Ultrasonic spectrometry range

Determining the droplet size distribution of an emulsion by ultrasonic spectrometry involves two steps. First, the ultrasonic velocity and (or) attenuation coefficient of the emulsion is measured as a function of the frequency — preferably over as wide a range as possible. Second, the experimental measurements are compared with theoretical predictions of the ultrasonic properties of the emulsion, and the droplet size distribution providing the best fit between theory and experiment is determined. 

CSIRO Minerals has developed a particle size analyzer (UltraPS) based on ultrasonic attenuation and velocity spectrometry for particle size determination [269]. A gamma-ray transmission gauge corrects for variations in the density of the slurry. UltraPS is applicable to the measurement of particles in the size range 0.1 to 1000 pm in highly concentrated slurries without dilution. The method involves making measurements of the transit time (and hence velocity) and amplitude (attenuation) of pulsed multiple frequency ultrasonic waves that have passed through a concentrated slurry. From the measured ultrasonic velocity and attenuation particle size can be inferred either by using mathematical inversion techniques to provide a full size distribution or by correlation of the data with particle size cut points determined by laboratory analyses to provide a calibration equation. 

An important work on the LC-APPI-MS/MS field was developed for the analysis of 12 PAHs in sediment samples (Moriwaki et al. 2004). In this context APPI was performed in positive mode aiming to overcome the low sensitivity of poor fluorescence PAHs. Extraction of PAHs from sediments was conducted with ultrasonic agitation and the mixture was purified on a silica cartridge. PAHs were eluted with a mixture of hexane toluene (9 1) and separated on a reversed phase ODS column with a runtime of 20 min. From mass spectrometry point of view the positive molecular ions were observed as the main peaks for all PAHs. Limits of determination ranged from 6 to 91 ng/g thus they were comparable with LODs presented in HPLC-FLD analyses. The method had also acceptable recovery values (90-116%). 

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