Analysis Conditions

  In 21CFR11 environments, this section is applicable only to members of the Developer group, however, members of the Analyst group may find information in this section helpful. Parameter file information that is available to Analysts is created by a member in the Developer group using information in this section.

(or click the Analysis Conditions tab when in Advanced option presentation)

Analysis conditions specify the parameters used to guide an analysis.

Analysis Conditions Fields and Buttons Table
Field or Button Description
Absolute pressure dosing [check box]

Specifies pressure targets in mmHg, mbar, or kPa instead of relative pressure. If this option is selected, the Relative Pressure labels and entries change to Absolute Pressure in the selected pressure units.

Adsorptive [drop‑down box] Select an Adsorptive Properties file from the list of defined gases to be used for analysis. After selection, click Edit to modify adsorptive properties.

See Adsorptive Properties.

Analysis Conditions [drop‑down box] Use to browse for an Analysis Conditions file that contains analysis condition parameters to be used in the analysis.
Backfill [button] Select gas for backfilling the sample tube at the start and end of an analysis.

The options are disabled if the file status is Entered, Complete, or Analyzing.
Dosing [button]

Options for dosing tolerance, low pressure dosing, and dosing near saturation pressure.

Absolute / Relative pressure tolerance. Values used to determine how close the actual pressure must be to each target pressure from the pressure table. At lower pressures, the relative tolerance value is lower. At higher pressures, the absolute tolerance value is lower.  For example:

Experiment 1. There might be an absolute tolerance of 5 mmHg, a relative tolerance of 5%, and a target pressure of 40 mmHg; 5% of 40 mmHg is 2 mmHg. Since 2 mmHg (relative tolerance) is lower than 5 mmHg (absolute tolerance), 2 mmHg is used. Therefore a minimum pressure of 38 mmHg (40 - 2) must be attained to collect data for a target pressure of 40 mmHg.

Experiment 2. There might be an absolute tolerance of 5 mmHg, a relative tolerance of 5%, and a target pressure of 200 mmHg; 5% of 200 mmHg is 10 mmHg. Since 5 mmHg (absolute tolerance) is lower than 10 mmHg (relative tolerance), 5 mmHg is used. Therefore a minimum pressure of 195 mmHg (200 - 5) must be attained to collect data for a target pressure of 200 mmHg.

Normally, surface area measurement points are widely spaced and the resulting measurement is not very sensitive to the precise location of points so wider tolerances may be used. Unnecessarily tight tolerances lengthen the analysis.

First pressure fixed dose.

This option is most frequently used when performing a standard nitrogen analysis of mesoporous materials such as catalysts. If the first pressure table point is low and the gas uptake of the sample is expected to be high, this option can shorten the time required to reach the first point on the pressure table.

The sample is dosed repeatedly at low pressures with a specified amount of gas until the first pressure point is reached. This initial dosing quickly meets the adsorptive demand of the sample.

The first point on the pressure table is the threshold value, triggering the transition from the Fixed Dose Mode to Pressure Table Mode. When the first pressure table value is reached, Fixed Dose Mode is disabled, and points are equilibrated and recorded in accordance with the specified pressure table.

Enter the amount of gas to be added to the sample for each dose cycle.

Maximum volume increment. Select to determine when additional data points are collected between target pressures in regions of adsorption. When the maximum increment has been adsorbed since the last collected data point, another point is equilibrated and collected. During desorption, this field is treated as a maximum volume decrement value.   

Equilibration [button]

Provides options to specify the equilibration interval and delay time.

Minimum equilibration delay at p/po > = 0.995. The minimum number of seconds required before equilibration can occur for a relative pressure greater than or equal to 0.995. This field is not available if Absolute pressure dosing is selected on the Analysis Conditions tab.

Relative Pressure (p/po) or Absolute Pressure. The pressure the equilibration interval will be applied.

Equilibration interval [text box]

The number of seconds between successive pressure readings during equilibration. Long equilibration intervals tend to lengthen analyses, however, they do improve data integrity. Short equilibration intervals produce a faster analysis but may reduce the accuracy of data.
Free Space [button]

How the free space is to be measured.

Free Space
(continued)

Measure

  • Lower dewar for evacuation. If the dewar is to be lowered for evacuation, select this option and enter the length of time for evacuation after the free space measurement in the Evacuation time field. If using a cryostat, the operator must manually move the cryostat assembly when prompted.
  • Evacuation time. The length of evacuation time prior to free space measurement.
  • Outgas test. Checks for system leaks or sample outgassing. After free space is measured, the dewar is lowered and the sample evacuated for the specified amount of time. The leak test is performed after evacuation. If the pressure rises more than 0.025 mmHg within the time specified in the Outgas test duration field, outgassing is present. If a leak is found, the leak test repeats nine times, with 30 minutes evacuation between tests. If the 10th leak check fails, the analysis stops and the operator is notified. While leak testing slightly increases analysis time, it prevents the continuation of analysis and collection of erroneous data if a leak occurs.

Enter. Allows manual entry of free space.

Calculate. Use to have the free space measurement calculated using the sample and tube parameters.

Free Space
(continued)

Enter. Allows manual entry of free space.

Measure after analysis. Measures free space after analysis ends. Enter the estimated free space measurements.

p° and Temperature Options [button]

How the saturation pressure (P0) is to be measured or calculated and the analysis bath temperature.

p° Options. Select one option indicating how P0 is to be measured or calculated.

  If using a cryostat, select either the Calculate p0 or Entered p0 option. Also enter an analysis temperature.

Analysis Temperature Options. Select an option to enter analysis temperature manually, or choose to have it automatically calculated from p° or P0. An estimated P0 can be entered if a measured P0 option is selected.

Psat Gas. If choosing to measure the P0 for each isotherm point using a gas other than the adsorptive, select the P0 gas from the drop-down list, then click Edit to modify the P0 adsorptive properties. Refer to the Adsorptive drop-down list earlier in this table for details on editing this window.

Pre-analysis evacuation time [text box]

Evacuation is required prior to analysis. The default setting is 30 minutes.

Preparation. Use to set the evacuation rate, unrestricted pressure, and setpoint.

Temperature. Use to set the temperature and ramp rate.

Preparation [button]

Evacuation rate / time / level, leak test and time values, elevator prompts, and in situ degassing or activation.

Evacuation time. The length of time for preliminary evacuation.

Fast evacuation. Select for samples (such as pellets) that do not fluidize or shed particles during evacuation.

Unrestricted evac. from. The pressure at which unrestricted evacuation is to begin. This option is enabled when Fast evacuation is not selected.

Preparation
(continued)

Leak test. Enables the system to check for leaks or sample outgassing before the analysis. The leak test allows sample pressure to rise during the test. If the pressure rises more than 0.15 mmHg, the analysis does not proceed and the operator is notified. While leak testing slightly increases analysis time, it prevents the continuation of analysis and collection of erroneous data if a leak exists.

Use TranSeal. Select if using the TranSeal to transfer the sample from the preparation port to the analysis port under vacuum.

Vacuum setpoint. The vacuum level to be achieved before timed evacuation begins.

Preparation
(continued)

Backfill gas. Lists the available backfill gases.

Vacuum level. The pressure for unrestricted evacuation.

In situ activation. When selected, preparation steps will be done. If not selected, the task table is disabled and analysis starts after the preliminary evacuation.

  See Chemical Adsorption Tasks for information on inserting tasks for a chemical adsorption analysis.
Repeat analysis [check box] Pressure at which heating will stop and hold the sample temperature approximately constant until the pressure falls below the Hold pressure. This feature prevents damage to the sample structure due to 'steaming,' as well as sample elutriation due to excessive escaping gas velocity.
Temperature [text box]

Provides access to furnace and accessory temperature control.

Analysis temperature. Enter the analysis temperature.

Temperature rate. Enter the analysis temperature rate.

Termination [button]

Backfill options after analysis.

Select the backfill gas if backfill is to be done after the analysis.

Cool to less than 50 °C. Select to enable the cool down option.

  For fields and buttons not listed in this table, see Common Fields and Buttons.
 
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