Determination of sodium and potassium contents in palm-based polyols using graphite furnace atomic absorption spectrometer

Abstract

In the production of palm-based polyols (PBP), multiple purification steps might introduce sodium (Na) and potassium (K) into the polyols. The Na and K have potential to influence reactivity of polyether polyols with isocyanate in polyurethane (PU) production. The Na and K contents in polyether polyols for PU production are both limited to 10 mg kg−1. This study focuses on method(s) development for determination of Na and K in PBP by graphite furnace atomic absorption spectrometer (GF AAS) using dilution in isopropyl alcohol as a sample preparation method. All measurements were performed without any chemical modifier. In GF AAS analysis, it is essential to establish the optimum temperature program which includes pyrolysis and atomization temperature. At the optimized condition, the developed method was validated according to the validation protocol described by International Conference on Harmonization (ICH) and AOAC International. Several parameters were evaluated include linearity of calibration curve, limit of detection (LOD), limit of quantitation (LOQ), sensitivity, recovery, and precision. The optimization of temperature program for both Na and K determinations deduced the optimum pyrolysis and atomization temperature of 900 and 1600 °C, respectively. The method for Na determination concludes as follows: the analytical curve showed linear correlation with R2 value of 0.9928. The LOD and LOQ were 0.307 and 1.025 µg kg−1, respectively. Recoveries in the range of 97 to 108% were obtained from spiked samples (4–12 µg kg−1). Whereas, the method for K determination deduces as follows: the analytical curve showed linear correlation with R2 value of 0.9985. The LOD and LOQ were 0.249 and 0.829 µg kg−1, respectively. Recoveries in the range of 90–109% were obtained from spiked samples (4–12 µg kg−1). The Na and K contents obtained from the developed GF AAS method are in agreement with inductively coupled plasma optical emission spectrometry (ICP OES) with 95% confidence level. The Na and K contents in PBP samples were within the limit allowed for PU production.