Nitric acid 65 suprapur

The collected samples were washed with Milli-Q water, length measured using a ruler, dissected, and the tissues were separated on-site, frozen, and stored at -20 °C in clean polypropylene bottles until acid digestion. The samples were weighted, lyophilized (Adolf Kühner, Birsfelden, Switzerland), and water content was calculated as performed in our previous study (Ngelinkoto et al., 2014 ). The digestion of samples was performed according to the methods described by Rashed (2001) (link), Sivaperumal et al. (2007) and Ngelinkoto et al. (2014) with minor modifications. Briefly, a portion of edible tissue from each sample was freeze-dried (Adolf Kühner, Birsfelden, Switzerland) and ground to obtain a fine powder. Approximately 1 g was digested in 10 mL of a suprapur HNO₃ (Nitric acid 65% Suprapur, Merck KGaA, Darmstadt Germany)-HClO₄ (Perchloric acid 70%, Merck KGaA, Darmstadt Germany) mixture (3:1), in Teflon bombs and heated overnight at 110 °C. The digested samples were cooled at room temperature and centrifuged. Inductively coupled plasma mass spectroscopy (ICP-MS) analysis was performed after dilution with suprapur 1% HNO₃ (Nitric acid 65% Suprapur, Merck KGaA, Darmstadt Germany). Acid dilutions were performed using ultrapure water (Millipore, Milli-Q, 18MW, Merck, Darmstadt, Germany).

Minimal essential medium Eagle (MEM), non-essential amino acids (NEA) and culture dishes were provided by Biochrom (Berlin, Germany). Fetal calf serum (FCS) was purchased from PAA Laboratories (Pasching, Austria). Penicillin–streptomycin solutions, trypsin, cacodylic acid (DMA^V, ≥99% purity) and hydrogen peroxide solution (30%, Suprapur) were products of Sigma Aldrich (Steinheim, Germany). Nitric acid (65% Suprapur) was from Merck (Darmstadt, Germany). Sodium(meta)-arsenite (≥99% purity) and Alcian Blue were from Fluka Biochemika (Buchs, Germany). The cell-counting kit-8 (CCK-8) was obtained from Dojindo molecular technologies (Munich, Germany) and the inductively coupled plasma mass spectrometry (ICP-MS) elemental standard (As, 1 mg L^–1) from Spetec (Erding, Germany). All other chemicals were of p.a. grade and were from Merck (Darmstadt, Germany) or Sigma Aldrich (Steinheim, Germany). HepG2 liver cells were supplied by the European Collection of Cell Cultures (ECACC; number 85011430, Salisbury, UK). The urothelial cell line UROtsa was derived from a primary culture of a normal human urothelium through immortalisation with the SV-40 large T antigen. This cell line was kindly provided by Prof. M. Stýblo (University of North Carolina, USA).