Quantitative analysis (chemistry)
Quantitative analysis in chemistry is a method used by scientists to determine the specific amounts of various substances within a sample. This type of analysis is essential for applications ranging from testing dissolved solids in drinking water to analyzing minerals in blood samples. Unlike qualitative analysis, which identifies the types of molecules present, quantitative analysis focuses on measuring the precise quantities of those molecules. Common methods employed in quantitative analysis include gravimetric analysis, which involves isolating a material through precipitation reactions, and titrimetry (or titration), where a reagent is added to a solution to measure the amount of a substance based on the reaction produced.
Other valuable techniques include chromatography, which separates mixed materials for analysis, and spectroscopy, which examines light spectra to determine material composition. The precision of quantitative analysis is significantly enhanced by the use of sensitive instruments like analytical balances, capable of measuring extremely small quantities. Factors influencing the choice of analysis methods include the type of material, available sample size, required accuracy, and time constraints. Overall, quantitative analysis is a fundamental aspect of analytical chemistry that provides critical data for various scientific and industrial applications.
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Quantitative analysis (chemistry)
Quantitative analysis is a type of chemical analysis that scientists use to determine the specific amounts of certain materials within a particular substance. For example, scientists may use quantitative analysis to test the amount of dissolved solids in drinking water or to determine the amounts of various minerals in a patient's blood. Quantitative chemical analysis is accomplished by conducting chemical reactions and measuring specific outcomes. Some methods scientists use to conduct quantitative chemical analysis are gravimetric analysis and titrimetry.
Background
Chemical analysis is the study of the makeup of different substances. Analytical chemistry is a branch of chemistry devoted to chemical analysis. The two types of chemical analysis are qualitative and quantitative. Qualitative analysis tests to identify the types of molecules, atoms, and ions present in particular materials. Quantitative analysis seeks to find the specific quantities of molecules, atoms, and ions that are in particular materials. Quantitative analysis is more precise than qualitative analysis. Qualitative and quantitative analyses are used for different reasons. Qualitative analysis often costs less and takes less time than quantitative analysis. Therefore, scientists tend to use quantitative analysis only when very precise measurements must be known. They are more likely to choose qualitative analysis if they need to save money or time.
Overview
When performing a quantitative analysis, scientists follow a number of steps. First, they determine the problem they want to solve. For example, they may want to find how much of a certain molecule is present in a solution. At this stage, scientists have to consider who will use the data, how accurate the data must be, and how much money they can spend on their analysis. These factors will influence the methods used to conduct the analysis. Other factors that influence the choice include the type of material being tested, the amount of material available for testing, the amount of time available to complete the tests, the standard methods used in the field, and so on.
After scientists choose the testing method, they will collect samples and prepare them for analysis. Scientists may have to change the sample size, change the solution conditions, or conduct chemical separations before they can test certain samples. Then, researchers have to perform the actual test or measurement. This may involve adding a reagent to a solution to see what chemical reaction occurs or separating elements using chromatography and measuring each part. Scientists sometimes try to replicate their tests and analyses to ensure their results are correct. Finally, researchers observe their tests, collect data, and analyze and report their results.
Many methods can be used to conduct quantitative analysis. People choose different methods depending on the type of material being tested, the amount of material available for testing, the desired effect of the testing, and so on. Two of the most important quantitative analysis methods are gravimetric analysis and titrimetry. When using gravimetric analysis, a researcher will isolate a particular material in a substance, most often through a precipitation chemical reaction. A precipitation reaction is a chemical reaction in which two reactants are mixed together and produce two new products. One of the products is a crystalline solid, and the other is a solution. To finish the gravimetric process, the scientist performs the chemical reaction, collects the solid material, dries the solid material, and weighs it. This is one of the most basic tests for quantitative analysis, as it is fairly simple and fairly inexpensive. However, this test is not appropriate for every situation or for every material that needs to be tested.
Titrimetry is another type of quantitative analysis. Titrimetry, often called titration, is a process in which a reagent called a titrant is mixed with a solution. The reagent and the solution will form a chemical reaction. For example, a solution contains an unknown amount of a particular substance. To conduct a titration, a scientist will add a known amount of the titrant to the solution over time. The amount of titrant that is added to the solution is precisely measured. Once the chemical reaction occurs, the scientist conducting the experiment can determine the amount of a particular material in the solution by understanding and analyzing how much titrant was required to produce the chemical reaction.
Scientists may use many other methods to complete a quantitative analysis. Chromatography is a separation method that divides different materials that are mixed together. Chromatography is a valuable quantitative analysis tool because it can be used to separate and test small samples, and it gives very specific results. In addition, it usually can be completed quickly and cheaply. Chromatography experiments and results can be replicated easily by different scientists as long as they follow specific methods. Spectroscopy is another important tool used in quantitative analysis. Spectroscopy separates the spectrum of light that shines through objects. By observing the spectrum of light, scientists can determine the composition of the material. Many types of chromatography and spectroscopy exist.
One of the most common tools used in quantitative analysis is the analytical balance. An analytical balance is extremely sensitive and precise. It can measure the smallest quantities so that scientists can accurately identify the amount of particular molecules, atoms, or ions in a material. Analytical balances can generally measure up to 0.0001 grams (1/10,000 of a gram). Even airflow can affect analytical balances, so they have draft shields to protect them from being affected by the air. Because these balances are so sensitive, it is important for people to keep them clean and to store them in a safe, clean space.
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