About the Starter Series
Accurate and precise measurement has been our main focus since our inception in 1907. After more than a century of developing balances that have provided the reliable and precise weight determination that is essential to laboratory applications, OHAUS is proud to now o er our expertise in measurement in a line of electrochemistry products.
The Starter Series includes pH, reference, oxidation-reduction potential (ORP) electrodes, as well as conductivity, dissolved oxygen (DO) and temperature probes that can be used in conjunction with our bench and portable meters. This catalog contains essential information regarding OHAUS' portfolio of Starter sensors, including product speci cations and sample types they were designed to measure. In addition to the sensors, information regarding accessories such as conductivity and pH solutions used for calibration, are included.
Basic Theory of pH
pH is a one of the most commonly measured parameters in chemical and life sciences research, as well as is many di erent industries, including water and wastewater treatment, food technology, environmental protection, production and agriculture.
pH is de ned as the negative logarithm of the hydrogen ions concentration in the sample:
pH = -log [H+]
pH provides a convenient way to compare the relative acidity or alkalinity of a sample at a given temperature.
pH electrodes produce di erent mV values in solutions with di erent pH. Ideally, at 25°C, a pH electrode should produce a slope of 59.16mV per 1 pH unit.
Electrodes for pH Measurement
pH measurement is usually conducted using a combination electrode that consists of a pH-sensitive glass electrode that is sensitive to hydrogen ions present in the sample as well as a reference electrode that has a constant potential value.
A potential is developed on the membrane surface when a pH electrode comes into contact with a sample.
pH meters measure variations in the potential and convert it directly to a corrsponding pH value, according to the Nernst equation:
E = E0 + (2.303RT/nF)log[H+]
pH measurement is sensitive to temperature changes. However, at a pH of 7, temperature will not have an e ect on the potential of the is known as the isopotential point. OHAUS' 3-in-1 electrodes are convenient tools that contain a built-in temperature probe that can be used together with a meter to compensate temperature changes without application of any extrernal temperature probe.
Maintenance and Storage of pH Electrodes
pH electrodes are delicate measuring instruments that require proper care and maintenance to produce accurate and reliable results as well as to ensure a long usable life.
If an electrode is not in use always keep it moist by placing the electrode's glass bulb in the storage solution (3M KCl). Do not store the electrode in distilled or deionized water as this will cause ions to leak out of the glass bulb and reference electrolyte, which can cause a slow response and damage the electrode.
Electrodes may be shipped with either protective caps or in electrode soaking bottles to prevent cracking or scratching and to keep the glass bulbs moist. Gently remove the electrode from the storage bottle and rinse it with distilled water before use. For long-term storage, always keep the electrode in the bottle in enough storage solution to cover the bulb. Replenish the bottle as needed.
Specifications ST350:
Item Number: 30129354
pH Range: 0 to 14pH
Temp. Range: 0 to 100 oC
Shaft material: Glass
Internal Reference Type: Ag/AgCl
Refllable/Non-Refillable: Refillable
Reference Junction Type: Annular ceramic
Refilling Reference Electrolyte: 3M KCl solution
Dimensions (Shaft): 120 x 12 mm
Cable Length: 1m
Temperature Sensor: Yes
Connector: BNC Cinch
Application: 3-in-1 re llable pH electrode, with integrated temperature probe. Suitable for normal samples.
