What Is a Glove Box?
A glove box is a device that enables work in a sealed environment by integrating a glove and a sealed container. They are mainly used when performing work where contact with the outside air or humans is undesirable. For example, cell culture work or work involving the handling of gases harmful to the human body.
Glove Box Applications
Glove boxes are used in many laboratories, mainly in the biological field, such as cell culture and in materials research, where contact with the outside air can cause some kind of reaction.
In the field of materials development, in particular, the outside air contains not only oxygen, which causes oxidation but also moisture, which causes corrosion. Therefore, experiments in the open air often cause unexpected reactions, making it an inadequate experimental environment.
In such cases, gloveboxes were invented to allow manual experiments to be conducted while keeping experimental specimens in a space isolated from moisture and oxygen.
Types of Glove Boxes
Glove boxes can be broadly classified into two types based on differences in their internal cleanliness control mechanisms.
1. Vacuum-type Glove Box
One is a glove box in which the internal space is evacuated once and then filled with an inert gas such as nitrogen or argon.
2. Displacement-type Glove Box
The other type of glove box is a displacement glove box, in which the interior is replaced by an inert gas without drawing a vacuum.
The vacuum-type glove box, in which a vacuum is pulled once, can create a space with a high level of cleanliness because impurities such as moisture and oxygen inside the glove box can be wiped out.
In addition, if the sample to be placed in the glove box is very reactive, it is likely to react with the container body and the glove as well. Therefore, to accommodate highly reactive samples, it is necessary to appropriately select a wide range of materials for the body and glove, from plastic to stainless steel.
How to select a Glove Box
In general, a vacuum-type glove box provides a cleaner space but requires a vacuum pump as accessory equipment. These are often expensive and a bit large for simple experiments in which the environment is not severe. For this reason, it is a good idea to start with a displacement-type glove box when using it for experiments that are relatively less dependent on the surrounding environment or when introducing it.
In either case, however, it is important to select materials for the body and glove that are not reactive to the sample you plan to experiment with.
Additional Glove Box information
1. Glove Boxes and Inert Gases
Nitrogen is frequently used as an inert gas, not only in glove boxes. For example, it is used as a purging gas for food packages due to its inert properties, and it is also frequently used in electronics-related factories, such as those in the semiconductor field.
Nitrogen is readily available in the atmosphere at a volume ratio of approximately 78.1%, making it cost-effective. Its specific gravity is 0.97, which is slightly lighter than air = 1.
Argon, on the other hand, is also present in the air, but at only 0.93% by volume. However, it is still the third most abundant gas in the atmosphere. As a noble gas, argon is even less reactive than nitrogen. Its specific gravity of 1.38 makes it heavier than nitrogen or air, so it accumulates in the glove box and pushes air out from above.
Argon gas is required when a more inert environment is required. In addition, maintaining the pressure inside the glove box higher than atmospheric pressure prevents atmospheric air from entering through the slightest gap in the glove box, thus maintaining a cleaner environment.
2. Moisture removal inside the Glove Box
After the inside of the glove box is replaced with inert gas, moisture may be generated when the desired reaction proceeds. Moisture in the glove box is removed by a moisture adsorbent. The adsorbent may be activated carbon or a special material called a molecular sieve.
Molecular Sieve Description
A molecular sieve is a crystalline zeolite. It is a porous crystal, and impurities in the glove box are removed by the adsorption of molecules into these pores. Naturally, the adsorption characteristics can be controlled by changing the crystal structure, so if you want to absorb only specific organic gases, it is important to select a molecular sieve that matches your application.
In recent years, a wide variety of molecular sieves have become available. As mentioned earlier, it is possible to select the adsorption target by controlling its crystallinity. In most cases, adsorption is possible under conditions where the effective diameter of the molecule is <0.3 nm, <0.4 nm, or <0.5 nm.
If all you want to do is to remove moisture, you only need to select those with <0.3nm and it is possible to create an ultra-low humidity atmosphere with a dew point temperature of -76°C or lower (moisture content: 1ppm or lower). A molecular sieve that has absorbed moisture can be regenerated and reused by flowing inert gas or by vacuum heating.
3. Oxygen removal in Glove Boxes
Removing oxygen is also important when an anaerobic environment is required or when handling materials that are highly reactive to oxygen.
Two types of catalysts can be used to remove oxygen: oxygen adsorbents such as nickel and copper and precious metal catalysts such as palladium and platinum.
When oxygen adsorbents are used, an inert gas containing several percent hydrogens must be passed through the catalyst to regenerate it, whereas precious metal catalysts do not require a regeneration gas during regeneration. Although the introduction cost of precious metal-based catalysts is higher, they are safer and have lower running costs because they do not use hydrogen-mixed gas.
4. Points to note when using a Glove Box
Due to the sealed nature of the glove box, dirt tends to accumulate inside the glove box due to reagents, etc. Therefore, it is necessary to clean the inside of the glove box to prevent contamination.
In addition, although the glove box can create an atmosphere of less than the ppm order in terms of moisture and oxygen, the environment deteriorates rapidly if only a small amount of air is introduced. To maintain a strict environment inside the glove box, it is important to remove moisture and oxygen properly when reagents are placed inside the glove box and to perform regular maintenance to prevent holes in the gloves.