Adsorption of Triazine Derivatives with Humic Fraction-Immobilized Silica Gel in Hexane: A Mechanistic Consideration

Hu, Shun-Wei; Chen, Shushi

doi:10.1021/jf4019118

Cited by 11 publications

(10 citation statements)

References 49 publications

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“…Furthermore, the adsorption capacities determined for these analytes would have been different from those listed in Table 1 . The adsorption capacities were determined to be larger than those previously reported for organophosphate pesticides on humic-fraction-modified silica gel in hexane, and were of approximately the same order of magnitude as that reported for the adsorption of triazines on a lignin-modified adsorbent in hexane [ 20 ]. In the cited studies, the adsorption was determined to have resulted from intense dipole-dipole interactions (e.g., hydrogen bonding) between the analytes and the adsorbent molecules in hexane.…”

Section: Resultsmentioning

confidence: 73%

Study of Lignin-Modified Silica Gel Adsorption after Association with Six Different Organophenylmercuric Compounds in Chloroform

Chen

Gao

2018

IJMS

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In this study, the adsorption of lignin-modified silica gel after association with six different organophenylmercuric compounds in chloroform was investigated. Adsorption reached approximately 90% of the maximum value within 15 min. The adsorption capacity, Fourier transform infrared spectroscopy, and interaction simulation results indicated that the adsorption proportion resulted from the strong dipole-dipole interaction between the lignin and analyte molecules, and was considered to be size- and structure-dependent. However, the π-π complexation interaction arising from the acidic aromatic moiety of the analyte, which was significant in an apolar environment, was not the major force responsible for the resulting adsorption. Additives, such as acid or ether, which competed with the analyte for the binding site on the lignin molecule, were not beneficial to the interaction, and thus not beneficial to the adsorption processes.

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Section: Resultsmentioning

confidence: 73%

Study of Lignin-Modified Silica Gel Adsorption after Association with Six Different Organophenylmercuric Compounds in Chloroform

Chen

Gao

2018

IJMS

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“…However, as Table shows, a force leading to adsorptions in acetonitrile and hexane, as described in previous studies, was not observed in fluorescence quenching data. The percentages of adsorption and adsorption capacity are listed in Table for comparison and interpretation purposes . The fluorescence emission spectra of several analytes in Table overlap; these are depicted in Figure , which provides a visual and conceptual representation of fluorescence intensity attenuation versus wavelength.…”

Section: Resultsmentioning

confidence: 99%

Fluorescence quenching study of humic‐fraction‐modified silica gel in a solid state after association with a variety of pesticidal analytes in hexane and acetonitrile

Gao¹,

Chen²

2018

J Chinese Chemical Soc

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In this paper, we investigate the fluorescence quenching of acidic humic-fractionmodified silica gel in the solid state after association with a variety of pesticidal analytes in hexane and acetonitrile. The percentage of fluorescence quenching is found to be dependent on the contact time and linearly on the number of moles of analyte involved in the association process. However, any π-π complexation interaction arising from the acidic aromatic ring on the analyte due to the derivatization of a bulky electron-withdrawing group is not observed. Also, any mechanism leading to adsorption or any quenching process occurring as a result of the steric hindrance obtained by a theoretical interaction simulation is not observed. The Fourier transform infrared (FTIR) data and simulation results, instead, suggest that electron-rich atoms on the analyte, such as oxygen, sulfur, nitrogen, and phosphorus, are responsible for fluorescence quenching, following dipole-dipole interaction with the humic-fraction-modified adsorbent. K E Y W O R D S electron-rich atom, electron-withdrawing group, fluorescence quenching, humicfraction-modified silica gel, theoretical interaction simulation, π-π complexation 1 | INTRODUCTIONThe oxygen molecule is one of the most efficient collisional quenchers because it quenches almost all known fluorophores. [1] Other collisional quenchers, such as aromatic and aliphatic amines, are also efficient for most unsubstituted aromatic hydrocarbons. Other types of collisional quenchers are heavy atoms such as iodine and bromine. However, for larger halogens such as these, in contrast to intersystem crossing to an excited triplet state, a requirement for collisional quenching may be the quenching mechanism rather than molecular contact. For chlorinated hydrocarbons and electron scavengers, such as the proton and divalent ions such as Cu 2+ , the fluorophore is quenched by the withdrawal of an electron. A typical example is the fluorescence quenching of humic acid in the presence of several divalent ions such as Cu 2+ , Al 2+ , Mg 2+ , Mn 2+ , Zn 2+ , and Ni 2+ . [2][3][4][5][6][7][8] The effect of pH on the fluorescence spectra of humic acidlike soil fungal polymers has also been investigated. [9] In this study, we measured the fluorescence quenching of humic-fraction-modified silica gel in the solid state before and after the adsorption of various pesticidal analytes in haxane and acetonitrile. Based on the quenching results, a quantitative analysis was conducted on the percentage of fluorescence quenching, which was dependent on the contact time. The relevance of the number of moles of analyte involved in the quenching process was also considered. Finally, Fourier transform infrared (FTIR) data were collected to clarify the mechanism of solid-state fluorescence quenching.

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“…Acetonitrile is less favorable in that respect. The other practical consideration for a successful extraction process is that the adsorption of triazine analogs on the lignin-modified absorbent was only observed in hexane [55]. The solvent mixture of hexane and methylene chloride (1:1, v / v ) was also used in the evaluation of adsorbing aflatoxins in this study.…”

Section: Resultsmentioning

confidence: 99%

“…Note that the percentage of adsorption for aflatoxins was near 100% in a hexane/methylene chloride mixture (1:1, v / v ). Two adsorption mechanisms reported previously were thought to be responsible for the extraction results, and also led to the variation in the adsorption capacity values for these analytes, as shown in Table 3 [55,56]. The availability of binding sites on the lignin-modified adsorbent (i.e., ether linkage in hexane) and the size of the analyte molecule are factors believed to be particularly responsible for the extraction results, according to the proposed structure of lignin [37,42,56,57,58].…”

Section: Resultsmentioning

confidence: 99%

Large-Scale Membrane- and Lignin-Modified Adsorbent-Assisted Extraction and Preconcentration of Triazine Analogs and Aflatoxins

Chen

2017

IJMS

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The large-scale simultaneous extraction and concentration of aqueous solutions of triazine analogs, and aflatoxins, through a hydrocarbon-based membrane (e.g., polyethylene, polyethylene/polypropylene copolymer) under ambient temperature and atmospheric pressure is reported. The subsequent adsorption of analyte in the extraction chamber over the lignin-modified silica gel facilitates the process by reducing the operating time. The maximum adsorption capacity values for triazine analogs and aflatoxins are mainly adsorption mechanism-dependent and were calculated to be 0.432 and 0.297 mg/10 mg, respectively. The permeation, and therefore the percentage of analyte extracted, ranges from 1% to almost 100%, and varies among the solvents examined. It is considered to be vapor pressure- and chemical polarity-dependent, and is thus highly affected by the nature and thickness of the membrane, the discrepancy in the solubility values of the analyte between the two liquid phases, and the amount of adsorbent used in the process. A dependence on the size of the analyte was observed in the adsorption capacity measurement, but not in the extraction process. The theoretical interaction simulation and FTIR data show that the planar aflatoxin molecule releases much more energy when facing toward the membrane molecule when approaching it, and the mechanism leading to the adsorption.

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Adsorption of Triazine Derivatives with Humic Fraction-Immobilized Silica Gel in Hexane: A Mechanistic Consideration

Cited by 11 publications

References 49 publications

Study of Lignin-Modified Silica Gel Adsorption after Association with Six Different Organophenylmercuric Compounds in Chloroform

Study of Lignin-Modified Silica Gel Adsorption after Association with Six Different Organophenylmercuric Compounds in Chloroform

Fluorescence quenching study of humic‐fraction‐modified silica gel in a solid state after association with a variety of pesticidal analytes in hexane and acetonitrile

Large-Scale Membrane- and Lignin-Modified Adsorbent-Assisted Extraction and Preconcentration of Triazine Analogs and Aflatoxins

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