An RA-915+Mercury Analyzer (Ohio Lumex Co., Russia)with a RP-
91C pyrolysis accessory (Lumex, Russia) was used for FPAAS mercury
determination in dry nanodiamond samples. RA-915+ is a portable
multifunctional atomic absorption spectrometer with Zeeman highfrequency
modulation of polarization for background correction [36,
44–46]. RP-91C is intended as an accessory for thermal decomposition
of solid samples at 800 °C under air atmosphere and the transformation
of bound Hg from ionic to atomic species for subsequent determination
with a RA-915+ analyzer. The attested detection limit of this analytical
system is 0.5 μg/kg (0.5 ppb) at 200 mg of sample [47]. The analysis
time is 3 min per a single determination including sample weighing,
combustion, and cooling combustion tube. Typical decomposition time
was about 15–40 s.