Ultrasonic Dissolving of Solids in Liquids

The preparation of solutions is an important step for lab samples as well as for industrial production. In general, lab samples must be liquified before analysis. Ultrasonic homogenization and dissolving is a quick and reliable means to prepare samples of all sizes. In industrial production, the preparation of homogeneous and well-dissolved solutions is often a crucial factor to guarantee steady product characteristics and a consistent quality. Ultrasonic dissolvers are available as compact lab devices and as full-commercial industrial dissolvers.

Ultrasonic Dissolvers: Use and Applications

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 you are interested in the preparation of heterogeneous suspensions, click here for: ultrasonic emulsification and ultrasonic 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.
Ultrasonication is often used to promote an effective and fast dissolution of samples. The ultrasonically assisted dissolving is based on the mechanical agitation of the cavitational effects caused by the input of ultrasound waves into liquids. The input of ultrasound energy facilitates and accelerates the sample pretreatment such as dissolving and leaching prior to analysis.
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.

Microscopic images of meloxicam suspension:
Left: untreated meloxicam suspension; Right: Meloxicam nanosuspension obtained by ultrasonication with the UP100H for 45 minutes at 100% amplitude and cycle 1.
(study and picture: ©Iurian et al., 2015)

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 guaranteed without the risk of cross-contamination and sample falsification or sample loss.
Read more about the All-in-One Ultrasonic Sample Prep Unit SonoStep!

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 reactions

Ultrasonic Processors for Dissolving Applications at Any Scale

Hielscher Ultrasonics offers the ideal solution for your dissolving and wetting application. Wether you need to prepare analytical samples in the laboratory or produce large volumes of solutions or brines in continuous flow-through mode – Hielscher Ultrasonics has the ideal ultrasonic dissolver for your process!
With ultrasonicators at any power rating and for batch as well as inline processing, we will recommend you the most suitable ultrasonicator for your processing goals!
The table below gives you an indication of the approximate processing capacity of our ultrasonicators: