1.1. Environmental Analysis of Organics in Water

In this lecture, we are going to talk a little bit about the analysis methods for organic and inorganic chemicals there are in water, sediment, and other matrices. This is the general pre-analysis method. Analysis method, we just have an overview of the analysis method again.

This portion introduces the lecture's focus on analyzing both organic and inorganic chemicals present in various environmental matrices, such as water and sediment. The aim is to provide an overview of the general methods used to analyze these substances, which will be detailed later in the lecture.

Think of this as preparing for a cooking class where you'll learn different recipes. Before diving into the meals, the instructor will first discuss the basic cooking techniques that will be used throughout the course, ensuring that everyone has a foundational understanding.

So, let us say we have a sample of water which has some analyte. When we say an analyte here, we are looking at multiple analytes, but our representation will be this A which is one analyte. So, for the analysis the general flow of the information is as follows. This A needs to be extracted from the water or any matrix into an extract and then from here it needs to be transferred to an analytical instrument.

This segment discusses the steps involved in the analytical process. An 'analyte' refers to the substance being measured (represented as A). The procedure begins with the extraction of the analyte from the water sample, transferring it into a form suitable for analysis, which usually involves transferring it to an analytical instrument designed to measure its properties.

Imagine trying to measure how much sugar is in a cup of coffee. First, you need to take some coffee (extraction) and then put it into a device that can tell you the sugar content (the analytical instrument). You can't just measure it straight from the cup.

The reason we have to do this is very often you cannot take the analyte A directly to the analytical instrument, this is not possible. ... if you want to measure temperature of air or relative humidity of air or some few chemicals in air, you have a probe that is available commercially and you can just show it in the atmosphere, in the air or water and it will give you things like this.

This part explains the limitations of direct measurement of analytes. For certain compounds in samples like water, it is not feasible to measure them directly with analytical instruments. Instead, specialized methods of extraction are necessary to convert these samples into a more manageable form for analysis.

Consider trying to weigh a tiny object using a large scale — it won't work effectively. Instead, you would place the item on a plate that can be weighed more accurately, much like extracting a chemical into a suitable medium for analysis.

The other reason why we would like to extract something from water into a solvent and then take it to an analytical instrument is also for purposes is that we have discussed something called the sensitivity or the minimum detection limit.

This section highlights the significance of sensitivity in analytical methods and how the minimum detection limit (MDL) affects the ability to measure low concentrations of analytes. If the concentration of the analyte is below the MDL, it can lead to inaccurate readings or a failure to detect the substance entirely, leading analysts to increase the concentration through extraction techniques.

Imagine you are trying to find a specific fish in a vast ocean. If you use a small net (low sensitivity), you may not catch any fish at all. If you can find a way to concentrate your search area or increase your catch size (by extraction), you have a better chance of noticing that one specific fish.

So, in a different view of this if I look at the calibration... we call this a region 3. If rhoA2 in 1, it needs to be reduced, concentration has to be reduced to bring it to region 2 and this we do by dilution.

This part explains the concepts of dilution and concentration as strategies used in preparing samples for analysis. When the concentration of an analyte is too high or too low, adjustments are made either by diluting the sample or concentrating it to ensure readings fall within a measurable range.

Think of a fruit juice that tastes too strong. If you add water, you dilute it to make it palatable. In analytical methods, if the concentration is too high, one might dilute it prior to analysis to obtain accurate results.

So therefore we take 100 milligrams... is a practical guideline in designing the extraction process.

Here, the concept of solvent extraction is introduced as a method for transferring analytes from water to a different medium. The choice of solvent is crucial, as it needs to have a higher affinity for the analyte than water, ensuring effective extraction.

Consider trying to soak up liquid using a sponge. If you use a sponge designed for a thin liquid, it will absorb much more efficiently than a solid piece of fabric. Likewise, the right solvent is needed to efficiently extract the target analyte from the water.

What method of extraction is called as a liquid-liquid extraction where you add a solvent and then shake it...

This segment details various extraction methods, chiefly focused on liquid-liquid extraction. This process involves mixing the water sample with a solvent, allowing the analyte to migrate into the solvent phase, thus separating it from the aqueous phase.

Think of it as mixing oil and water. If you pour oil into water, it will separate and float on top. If you mix them vigorously, the oil can dissolve a bit in the water, just like how the analyte can move into the solvent.

The other kind of more recent one is called solid-phase extraction or solid phase. ... liquid-liquid extract involves the physical operation between 2 liquids.

This section presents solid-phase extraction (SPE) as an alternative to liquid-liquid extraction. SPE uses a solid adsorbent to capture the analyte from large volumes of water, allowing for easier handling and reduced risk of sample loss during extraction.

Imagine trying to pick fruit from a field. Instead of carrying numerous fruit in your hands (liquid-liquid extraction), you could use a basket instead (solid-phase extraction) that makes it easier to handle and transport the fruit without losing any.

One of the things you have to understand that during the extraction, there are so many of these steps that are present here that there is always a possibility of loss of analyte during different processes...

This chunk discusses the need for recovery tests to ensure that the extraction processes are working effectively and to quantify losses at each step. Recovery tests allow for evaluating the efficiency of the procedure and adjusting methodologies accordingly.

It's much like testing a new recipe. If you keep losing ingredients at different steps (like burning something), you need to rethink your technique and track where in the process you are losing those ingredients.

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