Wet mounts are a fundamental technique in microscopy, allowing for the examination of specimens in their natural, hydrated state. This method involves suspending a sample in a liquid medium between a microscope slide and a coverslip. It is particularly useful for observing live microorganisms, such as bacteria or protozoa, enabling the study of their movement and behavior. The simplicity and speed of preparing a wet mount make it a widely adopted practice in various scientific and clinical settings, including the rapid diagnosis of certain infections.
Gathering Your Materials
Preparing a wet mount requires several materials. A clean microscope slide, typically a standard glass slide, serves as the base for the specimen. A thin, square piece of glass or plastic called a coverslip is placed over the sample and liquid, helping to flatten the specimen and protect the microscope’s objective lens. A dropper or pipette is used to precisely add the liquid medium, often water or a physiological saline solution, to the slide. Finally, the specimen itself is needed, ranging from pond water containing microorganisms to plant tissue or cheek cells.
Step-by-Step Preparation
Preparing a wet mount involves a sequence of careful actions to ensure optimal viewing. First, place a small drop of liquid medium, such as water or saline, in the center of a clean microscope slide. The drop should be slightly smaller than the coverslip to prevent excess liquid from causing it to float. Next, using tweezers or a similar tool, gently transfer the specimen into the liquid droplet, ensuring it is fully immersed. If the specimen is dry, like a thin section of onion skin, add it to the slide first, then place the liquid drop over it.
Next, carefully position the coverslip. Hold the coverslip at a 45-degree angle, touching one edge to the liquid droplet. Slowly lower the coverslip until it rests flat on the slide, allowing the liquid to spread evenly underneath. This angled approach helps push out air, minimizing air bubbles that can obscure the view. Finally, use a paper towel or absorbent tissue to gently blot any excess liquid from under the coverslip’s edges. This ensures the coverslip remains stable and prevents it from sliding around during observation.
Achieving Clear Observations
Achieving a clear view under the microscope often requires addressing issues like air bubbles. The angled lowering technique effectively prevents many air bubbles. If air bubbles still appear, gently tapping the coverslip with a blunt object or carefully lifting one edge with a fine needle and repositioning it can help dislodge them. Some mounting media reduce air bubble formation, and hydrophilic slides can promote smoother liquid spread.
Wet mounts can dry out over time, especially with prolonged observation. To prevent evaporation and extend observation time, the edges of the coverslip can be sealed. Common sealing agents include clear nail polish or petroleum jelly (Vaseline). Applying a thin line of sealant around the coverslip’s perimeter creates a barrier, preserving the liquid medium and specimen hydration.
Safety and Cleanup
After observation, proper safety and cleanup are important. Always handle glass slides and coverslips with care, as they can break and create sharp edges. Wearing appropriate personal protective equipment, such as gloves, is advisable, especially with biological specimens, to prevent cross-contamination. After use, slides with biological specimens should not be disposed of in regular trash.
Biological waste, including slides with samples, should be treated as potentially hazardous. Many laboratories use chemical disinfection, such as soaking slides in bleach solutions, or autoclaving to sterilize them before disposal. Contaminated slides should be placed in designated biohazard bags or puncture-resistant sharps containers. Always consult local waste management guidelines or institutional protocols for disposal of biological specimens and broken glass to ensure safety and environmental compliance.