Icap 6000 icp oes analyzer

To a solution of 1 equivalents of Cu²⁺ (0.5 mM in MeOH : H₂O 4 : 1) and 10 equivalents of Co²⁺, Mn²⁺, Ni²⁺, Fe³⁺ and Zn²⁺ (5 mM each in MeOH : H₂O 4 : 1), 6 mg of peptoid Helix HQT i + 3 were added and the mixture was allowed to shake for 30 min. The solvent was then evaporated and the water solution was lyophilized overnight. To the lyophilized powder, 1 mL of H₂O was added; the mixture was shaken for 5 min and centrifuged 15 min to separate the solution and the precipitate. After the centrifugation, the water was removed and this process was repeated another 9 times. To the precipitated metallopeptoid, 0.2 mL of 69% nitric acid HNO₃ was added, the mixture was mixed thoroughly for 30 minutes, followed by the addition of water to get 10 mL final volume. This experiment was done 3 times. When ACN was used as a solvent, 1 equivalent each of Cu²⁺, Co²⁺, Mn²⁺, Ni²⁺, Fe³⁺ and Zn²⁺ was added (1 mM each in ACN : H₂O 17 : 3) to 5.6 mg of peptoid Helix HQT i + 3. All solutions were filtered by 0.2 μm filters prior to ICP analysis by a Thermo Scientific iCAP 6000 ICP-OES analyzer. Wavelengths used for the detection of the different metal ions were as follows: 324.7 nm for Cu, 228.6 nm for Co, 257.6 nm for Mn, 231.6 nm for Ni, 213.8 nm for Zn.

The elemental composition of the total community was determined from the concentrations of particulate organic carbon (POC), particulate organic nitrogen (PON), and POP at steady state. Measurements were done in triplicate by filtering 5 mL of culture over a pre-combusted glass fiber filter (Whatman GF/F; for POC and PON) or over a 0.45 μm nitrocellulose membrane filter (Millipore Corporation, Bedford, MA, USA; for POP), previously washed with 0.2 M HCl and rinsed with demineralized water. Filters were subsequently rinsed again with demineralized water and stored at -20°C. Prior to analysis, filters were dried at 60°C for 48 h. POC and PON were analyzed by an element analyzer (NA-2500 Thermo Analyzer, Thermo Fisher Scientific, Whaltham, MA, USA). POP was determined through digestion of the organic material with nitric acid at 200°C and subsequent analysis at 213.6 nm with an inductively coupled plasma-optical emission spectrophotometer (iCap 6000 ICP-OES Analyzer, Thermo Fisher Scientific).