Electrochemical removal of amphoteric ions

Several harmful or valuable ionic species present in seawater, brackish water, and wastewater are amphoteric, weak acids or weak bases, and, thus, their properties depend on local water pH. Effective removal of these species can be challenging for conventional membrane technologies, necessitating chemical dosing of the feedwater to adjust pH. A prominent example is boron, which is considered toxic in high concentrations and often requires additional membrane passes to remove during seawater desalination. Capacitive deionization (CDI) is an emerging membraneless technique for water treatment and desalination, based on electrosorption of salt ions into charging microporous electrodes. CDI cells show strong internally generated pH variations during operation, and, thus, CDI can potentially remove pH-dependent species without chemical dosing. However, development of this technique is inhibited by the complexities inherent to the coupling of pH dynamics and ion properties in a charging CDI cell. Here, we present a theoretical framework predicting the electrosorption of pH-dependent species in flow-through electrode CDI cells. We demonstrate that such a model enables insight into factors affecting species electrosorption and conclude that important design rules for such systems are highly counterintuitive. For example, we show both theoretically and experimentally that for boron removal, the anode should be placed upstream and the cathode downstream, an electrode order that runs counter to the accepted wisdom in the CDI field. Overall, we show that to achieve target separations relying on coupled, complex phenomena, such as in the removal of amphoteric species, a theoretical CDI model is essential.

An In Vivo Predictive Dissolution Methodology (iPD Methodology) with a BCS Class IIb Drug Can Predict the In Vivo Bioequivalence Results: Etoricoxib Products

The purpose of this study was to predict in vivo performance of three oral products of Etoricoxib (Arcoxia® as reference and two generic formulations in development) by conducting in vivo predictive dissolution with GIS (Gastro Intestinal Simulator) and computational analysis. Those predictions were compared with the results from previous bioequivalence (BE) human studies. Product dissolution studies were performed using a computer-controlled multicompartmental dissolution device (GIS) equipped with three dissolution chambers, representing stomach, duodenum, and jejunum, with integrated transit times and secretion rates. The measured dissolved amounts were modelled in each compartment with a set of differential equations representing transit, dissolution, and precipitation processes. The observed drug concentration by in vitro dissolution studies were directly convoluted with permeability and disposition parameters from literature to generate the predicted plasma concentrations. The GIS was able to detect the dissolution differences among reference and generic formulations in the gastric chamber where the drug solubility is high (pH 2) while the USP 2 standard dissolution test at pH 2 did not show any difference. Therefore, the current study confirms the importance of multicompartmental dissolution testing for weak bases as observed for other case examples but also the impact of excipients on duodenal and jejunal in vivo behavior.

Overcoming Chemoresistance: Altering pH of Cellular Compartments by Chloroquine and Hydroxychloroquine

Resistance to the anti-cancer effects of chemotherapeutic agents (chemoresistance) is a major issue for people living with cancer and their providers. A diverse set of cellular and inter-organellar signaling changes have been implicated in chemoresistance, but it is still unclear what processes lead to chemoresistance and effective strategies to overcome chemoresistance are lacking. The anti-malaria drugs, chloroquine (CQ) and its derivative hydroxychloroquine (HCQ) are being used for the treatment of various cancers and CQ and HCQ are used in combination with chemotherapeutic drugs to enhance their anti-cancer effects. The widely accepted anti-cancer effect of CQ and HCQ is their ability to inhibit autophagic flux. As diprotic weak bases, CQ and HCQ preferentially accumulate in acidic organelles and neutralize their luminal pH. In addition, CQ and HCQ acidify the cytosolic and extracellular environments; processes implicated in tumorigenesis and cancer. Thus, the anti-cancer effects of CQ and HCQ extend beyond autophagy inhibition. The present review summarizes effects of CQ, HCQ and proton pump inhibitors on pH of various cellular compartments and discuss potential mechanisms underlying their pH-dependent anti-cancer effects. The mechanisms considered here include their ability to de-acidify lysosomes and inhibit autophagosome lysosome fusion, to de-acidify Golgi apparatus and secretory vesicles thus affecting secretion, and to acidify cytoplasm thus disturbing aerobic metabolism. Further, we review the ability of these agents to prevent chemotherapeutic drugs from accumulating in acidic organelles and altering their cytosolic concentrations.

Towards a Notion of Basis for Knowledge-Based Systems—Applications

In the paradigm of Knowledge-Based Systems (KBS), the design of methods to simplify the reasoning leads to more efficient processes. A point of view that provides valuable insights is the algebraic one. In this work, a notion of basis (and dimension) for Knowledge Bases in Propositional Logic associated with knowledge forgetting is introduced. It is based on ideas that come from the translation of such logic in (Computer) Algebra, particularly from the interpretation of variable forgetting. In this paper, the concept of weak base is defined as a set of variables sufficient to decide the consistency using variable forgetting. Several applications of weak bases are presented in order to show their usefulness in KBS reasoning and to justify their study and use in solving problems within this topic.

Strong Bases Behave as Weak Bases in Nanoscale Chemical Environments: Implication in Humidity-swing CO2 Air Capture

The hydration of ions/molecules in nanometer-sized clusters or nanoscopic pores is ubiquitous and plays a key role in many chemical and physical systems. In this work, the guanidine-H2O reactions with...

Acid Neutralizing Capacity of Selected Antacid Suspensions Available in the Ghanaian Market

Antacids are substances commonly used by patients to obtain fast symptomatic relief from dyspepsia. They are weak bases which neutralize excess gastric acid and subsequently raise the pH of the gastric contents. The potency of the antacids depends mainly on their acid neutralization capacity (ANC) and this can vary from one brand to another. Several dosage forms of antacids are available for use by patients. However, In Ghana, suspensions are the commonest dosage form of antacids which is preferred by patients. The objective of this study was to determine the acid neutralizing capacity of six (6) randomly selected brands of antacid suspensions on the Ghanaian market using potentiometric acid-base titration. The samples were coded A-F to avoid any bias in the study. All the sampled brands had more than one year to expiry as indicated on their label. Brand D had the highest ANC of 29.70 mEq/dose whiles brand A had the lowest ANC of 11.25 mEq/dose. From the results obtained, it can be inferred that acid neutralization can be more effective and rapidly achieved with liquid antacids containing a high amount of magnesium hydroxide and aluminium Hydroxide. Hence, for acute symptomatic relief from dyspepsia, antacids containing a higher concentration of magnesium hydroxide and aluminium hydroxide would be most beneficial to patients.

Utilization of Kalpataru Flower Extract (Hura crepitans Linn) as an Alternative Acid Base Indicator

Kalpataru flower (Hura crepitans Linn) is an anthocyanin-containing plant. This study aims to utilize extract from the kalpataru flower as an alternative acid base indicator and determine the type of acid-base titration suitable for extracting the kalpataru flower indicator. Kalpataru flowers are macerated with methanol solvent for around 2 hours. Kalpataru flower extract was tested as an indicator in acid-base solution, buffer, and compared with phenolphthalein and methyl orange for acid-base titration, namely: strong acids with strong bases, weak acids with strong bases, and weak bases with strong acids. The results obtained in this study were: indicator extract of brownish yellow kalpataru flowers, in strong red acids, in strong bases of dark green, in weak pink acids, and in weak bases in light green. In the buffer, the indicator extract of the kalpataru flower has a range of pH pH 4-5 (pink-colorless) and pH 9-11 (yellowish green-dark green). The indicator of kalpataru flower extract can be used on strong acid titration with strong bases, weak acids with strong bases and weak bases with strong acids. Kalpataru flower extract can be used as an acid-base indicator.