On-line electrochemical reagent production for fluorescence detection of phenothiazines in liquid chromatography

Kok, Wim Th.; Voogt, W.H.; Brinkman, U.A.Th.; Frei, R.W.

doi:10.1016/s0021-9673(01)87026-6

Cited by 27 publications

(7 citation statements)

References 14 publications

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“…25 Electrochemically generated bromine was used as oxidizing agent by Kok et al and the LOD was 0.8 ng. 27 Quantification of Phenothiazine. For phenothiazine, there is a stable colored radical cation as well as a fluorescent sulfoxide.…”

Section: Resultsmentioning

confidence: 99%

“…High-performance liquid chromatographic (HPLC) methods for the postcolumn oxidation of phenothiazines with subsequent fluorometric detection has been long known. [24][25][26][27] A method for the determination of phenothiazine and 11 of its derivatives with postcolumn chemical oxidation by peroxyacetic acid to the respective sulfoxides has been published recently. 14 Our goal, based on this method, was to simplify the technical setup without sacrificing sensitivity.…”

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confidence: 99%

“…Coupling a chromatographic procedure with an oxidation step is therefore an attractive option to increase selectivity and to gain sensitivity, for example, in conjunction with a postcolumn derivatization to the fluorescent product. High-performance liquid chromatographic (HPLC) methods for the postcolumn oxidation of phenothiazines with subsequent fluorometric detection has been long known. − A method for the determination of phenothiazine and 11 of its derivatives with postcolumn chemical oxidation by peroxyacetic acid to the respective sulfoxides has been published recently …”

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Analysis of Phenothiazine and Its Derivatives Using LC/Electrochemistry/MS and LC/Electrochemistry/Fluorescence

Hayen

Kärst

2003

Anal. Chem.

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The on-line electrochemical conversion of phenothiazine and its derivatives after liquid chromatographic separation has been studied by mass spectrometry and fluorescence spectroscopy. In an electrochemical cell consisting of porous glassy carbon, the phenothiazines are readily converted to oxidized products, which can be detected by on-line fluorescence spectroscopy and mass spectrometry. The method allows rapid investigations on the electrochemical oxidation pathways, as demonstrated for phenothiazine itself. The phenothiazine derivatives are transferred into their strongly fluorescent sulfoxides. Based on this reaction, an LC/electrochemistry/fluorescence method was developed that allows for limits of detection between 5 x 10(-9) and 4 x 10(-8) mol/L and limits of quantification between 2 x 10(-8) and 1 x 10(-7) mol/L for the individual phenothiazines. The linear ranges comprised three decades starting at the limit of quantification.

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Analysis of Phenothiazine and Its Derivatives Using LC/Electrochemistry/MS and LC/Electrochemistry/Fluorescence

Hayen

Kärst

2003

Anal. Chem.

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“…As a result, AFs were converted into fluorescent hemiacetals, which are similar compounds to those obtained by the derivatization using TFA (Garcia-Villanova et al, 2004; Torres et al, 1995). The response sensitivity of AFs in aqueous solutions could be increased using other oxidizing reagents such as iodine and phenothiazines (Davis et al, 1981; Jansen et al, 1987; Kok et al, 1986). However, bromine was preferred over iodine due to its stronger oxidizing ability.…”

Section: Resultsmentioning

confidence: 99%

Development and validation of a high-performance liquid chromatography method with post-column derivatization for the detection of aflatoxins in cereals and grains

Asghar¹,

Iqbal²,

Ahmed³

et al. 2014

Toxicol Ind Health

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A novel, reliable and rapid high-performance liquid chromatography (HPLC) method with post-column derivatization was developed and validated. The HPLC method was used for the simultaneous determination of aflatoxin B1 (AFB1), B2 (AFB2), G1 (AFG1) and G2 (AFG2) in various cereals and grains. Samples were extracted with 80:20 (v/v) methanol:water and purified using C18 (40-63 μm) solid-phase extraction cartridges. AFs were separated using a LiChroCART-RP-18 (5 μm, 250 × 4.0 mm(2)) column. The mobile phase consisted of methanol:acetonitrile:buffer (17.5:17.5:65 v/v) (pH 7.4) delivered at the flow rate of 1.0 mL min(-1) The fluorescence of each AF was detected at λex = 365 nm and λem = 435 nm. All four AFs were properly resolved within the total run time of 20 min. The established method was extensively validated as a final verification of the method development by the evaluation of selectivity (AFB1, AFB2, AFG1 and AFG2), linearity (R(2) ≥ 0.9994), precision (average SD ≤ 2.79), accuracy (relative mean error ≤ -5.51), robustness (p < 0.0080), ruggedness (p < 0.0100) and average recoveries (89.2-97.8%). The limits of quantification of AFB1, AFB2, AFG1 and AFG2 were 0.080, 0.073, 0.062 and 0.066 ng g(-1), respectively. Finally, the developed method was applied for the analysis of AFs in 45 samples comprising rice (n = 20), wheat (n = 15) and maize (n = 10). The results showed that 65% of rice, 20% of wheat and 80% of maize samples were found contaminated with AFs. Thus, according to the achieved results, it is suggested that the newly developed HPLC method could be effectively applied for the routine analysis of the AFs in different cereals and grains.

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“…(314) An analogous method has been reported for phenothiazines, such as thioridazine; however, the resultant products from the oxidation reaction with bromine are detected fluorimetrically. (315) Photochemical activation of phenothiazines and demoxepam in 2 min and subsequent fluorescence detection provided detection limits a factor of 10 better than UV detection. (316) Applications of photochemical reactors to a variety of pharmaceuticals, such as phenothiazines, have been summarized.…”

Section: Sulfur Compoundsmentioning

confidence: 99%

Chemical Reagents and Derivatization Procedures in Drug Analysis

Danielson

Gallagher

Bao

2008

Encyclopedia of Analytical Chemistry

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This article describes both pre‐ and postcolumn derivatization chemistry used in conjunction with either chromatography or capillary electrophoresis (CE) to facilitate the determination of drugs. Generally, only prederivatization is used in gas chromatography (GC), principally to enhance the volatility, temperature stability, and/or detectability. The GC section considers derivatization of drugs by reagent class: alkylation, acylation, and silylation. The GC sample‐handling section describes an approach that combines the extraction and derivatization steps together. Both pre‐ and postcolumn derivatization are common approaches for high‐performance liquid chromatography (HPLC) and many of these methods have been adapted for CE. Derivatization for HPLC is often directed toward aliphatic amines, carboxylic acids, or alcohols that are difficult to detect at low levels by absorbance, luminescence, or electrochemical means. In addition, small hydrophilic molecules upon prederivatization are often converted into larger more hydrophobic compounds, making reversed‐phase HPLC easier or even feasible. The HPLC section considers derivatization of drugs based on the following types: alkaloids, amines, antibiotics, barbiturates, carbonyl compounds and carboxylic acids, catecholamines, hydroxy compounds, steroids, and sulfur compounds. For the GC and HPLC sections, tables are included, giving the structures of the more important derivatizing agents, the analytes, and the corresponding reaction products. A brief rationale for derivatization chemistry with CE concludes this article. For CE, derivatization is often done to improve detectability as the path length for absorbance detection is very short and fluorescence can be effective using laser‐based systems.

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On-line electrochemical reagent production for fluorescence detection of phenothiazines in liquid chromatography

Cited by 27 publications

References 14 publications

Analysis of Phenothiazine and Its Derivatives Using LC/Electrochemistry/MS and LC/Electrochemistry/Fluorescence

Analysis of Phenothiazine and Its Derivatives Using LC/Electrochemistry/MS and LC/Electrochemistry/Fluorescence

Development and validation of a high-performance liquid chromatography method with post-column derivatization for the detection of aflatoxins in cereals and grains

Chemical Reagents and Derivatization Procedures in Drug Analysis

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