Calculator Inputs
Use one calculation mode at a time. Replicate absorbance values override the single absorbance input when supplied.
Example Data Table
| Sample | Wavelength (nm) | A1 | A2 | A3 | Mean A | Blank | Corrected A | ε | Path (cm) | Estimated c (mol/L) |
|---|---|---|---|---|---|---|---|---|---|---|
| Standard 1 | 540 | 0.182 | 0.184 | 0.181 | 0.1823 | 0.010 | 0.1723 | 12500 | 1.00 | 1.378E-5 |
| Sample A | 540 | 0.628 | 0.634 | 0.636 | 0.6327 | 0.012 | 0.6207 | 12500 | 1.00 | 4.966E-5 |
| Sample B | 600 | 0.412 | 0.409 | 0.415 | 0.4120 | 0.008 | 0.4040 | 9800 | 1.00 | 4.122E-5 |
Formula Used
Beer-Lambert law: A = εlc, where absorbance equals molar absorptivity multiplied by path length and concentration.
Concentration from absorbance: c = Acorrected / (ε × l).
Blank correction: Acorrected = Asample - Ablank.
Absorbance from transmittance: A = -log10(T) or A = 2 - log10(%T).
Transmittance from absorbance: %T = 100 × 10-A.
Molar absorptivity: ε = Acorrected / (c × l).
Path length: l = Acorrected / (ε × c).
Calibration curve: c = (Acorrected - b) / m, where m is slope and b is intercept.
Replicate precision: Mean absorbance, standard deviation, and relative standard deviation support repeatability checks.
How to Use This Calculator
- Select the calculation mode that matches your laboratory task.
- Enter the sample name and wavelength for easier report tracking.
- Provide either one absorbance value or several replicate absorbance readings.
- Add blank absorbance, dilution factor, and reference constants when needed.
- Use calibration slope and intercept only for calibration curve mode.
- Click Calculate to show the result above the form.
- Review replicate precision, interpretation notes, and any warning messages.
- Use the CSV or PDF buttons to save the generated report.
FAQs
1. What does this calculator solve?
It converts absorbance and transmittance, estimates concentration, determines molar absorptivity, calculates path length, and handles straight-line calibration calculations with blank correction.
2. Why use blank correction?
Blank correction removes signal caused by solvent, reagent background, and cuvette effects. It improves accuracy before concentration or calibration estimates are reported.
3. When should I enter replicate absorbance values?
Enter replicates whenever you measured the same sample several times. The calculator averages them and reports standard deviation and relative standard deviation for quality control.
4. What is molar absorptivity?
Molar absorptivity describes how strongly a species absorbs light at a chosen wavelength. It depends on wavelength, solvent conditions, and chemical form.
5. Why is my calculated concentration negative?
A negative result usually means the blank was too large, the calibration intercept was unsuitable, or the measurement sits outside the valid calibration range.
6. What concentration unit should I use?
Use the same unit that matches your calibration data or laboratory standard. Common choices include mol/L, mmol/L, mg/L, and µg/mL.
7. Does dilution factor change the measured result?
Yes. The instrument measures the diluted sample. The calculator multiplies measured concentration by the dilution factor to estimate original sample concentration.
8. Can I use this for calibration-curve workflows?
Yes. Choose calibration mode, enter corrected absorbance inputs, then provide slope and intercept from your standard curve equation.