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Environmental Analysis Tips and Tricks for pH Measuring Techniques
Mettler Toledo (UK) has launched an email series of tips and tricks to help researchers and scientists to improve pH measurements in laboratories. pH measurement is a frequent task in a lab,the results of which are often dependent on the performance of the instruments used. While there are regular check- ups and calibration possibilities for your pH meters, but did you know that your measurements can be influenced by external factors, such as the surrounding temperature or the age of the buffer solutions. Did you know that there are cases where you measure the sensor and not the sample? Technique directly affects the success and repeatability of your experiments and fortunately there are a few simple tips that will greatly improve your pH measuring performance.
Diaphragm clogging: TRIS-based buffers can damage standard pH equipment, as the reference junction on conventional pH electrodes can clog when TRIS reacts with silver ions in the filling solution. This may also occur with protein in the buffer, such as BSA, eventually causing slow or fluctuating readings, or even entirely wrong results. To ensure reliable results and accurate buffer values choose an electrode specifically designed to be compatible with TRIS-based buffers.
Automatic and manual temperature compensation: Automatic temperature compensation (ATC) is most effective with sample volumes greater than 10 ml. Sensors with an integrated temperature probe allow ATC by the pH meter, whereas sensors without an integrated temperature probe require a separate probe. Manual temperature compensation is extremely accurate, but time-consuming. Always enter temperatures in the measurement settings of the pH meter, and adjust with every temperature change.
Store sample and sensor at the same temperature: Store the sensor with the samples, as the greatest accuracy is achieved when the pH membrane, reference system and sample are at the same temperature.
Measure the sample, not the sensor: With very small samples, the sensor can take so long to reach equilibrium that its temperature is wrongly interpreted as the sample temperature. Take the time necessary to ensure that you actually measure the sample temperature.
Use fresh buffers: Unopened buffers typically have a shelf life of 2 years, opened buffers Three to six months, and alkaline buffers (pH 10 or higher) one month, as their pH changes noticeably through contact with carbon dioxide in the air. Always use fresh buffer solution, store buffers in closed bottles and never use them after the expiry date.
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P3000 - New Digital Economy Polarimeter
Krüss (Germany) have developed a high-speed measurement that reduces measuring time of samples to only 1 second irrespective of the angle of the sample. Compared to other polarimeters, much time is saved during the measuring process.
The P3000 is an economy version of the P8000 and operates just as fast as its big brother. An intuitive touch screen with basic functions has been implemented as well. Measuring results are shown either in optical rotation or in the international sugar scale. Data can be exported to a printer via an RS-232 interface.
For industries – i.e. sugar industry – which don’t need more than 2 digits after the decimal point and perform standardised measuring, the P3000 can be excellent value for money.
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Merck Millipore (USA), the Life Science division of Merck, today announced the addition of its Elix Essential systems to the company’s existing range of Elix water purification equipment. The new systems integrate patented Elix electrodeionization (EDI) technology along with several other complementary water purification techniques (e.g., pretreatment, reverse osmosis, and UV lamp treatment) in order to produce Type 2 pure water with consistently pure and reliable water quality.
The new Elix Essential system range includes models with flow rates of 3, 5, 10 or 15 liters of pure water per hour, and daily production possibilities of up to 300 liters. The high-quality pure water produced by the systems has resistivity values exceeding 5 M ·cm at 25°C (typically 10-15 M ·cm at 25°C) and less than 30 ppb of TOC (Total Oxidizable Carbon).
Users of Elix Essential systems have full control over pure water quality, thanks to the systems’ high- precision monitoring equipment that measures key water quality parameters. In addition, RFID technology provides traceability for the Progard pretreatment cartridges.
“These new systems are ideal for customers who need an easy-to-use, economical solution that can provide a constant and reliable source of Type 2 pure water in the volumes they need,” says Stéphanie Bourin, Lab Water Product Manager. “Users can count on low and predictable running costs thanks to integrated Elix EDI technology, which requires no costly resin regeneration or replacement. Plus, the systems’ overall reduced water and electricity use also enables additional savings,” she adds.
Reader Reply Card No. IET March / April 2012
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Elix Essential 3, 5, 10, 15 Water Purification Systems
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