What's the purpose of a blank, a postivie control and a negative control??
(say, for an experiement with a spectrophotometer).
In an experiment, a blank, a positive control, and a negative control serve distinct purposes. Let's specifically discuss their relevance in an experiment involving a spectrophotometer.
1. Blank: A blank is a reference solution used to calibrate the spectrophotometer and account for any background absorbance or interference from the solvent or reagents. To prepare a blank, you would typically use all the same components as your experimental samples except for the analyte you are measuring. By measuring the absorbance of the blank, you can subtract this background absorbance from your sample readings later on. This helps ensure that any changes in absorbance you observe are due to the analyte being measured and not other factors.
2. Positive control: A positive control is a sample or treatment that is known to produce a response or change that you expect to observe. In the context of a spectrophotometer experiment, a positive control could be a sample with a known concentration of the analyte you are measuring. By comparing your experimental samples to the positive control, you can confirm that the spectrophotometer is working correctly and that your measurements are accurate. It also serves as a reference point to gauge the magnitude of the response or change you should expect in your experimental samples.
3. Negative control: A negative control, on the other hand, is a sample or treatment that is expected to show no response or change. It helps to determine whether any observed responses in your experimental samples are specific to the analyte being measured or if they are occurring due to other factors. In a spectrophotometer experiment, a negative control could be a sample containing all the same components as your experimental samples but lacking the analyte of interest. By comparing the absorbance values of your negative control to those of your experimental samples, you can assess the specificity of the measurement and ensure that the observed changes are not due to any interfering factors.
Overall, using a blank, positive control, and negative control in a spectrophotometer experiment helps you establish a baseline for background absorbance, verify the accuracy of your measurements, and ensure the specificity of your observations.