microwave digestion

MARUM - Sediment Geochemistry - Leobener Str - D-28359 Bremen - Germany

Marine Geochemistry - Laboratory Methods

Microwave digestion with MLS Ethos 1600

Microwave digestion
type	MLS Ethos 1600
spec	Microwave digestion system with PTFE digestion cups that fit into both, digestion and evaporation rotors. Vapor condensation and neutralization. Process control by PTFE coated pressure and temperature sensors.
solutions	HNO3, conc. 65% , suprapure Merck # 100441 HF conc. 47-51%, trace select, Fluka # 47559 HCl conc. 30%, suprapure Merck # 100318 pure water - 18.2 MOhm water prepared with MilliQ ion exchanger cleaning solution for cups - 3.25% HNO3 suprapure (5 mL HNO3 65% in 1L pure water)
sample size	approx. 50 mg weighed directly into PTFE sample cups
digestion solution	3mL HNO3, 2mL HF, 2mL HCl
pressure digestion	time [min]	2								1	2	3	4	6	12	30	30
pressure digestion	Power [Watts]	250								0	250	550	800	1000	700	vent.	cool
Evaporation rotor
Evaporation	time [min]	50
Evaporation	Power [Watts]	350
Homogenization	add 0.5 mL HNO3 and 4.5 mL pure water
	add 0.5 mL HNO3 and 4.5 mL pure water
	time [min]	15								30
	Power [Watts]	400								vent
dilution	add 45 mL pure water and transfer solution from digestion cups to 100 mL Greiner sample vials
Cup Cleaning	use 8 mL HNO3, 5%
	time [min]	5								5	5	10
	Power [Watts]	250								400	550	vent.
	rinse with pure water


	dry at 60°C in dryer box
tips + tricks	The advantage of the MLS Ethos system is, that the samples remain inside the same PTFE digestion cups during all steps. This reduces contamination sources digestion cups have to be perfectly dry externally use antistatic fan to remove static load from digestion cups digestion cups are constructed for max. 230°C and max. 30 bars -> higher p,T will result in irreversible damage power settings have to be reduced when the digestion rotor is not completely filled with samples

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