Surfactants B

Total Page:16

File Type:pdf, Size:1020Kb

Surfactants B 42 Physical Pharmacy chapter 4 7. Indicate which of the following statements relating to the effect of pH on drug stability are true: a. The rate of acid-catalysed decomposition of a drug increases with pH. Surfactants b. The rate of base-catalysed decomposition of a drug increases with the concentration of hydroxyl ions. c. The effect of buffer components on decomposition is referred to as general acid–base catalysis. Overview d. A plot of the observed-rate constant (as ordinate) against pH (as abscissa) for an acid-catalysed reaction has a gradient equal to k +. In this chapter we will: H Ⅲ see why certain molecules have the ability to lower the surface and interfacial tension and how the surface activity of a molecule is related to its molecular structure 8. What is the remaining concentration (a – x) in mg ml–1 of a drug (initial Ⅲ look at the properties of some surfactants that are commonly used in pharmacy –1 concentration a = 7 mg ml ) after a time equivalent to 3 half-lives assuming Ⅲ examine the nature and properties of monolayers formed when insoluble surfactants are that the decomposition follows fi rst-order kinetics? spread over the surface of a liquid a. 2.33 Ⅲ look at some of the factors that infl uence adsorption onto solid surfaces and see how b. 3.5 experimental data from adsorption experiments may be analysed to gain information on c. 1.75 the process of adsorption Ⅲ d. 0.875 see why micelles are formed, examine the structure of ionic and non-ionic micelles and look at some of the factors that infl uence micelle formation e. 1.167 Ⅲ examine the properties of liquid crystals and surfactant vesicles Ⅲ discuss the process of solubilisation of water-insoluble compounds by surfactant micelles 9. The time taken for 5% of a drug to decompose by fi rst-order kinetics is: and its applications in pharmacy. a. 0.022/k1 b. 0.051/k1 c. 0.105/k1 d. k /0.051 1 Some typical surfactants KeyPoint e. 0.105 k 1 Surfactants have two distinct Depending on their charge characteristics regions in their chemical structure, the surface-active molecules may be one of which is water-liking or anionic, cationic, zwitterionic (ampholytic) hydrophilic and the other of which or non-ionic. Examples of surfactants that is water-hating or hydrophobic. are used in pharmaceutical formulation are These molecules are referred to as follows: as amphiphilic or amphipathic molecules or simply as surfactants or surface active agents. Anionic surfactants: Sodium Lauryl Sulphate BP Ⅲ is a mixture of sodium alkyl sulfates, the chief of which is – + sodium dodecyl sulfate, C12 H25 SO4 Na Ⅲ is very soluble in water at room temperature, and is used pharmaceutically as a preoperative skin cleaner, having bacteriostatic action against gram-positive bacteria, and also in medicated shampoos Ⅲ is a component of emulsifying wax. Cationic surfactants Ⅲ The quaternary ammonium and pyridinium cationic surfactants are important pharmaceutically because of their 43 44 Physical Pharmacy Surfactants 45 bactericidal activity against a wide range of gram-positive and Reduction of surface and interfacial KeyPoints tension some gram-negative organisms. Ⅲ The molecules at the surface Ⅲ They may be used on the skin, especially in the cleaning of When surfactants are dissolved in water they of water are not completely wounds. orientate at the surface so that the hydrophobic surrounded by other molecules Ⅲ Their aqueous solutions are used for cleaning contaminated regions are removed from the aqueous as they are in the bulk of the utensils. environment, as shown in Figure 4.1a. The water. Ⅲ As a result there is a net inward reason for the reduction in the surface tension Non-ionic surfactants force of attraction exerted when surfactant molecules adsorb at the water on a molecule at the surface Ⅲ Sorbitan esters are supplied commercially as Spans and are surface is that the surfactant molecules replace from the molecules in the mixtures of the partial esters of sorbitol and its mono- and some of the water molecules in the surface and bulk solution, which results in di-anhydrides with oleic acid. They are generally insoluble the forces of attraction between surfactant and a tendency for the surface to in water (low hydrophile–lipophile balance (HLB) value) water molecules are less than those between two contract. This contraction is and are used as water-in-oil emulsifi ers and as wetting water molecules, hence the contraction force is spontaneous and represents a minimum free energy state. agents. reduced. Ⅲ Ⅲ We express the strength of Polysorbates are complex mixtures of contraction by the work required Figure 4.1 Orientation of amphiphiles at (a) solution– Tip partial esters of sorbitol and its mono- to increase the surface area by vapour interface and (b) hydrocarbon–solution interface. HLB stands for hydrophile–lipophile and di-anhydrides condensed with an 1 m2; this is referred to as the balance. Compounds with a high approximate number of moles of ethylene surface tension γ. HLB (greater than about 12) are oxide. They are supplied commercially Ⅲ Units of surface and interfacial –1 predominantly hydrophilic and as Tweens. The polysorbates are miscible Vapour phase tension are mN m . Aqueous solution water-soluble. Those with very low with water, as refl ected in their higher HLB values are hydrophobic and HLB values, and are used as emulsifying (a) water-insoluble. agents for oil-in-water emulsions. Ⅲ Poloxamers are synthetic block copolymers of hydrophilic Hydrocarbon poly(oxyethylene) and hydrophobic poly(oxypropylene) Aqueous solution with the general formula EmPnEm, where E = oxyethylene Hydrophobic group (OCH2CH2) and P = oxypropylene (OCH2CH(CH3)) and the subscripts m and n denote chain lengths. Properties such as (b) Hydrophilic group viscosity, HLB and physical state (liquid, paste or solid) are dependent on the relative chain lengths of the hydrophilic and hydrophobic blocks. They are supplied commercially Surfactants will also adsorb at the interface Tip as Pluronics and are labelled using the Pluronic grid, for between two immiscible liquids such as oil and When substituting values into example as F127 or L62, where the letter indicates the water and will orientate themselves as shown in equations it is important to convert physical state (F, P or L, denoting solid, paste or liquid, Figure 4.1b, with their hydrophilic group in the the values into the correct units. respectively). The last digit of this number is approximately water and their hydrophobic group in the oil. In the case of the Gibbs equation it is easy to forget to convert one-tenth of the weight percentage of poly(oxyethylene); the The interfacial tension at this interface, which concentration into mol m–3 fi rst one (or two digits in a three-digit number) multiplied arises because of a similar imbalance of attractive (1 mol l–1 = 1 mol dm–3 = 103 mol by 300 gives a rough estimate of the molecular weight of the forces as at the water surface, will be reduced by m–3). hydrophobe. this adsorption. There is an equilibrium between surfactant A wide variety of drugs, including the antihistamines and the molecules at the surface of the solution and those in the bulk of the tricyclic depressants, are surface-active. solution which is expressed by the Gibbs equation: 1 dγ Γ = – 2 xRT 2.303 d logc where Γ2 is the surface excess concentration, R is the gas constant 46 Physical Pharmacy Surfactants 47 –1 –1 –3 (8.314 J mol K ), T is temperature in kelvins, c is the concentration in mol m and x pressure π (π = γo – γm, where γo is the surface tension of the clean has a value of 1 for ionic surfactants in dilute solution. surface and γm is the surface tension of the fi lm-covered surface) The area A occupied by a surfactant molecule at the solution–air interface can be against area per molecule. calculated from A = 1/N Γ where N is the Avogadro number (6.023 × 1023 molecules A 2 A Figure 4.2 Langmuir trough. mol–1) and dγ/dlogc is the gradient of the plot of surface tension against logc measured at a concentration just below the critical micelle concentration (CMC). Tip The surface activity of a particular surfactant depends on the balance between its Fixed Remember when using Traube’s bar hydrophilic and hydrophobic properties. For rule that for every extra CH2 group in the compound you need 3 times a homologous series of surfactants: Film less of the compound to produce Ⅲ An increase in the length of the the same lowering of surface hydrocarbon chain (hydrophobic) tension. So if you add 2 extra CH 2 increases the surface activity. This groups you will require 9 times relationship between hydrocarbon chain less of the compound (not 6 times length and surface activity is expressed by Fixed less). bar Traube’s rule, which states that ‘in dilute Movable aqueous solutions of surfactants belonging bar to any one homologous series, the molar Side view Plan view Tip concentrations required to produce equal Remember that an increase in lowering of the surface tension of water surface activity means a decrease decreases threefold for each additional There are three main types of insoluble monolayers (Figure 4.3): in surface tension. Compounds Ⅲ CH2 group in the hydrocarbon chain of the Solid or condensed monolayers, in which the fi lm pressure that are most effective in lowering solute’. remains very low at high fi lm areas and rises abruptly when the surface tension are those with Ⅲ An increase of the length of the the molecules become tightly packed on compression. The a high surface activity. ethylene oxide chain (hydrophilic) of a extrapolated limiting surface area is very close to the cross- polyoxyethylated non-ionic surfactant sectional area of the molecule from molecular models.
Recommended publications
  • Effects of Surfactants on the Toxicitiy of Glyphosate, with Specific Reference to RODEO
    SERA TR 97-206-1b Effects of Surfactants on the Toxicitiy of Glyphosate, with Specific Reference to RODEO Submitted to: Leslie Rubin, COTR Animal and Plant Health Inspection Service (APHIS) Biotechnology, Biologics and Environmental Protection Environmental Analysis and Documentation United States Department of Agriculture Suite 5A44, Unit 149 4700 River Road Riverdale, MD 20737 Task No. 5 USDA Contract No. 53-3187-5-12 USDA Order No. 43-3187-7-0028 Prepared by: Gary L. Diamond Syracuse Research Corporation Merrill Lane Syracuse, NY 13210 and Patrick R. Durkin Syracuse Environmental Research Associates, Inc. 5100 Highbridge St., 42C Fayetteville, New York 13066-0950 Telephone: (315) 637-9560 Fax: (315) 637-0445 CompuServe: 71151,64 Internet: [email protected] February 6, 1997 TABLE OF CONTENTS EXECUTIVE SUMMARY ......................................... iii 1. INTRODUCTION .............................................1 2. CONSTITUENTS OF SURFACTANT FORMULATIONS USED WITH RODE0 ....4 2.1. AGRI-DEX ..........................................4 2.2. LI-700 .............................................4 2.3. R-11 ...............................................6 2.4. LATRON AG-98 ......................................6 2.5. LATRON AG-98 AG ....................................7 3. INFORMATION ON EFFECTS OF SURFACTANT FORMULATIONS ON THE TOXICITY OF RODEO ................................8 3.1. HUMAN HEALTH ......................................8 3.1.1. LI 700 ........................................8 3.1.2. Phosphatidylcholine ................................8
    [Show full text]
  • Is Colonic Propionate Delivery a Novel Solution to Improve Metabolism and Inflammation in Overweight Or Obese Subjects?
    Commentary in IgG levels in IPE-treated subjects versus Is colonic propionate delivery a novel those receiving cellulose supplementa- tion. This interesting discovery is the Gut: first published as 10.1136/gutjnl-2019-318776 on 26 April 2019. Downloaded from solution to improve metabolism and first evidence in humans that promoting the delivery of propionate in the colon inflammation in overweight or may affect adaptive immunity. It is worth noting that previous preclinical and clin- obese subjects? ical data have shown that supplementation with inulin-type fructans was associated 1,2 with a lower inflammatory tone and a Patrice D Cani reinforcement of the gut barrier.7 8 Never- theless, it remains unknown if these effects Increased intake of dietary fibre has been was the lack of evidence that the observed are directly linked with the production of linked to beneficial impacts on health for effects were due to the presence of inulin propionate, changes in the proportion of decades. Strikingly, the exact mechanisms itself on IPE or the delivery of propionate the overall levels of SCFAs, or the pres- of action are not yet fully understood. into the colon. ence of any other bacterial metabolites. Among the different families of fibres, In GUT, Chambers and colleagues Alongside the changes in the levels prebiotics have gained attention mainly addressed this gap of knowledge and of SCFAs, plasma metabolome analysis because of their capacity to selectively expanded on their previous findings.6 For revealed that each of the supplementa- modulate the gut microbiota composition 42 days, they investigated the impact of tion periods was correlated with different 1 and promote health benefits.
    [Show full text]
  • Sanitization: Concentration, Temperature, and Exposure Time
    Sanitization: Concentration, Temperature, and Exposure Time Did you know? According to the CDC, contaminated equipment is one of the top five risk factors that contribute to foodborne illnesses. Food contact surfaces in your establishment must be cleaned and sanitized. This can be done either by heating an object to a high enough temperature to kill harmful micro-organisms or it can be treated with a chemical sanitizing compound. 1. Heat Sanitization: Allowing a food contact surface to be exposed to high heat for a designated period of time will sanitize the surface. An acceptable method of hot water sanitizing is by utilizing the three compartment sink. The final step of the wash, rinse, and sanitizing procedure is immersion of the object in water with a temperature of at least 170°F for no less than 30 seconds. The most common method of hot water sanitizing takes place in the final rinse cycle of dishwashing machines. Water temperature must be at least 180°F, but not greater than 200°F. At temperatures greater than 200°F, water vaporizes into steam before sanitization can occur. It is important to note that the surface temperature of the object being sanitized must be at 160°F for a long enough time to kill the bacteria. 2. Chemical Sanitization: Sanitizing is also achieved through the use of chemical compounds capable of destroying disease causing bacteria. Common sanitizers are chlorine (bleach), iodine, and quaternary ammonium. Chemical sanitizers have found widespread acceptance in the food service industry. These compounds are regulated by the U.S. Environmental Protection Agency and consequently require labeling with the word “Sanitizer.” The labeling should also include what concentration to use, data on minimum effective uses and warnings of possible health hazards.
    [Show full text]
  • Hydrophilic Surface-Treating Aqueous Solution and Hydrophilic Surface
    Europaisches Patentamt (19) European Patent Office Office europeenpeen des brevets EP 0 654 514 B1 (12) EUROPEAN PATENT SPECIFICATION (45) Date of publication and mention (51) intci.6: C09D 201/00, C09D 177/04, of the grant of the patent: C09D 5/08, C23C 22/68, 09.12.1998 Bulletin 1998/50 C23C 22/66 (21) Application number: 94307102.7 (22) Date of filing: 28.09.1994 (54) Hydrophilic surface-treating aqueous solution and hydrophilic surface-treating method Hydrophile wassrige Oberflachenbehandlungslosung und hydrophiles Oberflachenbehandlungsverfahren Solution aqueuse hydrophile de traitement de surface, et methode de traitement de surface (84) Designated Contracting States: • Hirasawa, Hidekimi DE FR GB Yokohama-shi, Kanagawa (JP) • Yamasoe, Katsuyoshi (30) Priority: 06.10.1993 JP 250314/93 Yotsukaido-shi, Chiba (JP) (43) Date of publication of application: (74) Representative: Stuart, Ian Alexander et al 24.05.1995 Bulletin 1995/21 MEWBURN ELLIS York House (73) Proprietor: Nippon Paint Co., Ltd. 23 Kingsway Kita-ku, Osaka-shi, Osaka 531 (JP) London WC2B 6HP (GB) (72) Inventors: (56) References cited: • Matsukawa, Masahiko EP-A- 0 413 260 US-A-4 828 616 Kawasaki-shi, Kanagawa (JP) US-A- 4 908 075 US-A- 4 973 359 • Mikami, Fujio Yokohama-shi, Kanagawa (JP) DO ^> lo ^- LO CO Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice the Patent Office of the Notice of shall be filed in o to European opposition to European patent granted. opposition a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid.
    [Show full text]
  • Pulmonary Surfactant: the Key to the Evolution of Air Breathing Christopher B
    Pulmonary Surfactant: The Key to the Evolution of Air Breathing Christopher B. Daniels and Sandra Orgeig Department of Environmental Biology, University of Adelaide, Adelaide, South Australia 5005, Australia Pulmonary surfactant controls the surface tension at the air-liquid interface within the lung. This sys- tem had a single evolutionary origin that predates the evolution of the vertebrates and lungs. The lipid composition of surfactant has been subjected to evolutionary selection pressures, partic- ularly temperature, throughout the evolution of the vertebrates. ungs have evolved independently on several occasions pendent units, do not necessarily stretch upon inflation but Lover the past 300 million years in association with the radi- unpleat or unfold in a complex manner. Moreover, the many ation and diversification of the vertebrates, such that all major fluid-filled corners and crevices in the alveoli open and close vertebrate groups have members with lungs. However, lungs as the lung inflates and deflates. differ considerably in structure, embryological origin, and Surfactant in nonmammals exhibits an antiadhesive func- function between vertebrate groups. The bronchoalveolar lung tion, lining the interface between apposed epithelial surfaces of mammals is a branching “tree” of tubes leading to millions within regions of a collapsed lung. As the two apposing sur- of tiny respiratory exchange units, termed alveoli. In humans faces peel apart, the lipids rise to the surface of the hypophase there are ~25 branches and 300 million alveoli. This structure fluid at the expanding gas-liquid interface and lower the sur- allows for the generation of an enormous respiratory surface face tension of this fluid, thereby decreasing the work required area (up to 70 m2 in adult humans).
    [Show full text]
  • The Lower Critical Solution Temperature (LCST) Transition
    Copyright by David Samuel Simmons 2009 The Dissertation Committee for David Samuel Simmons certifies that this is the approved version of the following dissertation: Phase and Conformational Behavior of LCST-Driven Stimuli Responsive Polymers Committee: ______________________________ Isaac Sanchez, Supervisor ______________________________ Nicholas Peppas ______________________________ Krishnendu Roy ______________________________ Venkat Ganesan ______________________________ Thomas Truskett Phase and Conformational Behavior of LCST-Driven Stimuli Responsive Polymers by David Samuel Simmons, B.S. Dissertation Presented to the Faculty of the Graduate School of The University of Texas at Austin in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy The University of Texas at Austin December, 2009 To my grandfather, who made me an engineer before I knew the word and to my wife, Carey, for being my partner on my good days and bad. Acknowledgements I am extraordinarily fortunate in the support I have received on the path to this accomplishment. My adviser, Dr. Isaac Sanchez, has made this publication possible with his advice, support, and willingness to field my ideas at random times in the afternoon; he has my deep appreciation for his outstanding guidance. My thanks also go to the members of my Ph.D. committee for their valuable feedback in improving my research and exploring new directions. I am likewise grateful to the other members of Dr. Sanchez’ research group – Xiaoyan Wang, Yingying Jiang, Xiaochu Wang, and Frank Willmore – who have shared their ideas and provided valuable sounding boards for my mine. I would particularly like to express appreciation for Frank’s donation of his own post-graduation time in assisting my research.
    [Show full text]
  • Micelle Formation and the Hydrophobic Effect†
    6778 J. Phys. Chem. B 2004, 108, 6778-6781 Micelle Formation and the Hydrophobic Effect† Lutz Maibaum,‡ Aaron R. Dinner,§ and David Chandler*,‡ Department of Chemistry, UniVersity of California, Berkeley, California 94720, and Department of Chemistry, UniVersity of Chicago, Chicago, Illinois 60637 ReceiVed: NoVember 14, 2003; In Final Form: January 14, 2004 The tendency of amphiphilic molecules to form micelles in aqueous solution is a consequence of the hydrophobic effect. The fundamental difference between micelle assembly and macroscopic phase separation is the stoichiometric constraint that frustrates the demixing of polar and hydrophobic groups. We present a theory for micelle assembly that combines the account of this constraint with a description of the hydrophobic driving force. The latter arises from the length scale dependence of aqueous solvation. The theoretical predictions for temperature dependence and surfactant chain length dependence of critical micelle concentrations for nonionic surfactants agree favorably with experiment. I. Introduction in accord with experimental observations. An appendix is used to augment the discussion in section II. This paper concerns the formation of micelles, which are the simplest form of amphiphilic assemblies. Our treatment of this II. Theory phenomenon is based upon the length scale dependence of hydrophobic effects.1,2 Namely, the free energy to solvate small A. Law of Mass Action. We consider an aqueous solution hydrophobic molecules scales linearly with solute volume, of neutral amphiphilic molecules (i.e., nonionic surfactants), each whereas that to solvate large hydrophobic species scales linearly of which has a single alkyl chain as its hydrophobic tail. In with surface area. The crossover from one regime to the other general, amphiphiles can form aggregates of various sizes and occurs when the oily species presents a surface in water shapes.
    [Show full text]
  • Tutorial on Working with Micelles and Other Model Membranes
    Tutorial on Working with Micelles and Model Membranes Chuck Sanders Dept. of Biochemistry, Dept. of Medicine, and Center for Structural Biology Vanderbilt University School of Medicine. http://structbio.vanderbilt.edu/sanders/ March, 2017 There are two general classes of membrane proteins. This presentation is on working with integral MPs, which traditionally could be removed from the membrane only by dissolving the membrane with detergents or organic solvents. Multilamellar Vesicles: onion-like assemblies. Each layer is one bilayer. A thin layer of water separates each bilayer. MLVs are what form when lipid powders are dispersed in water. They form spontaneously. Cryo-EM Micrograph of a Multilamellar Vesicle (K. Mittendorf, C. Sanders, and M. Ohi) Unilamellar Multilamellar Vesicle Vesicle Advances in Anesthesia 32(1):133-147 · 2014 Energy from sonication, physical manipulation (such as extrusion by forcing MLV dispersions through filters with fixed pore sizes), or some other high energy mechanism is required to convert multilayered bilayer assemblies into unilamellar vesicles. If the MLVs contain a membrane protein then you should worry about whether the protein will survive these procedures in folded and functional form. Vesicles can also be prepared by dissolving lipids using detergents and then removing the detergent using BioBeads-SM dialysis, size exclusion chromatography or by diluting the solution to below the detergent’s critical micelle concentration. These are much gentler methods that a membrane protein may well survive with intact structure and function. From: Avanti Polar Lipids Catalog Bilayers can undergo phase transitions at a critical temperature, Tm. Native bilayers are usually in the fluid (liquid crystalline) phase.
    [Show full text]
  • (CCC)95-Hydrophile-Lipophile Balance (HLB) Relationship
    Minerals 2012, 2, 208-227; doi:10.3390/min2030208 OPEN ACCESS minerals ISSN 2075-163X www.mdpi.com/journal/minerals Article Characterizing Frothers through Critical Coalescence Concentration (CCC)95-Hydrophile-Lipophile Balance (HLB) Relationship Wei Zhang 1, Jan E. Nesset 2, Ramachandra Rao 1 and James A. Finch 1,* 1 Department of Mining and Materials Engineering, McGill University, 3610 Univeristy Street, Wong Building, Montreal, QC H3A 2B2, Canada; E-Mails: [email protected] (W.Z.); [email protected] (R.R.) 2 NesseTech Consulting Services Inc., 17-35 Sculler’s Way, St., Catharines, ON L2N 7S9, Canada; E-Mail: [email protected] * Author to whom correspondence should be addressed; E-Mail: [email protected]; Tel.: +01-514-398-1452; Fax: +01-514-398-4492. Received: 22 June 2012; in revised form: 26 July 2012 / Accepted: 31 July 2012 / Published: 13 August 2012 Abstract: Frothers are surfactants commonly used to reduce bubble size in mineral flotation. This paper describes a methodology to characterize frothers by relating impact on bubble size reduction represented by CCC (critical coalescence concentration) to frother structure represented by HLB (hydrophile-lipophile balance). Thirty-six surfactants were tested from three frother families: Aliphatic Alcohols, Polypropylene Glycol Alkyl Ethers and Polypropylene Glycols, covering a range in alkyl groups (represented by n, the number of carbon atoms) and number of Propylene Oxide groups (represented by m). The Sauter 3 mean size (D32) was derived from bubble size distribution measured in a 0.8 m mechanical flotation cell. The D32 vs. concentration data were fitted to a 3-parameter model to determine CCC95, the concentration giving 95% reduction in bubble size compared to water only.
    [Show full text]
  • Exercise and Cellular Respiration Lab
    California State University of Bakersfield, Department of Chemistry Exercise and Cellular Respiration Lab Standards: MS-LS1-7 Develop a model to describe how food is rearranged through chemical reactions forming new molecules that support growth and/or release energy as this matter moves through an organism. Introduction: I. Background Information. Cellular respiration (see chemical reaction below) is a chemical reaction that occurs in your cells to create energy; when you are exercising your muscle cells are creating ATP to contract. Cellular respiration requires oxygen (which is breathed in) and creates carbon dioxide (which is breathed out). This lab will address how exercise (increased muscle activity) affects the rate of cellular respiration. You will measure 3 different indicators of cellular respiration: breathing rate, heart rate, and carbon dioxide production. You will measure these indicators at rest (with no exercise) and after 1 and 2 minutes of exercise. Breathing rate is measured in breaths per minute, heart rate in beats per minute, and carbon dioxide in the time it takes bromothymol blue to change color. Carbon dioxide production can be measured by breathing through a straw into a solution of bromothymol blue (BTB). BTB is an acid indicator; when it reacts with acid it turns from blue to yellow. When carbon dioxide reacts with water, a weak acid (carbonic acid) is formed (see chemical reaction below). The more carbon dioxide you breathe into the BTB solution, the faster it will change color to yellow. The purpose of this lab activity is to analyze the effect of exercise on cellular respiration. Background: I.
    [Show full text]
  • Electrification at Water–Hydrophobe Interfaces
    Electrification at water–hydrophobe interfaces Item Type Article Authors Nauruzbayeva, Jamilya; Sun, Zhonghao; Gallo Junior, Adair; Ibrahim, Mahmoud; Santamarina, Carlos; Mishra, Himanshu Citation Nauruzbayeva, J., Sun, Z., Gallo, A., Ibrahim, M., Santamarina, J. C., & Mishra, H. (2020). Electrification at water–hydrophobe interfaces. Nature Communications, 11(1). doi:10.1038/ s41467-020-19054-8 Eprint version Publisher's Version/PDF DOI 10.1038/s41467-020-19054-8 Publisher Springer Nature Journal Nature Communications Rights This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. Download date 05/10/2021 16:06:59 Item License https://creativecommons.org/licenses/by/4.0 Link to Item http://hdl.handle.net/10754/665657 ARTICLE https://doi.org/10.1038/s41467-020-19054-8 OPEN Electrification at water–hydrophobe interfaces Jamilya Nauruzbayeva1,3, Zhonghao Sun 2,3, Adair Gallo Jr.1,3, Mahmoud Ibrahim1, J. Carlos Santamarina 2 & ✉ Himanshu Mishra 1 The mechanisms leading to the electrification of water when it comes in contact with hydrophobic surfaces remains a research frontier in chemical science.
    [Show full text]
  • Statistical Mechanics I: Exam Review 1 Solution
    8.333: Statistical Mechanics I Fall 2007 Test 1 Review Problems The first in-class test will take place on Wednesday 9/26/07 from 2:30 to 4:00 pm. There will be a recitation with test review on Friday 9/21/07. The test is ‘closed book,’ but if you wish you may bring a one-sided sheet of formulas. The test will be composed entirely from a subset of the following problems. Thus if you are familiar and comfortable with these problems, there will be no surprises! ******** You may find the following information helpful: Physical Constants 31 27 Electron mass me 9.1 10− kg Proton mass mp 1.7 10− kg ≈ × 19 ≈ × 34 1 Electron Charge e 1.6 10− C Planck’s const./2π ¯h 1.1 10− Js− ≈ × 8 1 ≈ × 8 2 4 Speed of light c 3.0 10 ms− Stefan’s const. σ 5.7 10− W m− K− ≈ × 23 1 ≈ × 23 1 Boltzmann’s const. k 1.4 10− JK− Avogadro’s number N 6.0 10 mol− B ≈ × 0 ≈ × Conversion Factors 5 2 10 4 1atm 1.0 10 Nm− 1A˚ 10− m 1eV 1.1 10 K ≡ × ≡ ≡ × Thermodynamics dE = T dS+dW¯ For a gas: dW¯ = P dV For a wire: dW¯ = Jdx − Mathematical Formulas √π ∞ n αx n! 1 0 dx x e− = αn+1 2 ! = 2 R 2 2 2 ∞ x √ 2 σ k dx exp ikx 2σ2 = 2πσ exp 2 limN ln N! = N ln N N −∞ − − − →∞ − h i h i R n n ikx ( ik) n ikx ( ik) n e− = ∞ − x ln e− = ∞ − x n=0 n! � � n=1 n! � �c P 2 4 P 3 5 cosh(x) = 1 + x + x + sinh(x) = x + x + x + 2! 4! · · · 3! 5! · · · 2πd/2 Surface area of a unit sphere in d dimensions Sd = (d/2 1)! − 1 1.
    [Show full text]