Experimental determination of the half-life of sodium salicylate

Summary

The half-life of salicylic acid was determined by the colorimetric method, the salicylic acid root reacts with iron ions to form a purple complex, the optical density was obtained by colorimetry according to the color of the purple complex, and the half-life was calculated by substituting the optical density into the formula. The purpose of this experiment is to master the determination of plasma half-life (t1/2) of drugs and calculate the plasma half-life (t1/2).

Operation method

colorimetric method

Principle

Salicylate reacts with iron ions to form a purple complex, the optical density is obtained by colorimetry based on the color of the purple complex, and the half-life is calculated by substituting the optical density into the formula.

Materials and Instruments

Rabbit
Sodium salicylate solution Trichloroacetic acid solution Ferric chloride solution Heparin solution
Test tubes Centrifuge tubes Graduated pipettes Syringes Spectrophotometer Model 721 Centrifuge Pipette holders Alcohol cotton balls Dried cotton Bamboo sticks

Move

1. A rabbit was taken, weighed, and 2 ml of blood was taken from the heart with a syringe moistened with 0.5% heparin (as a control blood sample), followed by injection of 1.5 m/kg of 10% salicylate solution (150 mg/kg) into the ear vein. 2. 5 minutes and 35 minutes after injection, 2 ml of blood was taken from the heart.
2. 5 minutes and 35 minutes after the injection, 2 ml of blood was withdrawn from the heart, and the blood from the above three draws was put into three centrifuge tubes pre-filled with 7 ml of trichloroacetic acid and stirred and centrifuged (1,500 rpm) for 5 minutes, so that plasma proteins could be precipitated. 3.
3. 6 ml of each supernatant was accurately sucked into test tubes, and 0.6 ml (or 12 drops) of ferric chloride solution was added to each tube and shaken well to develop the color. 4.
4. Take the pre-drug tube as the control, use the colorimeter with a wavelength of 510 nm, 1 cm aperture cuvette for colorimetry, and read the optical density of the supernatant of the two tubes after the administration of the drug (x1, x2).
5. Find the half-life t =1/2 according to the following equation (x1, x2 are the optical densities of the two post-dose blood concentrations and t is the time between the two blood samplings)

Caveat

⒈ heart blood: the rabbit lying on its back, with the left thumb on one side of the sternum, the index finger and middle finger on the other side of the sternum to fix the heart, in the heart tipIn the most obvious beat of the tip of the heart, the needle and the chest wall perpendicular to the thoracic cavity, when the hand holding the needle felt the heart beat, and then slightly stabbed into the heart, and then draw blood.The blood is then withdrawn. When extracting blood, it is advisable to use a 7-8 gauge needle, and the needle should be inserted straight into the chest cavity, without exploring the chest cavity from side to side.In order to prevent coagulation, the inside of the syringe should be moistened with 0.5% heparin solution when blood is taken from the heart.

Common Problems

I. What is the clinical significance of determining the half-life of a drug?

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