Method validation and proficiency testing for determination of total arsenic in apple juice by inductively coupled plasma/ mass spectrometry.

A proficiency test (PT) program for determination of total As in apple juice samples was conducted by the Food Emergency Response Network (FERN) laboratories. An analytical method using inductively coupled plasma (ICP)-MS was validated for this project. The LOD and LOQ were determined to be 0.315 and 2.32 ng/g, respectively. A total of eight apple juice samples were sent to 38 FERN laboratories, and results were statistically evaluated according to ISO 13528:2005. The total As concentrations in the PT samples reported by the participating laboratories were very close to those obtained in the homogeneity and stability tests. The reproducibility, repeatability, interlaboratory, and intralaboratory variability results led to 69% of participating laboratories being rated as satisfactory using the widely accepted Izl score <or= 2 criterion. The percentage of laboratories with acceptable z scores (Izl scores <or=2) increased from 61 to 89% with the increase in As concentration in PT samples from 5.05 to 30.72 ng/g. This study demonstrated that the ICP/MS method was adequate for total As determination in fruit juice, and most of the participating laboratories were proficient in their analytical performance.