An internal standard, in analytical chemistry and laboratory testing, is a substance deliberately added to multiple samples within an experiment, including blank samples, calibration standards, and unknown samples. Its primary purpose is to enhance the precision and accuracy of the assay or analysis being conducted. Here are some key points about internal standards:
- Precision Improvement: The internal standard contains a known concentration of a reference substance or compound. By adding this known substance to all samples, it helps to ensure that the conditions of each sample are as similar as possible, which in turn improves the precision of the assay.
- Quality Control: Internal standards are an integral part of the quality control process in analytical chemistry. They serve as a means to verify the accuracy and reliability of the experimental procedure.
- CalibrationThe act of checking or adjusting (by comparison with a standard) the accuracy of a measuring instrument. Operation that, under specified conditions, in a first step, establishes a relation between the quantity values with measurement uncertainties provided by measurement standards and corresponding indications with associated measurement uncertainties and, in a second step, uses this information to establish a relation for obtaining a measurement result from an indication. More: The internal standard is used in the calibration of the analytical instrument or method. It provides a reference point against which the responses of other samples can be compared.
- Monitoring Instrument Performance: The response of the analytical instrument to the internal standard is closely monitored. If the instrument’s response to the internal standard is unexpected or falls outside an acceptable range, it may indicate a problem with the instrument’s performance or the experimental conditions. In such cases, the results for all samples in that run may be compromised.
- Compensation for Variability: In complex analytical methods, variations in sample preparation, instrument conditions, or other factors can affect the accuracy of measurements. The internal standard helps to correct for these variations by providing a consistent reference point.
- Examples: Internal standards can vary depending on the type of analysis. In gas chromatography, for instance, a known compound with a specific retention time might be used as an internal standard. In mass spectrometry, a stable isotope-labeled compound can serve as an internal standard.
- DataInformation in analog or digital form that can be transmitted or processed. More Analysis: During data analysis, the response of the internal standard is used to adjust the results obtained from other samples. This adjustment accounts for any variations or drift in instrument response.
- Statistical Control: Internal standards contribute to statistical control in analytical processes, allowing for the detection of outliers or problems in real-time. If the internal standard response deviates significantly, it may prompt re-analysis or investigation.
In summary, an internal standard is a known substance intentionally added to multiple samples in an experiment to enhance precision and quality control. By monitoring the response of the internal standard, analysts can assess the reliability of the experimental run and make necessary corrections to ensure accurate and valid results for other samples in the analysis.
