Preconcentration of trace elements in sea water by complexation with 8-hydroxyquinoline and adsorption on C18 bonded silica gel

Low-cost modular chromatography column rack and vial holders

Gravity-driven chromatography columns are used in scientific, engineering, medical, and industrial fields to separate desired compounds from solutions. Running multiple columns simultaneously saves time and improves procedural consistency. Though column chromatography is widely used, to meet their laboratory needs many investigators must resort to designing and fabricating custom racks for holding their chromatography columns. We have created a robust column rack design, with collection vial holders, that is easily made, inexpensive to build, and may be easily adapted to fit experimental needs. The column holder can be made to hold various sizes of columns (and can be interchanged as necessary); the height of columns above collection vials can be precisely set; and the design is modular, so the rack and vial holders can be expanded to accommodate the desired numbers of columns and the numbers and sizes of vials used to collect fractions eluted from each column. Importantly, the rack is made of inexpensive, readily-available materials and the fabrication is straightforward. Here we present details of the rack's features, a list of materials, and instructions for making it. We hope our design will help investigators who perform gravity-driven column chromatography.

Study on the performance of micro-flow injection preconcentration method on-line coupled to thermospray flame furnace AAS using MWCNTs wrapped with polyvinylpyridine nanocomposites as adsorbent

An adsorbent nanocomposite based on multi-walled carbon nanotubes and polyvinylpyridine is used in the development of a micro-flow injection preconcentration method coupled to TS-FF-AAS for the determination of very low levels of Cd.

Solid phase extraction of inorganic mercury using 5-phenylazo-8-hydroxyquinoline and determination by cold vapor atomic fluorescence spectroscopy in natural water samples

8-Hydroxyquinoline (8-HQ) was chosen as a powerful ligand for Hg solid phase extraction. Among several chelating resins based on 8-HQ, 5-phenylazo-8-hydroxyquinoline (5Ph8HQ) is used for mercury extraction in which the adsorption dynamics were fully studied. It has been shown that Hg(II) is totally absorbed by 5Ph8HQ within the first 30 minutes of contact time with t_1/2 5 minutes, following Langmuir adsorption model. At pH 4, the affinity of mercury is unchallenged by other metals except, for Cu(II), which have shown higher Kd value. With these latter characteristics, 5Ph8HQ was examined for the preconcentration of trace levels of Hg(II). The developed method showed quantitative recoveries of Hg(II) with LOD = 0.21 pg mL⁻¹ and RSD = 3–6% using cold vapor atomic fluorescence spectroscopy (CV-AFS) with a preconcentration factor greater than 250.

Direct analysis of analyte–laden chromatographic stationary phase by induction–heating electrothermal vaporizer with inductively coupled plasma atomic emission spectroscopy

We describe the inductively heated electrothermal vaporization of 8-hydroxyquinolate complexes of Cd, Pb, and Zn adsorbed onto C18-bonded silica gel with inductively coupled plasma atomic emission spectroscopic detection. The metal complexes were adsorbed onto the chromatographic stationary phase using a solid-phase extraction procedure. Instead of eluting the complexes from the stationary phase, the solid phase was directly vaporized into the plasma. Absolute detection limits for this method ranged from 0.3 to 3 µg.Key words: 8-hydroxyquinoline, silica gel, induction heating electrothermal vaporization, inductively coupled plasma atomic emission spectroscopy.

Solid-Phase Extraction on Alkyl-bonded Silica Gels in Inorganic Analysis

Solid-phase extraction (SPE) is an effective tool for the preconcentration of trace elements and their separation from various sample constituents. Octadecyl and other alkyl-bonded silica gels are most widely used for these purposes. The fundamentals of the SPE of inorganic ions are reviewed and compared with those of related techniques (liquid-liquid extraction and reversed-phase liquid chromatography). The extraction of ions in the form of chelate compounds, inorganic salts solvated by neutral reagents, and ion-pair compounds is considered. Numerous applications of SPE to the separation and preconcentration of different elements and their species, including on-line combinations with instrumental determination techniques, are described and tabulated.

Solid-liquid extraction and preconcentration of trace nickel using 2-nitroso-1-naphthol-4-sulfonic acid (Nitroso-S) and TDBA onto benzophenone and determination by atomic absorption spectrometry

Nickel was quantitatively retained by 2-nitroso-1-naphthol-4-sulfonic acid (Nitroso-S) and tetradecyldimethylbenzylammonium chloride (TDBA Cl) onto benzophenone in the pH range 5.0-6.0 from large volumes of aqueous solutions of various samples. After filtration, each solid mass consisting of a nickel complex and benzophenone was dissolved with 5 ml of dimethylformamide (DMF) and the metal was determined by atomic absorption spectrometry (AAS). About 0.6 microg of nickel could be concentrated from 200 ml of an aqueous sample, where its concentration was as low as 3.0 ng/ml. Eight replicate determinations of 2.5 microg/ml of nickel in the final DMF solution gave a mean absorbance of 0.112 with a relative standard deviation of 1.9%. The sensitivity for 1% absorption was 98 ng/ml. The interference of a number of anions and cations was studied and the developed optimized conditions were utilized for the trace determination of nickel in various alloys and biological samples.

Determination of trace elements in biological materials by inductively coupled plasma spectroscopy with novel chelating resins

Although substantial progress has been achieved in inductovely coupled plasma (ICP) spectroscopy, placing it among the principal spectroscopic tools in analytical chemistry research and applications laboratories, some limitations exist especially for the analysis of ultratrace concentration levels in biological materials. The application of chemical and instrumental techniques to increase the concentration levels of analytes is practical, but complicated by the requirements of maintaining the multielement nature of ICP spectroscopy. Two novel chelating resins [poly(dithiocarbamate) and poly(acrylamidoxime)] have been synthesized and applied with ICP spectrometry to enhance the practical sensitivity for ultratrace concentration determinations in biological and other materials. The determination of a number of trace elements in bone, dialysis solutions, serum, and urine is improved using the resin ICP approach. In addition, speciation of inorganic forms of As, Cr, Se, and Te is possible with the poly(dithiocarbamate) resin, and determination of the chemical forms of these elements in urine was performed.