pH Electrodes
One of the first pH electrodes is made of a glass bulb filled with strong electrolytes and has silver/silver chloride cells inside of it. The Ag/silver wire acts as a contact in this type of electrode. The original and modern types of pH electrodes haven’t changed much, but the advancements of modern technology have made it possible for new designs and improved types of electrodes to come into the picture.
Nowadays, pH electrodes are commonly known as combination electrodes. As such, what is this type of electrode?
Combination Electrodes
One of the main uses of combination electrodes is to measure the difference between the two sides of a glass electrode. Essentially, to measure this potential difference, there must be a closed circuit. Once the electrode is immersed in the test solution, the glass bulb will sense the hydrogen ions in the form of millivolts (mV). This is due to the positive charge innate among hydrogen ions. After which, the internal solution or electrolyte will pick up the mV signal from the glass bulb. The internal electrode will then receive the signal. Then, the mV reading is done through the meter which is then displayed in pH units.
Double Junction Electrodes
A double junction electrode is used when there is an occurrence of an electrolyte flow reversal. To protect the internal solution from contamination, a second or added junction is built into the electrode. Essentially, the double junction electrode provides an additional chamber between the tested solution and the reference electrode. Possible contamination from the test solution will have to go through the second chamber before it can get to the reference electrode. More than this, double junction electrodes last longer and work well in adverse situations.
Calomel Electrodes
Calomel electrodes are primarily made constructed from mercury and mercuric chloride which both have KCI electrolytes. One of the important uses of calomel electrodes is that it gives a longer service life to the electrolytes. Conversely, calomel electrolytes contain hazardous materials such as mercury which needs to be specifically disposed of with caution.
Ion Selective Field Effect Transistors (ISFET)
ISFET or also known as solid-state electrodes work with a silicon chip that is placed in contact with the test solution which helps to detect and measure the potential difference between the surface and the semiconductor material used. Essentially, ISFET electrodes are durable and easy to maintain for their longer service life. As they are made of steel, they are unbreakable which is useful when conducting pH monitoring.
Ion Selective Electrodes
ISEs are one of the types of electrodes that measure specific ion concentrations present in a solution on a regular and timely basis. These electrodes are composed of a sensor that converts an ion into an electrical potential during the entire process of dissolving the tested solution. Unlike the traditional pH electrode that only measures hydrogen ions, ISEs measure potential ions from many substances such as Ammonia, Cadmium, Calcium, and Copper. Essentially, ISEs are used in water treatment plants and other manufacturing facilities and laboratories which makes this type of electrode useful in 24-hour pH monitoring.
Frequently Asked Questions (FAQs)
FAQ #1: What is the difference between a Glass body electrode when compared to an Epoxy-body electrode?
Epoxy-body electrodes are suited to be used in fieldwork or any type of work that requires rough handling. These are made of glass bulbs that necessitate the caution to handle these electrodes with proper handling and monitoring. More than this, the plastic body limits the use of electrodes under high-temperature solutions and solvents.
FAQ #2: What is the difference between a refillable electrode from a gel-filled electrode?
A small amount of electrolyte solution that manages to leak through the junction and eventually into the test solution can be refilled using a refillable electrode through a fill on the port of its body. Essentially, this maintains accuracy and extends the longer service life of the electrode.
FAQ #3: What is the average life expectancy of an electrode?
There are many contributing factors that affect the life expectancy of an electrode. Generally, the average life expectancy of a pH electrode lasts from one to two years. Maintaining longer service life for electrodes means that proper maintenance and storage should be practiced.
