Gravimetric Test for Analytes Determination

Gravimetric test is a classic wet chemical method used to measure the weight or concentration of a solid in a liquid. As a set of methods in analytical chemistry, this weight analysis method quantifies the analyte based on the mass of the solid. A simple example is the measurement of solids suspended in a water sample by filtering a known volume of water and weighing the collected solids. Gravimetric testing analysis uses changes in weight to provide information. Some methods, such as dry weight loss, may involve simple weighing, heating and cooling, while other methods, such as chloride, may involve the reaction of other reagents followed by filtration and weighing. BOC Sciences is capable of providing wet chemistry gravimetric techniques to provide better performance and a more cost effective solution. Our cGMP compliant laboratory is equipped with state of the art instrumentation to ensure rapid and accurate product characterization and method development.

Introduction of Gravimetric Analysis

Gravimetric analysis is a technique in which the amount of an analyte can be determined by measuring its mass. The mass of an analyte is determined by comparing the masses of two compounds containing the analyte. It involves separating the ions in the solution by a precipitation reaction, filtering, washing the precipitate free of contaminants, converting the precipitate into a product of known composition, and then weighing the precipitate and determining the difference in mass.

Our Workflow

• First, a known amount of the sample is weighed and dissolved
• Then, the sample is treated by chemical or physical methods (appropriate reagents) to precipitate the compound
• Next, the precipitate is collected by filtration, washed, dried to remove traces of water from the solution, and weighed
• Finally, based on the mass of the precipitate and its chemical composition, the amount of the components in the original sample is accurately calculated

What We Offer

At BOC Sciences, we have introduced gravimetry methods for the quantitative determination of an analyte based on its mass. Examples include:

Loss on drying (LoD)

• LoD is a frequently applied method that can be used to estimate water content greater than 5% when it is assumed that the loss in weight is water.

Loss on Ignition (LoI)

• Lol is used for most organic (carbon-based) materials that will burn when heated to a sufficient temperature leaving behind the mineral matter in the formulation. The residue is considered to be representative of the mineral content.

Precipitation

• Many other substances, including metals, such as calcium, iron and nickel, and anions, such as sulfates, phosphates and oxalates, can be estimated by gravimetry.

Figure 2. Gravimetric test results on seawater. (Cavasin, M.; et al. 2018)

Advantages of Our Gravimetric Analysis

• Precise and accurate
• Possible sources of error can be easily checked, as the filtrate can be tested for precipitation integrity and the precipitate can be carefully checked for the presence of impurities
• Low cost: only relatively inexpensive instruments are used for the determination
• Available for the determination of the atomic mass of many elements
• Very small instrument error margin and no need for a series of standards to calculate the unknowns