Assay of serum (plasma) bicarbonate and total carbon dioxide by titrimetric method

Summary

Add excess standard hydrochloric acid solution to plasma (clear), so that the acid and HCO3-neutralization reaction, the release of CO2 and then standard sodium hydroxide titration of the remaining hydrochloric acid, sodium hydroxide consumption calculated plasma HCO3- content, plasma (clear) of the original PH as the end point of the titration. The plasma (clear) is added with excess standard hydrochloric acid solution, so that the acid neutralizes with HCO3-, releasing CO2, and then the remaining hydrochloric acid is titrated with standard sodium hydroxide, and the content of plasma HCO3- is calculated by the consumption of sodium hydroxide, and the original pH of plasma (clear) is used as the end point of the titration.

Operation method

Serum (plasma) bicarbonate and total carbon dioxide assay by titration

Principle

The plasma (clear) is added with an excess of standard hydrochloric acid solution, so that the acid reacts with HCO3- to release CO2, and then the remaining hydrochloric acid is titrated with standard sodium hydroxide, and the plasma HCO3- content is calculated by the consumption of sodium hydroxide, and the original pH of the plasma (clear) is used as the end point of the titration.

Move

I. Experimental reagents:

1. 0.01 mol/L hydrochloric acid: take 1.0 ml of accurately calibrated 1.00 mol/L hydrochloric acid solution, transfer it to a 100 ml volumetric flask, and dilute it to the scale with physiological saline.

2. 0.01mol/L sodium hydroxide: take 1.0ml of precisely calibrated 100mol/L sodium hydroxide solution and transfer it to a 100ml volumetric flask, dilute it to the scale with physiological saline, this solution should be kept in airtight condition and can be used for about 1 week.

3. Phenol red indicator: weigh 50mg of phenol red, add 0.01mol/L sodium hydroxide 14.1ml, grind and dissolve, add saline to 250ml.

4. physiological saline

Second, the experimental operation: take 2 small test tubes, marked determination tube and control tube, each tube add fresh plasma (or serum) 0.1ml, phenol red indicator 2 drops, the control tube add saline 2.5ml, determination tube accurately add 0.01mol / L hydrochloric acid 0.5ml. shaking for 1 minute, so that CO2 escape, and then add 2ml of saline, mixing, and then use a microburette to the 0.01mol/L sodium hydroxide was added drop by drop until the same color as the control tube as the end point.

III. Calculation:

Serum (plasma) HCO3-mmol/L=(0.5-number of ml of 0.01 mol/L sodium hydroxide for titration)×0.01×(1000/0.1)

Reference value: HCO3-adult: 20-29 mmol/L

Children: 18-27 mmol/L

Caveat

1. blood specimens should avoid contact with air and quickly separate plasma for timely manipulation.

2. All utensils must be neutral or the results will be affected.

3. 0.0lmol/L sodium hydroxide is not stable, should be sealed and stored to avoid absorption of CO20, 0.01mol/L hydrochloric acid is more stable, so every day should be done to correct the titration, using phenol red as an indicator to red for 10 seconds without fading as the end point of the determination of the results, but also compared to the former two content is very little.

4. Physiological saline must be neutral, acidic or alkaline will affect the accuracy of the results.

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