Rapid Total Solids Analysis for Household Cleaning Products

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Most household cleaning products are comprised of a mixture of high-cost active ingredients and low-cost filler, such as water. Accurately verifying the total solids content is the key to minimizing material costs per batch, which should be performed as quickly as possible to expedite batch release and minimize production down time. Because of the wide variety of volatile components present in a given sample, solids testing has traditionally been performed in an air or vacuum oven, which is effective at drying all sample types, but takes hours to complete. Infrared-only analyzers reduce the time it takes to analyze products, compared to air oven methods, but can still take up to 25 minutes to completely dry liquid detergents and softeners, which tend to re-condense inside the drying cavity, due to a lack of active ventilation. Microwave-only analyzers can perform a total solids test in minutes, but the presence of glycerin tends to result in sample scorching. Furthermore, microwave-based analyzers are ineffective at completely drying certain products that contain non-aqueous volatile components which are not excited by microwave energy. Indirect techniques, such as NIR and FT-IR have been introduced to perform rapid analysis, but require costly calibrations and are sensitive to slight variations in color and formulation.


The SMART 6 total solids analyzer is uniquely designed to handle a wide variety of household goods and their ingredients, whether they are water-based, contain a mixture of volatile components, or are a high-solids paste. The SMART 6 utilizes dual-frequency energy, specifically microwave and infrared, to rapidly analyze solids content. Low frequency microwaves penetrate the entire sample to rapidly remove bound moisture through dipole rotation, while high-frequency infrared energy evenly heats the surface through molecular vibration. The two energy sources work in unison, providing benefits over microwave-only and infrared-only analyzers, with results in less than 4 minutes. This study demonstrates that the SMART 6 can rapidly analyze a wide range of household goods for total solids with an average difference of less than 0.08 % compared to reference methods.