Development of a fully automated open vessel focused microwave digestion system

The use of microwaves in the acceleration of digestion and colour development in the determination of total Kjeldahl nitrogen in soil

“…This was regarded as an improvement on the method reported by Alvarado et al 6 Although only a 2-fold decrease in preparation time was achieved in the case of 'real' samples, no hydrogen peroxide was required to complete the digestion procedure. In the case of the method reported by Feinberg et al 7 hydrogen peroxide had to be added to achieve complete extraction of the nitrogen. In terms of throughput of samples the Star 6 had the ability to process six samples at once compared to the system reported by Collins et al 8 which could only process one digest at a time.…”

“…The method did however require continuous attention from an operator, turning the microwave power on and off so as not to allow the pressure to exceed that allowed by the glass tubes. Later developments, again in investigating the digestion of food, have been reported by Feinberg et al, 7 with the introduction of a more sophisticated open-vessel focused microwave digestion system. Feinberg reported that the use of a metal catalyst was not necessary in this case if hydrogen peroxide was used.…”

“…After transport through a mixing tube the sample was then mixed with reagent (1) at merging zone (5). Colour development took place in the thermally (7) or microwaveheated coil (12). Detection then took place in the dual diode colorimetric detector flow cell (8), and signals were integrated (9).…”

Microwave digestion procedures for environmental matrices

“…This is of particular value in a multi-element situation when no single digestion procedure gives good results for all the elements required and a method is needed to obtain the best overall performance. In addition, Feinberg et al 67 related digestion programmes with the nature of the sample matrix using an empirical modelling approach. A preliminary study using Kjedahl nitrogen determinations in food samples to define reference digestion procedures was found to be very effective for precisely defined samples.…”

Rapid Determination of Total Kjeldahl Nitrogen Using Microwave Digestion

“…The method, however, did not report the maximum digestion temperature reached in the process, and the heating process was controlled only by turning the microwave power on and off. The open-vessel focused microwave digestion of food reported by Feinberg, Suard, and Ireland-Ripert [5] showed that it required 40 min, even with the use of a strong oxidation reagent, hydrogen peroxide, as a catalyst. Again, the operating temperature was not reported in their paper.…”