Tech Challenge


Tech Challenge






Chemical Compatibility with Plastic Desiccator

HygroscopINC generally uses large plastic vacuum desiccators (greater than 20 L and up to 28.5" Hg vacuum pressure) to keep water from reentering its hygroscopic chemicals as they cool from 500ºF. However, they have noticed the plastic starting to crack and fissure when used to cool one of the newer chemicals. They suspect the plastic of their desiccator is not compatible with the fumes of their new chemical, and this is the cause of the fissures inside the plastic desiccators. They have not noticed any problems with the glass bottles storing the chemical or the silicone and neoprene gaskets on their desiccators, or the metal liner of the caps on the storage bottles. Outside of the glass and the thin stainless steel liner of the caps (silicone and neoprene), they do not have any chemical compatibility data. They are looking for a few desiccators that would be compatible with their newest chemical to replace the fissured plastic units.

What would you suggest?

  1. Glass/Stainless Steel Desiccator with Two Stainless Steel Shelves (08901-60).
  2. The 250-mm Pyrex® Glass Vacuum Desiccator (34548-29).
  3. A vacuum oven with a stainless steel interior (such as the
    1.8 cu ft Salvis® Vacucenter Oven 52402-10).
Answers:

  1. Glass/Stainless Steel Desiccator with Two Stainless Steel Shelves (08901-60).

    Correct! This desiccator has a high capacity interior and is made of parts that are already known to be compatible with the new chemical.


  2. The 250-mm Pyrex Vacuum Desiccator (34548-29).

    Incorrect. Based on the large volume the customer needs the desiccator to hold, this unit will not be sufficient. It has only a 10.5 L capacity.


  3. A vacuum oven with a stainless steel interior (such as the
    1.8 cu ft Salvis Vacucenter Oven 52402-10)


    Incorrect. Although this option would satisfy the internal capacity and chemical compatibility issue, it is overkill. A much more economical alternative exists.

Graduate Student Recovers Immunoglobulin IgE from Serum Samples

An immunology graduate student is designing her thesis research project. She knows she wants to isolate, purify, and recover immunoglobulin IgE with a molecular weight of about 200,000 Dalton from high volumes of serum samples. So, she is looking for a method using a 100,000 Dalton MWCO (molecular weight cut-off) device.

Which of the following methods would work best for this application?

  1. Use disposable ultrafiltration units by Advantec® (such as 02910-52).
  2. Use Millipore® Steriflip® disposable vacuum-driven filter devices (such as 29969-20).
  3. Use Millipore® Stirred Cells (such as 29968-14 with Ultrafilter Disc 29949-36).
  4. Use Spectra/Por® Biotech-Grade Dialysis Tubing (such as 02890-14 with Dialysis Tubing Closure (02899-71).
Answers:

  1. Use disposable ultrafiltration units by Advantec® (such as 02910-52).

    Incorrect This is not a good choice for large volumes at 2 mL capacity per unit, and there is no option for 100,000 Dalton MWCO.


  2. Use Millipore® Steriflip® disposable vacuum-driven filter devices (such as 29969-20).

    Incorrect. This is inefficient for large volumes at 50 mL per unit, and 0.22 microns is roughly equivalent to 2 million Daltons, so the pore size is far too big.


  3. Use Millipore® Stirred Cells (such as 29968-14 with Ultrafilter Disc 29949-36).

    Incorrect. This is inefficient for large volumes at 50 mL per unit, although the 100,000 Dalton MWCO membrane is available.


  4. Use Spectra/Por Biotech-Grade Dialysis Tubing (such as
    02890-14 with Dialysis Tubing Closure (02899-71).


    Correct! You can cut off as much tubing as you need to isolate, purify, and recover large volumes in fewer batches and it is available in the 100,000 Dalton MWCO required.

Inspecting HVAC System

A recently hired technician for Rob-O’s Controlled Environment Services needs to perform an inspection of a customer’s cleanroom HVAC system to make sure it is operating according to required specifications. It should be supplying enough air volume and velocity to produce positive pressure. Leaks or blockages should not be evident inside the ductwork. And, the temperature of the air blowing into the cleanroom should be within a certain tolerance compared to the temperature programmed into the thermostat. The system also needs data logging to record the readings and PC-downloading capabilities to produce a report.

Which instrument should the technician choose?

  1. The Testo® CFM Vane Anemometer (10323-15).
  2. The Cole-Parmer® Heavy-Duty Thermoanemometer with Data logger (37955-10).
  3. The Alnor® Analog Balometer Kit (68511-51).
  4. Extech® Heavy-Duty CFM Hot-Wire Thermoanemometer (10200-09 with Data Acquisition and Logging Software (10200-10) and Data logger Module (10200-20).
Answers:

  1. The Testo® CFM Vane Anemometer (10323-15).

    Incorrect You cannot get very far into the ductwork with this integral 4” diameter vane, and it does not have data logging or PC compatibility, although it provides air velocity, air volume and temperature measurements.


  2. The Cole-Parmer® Heavy-Duty Thermoanemometer with Data logger (37955-10).

    Incorrect. Although this unit measures air velocity, air volume, and temperature, and has data logging as well as PC downloading, it is not ideal because the remote probe is not very long, so it cannot be inserted deeply into the ductwork.


  3. The Alnor® Analog Balometer Kit (68511-51).

    Incorrect. The balometer only measures volume airflow. It has no air velocity, temperature, data logging, or PC downloading abilities.


  4. Extech® Heavy-Duty CFM Hot-Wire Thermoanemometer (10200-09 with Data Acquisition and Logging Software
    (10200-10) and Data logger Module (10200-20).


    Correct! This unit measures air volume and air velocity as well as temperature. It also logs 8000 data points and downloads the data to a PC via RS-232.