Colorimetric Analysis and Camera Phones
At one time, the only way to colorimetrically analyze a solution was with complicated and expensive equipment such as spectrophotometers and other advanced instruments which would cost an individual thousands of dollars. Nowadays, anyone can use their smartphone and common household items to perform sophisticated colorimetric analyses without needing a single item that costs more than $10. If you’re interested in learning how to perform this type of analysis on any substance using your smartphone, then you’ll want to continue reading below!
What Is Colorimetric Analysis?
Colorimetric analysis refers to a quantitative technique used to measure the concentration of a given substance in a solution. This allows quantification of substances such as water and chemicals on metallic surfaces and their corresponding contribution to corrosion rates. One way colorimetric analysis can be performed is by taking pictures of colors formed on your samples, allowing you to do chemical analyses using regular camera phones. Doing so is quick, simple, cheap, portable and it can help develop analytical methods that are easy enough for routine laboratory or even field use, making colorimetric determination an ideal tool for many applications such as diagnostics or quantification processes. With proper training and results from previous experiments one can visualize trends in these processes within seconds compared to hours spent in a lab testing hundreds of samples manually.
The first step in colorimetric analysis is preparing a calibration curve. To create a calibration curve scientists take multiple measurements at each wavelength and calculate curves using Beer’s law which relate the absorbance of light per volume of solution at certain wavelengths to concentrations of dissolved substances therein. More specifically, chemists generally use ultraviolet-visible spectroscopy (UV-vis), where they excite specific wavelengths light into absorption peaks for each substance present by passing light through samples containing known concentrations along with absorbents like quartz wool . The intensity of transmitted radiation provides information about transmission due to solute molecules being excited into higher energy states before returning to ground state after absorbing energy from light. This process leads to increased or decreased fluorescence or phosphorescence that can be measured based on how much light was absorbed... (see rest)
The second step in colorimetric analysis is visualizing results. In order to do so you need some sort of camera phone that can capture images at least 240x320 pixels resolution and save them as JPEG files. You also need software that allows you to convert these files into something readable such as PNG or TIFF format. Once you have your image files you simply open them up in any image editing software such as Photoshop or GIMP then go to Image -> Mode -> Indexed... This will give you a list of colors that are represented by numbers ranging from 0–255.
When Can I Use This Technique?
The process of colorimetric analysis is particularly useful in situations where it is not practical or possible to use a lab instrument. For example, reagents can be prepared and assays performed onsite so that preliminary results can be given quickly. This type of testing is often used in both product research and quality control, although there are many applications across a variety of disciplines. The key benefit of colorimetric analysis over other forms of laboratory testing is that it is quick and simple to perform, giving immediate results for variables such as pH value, heavy metal concentration and water purity. In addition, tests that involve fluorescence need only be carried out in daylight hours due to sensitivity towards ultraviolet light; thus colorimetry has a number of environmental benefits as well as cost-effectiveness benefits. As an important point of consideration, colorimetric analysis should always be validated before being put into practice because it does not offer quantification accuracy at low concentrations like some other methods do. However, when dealing with large quantities or very potent chemicals such as cyanide or phenol, accurate quantification is unnecessary because hazardous levels will result in highly visible reactions anyway. Another important note about using colorimetry: Because you’re relying on human perception to determine if a reaction occurs, you must make sure that your test subjects (or yourself) are reliable! Always repeat your test several times before making any decisions based off visual evidence alone. To learn more about performing colorimetric analysis, check out our guide.
Which Materials Can We Test?
In theory, any number of materials can be analyzed via colorimetry; it all depends on your experimental needs. As a simple rule of thumb, if you want to figure out how much water is in a given solution, you'll need an instrument that measures light reflected off of a surface (colorimeters do just that). If you're looking for something more specific -- say, chloride ions in seawater or sugar in a soft drink -- then your goal will be different and you may have to use specialized instruments such as spectrophotometers or potentiometric titration instruments. However, determining salt concentrations is typically done using colorimeters because they're relatively inexpensive and easy-to-use compared to some other methods. Most commercially available colorimeters cost around $5,000 USD and offer good accuracy for general research purposes. Some are also capable of quantifying certain chemicals by simply adding reagents to samples during experiments, which allows you to turn them into chemical analysis devices at a low cost. To learn more about colorimetric analysis, check out our post on Colorimetry 101 . To learn about what kind of tests you can perform with a smartphone, read our post on Colorimeter Apps . And finally, check out these posts from our friends over at Ocean Optics: Colorimeters 101 and Spectrometers 101.
How To Perform Colorimetric Analysis
Colorimetric analysis refers to a quantitative technique used to measure the concentration of a given substance in a solution. The dilution must be added stepwise, increasing each time by 10%. At each step, you will carry out a titration and measure its pH level. When all of your steps are complete, your results should look like Figure 1 below. I would also suggest taking pictures of these results for later review. Further study will reveal that as pH increases (that is, as you move from left to right in your figure), there is an increase in absorbance and therefore color change! Try varying various conditions such as temperature and solvent type (i.e., alcohol vs. water) for more practice! In order to perform any type of volumetric analysis, it is important to calibrate your sample first. In our case, we know our volume based on how much NaOH was required to reach a particular point on our curve; however, because we did not add everything at once (we stepped it up slowly), it is likely that we did not reach exactly 0.25 M NaOH at any point during our experiment. To account for small variations like these when making measurements or calculations involving molarity or other types of concentration units, you need to calibrate them first. You can do so using Beer's law: where A is absorbance, C is concentration, l is path length, λ is wavelength, and ε(λ) is extinction coefficient. If you were to take a plot of ln[A] versus ln[C], it would yield a straight line whose slope equals −ε(λ). This allows us to calculate what we call molar absorptivity (also known as extinction coefficient): where ε(λ) = –slope/intercept.
Testing - The Basic Procedure
The analysis is done using a colorimeter, which is an instrument that measures color. The basic procedure consists of five steps: (1) Preparation of working solution, (2) Testing, (3) Quantification, (4) Statistical treatment and determination of detection limit and precision and (5) Correlation. The next step was quantification. Since a standard curve had already been prepared for each enzyme or phosphate standard solution in advance it was possible to determine what concentrations have reacted by comparing their absorbance at 490 nm with one's already existing data on known concentrations versus absorbance values. Through interpolation we could then determine how much water sample has reacted in order to calculate how much sugar is present in beer. This process can be expressed mathematically as Beer's law where A=absorbance, C=concentration and λ=wavelength of light. This equation shows that if you know two variables you can solve for another variable provided all three are linear functions. In our case A is equal to absorbance and λ is equal to wavelength so if we know C (concentration) from our calibration curves we can solve for A (absorbance). We also need to know B in order to use Beer's law since B tells us what concentration corresponds with a given absorbance value which will allow us to find out how much beer has reacted when testing beer samples whose concentration may not be known. If we did not know B we would have to test every single beer sample until its concentration was found through trial and error. The last step was statistical treatment and determination of detection limit and precision. For our purposes a large amount of beer samples were tested multiple times for both enzymes and phosphates standards. After determining these results we used them to construct confidence intervals around our average results from which we determined how accurate they were.
Examples of Practical Applications
1. Determination of concentrations of reactive chemicals on surfaces and near surface layers using Beer’s law. By comparing colored visible light transmitted through liquid samples to an image captured by a camera phone, HPLC spectrometry can be used for real-time chemical analysis without specialized equipment. This is particularly advantageous for developing regions where expensive equipment is not readily available and if done accurately, allows rapid analysis on-site during disaster relief efforts. 2. Color changes in beer can be used as visual indicators of fermentation via pH titration values or alcohol content via densitometry techniques: Using camera phones or tablets, one could monitor beer quality remotely in various locations throughout its production cycle while taking into account other variables such as temperature or oxygen levels—key factors that affect flavor development in beer. 3. Detection of corrosive water conditions (e.g., high mineral concentration) using methods similar to those described above: In areas lacking adequate infrastructure for water purification, regular monitoring would allow early detection of corrosive conditions before they become severe enough to cause structural damage. 4. Early detection of food spoilage/spoilage due to bacteria growth or food poisoning: In areas lacking refrigeration capabilities, colorimetric analysis can be used as a non-invasive technique to detect potentially harmful bacterial growth based on color change in foods over time (e.g., spoiled milk). 5. Real-time monitoring of industrial processes: Similar to some examples mentioned above, camera phones or tablets can be used to monitor industrial processes in real time from remote locations. For example, detecting corrosion rates in oil pipelines or determining metal layer thicknesses in manufacturing environments are just two examples of how cameras might be able to assist engineers working at a distance from their facilities. 6. Emergency response applications such as detecting hazardous materials following disasters: Following natural disasters like earthquakes and tsunamis, it is often difficult for first responders to identify hazardous materials present at affected sites. While traditional methods require special training and equipment, simple visual inspection by untrained personnel may aid initial site assessment following major events. 7. Monitoring environmental pollution caused by heavy metals: Heavy metals have been shown to negatively impact ecosystems around mining sites. The use of camera phones coupled with suitable software can help quantify heavy metal contamination in soils and waterways around mining sites, providing valuable information for environmental cleanup efforts. 8. Monitoring air pollution levels over large geographic areas: Air pollution levels vary significantly depending on local weather patterns and population density. Monitoring air quality over large geographical regions has traditionally required highly sophisticated measurement systems which are typically unavailable outside developed countries; however, inexpensive mobile devices can be used to provide basic data about local air quality which can then be combined with meteorological data to create more accurate models of regional air quality trends. 9. Monitoring water quality in lakes and rivers: Water pollution is a serious issue in many parts of the world. With camera phones or tablets, water quality can be monitored on-site by trained observers to provide real-time feedback to public health officials. 10. Monitoring urban heat island effects: Heat islands are formed as a result of human activity (i.e., building and road construction) and are characterized by higher temperatures than surrounding areas. Although these effects are usually localized, monitoring urban heat islands can be useful for energy conservation efforts since more efficient cooling strategies can be implemented in hot spots (i.e., areas with higher ambient temperatures). 11. Monitoring air pollution levels over large geographic areas: Air pollution levels vary significantly depending on local weather patterns and population density.
Smartphone Colorimetric Analysis
The method for color analysis is called Beer’s Law, which states that transmittance of a given wavelength of light through a solution equals its concentration. By attaching a piece of colored glass to a smartphone camera lens, you are creating a colored filter. In certain circumstances, your camera will be able to pick up on wavelengths beyond what it can normally see (i.e., infrared or ultraviolet), but in cases where you are trying to analyze visible light, by placing red glass over your camera lens you will restrict the wavelengths allowed through and therefore be able to see only red. Place blue or green glass over your lens and suddenly you’ll be restricted to seeing only those colors, etc. This allows you to quantify how much each particular substance contributes to corrosion rates.
With practice, even if you don't have an advanced degree in chemistry, you'll soon learn how different substances contribute differently to corrosion rates based on their color alone. This knowledge can help determine what types of coatings are most appropriate for certain environments and situations. For example, if your coating is failing due to rusting from exposure to water and air—but it isn't discolored—you'll know that there's no need for an anti-corrosion coating since there's no actual corrosion taking place; rather just oxidation due to exposure without protection. So why waste money? Instead use a simple water-repellent coating instead.
Fun Terms to Investigate
Permanganate, photons, quantitative analysis, spectrophotometric, cuvettes.
