Ultrasonic Dissolving of Solids in Liquids
Ultrasonics is a well-known, reliable tool for sample preparation in the lab. Usual applications include homogenization, emulsification, dispersion, extraction, degassing, and sonochemical treatments.
For measurements by analytical instruments (e.g. HPLC, atomic spectrometer, etc.), generally most samples have to be liquefied. This means that the sample either must be be in the homogeneous state of a solution or must be transferred into the a colloid, suspension, dispersion or emulsion if the mixture is of heterogeneous nature. Powerful ultrasonication is an very effective tool to prepare both homogenous and heterogeneous mixtures. If your interested in the preparation of heterogeneous suspensions, click here for ultrasonically assisted emulsification and dispersing!
For the generation of homogeneous mixtures by ultrasonic dissolving, please continue reading below!
Ultrasonic Cavitation for Dissolving
If the sample is soluble, the solute (such as succralose, salts, e.g. in powder or tablet form) can be dissolved in a solvent (e.g. water, aqueous solvents, organic solvents etc.) resulting in a homogeneous mixture, composed of only one phase. The dissolving process can be carried out by manual or mechanical stirring, which is time-consuming and inefficient. Related problems are sample losses due to manipulation or lacking reproducibility by random errors and uneven mixing.
By the ultrasonically assisted preparation of a solution, it becomes possible to dissolve solutes in high concentration and to create efficiently and fast a concentrated or saturated (and oversaturated) solution.
When high power/ low frequency ultrasound is introduces into a liquid medium, the resulting acoustic cavitation creates unique conditions. Ultrasonication has enhanced liquid-liquid and solid-liquid sample pretreatments (e.g. digestion, solubilization and extraction), which are typically applied prior to analytical detection and measurement.
The dissolution rate quantifies the speed of the dissolving process. The dissolution rate is influenced by various factors:
- material: solvent and solute
- temperature + pressure
- degree of (under-)saturation
- efficiency and impact of dissolving and blending
- interphase surface area
- presence of inhibitors (e.g. substances deposited on the particles/ blocking on the phase boundary)
To accelerate the solvation process and the dissolution rate, powerful homogenizers that provide sufficient mechanical impact are required. The cavitational dissolving and blending power of ultrasonic homogenizers are well-known and thereby a common and reliable tool for the sample preparation in laboratories.
Ultrasonic Dissolving of Lab Samples
Ultrasonically assisted dissolution for sample preparation is used in laboratories before analytical measurements.
List of analytic instruments that require (often) liquefied samples:
- HPLC – High Performance Liquid Chromatography
- FTIR – Fourier Transform Infrared Spectroscopy
- GC – Gas Chromatography
- Atomic spectroscopy
- ATR – Attenuated Total Reflection
- Laser Diffraction Particle Sizing
- Dynamic Light Scattering
With the ultrasonic sample preparation device SonoStep, pre-analysis sample treatment can be operated completely inline: The ultrasonic sample preparation device features an integrated stirrer and pump, so that the samples run steady and continuously through a closed system. Thereby, an even and reliable sonication is guarantueed without the risk of cross-contamination and sample falsification or sample loss.
Ultrasonic Dissolving for Industrial Production
In industrial production lines, high power ultrasound is integrated to dissolve and homogenize solid-liquid mixtures to form an even and stable product.
Find below some examples for different industrial branches:
Pharmaceutical industry: dissolving of drug components, e.g. salts, polymers
Food and beverage industry: dissolving of ingredients, e.g. sugar, salt, syrup, condiments
Paints & Coatings: dissolving of polymers
Chemistry: preparation of a supersaturated solution before precipitation
- Welna, Maja; Szymczycha-Madeja, Anna; Pohl, Pawel: Quality of the Trace Element Analysis: Sample Preparation Steps. In: InTechOpen.
- Castro, Luque de; Capote, Priego F. (ed.) (2007): Analytical Applications of Ultrasound. Elservier Science, 2007.