Chn elemental analyzer

Before the grazing experiment started, samples for analyses of cellular C, N, and P of differently grown T. weissflogii were taken from the respective culture bottles by filtering 15 to 25 mL cultures onto pre-combusted (550 °C, 4 to 5 h) GF/C glass-fiber filters. Samples for determining total elemental composition (C, N and P) and intracellular nutrients (NH₄⁺ and PO₄³⁻) of Noctiluca were collected at the beginning and end of the feeding experiment, and also after 6 h starvation. Usually more than 1200 Noctiluca cells were filtered on pre-combusted 25 µm GF/C filters for cellular C, N and P analyses. A similar amount of Noctiluca cells were filtered onto a 20-μm PC membrane and the filters were immediately submerged into 10 mL MilliQ, sonicated (50/60 hz, 20 min), and then filtered through a 0.2 µm disk filter. The filtrate was used to determine the amount of dissolved inorganic NH₄⁺ and PO₄³⁻ in N. scintllans. Subsamples for measuring these elements were in triplicate.
Cellular C and N were analyzed with a CHN elemental analyzer (Perkin-Elmer) and cellular P was analyzed as orthophosphate after acidic oxidative hydrolysis with 1% HCl⁶⁸ . Analyses of NH₄⁺ and PO₄³⁻ were conducted manually according to Strickland and Parsons (1972)⁶⁹ , and the detection limit was 0.5 µmol L⁻¹ for PO₄³⁻ and 0.5 µmol L⁻¹ for NH₄⁺.

Starting compounds and reagents were obtained from Aldrich, TCI, and Alfa Aesar. The already published compounds 1A, 1B, 2B, 2O, and 2R were prepared as described^{[5 (link),6 (link),9 ,14 ]}. For compound analysis, the following instruments were used: Gallenkamp for melting points (uncorrected); Perkin-Elmer Spectrum One FT-IR spectrophotometer (ATR) for IR spectra; BRUKER Avance 300 spectrometer for nuclear magnetic resonance spectra; chemical shifts were expressed as ppm (parts per million, δ) downfield from TMS (tetramethylsilane) as the internal standard; Varian MAT 311A (EI) and UPLC/Orbitrap (ESI-HRMS) for mass spectra; Perkin-Elmer 2400 CHN elemental analyzer for elemental analyses (microanalyses), and compounds were > 95% pure as to elemental analysis.