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Sintered woven wire laminate offers a balance of customization, efficiency, and cost-effectiveness, making it perfect when constructing a chromatography frit. This guide provides insight that will equip you to select and optimize your next woven wire chromatography frits, ensuring accurate and repeatable results.
You will learn about critical design parameters, creating a frit that delivers desirable results, selecting the correct specifications, and more. Whether you are just getting started or a seasoned professional, The Ultimate Guide To Chromatography will help project your chromatography process to greater heights.
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Chromatography is best defined as the scientific process in which a mixture is separated into the individual elements that make it up. It relies on a carrying agent (liquid or gas) to project the mixture through a filter medium.
As the elements of the mixture have different characteristics, flow speed variation is critical to individualizing the elements. It balances the interaction time of the mixture as it passes the filter, creating a sharper, more distinct element separation.
Now, there are several different ways to conduct chromatography, including paper chromatography, liquid chromatography, gas chromatography, thin-layer chromatography, high-performance chromatography, size-exclusive chromatography, and ion exchange chromatography. That said, woven wire is most beneficial to high-performance liquid chromatography.
High-performance liquid chromatography entails submerging the mixtures in a special solvent. This solvent, called the mobile phase, carries the mixture through the chromatography column.
Pressure is created within the column, pressing the mixture against the filter (stationary phase). As stated above, the pressure generated varies to control flow rate speeds to ensure accurate separation.
As the mixture separates, elements with higher affinity take longer to pass, and lower affinity elements pass quicker. This is how clear, easy-to-read separations are achieved.
Once the mixture has passed in its entirety and the elements have been successfully eluted, you can then identify and quantify each element.
Woven wire mesh is a versatile screening material fabricated using a centuries-old weaving process to interlock thousands of metal wires. With alloy capabilities spanning from stainless steel to brass to hastelloy, roadblocks associated with strength, element resistance, conductivity, etc., are easily tackled.
It can be fully customized to accommodate your chromatography requirements. You have complete control over all parameters, including weave pattern, alloy, wire diameter, micron rating, and layer configuration.
And because of this customization, woven wire comes in many forms. In recent years, sintered multi-layered wove wire laminates, like W.S. Tyler's POROSTAR®, have become more widely used.
Check out how woven wire is made:
POROSTAR® is a woven wire laminate that consists of multiple layers of varying woven wire specifications. These layers are firmly bonded together without compromising the geometric structure of the individual layers.
This ensures a woven wire solution that provides advanced durability, pore size accuracy, pore distribution, porosity, and permeability.
While highly durable, POROSTAR can be shaped, formed, and welded to ensure a glove fit in nearly every chromatography application. To that end, POROSTAR can be attached to additional support elements, making it even more versatile.
POROSTAR is available in four standardized specifications: POROSTAR standard, POROSTAR light, POROSTAR hiflo, and POROSTAR Combi. While each spec is designed for distinct applications and performance, they are typically produced to 1,500mm x 1200mm or 1,200mm x 1,200mm sheets before being fabricated into filter discs or other filtration components.
POROSTAR spec that is put in filter sheets and cylinders. It is designed with five or six layers and is especially suitable for unbalanced loads.
POROSTAR spec suitable for manufacturing pleated filter cylinders and discs with very small diameters, e.g., 2.5 mm, and is comprised of three woven wire cloth layers.
Because of its essential flow capacity, Porostar® HIFLO is especially suitable for sieving and filtering methods using minimized pressures. Each woven wire cloth layer is a square mesh weave.
POROTAR spec that is suitable for high-pressure applications, even in reverse direction flow. Woven wire cloth layers and a perforated metal plate are bonded by sintering. Porostar®-Combi is also available in Standard-type and special types of light or HIFLO.
The number of woven wire layers and thickness of the perforated metal plate are variable.
As mentioned above, POROSTAR chromatography frits are particularly beneficial to high-performance liquid chromatography. The precision of the multiple mesh layers helps deliver pinpoint separation without affecting the flow rate variation speeds.
In fact, its calculated pore sizes and pore opening distribution aid in controlling the flow rate in which the mixtures pass through the stationary phase. And with its heightened durability, it won't flex or sag when enduring high-pressure loads.
This, alongside its ability to block unwanted contaminants, affords a boosted elution, which translates to accurate and repeatable results. Additionally, POROSTAR is constructed from alloys that are highly resistant to corrosion, meaning its dependability won't decline when subjected to the harshest environments.
As stated previously, POROSTAR is a wire mesh laminate that consists of several layers of woven wire mesh. These mesh layers undergo a specialized diffusion process that squeezes the mesh layers together under tremendous heat and pressure.
After diffusion, a secondary sintering process is applied to ensure an even and secure bond. This leaves you with a porous screen media panel with predetermined characteristics.
These panels are then cut, formed, and otherwise fabricated to fit your chromatography machine. When applicable, fabricated POROSTAR plates are then attached to the support materials you specify.
During the chromatography process, woven wire chromatography frits can be subjected to varying temperatures, chemicals, and pressure loads. Being able to withstand operational variants without flexing, sagging, or distorting is critical to achieving peak separation results.
For this reason, you must take the time to identify and implement a woven wire alloy suitable to deliver the desired results. The three primary alloys you will want to compare and consider are Hastelloy, 316 stainless steel, and 904L stainless steel.
Hastelloy is a nickel-based woven wire alloy known for its performance in severe conditions, particularly when exposed to extreme heat. It is comprised of less than 01% carbon, less than .08% silicon, less than .5% manganese, 20-22.5% chromium, and 12.5-14.5% molybdenum.
With a heat conductivity capacity of .9 W/Km, Hasteloy can withstand operational temperatures reaching 1022F (550C).
316 stainless is possibly the most widely used alloy for woven wire applications as it provides peak versatility. It is comprised of 16% chromium, 8% nickel, 2% molybdenum, and 1% carbon.
The minimal carbon content makes 316 stainless steel a low-carbon alloy. This means that woven wire made from the alloy is resistant to carbide precipitation.
904L stainless steel is an austenitic woven wire alloy used primarily for its ability to perform in harsh conditions that would hamper the performance of more standard stainless steel. It is comprised of 45-47% iron, 19-23% chromium, 23-28% nickel, 4-5% molybdenum, 2% manganese, 1% silicon, .045% phosphorus, .035% sulfur, and .020% carbon.
Dozens of alloys can be used to weave woven wire and fabricate woven wire chromatography frits. But as stated above, Hastelloy, 316 stainless steel, and 904L stainless steel are the most widely used.
"What alloy should I be using?"
Well, this depends on the needs of your chromatography process. First and foremost, you must consider a specific alloy if it offers characteristics that your process relies on. For example, if your chromatography frit must deliver optimal corrosion resistance, you must select an alloy with high nickel content.
It should be noted that in certain cases, "less is more" when talking about alloy cost. For a cost exercise, we will look at both the nickel and iron content of the three prominent alloys:
The average cost of iron is approximately $0.04/lb, with the approximate average cost of nickel around $7.30/lb. This illustrates that there is a notable price gap between these alloys.
So, if you can achieve the results you need with 316 stainless steel, you can achieve the same results with Hastelloy. But is it worth the investment since Hastelloy costs significantly more?
This is why it's critical that you are as transparent as possible with your woven wire supplier when it comes to the needs of your process. This will ensure you select the suitable woven wire alloy.
The opening size of each mesh layer used to construct your woven wire chromatography frit dictates parameters such as mesh count, wire diameter, and number of layers. Subsequently, mesh count directly controls the separation efficiency of your chromatography frit.
Mesh count is defined as the number of pore openings in a linear inch. So, if you get your hands on a 20x20 piece of mesh, you will find 20 openings in an inch in any direction.
Wire diameter is a measurement of how thick the individual wires of the weave are. So, looking at the same 20x20 piece of mesh, a specification with .020 diameter wires will have larger openings than a specification with .022 diameter wires.
This is because, with the number of openings remaining the same, the smaller wires increase the percentage of open area.
Now, it's essential to know that there are two primary weave types: plain weave and filter weave. Plain weaves are known for having the same number of openings in any given direction, but filter weaves can be a little more complex.
You will often see filter weaves with mesh count descriptors that look like 170x850. This means that you will find the spec to have 170 openings in one direction and 850 in the other.
This variation in openings also means that the wire diameters in the weave will vary.
Selecting The Right Layer ConfigurationWhen experimenting with layer configuration, you must identify a configuration that balances separation capacity and flow rate. You will want to consider things like the properties of the mixture(s) being run, the size of the packing material (if applicable), as well as the thickness and density of the frit.
Integrating multi-layered specifications can improve flow distribution and optimize separation efficiency. While you can customize your layer configuration to accommodate your operation best, it is critical that you include a coarse layer, an intermediate layer, and a fine layer.
A coarse layer is put in place to improve the flow distribution of the mixture as it passes the inlet side of the frit. When implemented correctly, this layer works to dampen channeling impact.
This prevents inconsistent separation as the mobile phase passes.
Intermediate layers are used to reduce the pore size of the frit gradually, serving as the middle ground between the fine layer pore size and the coarse layer pore size. They work to create a more smooth mixture flow.
Additionally, these layers provide the fine layer with extra mechanical support. For this reason, it is common for several intermediate layers to be used.
The fine layer blocks unwanted material from passing through the frit. This means that the pore sizes must be smaller than the smallest unwanted particle present when running a mixture.
At the same time, the pore openings interact with the different element affinities in a way that promotes accurate separation.
Now, when determining what layer configuration to use, it is important to understand that the more layers you use, the more potential for intersecting wires. This translates to smaller openings.
As this can be daunting, feel free to reach out to our team with any questions you may have.
Wear and tear is inevitable regardless of how well you care for your woven wire chromatography frits. That said, you must implement best maintenance practices to prolong their lifespan.
Proper maintenance works to combat the accumulation of residual material from previous testing. This does two things:
Neglecting to establish a trusted maintenance routine, however, can lead to a slew of concerns. First and foremost, material from previous tests can make their way into new mixtures.
With this, the risk of encountering unusual peaks in your results is increased dramatically.
This leftover material can also become lodged in the pores of the woven wire, clogging them. As time passes, the hindrance this will have on your process will gradually grow, heavily impacting efficiency.
Regarding the physical well-being of your chromatography frit, long-term material accumulation can lead to substantial oxidation. This can then deform the mesh, resulting in performance inconsistencies.
However, it should be noted that a maintenance routine can cause more harm than good if not done correctly. More specifically, improper maintenance and handling can lead to bends, warping, and other blemishes.
It can even cause the mesh to delaminate or detach from its supportive framing.
As it is imperative to longevity and performance, understanding what best maintenance practices you should be integrating into your chromatography process is essential. This includes a cleaning routine, visual inspections, proper storage, and proper use.
When running material through woven wire chromatography frits, it is not uncommon for residual material to become lodged in the pore openings. It would be best to establish a regular cleaning routine capable of removing unwanted dirt, debris, and any other contaminants that can skew future results.
For most cases, a mild detergent can be paired with the agitations of a gentle cleaning brush to provide efficient cleaning. For more stubborn contaminants, compressed air can be utilized to dislodge embedded particles.
It is easy for performance-hindering blemishes to go unnoticed until result anomalies are prominent. Visual inspections are the easiest and arguably best way to detect these blemishes before they become a major concern.
During these inspections, you should be examining for things like loose wires, dents, bends, and any other form of structural concerns. If any faults of note are detected, you will want to either repair the section or replace the frit entirely.
This, of course, depends on the severity of the fault.
How your woven wire chromatography frits are stored is just as important as their implementation. Neglecting to store them in a secure area free of debris can cause premature wear or skewed results.
To that end, you must also ensure no moisture is present in the storage area. Moisture presence will increase the chances of corrosion like rust.
To ensure you get the most out of your chromatography frit, it is important that you always implement it within the designated usage tolerances. This entails ensuring parameters like pressure loads, run times, and support elements fall within the recommendations of the manufacturer of the chromatography machine.
It is also a great way to combat delamination and other troublesome faults.
In the right situation, replacing your woven wire chromatography frit will be necessary. But what are the calling signs you should look for to signify that it is time for replacement?
Well, first and foremost, increased pressure accompanied by a reduced flow of material is a key indicator that the pores have become clogged. While this can typically be remedied with a thorough cleaning process, these clogs can become permanent.
When this occurs, you will want to repair the isolated area rather than replace the entire frit. If it is a widespread clog, only then will you want to replace it.
Anomalies in your results can also be an indicator that there are imperfections in your chromatography frit. If these anomalies proceed or even get worse, replacement may be required.
To that end, if your system begins to leak during separation, this may be a sign that your frit is failing to sit in the housing properly. Wear and tear is often the root of this problem; replacement may be your only option.
Turning to everyday maintenance, it was stated previously that mild detergents can be used to clean your chromatography frits. That said, we often see harsher chemicals used, which can cause permanent damage to your woven wire.
Naturally, you are tasked with replacing the damaged frit to restore the accuracy of your results.
But something that is not in the hands of the user is industry standards and manufacture recommendations that will set time intervals in which you will want to replace your frit regardless of its condition. The time intervals you should follow generally take a calculated timeframe, usage volume, and environmental conditions into consideration.
Repairing a woven wire chromatography frit can be a cost-effective method to get your process back to producing accurate and repeatable results. This involves isolating only the damaged area of the frit.
To provide more insight, when repairing a woven wire chromatography frit, the damaged area is cut out. A new portion of mesh with the exact same specifications is then welded in its place.
This weld is applied with the utmost care by a seasoned welder, resulting in flush seams that have no impact on separation performance.
NOTE: Woven wire chromatography frit repair is typically reserved for frits with a diameter of 4 feet or larger. Replacement may be a more cost-effective option for chromatography frits that are smaller than this threshold.
