pH

In 1986 Hanna Instruments revolutionized the way pH can be measured with the introduction of the pHep® (pH electronic paper). This tester brought the electronic pH measurement to the masses. It allowed farmers, students, and many other users access to a pH meter that was simple to use and very accurate. The meter was also very affordable with a price point less than $50.00.

Since the introduction of the pHep, Hanna Instruments has been at the forefront of innovating the tester technology. Our innovations include the first tester with a replaceable pH electrode, the first combination testers that can measure multiple parameters, the first with a large multi-level LCD that shows both pH and temperature readings, and now to an extensive line of application specific testers that are optimally designed for difficult samples including cheese, meat, bread, wine and beer, to name a few.

In 2015, Hanna Instruments was the first manufacturer to incorporate Bluetooth^® LE technology into a pH electrode. This innovation allowed for wireless measurements to be performed. All readings are transmitted directly to compatible Apple^® or Android^® device running the Hanna Lab App. An advanced measurement system is created with the use of a smart device and Halo pH electrode. This measurement system rivals many portable and benchtop meters available on the market with advanced features including:  

• Five point calibration
• Good Laboratory Practice (GLP) for tracking calibration information
• Data logging and graphing
• Ability to email and share data
• Built in temperature sensor for automatic temperature compensation (ATC)
• Hanna’s unique CAL Check for identifying issues with the probe

All Halo probes are compatible with edge^blu tablet style pH meters. We offer a variety of Halo pH probes and each are built based on the intended application which is critical to obtain accurate, reliable measurements.

Portable meters come in a variety of models based on the specific requirements required. Most meters fall into two families.

Features found in portable meters include:

• Application specific versions
• Supplied complete including solutions and a carrying case
• Choice of pH electrode connectors including BNC and waterproof DIN

Benchtop meters are the workhorse in the lab. The meters we offer can range from basic benchtops to research grade versions with custom configuration ability for many aspects of pH measurements. There is also the edge family that is a crossover tablet sized meter that can be used as a benchtop or as a portable.

Meters Options Include:

• USB Ports for transferring logged data
• CAL-Check to identify issues with the pH electrode during calibration
• ISE measurement modes with direct concentration readout

Maintenance solutions are very easily overlooked but they are an important of the measuring system. Maintenance solutions include both storage and cleaning solutions.

Storage Solutions

The sensitive pH glass must be hydrated for an accurate measurement. A hydration layer can take hours to completely form. The junction of the reference cell also needs to be hydrated so that ions can move freely from the inside of the cell to the outside. Storage solutions are manufactured to be able to maintain the hydration for the probe while minimizing changes to the reference cell composition.

Cleaning Solutions

The sensitive pH glass must be clean for an accurate measurement. A build up on the glass will change the measured potential in the solution. This build up can be hard to discern with the naked eye but has an impact on the measurement. If a probe is calibrated when there is a coating and the coating changes in the solution then the calibration is no longer valid and measurements not accurate. It is important to have a regimen to periodically clean the pH electrode to maintain it in the optimal condition. We offer a variety of solutions including general purpose and ones specific to the application. Solutions are available in bottles and single use sachets.

At the heart of the potentiometric pH measuring system is the combination pH electrode. A combination pH electrode includes both the indicating sensor made of pH sensitive glass and the reference cell used to generate a stable mV potential. Each have their own design elements that make them ideal for a specific application.

The indicating pH electrode can be made from a variety of different glass types. Glass that is suitable for low temperatures (LT), high temperatures (HT), general purpose (GP) and hydrofluoric acid resistance (HF) are the four types of glass that we use in making a pH electrode. The glass is hand blown into conic, flat tip, bullet and spherical shapes. Each shape has its’ own benefit to an application.

A critical part of the pH measuring system is the reference half cell. In order to provide a steady reference potential the type of junction material is an important decision when building a probe for specific applications. Ceramic junctions are easily fused with glass and are commonly used. For low conductivity samples a probe can have multiple ceramic junctions for a higher flow rate. For food applications in which there is a high solids content a viscolene hard gel is the interface between the sample and the reference cell. This type of junction is referred to as open junction and is resistant to clogging. Other junctions include a removable sleeve design to disassemble and clean, ground glass with a movable sleeve for cleaning, and junctions made from cloth or PTFE materials.

The overall body shape of a pH electrode can be in a variety of shapes, sizes and materials. There are probes with a very small in diameter that can measure as little as 100 μL and very long to be used in an Erlenmeyer flask. The body can be made of glass, PEI or titanium. Each having their own benefit based on its’ intended use.

Connector Types

• BNC – Universal common connector
• Quick Connect DIN
• Digital – 3.5mm
• Digital with matching pin – 3.5mm
• Bluetooth

Hanna Instruments offers a variety meters that are used to monitor and/or control measurements in real-time. The meters come in a variety of formats including meters with built-in dosing pumps, transmitters and process controllers.

Controllers are available with on/off control and advanced PID (Proportional Integral and Derivative) control. Out put signals include basic 4-20 mA to advanced RS485 that allows up to 32 devices to be connected in parallel to a remote monitoring device such as PC, SCADA and PLC units.

The quality of a calibration buffer is often overlooked when calibrating a pH electrode. Many users make very important decisions based on the measurement obtained but overlook the importance of the quality of the buffer used when calibrating their meters. The most important aspect in obtaining an accurate measurement is the quality of the buffer that is being used. It is the reference point for the electrode response when testing a sample. The measurement is only is as good as the buffer.

At Hanna, we not only make the bottle, but also formulate and manufacture the buffer that goes in it. All buffers are produced in accordance with ISO 3696/BS3978 standards using high purity salts, deionized water, certified weight-checked balances, and Class A glassware in a temperature controlled environment monitored with certified thermometers. For our basic buffers the reported values are accurate to +/- 0.01 pH @ 25°C and are traceable to NIST Standard Reference Materials (SRMs). The can be purchased with or without a certificate of analysis. Hanna also offers millesimal buffers that have reported values are accurate to +/- 0.002 pH @ 25°C.

Buffers can be purchased in a variety of sizes and packaging. They can be purchased in single use sachets that are ideal for the user that works in the field or for someone that uses the meter infrequently. We also offer buffers that are dyed for easy identification for those that are calibrating to multiple points frequently.

Buffer Options

• Basic buffers with +/- 0.01 pH accuracy in bottles or sachets
• Technical buffers with +/- 0.01 pH accuracy and supplied with COA in bottles or sachets
• Millesimal buffers with +/- 0.002 pH accuracy and supplied with COA in bottles or sachets