Microwave-assisted sample combustion: a technique for sample preparation in trace element determination.
A novel digestion procedure based on sample combustion ignited by microwave radiation is proposed for organic samples. Certified samples of bovine liver, pig kidney, and skim milk were used as examples to demonstrate the performance of the proposed procedure. Cadmium and copper were determined in these samples by electrothermal atomic absorption spectrometry. Samples (between 50 and 250 mg) were wrapped with paper and placed on a homemade quartz holder that was positioned inside to quartz vessels used in a commercial microwave oven. Ammonium nitrate solution was added to the paper, and vessels were pressurized with oxygen to 15 bar. The rotor containing four vessels was placed inside the oven, and microwave radiation was applied for 20 s at 1400 W. Combustion was complete in few seconds, and an additional reflux step, which was optional, was applied. The agreement to the certified values was between 96 and 105% for both analytes. Only with the combustion step, the residual carbon (RC) was below 1.3%. The RC decreased to less than 0.4% when an additional reflux step with concentrated nitric acid was applied.
Flores
Erico Marlon de Moraes
EM
Departamento de Química, Universidade Federal de Santa Maria, 97105-900 Santa Maria, RS, Brazil. flores@quimica.ufsm.br
Barin
Juliano Smanioto
JS
Paniz
José Neri Gottfried
JN
Medeiros
João Alfredo
JA
Knapp
Günter
G
D000818:Animals; D002104:Cadmium / Q000032:analysis / Q000737:chemistry; D003300:Copper / Q000032:analysis / Q000737:chemistry; D007668:Kidney / Q000737:chemistry; D008099:Liver / Q000737:chemistry; D008872:Microwaves; D008892:Milk / Q000737:chemistry; D013054:Spectrophotometry, Atomic / Q000295:instrumentation / Q000379:methods; D013997:Time Factors; D014131:Trace Elements / Q000032:analysis* / Q000737:chemistry*
D014131:Trace Elements; D002104:Cadmium; D003300:Copper