Microtrac only presents data within the particle size range of a given model or instrument set-up. Particles larger than or smaller than the instrument measuring range are not included as part of the distribution or other data. For this reason, “percent smaller or larger than data begin with 100% at the largest or smallest size measured in a sample, even though some particles may exist outside the measuring range.  Two modes of operation are currently available for the Microtrac S3000 particle size analyzer, dry & wet.

1. Using the dry particle controller with compressed air jet and vacuum collector, the S3000 can measure particles with diameters between 250 nanometers & 1408 microns.  The dry particle set-up is useful for particles that dissolve in most solvents.

2. Using the wet sample cell and VSR pump, the S3000 can measure particles suspended in solvent with diameters between 40 nanometers and 1408 microns.  The wet particle set-up is more convenient for particles that tend to pick up a charge and/or agglomerate.  The particles can first be mixed with solvents and surfactants, sonicated using an ultrasonic horn and then added to the apparatus for measurement.

Several types of solvents can be used to suspend particles for the wet sample cell.  A partial list is included in the help file.  Basically, solvents suitable for contact with CRES 304 (stainless steel), Teflon tubing, Buna o-rings, and glass sample cells are acceptable.  The solvents should not leave a residue in the apparatus or cause corrosion.  Due to availability, heath, safety, and environmental concerns, de-ionized water is the preferred solvent.  De-ionized water is the only solvent that shall be left in the apparatus for extended periods of time.

1.  The nature of the continuous flow wet sample cell helps insure uniformity of the mixture.  However, temperature gradients will reduce the accuracy of the measurements.  All samples should be allowed to equilibrate before running a measurement.  This is best done by adding the sample to the apparatus and then allowing it to cycle (pump) for a few minutes before initiating a measurement.

2.  The refractive index for the particles and for the solvent are of importance, especially when measuring larger particles ( >40 microns).  Refractive indices for several compounds and solvents are given in the Help menu.  An Abbe Refractometer can be used to determine the refractive index or Index Matching can be accomplished using oils with known refractive indices.

3.  Particle shape and absorption are also of concern.  Only a few choices are available for these variables in the Flex setup menus.  They can be determined using optical microscopy.

4.  The wet sample cell requires dilute samples.  The Flex software can and should be used to monitor sample concentration while adding the sample.

5.  Agglomeration is always a concern for both the dry and wet sample cells.  Microscopy is a good way to check for agglomerates.  Work to minimize electrostatic and other attractive forces between the particles by selecting appropriate solvents and surfactants when preparing the samples.  Static electricity is a particular problem for the dry sample cell.

Image taken from the S3000 Op. & Main. Manual, Microtrac 2001.

Obtain the wet sample cell (generally stored in the drawer built into the S3000 case) and inspect for damage.  The glass cell windows should be clear of stains, streaks, and dust.  The outside of the glass (dry side) is coated with a special optical film.  The film is easily damaged.  Except for dusting using a compressed air can, the dry side should only be cleaned under the direction of the lab mentors.  The wet side (pr inside) can be cleaned using Q-tips, pipe cleaners, or other suitable scrubbing devices.  A mild acid such as 3% phosphoric acid can be used to remove stains from inside the flow cell.  Remove the o-rings and inspect for nicks or tears.  New o-rings are kept in the built-in drawer.  Clean the stainless steel o-ring groove and mating flanges using a "very fine" steel wool or Scotch-Brite pad.  Always rinse the mating flanges and inside of the sample cell with de-ionized water before installing (do not allow the outside of the glass to become wet).

Obtain the wet sample cell holder and clean the stainless steel mating flanges. Rinse the mating flanges and inner bore of the pipe fittings with de-ionized water.  Open the sample module door on the front of the S3000.  Insert the sample cell holder through the top opening in the S3000 and rotate until it drops down and engages the locating pins.  Rotate the two dogs to push down on the flange of the sample cell holder and tighten the thumb screws finger tight.

Do not bump the prism assemblies or other optical fixtures inside the S3000 while loading the sample cell.  Ensure the o-rings are in place.  Carefully load the sample cell into the sample cell holder through the sample module door in the front of the machine (the top and bottom flanges on the sample cell are different sizes, the narrower is the top and the handle points toward the front of the machine).  Tighten the cell retaining knob on the top of the sample cell holder finger tight.  Close the sample module door on the front of the S3000.

Refer to the module Using the Wet Sample Cell for how to use the equipment.

Obtain the dry sample cell (generally stored in the drawer built into the S3000 case) and inspect for damage.  The cell bore should be clear of stains, streaks, and dust.  The dry sample cell can be cleaned using Chem-wipes, Q-tips, pipe cleaners, or other suitable scrubbing devices.  A mild and fast evaporating solvent such as acetone can be used to remove stains from the dry sample cell.

Open the sample module door on the front of the S3000.  Do not bump the prism assemblies or other optical fixtures inside the S3000 while loading the sample cell.  Insert the dry sample cell through the top opening in the S3000 and rotate until it drops down and engages the locating pins.  Rotate the two dogs to push down on the flange of the sample cell and tighten the thumb screws hand tight.   Close the sample module door on the front of the S3000.

Only clean, dry air can be used to supply the compressed air jet.  A commercial grade high pressure compressed air bottle regulated to 100psi is preferred.  The building compressed air supply can be used if a quality air dryer and filter is installed and a regulator is used to keep the supply pressure at 100psi. Connect the compressed air source to the Dry Particle Controller and connect the Dry Particle Controller to the Dry Sample Cell.

Connect the vacuum to the base of the Dry Sample Cell.

Refer to the module Using the Dry Sample Cell for how to use the equipment. 

Turn on the S3000 and the VSR (the VSR power switch is on the back plate in the lower left-hand corner).  Verify the reservoir in the VSR is filled to within a 1/4" of the overflow drain.  Check the time, it is a good idea to allow the S3000 to warm up for several minutes and equilibrate before starting measurements.  Several steps can be done during this time (up to clicking the SetZero icon).

Set the pump speed (75% is a good starting point, slower for fragile particles like hollow spheres and faster for particles that tend to agglomerate) and push the Circulate button to start the pump.  Check for leaks at all external connections.  Run the pump for about 10 seconds and then turn off and immediately check for air bubbles in the reservoir and in the Teflon tubing.  It is a good idea to repeat this cycle a couple times to verify all air bubbles are out of the system.  Push the circulate button again and leave the pump on. 

Boot up the computer and open the Microtrac Flex software (choose the latest version if starting new research or whichever version has been used for previous measurements).  Open the Tools tab and select Hardware Configuration.

The Hardware Configuration window will open and the Sampling Systems tab will be displayed.  Check the Wet Application Type, verify the MAC 26 and the SDC Installed are not selected.  Verify none is selected for ASVR Com Port.  Then display the S3000/S3500 Analyzer Tab. Verify COM 1 is selected and Size Range is set to .021 um - 1408 um.  Click on the Sample Cell button.

The Sample Cell Management window will open.  Select installed cell ID of 0250 and select OK to save settings.  The Hardware Configuration window will become active again.  Select OK to save settings.

The Hardware Configuration window will close and the main window will become active. Open the Measure tab, Select Instrument, S3000.

Flex will open the last database used.  Note the Title Bar now displays "S3500/3000 - WET - 0.0215 To 1408 um" and the filename of the last used database.  If it does not display this, close the database window (not the Flex window) and repeat the Hardware Configuration.

Open the File tab and select Create New Database.

Type in a name for the new database.  A generic description of the material or the title of the project make good database names.  The default stores the new database in a folder called Databases.  If desired, select an alternate location for the database by changing the active directory.  Click Open. 

Microtrac will verify you wish to switch databases, click yes to proceed. The new database will open.

Click on the Setup icon on the Toolbar.

The Measurement Setup window will open.  Click the Options button.

The Measurement Setup Options window will open with the Identifiers tab displayed.  Type in a title for the samples you are preparing to analysis.  You can also type in the ID of the first sample you plan to analyze at this time (product names, dates, lot numbers or any unique way of identifying the samples).  1: and 2: refer to separate lines of the same sample ID.  Additional information can be added to the Notes.  Click on the Timing tab.

Setzero refers to collecting background data that will later be subtracted from the actual measurements.  Set the amount of time the software will use to collect background data. 10 seconds is a good starting point, adjust until repeat measurements of the same sample are within an acceptable level of deviation.  Also, set the amount of time the software will collect data for the specific sample and the number of times to analyze the sample.  Again, 10 seconds is a good starting point and 3 runs is usually sufficient to show the reliability of the measurement.   Click on the Analysis tab. 

The Analysis tab will open with the Particle Information tab displayed.  Enter the refractive index of the particles you will be measuring.  Click on Reference to open a pdf file giving the refractive indices for several common molecules.  If necessary, an Abbe Refractometer or Index Matching using oils with known refractive indices can be used to determine the refractive index.  Select the transparency and the particle shape.  These properties can be determined with optical microscopy.  Type in a New Particle Name and click Save.  Then click on the Fluid Information tab.

Enter the refractive index of the fluid you will be using to suspend your particles.  De-ionized water is the preferred fluid and is provided in the poly bottle above the sink.  The refractive indices of several fluids are available in a pdf file by clicking the Reference button.  Type in a New Fluid Name and click save.  Click on the Analysis Options tab.

Verify S3000 is the selected Analysis Mode and Enabled Standard is the Filter.  For additional information on these choices and the Advanced button, please refer to the help menu in the Flex software.  Click on the Perspective tab.

Verify the Progression is standard, the Distribution is Volume, the size range is .0215 to 1408, and the Residuals is not enabled.  For additional information on these choices, please refer to the help menu in the Flex software. If you are looking for a certain percentile like D84, adjust the Percentiles and Size % as necessary.  Click OK.

Your settings will be saved for the current session and the Measurement Setup window will reappear.  Enter a Setup Name to Save (generic name of the particle works well) and click Save.  Click close to return to the Database window.

Open the Measure tab and Verify With Save and Auto-Align are checked.

The blue icons Auto-Align and Auto-Save DB should be displayed on the toolbar. 

Verify the S3000 laser has been on for at least five minutes and the VSR pump is circulating fluid.  If you are using de-ionized water to suspend your particles, skip to the next image.  If you intend to us a solvent other than de-ionized water, turn off the Circulate button and press the Drain button until all water is removed from the VSR and the lines connecting the sample cell.  Place the intake line into a reservoir (minimum of 2 liters) containing the solvent you intend to use.  Press the Rinse button until all water is pushed out of the intake line and the new solvent is coming out of the Drain line.  Press the Fill button until the solvent has filled the reservoir in the VSR to within 1/4" of the overflow drain.  Press Circulate, allow to circulate for a few seconds and stop.  Check for air in the reservoir and in the lines connecting the sample cell.  Repeat until no air bubbles are visible, then leave the Circulate button on.

If you did not already enter a sample name for your first sample, click on the ID icon on the toolbar and enter a sample name.  Otherwise click on the S/Z icon to calibrate the instrument.  

The software will automatically align the laser and collect particle size data to be used as a baseline for the solvent currently in the system.  Once Setzero has been performed, a green SETZERO icon will replace the yellow No SETZERO icon on the toolbar and the LD icon will become active.  If a red HIGH BACKGROUND icon appears, perform a rinse and fill cycle to flush excess contaminates out of the system and click on the S/Z icon again.  If the system still displays the HIGH BACKGROUND icon, the system requires maintenance.  Contact the lab mentor.  Once a green SETZERO is displayed, click on the LD icon to open the Sample Loading window.

The Sample loading window will display the concentration of the sample as you add it to the reservoir on the VSR.  It takes a few seconds for the computer to collect enough data to display the concentration, so only add small amounts at a time.  For fine powders (less than 40 microns), a good method is to suspend your sample with some of the solvent you are using in a beaker.  Then use a pipet and transfer sample to the machine.  For larger particles, a spatula is adequate to transfer dry powders.

Only disperse one drop at a time and watch how the concentration rises until you get a feel for how much sample is required to reach the optimum concentration.  The optimum concentration is shown by a green bar. 

If you over shoot the optimum concentration, click on the Drain button to remove some fluid from the system. Then click the Fill button to restore the fluid to within 1/4" of the overflow drain in reservoir.  Press Circulate to resume flow.

Once the concentration of your sample is in the green, click the Run Icon in the Sample Loading Window to measure the sample.

When the instrument has completed the number of data collection cycles you chose in the Measurement Setup Options, the computer will automatically average the data cycles and display the average distribution and particle size information.  Each data cycle and the average will be automatically saved in the database for future reference.  

Refer to the module on creating data reports if you wish to create a report before collecting more data.  Note: once the sample data is stored in the database (auto database save), it can be reloaded and made into a report at any time. 

When you have finished with the current sample, turn off the Circulate button and press Drain until all fluid is removed from the VSR and the lines connecting the VSR to the wet sample cell.  

1. If you plan to take another measurement, then press Rinse for a few seconds.  Press Fill until fluid is within 1/4" of the overflow drain in the VSR reservoir.  Press Circulate, allow to circulate for a few seconds and stop.  Check for air in the reservoir and in the lines connecting the sample cell.  Repeat until no air bubbles are visible, then leave the Circulate button on.  Press SetZero in the Flex software.  Once you have a green SetZero icon you are ready to add new sample.  Be sure to press the ID icon and change the sample ID before adding the next sample.

2. If you are done with the instrument and used de-ionized water as the solvent, then press Rinse for a few seconds.  Press Fill until water is within 1/4" of the overflow drain in the VSR reservoir.  Press Circulate, allow to circulate for a few seconds and stop.  Press Drain until all water is removed from the VSR and the lines connecting the VSR to the wet sample cell.  Repeat this cycle several times to ensure sample is removed from the instrument. Then fill with de-ionized water.   Press Circulate, allow to circulate for a few seconds and stop.  Check for air in the reservoir and in the lines connecting the sample cell.  Repeat until no air bubbles are visible, then leave the Circulate button on.  Press SetZero in the Flex software.  Once you have a green SetZero icon you are ready to power down the S3000, the VSR pump, and the computer.
3. If you are done with the instrument and used a solvent other than de-ionized water, move the intake line to a bucket with warm tap water and press Rinse until all solvent is pushed out of the intake line.  Wipe off the intake line and insert it back into the de-ionized water reservoir.  Then press Rinse for a few seconds.  Press Fill until water is within 1/4" of the overflow drain in the VSR reservoir.  Press Circulate, allow to circulate for a few seconds and stop.  Press Drain until all water is removed from the VSR and the lines connecting the VSR to the wet sample cell.  Repeat this cycle several times to ensure sample & solvent is removed from the instrument. Then fill with de-ionized water.   Press Circulate, allow to circulate for a few seconds and stop.  Check for air in the reservoir and in the lines connecting the sample cell.  Repeat until no air bubbles are visible, then leave the Circulate button on.  Press SetZero in the Flex software.  Once you have a green SetZero icon you are ready to power down the S3000, the VSR pump, and the computer.

The Flex software has many additional features.  As you continue your research, I encourage you to review the user manuals to become more familiar with the capabilities available. 

Turn on the S3000, the vibrator on the dry particle controller, the compressed air valve, and the vacuum.  Note: the equipment is controlled by the Flex software and should not actually come on until the appropriate program is executed.  Check the time, it is a good idea to allow the S3000 laser to warm up for several minutes and equilibrate before starting measurements.  Several steps can be done during this time.

Set the vibrator range (7 is a good starting point, adjust until a uniform feed rate).

Set the air pressure regulator (15 psi is a good starting point, higher for fine particles and lower for coarse).  

Boot up the computer and open the Microtrac Flex software (choose the latest version if starting new research or whichever version you have used for previous measurements).