When you need to create a lab within a lab, a glove box is a particularly versatile solution that can protect the safety of the user, and the integrity, purity, and stability of the sample or procedure that needs to be sequestered from the adulterating influence of the outside world. This versatility is underlined by a wide array of options and controls to gauge access, volume, temperature, and atmosphere.
First of all, a glove box is most obviously what it says it is—a box that can be hermetically sealed against unwanted intrusion, with entry ports for gloved hands to manipulate samples or equipment inside. However, there are two basic types of laboratory glove boxes, the functions of which dictate their situational utility. Containment boxes serve the primary purpose of removing hazards for the user by protecting against the escape of toxic or pathogenic materials, encapsulating them in air-tight environments where they can be safely manipulated. Isolator boxes deliver inert gas in controlled atmospheres specific to experimental or manufacturing protocols where product quality is dependent on specific parameters of humidity and pressure.
Containment glove boxes provide airflow via HEPA or ULPA filtration. They can recycle and recirculate a controlled gas atmosphere internally, often combining with a blower/impeller to function in a closed loop. Alternatively, a single-pass or open-loop box creates one-way airflow using an inlet filter to incorporate ambient air and remove particulates before it encounters a sample. An exit filter then captures fine particles before exhausting purified air back into the room. Combination boxes allow for both closed- and open-loop configurations with adjustable valves. One specialized containment box is the anaerobic chamber for large-scale, controlled culture of up to hundreds of microbial plates, commonly using a chemical catalyst to stimulate removal of ambient oxygen.
Isolation glove boxes offer a diverse approach to controlling internal conditions, and to optimizing use of resources, especially inert process gases. For this purpose, the most common, one-size-fits-all solution is the standard isolation box. Laboratory workflows and the chemistry of samples manipulated or generated dictate the most appropriate construction materials, which include:
- Acrylic, which can be cost effective but narrowly applicable because of susceptibility to damage from alcohols and chemical cleaners
- Non-dissipative polyvinyl chloride (PVC), which can be used more broadly with corrosive materials and alcohols
- Static-dissipative PVC, which repels particulates, maintaining the highest levels of internal cleanliness, and can augment the capabilities of a cleanroom used in manufacturing or assembly
- Polypropylene, which has the highest level of chemical resistance.
Finally, stainless steel boxes come in many different configurations, with broad chemical compatibility, impermeability, and resistance to moisture and heat. Moreover, stainless steel boxes feature comparatively straightforward cleaning and sterilization, often including removable and autoclavable doors and individual parts.
“Glove box users can exert further environmental control by setting, monitoring, and modifying temperature and humidity.”
Within the boxes themselves, atmospheres can be customized by back-filling with gas, typically nitrogen, although argon is also common. The combination of glove box, airlock, vacuum pump, and gas port, with associated gauges and monitors, allows fine control of relative humidity and oxygen content. These can be employed in different contexts to create either positive or negative pressure. For example, a compounding aseptic isolator uses positive pressure to create a sterile environment for pharmaceutical combination and packaging, and can be certified to ISO Class 5 cleanroom standards. Negative pressure conditions can similarly be used to secure containment for sensitive samples, particularly toxic or radioactive ones. In pressure control systems, a fluctuating pump removes air every cycle until it reaches a setpoint, and the system can back-fill with gas. Continuous pump fluctuation can extend operating life by avoiding disruptive stops and starts, and a dual purge system using an automatic relief or bleed valve can maintain a positive-pressure environment while conserving gas.
Glove box users can exert further environmental control by setting, monitoring, and modifying temperature and humidity. For high-relative humidity (RH) applications, a drop in RH triggers specialized monitors to activate a heater and solenoid valve to release water vapor into the internal space. For procedures within normal low-RH ranges (one to five percent), several options are available, including desiccant drying systems, although a manual gas flow meter is a cost effective and accurate option for small systems under frequent single-user supervision. An automatic gas purge system, however, mitigates user error and maintains desired humidity levels while conserving more gas over time, and is therefore the best solution for larger instruments with multiple users. For applications requiring ultra-low humidity (less than one percent RH), a zirconium oxide or fuel cell sensor can detect oxygen with sensitivities in the parts per million range.
Filtration and gas purge systems to mitigate particulate and oxygen contamination can be combined with temperature control systems that cycle the internal space between hot and sub-freezing setpoints. This is particularly useful in accelerated and controlled shelf-life or stability testing of compounds generated at production scale. Alternatively, a process gas heater can deliver exact temperature control without contacting the purge gas itself; for instance, to preheat or dry components to high temperatures before they are baked or welded.
Finally, glove boxes offer options for leveraging space and mobility, with solutions for smaller laboratories, traveling back and forth between laboratories, or even taking the lab on the road for field work. For example, a standard isolation box is also available in a compact format. With significantly reduced volume and glove ports on opposing sides, a compact box maximizes the use of internal space, although it is still adaptable to airlocks, vacuum pumps, and gas ports. A portable version can be placed on a table with casters to move process or sample isolation from laboratory to laboratory. And lastly, you can take the laboratory with you into the field, even in your suitcase, with comparatively low-cost polyethylene collapsible and inflatable glove bags.
For containment, isolation, user protection, and atmospheric control, diversity of laboratory glove boxes, in various sizes and configurations, provide attractive solutions to create a lab within a lab.