研究目的
To develop an analytical method for determining thiacloprid, thiamethoxam, and imidacloprid in tea samples based on quenching of terbium luminescence, as an alternative to chromatographic techniques.
研究成果
The proposed time-resolved luminescence method is suitable for quantifying thiacloprid, thiamethoxam, and imidacloprid in tea samples at levels below maximum residue limits, with accuracy and precision comparable to HPLC-MS. It offers a simple and inexpensive screening alternative, though confirmation is needed for specific identification.
研究不足
The method does not discriminate between different neonicotinoids; positive results require confirmation by HPLC-MS. Potential matrix effects in some samples necessitate the use of standard addition method.
1:Experimental Design and Method Selection:
The method is based on quenching of terbium luminescence by neonicotinoids. Time-resolved luminescence is used to avoid interferences.
2:Sample Selection and Data Sources:
Tea samples (green tea, black tea, chamomile, peppermint) were selected. Samples were spiked with known concentrations of analytes for recovery experiments.
3:List of Experimental Equipment and Materials:
Equipment includes a Cary-Eclipse luminescence spectrometer, ultrasonic bath, pH meter, centrifuge, rotary evaporator, and HPLC system. Materials include terbium nitrate, neonicotinoid standards, buffers, and SPE cartridges.
4:Experimental Procedures and Operational Workflow:
Sample preparation involved QuEChERS extraction and SPE clean-up. Luminescence measurements were performed with optimized parameters (excitation 256 nm, emission 545 nm, delay time
5:1 ms, gate time 3 ms). Calibration graphs were constructed for each analyte. Data Analysis Methods:
Data were analyzed using the Stern-Volmer equation for quenching mechanism. Statistical analysis included calculation of detection limits, recovery yields, and comparison with HPLC-MS reference method using F-test and t-test.
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HPLC system
Agilent Series 1100
Agilent Technologies
Reference method for comparison
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mass spectrometer
Esquire 6000
Bruker Daltonics
Detection for HPLC reference method
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Cary-Eclipse luminescence spectrometer
Cary-Eclipse
Varian Inc.
Recording luminescence measurements
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quartz cuvette
Hellma 1010-QS
Hellma
Holding samples for luminescence measurements
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ultrasonic bath
Sonorex Digital 10P
Bandelin Electronic
Used in sample preparation
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pH meter
GLP21
Crison Instruments
Measuring pH of solutions
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centrifuge
Mixtasel-BL
Selecta
Centrifuging samples
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rotary evaporator
Heidolf
Evaporating solvents
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SPE cartridges
Discovery DSC-18
Supelco (Sigma-Aldrich)
Solid-phase extraction for sample clean-up
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water purification system
Milli-Q Waters
Millipore
Producing ultrapure water
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