Avaluació del cabal per SPE amb òxid de titani com a adsorbent per a la preconcentració i determinació de Glifosat i àcid aminometilfosfònic en matrius aquoses

Abstract

Glyphosate (GLP) is a herbicide that is widely used today. This compound and its main

degradation product, aminomethylphosphonic acid (AMPA), are environmentally controversial

due to their persistence and possible toxicity. Their presence is mainly found in transgenic

crops. In the European context, due to the lack of results conclusively demonstrating the

carcinogenic effect of GLP, the European Commission renewed its authorization for use until

2033.

The aim of this work is to evaluate the use of titanium dioxide (TiO₂) as an adsorbent using the

solid-phase extraction (SPE) methodology for the detection of Glyphosate and its metabolite

AMPA in natural waters. The study is mainly focused on the effect of the loading flow rate on

adsorption.

SPE with titanium dioxide takes advantage of the high affinity of this oxide for phosphorous

compounds, making it a useful tool for concentrating analytes in samples containing interfering

substances, such as natural waters.

For the analysis, it is necessary to carry out the derivatization of the analytes with a

commercial derivatizing reagent (AccQ-Fluor™) to obtain fluorescent compounds that can be

detected by HPLC with a fluorescence detector. This significantly improves selectivity and

sensitivity compared to UV detection. Calibration curves have been prepared in the range of 1–

60 mg/L, showing linearity. Heteroscedasticity is observed in the responses, so a weighted least

squares (WLS) regression is required to improve the precision and accuracy of the results.

In the flow studies, it was found that flow rates <1 mL/min are necessary to achieve

quantitative adsorption and recoveries close to 100%. At higher flow rates, analyte retention

decreases significantly.

Various samples of natural waters have been analyzed. Except in one case, a sample from the

mining area of the Osar River, neither Glyphosate nor AMPA was detected. Therefore, the SPE

technique using TiO₂ as an adsorbent is promising for detecting both GLP and its metabolite

AMPA, although it would be necessary to increase the sample volume or use more sensitive

detectors, such as mass spectrometry, to achieve lower detection limits

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