Milestone Ethos EZ - Basic Microwave Chemistry Rules

BASIC RULES OF MICROWAVE CHEMISTRY
The basic rules of chemistry also apply in a microwave field. The conditions outlined in the Milestone
cookbooks describe optimized microwave processes of particular materials. The procedures in
Milestone cookbooks are only guidelines. Please refer to your local Milestone Application Specialist for
any modifications or suggestions.
Basic rules are described below:
• All vessels must contain same type and amount of sample/reaction mixture.
• Be sure the minimum and maximum volumes are set in accordance with the rotor
specification.
• The maximum volume has always to be approximately 50/60% of the total volume of the
vessel.
• Never use a blank in the reference vessel, because a possible exothermic reaction can not be
monitored.
• Never heat water in the reference and/or in one of the standard vessels, in any digestion
cycles.
• Before adding reaction mixture rinse the vessels with distilled water in order to remove any
electrostatic field.
• To prevent hot spot place the sample on the bottom of the vessels, if part of the sample stays
on the inner wall of the vessel, wet it by adding acids drop by drop.
• If during the addition of the reagents at your sample an exothermic reaction is observed,
leave the vessel under fume hood for five minutes, before closing
• Before running any test check that the method (temperature and pressure) is suitable for your
type of reactor.
• For method development use a small sample amount (e.g. 100 mg), low temperature, low
power and short time
• For strong exothermic reactions add 2 ml of distilled water
• Periodically check the status of vessels, covers, shields, adapters, springs.
• Always check the reference cover especially at level of the thermowell.
• After starting the microwave program always check if the temperature and/or pressure sensor
are free to rotate.
• Never open the reaction vessels at high temperature or above the boiling temperature of the
reagents
• After digestion open the vessels slowly. In particular for organic samples that generates a lot
of yellow-red gases (NOx) during the digestion: n(CH
2
) + HNO
3
= nCO
2
(g) + NOX(g) + H
2
O
(reaction between organic samples and HNO
3
).
• Do not use ice to cool down the rotor after microwave heating as the thermal shock could
damage the safety shields.
Before using Milestone labstations read carefully the user manual.