Labconco offers two rotational molded polyethylene-lined glove boxes with HEPA filtration: the Precise® HEPA-Filtered Glove Box and the XPert® Weigh Box. Both of these boxes have a built-in blower and inlet/outlet HEPA filters to remove hazardous particulates.
In addition, the XPert Weigh Box features a balance vibration isolator (a marble slab with stainless steel cover and four isolation pads) and an anti-static ionizer fan to control static charge.
A common application for either of these glove boxes is weighing hazardous powders using an analytical balance. We know that Precise Boxes contain and isolate hazardous particulates down to 32 ng/m3 through 3rd party testing confirmed by SafeBridge Consultants, Inc.
But how accurately can an operator weigh drug powders on an analytical balance in a Precise Glove Box with an on-board motor? Labconco engineers put the following performance goal to the test:
“The Precise HEPA-Filtered Glove Box shall permit weighing of samples to five decimal places with an analytical balance without affecting the balance performance. The glove box operational airflow volumes shall allow the precision and accuracy as specified by the manufacturer of the analytical balance.”
Equipment Used in the Test:
Balance Stability Test Parameters and Procedure
The Mettler Toledo AX105 Delta Range Analytical Balance was placed inside the Precise Glove Box atop the Balance Vibration Isolator. The glove box was located in a typical laboratory setting. No effort was made to isolate the box from foot traffic or other laboratory equipment operating in the room.
The testing consisted of weighing calibration weights (20 mg, 200 mg and 2 grams) five times. After each weighing, the weight was removed and the balance allowed to return to zero. The measurements were taken with the glove box blower off and at settings of 13, 20, 61 and 100 cubic feet per minute (CFM).
Using the identical sampling procedure, the same test performed but without the Balance Vibration Isolator. The Mettler AX105 Balance was placed directly on the interior surface of the Precise Glove Box.
The five weigh-outs for each target weight were averaged, then the standard deviation and relative deviations were calculated. Complete test data may be found in the Precise HEPA-Filtered Glove Box and XPert Weigh Box Test Report.
Below are the summaries of results for the test performed with the Balance Vibration Isolator and the test performed without the Balance Vibration Isolator.
Precise Test 1: Analytical Balance Stability Test Results, Precise HEPA Filtered Glove Box with Balance Vibration Isolation (Marble Slab)
Precise Test 2: Analytical Balance Stability Test Results, Precise HEPA Filtered Glove Box without Marble Slab
The performance goal was met: the Precise HEPA-Filtered Glove Box delivers precise, reproducible weighing. Balance stability testing on the Precise HEPA-Filtered Glove Box confirmed that it permits weighing of samples with an analytical balance to five decimal places. In both tests, the relative standard deviations were extremely low, indicating that the analytical balance remained stable inside the box.
The results of the test using the marble slab were only slightly better. Neither airflow through the glove box nor vibration from its mechanical components significantly affected the weight measurements, indicating that the Precise Glove Box is inherently stable.