Measuring pH is important within a variety of industries, which can be measured in several ways. While both pH meters and pH paper are portable methods to measure a solution’s pH, pH meters provide more accurate results and color blindness is not an issue as results are displayed on a digital readable display. However, pH paper is a much cheaper and easier way to measure pH.
pH (potential of hydrogen) is the measurement of hydrogen ions in an aqueous solution. The pH scale is a negative logarithmic scale that ranges from 0-14, 7 being neutral, 0 being the most acidic, and 14 being the most basic or alkaline. An example of a solution that has a neutral pH value is pure water.
We cannot see ions with the naked eye, so testing the pH of solutions is important to determine pH levels. pH paper (litmus paper) and pH meters are very useful tools in quickly identifying the pH of a sample. Litmus paper is the old-school way of measuring pH using qualitative judgments to determine if a solution is acidic or basic (alkaline). However, for accurate and continuous measurements on a larger scale, pH meters equipped with pH probes are recommended, providing a more robust approach to pH testing.
A pH meter is an electronic piece of equipment to determine the pH of a solution. An electrode (usually glass) is attached to the meter, which measures the voltage. As pH meters and probes require calibration before use, they can be calibrated with a standard buffer solution that is input into the machine (or it can be done without a solution) giving an accurate result. The buffer solution commonly uses the following three pH levels: pH 7, pH 4, and pH 9.2/10.
A pH meter works by associating a voltage with a pH value. The more ions that pass through the membrane, the higher the pH value, and vice versa.
How Accurate Is A pH Meter?
pH meters use a computer or digital user interface providing you with an instant pH reading on a readable display, therefore, they are considered extremely accurate and durable as long as you store them properly and maintain them according to the manufacturer’s guidelines.
As mentioned, pH meters must be calibrated using a standardized buffer. A buffer allows the meter to associate the voltage of a solution with a pH value. pH meters may slightly differ, but they are usually all accurate to the hundredth place. pH meters can be affected by ion interference sometimes drifting from the calibration position, hence it is important to always calibrate your pH meter before use.
Some pH meters require to be plugged into an outlet, while others need batteries, which are commonly used in the field. pH meters accommodate different industries depending on the application. At Atlas Scientific, we have a range of pH sensors for different applications to meet your testing needs.
Advantages Of Using pH Meters
pH meters are simple to use and are not affected by human error such as color blindness. Some people may perceive color differently from others, or the true result. As pH meters use a readable digital display, they provide a much more precise result than pH papers and titration methods.
As pH meters are portable, providing quality precision readings wherever you need to test pH solutions is easy. They can be used in a controlled laboratory or used for environmental field-testing. If you will be in the field, small battery-operated pH meters are ideal for hauling to different locations.
Disadvantages Of Using pH Meters
pH meters cost a lot more money than pH paper strips, as a pH meter is a long-term investment to provide accurate pH readings. If you only need to take occasional pH readings such as in home aquariums, pH paper may be a better alternative.
Another disadvantage of using pH meters is maintenance. You will need to clean it regularly to avoid possible contamination of samples. As most pH meters contain a probe with a glass tip, these are extremely fragile so can be easily broken or damaged if exposed to corrosive substances.
Lastly, pH meters must be calibrated before use, which is vital for obtaining accurate results. If a pH meter is not calibrated properly, the results can be distorted. To prevent human error when using a pH meter, always refer to the operating manual for detailed instructions of use.
pH paper, or litmus paper, comes in strips that change color when it comes upon contact with a solution giving a pH reading. Each pH value has a corresponding color, which can be found on a standard pH chart.
Another advantage of pH papers is that they are easier and cheaper to use than a pH meter, and provide quick readings. pH paper also doesn’t require pre-calibration before use.
How Accurate Is pH Paper?
pH paper uses colors to indicate pH values, similar to a Galileo thermometer. pH paper is great for quick qualitative research, but if you require highly accurate quantitative research, you may want to invest in a pH meter. However, if you only need broad accuracy to one pH value or two, pH paper will be adequate.
Just a quick note: to obtain accurate results, someone that is not considered color-blind must read the results.
Advantages Of Using pH Paper
pH paper is a more simple, cheaper, and quicker way to obtain pH readings than a pH meter, which also does not require any pre-calibration. As they are small and do not require an energy source, they are a great portable way to measure the pH of solutions, wherever you’re testing.
pH paper and strips provide more precise pH results than liquid indicators such as the titration method. The paper changes color depending on the pH value, making it easy to read and record results.
Disadvantages Of Using pH Paper
Using pH paper has a great deal of uncertainty in terms of measurement. When using pH paper, as previously mentioned, the pH values are only accurate within a unit or two. pH paper is not designed for extreme pH values (whether it be high or low pH), so often they do not give an accurate reading like a pH meter.
This relates to resolution issues. As colors correspond to pH ranges not specific pH values, often values are in increments of 0.5 on the pH scale, so if you need a specific pH value, consider using a pH meter.
pH is not temperature-compensated, this can give inaccuracies to results if the sample is tested in a very high or low-temperature setting. Some pH meters can compensate for this change.
As pH paper is in contact with the surrounding air, and they are not washable, the possibility of sample contamination is higher than using pH meters.
If you are color-blind, working with pH paper can be difficult. Often, it can be difficult to differentiate the colors for someone that is not color-blind. For example, if the pH paper appears to be green, deciding which shade of green that is displayed on the box can be tricky. This proves much more difficult if you are red-green colorblind, therefore using a pH meter with a readable screen may be better.
Summing Up pH Meters & pH Paper
If you work in applications where low resolution and accuracy are sufficient, then pH strips are a great way to easily and cheaply measure pH in solutions. However, if you need high resolution and extremely accurate results, pH meters are the best option, and worth the investment.
Before choosing which pH testing method, consider the pros and cons of each and what industry you are working in.
Our goal is to help make measuring pH easy and accessible for you. If you have any questions regarding pH or the products we have to offer, please feel free to reach out to our world-class team at Atlas Scientific.