A substance's pH is a measure of its acidity or alkalinity as expressed in the concentration of hydrogen ions it contains. The pH (short for "power of hydrogen") scale is created by multiplying the exponent for the concentration of hydrogen ions in solution (0.1 equal to 10 to the power of -1, 0.01 equal to 10 to the power of -2) by -1. The pH scale runs from 1 to 14; vinegar (acetic acid), has a pH of 2, while a strong alkali like caustic lye (sodium hydroxide) has a pH of 12, and pure water, considered neutral, has a pH of 7. Such things as blood, soil, battery acid, and swimming pools are pH tested, but pH testing is especially important in ensuring the safety and quality of foods ranging from coffee and cheese to beer and wine. Although litmus paper can be used to test acidity in foods with a pH of 4.0 or less, the best way to ensure correct pH is by using an electronic pH meter, which uses a thin, glass-tipped probe to measure voltage changes caused by the hydrogen ions in solution. Here's what to look for when shopping for a pH meter.
1
Look for a sufficient level of accuracy. Meters used to measure pH in scientific research are accurate to within 0.002 pH units. If you're buying a pH meter to test the acidity of food, you'll most likely want a unit with an accuracy of 0.01 to 0.02 units, although you can get by with a pH meter with an accuracy of 0.2 units if the pH of the food item you're making won't exceed 4.0.
For certain foods where the sugar-to-acid ratio is important, such as jellies, jams, and preserves, you'll want a more accurate meter, regardless of the pH of the food, as the pH will affect the temperature at which the food jells and how well it sets. For other flavor-sensitive foods, using a less accurate pH meter could cause you to add acid when you don't need to and so alter the food's flavor.
Using a less accurate pH meter with foods whose pH can exceed 4.0 runs the risk of allowing foods with an unsafely high pH (4.6 or higher) to go on the market.
Your pH meter should not only be accurate, but its results should also be consistent from reading to reading. If it gives widely different results a minute apart, it's not reliable.
2
Look for a pH meter with at least 2-point calibration. To ensure accuracy, the pH meter must be calibrated to ensure its readings are accurate. Calibration is done with standard solutions of known pH. There are 3 standard solutions: pH 4, pH 7, and pH 10. If you are buying a pH meter to test acidic foods, you need to have 2 points of calibration, pH 4 and pH 7. If you are buying a pH meter for scientific research, then you'll also need the pH 10 calibration standard solution.
Calibration solutions are color-coded for easy identification. The pH 4 solution is usually red, the pH 7 solution is usually yellow, and the pH 10 solution is usually blue.
You should calibrate your pH meter at the same temperature as the item you're testing to ensure accuracy.
3
Choose a unit with the appropriate style of electrode for your testing needs. If you're pH-testing foods with little or no oil, or foods where oil can be added later or separated out, you can get by with standard glass-tipped electrodes. For foods with a high-oil content where the oil cannot be separated out, such as salad dressings, you will need electrodes that won't be clogged by the solution they're immersed in.
Some pH meters come with several types of electrodes, while other meters require you to buy the electrode you need separately.
If you are going to use the pH meter in a number of places, choose a meter where the electrode isn't permanently attached. If the electrode breaks, your meter will be useless.
4
Look for a durable unit. Your pH meter should be rugged enough to stand up to the environment or environments you'll be using it in. A unit designed to be taken into the field should be resistant to dirt and possibly also to harsh chemicals. If you test for acidity on just-cooked foods, your pH meter should be able to withstand a temperature of at least 160 degrees Fahrenheit (71 degrees Celsius).
5
Look for automatic temperature compensation. Because pH readings are affected by temperature, buying a pH meter with automatic temperature compensation is helpful if you produce a large amount of food items that need to be tested and don't have the time to let the food cool to room temperature before testing. The temperature compensation feature should have a range that covers the temperature at which your sample is to be tested.
If you use a pH meter without temperature compensation, you can either test samples only at room temperature or use a temperature compensation chart to determine the correct pH.
6
Consider a pH meter that connects to a computer. This kind of meter automatically transfers a sample's pH and temperature readings to the computer, useful if you routinely test a large number of samples at a given time. This feature adds about $75 to $100 to the overall cost of the pH meter, however, so if you test only a small number of samples at a time, you may not be able to justify the additional cost.
7
Shop for the best price. You can buy a pH meter from a scientific supply company or directly from the manufacturer' website. Prices range from under $100 to over $1,000; to get the best deal, assess your needs and ask the company's representatives about the capabilities and features of their pH meters before you buy.
YK Scientific Instrument is a professional manufacturer and supplier of kinds of PH Meters with or without Temperature Compensation.
Any enquiries, please email us: sales@yk-instrument.com
2016年9月14日星期三
9 Different Types of Spectroscopy Techniques & their Uses
Spectroscopy is that branch of physics which deals with interaction light with materials. In other words it is an analytical method for qualitative and quantitative estimation by use of light.
Light is as we all know is an electromagnetic radiation which has wave and frequency as measurable characters.
You can know more details here on the principle of spectroscopy.
Spectroscopy finds wide spre 0ad application in daily life. It is used in analytical chemistry, phyto-chemistry (plant chemistry), biological analysis, health care and medicine.
Further is became a part of other means of estimation and analysis like in chromatography, elemental analysis and also identification tools.
This is mainly of 3 types which is again classified into subtypes.
THE DIFFERENT TYPES OF SPECTROSCOPY INCLUDE:
a. Based on the level of study. Here the classification is done based on the study made at atomic or molecular level. When light is allowed to pass through the substance, changes in atomic level or molecular level is observed.
1) Atomic spectroscopy: Here energy changes takes place at atomic levels. The measurement is done to study the atoms and their quantity. This is of two types as atomic absorption spectroscopy and atomic emission spectroscopy. These are referred as atomic absorption spectroscopy and flame photometry respectively.
Here the sample mostly metals and their formulations are converted to atomic forms and then measured. Ex: Sodium, calcium, magnesium related formulations.
This finds less application as the characters of most substance are depended on the molecular nature and not just atoms in it.
Also the methods are expensive, time taking and even quite tedious to perform.
2) Molecular spectroscopy: Here the energy changes occurring at the level of molecule are studied. The characters like molecular absorption. emission and vibration are studied.
The examples include, colorimetry, UV-spectroscopy, infra red, FTIR, fluorimetry etc.
This method of spectroscopy is widely used due to many applications. The methods are quick, easy and accurate in determination. Further they are easily integrated into other analytical techniques like chromatography.
B) Based on the property of either absorption or emission.
Here the principle of abortion or emission of electromagnetic radiation is taken into consideration.
1) Absorption spectroscopy: As the name suggests, here there is absorption of light by the sample. The extent of absorption and the wavelength of the absorbed light is considered. The wavelength of light absorbed tells the nature of the compound while the intensity of absorbed light tells the concentration.
The examples of the spectroscopic methods coming under this method are colorimetry, UV-spectroscopy, infra red spectroscopy, Nuclear magnetic resonance (NMR), atomic absorption spectroscopy.
2) Emission spectroscopy: Contrary to the above method, here the emitted light is measured. once the light impinges on the sample, some of it is absorbed. This absorption of light leads to transition of electrons from ground state to excited state. These excited electrons return back to ground state by release of electromagnetic radiation (light) of specific wavelength. The intensity gives the concentration while the wavelength tells the nature of the compound.
Examples include fluorimetry, flame photometry.
C) Based on the level of study i.e. electronic or magnetic levels.
Here the study is done based on electronic or magnetic properties of the compound. Light is an electromagnetic radiation. That is it has both electronic and magnetic properties.
Electronic spectroscopy: So when a compound is estimated without the magnetic field we call it electronic spectroscopy. In this method the substance under test is exposed to light without the influence of magnetic field.
Examples of this method are again colorimetry, UV-spectroscopy, IR, fluorimetry etc.
Magnetic spectroscopy: Here the substance is exposed to electromagnetic radiation in presence of external magnetic field.
Examples include Nuclear magnetic resonance spectroscopy (NMR), Electron spin resonance spectroscopy (ESR).
Any enquiries, please email us: sales@yk-instrument.com
Light is as we all know is an electromagnetic radiation which has wave and frequency as measurable characters.
You can know more details here on the principle of spectroscopy.
Spectroscopy finds wide spre 0ad application in daily life. It is used in analytical chemistry, phyto-chemistry (plant chemistry), biological analysis, health care and medicine.
Further is became a part of other means of estimation and analysis like in chromatography, elemental analysis and also identification tools.
This is mainly of 3 types which is again classified into subtypes.
THE DIFFERENT TYPES OF SPECTROSCOPY INCLUDE:
a. Based on the level of study. Here the classification is done based on the study made at atomic or molecular level. When light is allowed to pass through the substance, changes in atomic level or molecular level is observed.
1) Atomic spectroscopy: Here energy changes takes place at atomic levels. The measurement is done to study the atoms and their quantity. This is of two types as atomic absorption spectroscopy and atomic emission spectroscopy. These are referred as atomic absorption spectroscopy and flame photometry respectively.
Here the sample mostly metals and their formulations are converted to atomic forms and then measured. Ex: Sodium, calcium, magnesium related formulations.
This finds less application as the characters of most substance are depended on the molecular nature and not just atoms in it.
Also the methods are expensive, time taking and even quite tedious to perform.
2) Molecular spectroscopy: Here the energy changes occurring at the level of molecule are studied. The characters like molecular absorption. emission and vibration are studied.
The examples include, colorimetry, UV-spectroscopy, infra red, FTIR, fluorimetry etc.
This method of spectroscopy is widely used due to many applications. The methods are quick, easy and accurate in determination. Further they are easily integrated into other analytical techniques like chromatography.
B) Based on the property of either absorption or emission.
Here the principle of abortion or emission of electromagnetic radiation is taken into consideration.
1) Absorption spectroscopy: As the name suggests, here there is absorption of light by the sample. The extent of absorption and the wavelength of the absorbed light is considered. The wavelength of light absorbed tells the nature of the compound while the intensity of absorbed light tells the concentration.
The examples of the spectroscopic methods coming under this method are colorimetry, UV-spectroscopy, infra red spectroscopy, Nuclear magnetic resonance (NMR), atomic absorption spectroscopy.
2) Emission spectroscopy: Contrary to the above method, here the emitted light is measured. once the light impinges on the sample, some of it is absorbed. This absorption of light leads to transition of electrons from ground state to excited state. These excited electrons return back to ground state by release of electromagnetic radiation (light) of specific wavelength. The intensity gives the concentration while the wavelength tells the nature of the compound.
Examples include fluorimetry, flame photometry.
C) Based on the level of study i.e. electronic or magnetic levels.
Here the study is done based on electronic or magnetic properties of the compound. Light is an electromagnetic radiation. That is it has both electronic and magnetic properties.
Electronic spectroscopy: So when a compound is estimated without the magnetic field we call it electronic spectroscopy. In this method the substance under test is exposed to light without the influence of magnetic field.
Examples of this method are again colorimetry, UV-spectroscopy, IR, fluorimetry etc.
Magnetic spectroscopy: Here the substance is exposed to electromagnetic radiation in presence of external magnetic field.
Examples include Nuclear magnetic resonance spectroscopy (NMR), Electron spin resonance spectroscopy (ESR).
Any enquiries, please email us: sales@yk-instrument.com
2016年9月13日星期二
New UV-Vis spectrophotometer simplifies sample quality decisions
Life scientists who work with DNA, RNA and proteins can make educated decisions about sample suitability in experiments using a standalone, microvolume spectrophotometer for accurate quantitation and purity measurements to ensure downstream application success.
The Thermo Scientific NanoDrop One and NanoDrop OneC UV-Vis microvolume spectrophotometers are designed to help life science researchers gain a more complete understanding of sample quality and avoid costly delays due to troubleshooting and repeating experiments. These new spectrophotometers introduce the Thermo Scientific Acclaro Sample Intelligence technology, which enables researchers to:
Identify sample contaminants and obtain corrected concentration results;
Receive instant feedback about sample quality with on-demand technical support and guided troubleshooting; and
Confidently measure samples with embedded sensor and digital image analysis.
“Building on the success of previous NanoDrop instruments, used by thousands of scientists worldwide, we have designed the NanoDrop One instrument to provide simplicity and speed as well as information on sample quality. This allows scientists to accurately quantify and qualify nucleic acid and protein samples, so they can make informed decisions on sample use in downstream applications,” said Dr. Voula Kodoyianni, product manager, molecular spectroscopy, Thermo Fisher Scientific.
The NanoDrop One instrument with its high-resolution, touchscreen interface makes it simple to use as a compact, ergonomic instrument, while the powerful auto-range pathlength technology facilitates accurate measurements for concentrated samples with no need for dilutions.
The patented NanoDrop sample-retention system measures 1-2 µL of sample in seconds without the need for cuvettes, making it a cost- and time-effective solution for busy labs. Workflows can be streamlined on the NanoDrop One instrument with the Auto-Measure functionality, while modern connectivity allows results to be shared and archived via Wi-Fi, Ethernet or USB. The NanoDrop OneC instrument contains both pedestal and cuvette measuring positions, increasing dynamic range and assay flexibility.
YK Scientific Instrument is a professional supplier of UV-Vis spectrophotometer.
Any enquiries, please email us: sales@yk-instrument.com
The Thermo Scientific NanoDrop One and NanoDrop OneC UV-Vis microvolume spectrophotometers are designed to help life science researchers gain a more complete understanding of sample quality and avoid costly delays due to troubleshooting and repeating experiments. These new spectrophotometers introduce the Thermo Scientific Acclaro Sample Intelligence technology, which enables researchers to:
Identify sample contaminants and obtain corrected concentration results;
Receive instant feedback about sample quality with on-demand technical support and guided troubleshooting; and
Confidently measure samples with embedded sensor and digital image analysis.
“Building on the success of previous NanoDrop instruments, used by thousands of scientists worldwide, we have designed the NanoDrop One instrument to provide simplicity and speed as well as information on sample quality. This allows scientists to accurately quantify and qualify nucleic acid and protein samples, so they can make informed decisions on sample use in downstream applications,” said Dr. Voula Kodoyianni, product manager, molecular spectroscopy, Thermo Fisher Scientific.
The NanoDrop One instrument with its high-resolution, touchscreen interface makes it simple to use as a compact, ergonomic instrument, while the powerful auto-range pathlength technology facilitates accurate measurements for concentrated samples with no need for dilutions.
The patented NanoDrop sample-retention system measures 1-2 µL of sample in seconds without the need for cuvettes, making it a cost- and time-effective solution for busy labs. Workflows can be streamlined on the NanoDrop One instrument with the Auto-Measure functionality, while modern connectivity allows results to be shared and archived via Wi-Fi, Ethernet or USB. The NanoDrop OneC instrument contains both pedestal and cuvette measuring positions, increasing dynamic range and assay flexibility.
YK Scientific Instrument is a professional supplier of UV-Vis spectrophotometer.
Any enquiries, please email us: sales@yk-instrument.com
How to select a laboratory balance?
1. Weight Capacity of the Analytical Weighing Balance
You’ll need to select a balance that displays sample weight to the resolution desired. This is described as readout. Readout can be to several decimal places presented in grams or milligrams.
Select a balance with a weighing capacity in excess of the samples you plan to weigh. Some balances also specify the minimum load that can be placed on the weighing plate.
2. Analaytical Balance Weighing Errors
Balance errors are expressed several ways including: linearity and repeatability. Linearity describes the maximum difference between the true weight of the sample over its weighing range and the deviation of readout from that weight. If you draw a plot of the real sample weight vs. the weight displayed, for a perfect balance this plot would be a straight line. But nothing is perfect. Laboratory balance specification tables present linearity as a plus/minus (±) figure which represents the maximum ± deviation of the curve from the straight line. For ABT balances with a 10 mg minimum sample size linearity is ±0.2 mg or ±0.3 mg depending on balance capacity; for the ABT balance with a 1 mg minimum load and 101 g capacity linearity is ±0.15 mg.
Repeatability (designated by some manufacturers as reproducibility) is the ability of a balance to display the same result when an object is repeatedly weighed under the same conditions. Repeatability is usually the standard deviation of 10 consecutive measurements of a calibrated test weight. In the 10 mg minimum load balances discussed here repeatability is 0.1 mg, and for the 1 mg minimum load balance it is 0.05 mg.
Analytical balance accuracy is highly dependent on where the instrument is placed and how it is maintained. We direct your attention to our post on setting up and maintaining your balance to avoid weighing errors and to insure long term reliable performance. Again we invite you to contact our experts for advice and suggestions on choosing the correct balance for your weighing requirements.
YK Scientific Instrument is a professional manufacturer and exporter of Laboratory Balances.
Should you have any enquiry, please contact us: sales@yk-instrument.com
You’ll need to select a balance that displays sample weight to the resolution desired. This is described as readout. Readout can be to several decimal places presented in grams or milligrams.
Select a balance with a weighing capacity in excess of the samples you plan to weigh. Some balances also specify the minimum load that can be placed on the weighing plate.
2. Analaytical Balance Weighing Errors
Balance errors are expressed several ways including: linearity and repeatability. Linearity describes the maximum difference between the true weight of the sample over its weighing range and the deviation of readout from that weight. If you draw a plot of the real sample weight vs. the weight displayed, for a perfect balance this plot would be a straight line. But nothing is perfect. Laboratory balance specification tables present linearity as a plus/minus (±) figure which represents the maximum ± deviation of the curve from the straight line. For ABT balances with a 10 mg minimum sample size linearity is ±0.2 mg or ±0.3 mg depending on balance capacity; for the ABT balance with a 1 mg minimum load and 101 g capacity linearity is ±0.15 mg.
Repeatability (designated by some manufacturers as reproducibility) is the ability of a balance to display the same result when an object is repeatedly weighed under the same conditions. Repeatability is usually the standard deviation of 10 consecutive measurements of a calibrated test weight. In the 10 mg minimum load balances discussed here repeatability is 0.1 mg, and for the 1 mg minimum load balance it is 0.05 mg.
Analytical balance accuracy is highly dependent on where the instrument is placed and how it is maintained. We direct your attention to our post on setting up and maintaining your balance to avoid weighing errors and to insure long term reliable performance. Again we invite you to contact our experts for advice and suggestions on choosing the correct balance for your weighing requirements.
YK Scientific Instrument is a professional manufacturer and exporter of Laboratory Balances.
Should you have any enquiry, please contact us: sales@yk-instrument.com
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