Introduction to Laboratory Analysis

Introduction to Laboratory Analysis

• This lecture introduces principles of laboratory analysis, focusing on solute and solvent concepts.
• Clinical lab analyses frequently determine the concentration of substances in solutions.
• Common solution samples include blood, serum, urine, and spinal fluid.

Concept of Solute and Solvent

• A solution is a homogeneous mixture of one or more solutes dispersed in a solvent.
• In lab practice, solutes are often measured and referred to as analytes.

Expressing Concentrations of Solutions

• Various units quantify solute concentration in solutions.
  • Substance concentration: Amount of solute per volume of solution (mol/m³ or mol/L)
  • Molality: Amount of solute per mass of solvent (mol/kg)
  • Mole fraction: Amount of one substance relative to the total amount of all substances in the mixture (mol/mol)
  • Mole ratio: Amount of solute relative to the amount of the solvent (mol/mol)
  • Mass concentration: Mass of solute per unit volume of solution (kg/m³ or kg/L)
  • Mass fraction: Mass of solute relative to the total mass of the solution (kg/kg)
  • Volume fraction: Volume of solute relative to the total volume of the solution (m³/m³ or L/L)
  • Number concentration: Number of particles per unit volume of solution (m³⁻¹ or L⁻¹)
  • Number fraction: Number of particles of one kind relative to the total number of particles in the solution (no unit)
  • Substance content: Amount of substance of a component relative to the mass of the solution (mol/kg)

Equations for Expression of Concentration

• Molarity (M): Moles of solute per liter of solution.

  • Formula: M = n solute / V solution
    • M = molarity (mol/L)
    • n solute = moles of solute (mol)
    • V solution = volume of solution (L)

• Molality (m): Moles of solute per kilogram of solvent.

  • Formula: m = n solute / m solvent
    • m = molality (mol/kg)
    • n solute = moles of solute (mol)
    • m solvent = mass of solvent (kg)

• Mass percent (w/w%): Mass of solute divided by the total mass of solution, multiplied by 100.

  • Formula: Mass Percent = (m solute / m solution) x 100
    • m solute = mass of solute (g)
    • m solution = mass of solution (g)

• Volume percent (v/v%): Volume of solute divided by the total volume of solution, multiplied by 100.

  • Formula: Volume Percent = (V solute / V solution) x 100
    • V solute = volume of solute (mL or L)
    • V solution = total volume of solution (mL or L)

• Mole fraction (X): Ratio of moles of one component to the total number of moles in the mixture.

  • Formula: X_A = n_A / (n_A + n_B)
    • X_A = mole fraction of component A
    • n_A = moles of component A
    • n_B = moles of component B

• Normality (N): Number of equivalents of solute per liter of solution

  • Formula: N = equivalents of solute / V solution
    • N = normality (eq/L)
    • V solution = volume of solution (L)

Reference Material

• Reference standard materials are highly purified compounds with well-defined characteristics.
• The quality of these materials is essential for obtaining accurate analytical results in pharmaceutical and other analytical methods.

Basic Techniques and Procedures

• Spectroscopy techniques including UV-VIS, mass spectrometry, atomic absorption, fluorescence, FT-IR, X-ray diffraction, atomic emission, and ICPOES.
• Separations methods like electrophoresis and chromatography (GC, HPLC)
• Microscopy techniques, such as scanning electron microscopy and transmission electron microscopy.
• Thermal analysis methods involving thermogravimetry analysis and bomb calorimetry.
• Electrochemical analysis methods, including coulometry, potentiometry, polarography, voltammetry, conductimetry, and amperometry.

Qualitative vs Quantitative Analysis

• Qualitative analysis identifies substances, while quantitative analysis determines the amount.

Comparison of Quantitative and Qualitative Analysis

• Quantitative analysis uses numerical data, while qualitative analysis uses non-numerical data like text or images.
• Quantitative analysis is objective, minimizing subjectivity, while qualitative analysis embraces subjectivity and explores understanding.
• Quantitative research aims for hypothesis testing and prediction, while qualitative research aims for exploratory understanding and context.