Recent developments in the evaluation of chemically bonded silica packings for liquid chromatography

Unger, Klaus K.; Becker, N.; Roumeliotis, P.

doi:10.1016/s0021-9673(00)93815-9

Cited by 322 publications

(63 citation statements)

References 14 publications

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“…The difference in nitrogen content between the TCPP-based silica and the original aminopropyl-silica phase is 6.67% and this content corresponds to a porphyrin coverage of 5.6 µmol m -2 according to general equation proposed by Unger et al 22 To establish the possibility of application of Si-NH2-TCPP sorbent, we investigated the elution of TCPP by mineral acids and base solutions. The portions of appropriate eluent at different concentrations were passed through the columns containing 0.1 g of this sorbent.…”

Section: Characterization Of the Tcpp-loaded Silica Gelmentioning

confidence: 99%

Sorption Behavior of Vanadium on Silica Gel Modified with Tetrakis(4-carboxyphenyl)porphyrin

Pyrzyńska

Wierzbicki

2005

ANAL. SCI.

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IntroductionFor the purpose of separation of metal ions, either for purification or preconcentration, various kinds of chelating resins have been developed. This has been the subject of numerous papers and reviews related to synthesis, characterization and metal ion uptake studies. [1][2][3][4] The insertion of suitable specific functional groups into solid matrices makes them capable of reacting with metal species under certain favorable conditions to form metal complexes. One of the most used supports is silica gel due to its good mechanical, thermal and chemical stability as well as excellent swelling resistance in different solvents. 4,5 Synthesis and application of silica gel phases loaded with various organic reagents for preconcentration of metal ions have been reviewed by Jal et al. 4 Additionally, several new reagents like dimethylglyoxime, 6 4-aminoantipyrene, 7 5-formyl-3-(1′-carboxyphenylazo) salicylic acid, 8 2-aminothiazol 9 and dendrimer-like polyamidoamine 10 have been recently reported for the chemical modification of silica surface.Unfortunately, the modified silica phases have not been studied for selective extraction and enrichment of vanadium. For this purpose chelating resins 11-14 and several modified polymers [15][16][17] have usually been applied. Determination of vanadium at trace levels is important for monitoring pollution as well as for understanding its geochemical and biological effects. However, when the level of this metal in real samples is very low, a preconcentration/separation step is necessary to improve the precision and accuracy.18 Moreover, the procedures based on sorption principles are very useful for separation of vanadium species as V(IV) and V(V), two main forms present in natural waters, which have different nutritional and toxic properties.In the present study, modified silica gel was used for the solid phase extraction of vanadium. Tetrakis(4-carboxyphenyl)-porphyrin (TCPP) was chosen as a complexing reagent as it forms stable complexes with vanadium. Vanadyl porphyrins occur for example in fossil fuels. 19 The silica surface was modified by physical adsorption and by direct chemical immobilization through formation of an amide bond. The resulting chelating sorbents have been studied for separation and preconcentration of vanadium species. Experimental Reagents and apparatusThe chemicals used were of analytical grade, and all solutions were prepared with deionized water obtained from a Milli-Q system (Millipore).A commercial atomic absorption standard solution (Merck) containing 1000 mg L -1 of V(IV) (VOSO4 in 0.5 mol L -1 H2SO4) was used. Vanadium(V) solutions were prepared by dissolving V2O5 in 1% (v/v) HNO3.5,10,15,20-Tetrakis(4-carboxyphenyl)porphyrin (TCPP) from Fluka was used without further purification.A Perkin Elmer Model AAnalyst 300 atomic absorption spectrometer equipped with a deuterium background correction system utilized the vanadium 318.5 nm line. HGA-800 furnace and pyrolytically coated graphite tubes were employed. The instrumental settings...

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Section: Characterization Of the Tcpp-loaded Silica Gelmentioning

confidence: 99%

Sorption Behavior of Vanadium on Silica Gel Modified with Tetrakis(4-carboxyphenyl)porphyrin

Pyrzyńska

Wierzbicki

2005

ANAL. SCI.

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“…In spite of the cares, the laser light can be diffused, particularly by the prism and can reach the photomultiplier. Black screens (11) were then placed in order to dissociate the excitation part (laser) from the emission one (fluorescence) of the set-up. A silica-silicon optical fiber (12), of 1 mm diameter and 2 m length, connected the fluorimeter to the optrode.…”

Section: Optical Device and Optrode Set-upmentioning

confidence: 99%

“…The following silanization reaction governs the final grafting quality. The process was a condensation reaction between the surface silanols and the siloxane part of APTES, with the concomitant elimination of APTES ethoxy groups (one or two, but never three [11]). When it occurred with water traces, it ensued the hydrolysis of the silane leading to the uncontrolled formation of a polysiloxane network [12].…”

Section: Covalent Immobilization Of Fluorescein On the Optical Fibermentioning

confidence: 99%

Nitrate fluorimetric analysis using an active optical fiber

Mahieuxe¹,

Carré²,

André³

et al. 1999

Analusis

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These last past years, nitrate ions have been in vogue pollutants because often incriminated in aquatic pollutions. Very currently used as chemical fertilizers, nitrate can be transformed, when ingested, into carcinogenic nitrosamines in the human body. So it is necessary to monitor the concentrations of these anions, even as traces, particularly in drinking waters or in order to prevent pollution accidents in environmental waters. We recall that the recommanded nitrate concentration by the European Community for drinking water is less than 50 mg NO 3 -L -1 .Besides several methods (ion chromatography, absorption spectrometry, etc. [1,2]), fluorimetry is generally described as a very sensitive, selective, simple and quick technique (see reference 3 for a review). Moreover, use of an optical fiber would allow both remote excitation and fluorescence emission guiding. Then, our objective was to develop a sensor based on fluorescence measurements as a system currently able to rapidly measure, in situ and specifically, low nitrate rates.Following a large bibliographical study [3], a fluorimetric method for the determination of nitrate was selected and particularly the one using fluorescein as a fluorescent indicator [4,5]. Fluorescein advantages are its non toxicity and the fact that it has several commercially available derivatives, making easier its covalent immobilization on an optical fiber. The method consists in the determination of nitrate ions in concentrated sulfuric acid, by measuring their quenching effect on the fluorescence of fluorescein, owing to the formation of a non fluorescent dinitrated compound, as indicated in figure 1. The analysis of nitrate ions in homogeneous acidic medium was largely studied [4,5] and we reproduced the method with our own equipment. Even the acidic medium, the study of the fluorescence emission is still possible, of course the fluorescence characteristics have changed: lower quantum yield and blue shift of the emission [6].With the idea of the development of an active optrode, the major drawback is the requirement of concentrated sulfuric acid, 89% minimum, which might be harmful for its stability. Therefore, to obtain a more stable optrode regarding the immobilization of fluorescein, it would be preferable to create a covalent bond. The three required steps for a covalent immobilization of fluorescein on the silica tip of the optical fiber are summarized in figure 2. Such a fixation would prevent or at least limit the desorption or wash out phenomena which would happen for the optrode using in a highly aggressive media, such as 95 % sulfuric acid. Two minor disadvantages are respectively the too long reaction time (i.e. 45 min; in fact we will show that this time might be reduced to 30 min) and the irreversibility of the reaction which will limit the method to an integrating sensor. 735Nitrate fluorimetric analysis using an active optical fiber Abstract. With the objective to use a fluorimetric determination of nitrate based on fluorescein as the sensitive fluorescent indi...

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“…Because the entire structure of the particle backbone has a distributive hydrophobicity, the result is a rugged hybrid (inorganic/organic) particle. The process for making these hybrid materials is illustrated in Equation (1) [11].…”

Section: Introductionmentioning

confidence: 99%

“…These particles can then be surface-bonded and nonpolar groups (e.g., C18, C8) are attached. Therefore, such particles combine the properties of the broad pH tolerance of polymer-based packing materials with the full range benefits of silica-based packings [11]. Surface characterization of chemically bonded stationary phases for chromatography has been performed using cross-polarization and magic-angle spinning (CP-MAS) NMR [12][13][14][15][16][17][18][19][20][21][22][23][24][25].…”

Section: Introductionmentioning

confidence: 99%

Surface Characterization of Some Novel Bonded Phase Packing Materials for HPLC Columns Using MAS-NMR Spectroscopy

Abia

2015

Chromatography

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Information on the surface properties of three novel chemically bonded phase packing materials for High performance liquid chromatography (HPLC) were obtained using spectra obtained by solid state cross-polarization (CP) magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopic experiments for the 29 Si, and 13 C nuclei. These packing materials were: Cogent bidentate C18 bonded to type-C silica, hybrid packing materials XTerra MS C18, and XBridge Prep. C18. The spectra obtained using cross-polarization magic angle spinning (CP-MAS) on the Cogent bidentate C18 bonded to type-C silica show the surface to be densely populated with hydride groups (Si-H), with a relative surface coverage exceeding 80%. The hybrid packing materials XTerra and XBridge gave spectra that reveal the silicon atoms to be bonded to organic moieties embedded in the molecular structure of these materials with over 90% of the alkyl silicon atoms found within the completely condensed silicon environments. The hydrolytic stability of these materials were investigated in acidic aqueous solutions at pHs of 7.0 and 3.0, and it was found that while the samples of XTerra and XBridge were not affected by hydrolysis at this pH range, the sample of Cogent lost a significant proportion of its Si-H groups after five days of treatment in acidic aqueous solution.

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Recent developments in the evaluation of chemically bonded silica packings for liquid chromatography

Cited by 322 publications

References 14 publications

Sorption Behavior of Vanadium on Silica Gel Modified with Tetrakis(4-carboxyphenyl)porphyrin

Sorption Behavior of Vanadium on Silica Gel Modified with Tetrakis(4-carboxyphenyl)porphyrin

Nitrate fluorimetric analysis using an active optical fiber

Surface Characterization of Some Novel Bonded Phase Packing Materials for HPLC Columns Using MAS-NMR Spectroscopy

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