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Related Concept Videos

Factors Influencing Microbial Growth: pH01:29

Factors Influencing Microbial Growth: pH

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Microorganisms are classified as acidophiles, neutrophiles, or alkaliphiles based on their pH growth preferences, reflecting their adaptations to specific environments. Maintaining a stable intracellular pH is critical for macromolecular stability and enzymatic activity, which can be challenged by external pH variations.Neutrophiles, such as Escherichia coli, grow optimally between pH 5.5 and 8.0. These microorganisms inhabit neutral or slightly acidic environments and employ mechanisms like...
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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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Hydronium and hydroxide ions are present both in pure water and in all aqueous solutions, and their concentrations are inversely proportional as determined by the ion product of water (Kw). The concentrations of these ions in a solution are often critical determinants of the solution’s properties and the chemical behaviors of its other solutes. Two different solutions can differ in their hydronium or hydroxide ion concentrations by a million, billion, or even trillion times. A common means of...
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The pH of a salt solution is determined by its component anions and cations. Salts that contain pH-neutral anions and the hydronium ion-producing cations form a solution with a pH less than 7. For example, in ammonium nitrate (NH4NO3) solution, NO3− ions do not react with water whereas NH4+ ions produce the hydronium ions resulting in the acidic solution.  In contrast, salts that contain pH-neutral cations and the hydroxide ion-producing anions form a solution with a pH greater than...
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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.
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Acid–Base Equilibria: Activity-Based Definition of pH01:10

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For an ideal solution, the pH is defined as the negative logarithm of the hydrogen ion concentration. For a non-ideal solution, an accurate measurement of the pH must consider the negative logarithm of the hydrogen ion activity rather than concentration. In such a solution, the pH can be more accurately defined as the negative logarithm of a product of the hydrogen ion concentration and its activity coefficient.
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Measuring Phosphorus Release in Laboratory Microcosms for Water Quality Assessment
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Development of a Quantitative Method for Formulation Microenvironmental pH Assessment.

Mariana Romero-Gonzalez1, Robert D Van Horn2, Youlin Liu2

  • 1Department of Pharmaceutical Sciences, University of Michigan, Ann Arbor, Michigan 48109, United States.

Molecular Pharmaceutics
|August 5, 2025
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Summary
This summary is machine-generated.

This study introduces a new method for measuring microenvironmental pH in pharmaceutical formulations using fluorescent dyes and microscopy. This technique aids in optimizing drug delivery and stability.

Keywords:
confocal laser scanning microscopydual-emission pH-sensitive fluorescent dyesmicroenvironmental pHpH modifiersolid dispersion

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Area of Science:

  • Pharmaceutical Sciences
  • Analytical Chemistry
  • Materials Science

Background:

  • Pharmaceutical formulations often contain pH modifiers to enhance drug dissolution and stability.
  • Ionizable drugs exhibit pH-dependent solubility, necessitating precise control of the microenvironmental pH.
  • Current methods for assessing microenvironmental pH in complex formulations can be limited.

Purpose of the Study:

  • To develop a quantitative method for assessing the microenvironmental pH of pharmaceutical formulations.
  • To enable spatial pH mapping within dissolving drug compacts.
  • To provide a tool for optimizing oral pharmaceutical formulations.

Main Methods:

  • Utilized dual-emission pH-sensitive fluorescent dyes for imaging.
  • Employed confocal laser scanning microscopy to visualize dissolving formulation compacts.
  • Analyzed images using Python code to generate quantitative pH maps.

Main Results:

  • Successfully mapped spatial pH changes across distinct layers of dissolving compacts.
  • Demonstrated pH mapping over a broad pH range using two different fluorescent dyes.
  • Validated a robust technique for microenvironmental pH assessment.

Conclusions:

  • The developed technique offers a reliable method for assessing microenvironmental pH in pharmaceutical formulations.
  • This approach can optimize formulation performance and stability, reducing reformulation needs.
  • The technique has the potential to expedite the development of new pharmaceutical products.