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Prior to starting Mars, here are important safety guideline for using the MARS.

Safety Guidelines
Microwave sample preparation imposes a unique set of safety considerations beyond the basics of good laboratory practice.

1. All vessel components must be dry and free of particulate matter. Drops of liquid or particles will absorb microwave energy, causing localized heating which may char and damage vessel components, leading to possible vessel failure.

2. Ensure that the vessels are completely vented of built-up reaction gases and completely depressurized before completely open the vessel. Failure to do so could potentially result in ejection of acid and injury to the operator.

3. NEVER attempt to digest samples larger than the recommended maximum amount if the organic content and composition of the sample is unknown. Unknown samples should always be predigested for a minimum of 15 minutes in an unsealed vessel without any heating prior to attempting closed vessel microwave digestion.

4. DO NOT heat concentrated base or salt solutions inside the vessel. Microwave heating of such solutions causes precipitation of salts and formation of crystal deposits which absorb microwave energy and may char into the vessel or electrically arc, leading to possible vessel failure or explosion.

5. The vessels have a maximum recommended hold time of 30 minutes at 240oC. Hold times longer than 30 minutes at the maximum temperature or higher may result in softening of the bottom of the support module and may damage the vessel.

Be safe when you use this instrument!

Procedures:

The following instructions for use of the microwave digester must be followed very carefully. Do not perform any steps until you are absolutely sure that step is understood.  Ask EM1 technician to show you when you are unsure prior to proceeding.

The Microwave Accelerated Reaction System (MARS)  is located in Green 044.

When the instrument is initially turned on (switch on right side of unit near the back).  Two choices appear on the display:

Edit/Create Method and Load Method

An appropriate method should already be programmed into the unit for your sample. DO NOT Edit/Create your own method. The (+) and (-) touchpad keys on the front of the unit will allow you to highlight Load Method. Press Select.

Next screen gives the choice of CEM or User Directory. Highlight User Directory and press Select. Highlight the appropriate method and Press select to load method.

Load Method (Select) --> User Directory (Select) --> Appropriate Method (Select)

For Soil select specific method based on your need.  The method is created by EM1 personnel for your need depending on the number of samples you are digesting.  Now you must prepare your sample(s) for digestion.

If you have any questions, please contact Guangchao Li at gcli@stanford.edu or call 724-3220.

You can get more detailed information by checking out our FAQ.