Explain the following statement: "The validity of a chemical analysis ultimately depends on measuring the response of the analytical procedure to known standards."
(b) Calibration curves are necessary in many chemical measurements involving electrochemistry, spectroscopy and chromatography. Many aspects of a calibration are part of the “figures of merit” for an analysis. Define 5 figures of merit and discuss ways in which these could be evaluated in the process of establishing a calibration. PLZ HELP.....
wwe must know the response of an analytical procedure to know quatities before the procedure can be used for an unknown.
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The statement "The validity of a chemical analysis ultimately depends on measuring the response of the analytical procedure to known standards" means that in order to determine the accuracy and reliability of a chemical analysis, it is essential to compare the results obtained from an unknown sample to those obtained from known standard samples.
Calibration curves are important in many chemical measurements involving electrochemistry, spectroscopy, and chromatography. These curves help establish a relationship between the concentration or amount of a substance being analyzed and the instrumental response (e.g., peak intensity, current, absorbance). The figures of merit associated with calibration are parameters that assess the performance of the analytical method and its ability to produce accurate and precise results.
Here are five commonly used figures of merit and ways to evaluate them during the process of establishing a calibration:
1. Accuracy: Accuracy refers to how close the measured values are to the true or accepted values. To evaluate accuracy, known standard samples with known concentrations or amounts are analyzed using the calibration procedure. The measured values are then compared to the reference values, and the difference between them provides an indication of accuracy.
2. Precision: Precision is the measure of how close individual measurements are to each other. To evaluate precision, replicate measurements of the same known standard are performed and the standard deviation or relative standard deviation (RSD) is calculated. A smaller deviation or RSD indicates higher precision.
3. Linearity: Linearity assesses the relationship between the analyte concentration or amount and the instrumental response. Calibration curves are used to evaluate linearity by plotting the response values against the known concentrations or amounts. A straight line with a high correlation coefficient (close to 1) indicates good linearity.
4. Sensitivity: Sensitivity measures the change in the instrumental response for a given change in analyte concentration. It is typically represented by the slope of the calibration curve. A higher slope indicates greater sensitivity, meaning that small changes in concentration can be accurately detected.
5. Limit of Detection (LOD) and Limit of Quantitation (LOQ): LOD and LOQ represent the lowest analyte concentration or amount that can be reliably detected or quantified, respectively. These figures of merit can be evaluated by gradually diluting a known standard until the signal is just above the noise level (LOD) or reliably quantifiable (LOQ).
By evaluating these figures of merit during the calibration process, one can determine the reliability and accuracy of the analytical procedure, ensuring that valid results can be obtained for the unknown samples.