Sample preparation using membrane dialysis for determination of Iodide Ion in milk and egg samples

Abstract

The sample preparation using membrane dialysis for iodide determination in milk and egg samples was developed. Thio-nit method was used for iodide detection. Several dialysis configurations with polysulfone hollow fiber membrane were investigated. When donor solution (iodide solution) or acceptor solution (deionized water) was recirculated through the membrane which was immersed in the other solution, high %dialysis was obtained, however, dialysis time was quite long and filtration effect was found. The similar effects were observed when the donor and acceptor solutions were recirculated countercurrently across the membrane. When the donor solution was fixed inside the membrane while the acceptor was flown outside in non-recirculation system, only 0.2 mL of sample could provide sufficient %dialysis for dialysis time less than 10 min and the filtration effect was not found. Furthermore, it was found that 1 mL/min of acceptor flow rate could provide sufficient %dialysis in short dialysis time. The donor composition was optimized using the mixture of Na[subscript 2]CO [subscript 3] and NaHCO [subscript 3]. It was observed that the %dialysis was significantly increased due to the ionic strength effect on the dialysis mechanism. However, as higher salt concentration, the % dialysis was decreased. Because of the solution may become more viscous, the diffusion of iodide ion would be slower. The linear dynamic range was 0 to 480 µg/L. The limit of detection and the limit of quantitation were 32.9 µg/L and 97.7 µg/L, respectively. The recovery of 89.7% was obtained from skim milk powder standard reference material with 9 %RSD. This method was applied to milk and egg samples. The recovery of spiked milk and egg samples were in the range of 100-115 % with 4-22 %RSD and 100-112% with 15-22 %RSD, respectively.