Application of Solid Sampling Device for Direct Determination of Chromium and Nickel in Lubricating Oils by Graphite Furnace Atomic Absorption Spectrometry

Abstract

One method using a solid sampling device for the direct determination of Cr and Ni in fresh and used lubricating oils by graphite furnace atomic absorption spectrometry are proposed. The high organic content in the samples was minimized using a digestion step at 400°C in combination with an oxidant mixture 1.0% (v v⁻¹) HNO₃ + 15% (v v⁻¹) H₂O₂ + 0.1% (m v⁻¹) Triton X-100 for the in situ digestion. The 3-field mode Zeeman-effect allowed the spectrometer calibration up to 5 ng of Cr and Ni. The quantification limits were 0.86 µg g⁻¹ for Cr and 0.82 µg g⁻¹ for Ni, respectively. The analysis of reference materials showed no statistically significant difference between the recommended values and those obtained by the proposed methods.

Keywords:

• Atomic absorption
• chromium
• direct oil sampling
• nickel

This research was supported by FAPESP and CNPq.

Notes

^a Cr.

^b Ni.

SD = Standard Deviation (n = 5).

^a NIST 1643c (Ni = 17.54 ± 0.21 µg g⁻¹).

^b JM-21 (Ni = 100 µg g⁻¹ and Cr = 100 µg g⁻¹).