(E)Gasboard turns GC or headspace measurements into gas amounts in closed incubations. It also corrects repeated sampling, calculates gas dosing, fits time-series rates and lets you explore whether gas transfer could limit a process.
Pressure, temperature, bottle volumes and gas solubility are included, with optional salinity and pH-dependent CO₂/H₂S speciation. See how the calculations work →
What this tool does
Convert GC or headspace measurements to headspace, dissolved and total bottle amounts.
Calculate gas additions for dissolved or equilibrated headspace targets.
Fit time-series rates and screen whether gas transfer could support them.
Batch analysis
Upload measurements and calibration data as .xlsx, .csv or .tsv. One row is one bottle and time point; recognized gas columns are read automatically.
Input format & example columns
Measurement input
| experiment_id | sample_id | time_h | pressure_bar_abs | temperature_C | bottle_volume_mL | liquid_volume_mL | liquid_sample_mL | headspace_sample_mL | salinity_g_L_NaCl | pH | CO | CO2 | CH4 | O2 | H2S | N2O | NO | N2 | C2H6 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| WK3_example | 1_CO | 3.6333 | 1.58325 | 23 | 120 | 39.56 | 0.50 | 0.10 | 0 | 7.27 | 829.056 | 274.38 | 2.40 | ||||||
| WK3_example | 1_CO | 16.1667 | 1.54525 | 23 | 120 | 39.06 | 1.50 | 0.10 | 0 | 7.27 | 408.20 | 455.30 | 7.50 |
Recognized gas columns: CO, CO2, CH4, O2, H2S, N2O, NO, N2 and C2H6.
liquid_sample_mL and headspace_sample_mL are optional and describe volumes removed after the measurement on that row.
Calibration input
| gas_id | calibration_id | gas_percent | peak_area |
|---|---|---|---|
| CO | CO_0.935_rep1 | 0.93541 | 100.6 |
| CO | CO_4.516_rep1 | 4.51637 | 530.0 |
Results
Time series? Fit a rate from any selected interval and optionally screen gas transfer.
Saved analyses are added to the Rates_mass_transfer sheet in the download.
Calibration curve
Gas amount
Calculated data
Single calculation
Gas dosing
Calculate how much gas to add for either a dissolved target or an equilibrated headspace target. Headspace concentrations can be entered as % or ppmv.
Concentration is entered per litre; the dissolved amount is automatically scaled to the entered liquid volume.
Rate & mass transfer
Analyze fits a Batch interval or uses a manual rate. Explore & predict lets you change bottle conditions and see the transfer screen update live. In Analyze mode, choose the rate source below; mass-transfer screening is optional.
Rate
Bottle & transfer settings
Bottle
Gas properties
Mass transfer
How (E)Gasboard works
This page shows the equations and assumptions behind Batch analysis, Single calculation, Gas dosing and the rate/mass-transfer screen. The calculations are kept visible so results can be checked and reproduced.
Res ipsa loquitur.
Parameters & units reference
| Parameter | Symbol | Meaning |
|---|---|---|
| GC peak area | A | Instrument response measured for a standard or sample |
| Calibration slope | m | Change in GC peak area per unit gas concentration |
| Calibration intercept | b | Predicted GC peak area at 0% gas |
| Gas concentration | x | Percentage of the headspace made up by the selected gas |
| Gas fraction | yi | Gas concentration expressed as a fraction from 0 to 1 |
| Absolute pressure | Pabs | Total pressure in the bottle |
| Partial pressure | pi | Pressure contributed by the selected gas |
| Bottle volume | Vbottle | Total internal bottle volume |
| Liquid volume | Vliquid | Volume occupied by liquid |
| Headspace volume | Vheadspace | Gas-filled bottle volume |
| Liquid sample volume | Vsample,liquid | Optional liquid volume removed after a time-point measurement |
| Headspace sample volume | Vsample,gas | Optional headspace gas volume removed after a time-point measurement |
| Sampled amount | nsample | Amount of a gas physically removed in a gas and/or liquid sample |
| Cumulative sampled amount | Nsample,<i | Total amount removed during sampling before the current time point |
| Sampling-corrected amount | ncorrected | Current bottle amount plus material removed during previous sampling events |
| Temperature | T | Bottle temperature when pressure and gas composition apply |
| Compressibility factor | Z | Fixed at 1 in v0.2 |
| Gas constant | R | 8.314462618 J mol-1 K-1 |
| Henry solubility | Hscp | Dissolved concentration per gas partial pressure at the sample temperature |
| Reference Henry solubility | Hscp,* | Henry solubility at 298.15 K; * denotes the reference state |
| Henry temperature coefficient | B | Temperature-dependence coefficient used to correct Henry solubility; units K |
| Dissolved concentration | c | Dissolved concentration of the selected gas |
| Salting-out coefficient | Ks | Gas-specific coefficient used in the NaCl-equivalent salting-out correction |
| NaCl-equivalent concentration | cNaCl | NaCl-equivalent salt concentration used for the salting-out correction |
| Gas amount | n | Amount of gas; results are reported in mmol |
Internal calculation units are Pa, m³, K and mol.
1. GC peak area to gas concentration
For a multipoint calibration, every calibration observation is retained, including replicates. A straight line is fitted:
The sample gas concentration is then:
The calibration summary reports slope, intercept, R², number of observations and calibration range. Samples outside that range are still calculated but are flagged as extrapolations.
For a multipoint calibration, the normal model includes an intercept. If that unconstrained fit would give a negative intercept - and therefore a physically impossible negative predicted peak area at 0% gas - the intercept is constrained to 0 and the slope is refitted by least squares through the origin.
With only one non-zero standard, a proportional calibration through zero is used because slope and intercept cannot both be estimated.
2. Gas concentration to partial pressure
Pressure is absolute pressure. Water vapour is neglected in v0.2, so the entered pressure is treated as the pressure of the modelled dry gas mixture. Because partial pressure changes with gas fraction and bottle pressure, it is reported per gas and time point in Results rather than as a static metadata value.
3. Headspace amount
v0.2 uses Z = 1 and is intended for normal incubation pressures.
4. Temperature-dependent Henry solubility
The Henry convention used here is:
with units mol m-3 Pa-1.
Reference values are stored at 298.15 K and corrected to the bottle temperature using Sander (2023):
Stored temperature-range metadata are used for warnings where a supporting range is available. For entries without such a range, the two-parameter correction should be regarded as a local temperature approximation.
Gas solubility constants used
| Gas | Hscp,* at 298.15 K | B (K) | Stored temperature range |
|---|---|---|---|
| CO | 9.70 × 10-6 | 1300 | 278-323 K |
| CO₂ | 3.40 × 10-4 | 2300 | - |
| CH₄ | 1.40 × 10-5 | 1600 | 275-328 K |
| NO | 1.90 × 10-5 | 1600 | - |
| N₂O | 2.40 × 10-4 | 2600 | - |
| H₂S | 1.00 × 10-3 | 2100 | - |
| C₂H₆ | 1.90 × 10-5 | 2400 | 275-328 K |
| N₂ | 6.40 × 10-6 | 1300 | 278.15-323.15 K |
| O₂ | 1.30 × 10-5 | 1500 | 274-328 K |
All Henry solubility values, temperature coefficients and stored ranges are selected from Sander (2023).
5. Optional salting-out correction
NaCl-equivalent concentration is optional. If it is blank or 0, the pure-water Henry solubility is used. When a value is supplied, the Weisenberger-Schumpe salting-out correction is applied where a gas-specific parameter is available:
This is an NaCl-equivalent approximation, not a full mixed-electrolyte model. CO has no parameter in this model, so CO is left uncorrected and flagged.
6. Dissolved amount
This is the molecular dissolved gas amount. For CO₂ and H₂S, pH-dependent pools are calculated separately.
7. Optional pH-dependent speciation
CO₂ / carbonate
At 25 °C, the implemented values are:
- pKa1 = 6.352
- pKa2 = 10.329
Both are recalculated for the sample temperature.
H₂S / sulfide
At 25 °C, the implemented values are:
- pKa1 ≈ 6.980
- pKa2 = 14.00
H₂S, HS⁻ and S²⁻ are included. Around neutral pH the S²⁻ fraction is normally extremely small.
8. Total bottle amount
This definition is the same for every gas. Estimated DIC and estimated dissolved total sulfide are separate outputs.
9. Sampling-loss correction for time-series experiments
Repeated gas and liquid sampling physically removes material from a closed bottle. The measured bottle amount therefore describes what remains at that time point. When optional sampling volumes are supplied, (E)Gasboard additionally reports a sampling-corrected inventory that adds back material removed during previous sampling events.
Sampling volumes entered on row i are assumed to be removed after the measurement on that row. They do not alter the corrected value for row i; they first contribute to the correction at the next time point.
For CO₂, a second sampling correction is calculated for total inorganic carbon when pH is available. Liquid sampling then removes the estimated DIC pool (CO₂* + HCO₃⁻ + CO₃²⁻), while headspace sampling removes gaseous CO₂. H₂S is handled analogously using the estimated dissolved total sulfide pool.
The corrected value is a mass-balance inventory, not a prediction of the exact concentration
that would have occurred in an unsampled bottle. Sampling changes liquid and headspace volumes and can therefore
also affect subsequent gas-liquid partitioning. Enter the actual liquid volume present at every time point;
(E)Gasboard does not automatically subtract liquid_sample_mL from later rows.
CO₂: physical CO₂ and estimated DIC
CO₂ has two useful outputs and they are deliberately kept separate.
Physical CO₂
This is the same physical total reported as total bottle amount.
Estimated dissolved inorganic carbon
Estimated DIC is only added when pH is available. It does not replace the physical CO₂ result.
Important for CO₂ utilization and carbon-balance experiments: estimated DIC is strongly dependent on pH because pH determines the distribution between CO₂*, HCO₃⁻ and CO₃²⁻. Even small pH changes can substantially affect the estimated DIC pool. For quantitative CO₂ utilization or carbon-balance analyses, pH should preferably be measured at each time point rather than assumed to remain constant. Sampling-corrected DIC uses the pH entered for each sampling time point.
Detailed carbonate species remain in Extended_data.
Rate & gas-liquid mass transfer
A selected Batch interval is fitted with a straight line. Negative slopes are uptake; positive slopes are production.
For gas uptake, equilibrium concentration and maximum transfer capacity are:
Transfer demand and the minimum kLa required for the observed uptake are:
D = 1 is the calculated maximum transfer capacity. Values near or above 1 indicate that gas transfer may constrain the observed uptake.
Rough kLa screening values
If kLa has not been measured, the tool uses the central values below with a ±50% screening range.
| Vessel / working volume | 100 rpm | 150 rpm | 200 rpm | 400 rpm* |
|---|---|---|---|---|
| Tube (10-20 mL) | 8 | 15 | 30 | 80 |
| Flask (20-120 mL) | 4 | 12 | 20 | 60 |
| Small bottle (120-500 mL) | 5 | 10 | 15 | 40 |
| Large bottle (0.5-2 L) | 2 | 5 | 8 | 25 |
Values are kLa in h−1. 400 rpm is a higher-uncertainty extrapolation. Use a measured value whenever available.
Literature used for the screening defaults
| Use | Reference |
|---|---|
| CO, vial-scale batch culture | Jang et al. (2017), doi:10.1016/j.biortech.2017.05.023 |
| CO, shaken serum bottles | Schick et al. (2025), doi:10.1016/j.bej.2025.109838 |
| Shaken-vessel kLa ranges | Maier & Büchs (2001), doi:10.1016/S1369-703X(00)00107-8 |
Gas dosing
A dissolved target is converted to its required partial pressure. A headspace target (% or ppmv) is solved together with gas-liquid equilibrium and the pressure added by the dosing mixture.
For CO₂ and H₂S, dissolved targets can refer to the molecular gas or the estimated total dissolved pool when pH is available. If the selected dosing mixture cannot reach the target, the calculation returns an error.
Gas-phase concentration units: % and ppmv
ppmv means parts per million by volume. For the ideal gas mixtures used here, volume fraction and mole fraction are equivalent. (E)Gasboard therefore converts % and ppmv directly for headspace concentrations and dosing mixtures.
Therefore 500 ppmv = 0.05%, 1000 ppmv = 0.1%, and 10000 ppmv = 1%. ppmv is a gas-phase composition unit; it is not a mass-based ppm concentration.
Gas-transfer estimates
kLa depends strongly on vessel geometry, liquid volume, shaking conditions and medium composition. (E)Gasboard therefore uses literature-based estimates for comparable batch systems where available.
These values are intended for screening gas-transfer limitation, not as exact system-specific measurements. kLa and Henry-law values can be replaced by the user. (If you disagree or have more representative values, please let me know!)
CSV/TSV output
CSV and TSV can be downloaded as the compact Results table only, or as a ZIP data package containing Results, Extended_data, calibration tables and Rates_mass_transfer when that optional analysis has been run.
Current assumptions and scope
- Each measurement is treated as the measured state of the bottle at that time point.
- Optional liquid/headspace sample volumes are treated as material removed after the measurement on that row and are applied only to subsequent time points.
- Sampling-corrected values are mass-balance inventories; actual bottle volumes must still be entered for every time point.
- Dissolved amounts are equilibrium estimates from Henry's law.
- Absolute pressure is used.
- Water vapour is neglected in v0.2. A correction is planned for a later version.
- v0.2 uses Z = 1.
- Salting out is optional and uses NaCl-equivalent concentration.
- Full mixed-electrolyte corrections are not included.
- Volatile fatty acids are not included.
- Built-in kLa values are literature-based screening estimates for shaken batch systems and can be replaced by the user.
- The mass-transfer module currently screens gas uptake; gas-production/outgassing limitation is not yet modeled.
- Formal uncertainty propagation is not included.
References
Henry solubility and temperature dependence
Sander, R. (2023). Compilation of Henry's law constants
(version 5.0.0) for water as solvent. Atmospheric Chemistry and Physics,
23, 10901-12440.
doi:10.5194/acp-23-10901-2023
Optional salting-out correction
Weisenberger, S. & Schumpe, A. (1996).
Estimation of gas solubilities in salt solutions at temperatures from
273 K to 363 K. AIChE Journal, 42, 298-300.
doi:10.1002/aic.690420130
Carbonate and sulfide speciation are documented here by the equations and pKa values implemented in the calculation.
Metrics & citation
(E)Gasboard - Open research software for gas calculations.
Site analytics for completed actions. Uploaded files and calculation values are not sent.
Software output
Open research software with documented calculations and a public web interface.
Citation
(E)Gasboard - Open research software for gas calculations, Reinier A. Egas, 2026. doi:10.5281/zenodo.22704550
Source code: GitHub repository
Requests, suggestions or ideas for improvements are welcome - please reach out.