Reliable pH measurements are essential to a variety of processes and industries. From agriculture, to wastewater and plating, to food processing, measuring pH is a crucial step in determining the efficiency of a process or quality of a product.
Vital steps in achieving accurate pH results include calibrating a pH meter and ensuring the electrode is working properly. But how do we determine when a calibration is necessary or how to troubleshoot a faulty electrode? Hanna Instruments has compiled six tips to consider when calibrating a pH meter.
1. Always read the manual
Calibration procedures change based on which meter is used. In order to best understand your specific meter and perform calibration correctly, it’s important to read the manual.
2. Ensure your calibration points bracket the pH range of your sample.
When performing a pH calibration it’s recommended to calibrate to at least two points. When choosing calibration points, it’s important to consider the pH range of the samples being measured. pH calibration is most effective when calibration points bracket the sample pH.
3. Use best practices
Ensure the glass bulb of the pH electrode is hydrated before performing a calibration. Calibrating a dry pH electrode will result in the need for frequent calibration.
Use an adequate volume of pH buffer to fully submerge the pH bulb and the reference junction, which is typically a small ceramic frit on the side of the probe.
Open or loosen the fill hole on the electrode to ensure flow or reference electrolyte into the sample. This is crucial for fast electrode response and stable electrode readings.
During pH calibration and measurement, the solution should always be stirring. Wait for the electrode reading to stabilize before accepting each calibration point.
Always use fresh buffer solution for calibration, this ensures the buffer being used is not contaminated. Check the expiration date of all buffers and keep track of how long the buffer has been opened. Buffer solutions may expire much sooner than the specified expiration dates once they are opened due to evaporation and influx of atmospheric carbon dioxide.
4. Calibrate often
For the most accurate measurements, it’s suggested to calibrate a pH meter each time a new set of measurements is performed. Calibration can also help identify a problem with electrodes.
5. Be aware of your offset and slope
Offset and slope have a significant impact on the condition of a pH meter’s electrode. The offset is the mV reading of the electrode when it’s submerged in pH 7 buffer. The theoretical offset is 0 mV; however, the offset shouldn’t exceed ±30 mV. The slope of the electrode is calculated by determining the mV change between two different pH buffers. By dividing the mV difference by the change in pH units, users can get the actual slope of the electrode. If users then divide the slope of the electrode by the theoretical slope of 59.16 mV and multiply by 100, they can get an overall percentage condition of the electrode.
If there’s an offset outside of the ±30 mV range, this could mean either a clogged junction or the probe requires cleaning. If this occurs, try soaking the probe in cleaning solution, rehydrating the bulb and repeat the process of checking offset. If the slope is too far from the ideal slope of 59.16 mV, this could mean expired or contaminated buffers have been used. If this is the case, repeat the calibration, ensuring fresh buffers are used. Following calibration, many Hanna Instruments meters will display both the slope and offset in the GLP data screen. Some Hanna meters also come equipped with CAL Check; this feature provides indicators to potential problems during the calibration process based on previous offset and slope values, allowing users to quickly solve the problem.
6. Electrode care
pH calibration and measurements are only as good as the condition of pH electrode. pH electrodes should never be stored in distilled or deionized water, as this can dehydrate the sensing glass of the pH electrode and deplete reference electrolyte. Instead, storing the electrode in storage solution will provide stable and highly responsive readings due to a properly hydrated and responsive bulb.
7. Keep a record of calibrations.
It is important that notes and records are kept of calibrations, especially recording deviations and what corrective action was taken.
By following these few simple tips, pH meter users can obtain accurate calibrations and pH measurements.
In this undated photo provided by the Gilbert family shows Dylan Gilbert, 7, of Naperville, Ill., demonstrating how he helped collect samples of bacteria from his foot during a 2012 study. Dylan’s father, microbiologist Jack Gilbert of Argonne National Laboratory, led the Home Microbiome Project that analyzed bacteria in seven homes around the country, including his own, and found the microbes that normally live in people’s bodies quickly move onto their doorknobs, countertops and floors. (AP Photo/Gilbert Family)
Sorry, clean freaks. No matter how well you scrub your home, it's covered in bacteria from your own body. And if you pack up and move, new research shows, you'll rapidly transfer your unique microbial fingerprint to the doorknobs, countertops and floors in your new house, too.
In fact, researchers who studied seven families in Illinois, Washington and California could easily match up who lived where using their microscopic roommates, almost like CSI for germs.
Thursday's study is part of an effort to understand how the trillions of mostly beneficial bacteria that live in and on our bodies—what's called the human microbiome—interact with bugs in the environment to affect our health.
"We have so little information about where the microbes come from that shape our microbiome, whether it's for health or disease," said microbiologist Jack Gilbert of the Argonne National Laboratory and Univ. of Chicago.
Where do people spend most of their time? "It's the indoor environment. The best place to look at that was the home," said Gilbert, who led the Home Microbiome Project and included his own family.
Right at birth, babies start picking up microbes on the skin, in the nose, in the gut that eventually make up living communities that will share their bodies throughout life. Many of these bugs play critical roles in digestion, the immune system and other health-inducing factors. Others may make it easier to gain weight, or influence disease. What shapes the balance of good bugs and bad is a huge scientific question.
Hospital studies make clear that someone who already is sick can catch a new infection from pathogenic bacteria left behind by a previous patient.
In contrast, the new study examines healthy people, and it marks an important step: Beginning to show what's normal in a regular home, said Dr. Lisa Helbling Chadwick of the National Institutes of Health. That's a key question before scientists can explore how to possibly create healthier homes.
"You have to think about the microbiome of your home as part of your home's immune system," said Chadwick, of NIH's National Institute of Environmental Health Sciences, who wasn't involved with Gilbert's project. "Instead of relying on killing bugs to stop the spread of infection, maybe we need to cultivate better bugs."
For the study, Gilbert recruited seven households that included 15 adults, three children, three dogs and a cat. For six weeks, participants collected samples of the microscopic bugs living on and around them by swabbing the hands, feet, noses and paws of everyone in the household, plus doorknobs, light switches, floors and countertops.
Back in the laboratory, Gilbert's team identified the bugs by their DNA, and they reported Thursday in the journal Science that people substantially affect the microbial communities in their homes.
Different homes harbored markedly different bacterial populations, but they closely matched the microbiomes of their residents.
The big surprise: How quickly the bugs settled in. Like Pigpen's trailing cloud of dust in the Peanuts comic strip, when three families moved—one of them from a hotel room to a house—it took about a day for the microbes in their new homes to closely resemble those in the old ones.
"The speed at which that colonization happens was quite remarkable," Gilbert said.
Sure, there are some leftover bacteria from previous occupants, he said. But many bacteria die or go dormant after a while on a hard, air-conditioned surface. At the same time, the oil in your skin readily transfers your own bacteria to surfaces. That's not counting all those tiny flakes of dead skin that people constantly shed, microbe-filled dust that probably just blankets the bugs that were there first, Gilbert noted.
"It changed my perspective almost on hotel rooms," he added with a laugh.
In another home, someone went on a three-day trip, and that person's contribution to the usual household microbe mix dropped noticeably.
And dogs moved the bacteria from surface to surface even more rapidly.
As for potentially dangerous bacteria, in one house, the scientists tracked a germ called Enterobacter from one person's hands to the kitchen counter and then to another person's hands. No one got sick, possibly because the residents were healthy and hadn't recently used antibiotics, Gilbert said.
It will take more research to figure out where the different bugs that people and their pets bring into their homes originally come from. And Gilbert pointed to the study's other implication: Maybe people should make sure they're regularly getting outside to expose themselves, and their immune systems, to a wider variety of bugs.
Does your sweetheart have a milk allergy? You may want to hold off on a dark chocolate Valentine. Although dark chocolate generally isn't made with milk, a new Food and Drug Administration study released this week shows that there are traces of milk in some of the candies.
The agency found that 55 of 93 bars of dark chocolate "without any clear indication of the presence of milk" on their labels contained some level of milk. The agency also found that two out of 17 dark chocolate bars that were labeled "dairy free or allergen-free" contained milk.
"This can be a problem, since even one small bite of a product containing milk can cause a dangerous reaction in some individuals," says FDA researcher Binaifer Bedford.
The agency would not say what brands of bars tested positive for milk.
Milk is one of several allergens required to be labeled on food packages. The agency tested dark chocolate after hearing from consumers who said they had eaten it and experienced harmful reactions.
The FDA said milk can inadvertently end up in dark chocolate if it is manufactured on the same equipment that makes milk chocolate.
The bars tested were purchased from different parts of the country and from several different manufacturers.
When it comes to allergens, labels can be confusing. Some foods are labeled that they "may contain traces of milk," but a consumer doesn't know how much milk that is, or whether it's enough to cause a reaction. The FDA said the dark chocolate study showed that 6 out of 11 tested products that were labeled as containing traces of milk "contained milk at detectable levels high enough to potentially cause severe reactions in some individuals."
The FDA says concerned consumers should contact food manufacturers to find out how they control for allergens. If they experienced an allergic reaction, they can call FDA or report it online.
The harmful and potentially deadly bacterium Listeria is extremely good at adapting to changes. Now research from University of Southern Denmark uncovers exactly how cunning Listeria is and why it is so hard to fight. The discovery can help develop more efficient ways to combat the bacteria.
Listeria is a dreaded bacterium that can be found in both unprocessed and processed foods. Over the last few weeks, 28 persons in Denmark have been infected with Listeria from processed food, sold in supermarkets. 13 have died.
The bacterium is notoriously difficult to fight because it has an almost uncanny ability to adapt to changes in its surroundings, says Associate Professor Birgitte Kallipolitis, University of Southern Denmark. Together with colleagues from the Department of Biochemistry and Molecular Biology, she has published a study, which in details reveals how this extreme ability to adapt takes place.
The researchers tested how Listeria reacts when it is exposed to a number of substances that can normally fight pathogenic bacteria. In the laboratory, Listeria was exposed to antibiotics, bile, salt, acid and ethanol, similar to what it often encounters in food, in the human body and during disinfection.
Listeria is constantly alert
"We knew that Listeria can resist these substances, but we did not quite know how," says Kallipolitis.
The researchers discovered that Listeria used a variety of strategies that enabled them to withstand the substances.
"Generally speaking, Listeria must be described as extremely adaptable. It is constantly aware of its surroundings and if the environment changes around it. It reacts instantly and has a number of strategies to withstand threats," says Kallipolitis.
The researchers also discovered that listeria is an expert at not attracting unwanted attention from the body's immune system.
"On the one hand, Listeria needs to produce some special proteins that enable it to infect the cells in our body. On the other hand, it must ensure that the body's immune system does not detect these proteins. It is vital for Listeria to keep a balance between producing enough of these proteins but not so many that they are detected by the immune system—and it masters just that,” explains Kallipolitis.
When in the lab, the researchers looked at what happened at the microbiological level. It turned out that Listeria started producing some special RNA molecules, when they were exposed to antibiotics, bile, salt, acid and ethanol.
It is all about controlling protein production
"With these RNA molecules the bacteria can adjust how much or how little to produce of various proteins. For example it can downgrade the production of the protein LapB, which it uses to enter our cells. If this production is not downgraded, the bacterium will potentially be detected and fought by the immune system,” says Kallipolitis.
In other words: Listeria can fine-tune the production of the proteins needed to infect our cells to a point where there is exactly enough to sneak through the immune system’s defense, but not so many that they are discovered.
The RNA molecules, produced when Listeria face dangerous environmental changes, also helps Listeria monitor its own cell wall. Antibiotics work by attacking the bacterial cell wall, and when exposed to antibiotics Listeria immediately detects that its cell wall is attacked. This enables it to quickly repair its cell wall—and thus become ready for combat again.
"We see this production of RNA molecules only when Listeria is exposed to threatening substances in the lab. When there are no threats, Listeria does not produce them. This reveals part of the mechanism behind Listeria´s extreme adaptability," concludes Kallipolitis.
The understanding of how Listeria is able to survive antibiotics, the immune system and disinfecting agents is necessary in order to develop effective means against the life-threatening bacteria.
"Only by looking at what the bacteria themselves do to survive, we can become better at fighting their pathogenicity," says Kallipolitis.
She and her colleagues are now investigating whether Listeria can be changed into harmless bacteria by removing the RNA molecules.
A multicopy sRNA of Listeria monocytogenes regulates expression of the virulence adhesin LapB - http://nar.oxfordjournals.org/content/42/14/9383
Source: Southern Denmark Univ. - www.sdu.dk/en/Om_SDU/Fakulteterne/Naturvidenskab/Nyheder/2014_27_08_listeria
Research finds hand dryers are much worse than paper towels when it comes to spreading germs, according to new University of Leeds research.
Scientists from the University of Leeds have found that high-powered 'jet-air' and warm air hand dryers can spread bacteria in public toilets. Airborne germ counts were 27 times higher around jet air dryers in comparison with the air around paper towel dispensers.
The study shows that both jet and warm air hand dryers spread bacteria into the air and onto users and those nearby.
The research team, led by Professor Mark Wilcox of the School of Medicine (http://medhealth.leeds.ac.uk/info/200/school_of_medicine/), contaminated hands with a harmless type of bacteria called Lactobacillus, which is not normally found in public bathrooms. This was done to mimic hands that have been poorly washed.
Subsequent detection of the Lactobacillus in the air proved that it must have come from the hands during drying. The experts collected air samples around the hand dryers and also at distances of one and two metres away.
Air bacterial counts close to jet air dryers were found to be 4.5 times higher than around warm air dryers and 27 times higher compared with the air when using paper towels. Next to the dryers, bacteria persisted in the air well beyond the 15 second hand-drying time, with approximately half (48%) of the Lactobacilli collected more than five minutes after drying ended. Lactobacilli were still detected in the air 15 minutes after hand drying.
Professor Wilcox said: "Next time you dry your hands in a public toilet using an electric hand dryer, you may be spreading bacteria without knowing it. You may also be splattered with bugs from other people's hands.
"These findings are more important for understanding the ways in which bacteria spread, with potential to transmit illness and disease."
The research, funded by the European Tissue Symposium, was published in the Journal of Hospital Infection (http://www,sciencedirect.com/science/article/pii/S0195670114002461) and presented at the Healthcare Infection Society (http://www.his.org.uk/events/his2014/#.VG3fNY1FDcs) (HIS) International Conference in Lyon France.
For more information:
This ACS video breaks down the chemistry of our favourite frozen treat.
By American Chemical Society | June 17, 2014
The summer weather is here, and if you've been out in the sun, you're probably craving some ice cream to cool off. In the American Chemical Society's latest Reactions video, American University Assistant Professor Matt Hartings, Ph.D., breaks down the chemistry of this favorite frozen treat, including what makes ice cream creamy or crunchy, and why it is so sweet.
Romer Labs announced that both test kit lines, the AgraQuant Gluten G12 ELISA test and the AgraStrip Gluten G12 lateral flow test have obtained important approvals
| October 7, 2014
Romer Labs announced that both test kit lines, the AgraQuant Gluten G12 ELISA test and the AgraStrip Gluten G12 lateral flow test have obtained important approvals:
• The AgraStrip Gluten G12 lateral flow test obtains AOAC-RI approval
• The AgraQuant Gluten G12 ELISA test is now an AOAC Official Method and approved by the American Association of Cereal Chemists (AACCI)
• The AgraQuant Gluten G12 ELISA has proven in an validation from an influential third party that the delivers accurate and reliable results helping food producers to comply to standards and requirements set by the FDA and the Codex Alimentarius.
All requirements to comply with the FDA gluten free labeling rule demanding that only food that contains less than 20 parts per million (ppm) Gluten can be labeled as gluten free, are met.
Furthermore, the AgraQuant® Gluten G12 Elisa test fullfills the Codex Standard 118-1979 requirements for an effective and precise analytical method needed to determine the gluten concentration in foods and raw materials.
The Science of Caffeine: The World's Most Popular Drug - Reactions
Global Handwashing Day was originally created for children and schools, but can be celebrated by anyone promoting hand washing with soap.
Each year on October 15, over 200 million people are involved in celebrations in over 100 countries around the world.
Glitterbug® is a great tool to help teach the correct way to wash your hands. We all think we do it right but Glitterbug® can show you immediately those bits you may have missed – unless you wash ALL of your hand you could be contaminating anything you touch and so spreading disease.
You can use Glitterbug® Potion for teaching handwashing with soap or the Gel to teach how to spread waterless hand sanitisers over the whole hand.
Why Handwashing with Soap?
Handwashing with soap is the most effective and inexpensive way to prevent diarrheal and acute respiratory infections, which take the lives of millions of children in developing countries every year. Together, they are responsible for the majority of all child deaths. Yet, despite its lifesaving potential, handwashing with soap is seldom practiced and difficult to promote.
Turning handwashing with soap before eating and after using the toilet into an ingrained habit could save more lives than any single vaccine or medical intervention, cutting deaths from diarrhea by almost half and deaths from acute respiratory infections by one-quarter.
A vast change in handwashing behaviour is critical to meeting the Millennium Development Goal of reducing deaths among children under the age of five by two-thirds by 2015.
Global Handwashing Day focuses on children because not only do they suffer disproportionately from diarrheal and respiratory diseases and deaths, but research shows that children – the segment of society so often the most energetic, enthusiastic, and open to new ideas – can also be powerful agents for changing behaviours like handwashing with soap in their communities. - See more at: http://globalhandwashing.org/
Video of What Causes Garlic Breath? - Reactions
Garlic is good for your body, great for your taste buds, but terrible for your breath. In the American Chemical Society’s latest Reactions video, chemists look at the plant beloved by chefs and feared by vampires. Once again they’ve teamed up with the Compound Interest blog to break down the chemistry of garlic, and how to beat the bad breath it causes.