Electronic supplementary material

Measurement and analysis of mineral and heavy metal components in grape cultivars by Inductively Coupled Plasma-Optical Emission Spectrometer (ICP-OES)

Feng-Mei Zhu, Bin Du, Feng-Ying Li, Jian-Cai Zhang and Jun Li

Materials and Methods

Materials

Eight grape varieties including four wine grapes (Cabernet Sauvignon, Cabernet Franc, Merlot, Cabernet Gernischt) and four table grapes (Muscat, Red Globe, Vitis labruscana Kyoho, Milk grape) were obtained by grapeyard located in Changli, Hebei Province, China. General descriptions of the grape varieties are given in SupplementaryTable 1. The grapes were harvested on ripening in the 2010 vintages. Grapes free from visible blemish or disease were selected. Three separate batches of grapes from different sites were used to prepare triplicate samples. For quantitative analysis, 50-70 grape berries, randomly selected from each grape variety, were collected for extraction. All data collected for each grape variety were reported as mean±SD for three replications.

Reagents

Standard stock solutions of elements 50 mg/L of K, Fe, Ca, Na; 200 mg/L of Mg, Cu, Mn; 5 mg/L of Ni, Cd, Cr, Pb, Zn. (Perkin-Elmer Instruments Co.,Ltd. USA)

Working solutions of elementsPrepared by serial dilution of stock solutions with deionized water. The range of concentrations used depended on the elements determined.

Apparatus

All glassware and plasticware were washed with deionized water, soaked in 2% HNO3 overnight, rinsed with deionized water, and air-dried.

ICP-OES determinations were carried out with a Perkin-Elmer Optima 2100DV spectrometer (Perkin-Elmer Instruments Co.,Ltd. USA). Emission lines utilized are reported in SupplementaryTable 2. Argon (purity higher than 99.99%) was employed as plasmogen and carrier gas.

Sample preparation

For the sample preparation, conc. HNO3 and HClO4 was used to digest the samples. The fruit samples were prepared according to the following instructions: 1 g of dried flesh sample with 15 mL conc. HNO3 and 3 mL HClO4 are transferred to a 100 mL conical beaker covered with a ribbed watch glass and heated on an oven for digestion. After cooling to room temperature, the remaining solution was transferred to a 50 mL volumetric flask and diluted to volume with deionized water. The blank solution that was prepared from 15 mL conc. HNO3 and 3 mL HClO4 was used as a control for fruit sample. The solutions were filtered through filter paper into a triangular flask. These solutions are analyzed with the ICP-OES.

Analytical Methods

The ICP-OES instrument was initialized and allowed to achieve thermal equilibrium over 30 min. The operating conditions of the ICP-OES equipment are summarised in Supplementary Table 3.

Statistical analysis

Evaluation and analysis of data were performed by means of the following software packages: SPSS for Windows software version 11.5(SPSS Inc, USA). Results were subjected to ANOVA, and differences between means were located using Tukey’s multiple comparison test. Correlations between various parameters were also investigated. Significance was determined at p＜0.05. All data were reported as the mean±SD of three replications.

SupplementaryTable 1 Eight grape varieties

Sample No. / Cultivar / Colour / Abbreviation used
1 / Cabernet Sauvignon / Dark purple / CS
2 / Cabernet Franc / Dark purple / CF
3 / Merlot / Dark purple / ME
4 / Cabernet Gernischt / Dark purple / CG
5 / Muscat / Red, purple / MU
6 / Red Globe / Red / RG
7 / Vitis labruscana Kyoho / Red, purple / VL
8 / Milk grape / Green / MG

SupplementaryTable 2 Lines used for determination of elements with ICP-OES

Element / ICP-OES λ
(nm)
Ca / 317.933
Cd / 228.802
Cr / 267.716
Cu / 324.752
Fe / 238.204
K / 766.490
Mg / 285.213
Mn / 259.372
Na / 330.237
Ni / 231.604
Pb / 220.353
Zn / 213.857

SupplementaryTable 3 Instrumental conditions employed in ICP-OES for the elemental analysis of samples

Parameter / Value
RF power / 1300W
Gas / Argon
Plasma gas / 15 L min-1
Auxiliary gas / 0.2 L min-1
Nebuliser gas / 0.8 L min-1
Sample aspiration rate / 1.5 mL min-1
View / Axial
Background correction / 2-Point
Number of replicates / 1
Nebuliser / Meinhard

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