Titration is a common laboratory technique to help determine the concentration of an unknown concentration of a chemical in the solution. It involves adding a solution of known concentration slowly to a fixed volume of the solution until the endpoint is achieved. The endpoint is indicated by the color change or precipitation formation of the indicator used. The known solution (titrant) is filled in the burette and released slowly to a known volume of the unknown solution (analyte) until the titration reaction is complete.
However, as easy as it sounds to perform titrations, there are several factors that can cause errors in titration findings. The errors include either endpoint error, incorrect burette reading, mistaken concentration values, and faulty technique.
Here are the top error sources in manual titration and how to avoid them.
Choosing a wrong indicator
One of the most common human errors in titrations is choosing the wrong indicator. There are several different indicators used in acid-base titrations and you can unintentionally choose the wrong one.
The pH value of the acid base titration endpoint depends on the acid dissociation constant (Ka). If a strong base is titrated by a strong acid, the pH value of the endpoint is at 7. The titration of a strong base with a weak acid moves the endpoint to the alkaline range, however, the titration of a strong acid with a weak base shifts the endpoint to the acidic range.
The common pH indicators used are Phenolphthalein, Bromothymol blue (BTB), Methyl red, Bromocresol green, Methyl orange, and Crystal violet. Each provides a different color change at the endpoint. Therefore, it is essential that you choose the correct indicator for your titrations. Fortunately, most SOPs and standards specify an indicator. So, follow the instructions, and you are on the safe side.
Endpoint error
The endpoint of a titration experiment is when the reaction between the two solutions has stopped and is marked by the color change of the pH indicator used. For the acid-base titrations, the indicator color may first lighten before changing completely.
The problem really starts when you try to recognize the endpoint. Also, each person notices color slightly differently, which affects the outcome of the experiment. If the color has changed slightly, you tend to add more titrant into the solution, overshooting the results.
Misreading the burette volume
The accuracy of titration requires exact measurement of the volume of materials in use. However, the markings on a burette can be easily misread. One can misread the volume in the burette by looking at the measurement from an angle. From above, it can seem like the volume is lower, while from below, the apparent volume looks higher.
The solution in the burette forms a concave curve, and the bottom of the curve is used to measure the correct volume. The more your line of sight deviates from the horizontal, the more inaccurate reading you take, and the result is also incorrect. To get the correct burette reading, stand on a footstool and make sure that you read the meniscus value horizontally.
How to improve accuracy in titrations?
So, how can you eliminate the errors in titration experiments? The solution is to use an electronic burette. With electronic burettes, all you need to do is fill it with the titrant and then press a button. The device has an electronic display, an electronic control panel, and motor-controlled piston movements that eliminate all the problems of the manual burette. Using an electronic burette eliminates the human errors in the titration experiments making them more precise and accurate.
Microlit E-Burette is an advanced motor operated burette with various features and functionality to perform accurate titrations. Moreover, it is designed with ergonomics and intuitive handling in mind. For more information and to buy the product, visit us now.