What is Gravimetric Analysis?
Gravimetric analysis obtains information about a chemical or substance by separating the desired constituent from the sample to be analyzed and weighed. This is true as the gravimetric analysis principle is based on the estimation of how much mass percentage is present within an ion of an impure compound of known quantity in determining the mass of that same ion within a pure compound. To successfully determine mass, the ion must be completely isolated from the analyte.
The Steps of Gravimetric Analysis
Gravimetric analysis follows four basic steps. They are:
- Preparation of the solution containing the weight of the sample
- Seperation of the desired constituent using either an ashless filter paper or quantitative filter paper
- Weighing the isolated constituent
- Computation of the amount of the particular constituent within the sample from the observed weight of the isolated substance
There are four methods of gravimetric analysis
- Precipitation
- Volatilization
- Electro-analytical also called electrogravimetry
- Thermogravimetry
Precipitation Gravimetric Analysis
The most common form of gravimetric analysis, precipitation allows the constituent sought to be transformed into a substance that is not soluble within the solution. To isolate the constituent, a reagent is added to the solution that reacts with the analyte to create an insoluble compound without precipitating other solution based constituents. Precipitate is then obtained via either quantitative filter paper or ashless filter paper, washed free of the soluble impurities, and then dried or ignited to remove water and weighed.
Precipitation gravimetry is commonly applied to identify inorganic and organic analytes and instrument calibration. Common industries that apply precipitation gravimetry include pharmaceutical and food and beverage industries.
Volatilization Gravimetric Analysis
Volatilization gravimetric analysis is able to be either direct or indirect. For example, water that is eliminated within a quantitative manner from an inorganic substance through ignition is direct, while determining the amount of water by measuring water loss in mass during heating is indirect. While indirect methods of volatilization gravimetric analysis have a higher margin of error, it is commonly applied within the food industry to determine the moisture content of cereals.
Electrogravimetry
Electrogranimety, also called electo-analytical, is a method in which a metal is quantitatively electroplated to a (usually) platinum electrode. A current is then forced to flow between the platinum gauze cathode and platinum wire anode to completely deposit the metal.The cathode is then removed, dried, and weighed to determine the concentration of chemical analysis.
Thermogravimetry
Thermogravimetry is the least common form of gravimetric analysis. Within thermogravimetry, the mass of a sample is measured over a period of time as the temperature changes.
Vacuum Flasks for Gravimetric Analysis
Filtration of isolated constituents from the solution based constituents within the precipitation method of gravimetric analysis can be a time consuming endeavor. As such, it can be useful to employ vacuum flasks, which accelerate filtration with the application of an exhaust.
Ashless Filter Paper for Gravimetric Analysis
Ashless filter paper is a quantitative filter paper that is used to effectively filter precipitate from a solution by withstanding ignition to dry precipitate. As ashless filter paper does not create ash, the remaining dry precipitate sample can be collected to analyze mass.
Quantitative Filter Paper for Gravimetric Analysis
Quantitative filter paper is a cellulose based filter paper that is used for the ashing weighing post filtration as the ash weight of filter paper is set at a fixed value. Quantitative filters have a high wet strength and are able to withstand pressure and vacuum filtrations allowing them to be ideal for precipitation gravimetric analysis applications.
How to Determine The Correct Filter for Your Gravimetric Analysis Needs
When it comes to selecting a quantitative or ashless filter for any gravimetric analysis there is a prescribed process involved which requires four simple steps. These steps can be done with a filter media selector and include:
- Deciding on the necessity of prefiltration for the application.
- Choosing a membrane filtration material based on qualities such as aqueous, non-polar, and protein.
- Selecting a diameter typically of <10ml, <100ml, or <250ml to determine the mm diameter of the filter.
- Ensuring the pore size, based on micron size of the column of >3um or <3um.
As with anything else, it is of utmost importance to ensure the filter’s chemical compatibility with your application needs. Consider this chemical compatibility guide to determine what chemicals your filter is compatible with.
Tisch Scientific Supports Gravimetric Analysis Filtration and Vacuum Flask Needs
Regardless of the type of gravimetric analysis you are looking to complete, Tisch Scientific has a wide range of applicable ashless filter paper, quantitative filter paper, vacuum flasks, and other lab equipment to allow for proper filtration and analysis.