Measuring the pH of small volume samples is a critical task in various scientific fields, particularly in life sciences and chemistry. The challenge lies in the limited amount of sample available, which can be as little as a few microliters. Traditional pH meters are not suitable for such small volumes due to the size of their electrodes. However, advancements in sensor technology have made it possible to measure pH in these microsamples accurately.
Understanding pH Measurement Challenges in Microsamples
When dealing with small volume samples, the primary concern is the potential alteration of the sample’s properties due to the introduction of the sensor. This is because traditional sensors are designed for larger volumes and can significantly disrupt the sample’s environment.
Selecting the Right Sensor
For microsamples, it is essential to use a micro pH sensor with a very small membrane and low junction. These sensors are designed to minimize sample manipulation and avoid introducing errors into the pH results. For example, METTLER TOLEDO offers a range of micro pH sensors, such as the InLab Nano, InLab Ultra-Micro-ISM, and InLab Micro Pro-ISM.
Comparison of Micro pH Sensors
| Sensor Model | Membrane Size | Junction Type | Suitable Sample Volume |
|---|---|---|---|
| InLab Nano | Small | Low | < 10 μL |
| InLab Ultra-Micro-ISM | Very Small | Low | 15-25 μL |
| InLab Micro Pro-ISM | Small | Ceramic | 20-500 μL |
Best Practices for pH Measurement in Microsamples
- Minimize Sample Disturbance: Use a sensor that can measure the pH without disturbing the sample volume.
- Temperature Control: Ensure that the sensor and the sample are at the same temperature to avoid errors.
- Calibration: Regularly calibrate the sensor to maintain accuracy.
- Cleaning: Properly clean the sensor to prevent contamination between measurements.
