4. Quality Control Measures

Therefore, the burden of the quality control and assurance lies with the analyst and the chemical analyst. So, there are a large number of procedures that are built into the analytical procedures. If you look at a standard method that as we are discussed, this quality control and this Q/QC procedures are inbuilt into the system.

Quality control (QC) is crucial in any analytical process. It ensures that the results obtained from environmental samples are reliable and can be trusted for important decision-making. Analysts must adhere to established QC measures, which are incorporated into standard methods. These procedures help in detecting and reducing errors that can occur during sample analysis.

Think of quality control in analysis like the safety checks performed on an airplane before takeoff. Just as these checks are crucial to ensure the plane is safe for flight, QC measures in analysis ensure that the results are accurate for environmental safety.

The possible analyte losses occur first in the transportation of the sample. Second, which occur in the storage, then in processing, the fourth in the analytical instrument itself or the chemical analysis instrument part of it.

Analyte losses can occur at various stages: during transportation of samples, in the way samples are stored, during the processing of those samples, and even within the analytical instruments used for testing. Understanding these stages is critical to minimizing loss and ensuring the integrity of the sample.

Imagine you are carrying a glass of water. If you walk quickly (transportation), keep the glass uncovered (storage), spill some while handling it (processing), or have a faulty glass that leaks (instrument), it will have less water than when you started. Each stage affects the amount of water left, just as it affects analytes.

One of the main first things is volatilization, which is evaporation of the sample, evaporation of the analyte from the water sample or the filter or anything.

Volatilization refers to the process where a substance evaporates from liquid samples into the air. This is significant for volatile compounds found in water samples, as these can easily escape, leading to inaccurate readings of their concentration. Minimizing exposure to air and using airtight containers are strategies to mitigate this effect.

Consider how perfume quickly disperses into the air after being sprayed. Just like the scent itself evaporates, volatile compounds in samples can escape into the atmosphere if not contained properly.

The second part of it is reaction. This reaction could be many things. Reaction could be biodegradation, it could be reaction with other entities in the system which is things which are already present in the sample.

Reacting substances can degrade or alter the analyte. Biodegradation, where microorganisms break down substances, is a significant concern. The timing between sampling and analysis can affect how much of the analyte is left, especially if the analyte undergoes chemical changes when exposed to other materials or environmental conditions.

Think about how a banana turns brown over time when left out. This 'reaction' is akin to how certain analytes can degrade or change when left untested for too long, affecting the accuracy of measurements.

Third one is adsorption. So, the adsorption occurs through any solid surface during the processing, collection and processing, and one of the solid surfaces that you can generally see is solid surfaces we are looking at adsorption is the container itself.

Adsorption occurs when analytes cling to the surfaces of containers or other materials during collection and processing. This can lead to a reduced concentration in the sample as the analytes are trapped on the surfaces instead of remaining in the liquid. Selecting appropriate container materials can minimize this loss.

Imagine syrup in a glass. If the glass is sticky or dirty, some syrup will cling to the sides instead of being consumed. Similarly, analytes can stick to the walls of containers, leading to less analyte available for measurement.

For example we are looking at organics. There is a general theory that rule of thumb that organics like to bind with other organics. Therefore, the collection vessel, this collection and storage containers should be inorganic.

When storing organic substances, it is advisable to use inorganic containers like glass to prevent adsorption. Organic materials in plastic can attract organic analytes, leading to higher losses. The choice of container material can significantly impact the reliability of the analysis.

Choosing the right bag for groceries: If you're buying fruits that release ethylene gas, placing them in a plastic bag can ripen them too quickly. Similarly, using the right container can prevent analyte loss during sample analysis.

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