Rapid and sensitive determination of phosphorus-containing amino acid herbicides in soil samples by capillary zone electrophoresis with diode laser-induced fluorescence detection

Abstract

A straightforward and sensitive method has been developed for the analysis of phosphorus-containing amino acid herbicides (glufosinate and aminomethylphosphonic acid, the major metabolite of glyphosate) in soil samples. For this purpose, the analytical features of two indocyanine fluorescent dyes, sulfoindocyanine succinimidyl ester (Cy5) and 1-ethyl-1-[5-(N-succinimidyl-oxycarbonyl)pentyl]-3,3,3,3-tetramethyl-indodicarbocyanine chloride, as labeling reagents for the determination of these herbicides by CZE with diode LIF detection were investigated. Practical aspects related to the labeling chemistry and CZE separation showed that the two probes behave similarly, Cy5 being the best choice for the determination of these herbicides on account of its higher sensitivity. The optimum procedure includes a derivatization step of the pesticides at 25 degrees C for 30 min and direct injection to CZE analysis, which is conducted within about 14 min using ACN in the running buffer. The lowest detectable analyte concentration ranged from 0.025 to 0.18 microg/L with a precision of 3.6-5.4%. These results indicate that indocyanine fluorescence dyes are useful as rapid and sensitive labels for the determination of these herbicides when compared with typical fluorescein dyes such as FITC and 5-(4,6-dichloro-s-triazin-2-ylamino) fluorescein, because they provide faster labeling reactions even at room temperature and the excess of reagent practically does not interfere the determination. Finally, the Cy5 method was successfully applied to soil samples without a preliminary clean-up procedure, and the herbicides were measured without any interference from coexisting substances. The recoveries of these compounds in these samples at fortification levels of 100-500 ng/g were 90-93%.

Determination of Herbicides and Its Metabolite in Soil and Water Samples by Capillary Electrophoresis-laser Induced Fluorescence Detection Using Microwave-assisted Derivatization

“…Existing analytical methods for the detection of these herbicides in waters and other matrices like soils are mainly based on chromatographic techniques, including liquid chromatography (LC) [7][8][9] and capillary electrophoresis (CE), 10 equipped with different detection devices such as ultraviolet (UV), 11 mass spectrometry (MS), 12,13 and fluorescence detection. [14][15] During the last decade, MS detection with LC separation (LC-MS) has been the technique of choice for the analysis of these herbicides because it provides higher sensitivity and capability to differentiate overlapping peaks with distinct mass-to-charge ratios. 12,13 However, the instrumentation demands of these methods are substantial.…”

“…10,15 The analytical challenge posed by these herbicides is that they have neither chromophores nor fluorophores groups, preventing their detection by ultraviolet-visible (UV-vis) absorbance or fluorescence. Because of that, derivatization reactions are needed and the most commonly used are 9-fluorenyl methyl chloro formate (FMOC-Cl), [7][8][9] 4-chloro-3,5-dinitrobenzotrifluoride (CNBF), 11 4-fluoro-7-nitro-2,1,3-benzoxadiazole-(NBD-F), 16 p-toluenesulfonyl chloride (TsCl),17 3,6-dimethoxy-9-phenyl-9H-carbazole-1-sulfonyl chloride (DPCS-Cl), 18 sulfoindocyanine succinimidyl ester (Cy5), 14 FITC and DTAF are both fluorescein-based amino-reactive derivatives, which have relatively high absorptivity and excellent fluorescence quantum yield. What is more attractive is that they have a fluorophore compatible with the LIF detection system (488 or 473 nm).…”

Analysis of Phosphorus-containing Amino Acid-type Herbicides by Capillary Electrophoresis/Mass Spectrometry Using a Chemically Modified Capillary Having Amino Groups

“…Simplification of sample pretreatment shortens total analysis time and saves labor. CE methods coupled with UV-absorption 10,11) or fluorescence 12,13) detection have been used to detect those compounds. Recently we have reported a CE method for GLYP analysis using a simple online copper(II)-GLYP derivatization, and successfully detected GLYP in tea beverage samples.…”

A Fast and Simple Analysis of Glyphosate in Tea Beverages by Capillary Electrophoresis with On-Line Copper(II)-Glyphosate Complex Formation

“…Using gas chromatography analysis, derivatization of glyphosate is required to lower its polarity and enhance its volatility. 1,2) High performance liquid chromatographic (HPLC) [3][4][5] and capillary electrophoretic (CE) 6,7) methods also usually require derivatization of glyphosate to detect it by UV-absorption or fluorescence, because glyphosate possesses no chromophore. These analytic methods with derivatization can determine low levels of glyphosate, but the derivatization method is tedious and time-consuming.…”