Gel Microcolumn Research Articles

Study and application of a method for the determination of metallic elements by ICP-AES with preconcentration on an active carbon-silica gel microcolumn in a FI system

Using active carbon-silica gel as adsorbent and sodium diethyldithiocarbamate (NaDDTC) as chelating reagent in a flow injection system, an ICP-AES method has been developed for preconcentration and determination of trace metallic elements in high purity rare earth oxides. The experimental parameters such as pH, flow rate, amount of adsorbent, length of reaction coil and eluent acidity were optimized. At pH 4.6 Al,Cr,Cu,Fe,Pb,V,Zn could be preconcentrated, and subsequently determined by ICP-AES. This method can eliminate matrix effects. Its enrichment factors were 8.1–12.6 with detection limits in the ng/mL range and RSD of 2.3–5.0. This method was applied to the analysis of high purity of La2O3 and Eu2O3 with satisfactory results.

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.

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.

Rapid and reliable separation of 5α-dihydrotestosterone from testosterone on silica gel microcolumns

Rapid and reliable separation of 5α-dihydrotestosterone from testosterone on silica gel microcolumns

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