Application of Inorganic Element Ratios to Chemometrics for Determination of the Geographic Origin of Welsh Onions

The composition of concentration ratios of 19 inorganic elements to Mg (hereinafter referred to as
19-element/Mg composition) was applied to chemometric techniques to determine the geographic
origin (Japan or China) of Welsh onions (Allium fistulosum L.). Using a composition of element ratios
has the advantage of simplified sample preparation, and it was possible to determine the geographic
origin of a Welsh onion within 2 days. The classical technique based on 20 element concentrations
was also used along with the new simpler one based on 19 elements/Mg in order to validate the new
technique. Twenty elements, Na, P, K, Ca, Mg, Mn, Fe, Cu, Zn, Sr, Ba, Co, Ni, Rb, Mo, Cd, Cs, La,
Ce, and Tl, in 244 Welsh onion samples were analyzed by flame atomic absorption spectroscopy,
inductively coupled plasma atomic emission spectrometry, and inductively coupled plasma mass
spectrometry. Linear discriminant analysis (LDA) on 20-element concentrations and 19-element/Mg
composition was applied to these analytical data, and soft independent modeling of class analogy
(SIMCA) on 19-element/Mg composition was applied to these analytical data. The results showed
that techniques based on 19-element/Mg composition were effective. LDA, based on 19-element/Mg
composition for classification of samples from Japan and from Shandong, Shanghai, and Fujian in
China, classified 101 samples used for modeling 97% correctly and predicted another 119 samples
excluding 24 nonauthentic samples 93% correctly. In discriminations by 10 times of SIMCA based
on 19-element/Mg composition modeled using 101 samples, 220 samples from known production
areas including samples used for modeling and excluding 24 nonauthentic samples were predicted
92% correctly.
Keywords: Chemometrics; linear discriminant analysis; soft independent modeling of class analogy;
Welsh onions (Allium fistulosum L.); geographic origin; inorganic element