Standard Addition

Definition

Standard addition is an analytical technique used in quantitative chemical analysis to determine the concentration of an analyte in a sample by adding a known amount of the analyte to the sample and measuring the resulting change in the analytical signal. This method helps overcome matrix effects and improve the accuracy of the analysis.

5 Must Know Facts For Your Next Test

1. Standard addition is particularly useful when the sample matrix significantly affects the analytical signal, as it helps to compensate for these matrix effects.
2. The technique involves adding known amounts of the analyte to the sample and measuring the change in the analytical signal, which is then used to determine the original concentration of the analyte in the sample.
3. Standard addition is often used in conjunction with techniques such as atomic absorption spectroscopy, inductively coupled plasma, and electrochemical methods.
4. The method requires at least two measurements: one for the original sample and one for the sample with the added standard. Additional standard additions may be made to improve the accuracy of the analysis.
5. The concentration of the analyte in the original sample is determined by extrapolating the calibration curve obtained from the standard additions to the point where the analytical signal is zero.

Review Questions

• Explain the purpose of using the standard addition method in quantitative chemical analysis.
  • The purpose of using the standard addition method in quantitative chemical analysis is to overcome matrix effects and improve the accuracy of the analysis. Matrix effects can influence the analytical signal, leading to inaccurate results. By adding a known amount of the analyte to the sample and measuring the change in the analytical signal, the standard addition method allows for the determination of the original concentration of the analyte in the sample, even in the presence of matrix interferences.
• Describe the steps involved in the standard addition method and how the original analyte concentration is determined.
  • The standard addition method involves the following steps: 1) Measure the analytical signal of the original sample. 2) Add a known amount of the analyte standard to the sample and measure the new analytical signal. 3) Repeat step 2 with additional standard additions. 4) Plot the analytical signal versus the added standard concentration to create a calibration curve. 5) Extrapolate the calibration curve to the point where the analytical signal is zero, which corresponds to the original concentration of the analyte in the sample.
• Analyze how the standard addition method can help overcome matrix effects and improve the accuracy of quantitative chemical analysis.
  • The standard addition method helps overcome matrix effects by directly incorporating the sample matrix into the calibration process. By adding known amounts of the analyte to the sample, the method accounts for any interactions or interferences between the analyte and the sample components, which can affect the analytical signal. This allows for a more accurate determination of the original analyte concentration, as the calibration curve is specific to the sample being analyzed. Additionally, the standard addition method does not require a separate calibration standard, which can further improve the accuracy of the analysis by eliminating potential errors associated with the preparation and handling of external standards.

Related terms

Analyte: The specific chemical component in a sample that is being measured or analyzed.

Matrix Effect: The influence of sample components other than the analyte on the measurement or detection of the analyte.

Calibration Curve: A plot of the analytical signal versus the concentration of the analyte, used to determine the concentration of an unknown sample.