Rob ten Haaft
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For many years, Mass Flow Controllers (MFCs) and Mass Flow Meters (MFMs) have been used in Analytical instrumentation. There are some distinctive applications like carrier gas control or mobile phase control in Gas Chromatography (GC) and Liquid Chromatography (LC). I discovered that there are a lot more applications of Mass Flow Controllers in analyzers then I could imagine when entering the world of Mass Flow Controllers after many years working in Analytical Chemistry.

One application I would like to focus on in this blog is Mass Spectrometry or shortly, as chemists like to use abbreviations, MS. Mass Spectrometry comes in many forms and is often coupled to Gas Chromatography and Liquid Chromatography. A Mass Spectrometer coupled to a Gas Chromatography (GC) is called a GC-MS and a Mass Spectrometer coupled to a Liquid Chromatography (LC) is called a LC-MS.

Where are Mass Spectrometers applied?

The market for Mass Spectrometers is huge and expanding. The instruments are used for Analytical Research in general but increasingly important in Food Research. Research concerning aging of whiskey and fingerprinting of red wine to determine the origin of the grapes are some examples. Another emerging market is Biopharmaceutical Research where Mass Spectrometers are used to study proteins and how these proteins are digested in living organisms. There are even Mass Spectrometers on Mars (!), where the martian soil is studied.

schematic mass spectrometer

Figure 1: Mass Spectrometer(schematic)

What is a Mass Spectrometer?

The Mass Spectrometer is often compared with a weighing scale for molecules. Every molecule is built up from atoms and every atom has its own atomic mass and this is “weighted” by a Mass Spectrometer. Before it can weigh the different atoms that are present in one sample, the atoms have to be separated from each other. This is done by charging the atoms (to form ions) and using a magnet to deflect the path that the ion is following. The lighter the ion, the more influence the magnet has and the bigger the deflection. The detector detects where the ion hits and this is a measurement of the weight.

The place where the ionization takes place is called the ion source and there are a lot of different types of ion sources, depending on the matrix of the sample and on the ions that you want to form. The ionizing part is the most interesting part from a Mass Flow point of view because in this part different gases are used, depending on the technique of ionization.

There are two main techniques: hard ionization and soft ionization. With hard ionization techniques, molecules in the sample are heated and fragmented down to atomic levels giving information about the atomic structure of the molecule. With soft ionization techniques the molecule stays more intact giving mass information of the molecule. This is used in Food and Pharma research and has become very popular in the last decade.

Let’s look into detail to one of the most popular soft ionization techniques, the Electrospray Ion Source. The EIS vaporizes the liquid (coming from a Liquid Chromatograph, for example) by leading gas alongside a charged needle to form an aerosol spray. Leading a counter gas flow through the formed spray will evaporate most of the liquid that you do not want to measure, leaving the charged droplets going into the Mass Spectrometer.

atmospheric pressure chemical ionization electrospray ionization electroscopy

Figure 2+3: Electrospray ionization (ESI)

Mass Flow Controllers and Evaporation used in Electrospray Ion source

The interesting part is that the flow needs to be very constant as you want the process of forming droplets and evaporating solvent to be the same, day after day and at different locations with different circumstances. An important parameter in this reproducibility is the gas flow. By using Mass Flow Controllers for Nebulizer gas and Evaporation or Drying gas, the ion source will always have reproducible gas flows.

Our solutions department can design compact gas modules for analytical applications to supply gases for ion-source combined with other gas flows with high accuracy and good reproducibility. Combining components like pressure switches and/or shut-off valves with the flow channels can give a compact gas handling module to fit in the small footprint demanding designs of the Mass Spectrometers. Furthermore, the changes on leaks are decreased significantly as the whole manifold can be leak and pressure tested before it is shipped to the customer.

If you would like to learn more about Bronkhorst customized flow solutions, you can watch this Video or visit our website.

Sandra Wassink
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Did you know that natural gas is odorless? I didn’t… I always find it having a penetrating sulfur scent. Well, it appears that this penetrating scent is added to the natural gas on purpose. Let’s see why this is.

As natural gas is combustible and odorless by nature, the government requires some safety measures here. Many countries have established safety regulations how to handle natural gas and which gas needs odorisation. This is mostly done by the Health and Safety department (HSE) of the local government.

What about natural gas odorisation?

Today’s question is about this subject. Why does gas smell when it is odorless by nature? This is the point where gas odorisation comes in.

Odorisation of natural gas is done to act as a ‘warning agent’ in case of leakage. The idea is that people can smell the gas prematurely if it is present. Because, if there is too much gas present it can be explosive.

As shown in the picture, the LEL (Lower Explosive Limit) and UEL (Upper Explosive Limit) are crucial here. If the concentration of the combustible substance present in the air is too low (< LEL), than no combustion will occur. It the mixture is too rich (> UEL), there is a huge amount of gas in the air and only partial combustion will occur. Gases become dangerous in between the LEL and UEL. Therefore, it is most important for people in the surroundings to smell the gas in time, before the concentration is too high and it exceeds the LEL.

As a result, it is stated in the safety regulations that natural gas has to be detectable at a concentration level of 20% of the LEL and this is done by odorisation. Needless to say that the odor used in the gas is not dangerous to people’s health.

When is an odor added to gas?

This depends on the type of gas line. We know ‘distribution lines’ and ‘transmission lines’.
Distribution lines are local natural gas utility systems that include gas mains and service lines, such as the commercial gas used at domestic environments. All these distribution lines need to be odorised. For the transmission lines it is stated in the regulations when to odorise it.

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Picture LEL and UEL

THT, Tetrahydrothiophene

For the odorisation there are many different odorants available, such as Tetrahydrothiophene (THT) and Mercaptan. Selecting the odorant depends on the properties of the gas to be odorised, pipeline layout, ambient conditions etc. Tetrahydrothiophene or THT is a well-known odor. THT is under ambient conditions a colourless volatile liquid with an unpleasant smell.

Controlled supply of THT using mass flow controllers

Bronkhorst had the pleasure of developing a solution for a Dutch customer to add THT to their biogas. Biogas was generated from anaerobic decomposition of organic matter and upgraded to natural gas quality to inject into the Dutch natural gas main. As commercial natural gas in the Netherlands has to contain at least 18mg of THT per cubic meter gas, the process of adding this to the commercial gas had to be done really accurately.

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ATEX Zone 1 Coriolis Mass Flow Meter

The traditional approach to add THT is using a pump with a fixed stroke volume. However, low gas flow rates using a pump for batch-wise injection may lead to liquid THT remaining in the gas lines. THT may not be mixed well with the gas and might have the wrong concentration. A homogeneous injection of THT is therefore much better. Besides this, THT is a relatively expensive odor which also makes an accurate injection very much desired.

A better solution here would be using a combination of a pump with a Coriolis mass flow controller, in our case the mini CORI-FLOW™ series mass flow controllers. The Coriolis instruments make it possible to dose both continuously as well as accurately.

Read more about this application in our application note 'Controlled supply of odorant to natural gas'.

Hazardous areas

Something to be taken into account is the classification of the area. As gases in principle are explosive, it is very common for the environment around gases to be classified as a hazardous area. Most common classifications (in Europe) are marked as ATEX zone 1 or zone 2. Just make sure to select the right material to use.

For solutions such as THT odorisation processes, Bronkhorst can offer both ATEX/IECEx zone 1 and zone 2 solutions. Our mini CORI-FLOW Exd mass flow meter, for zone 1 applications, is a collaboration with one of world’s leading manufacturers in explosion protection, Electromach member of the R.STAHL Technology Group.

Check out our Coriolis mass flow meters for applications in hazardous areas and our thermal instruments for Atex zone 1.

James Walton
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Since the day of their introduction Instrumentation devices have always been required to evolve. One of the main reasons for this is to accommodate new, better and more complex communication protocols.

What a lot of people still do, due to ease of use and consistency is specify instruments with analogue or RS-232 serial communication. Analogue communication (4-20mA, 0-5v or 0-10v) and RS-232 which was the original way in which computers communicated was the original, mainly due to cost and available technology.

It is still a very robust and solid way to send and receive information over a small group of instruments however it does have some very practical set-backs. As a point-point communication protocol it requires a port both on the instrument and the controller, this can be very limiting in size affecting both the amount and length of cables needed.

The development of Fieldbus communications meant it became possible to have multiple (100’s) of instruments connected through only one communication port at the controller level. This means that you had a huge reduction in both the number and length of cables needed. This development allowed the complexity to increase and size decrease of instruments containing multiple sensors.

As with VHS and Betamax there will always be competing technologies and ‘bus’ development was no different. Of course everyone hopes for a single unified solution because it makes things simpler, cheaper and more efficient. However the reality is that most ‘buses’ are utilised differently in different industries.

Different industries are described as either; a ‘process fieldbus‘ used in many process automation applications (flow meters, pressure transmitters and other measurement devices) or a ‘device network’ which is a large number of discrete sensors are used, motion, position etc., the best example of this is in automotive manufacturing.

There is an IEC standard that was developed for the European Common Market and interestingly I have learnt that the common goal was not focused on commonality but more the elimination of restraint of trade between nations. This standard is IEC 61158, it is almost 4000 pages long. Issues of commonality are now left to the consortium that supports each of the standard fieldbus types.

What next is always a good question, Ethernet based communication systems are one area that has seen large development over recent years and its definitions are being added into the International standards.

In all of this, what is our involvement in Fieldbus. As you may know, we are mainly involved in Process and control industries. We support almost all of the major bus systems out in the market and also have our own in-house ‘Flow-bus’ system that can be used link multiple instruments together. You run them through a single PC running our Flow-Plot or Flow-View software.

The latest addition to the communication range is the ‘Gateway’ solution. This allows multiple or manifold instruments on a Flow-Bus network to communicate with PROFIBUB or PROFINET DP through a specific fieldbus interface. This can be a very cost effective solution as multiple PROFIBUB or PROFINET DP instrument can become very expensive, very quickly.

Bronkhorst Field-Bus Technology

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James Walton
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Chromatography has a long and interesting history. To discuss such a vast subject is a challenge, people are understandably passionate about such a subject. There is huge potential of not charting or discussing an area another person believes to be critical, for example we are discussing here Liquid Chromatography, we didn’t feel there would be room or time to discuss Gas Chromatography (GC) in an appropriate amount of detail.

So before we begin, please do let us know if you have any additions or corrections, we are always open to learning more from experts within any industry as that helps us to grow and learn.

Since the mid-19th century multiple types of chromatography have been developed. To start at the beginning, the word ‘Chromatography’ stands for ‘color writing’ and was initially used for the separation of plant pigments such as chlorophyll (which is green) and carotenoids (orange and yellow). However, it soon became apparent that it could be used for a wide range of separation processes as new forms of chromatography were developed starting in the 1940s.

In the modern analytical solutions discussed here, from HPLC to GC and SCFC we have an instrument that is currently in use, allowing the finished Analytical Instruments to achieve their full potential. We have provided solutions for liquid and gas applications, using thermal mass flow technology allowing manufacturers to achieve their end goals and meet the customer’s expectations.

As solutions providers we have relationships with all of the leading manufacturers around the world, these relationships are based on partnership where we provide the flow expertise. Our goal is to deliver the solutions of the future by listening to and understanding the trends in the market now.

One of those techniques is High Pressure Liquid Chromatography (HPLC).

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Schematic drawing of a typically HPLC instrument

HPLC stands for High Performance Liquid Chromatography and is a technique used to separate and allow the user to quantify different compounds. A high pressure pump is used to push the solvent through a column, due to the interaction between the compounds and the column material a separation of different compounds is possible. From here you can analyse the time taken to elute the compund ot the amount of compound detected.

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Schematic of our instruments installed in the HPLC system

UPLC stands for Ultra High Performance Liquid Chromatography and is a special version of HPLC. Compared to HPLC, UPLC columns contain smaller particles sizes (2 um for UPLC vs 5 um for HPLC), which results in a better separation of compounds. The pump pressure in UPLC can go up to 100MPa in comparison to HPLC where this is 40MPa. UPLC has, in some applications, improved chromatography significantly. The run times are much shorter; therefore very fast analysis is possible. UPLC is the abbreviation mostly used in writing; however this is a trademark technology of one of the major corporations in this field and is officially called UHPLC (Ultra High Performance Liquid Chromatography).

SCFC, the last trend we will discuss today is the growth of research into the way that liquid CO2 can be used as a super-solvent. With the ever increasing cost of chemical solvents used in the mobile phase, both purchase and disposal is increasing yearly. Developing a system that utilizes a solvent, such as CO2, that can elute different compounds and provide a gradient effect purely through adjusting and controlling the system pressure is an incredible potential cost saving development. However as with all things, the cost reduction has to be off-set by the cost of installation of such systems. That day is only getting closer, but we are not yet at the point of wide-spread liquid CO2 solvent usage.

  • Working with liquid CO2 can be a real challenge and one that we take seriously, our Coriolis and EL-Press instruments are perfect for this application giving flow and pressure control without the need for a thermal based system that would affect system integrity.

The industry is changing, that’s obvious! We will be on top of this………

James Walton
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Having worked in both the Life Sciences and Analytical industries I am sympathetic to the ever increasing demands for small foot prints and faster instruments. It has been a continuing trend for many years that lab real-estate has become more and more expensive; this led to a drive for footprint reduction of instruments. You had to make sure that size didn’t make you expensive in bench space.

One of the drivers behind this process was the NeSSI system initiative (New Sampling/Sensor Initiative), sponsored by the Centre for Process Analysis and Control. The aim was to reduce the overall costs of engineering, installing and maintaining chemical process analytical systems.

In the NeSSI system, mass flow and pressure meters/controllers needed a standard footprint of 1.5’’.

This footprint is perfect for a large number of applications and end users, even for some of the Life Science OEM companies that have room to spare in their systems. However when you are re-designing your system and you have the chance to incorporate new technology, look at the placement of existing technology and maybe add more it helps if you can reduce the footprint of the components that you use even further.

Reducing the footprint of a known, working technology has challenges of its own. The design and function of which will be driven by the physical characteristics of the measurement principle and therefore the sensor that it uses. To change this you need to look at alternative measurement technologies as a way to achieve the end goal of the industry, same functionality, same signal, smaller package.

Working in conjunction with the TNO, the Netherlands organisation for applied scientific research we designed a new range of mass flow and pressure meters/controllers built around MEMS technology. This allowed us to offer solutions with a footprint of 0.75’’, halving the footprint and offering ultra-compact flow controllers.

This has given our customers:

  • Compact assembly ensuring space efficiency
  • Analog or digital communication
  • Top mount modules, easily accessible
  • Pre-testing ‘’Plug and Play’’ manifold assemblies, reducing customer test requirement

To maintain the usefulness of the new instrument you have to have the same functionality. Along with a sensor on a chip, we need a new, smaller control valve, filter options and a smaller pneumatic shut-off valve. To save even more space and build time, customers requested a down-ported version.

The final addition that makes full use of the space saving created by the addition of new technology was to create a manifold system where a customer can design a number of flow channels into a manifold, all well within the internal space limitations they have for their instrument.

IQ+ Manifold Solution

This is one of the key themes of our blogs and it is referred to time and again. The Solutions based approach, ending up with a bespoke solution not a standard product with compromises. Innovation in technology must be driven by the customer. If you do not think that a standard flow or pressure solution will meet your needs then let us know and challenge our team, we will be your low flow fluid handling specialist.

Check out our smallest mass flow and pressure meter/controller

Check out our Ultra Low Flow Coriolis Instruments

James Walton
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As with any inter-dependent parameters there are consequences for changing one parameter if the controller of the other is responsive. For example; if you installed a mass flow controller and a digital pressure controller in-line, each with their own inputs and outputs, changing the set-point on the digital pressure controller would adjust the valve and therefore the flow. This reaction would be detected by the mass flow controller as either a decrease or increase in flow and the mass flow controller valve would adjust accordingly to achieve its given set-point. This second reaction would then be seen as a change in pressure by the digital pressure controller and you can see how quickly this would become a feedback loop of increasing instability.

One of the most frequent challenges that we come across, and one that people are always surprised we can solve, is the ability to control and meter flow and pressure in-line. Many of the applications we are involved in require control and measurement of the flow and pressure of the fluid. However, as the two parameters are different but inter-dependent it can make it difficult to determine the optimal process conditions in which both parameters are fully supporting each other. Our experience teaches us that each case has its own unique solution. We learned by experience that it is very beneficial to draw together the process owners of the application under discussion. I/we use this ‘drawing’ skill to help identify which areas are critical and where value could be added through the use of digital instrumentation. This can make it easier to determine what the best course of action is.

Applications for use:

The need to control/meter both pressure and flow can be important in:

• Consumption reactions • Biochemistry • Fuel cell development • Burner/Ignition lance applications • AiR Permeability testing

Application Examples:

If you need to measure the AiR permeability of medical packaging; you need to set a standard pressure while also metering and controlling the AiR required to maintain the standard pressure. This measure gives you the flow required to achieve stability and therefore the AiR permeability.

In consumption reactions you may want to hold your reaction vessel at a set pressure and control/meter the feed gas to maintain the set pressure. This set-up, with electronic instruments and PC/PLC communication software will give you total consumption, consumption rate and allow you to profile the life cycle of the reaction you are conducting.

Adding digital control can allow you to control maximum flow as you build up to desired pressure levels which can be important in certain applications.

As with all application solution requirements, talking the application aim through with your supplier can be crucial to getting the best result.

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