The 4S of Microwave Extraction: Speed, Simplicity, Safety and Savings

Not everyone has the same requirements and is looking for the same solutions. Nevertheless, speed, simplicity, safety, and savings are focus points in any daily work routine or purchase of new equipment. Hence, any microwave extraction equipment should cover these four aspects, “the 4S of extraction”. The question is: Where can you get the extraction equipment to suit your applications?

The first time I heard about the application of microwave instruments in chemistry was during my PhD studies at University. And I still remember how impressed I was after a demo in the headquarters of Anton Paar GmbH, where I used and tested a microwave instrument for my application. I was looking for a fast, easy and safe system that would allow me to optimize my process conditions and to save time and resources.

I realized pretty fast that all properties I wanted – speed, simplicity, safety and savings – were perfectly considered in the microwave reactor I was using. This “4S of extraction” is just the normal standard in any Anton Paar microwave instrument.

The modern approach: Microwave-assisted solvent extraction (MAE)

Nowadays dedicated microwave instruments are used to synthesize new compounds and to prepare samples for corresponding analyses. One special and important sample preparation procedure is solvent extraction. The traditional method, Soxhlet extraction, usually takes several hours. Now, with the modern microwave equipment, it is a matter of minutes. Microwave-assisted solvent extraction (MAE) is becoming the fast alternative to the traditional, time-consuming methods.

What is microwave-assisted solvent extraction?

MAE is a sample preparation method in which microwaves are used to heat up the solvents and to facilitate the extraction of the desired organic compounds from a matrix. Once the extracted substances are isolated, they are analyzed by means of High Performance Liquid Chromatography (HPLC) or Gas Chromatography (GC) for identification.

These investigations are important to assure consumers’ safety, e.g. by determining additives in food, plastics and pharmaceutical samples or even pesticides in environmental samples. You often have to fulfill regulations and follow defined standard methods from organizations like the United States Environmental Protection Agency (EPA) or ASTM International to conform to the corresponding legal requirements.

Anton Paar provides two modern microwave systems ready for MAE: Monowave EXTRA and Multiwave PRO Extraction Package. Both feature the 4S of extraction and the capacity to work according to the international directives mentioned above.

Monowave EXTRA is a dedicated solution for research and development. The sample is heated up with the highest and most homogeneous microwave field density to offer the utmost heating efficiency, which dramatically speeds up extraction times. Any extraction method is easily developed thanks to the instrument’s special features like an autosampler for treating different sample setups sequentially and an internal camera for real-time visualization of the process and the option of immediate reaction whenever necessary.

Monowave EXTRA Frontview

Monowave EXTRA

The Multiwave PRO Extraction Package is especially useful for scaling up experiments when higher sample amounts and higher throughputs are needed. Up to 16 samples are treated at the same time in a multimode cavity where the microwaves are distributed to achieve the homogeneous heating of all samples.

Multiwave PRO Extracion Package

Multiwave PRO Extracion Package

Here’s how both systems feature the “4S of extraction”:

  • Speed. Microwave-assisted solvent extraction (MAE) is up to 24 times faster than traditional methods like Soxhlet. The extractions take place in closed vessels. Hence we can work at higher temperatures than the solvent’s boiling point.“The higher the temperature, the faster the experiment: 10 °C increase doubles the process speed.”So, imagine how much time can be saved by using microwave irradiation in closed vessels. Let me give an example: Imagine you want to cook vegetables for lunch. You have a normal open pot and a pressure cooker that enables you to cook under pressure, above the boiling point of water. If you are very hungry and you want to eat soon, you will probably choose the second option.

    Consider, on the other side, that you would like to extract your sample with microwaves in an open system. You would certainly be able to do that, but you would lose the main advantage of microwave heating in closed vessels, meaning increased speed and a significant reduction of your extraction times.

  • Simplicity. It takes only 4 steps to start your experiment, and the microwaves’ extra features simplify your daily work in the laboratory. When you are working in a laboratory, you usually have to do several things in parallel, additionally document the experiments and finish your office work. So anything that simplifies your work is helpful.With Monowave EXTRA and Multiwave PRO, simplicity starts with the integrated software – it takes just a few steps to get your experiments to run. You do not have to be present during the experiment. Preparing experiments is just as simple, with easy-to-handle and frequently reusable vessels and caps for both systems. Fill in your sample, close it, place the sample vessel and start.Simplicity is further supported by the Monowave EXTRA standard features:

    ➨ Real-time visualization of the process by the integrated camera. You can observe directly on the screen how the process develops and judge if everything is running as expected. This is especially useful when developing a new extraction method.

    Monowave EXTRA Camera Polymers
    Monowave EXTRA Polymers through camera

    ➨ Automation of up to 24 sequential experiments – to increase your throughput and save time.

    Simplicity regarding extraction work-up is also considered in the Multiwave PRO Extraction Package: Glass filter inserts for extraction of solids. You can easily remove the solid matrix from the solvent containing the extracted compounds.

  • Safety. It is always comforting to know that the device you are using passed the strictest checks and works without compromising the user safety. It does not matter if it is a car, a motor bike, a drill, a washing machine or a microwave oven. Anton Paar pays great attention to safety. This is reflected both in Monowave EXTRA as well as in the Multiwave PRO Extraction Package.The best way to safety is:➨ to have everything under control: Both instruments are therefore equipped with a temperature and pressure sensor to continuously measure the two most important parameters.

    Monowave EXTRA with its infrared sensor and hydraulic pressure sensor accurately measures and registers temperature and pressure during the whole experiment.

    Multiwave PRO Extraction Package, complementary to the infrared sensor which measures the temperature in all 16 vessels, includes a pressure and temperature sensor which delivers the value of those parameters for a reference sample.

    ➨ to not burn your fingers: You do not have to handle hot and pressurized vessels; the corresponding cooling systems of the instruments rapidly and effectively cool down the processed samples to temperatures that allow for a safe vial/vessel opening.

    This bring us back to the topic ”open vessels/systems”. To eliminate the risk to users, we do not offer open systems for doing any kind of microwave process.

    In a chemical laboratory anything can happen; there is a lot of material standing around and we do not want to have anything falling into the microwaves’ field.

    Therefore in Monowave EXTRA a swiveling cover completely closes the monomode cavity, whereas the Multiwave PRO Extraction Package has an actively closed self-resealing safety door that cannot be opened until the microwave field is no longer present.

  • Savings. It is important to care about your resources and the environment. Microwave-assisted solvent extractions require up to 10 times less solvent than classical methods to get the same results. This is due to the use of closed vessel systems, which prevent evaporation. No refilling is required, which brings the solvent consumption down to the necessary minimum. Another advantage of the closed vessel systems: The risk of contamination during the extraction process is avoided.

I am currently working in the field of analytical and synthetic chemistry with microwave reactors regarding their uses and benefits. Our aim is to optimize our instruments, to simplify their use and to offer appropriate solutions for the different applications. Our motto: The best way of doing things is to do them well, offering useful solutions that guarantee satisfaction.

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