Silica Gel Microcolumn Research Articles

8-Hydroxyquinoline–chloroform single drop microextraction and electrothermal vaporization ICP-MS for the fractionation of aluminium in natural waters and drinks

A new method of cycle-flow single drop microextraction (SDME) combined with electrothermal vaporization (ETV)-ICP-MS was proposed for the fractionation of aluminium with 8-hydroxyquinoline (8-HQ) as extractant. Several factors affecting the separation of aluminium species, such as sample flow rate, microdrop volume, pH and extraction time were investigated, and the optimized microextraction conditions were established. The experimental results indicated that in a pH range of 5.0–7.5 labile monomeric Al species (free Al (Al3+, AlOH2+, and Al(OH)2+)) could be extracted by the 8-HQ–chloroform microdrop while non-labile monomeric Al species (Al–citrate, Al–SO4, Al–F, Al–EDTA, Al–humic) directly passed through the microdrop. Labile aluminium in the post-extraction organic phase was directly determined by ETV-ICP-MS. The total Al was determined using pneumatic nebulization (PN)-ICP-MS. The non-labile aluminium was obtained by subtraction of labile aluminium from the total aluminium. Under the optimized conditions, the detection limit of the method was 3.3 pg mL−1 and the relative standard deviation for 1 ng mL−1 of Al was 10%. After 8 min of extraction, the enrichment factor was 210. The proposed method has been successfully applied to the determination of Al species in natural water, coffee and tea infusions. The results were comparable with that obtained by the 8-HQ loaded silanized silica gel microcolumn system and conventional liquid–liquid extraction system.

Speciation of Aluminum in Drink Samples by 8-Hydroxyquinoline Loaded Silylanization Silica Gel Microcolumn Separation with Off-Line ICP-MS Detection

A technique using a flow injection microcolumn separation coupled with ICP-MS detection has been developed for the speciation of Al in drink samples. The retention behaviors of different Al species were studied with 8-hydroxyquinoline (8-HQ) loaded silylanization silica gel as the packing material and inorganic acid (HNO3) as the elution. The results indicated that in a pH range of 5.0 to 8.0, all labile monomeric Al species were retained on the microcolumn while nonlabile monomeric Al species were directly passed through the column. Various Al species after separation were detected by ICP-MS. The detection limit of 0.2 ng mL(-1) and a relative standard deviation (RSD) of 4.2% at 10 ng mL(-1) (n = 11) were achieved, and the recoveries for the spiked samples were 95-108%. The proposed method has been applied to the analysis of Al species in tea infusions, coffee, and tap waters with satisfactory results. The results obtained by this method were compared with that obtained by the cation exchange microcolumn separation and ICP-MS detection system, and some valuable conclusions were drawn.

Nonaqueous based microchip separation of toxic metal ions using 2-(5-bromo-2-pyridylazo)-5-( N-propyl- N-sulfopropylamino)phenol

The colorimetric metal chelating agent, 2-(5-bromo-2-pyridylazo)-5-( N-propyl- N-sulfopropylamino)phenol (5-Br-PAPS), was demonstrated on a capillary electrophoresis microchip in the separation and detection of six metal ions of environmental concern, Cd 2+, Pb 2+, Cu 2+, Co 2+, Ni 2+, and Hg 2+. The inclusion of methanol in the buffer was found to improve both the separation efficiency and sensitivity, in addition to making the technique directly amenable to the application of solid-phase extraction. The combination of metal chelation with solid-phase extraction on a C 18 silica gel microcolumn gave several hundred fold improvements in detection limits for the CE microchip measurements of toxic metal ions in water and extracted from a solid Plexiglas surface.

Particulate matter size distribution and associated polycyclic aromatic hydrocarbon content from indirect and direct injection diesel engines

Within the framework of atmospheric aerosol study, evaluation of the contribution of the particle source to global atmospheric pollution is a challenge that requires an improvement in the knowledge of particulate matter. As a part of this knowledge improvement, this study has been focused on particles emitted from diesel vehicles. Two light-duty diesel vehicles were studied for particulate matter size distribution and associated polycyclic aromatic hydrocarbon (PAH) content. A diffusional and inertial spectrometer was used, allowing particles from 7.5 nm to 15 μm to be collected and analysed. Teflon-coated glass fibre filters were employed as collector substrates, and weighed prior to and after sampling. Each of them was extracted with methylene chloride in an accelerated solvent extractor, cleaned on a silica gel micro-column and analysed for PAH by gas chromatography/mass spectrometry using internal standards for quantitation. Both analytical and sampling methods were validated. The highest particle mass was found to be emitted at 0.2 μm for the direct injection engine and 0.07 μm for the indirect injection engine. PAHs were found to be essentially distributed on particles in the accumulation mode, at about 0.2 μm, and high molecular weight PAH distributions were found to be bimodal or trimodal, depending on the engine injection.

Passage of the bracken fern carcinogen ptaquiloside into bovine milk

Summary - Ptaquiloside has been discovered for the first time in milk samples 01 a bovine fed a dietary complement (6 kg fresh weighVday) of freshly-eut bracken fronds. This was equivalent to ca 216 mg/day pure ptaquiloside. The compound was found in a quantity of no less than 0.11 mg/I in milk. This was determined by the appearance of pterosin 6 - the decomposition product of ptaquiloside - in prepurified milk sampi es treated with milg 1I1kllii (pH 8.0 and 11.5). The lack of base treatment led to the absence of pterosin B. A mi!kj}rilpurlflcatlon protocol based on meth,anol-acetonitrile precipitations in succession, hexllne and dlchloromethane extractions, alkaline treatment, reextraction and silica gel microcolumn chromatography followed by reverse-phase HPLC was developed for the detection 01 ptaquiloside.

Ontogenic variation of biologically active metabolites ofPteridium aquilinum (L. Kuhn) pterosins A and B, and ptaquiloside in a bracken population of the tropical andes

A negative correlation has been found between the amounts of pterosins A and B and ptaquiloside per biomass unit, and the growth stage of the blade of bracken. Their concentration decreased progressively from the crozierto the mature frond, where it attained less than 5% of the initial value. The growth was measured following the total blade length, its height, moisture content, and time of emergence from the soil surface. Quantitation of these compounds was achieved by HPLC using a water extraction, methylene chloride treatment, and silica gel microcolumn cleanup sequence. Pterosins were unevenly distributed in the blade, whereas ptaquiloside maintained a constant concentration throughout. Rhizomes contained only minor amounts of these compounds. Their possible role as semiochemicals in bracken is discussed.

Fluorimetric determination of uranium(VI) in waters by flow-injection analysis after preconcentration on a silica gel microcolumn

A method was developed for the selective determination of trace concentrations of uranium(VI) by flow-injection analysis (FIA) with fluorimetric detection. Uranium(VI) is selectively separated and/or pre-concentrated from a volume up to 20 ml on an activated silica gel microcolumn (2 × 40 mm) from a medium of 0.03 M EDTA, 0.06 M tartrate, and/or 0.05 M NaF at pH = 9.3. After washing the column the uranium is eluted with a mixture of 1.33 M sulphuric and phosphoric acids and determined with a relative standard deviation not exceeding 6% for concentrations in the range 10–250 μg/l. The detection limit was estimated to be 0.1–0.2 μg of uranium. The method has been verified on artificial water samples with high content of the interfering elements and applied to analysis of waste and natural waters.

Quantitation of pterosins A and B, and ptaquiloside, the main carcinogen of pteridium aquilinum (L. Kuhn), by high pressure liquid chromatography

AbstractA quantitative method for the assessment of ptaquiloside and pterosins A and B in bracken fern has been developed. The technique involves quantitative extraction of fresh plant tissue, base‐induced decomposition of ptaquiloside to pterosin B, followed by prepurification of products on a silica gel microcolumn and quantitative high pressure liquid chromatography. The method has been used to estimate the contents of these norsequiter‐penes in fronds and rhizomes of Pteridium aquilinum var. caudatum from northern South America.

Separation of pesticides, related compounds, polychlorobiphenyls and other pollutants into four groups by silica-gel microcolumn chromatography (application to surface water analysis)

Multi-residue analyses of pesticides and related compounds generally require clean-up procedures for the elimination of interfering substances. An analytical procedure for use in the recovery and determination of pesticides and other pollutants in water samples is described, in which the purification of the extracts is improved by the separation of pesticides into four groups. The separation of pesticides by silica-gel microcolumn chromatography is explained in detail.

Fluorimetric determination of beryllium with 3-hydroxy-2-naphthoic acid by flow injection analysis after preconcentration on a silica gel microcolumn

A method was worked out for the selective determination of trace concentrations of beryllium by flow injection analysis (FIA) with fluorimetric detection using 3-hydroxy-2-naphthoic acid (λex = 375 nm, λem = 455 nm) at cL = 50 μmol l-1 in 0.1M ammonium acetate, pH 7·1. In injected sample volumes of 80 μl, Be can be determined in concentrations of 10 to 156 μg l-1 with relative standard deviations not exceeding 5%, after its selective sorption on a microcolumn (2 x 40 or 3 x 30 mm) of silica gel from a medium of 0.05M-EDTA and 0.1M tartaric acid followed by elution with 0.1M-HCl. After preconcentration from 5 to 15 ml volumes, Be can be determined under the same conditions in samples at concentrations of ρBe = 0.5 to 4.6 or 0.1 to 0.8 μg l-1, respectively, with sr from 6 to 12%, the enrichment factor being as high as 200. The method was applied to beryllium bronzes and to dust from the atmosphere of the beryllium bronze foundry. The relative deviations of the beryllium content did not exceed 8% for the bronzes as compared to certified values, and 5% for the dust as compared to results obtained by ETA AAS.

Liquid Chromatography of Isomeric Phenols and Aromatic Acids Using a Poly (Ethyleneimine) Coated Silica Gel Micro-Column

Abstract Ortho-, meta- and para-isomers of various derivatives of phenols and aromatic acids have been separated on a cross-linked poly (ethyleneimine) coated silica gel micro-column liquid chromatography with very dilute carbonate or phosphate eluents.

Application of capillary gas chromatography mass spectrometry/computer techniques to synoptic survey of organic material in bed sediment

A bed sediment sample taken from an area impacted by heavy industrial activity was analyzed for organic compounds of environmental significance. Extraction was effected on a Soxhlet apparatus using a freeze-dried sample. The Soxhlet extract was fractionated by silica gel micro-column adsorption chromatography. Separation and identification of the organic compounds was accomplished by capillary gas chromatography/mass spectrometry techniques. More than 50 compounds were identified; these include saturated hydrocarbons, olefins, aromatic hydrocarbons, alkylated polycyclic aromatic hydrocarbons, and oxygenated compounds such as aldehydes and ketones. The role of bed sediments as a source or sink for organic pollutants is discussed.

Analysis of Pesticide Residues by Chemical Derivatization. II. N-Methylcarbamates in Natural Water and Soils

A method for the quantitative determination of several N-methylcarbamates in natural waters and the applicability of the derivative to soil samples using a previously published extraction procedure are described. After extraction of the carbamates from the substrate, the carbamates are hydrolyzed in a 10% methanol-potassium hydroxide solution to form the phenolic hydrolysis products, which are isolated and derivatized with pentafluorobenzyl (PFB) bromide to produce the PFB ether derivatives. The PFB derivatives are cleaned up and fractionated on a silica gel microcolumn and determined by electron capture gas-liquid chromatography (GLC). Eight organophosphate pesticides and 2 phthalate acid esters that hydrolyze to phenols or phthalic acid were evaluated as potential interferences and were found not to interfere with any of the carbamates tested. Quantitative determinations of 0.1 mug carbofuran and 3-ketocarbofuran and 0.5 mug carbaryl, metmercapturon, and Mobam in a 1 L water sample are possible. Propoxur was not determined at levels less than 1 mug/L due to the short GLC retention time of the derivative and interferences from the reagents at the lower levels.

Confirmation of pesticide residue identity: part IX. Organophosphorus pesticides.

This paper describes a confirmation procedure for residue levels of dyfonate, dichlorofenthion and cyanox. After extraction and quantitation by flame photometric detector (FPD)-gas liquid chromatography (GLC), the organophosphorus pesticides are hydrolyzed in a 10% methanolic-potassium hydroxide solution. The phenolic hydrolysis products are then extracted from this solution and reacted with pentafluorobenzyl bromide to produce the pentafluorobenzyl (PFB) ether derivatives. These PFB ethers are subsequently cleaned-up and fractionated on a silica gel micro-column and analyzed by electron capture (EC)- GLC.

Confirmation of Pesticide Residue Identity. VIII. Organophosphorus Pesticides

Abstract A chemical confirmation for 5 organophosphorus pesticides is described. After extraction and quantitation by flame photometric detector gas-liquid chromatography (CLC), the organophosphorus pesticides are hydrolyzed in a 10% methanolic-potassium hydroxide solution, followed by derivatization with pentafluorobenzyl bromide to produce the pentafluorobenzyl (PFB) ethers of the phenolic hydrolysis products. The PFB ethers are subsequently fractionated on a silica gel microcolumn, and analyzed by electron capture GLC. The preliminary chromatographic results of the electron capture GLC analysis of the PFB ethers of the phenolic hydrolysis products of several N-methylcarbamates are also presented. As little as 0.01 ppb ronnel and crufomate and 0.10 ppb parathion, fenitrothion, and methyl parathion in a 1 L water sample can be confirmed.

Polychlorinated biphenyls: Distribution and storage in body fluids and tissues of Sherman rats

An analytical method for determination of PCB (Aroclor 1254) in blood, urine, feces, and tissues of Sherman strain rats after prolonged dietary intake (100, 500, and 1000 ppm) is presented. The method involves homogenization and extraction with hexane, cleanup on a silica gel microcolumn and analysis by electron-capture gasliquid chromatography. Recovery data are shown at 0.1, 5, 14, and 100 ppm. Mass spectroscopic characteristics of PCB in tissues are given. Distribution, storage, and excretion rates during feeding and after discontinuance of PCB in the diet are presented.

The separation of fifty pesticides and related compounds and polychlorobiphenyls into four groups by silica gel microcolumn chromatography

An analytical scheme used in the study of the pollution of surface water by pesticides in Italy is described, and the separation of pesticides and polychlorobiphenyls into four groups by chromatography on a silica gel microcolumn is explained in detail. The advantages of the more accurate gas-chromatographic identification of pesticides present in the fractions eluted from silica gel are shown. Several organophosphorus pesticides were also identified in the waters by the technique described, the persistence of which in the environment had not previously been suspected.

Air sampling and analysis with microcolumns of silica gel.

Abstract This paper describes a simple microcolumn of silica gel, its behavior under experimental conditions and its applicability to air sampling. Data are presented for the ultraviolet spectral absorbance analysis of selected aromatic hydrocarbons, using a base line correction for background interference. The problems of direct silica gel elution and ultraviolet spectrophotometry are discussed, and resolution of the particulate background problem by base line calculations is shown. The silica gel microcolumn is proved simple, practical, and highly efficient for sampling air contaminants. Although only spectrophotometric analysis of eluates is reported here, other methods of analyzing the sorbed contaminant are suggested.

Silica Gel Microcolumn for Chromatographic Resolution of Cortical Steroids

Silica Gel Microcolumn for Chromatographic Resolution of Cortical Steroids