iron in Water Samples

A simple and reliable method is presented for the rapid extraction, separation, preconcentration, and determination of iron as its bathophenanthroline complex by the use of octadecylsilica membrane disks and spectrophotometry. We evaluted extraction efficiency, the influence of sample matrix, type and optimum amount of extractant, flow rates of sample solution and eluent, pH, amounts of bathophenanthroline and hydroxylamine hydrochloride, breakthrough volume, and limit of detection. We also studied the effects of various cationic interferences on percent recovery of iron. Complete elution of the complex from disks was obtained with a minimal amount of solvent. The limit of detection of the proposed method is 0.080 ppb. The method was applied to the recovery and determination of iron in natural waters.

Introducing Samples Directly into Electrospray Ionization Mass Spectrometers Using a Nanospray Interface

Electrospray (ES) is a concentration-dependent phenomenon, and operation at high flow rates results in a corresponding high rate of sample consumption. Sensitivity increases are most readily achieved by decreasing the flow rate of sample solution into the electrospray source. In recent years, a number of methodologies have been developed to achieve ES analyses at sub-ml/min flow rates. There are a large number of microscale ES devices currently in use, but this unit describes in detail a micro-scale interface for direct liquid introduction without separation.

Structural Elucidation of Zwitterionic Sugar Cores from Glycosphingolipids by Nanoelectrospray Ionization–Ion-Trap Mass Spectrometry

The use of electrospray ionization (ESI)–ion-trap mass spectrometry (ITMS) for analysis of zwitterionic, glycolipid-derived sugar cores of glycosphingolipids is described. The capability of the method to perform multiple steps of fragmentation (MSn) allows structural characterization of these compounds. No derivatization of the released oligosaccharides is necessary when using nano-ESI with sample solution flow rates of about 30 nL/min. Investigations of positive as well as negative ions in fragmentation experiments up to MS4 permit determination of the sequence of sugar units, their linkage positions, and the exact location of the substituents phosphocholine and phosphoethanolamine. In the case of phosphocholine, chemical cleavage of this substituent was necessary to obtain all the linkage information. Approximately 150–250 ng of sample was needed for each analysis.

Separation and speciation of Cr(III) and Cr(VI) with Saccharomyces cerevisiae immobilized on sepiolite and determination of both species in water by FAAS

A rapid, sensitive and accurate method for the separation, preconcentration and determination of Cr(III) and Cr(VI) in water samples is described. Chromium species can be separated by biosorption on Saccharomyces cerevisiae immobilized on sepiolite and determined by flame atomic absorption spectrometry (FAAS). The optimum conditions for separation and preconcentration (pH, bed height, flow rate and volume of sample solution) were evaluated. Recovery of the chromium was 96.3±0.2% at 95% confidence level. The breakthrough capacity of the adsorbent was found as 228 μmol g −1 for Cr(III). The proposed method was applied successfully to the determination of Cr(III) and Cr(VI) in spiked and river water samples.

Atomic Absorption Determination of Cobalt after Preconcentration by 1-(2-Pyridylazo)-2-naphthol Immobilized on Surfactant-Coated Alumina

1-(2-Pyridylazo)-2-naphthol loaded onto sodium dodecyl sulfate-coated alumina has been used as a new chelating sorbent for the preconcentration of trace metals prior to atomic absorption spectrometric determination. The effect of pH, flow rate of sample solution, and foreign ions on the sorption of cobalt(II) by this sorbent has been investigated. Preconcentration of cobalt and its separation from various concentrations of manganese are successful from aqueous solutions in the pH range 4–5. The elution of cobalt with acetone from the sorbent column is quantitative. The relative standard deviations at the 20 and 100 μg ml−1 levels were 4.0 and 1.4%, respectively. As there are no observable effects due to changes in the volume of sample solution up to a volume of 1 liter, a preconcentration factor of 100 can be achieved. The method has been applied to the determination of cobalt in mineral water and polluted river water.

Solid-phase extraction and spectrophotometric determination of trace amounts of copper in water samples

A simple method for rapid and selective extraction, preconcentration and determination of copper as it’s neocuproine complex by using octadecylsilica membrane disks and spectrophotometry is presented. Extraction efficiency and the influence of flow rates of sample solution and eluent, pH, amount of neocuproine and hydroxylamine hydrochloride, type and least amount of eluent for elution of copper complex from disks, break through volume and limit of detection were evaluated. Also the effects of various cationic interferences on percent recovery of copper were studied. Extraction efficiencies >99% were obtained by elution of the disks with minimal amount of solvent. The limit of detection of the proposed method is 0.12 ppb. The method was applied to the recovery and determination of copper in different water samples.

Hollow fiber based supported liquid membrane: a novel analytical system for trace metal analysis

A new versatile tool for speciation of trace metals, in particular Cu, Pb and Cd based on a hollow fiber supported liquid membrane (HFSLM) consisting of 1,10-didecyl diaza 18-crown-6, fatty acid and a mixture of toluene and phenylhexane (1 + 1) has been studied for application in natural water conditions. Two types of single hollow fiber modules i.e. non flow and flow systems for free metal ion separation and preconcentration were used. The effect of target elements, sample volume, target metal concentration, and flow rates of sample solution in the case of the flow system on the preconcentration factor for a given receiver solution volume (ca 50–60 μl) placed in the lumen of the membrane) have been studied. High preconcentration factors in the range 100–3000 for Cu, Pb and Cd, for preconcentration times in the range 5–120 min were found using sample and receiver solution volumes of 250 ml and 60 μl, respectively. Preconcentration factors were found to be independent of the initial concentration of target elements in the sample and dependent on initial sample volume. Long term stabilities of these membranes showed that they are stable for at least seven days of continuous use. The results of these studies suggest that by combining SLM with sensitive analytical detectors e.g., voltammetric ones, detection limits of below 10 −10 mol l −1 can be achieved.

Evaluation of a hollow cathode atomic emission source designed for continuous solution sample introduction

A hollow cathode discharge capable of continuous operation with solution sample introduction is described. Discharge current densities up to 0.64 A cm 2 are maintained in a helium plasma. Analyte emission intensities are optimized in terms of anode placement in relation to the hollow cathode, carrier gas flow rate, discharge current and sample solution flow rate. Detection limits for selected elements are reported and range from 0.03 ng ml for Li to 200 ng ml for Zn. Temporal stability of the discharge is examined and a calibration curve for Li is presented.

Elemental mass spectrometry using a helium microwave plasma torch as an ion source

An investigation was performed to evaluate the coupling of a 150 W atmospheric pressure helium microwave plasma torch (MPT) with mass spectrometric detection. The interface of an existing inductively coupled plasma mass spectrometer was modified to sample the helium plasma. Optimization studies illustrate the dependence of analytical signals on various instrumental parameters, including sampling depth, gas and sample solution flow rates, and ion optic settings. With the use of a pneumatic nebulization-desolvation sample introduction system, detection limits for seven non-metallic elements range from 12 ng ml to 1.0 μg ml , comparable to those determined with an Ar ICP and the same mass spectrometer. Interference effects of concomitant cations and isotope ratios for Cl and Br are also presented.

Determination of lead in environmental samples by preconcentration with adsorbent/AAS.

1-Phenyl-3-methyl-4-stearoy1-5-pyrazolone(C18)loaded on a porous polymer resin(C18/SP207)was prepared for the determination of lead in environmental samples. Lead(II)was quantitatively retained on C18/SP207 from an aqueous solution of pH>4.7 in the batch experiment. In the column experiment, lead(II) was quantitatively retained with 2.0g of C18/SP207 when the flow rate of sample solution was lower than 7 ml/min. Lead(II) retained on C18/SP207 was completely eluted with 2 M hydrochloric acid. The recovery from 203000 ml of sample solution containing 400 μg of lead was higher than 96%. Alkali and alkaline earth metal elements, chloride and other ions had no effect on the recovery. The method was applied to the determination of lead in several salt samples and one of seawater. The recoveries of lead(II) added to these samples were approximately 100%.