NRAN 80323 Mixtures and Solutions.pptx

Mixtures and Solutions NRAN 80323 Casey Crow DNP, CRNA Objectives • Mixtures • Solutions • Ionized Solutions • pKA • Solubility • Henry’s Law • Coefficients Mixtures Solution Solutions • Homogeneous mixture that consists of one or more solutes uniformly dispersed at the molecular or ionic l...

Mixtures and Solutions NRAN 80323 Casey Crow DNP, CRNA Objectives • Mixtures • Solutions • Ionized Solutions • pKA • Solubility • Henry’s Law • Coefficients Mixtures Solution Solutions • Homogeneous mixture that consists of one or more solutes uniformly dispersed at the molecular or ionic level throughout the medium known as the solvent SOLUTE SOLVENT Material which is dissolved Material in which something is dissolved Solutions • Molarity (M): Molar concentration, moles of solute per liter of solution • Solute per VOLUME • Molality (m): Molal concentration, moles of solute per kilogram of solution • Solute per MASS M = m = • Molarity can never equal molality, but the differences become smaller as the solutions become more dilute • Mole (mol): Molar weight, gram molecular weight of a substance • Millimole (mmol): milligram molecular weight Solutions Anytime in pharmacology, when a drug is expressed as percent by weight volume, it’s always grams/100 ml • Percent by weight to volume • (% w/v): grams of solute per 100 ml of solution % w/v= 2% = 2 g / 100 ml 2% = 2000 mg / 100 ml 2% = 20 mg/ml 0.5% = 0.5 g / 100 ml 0.5% = 500 mg / 100 ml 0.5% = 5 mg/ml Solutions Remember: 1 gram of solute per mls of solution Grams is always on the Left, mls of solution is always on the Right • Ratio Weight (Mass): grams of solute : ml of solution 1 g / 100,000 ml 1000 mg / 100,000 ml 1 mg / 100 ml 1000 mcg / 100 ml 10 mcg/ml 1 g / 200,000 ml 1000 mg / 200,000 ml 1 mg / 200 ml 1000 mcg / 200 ml Solutions • Equivalent Weight (Eq): gram weight (mass) of a substance that will combine or replace 1 g of hydrogen • Molar weight divided by ionic valence (charge number) • Milliequivalent (mEq): 1/1000 of an equivalent • How many mg of Ca++ are in one mEq? Colloids • Large molecules balanced between precipitation (settling) by gravity and suspension (floating) by intermolecular forces • Particles cannot be filtered out and do not settle out • Not true solutions: can differentiate and Explanation: To keep distinguish microparticles from settling • Dispersed particles are larger thanand suspending, these larger molecules and the molecules/atoms/ions intermolecular forces between them, (how they are attracted to each other) is what keeps them balanced Ionic Solutions • Solutions of atoms and or molecules in the ionized form • Salt (NaCl) molecule is dissociated into ionic atoms NaCl in water Na+ + Cl- NaCl in water NaCl in water is int its IONIZED State + Na + Cl Na becomes ionically (+) charged and the chloride becomes ionically (-) charged Na gives up the electron, Cl takes an electron Dissociation Constant (pKa): pH of solvent at which 50% of solute is ionized and 50% of How the reaction causes the drug to move or not move throughout the physiologic solute is non-ionized compartments of the body Ionic Solutions Gases in Solution Pa ? How does gas that we breathe in, get into our blood? O2, CO2, VA How is it dissolved into our blood? mmH g? Gases in Solution • Pressure can only be measured in GAS phase • Measured as a CONCENTRATION in a solution • Partial Pressure • Partial pressure of a gas in solution refers to the pressure of the gas in the gas phases at equilibrium with the liquid (solution) • Reflects “FORCE TO Indirect measurement: 1. Oxygen is dissolved in blood 2. Above the air fluid interface, when comes to equilibrium, can measure how much is in the fluid based on Gases in Solution • Inhaled anesthetics equilibrate based on partial pressures in each tissue compartment, not concentration • Concentration of anesthetic in a tissue depends on its partial pressure and the tissue solubility of the anesthetic Gases in Solution Henry’s Law defines solubility • Henry’s Law: the amount of gas that dissolves in a liquid, or the solubility of that gas, is DIRECTLY PROPORTIONAL to the PARTIAL PRESSURE of the gas above the liquid and INVERSLEY PROPORTIONAL to TEMPERATURE P = k(C) C P = partial pressure k = constant (r/t temperature) C = concentration of dissolved gas (expressed in MOLARITY PARTIAL PRESSURE TEMPERATURE = = P/k CONCENTRATION [mol/L]) PARTIAL PRESSURE TEMPERATURE = More oxygen in gas above blood, increases PP The amount in the blood will increase too P= • “Overpressurizing” volatile k(C) Gases in Solution anesthetics Increasing FAagent will increase concentration of agent in blood, speed tissue uptake Solubility • The tendency of a gas (gas phase) to equilibrate with solution (liquid phase)- how fast/easily gas infused into a liquid equilibrates • Measure of how much SOLUTE (gas) can dissolve in a given amount of SOLUTION (liquid) Bunsen Coefficient Unit (SI) volume of gas dissolved in a given, unit volume of liquid at STP Ostwald Coefficient Volume of gas dissolved in a given volume of liquid at a specific temperature Partition Coefficient Ratio of the amount of substance present in equal volumes of two phases at a stated temperature Blood:gas Partition Coefficient Blood:gas Partition Coefficient Sevo 0.65 Every 1 mole in alveolus (gas phase), there are 0.65 moles in the blood Halo 2.5 Every 1 mole in alveolus (gas phase), there are 2.5 moles in the blood Which is more soluble? Blood:gas Partition Coefficient Halo 2.5 Every 1 mole in alveolus (gas phase), there are 2.5 moles in the blood More Potent: MAC Sevo 0.65 Every 1 mole in alveolus (gas phase), there are 0.65 moles in the blood Less Potent: MAC Blood:gas Partition Coefficient HIGHER BLOOD:GAS PARTITION COEFFICIENT HIGHER LIPOPHILICITY HIGHER POTENCY HIGHER SOLUBILITY LARGER PHYSIOLOGIC “CONTAINER” SLOWER ONSET Blood:gas Partition Coefficient Blood compartment is bigger for Halo: more soluble, blood can hold more VA The Blood:gas Partition Coefficient is what defines the size of the physiologic container of blood Blood compartment is smaller for Sevo: less soluble, blood can’t hold as much VA The blood fills up more quickly because the container is smaller The Blood:gas Partition Coefficient also defines how quickly the anesthetic comes on and off Mastery: Formulas for%w/v • Define solute, solvent, solution Ratio weight • Differentiate molarity from molality Equivalent weight • Define and calculate percent by weight to volume of solution Blood:gas partition • Define and calculate ratio weight of solution coefficients • What is and equivalent and how is it calculated? Summary • What are the physical properties of a colloid? • What is an ionic solution? • What are the pharmacologic implications of ionic solutions? • Describe the relationship of partial pressure, temperature, and solubility related to gas solubility • Differentiate Bunsen, Otswald, and partition coefficients • Memorize the blood;gas partition coefficients of modern inhaled anesthetics • Describe how blood:gas partition coefficients affect pharmacokinetics of inhaled anesthetics References Shubert / Chapter 8 / 211239 Nagelhout / Chapter 15