Verify Beer-Lambert's law and determine the molar absorption coefficient (ε = 11,100 L·mol⁻¹·cm⁻¹), limit of detection (LOD = 0.54 μM), and limit of quantitation (LOQ = 1.62 μM) of the tris(1,10-phenanthroline)iron(II) complex ([Fe(phen)₃]²⁺) at 510.0 nm across concentrations from 10.0 to 80.0 μM at 25.0 °C. Explore interactive analytical gravimetry, Class A volumetric glassware and density determination.
Ready to dispense 50.0 μM of liquid.
Adjust c(Fe²⁺) V, then weigh the dispensed aliquot.
Mass observations are determined by the high-precision thermodynamic equation of state for pure liquid water. Readings reflect thermal equilibrium and analytical balance force restoration.
["Beer-Lambert's law applies strictly to monochromatic radiation and non-interacting chromophores at concentrations below 0.01 M.", 'Stray radiant energy and detector noise cap the linear dynamic range at absorbances above 1.5 AU.', 'Presence of strong competing ligands (such as EDTA, oxalate, or fluoride) can sequester iron and suppress complex formation.'] The quantitative model evaluates the [Fe(phen)₃]²⁺ complex at λ = 510.0 nm across six calibration concentrations from 10.0 to 80.0 μM in a matched 1.000 cm cuvette at 25.00 °C. The measured absorbances are [0.111, 0.222, 0.389, 0.555, 0.722, 0.888] AU. Ordinary least-squares regression yields an empirical slope m = 0.011102 AU/μM and Y-intercept b = 0.000086 AU with an exceptional coefficient of determination R² = 0.9999993. The extracted molar absorption coefficient is ε = 11,102 L·mol⁻¹·cm⁻¹ (0.0168% difference from the authoritative reference standard 11,100 L·mol⁻¹·cm⁻¹). Replicate blank measurements (s_blank = 0.0018 AU) establish an experimental Limit of Detection LOD = 0.54 μM (0.030 mg/L Fe) and Limit of Quantitation LOQ = 1.62 μM (0.091 mg/L Fe), confirming ideal adherence to Beer-Lambert's law.
High-precision split-beam optical spectrophotometer with deuterium/tungsten lamp sources, holographic grating monochromator, and matched photodiode detectors for measuring absorbance (A = -log₁₀ T) with photometric accuracy ±0.002 AU.
Certified optical transmission matched cuvettes with internal path length b = 10.00 ± 0.01 mm, cleaned with spectroscopic ethanol and optical lens wipes.
Calibrated P1000 and P100 micropipettes (ISO 8655 certified, accuracy ±0.5%) for dispensing micro-aliquots of standard iron(II) stock solution.
Certified Class A borosilicate volumetric flasks (tolerance ±0.05 mL) used for serial dilution of calibration standards.
Circulating constant-temperature water bath with external jacket maintaining the cuvette chamber at 25.00 ± 0.02 °C.
Electromagnetic force restoration balance (readability ±0.0001 g) used to weigh primary standard ferrous ammonium sulfate hexahydrate (Mohr's salt, Fe(NH₄)₂(SO₄)₂·6H₂O).
Verify Beer-Lambert's law and determine the molar absorption coefficient (ε = 11,100 L·mol⁻¹·cm⁻¹), limit of detection (LOD = 0.54 μM), and limit of quantitation (LOQ = 1.62 μM) of the tris(1,10-phenanthroline)iron(II) complex ([Fe(phen)₃]²⁺) at 510.0 nm across concentrations from 10.0 to 80.0 μM at 25.0 °C. Suggested independent volumetric settings: 10.0, 20.0, 35.0, 50.0, 65.0, 80.0 μM.
Accurately weigh 0.0702 g of primary standard ferrous ammonium sulfate hexahydrate (Fe(NH₄)₂(SO₄)₂·6H₂O, M = 392.14 g/mol) on the analytical balance. Dissolve in 50 mL deionized water containing 2.0 mL concentrated sulfuric acid, quantitatively transfer to a 500.00 mL volumetric flask, and dilute to the mark with deionized water to establish a 3.580 × 10⁻⁴ M (20.00 ppm Fe) stock solution.
Pipette aliquots of iron stock solution into a series of six 50.00 mL volumetric flasks to achieve final concentrations of 10.0, 20.0, 35.0, 50.0, 65.0, and 80.0 μM. To each flask, add 1.0 mL of 10% w/v hydroxylamine hydrochloride (to reduce any trace Fe³⁺ to Fe²⁺), 5.0 mL of 1.0 M sodium acetate buffer (pH 4.5), and 5.0 mL of 0.25% w/v 1,10-phenanthroline monohydrate solution.
Dilute each volumetric flask to the 50.00 mL calibration mark with deionized water, invert twenty times to homogenize, and allow the intense orange-red ferroin complex ([Fe(phen)₃]²⁺) to develop fully at 25.00 °C for 15 minutes. Prepare a reagent blank containing all reagents except the iron standard.
Turn on the dual-beam spectrophotometer and allow 30 minutes for thermal lamp stabilization. Set the monochromator to 510.0 nm with a 1.0 nm spectral slit width. Fill both matched cuvettes with deionized water and execute a zero-transmittance and 100% transmittance baseline calibration.
Rinse the sample cuvette twice with the test solution, fill to 80% capacity, wipe exterior optical windows with lens paper, and seat in the sample cell holder against the reagent blank in the reference beam. Measure and record the steady-state absorbance A₅₁₀ to three decimal places for each standard in ascending concentration order.
Plot absorbance A₅₁₀ versus iron concentration c (μM). Perform ordinary least-squares regression to determine the calibration slope m = ε·b and verify compliance with Beer's law (R² ≥ 0.999). Evaluate the standard deviation of blank measurements (s_blank) and compute the Limit of Detection (LOD = 3.3 · s_blank / m) and Limit of Quantitation (LOQ = 10 · s_blank / m).
Points are your recorded gravimetric observations. The regression line validates the linear mass-volume proportionality and extracts density.
| # | Iron(II)-Phenanthroline Concentration c (μM) | Absorbance at 510 nm (A₅₁₀) (AU) | Complex Concentration c (μM) | Absorbance A₅₁₀ (AU) | Remove |
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