Optimization of ultrasound-assisted dispersive solid-phase microextraction based on nanoparticles followed by spectrophotometry for the simultaneous determination of dyes using experimental design

• A fast UA-DSPME was optimized for AO and MG determination in water sample.
• Response surface methodology was used to optimize the process variables.
• The ultrasonic showed advantages compared with magnetic stirrer for this application.
• The novel method exhibits low detection limits and good recoveries for two compounds.

A simple, low cost and ultrasensitive method for the simultaneous preconcentration and determination of trace amount of auramine-O and malachite green in aqueous media following accumulation on novel and lower toxicity nanomaterials by ultrasound-assisted dispersive solid phase micro-extraction (UA-DSPME) procedure combined with spectrophotometric has been described. The Mn doped ZnS nanoparticles loaded on activated carbon were characterized by Field emission scanning electron microscopy (FE-SEM), particle size distribution, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) analyses and subsequently were used as green and efficient material for dyes accumulation. Contribution of experimental variables such as ultrasonic time, ultrasonic temperature, adsorbent mass, vortex time, ionic strength, pH and elution volume were optimized through experimental design, and while the preconcentrated analytes were efficiently eluted by acetone. Preliminary Plackett–Burman design was applied for selection of most significant factors and giving useful information about their main and interaction part of significant variables like ultrasonic time, adsorbent mass, elution volume and pH were obtained by central composite design combined with response surface analysis and optimum experimental conditions was set at pH of 8.0, 1.2 mg of adsorbent, 150 μL eluent and 3.7 min sonication. Under optimized conditions, the average recoveries (five replicates) for two dyes (spiked at 500.0 ng mL−1) changes in the range of 92.80–97.70% with acceptable RSD% less than 4.0% over a linear range of 3.0–5000.0 ng mL−1 for the AO and MG in water samples with regression coefficients (R2) of 0.9975 and 0.9977, respectively. Acceptable limits of detection of 0.91 and 0.61 ng mL−1 for AO and MG, respectively and high accuracy and repeatability are unique advantages of present method to improve the figures of merit for their accurate determination at trace level in complicated materials.

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