Mars x press microwave digestion system

Cd and Cu concentrations were analyzed in uterus tissue, using a Hitachi Z-8270 GF-AAS flameless atomic spectrometer (Hitachi, Ltd., Tokyo, Japan) with Zeeman-type background correction, autosampler and pyrocoated tube. Zn, Ca and Mg were determined using flame atomic absorption spectrometry on F-AAS (Avanta GM; GBC Scientific Equipment Pty Ltd., Melbourne, Australia). Tissue sample digestion was performed with a MarsXpress microwave digestion system (CEM Corporation, Matthews, NC, USA) with nitric acid. For determination of Cd and trace elements concentrations, the samples were prepared in duplicate. To assess Cd, Cu, Mg and Ca, mineralized tissues were additionally diluted (two to eight times) in relation to the measured metal. For each sample, three parallel independent determinations were made and the mean values were accepted. The concentrations of Cd and Cu, Zn, Ca, Mg in the tissues were reported as ng/g wet tissue and µg/g wet tissue. The accuracy of these measurements was confirmed against reference material (Bovine Liver 1577b). For 96% of the determinations, the repeatability error did not exceed 10%. The precision of the measurements, expressed as a coefficient of variation for Cd, Cu, Zn, Mg and Ca in the range of the samples analyzed in this study was <5.6%, <3.3%, <9.4%, <4.8% and <9.5%, respectively.

The levels of Al, As, Cd, Cr, Cu, Hg, Mn, Ni, Pb and Se in dried seaweed were analyzed by microwave digestion and ICP-OES based on our previous report^{26 (link)}. Briefly, the samples (0.5~2 g) and 6 ml nitric acid were transferred to Teflon-PFA vessels. Samples were digested at180 °C for 30 min by a MARS Xpress Microwave Digestion System (MARS 6, CEM Corporation, Mathews, NC, USA).Afterward, the digested solutions were evaporated to 0.5 ml with an electro-thermal plate and finally diluted to 5 or 10 ml with de-ion water for instrumental analysis. The solution was analysis by ICP-OES (Agilent 720ES, Agilent technologies Inc., USA). Limits of detection (LODs) were defined as 3 times the standard deviation of 10 runs of blank measurements. LODs of Al, As, Cd, Cr, Cu, Hg, Mn, Ni, Pb and Se were 0.015, 0.012, 0.009, 0.008, 0.009, 0.005, 0.007, 0.008, 0.010 and 0.045 mg/kg respectively.

Soil samples (150 mg) were weighed, and the total N concentration was determined using a Vario MAX CN elemental analyser (Elementar Analysensysteme GmbH, Langenselbold, HE, Germany). Soil samples (0.05 g) were soaked in 6 mL nitric acid (HNO₃) and 3 mL hydrofluoric acid (HF) overnight and boiled to invoke digestion using a Mars X press Microwave Digestion System (CEM Corporation, Matthews, NC, USA). Next, 0.5 mL perchloric acid (HCLO₄) was added to remove the acid, and then the solutions were cooled and adjusted to 15 mL to measure total P^{57 (link)}. Determinations were conducted using an inductively coupled plasma optical emission spectrometer (Optima 5300 DV, Perkin Elmer, Waltham, MA, USA). After determining total N and P, the soil N:P and averages for each site were calculated.