The key difference between kinetic and end point reaction is that in kinetic reaction method, we measure the difference in absorbance between two points during the progression of the reaction whereas, in end point reaction method, we measure the total amount of analytes that participate in the reaction.
The kinetic reaction method and the end point reaction method are useful in enzyme analysis. We mainly use these methods in clinical chemistry. Other than these two methods, there is another method; fixed time method.
CONTENTS
1. Overview and Key Difference
2. What is Kinetic Reaction
3. What is End Point Reaction
4. Side by Side Comparison – Kinetic vs End Point Reaction in Tabular Form
5. Summary
What is Kinetic Reaction?
Kinetic reaction method is an analysis method used in clinical chemistry to determine the difference in absorbance between two points of the progression of a reaction. Here, we use a specified time period for this determination. We should assume this determination; a constant amount of product forms during the time interval being monitored. Usually, we consider a short time period (20 seconds to 1 minute). That is to avoid any effect comes from enzyme degradation during the progression of the reaction.
Before starting the reaction, we should perform a pre-incubation in order to avoid any interferences comes from substances other than the analyte. During the pre-incubation, these substances completely react with the reagent system. There are two major types as;
- Increasing type: the reaction proceeds in a positive Here the initial absorbance is always a lower value than the final absorbance.
- Decreasing type: the reaction proceeds in the negative The initial absorbance is a higher value than the final absorbance.
What is End Point Reaction?
End point reaction method is an analysis method useful in clinical chemistry to determine the total amount of analytes consumed during the progression of a reaction. in this method, we consider the end point of reaction rather than two specific points as in kinetic method. Usually, the end point comes within 5 to 15 minutes at 37 ◦C.
Figure 01: We can use Spectrophotometers to measure the Absorbance
The reaction may give either a colored product or a colorless product at the end. However, we can measure the absorbance of this product using a spectrophotometer. The absorbance of the sample increases with time. It reaches a stable value which will not change further with time. This is the end point of the reaction.
What is the Difference Between Kinetic and End Point Reaction?
Kinetic reaction method is an analysis method used in clinical chemistry to determine the difference in absorbance between two points of the progression of a reaction. Here, we measure the difference in absorbance between two points during the progression of the reaction. Moreover, the time taken for this reaction is around 20 seconds to 1 minute. Whereas, the end point reaction method is an analysis method used in clinical chemistry to determine the total amount of analytes consumed during the progression of a reaction. In this method we measure the total amount of analytes that participate in the reaction. Furthermore, the time period taken for this reaction is 5 to 15 minutes.
Summary – Kinetic vs End Point Reaction
There are three main reaction methods that we use in clinical chemistry for the analysis of enzymatic reactions; kinetic method, fixed time method and end point method. The difference between kinetic and end point reaction is that in kinetic reaction method, we measure the difference in absorbance between two points during the progression of the reaction whereas in end point reaction method, we measure the total amount of analytes that participate in the reaction.
Reference:
1. “Climical Chemistry Methodologies.” The Verdict of Circuit Court in Lomza in 1949 – Piotr Gontarczyk. Available here
Image Courtesy:
1.’7152514131′ by Vivien Rolfe (CC BY-SA 2.0) via Flickr