Geographical origin discriminatory analysis of onions: Chemometrics methods applied to ICP-OES and ICP-MS analysis.

Geographical origin is an important determinant of agricultural product quality and safety. Herein, inductively coupled plasma (ICP) analysis was applied to determine the inorganic elemental content of onions and identify their geographical origin (Korean or Chinese). Chemometric, including principal component analysis (PCA), partial least squares discriminant analysis (PLS-DA), and orthogonal partial least square discriminant analysis (OPLS-DA) were applied to the ICP results. OPLS-DA distinguished each group, and 17 elements with variable importance in projection (VIP) values of ≥ 1 were selected. The receiver operating characteristic (ROC) curve had an area under the curve (AUC) of 1, indicating excellent discriminatory power. Differences in elemental content between groups were visually observed in a heatmap, and the country of origin was determined with 100% accuracy using canonical discriminant analysis (CDA). This method accurately distinguishes between Korean and Chinese onions and is expected to be beneficial for identifying agricultural products.

The effect of different mechanical retention forms on shear bond strength of rebonding of ceramic brackets.

The objective of this study is to compare the shear bond strength (SBS) and the morphological characteristics and chemical compositions of the base surface of newly bonded and rebonded ceramic brackets with different mechanical retention bases. Sixty extracted human premolars were divided into the newly bonded and rebonded groups. Ceramic brackets with patterned, laser-etched, and particle-coated patterned bases were randomly bonded to the tooth samples in each group (n=10 per base type). The rebonded brackets exhibited significantly lower SBS than the newly bonded brackets (p<0.05). The main chemical composition of the brackets in both groups was aluminum on the energy-dispersive X-ray spectroscopy. Scanning electron microscopy imaging showed the presence of regular-shaped undercuts or irregular micro-undercuts on the bracket bases which mostly remained intact even after debonding and sandblasting, while coated particles disappeared. The rebonded ceramic brackets with mechanical retention bases exhibited clinically acceptable bond strength regardless of retentive forms.