Flashcards on Biochemistry and Analytical Chemistry Calculations
Biochemistry & Analytical Chemistry Calculations: Oxidative Stress
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Analytical Chemistry Calculations
16 cards
Card 1
Question: How do you calculate the molar absorption coefficient (ε) from measured absorbance using Beer–Lambert law?
Answer: Use A = ε · c · d, so ε = A / (c · d). (Where A = absorbance, c = concentration, d = path length.)
Card 2
Question: Given 0.35 mL of a 1 mmol·L⁻¹ cytochrome c solution diluted to a total volume with 4.65 mL water, what is the resulting concentration used in Beer–Lam
Answer: Final volume = 0.35 + 4.65 = 5.00 mL. c = (0.35 mL / 5.00 mL) · 1 mmol·L⁻¹ = 0.07 mmol·L⁻¹ = 7·10⁻⁵ mol·L⁻¹.
Card 3
Question: Using A₅₅₀ = 0.56, path length d = 0.5 cm, and concentration c = 7·10⁻⁵ mol·L⁻¹, how is ε calculated and what is its value?
Answer: ε = A / (c·d) = 0.56 / (7·10⁻⁵ · 0.5) = 0.56 / 3.5·10⁻⁵ = 16000 L·mol⁻¹·cm⁻¹.
Card 4
Question: How do you find unknown concentration from absorbance when sample and standard are measured with the same volumes and path length?
Answer: Use proportionality A_sample / A_standard = c_sample / c_standard, so c_sample = c_standard · (A_sample / A_standard).
Card 5
Question: If a glucose standard 20 mmol·L⁻¹ gives A₄₉₈ = 0.16 and a sample gives A₄₉₈ = 0.05 with same volumes, what's the sample concentration?
Answer: c_sample = 20 mmol·L⁻¹ · (0.05 / 0.16) = 6.25 mmol·L⁻¹.
Card 6
Question: How do you account for dilution when calculating analyte concentration in an original (undiluted) sample?
Answer: Multiply the concentration measured in the diluted aliquot by the dilution factor (original volume / aliquot volume or by the dilution ratio).
Card 7
Question: A urine sample was diluted 100×; diluted sample concentration calculated as 541.7 mmol·L⁻¹ from absorbances. How do you get the concentration in undil
Answer: Undiluted concentration = 541.7 mmol·L⁻¹ · 100 = 54,170 mmol·L⁻¹? (Note: according to provided final answers, c = 541.7 mmol·L⁻¹ is the undiluted conc
Card 8
Question: How do you calculate concentration from absorbance when given molar absorptivity and path length (example: bilirubin)?
Answer: Use c = A / (ε · d). For A₄₅₃ = 0.01, ε = 6.0×10⁴ L·mol⁻¹·cm⁻¹, d = 1 cm, c_reaction = 1.67 μmol·L⁻¹ for the serum aliquot accounting for dilution.
Card 9
Question: How do you compute mass of solute in a given mass of solution using mass percent w?
Answer: m_solute = w · m_solution. Example: m_NaCl = 0.5% · 500 g = 2.5 g.
Card 10
Question: How do you compute mass percent w when you dissolve solute mass into solvent mass?
Answer: w (%) = (m_solute / total mass) · 100. Example: 0.5 g glucose in 4.5 g water → total 5.0 g → w = (0.5/5.0)·100 = 10%.