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Chemical and Biochemical Measurements with Nanoelectrodes

Explore the use of nanoelectrodes in chemical and biochemical measurements, including neurotransmitter detection and dopamine detection. Learn about important units of measurement, SI units, prefixes, and conversion factors. Understand the concepts of molarity, molality, percent concentration, and stoichiometry calculations. Discover the principles of gravimetric analysis and titrations. This website provides comprehensive information and explanations for these topics.

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Chemical and Biochemical Measurements with Nanoelectrodes

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  1. Website Ex) http://chemlab.pusan.ac.kr/echem/

  2. Chapter 1 Chemical Measurements

  3. Biochemical Measurements with a Nanoelectrode. Neurotransmitter detection (in vitro & in vivo) Carbon fiber electrode (dia.=100 nm) Dopamine detection

  4. Some important units of measurement 1-1.SI units(Le Système International d'Unités): • International System of Units • 1960’11th(CGPM, Conférence Générale des Poids et Mesures) -> "SI＂ • Fundamental SI unit: 7

  5. Using prefixes as multipliers *** Rather than using exponential notation, we often use prefixes from Table 1-3 to express large or small quantities. Examples: 1.7 x 104 m x 1km/103 m = 17 km 0.019Pa x 1mPa/10-3 Pa =19mPa

  6. Converting between units *** Although SI is the internationally accepted system of measurement in science, other units are encountered. Useful conversion factors are found in table 1-4.

  7. nx: number of mol ofx, Mx: mole mass(g/mol) of x massx: mass(g) of x 1-2. chemical concentrations Solution: a homogeneous mixture of two or more substance; it composedof Solute ( a minor species) and Solvent ( the major species) Def:The mole is the amount of substance of a system which contains as many elementary entities as there are atoms in 0.012 kilogram of carbon 12; its symbol is "mol.“ ▶mol : Avogadro number of particles. Molarity (M): the number of moles of a substance per liter of solution. ▶(6.022 Х 1023 ) :1mol ▶(molar mass, M),1mol mass( g)

  8. Ex) Molecular mass(M): The sum of atomic mass. Formaldehyde(CH2O) andglucose(C6H12O6)moles?

  9. ■ Analytical molarity (mol/L) Formal concentration (F) = (mass/ formula mass) /L Ex) In case of electrolyte (strong & weak electrolytes) ■ Equilibrium molarity (mol/L)

  10. solute(mol) (☞ M = mol/L = mmol/mL) Molarity (M) = solution(L) mol mol = MV M= V solute(mol) Formal concentration (F) = solution(L) solute(mol) - Formula mass (FM): molecular mass of a strong electrolyte ☞F : Molarity of strong electrolyte for the original chemical formula in solution (independent of T) Molality (m) = solvent(Kg) Example Molarity of Salts in the Sea (a) Sea water contains 2.7 g of NaCl per 100 mL (0.1 L) → molarity(M)?(b) 0.054 M MgCl2 → g of MgCl2 in 25 mL? Solution (a) Molar mass of NaCl = 22.99 g/mol Moles of NaCl = 2.7/22.99 = 0.046 mol ∴ Molarity (M) = 0.046 mol/ 0.1 L = 0.46 M (b) Molar mass of MgCl2 = 95.20 g/mol x g/95.20 gmol-1 mol ∴ x = 0.13 g = 0.054 M = M= 0.025 L V

  11. Weak electrolyte Equilibrium is dependent on the temperature. * Molality (m) is concentration expressed as moles of substance per kilogram of solvent.

  12. Solution = solute + solvent Percent concentration (%)

  13. solute solution solute solution μg L μg mL mg L ng mL Parts per Million and Parts per Billion 1 g of water equates with 1 ml of water approximately. ( 1 ppm = 1 μg/mL) ×106 ppm = ppm for aqueous solution: = ×109 ppb = ppb for aqueous solution: =

  14. 1-3preparing solutions To prepare a solution with a desired molarity from a pure solid or liquid, we weigh out the correct mass of reagent and dissolve it in a volumetric flask.

  15. Solution-diluent volume ratios 진한용액의 부피 : 묽히는 용액의 부피 = A : B ⇒1 : 4 HCl 용액 = 진한 HCl 부피 1 + 4 부피의 물 p-function

  16. Check the density of commercial reagents in liquid.

  17. Stoichiometry is the calculation of quantities of substances involved in a chemical reaction

  18. 1-4 Stoichiometry calculations for Analysis Chemical analysis based on weighing a final product is called gravimetric analysis. Experimental procedure: Step 1: Preparation of sample solution. Step 2: Chemical reaction to a species. Step 3: Convert the species to stable final product.

  19. Ex) Iron measurement in tablet by gravimetric analysis Step 1. Dissolve the Fe2+ with HCl Step 2. Oxidation of Fe2+ to Fe3+ with H2O2 2Fe2++ H2O2 + 2H+ → 2Fe3++ 2H2O (1-5) Step 3. Precipitate hydrous iron(III) oxide with NH4OH filter and ignite to convert it to pure solid Fe2O3 Fe3++ 3OH- +(x-1)H2O →FeOOH ㆍ xH2O(s) →Fe2O3 (1-6) Sample(tablet) 900℃ Step 1,2,3 Fe2+C4H2O42- + inert binder Fe2O3 (Mass ? ) 1Fe 2Fe g of Fe in tablet?

  20. 1-5. Introduction to titrations Procedures in which we measure the volume of reagent needed to react with analyte (the sub-stance being measured) are called volumetric analysis. titration, titrant (reagent solution), equivalent point, end point indicator, titration error, blank titration, primary standard, standardization standard solution, direct titration, back titration Gravimetric titration

  21. O O Ex) Titration of Oxalic acid with KMnO4 = = 5HO–C–C–OH (1-7) + 2MnO4-+ 6H+ → 10CO2 + 2Mn2+ + 8H2O (colorless) (colorless) Titrant (purple) Analyte Oxalic acid (colorless) ⇒ Equivalence point: occurs when 2 moles of MnO4- is added to 5 moles of oxalic acid ⇒ End point: appearance of the first trace of purple color of MnO4- • Titration error • The difference between the end point of a titration and the equivalence point of it. • The end-point may be slightly different from the true equivalence point. • Blank titration • The same titration procedure without analyte • Can estimate and reduce the titration error • Procedure for correction of titration error by a blank titration • i) repeat titration procedure without analyte • ii) determine amount of titrant needed to observe change • iii) subtract blank volume from titration

  22. Primary standard BOX 1-1 Reagent Chemicals and Primary Standards • Grade of Chemicals - Reagent-grade chemicals meeting purity requirements set by the American Chemical Society(ACS) Committee on Analytical Reagents. - Primary standard grade. - Trace analysis (analysis of species at ppm and lower levels): impurities in reagent chemicals must be extremely low. • Standardization • the process of determining the exact concentration of a solution. • Standard solution • - a solution of known concentration (molarity) • - use as a titrant • Direct titration: add titrant to analyte until the reaction is complete • Back titration: add a known excess of one standard reagent to the analyte

  23. 1-6 Titration Calculations Primary standard Standard solution H2C2O4 (Na2C2O4) (KMnO4) In stoichiometry calculations in volumetric analysis, the key step is to relate moles of tyrant to moles of analyte. Standardization Titration

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