Ultrasonic assisted magnetic solid phase extraction of ultra-trace mercury with ionic liquid functionalized materials.

Due to the agglomeration between particles, the inherent adsorption characteristics of magnetic powder materials are usually difficult to fully display. Taking ionic liquid functional materials as an example, the enrichment behavior of these adsorbents for trace mercury (Hg2+) in ultrasonic (US) assisted dispersion mode was systematically studied. The dissociation of protonic ionic liquids (IL) occur in the process of dispersion and the strong electrostatic attraction can improve the diffusion and adhesion of mercury on the adsorbent surface. Spectral measurement data showed that with the help of US, the more uniform dispersion of magnetic materials accelerated the adsorption of trace Hg2+. Ultrasonic intrinsic parameters such as frequency, power and radiation duration significantly affect the dispersion and apparent adsorption properties of magnetic functional materials. In the range of experimental parameters, the dye/paper image experimental results documents that there is a positive correlation between cavitation effect and ultrasonic frequency/power. The enrichment degree of fixed adsorbate (0.1 µg L-1) under high frequency (59 kHz) or high-power input (100%) is 1-2 times higher than that under low frequency (40 kHz) or low power (60%) input. This is a valuable conclusion for the subsequent study of US dispersion of magnetic and even non-magnetic powder materials. In addition, the in-situ desorption and accurate measurement of adsorbed mercury were realized by combining slurry vapor generation atomic fluorescence spectroscopy (SVG-AFS). The constructed US assisted magnetic solid phase extraction (US-MSPE) method has the characteristics of low detection limit (0.36 ng L-1), high recovery (>90%), sustainable utilization (>3) and reasonable measurement deviation (<5%), which can meet the requirements of ultra-trace Hg2+ (0.01-1.0 µg L-1).

Ultrasound-assisted dispersive solid phase extraction for promoting enrichment of ng L-1 level Hg2+ on ionic liquid coated magnetic materials.

Herein, we investigated the enrichment behavior of inorganic mercury (Hg2+) on magnetic adsorbent with different ultrasound (US) energy field input. The enrichment rate of 0.10 µg L-1 mercury is increased by 4.5 times after US instead of stirring as dispersion mode. The input of higher frequency and power ultrasound can accelerate the enrichment of magnetic ionic liquid adsorbent and reduce the Hg2+ residue, importantly, which has not been reported. The positive correlation between cavitation effect and acoustic frequency and power in imaging experiments documents that US parameters are the key factors affecting the magnetic solid phase extraction. In addition, in-situ desorption and detection of adsorbate and recovery of adsorbent can be realized by slurry vapor generation (SVG) technology. The recovery of Hg2+ in four cycles is more than 90%, which indicates that the structure and properties of the material are not affected by the application of US. Hence, the degradation of adsorption properties caused by agglomeration of magnetic materials can be improved by introducing dispersion methods such as US. At the same time, 95% enrichment efficiency and 0.01-1.0 µg L-1 linear calibration range corresponding to 150 mL sample documents that magnetic ionic liquid adsorbent combined with US and sensitive spectral detector can meet the needs of ng L-1 level Hg2+ analysis in natural water samples.

Ultrasound enhanced solid-phase extraction of ultra-trace arsenic on Fe3O4@AuNPs magnetic particles.

Using ultrasound (US) to reduce the agglomeration of magnetic materials has attracted many researchers' attention in the field of magnetic solid phase extraction (MSPE). This paper showed that even the simple magnetic material (Fe3O4@AuNPs) can stimulate excellent arsenic (As) enrichment performance with the assistance of US. Compared with stirring dispersion, the extraction efficiencies of Fe3O4@AuNPs for 0.2 µg L-1 As(III) and As(V) improved by a factor of about 6.2- and 5.7-times with ultrasonic agitation, respectively. Importantly, when the ultrasonic frequency and power are varied within a certain range, the extraction efficiency was increased by about 50% and 130%, respectively. This effect of ultrasonic frequency and power on the enrichment of arsenic by magnetic materials has never been reported. The number, dispersion uniformity and energy released by the bursting of cavitation bubbles under different conditions are considered to be the main reasons for the above phenomena. Additionally, the As(III) or As(V) can be converted into a gaseous product by in-situ slurry chemical hydride generation (SCHG) technology, and the material adsorbed by the material can be effectively removed, thereby ensuring that the complex is repeated at least 5 times or more. Under the optimized conditions, the whole enrichment process can be shortened from ~1 h to several minutes in the presence of US. At the same time, the linear calibration range was 0.01-3.0 µg L-1 documenting that this US-assisted dispersive MSPE method coupled with a sensitive spectral detector (e.g. atomic fluorescence spectrometer, AFS) is suitable for analysis of inorganic As in natural water samples. The content of arsenic in five kinds of natural water samples ranged from 34 ng L-1 to 2.3 µg L-1.