Rapid and Simplified Determination of Amphetamine-Type Stimulants Using One-Pot Synthesized Magnetic Adsorbents with Built-In pH Regulation Coupled with Liquid Chromatography-Tandem Mass Spectrometry

Abstract

Background: Amphetamine-type stimulants (ATS) in water pose significant public health and ecological risks, necessitating reliable and efficient detection methods. Current approaches often involve time-consuming pH adjustments and post-processing steps, limiting their practicality for high-throughput analysis. This study aimed to develop a streamlined method integrating pH regulation and adsorption into a single material to simplify sample preparation and enhance analytical efficiency.

Methods: A novel Fe₃O₄/MWCNTs-OH/CaO composite adsorbent was synthesized via a one-pot grinding method, embedding pH adjustment and adsorption functionalities within a single material. This innovation enabled magnetic solid-phase extraction (MSPE) without pre-adjusting sample pH or post-desorption steps. The method was coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS) for ATS detection. Optimization included evaluating adsorption/desorption conditions and validating performance in real water matrices.

Results: The method demonstrated exceptional linearity (R² > 0.98), low detection limits (0.020-0.060 ng/mL), and high accuracy with relative recoveries of 92.8-104.8%. Precision was robust, with intra-/inter-day relative standard deviations (RSDs) below 11.6%. Single-blind experiments confirmed practical applicability, yielding consistent recoveries (relative errors: 1-8%) for ATS-spiked samples at 0.8 and 8 ng/mL. Compared to existing techniques, the approach reduced processing time to ~5 min by eliminating external pH adjustments and post-concentration steps.

Conclusions: This work presents a rapid, reliable, and user-friendly method for ATS detection in complex environmental matrices. The integration of pH regulation and adsorption into a single adsorbent significantly simplifies workflows while maintaining high sensitivity and precision. The technique holds promise for large-scale environmental monitoring and forensic toxicology, offering a practical solution for high-throughput analysis of emerging contaminants.

Keywords: amphetamine-type stimulants (ATSs); built-in pH regulation; liquid chromatography–tandem mass spectrometry (LC-MS/MS); magnetic adsorbent; magnetic solid-phase extraction (MSPE); one-pot grinding.

Figure 1

The structures of eight amphetamine-type stimulants (pKa values were predicted using ChemDraw 20.0.0.41).

Figure 2

A schematic illustration of (A) the preparation of Fe₃O₄/MWCNTs-OH/CaO composite and (B) the MSPE procedure with integrated pH adjustment for analyte extraction from water samples.

Figure 3

The optimization of the crucial parameters of the proposed method: (A) the mass of CaO in the composite; (B) the mass of Fe₃O₄ and MWCNT-OH in the composite; (C) the acid concentration in the desorption solvent; and (D) the volume of the desorption solvent.

Figure 4

MRM chromatograms of (A) ATS standard solution (1 ng/mL) and (B) ATS standard solution (1 ng/mL) processed using the proposed sample preparation method.