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Traditional bistable stochastic resonance has been demonstrated as an effective tool to detect the weak signal in a strong noise background. To achieve a better signal-to-noise ratio for the output signal, a coupled stochastic resonance was developed by nonlinearly coupling two double-well potential systems. The response characteristics of coupled stochastic resonance subjected to analytical signals have been investigated and compared with those of bistable stochastic resonance. The improvement of chromatographic determination with the proposed coupled stochastic resonance was validated by both simulated signals and chromatographic signals. The weak signals from both simulated data and plasma samples with different concentrations were all amplified significantly and the quantitative relationship between different concentrations and responses was kept well. It is reasonable to believe that coupled stochastic resonance could play an important role in applications where quantitative determination of low-concentration samples is crucial. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Ultrasound-assisted emulsification-microextraction coupled to HPLC was applied to the determination of propoxur in environmental and beverage samples. Carbon tetrachloride (the extraction solvent) is added to the aqueous sample, and the liquids are sonificated at 60 °C, upon which an emulsion is formed. This is followed by centrifugation the lower phase being analyzed by HPLC. The extraction solvent, its volume, extraction time, temperature and salt concentration were optimized. Linear range (0.01–10 µg mL-1), correlation coefficient (0.9965), detection limit (1 ng mL-1 at a SNR of 3), and precision (4.5% RSD, n = 5) were determined. The technique was applied to the determination of propoxur in environmental and beverage samples and no target analyte was found in these samples. Therefore, samples were spiked and recoveries of 93–106% and RSDs of 1.5–6.2% were obtained. [ABSTRACT FROM AUTHOR]