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Related Concept Videos

Titration of Polyprotic Base with a Strong Acid01:18

Titration of Polyprotic Base with a Strong Acid

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The titration of a polyprotic base such as sodium carbonate with a strong acid such as hydrochloric acid results in two equivalence points on the titration curve. At the first equivalence point, the carbonate ions in the base are completely converted to bicarbonate ions. The second equivalence point corresponds to the complete conversion of bicarbonate ions to carbonic acid, which dissociates into carbon dioxide and water. The region before the first equivalence point corresponds to the...
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Titration of a Weak Acid with a Weak Base01:08

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Weak acids and bases do not undergo dissociation completely, and titrations between these two are rarely studied. When such studies are performed, say, for the titration of a weak acid with a weak base, the titration curve plots the change in pH as a function of the volume of base added. Take the titration of acetic acid with ammonia, for instance. During the titration, these two species form ammonium acetate and water, but the pH change is slow and gradual.
As a result, there is no simple...
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Titration of a Weak Base with a Strong Acid01:20

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The titration curve of a weak base like ammonia with a strong acid like hydrochloric acid is the mirror image of the titration curve of a weak acid with a strong base.
Using the ICE table and substituting the Kb value, we calculate the initial pH of 50 mL of 0.1 M ammonia to be 11.11. Addition of 25 mL of 0.1 M hydrochloric acid to this solution of ammonia results in a buffer with an equal concentration of ammonia and ammonium ions. The pH of this buffer can be calculated by substituting these...
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A buffer can prevent a sudden drop or increase in the pH of a solution after the addition of a strong acid or base up to its buffering capacity; however, such addition of a strong acid or base does result in the slight pH change of the solution. The small pH change can be calculated by determining the resulting change in the concentration of buffer components, i.e., a weak acid and its conjugate base or vice versa. The concentrations obtained using these stoichiometric calculations can be used...
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Bicarbonate-Carbonic Acid Buffer01:22

Bicarbonate-Carbonic Acid Buffer

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The carbonic acid-bicarbonate buffer system is critical for maintaining the body's pH balance. It operates on the equilibrium:
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Mixtures of Acids01:19

Mixtures of Acids

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The pH of a solution containing an acid can be determined using its acid dissociation constant and initial concentration. If a solution contains two different acids, then its pH can be determined using one of several methods depending on the relative strength of the acids and their dissociation constants.
In a strong and weak acid mixture, the strong acid dissociates completely and becomes a source of almost all the hydronium ions present in the solution. In contrast, the weak acid shows...
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Bicarbonate Buffer Dissolution Test Using the Floating Lid Method: Inter-Laboratory Reproducibility of pH

Masahiro Fushimi1,2, Masaki Higashino2,3, Shotaro Ikuta4

  • 1Sawai Pharmaceutical Co., Ltd., 5-2-30 Miyahara, Yodogawa-ku, Osaka 532-0003, Japan.

Chemical & Pharmaceutical Bulletin
|August 12, 2025
PubMed
Summary

The floating lid method effectively maintains pH in bicarbonate buffer (BCB) dissolution tests, confirming inter-laboratory reproducibility for both paddle and flow-through cell methods.

Keywords:
bicarbonate bufferbiorelevant bufferfloating lidin vivo predictive dissolutioninter-laboratory reproducibility

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Area of Science:

  • Pharmaceutical Science
  • Analytical Chemistry
  • Physical Chemistry

Background:

  • Bicarbonate buffer (BCB) is challenging for dissolution testing due to pH drift caused by CO2 escape.
  • The floating lid method offers a potential solution for stable BCB use in dissolution tests.

Purpose of the Study:

  • To confirm the inter-laboratory reproducibility of pH maintenance using the floating lid method with BCB.
  • To evaluate the effectiveness of the floating lid method in both paddle and flow-through cell (FTC) dissolution apparatus.

Main Methods:

  • Three pharmaceutical companies and one academic institute participated.
  • Bicarbonate buffer solution (pH 6.5, 15 mM) was used as the test medium.
  • pH stability was assessed with and without the floating lid in paddle (50 and 100 rpm) and FTC methods.

Main Results:

  • Without the floating lid, significant pH increases (ΔpH > 1.6) were observed in both paddle and FTC methods.
  • The floating lid method minimized pH changes, with ΔpH generally below 0.4 across all conditions.
  • Standard deviations for ΔpH were consistently low (≤0.05), indicating high reproducibility.

Conclusions:

  • The floating lid method demonstrates excellent inter-laboratory reproducibility for maintaining BCB pH in dissolution testing.
  • This method is effective for both paddle and FTC dissolution apparatus, overcoming previous limitations of BCB use.