Author
Kenneth Ong

PerkinElmer Life and Analytical Sciences 710 Bridgeport Avenue Shelton, CT 06484 USA

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Na and K analysis in cooking oil make easy with direct flame AAS

In accordance to EN14108 and EN14109, analysis of Na and K in cooking oil can be easily performed with AAS without tedious sample pre-treatment such as ashing or digestion. The oil is simply diluted between 10 to 25 times with a Xylene solution or kerosene. The Na/K content in the sample can be directly determined by a flame AAS at wavelength of 589nm and 766.5

Figure 1. AAnalyst 400

Figure 2. Cooking oil

However, some important precautions should be taken as sodium and potassium are present everywhere in the environment. The Glassware used for the preparation of the solutions shall be washed at least twice with approximate 5mol/l of HCl, rinsed with distilled water then dried in order to avoid sodium contamination. Alternative, isopropyl alcohol which can be obtained in very pure form can be used for final rinsing to speed up the drying process. It is recommended to prepare all determination solutions in polypropylene flasks and to conduct sample operation using polypropylene pipette.

The stock solution of ~5ppm, for the preparation of calibration solutions, should be prepared freshly everyday. Calibration solutions of 0.1ppm to 0.3ppm should be properly capped until they are ready for analysis to avoid evaporation of volatile xylene or kerosene. Do take care of the viscosity and oil content of the standard and sample solutions, while diluting to the calibration range, the sample solution should contain same oil content as the standard.

The common application of Flame AAS is for nutrient or major elements analysis in food staff, Graphite AAS on the other hand can also be employed for trace toxic elements analysis in Food Safety Application. The longitudinal Zeeman-effect background correction which provide double the amount of light throughput by eliminating the need for a polarizer in the optical system, together with the Transversely heating Graphite tube allow the instrument to hand complex digested food matrix. The GFAA has detection limit capability well below the level of concern and provides an economical choice for smaller laboratories or those with a smaller workload. This article at http://las.perkinelmer.com/Content/pdfs/India/Fresh-Vol8_2009.pdf feature the analysis of Baby Food using GFAAS.

Figure 3. AA600