Autoclaves

Because autoclaves must be used properly to effectively decontaminate materials, it is important that trainees be instructed on their care and use. According to Rutty, autoclaving alone may not rid instruments or glassware of DNA, but proper autoclave sterilization would prevent contamination by enzymes with nuclease activity.⁰³

Heat Blocks

Laboratories may use a heat block or dry bath for heated incubation. For example, steps such as heat denaturation of amplified DNA product in a microcentrifuge tube may be conducted in a heat block in the amplification room or in a thermal cycler with appropriate settings. A heat block is often preferred for heating samples during extraction, as there is less risk associated with water seepage and contamination. When necessary, the temperature can be checked using a NIST traceable thermometer.

Hotplates & Magnetic Stirrers

Hotplates and magnetic stir plates are often used in reagent preparation. Analysts should be well versed in their care and use and to only use them when a reagent recipe specifically warrants. Laboratories may also use hotplates for heat fixing slides, so it is important that they be clean and in good working order.

Incubators

Laboratories utilizing certain types of biological screening tests, such as precipitin or Ouchterlony plates and/or radial gel diffusion assays for α-amylase, may maintain a laboratory incubator. These can be used to create an environment of optimum temperature and humidity for incubating assays or for storing warm reagents, such as those used in slot blot quantitation. Temperatures can be sustained at room ambient or higher, and trainees should be instructed in the care and use of incubators. Cleanliness is imperative in these environments given the propensity for microbial growth. When necessary, the temperature can be checked using a NIST traceable thermometer.

Thermometers

The majority of thermometers used in a forensic science laboratory are liquid in glass thermometers. Thermometers deemed critical by the laboratory should be calibrated using standards traceable to national or international standards. Oftentimes laboratories purchase thermometers that have been verified and calibrated against a NIST traceable source.⁰⁴ Specialized thermometers using shaped probes are also used for monitoring and calibrating of equipment such as heat blocks and thermal cyclers. Trainees should understand the appropriate application of thermometers, how to read them, and the importance of calibration proper use and safety.

Water Baths

Water baths are used for a variety of laboratory applications and include general-purpose, shaking, immersion circulating, boiling, high temperature, and low temperature water baths. Trainees should be made familiar with the types of baths available in the lab and their respective uses. Emphasis should also be placed on proper filling and maintenance. When necessary, the temperature can be checked using a NIST traceable thermometer.

Water Purification

It is important that a DNA analyst understand the effects of resistivity and total organic carbon level in monitoring water quality and when ultrapure, sterile, and/or deionized water is used. Using sterilized water in various stages of the forensic DNA analysis process is very important. Most laboratories employ a commercial water purification system, and these have outputs that alert the laboratory when filters and/or UV lights need to be changed.

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