6.2. Summary of QA/QC Procedures

In general, the summary of the QA/QC procedures, the first and foremost we need calibration with standards. Then we need what we call us replicates for repeatability. Now this is repeatability of the entire process, which means samples, we must take sample replicate that will indicate several things. Sample replicates indicate the heterogeneity of the sample itself. This also indicates if your analysis procedure is consistent. So every time you do it, you should get similar results.

QA/QC stands for Quality Assurance and Quality Control, which are critical in environmental analysis. They ensure that the data collected during analysis is accurate and reliable. The first step in QA/QC is calibration using standards. Calibration involves comparing the measurements from the analytical instruments with known standards to ensure accuracy. Additionally, replicates of samples are taken to measure repeatability, indicating how consistent the analysis is across multiple tests. If the same sample gives similar results in various runs, it confirms that the analytical process is stable and the data can be trusted.

Think of QA/QC like a chef consistently making the same dish. To ensure the taste is always the same, the chef uses the same recipe (calibration with standards) and checks two or three times whether the flavor remains consistent with the last time they cooked it (replicates for repeatability). If the dish tastes different each time, it indicates there might be an issue with the ingredients or the cooking method.

Then we have to do a blank, a series of blank. So, every time you start an analysis, you start with a blank and then you start with a standard.

Blanks are essential in QA/QC procedures as they help identify contamination or errors in the analytical process. A blank is essentially a sample without any analyte present, allowing for measurement of background noise or contamination in the analytical instruments, glassware, or reagents. By running a blank before actual samples, analysts can see if their instruments add any signals or if there are any unforeseen contaminations. If the blank shows a reading above the detection limit, it indicates some form of contamination that could affect the accuracy of the sample analysis.

Imagine you are a painter. Before starting a new canvas, you test the paintbrush on an empty paper (the blank) to make sure there are no leftover colors that could spoil your new painting. If the test shows leftover paint, you know you'll need to clean your brush before starting. Similarly, in environmental analysis, running a blank helps ensure that the tools are clean and functioning properly to get accurate results.

Then we have, we do a recovery with many of this thing, yeah. In some cases we also use what is called as an internal standard.

Recovery refers to the process of measuring how much of the analyte remains after the entire analytical procedure as compared to the amount that was initially present. Calculating recovery rates helps scientists understand any losses that occurred during sample processing. For instance, if an initial concentration of a chemical in a sample was supposed to be high but was measured low after analysis, that indicates some analyte was lost, which can affect the interpretation of results. Sometimes, an internal standard is used, which is a known quantity of a similar substance added to the sample. This helps in adjusting for any losses as the behavior of the internal standard during analysis can indicate how much of the analyte was lost.

Consider a student taking a test where they expect to answer 50 questions correctly. If they find out later that they only managed 35 questions, they need to determine why that happened (this is like calculating recovery). To understand their performance, they might compare their scores from past tests (like using an internal standard) to see if they lost points due to misunderstanding a question or misreading the instructions.

So, to summarize this recovery for losses is blank analysis for this thing. There are different kinds of blanks.

During the analysis, contamination can lead to false positives or negatives, affecting the reliability of results. Various types of blanks are used in the QA/QC process to monitor contamination at different stages: method blanks check for contamination introduced in the analytical method, instrument blanks check for contamination from the equipment itself, and solvent blanks check the purity of solvents used. By identifying the presence of contamination early on with these blanks, analysts can correct the process to ensure that the analysis accurately reflects the sample's true condition.

Think about baking a cake. If you accidentally use a dirty mixing bowl, the batter could contain previous ingredients that could change the flavor (this relates to contamination). So, you would want to check your bowl to ensure it's clean before starting (using different blanks). Just as bakers need to monitor their tools for contamination to ensure quality results, environmental analysts do the same to safeguard their findings.

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