Nitrogen Purity
Nitrogen is used across many industries for different purposes. Although certain names of grades are very common, the actual grades of nitrogen are not standardized across industries or even within industries. Ultimately, the manufacturer of the nitrogen chooses the name of the grade to categorize the nitrogen. For this reason, it is possible to have two nitrogen products with the same purity specifications, but listed in grades with different names. It is also possible for two nitrogen products within the same grade to have different purity specifications. It is important to select a nitrogen product based on its purity specifications and not solely its grade.
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High-Purity Grades
High-purity grades of nitrogen are composed of greater than 99.998 percent nitrogen. The common high-purity grade names include Research Purity and Ultra High Purity. All of the high-purity grades can also be considered Zero grade. This is because they meet the specification of having less than 0.5 parts per million of total hydrocarbons required of Zero grade nitrogen. Besides hydrocarbons, nitrogen contains other impurities like oxygen, carbon dioxide, carbon monoxide and water. None of the high-purity grades contain oxygen greater than 0.5 parts per million, carbon dioxide or carbon monoxide greater than one part per million, or water greater than three parts per million.
Other Nitrogen Grades
Low-purity grades of nitrogen are composed of 90 up to 99.998 percent nitrogen. The common low-purity grade names include High Purity, Zero, Prepurified, Oxygen Free, Extra Dry and Industrial. The percentage of contaminates in these grades varies greatly. Oxygen Free grades contain less than 0.5 parts per million of oxygen. Other grades of nitrogen include the High Pressure grades. They usually come as nitrogen pressurized at or pounds per square inch with a purity of 99.998 percent.
Nitrogen Uses
The pharmaceutical industry uses high-purity grades as a shield gas for some medications. The high-purity nitrogen protects the medicine from contacting and reacting with surrounding oxygen and moisture because it is a non-reactive gas, especially if it contains low levels of impurities. Oxygen Free nitrogen is often used to coat objects or substances to make them less combustible. Combustion requires oxygen, leading to unsafe fires or explosions in some situations. Uses of low-purity nitrogen include tire inflation and industrial uses like heat treatment of furnaces.
A laboratory nitrogen generator is a machine that is able to separate nitrogen molecules from the air around it by using a compressed air source. By removing the vast majority of oxygen molecules and other impurities from an air source, these machines are able to produce high purity or ultra-high purity nitrogen gas needed to run a variety of different laboratory applications and instruments.
There are many applications that require a lab to use a nitrogen gas generator, with LC-MS, GC, ICP, ELSD, and sample preparation/blowdown evaporation being the most common. Each application will have specific nitrogen requirements (flow rate, purity level, etc.) which will determine the exact type of N2 generator needed by the lab.
N2 gas generators aren’t the only way labs are able to obtain nitrogen. Let’s get into some other common sources, and discuss when they may be a better fit.
Although nitrogen generators are a must-have for many laboratories, there are some instances where they just don’t make sense. Some labs may have a nitrogen consumption rate that is just too high for a generator to meet. On the other hand, some may require such a low amount of gas that the purchase of a generator can’t be justified.
So what are the common nitrogen gas sources for labs and who should be using each?
Ordering nitrogen gas from a third party vendor and having it delivered to your facility in tanks, cylinders, or Dewars is a great option for labs who have a very low or sporadic need for nitrogen. It’s a convenient way to get a small amount of N2 gas which may only be needed for a single project, without committing to the purchase of a new piece of equipment.
The technology behind membrane-based nitrogen generators is…you guessed it…a membrane. This type of generator contains a series of narrow, semi-permeable fibers located in a porous membrane. As compressed air is passed through, some gas molecules such as oxygen, carbon dioxide and water vapor are able to permeate the fibers quite easily and are vented off, while nitrogen molecules pass through much slower. This results in a high purity nitrogen stream (95-99% purity) from the membrane outlet.
Continue reading here for a more in-depth explanation on how membrane nitrogen generators work.
Organomation’s NITRO-GEN is a popular membrane-based N2 generator for sample preparation that is used by analytical laboratories worldwide. Producing up to 20 L/min at up to 99% purity, this lightweight generator is suitable for those using blowdown evaporation for solvent concentration. Find out how the NITRO-GEN supplies high purity nitrogen for a sample concentrator.
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PSA generators work by using two columns of tightly packed material called Carbon Molecular Sieve (CMS). Compressed air will pass through one CMS column, which will adsorb all oxygen, water vapor and other molecules, while allowing nitrogen to pass through and be stored in an accumulation tank. Once one sieve becomes saturated, compressed air will be diverted to the second CMS column, allowing the first one to depressurize, releasing all adsorbed impurities through an outlet. This process repeats over and over, leaving behind N2 gas with a 98-99.999% purity.
Continue reading here for a more in-depth explanation on how PSA technology works.
As this technology tends to produce a slightly higher purity and flow rate than with membranes, PSA generators are a great choice for both sample preparation and LC-MS applications. The NITRO-GEN+ is an affordable PSA generation solution that is able to produce up to 35 L/min, meeting all your sample prep and analytical needs. Find out how the NITRO-GEN+ can be your laboratory’s all-in-one nitrogen generation solution.
For more information on the pros and cons of each generator type, go to "which generator technology is right for me?"
Although seen as the popular and “traditional” nitrogen generation solution by many, the process of purchasing N2 tanks is quite pricey, especially for those consuming gas on a weekly or daily basis. There are many associated costs with tank-based solutions including the cost of the actual nitrogen, tank rentals, and required delivery. Let’s take a look at how much one analytical lab could be spending on tanks in just one year.
** This example uses estimated pricing. Your actual costs may vary.
A typical nitrogen tank costs around $50. It’s also common for vendors to charge a monthly rental fee, which is often around $20 each month, per individual cylinder. On top of that, you’ll be charged for delivery – for this example, let’s say the lab orders their tanks locally and it only costs them $25 per delivery.
Now, let’s estimate the nitrogen consumption for this particular lab. Let’s say they need 30 L/min of nitrogen for 4 hours a day, 5 days a week. That equals 36,000 liters of nitrogen per week, or about 5 cylinders. Over the course of a whole year, that’s nearing 2 million liters and over 250 nitrogen cylinders.
In just one year, this lab would be spending over $18,000 in nitrogen tanks alone! For most, this just isn’t feasible.
Acquiring a generator and producing your own nitrogen is a sure way to cut back on these extensive costs. Laboratory generators that are able to produce moderate flow rates and purity levels can range anywhere from $5,000 to $40,000. This one-time payment plus any required maintenance are the only things you have to take care of. No more worrying about rental costs, delivery costs, or wondering why the price of tanks has suddenly increased.
Depending on a lab’s nitrogen consumption levels, the payback period on a N2 generator could be as little as 1-3 years.
Determine how long it would take your lab to pay off a generator by using this simple nitrogen generator payback period calculator, and see how much you could be saving.
Let’s say you’re in the middle of concentrating down some analytical samples using a nitrogen dryer, and your nitrogen tank has just run out. You’re forced to stop the evaporation process, disconnect the empty tank, move it aside, bring in a new tank, recalibrate it, and hook it up to the evaporator. All the while your samples are sitting in the open air with the risk of oxidizing or otherwise becoming contaminated. With the constant gas supply a N2 generator provides, you’ll never have to worry about this happening.
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