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Related Concept Videos

Dialysis01:15

Dialysis

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Dialysis is a diffusion-based purification process that separates analyte molecules from a complex matrix. This is accomplished by allowing molecules in the solution to pass through a semipermeable membrane into a liquid on the other side. The membrane is usually made of cellulose acetate or cellulose nitrate, and the second liquid must be miscible with the solution. Ions (e.g., chloride or sodium) or organic molecules (e.g., glucose) can pass through the membrane pores, which generally have...
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Buffer solutions do not have an unlimited capacity to keep the pH relatively constant . Instead, the ability of a buffer solution to resist changes in pH relies on the presence of appreciable amounts of its conjugate weak acid-base pair. When enough strong acid or base is added to substantially lower the concentration of either member of the buffer pair, the buffering action within the solution is compromised.
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Peritoneal Dialysis I: Introduction and Procedure01:30

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Peritoneal dialysis (PD) is a procedure that facilitates the exchange of solutes, waste products, electrolytes, and excess fluid between the blood in the peritoneal capillaries and a dialysis solution introduced into the peritoneal cavity.Principles of Peritoneal Dialysis (PD)Diffusion: Waste products such as urea and electrolytes move from high concentrations in the blood to low concentrations in the dialysate across the peritoneal membrane. This mechanism is driven by the concentration...
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Formation of Dilute Urine01:20

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The formation of dilute urine is a critical renal adaptation that maintains fluid balance, particularly during periods of high fluid intake. This process primarily involves the juxtamedullary nephrons. By adjusting the permeability of water and ions in response to physiological conditions, the kidneys can either conserve or excrete water, resulting in concentrated or dilute urine.
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DialyzersA hemodialysis (HD) dialyzer is a plastic cartridge containing thousands of parallel hollow fibers, which serve as semipermeable membranes. These fibers are typically made from cellulose-based or other synthetic materials. During HD, blood is pumped into the top of the cartridge and distributed among these fibers. Simultaneously, dialysis fluid, known as dialysate, is introduced into the bottom of the cartridge, bathing the outside of the fibers. Across the semipermeable membrane,...
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Hemodialysis I: Introduction01:25

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Three-Dimensionally Printed Microfluidic Cross-flow System for Ultrafiltration/Nanofiltration Membrane Performance Testing
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pH variations during diafiltration due to buffer nonidealities.

Youngbin Baek1, Deyu Yang1, Nripen Singh2

  • 1Dept. of Chemical Engineering, The Pennsylvania State University, University Park, PA, 16802.

Biotechnology Progress
|August 26, 2017
PubMed
Summary
This summary is machine-generated.

Diafiltration pH shifts are caused by nonideal acid-base equilibria, not protein interactions. Matching ionic strength in feed and buffer eliminates these pH variations during biotherapeutic formulation.

Keywords:
bioprocessingbuffer exchangediafiltrationionic strengthpH

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Area of Science:

  • Biopharmaceutical formulation
  • Chemical engineering
  • Biotechnology

Background:

  • Diafiltration is critical for biotherapeutic final formulation.
  • Buffer and excipient concentrations can vary post-diafiltration due to product interactions.
  • Observed pH variations during diafiltration are largely independent of protein concentration.

Purpose of the Study:

  • Investigate the cause of pH variations during diafiltration.
  • Develop a model for diafiltration accounting for nonideal acid-base equilibria.
  • Understand factors controlling pH profiles in diafiltration processes.

Main Methods:

  • Developed a model for diafiltration incorporating ionic strength-dependent pKa.
  • Conducted experiments using phosphate and histidine buffers.
  • Analyzed pH changes in relation to ionic strength variations.

Main Results:

  • Model predictions showed excellent agreement with experimental results.
  • Decreased ionic strength increased the pKa of phosphate buffer, shifting solution pH.
  • pH shifts occurred even when initial feed and diafiltration buffer pH were identical.

Conclusions:

  • Nonidealities in acid-base equilibrium coefficients explain observed pH variations.
  • Ionic strength is a critical factor influencing pH during diafiltration.
  • Matching ionic strength between feed and diafiltration buffer eliminates pH shifts.