6.1. Common Analytical Instruments

Let me take an example of one of the analysis methods. So I have to give you an example of one of the analysis method before we go on with this. So, what we mean by sample volume, ok. What is the analytical instrument you are all familiar with? You can just name some and I will pick, what is the most commonly known analytical instrument? Example of an analytical instrument. GC. GC How many of you know what a GC is here, please raise your hands, okay. Next. HPLC. How many of you know what an HPLC is? Okay, less than half, how many, anything more? From high school you have done a lot of analytical instruments. UV, UV what UV? UV spectrometer. How many of you know what a UV spectrometer is? More number of people, but not all, okay. Turbidity meter, ah? turbidity meter. How many of you have seen turbidity meter? Six people. Next, anything? FTIR. Start from high school? Start from high school? Ah? FTIR, How many of you have heard of FTIR? Six people? Anything you have used from high school, what is the uh? pH meter Okay. Then, something more. Burette and pipette. Burette and pipette is not analytical instrument; it is a handling instrument. Microscope, microscope, okay. Weighing balance weighing balance. How many of you have used a weighing balance? How many of you have used weighing balance? please honestly raise your hands, then if you do not raise your hands, we will ask you to go back. All of you have used weighing balance, hopefully somewhere, weighing balance.

This chunk introduces the concept of analytical instruments used in various analysis methods. The instructor prompts students to name instruments they recognize, leading to an overview of common instruments like Gas Chromatography (GC), High-Performance Liquid Chromatography (HPLC), and others. The goal here is to establish familiarity with the tools that are pivotal in analytical chemistry, thus preparing students for further discussions on how sample volume and instrument choice relate to analysis methods.

Consider a chef preparing a dish. Just like a chef uses different utensils and tools (like a blender, a knife, or an oven) for various cooking tasks, scientists use analytical instruments to conduct different types of measurements and analyses. Each tool is designed for specific tasks, and understanding them is crucial for effective experimental outcomes.

So, we will start with weighing balance, okay. It measures mass. Weighing balance measures mass, okay. Now, let us say that we will do a simple measurement of total suspended solids. So, I have to I will describe what the total suspended solids method is and then based on this example, I will explain what we mean by, what we are trying to discuss here okay. So, we will go to the next page. We will do total suspended solids in water. So what we are measuring really is Rho 32. We are measuring solids in water, we are not measuring chemical concentration, we are measuring solids concentration in water.

This chunk focuses on the weighing balance, a fundamental analytical instrument used to measure mass. The discussion transitions to a specific application of the balance in measuring total suspended solids (TSS) in water. Here, the goal is to distinguish between measuring solids concentration and chemical concentration, guiding students to understand that in environmental science, measuring the amount of solids suspended in water is a common practice.

Think of a glass of muddy water. If you want to find out how much dirt is mixed in, you would use a balance to measure the amount of solid left after filtering the mud from the water. This measurement gives you a direct insight into the quality and cleanliness of the water, similar to how a chef weighs flour to ensure the right amount for a recipe.

So, what is the simplest way to do this? You simply want to measure mass over volume. So what are 2 measurements we need? One is the volume of this water. So, I can take a water sample, I can measure. If this says 1 liter, let us say 1 liter, I can fill up this water to 1 liter and I know that this is 1 liter, I know the volume, right. Let us assume that we know it is 1 liter okay, and then how do I measure the mass that is contained in this 1 liter? This is suspended, which means that, you know, if you take a snapshot of this, it will look like this, it will look like this. The mass is all suspended in the water. So, what do I need to do in order to measure the solids, suspended solids? Yeah, I need to filter.

In this chunk, the discussion emphasizes the process of measuring total suspended solids through a systematic sampling and filtration method. To determine the amount of suspended solids in water, you need to first know the volume of the water sample and then filter it to separate the solids from the liquid. This practical approach illustrates how physical separation techniques are employed in analytical chemistry.

Imagine making a cup of tea with loose leaves. After brewing, you use a strainer to separate the leaves from the liquid. Similarly, in this process, water samples are filtered to separate suspended solid particles from the clean water, allowing us to weigh the solids that are left behind, just like weighing the used tea leaves after straining.

So, what do we do in our example, coming back to our example, if you are not able to see a difference, what can you do to check if there is a difference. So, our TSS is m3 by V2, yeah. Let us say for example, let us say that the detection limit for a gravimetric balance, for a weighing balance is 1 milligram, this is below it, it cannot measure. The minimum it can measure is 1 milligram, right. Now I take 1 liter of water sample with a TSS of 0.5 milligram per liter. I am not going to see anything in the balance. My balance, let me say to be very clear, I will put it as 0.3. Sometimes this 0.5 will fluctuate and show up as 1, that we do not want that, we’ll use 0.3. I know this through some other methods, I have analyzed it, but if I put this I filter 1 liter in a filter paper and I put the filter paper, and I am going to register a weight difference mf1 minus mf0 is going to be 0.3 milligrams because I am using 1 liter of water sample. So in the instrument, I am going to be seeing 0, instrument will say 0, it is below the detection limit of the instrument.

This chunk introduces the concept of detection limits in analytical measurements. It explains how if the concentration of suspended solids (TSS) in a sample is lower than the detection limit of the weighing balance, the measurement may register as zero. This emphasizes the importance of understanding an instrument's sensitivity and the implications for accurate measurements in analytical processes.

Consider a person trying to hear a whisper in a noisy crowd. If the sound is too soft (below the person's hearing threshold), they won't even notice it's there. Similarly, if the concentration of a substance is below the detection limit of an analytical instrument, it won't be detected. Understanding this helps scientists choose the right equipment for their measurements.

So, this feature of sensitivity when you see sensitivity, when you look at instruments listing characteristics, specifications, you will see sensitivity and it is listed as a lowest concentration. The lowest theoretical concentration that the instrument can measure will be listed there. So, in the case of the balance is 0.00001 grams. It can detect 0.00001 grams okay. Whether it is useful to you or not is a different question, okay, but somebody has tested and say this is the minimum it can actually give you a sensitive reading, some reading, okay. How many of you have used a digital balance for your properly for your work? Few of you have used it, yeah.

This chunk details the concept of sensitivity in analytical instruments, focusing on the 'method detection limit,' which is the lowest concentration that an instrument can accurately measure. It explains how this limit is crucial for determining the reliability of the instrument's readings depending on the analysis being conducted. The discussion also emphasizes that each instrument may have different sensitivity levels based on its design and purpose.

Think of using a precision tool like a microscope. Just as a microscope helps you see tiny details that the naked eye cannot, sensitive instruments detect very small amounts of substances that standard tools might miss. For example, if one wanted to analyze the flavor of a gourmet dish, only a sensitive instrument could detect the subtle notes that contribute to its unique taste.

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