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Introduction Egg is an important source of high quality natural proteins, lipids, fatty acids, vitamins and essential minerals. Chemical composition of egg is complicated due to presence of many organic compounds that can bind trace elements e.g. protein ovalbumin attracts Se, Hg, Zn, Cu, Mn, glycoprotein ovotransferrin and phosphoproteins bind Fe ions. The elemental content of egg need to be checked for food safety assessment. It should be considered that essential elements may become toxic if consumed in excessive amount or contrary, may lead to element deficiency if consumed insufficiently. Poultry feed composition is different in various parts of the world. It reflects in elemental content of egg yolk and albumen. The contamination of elements in egg can be because of microorganism and by chemical substances which are transferred from environment into food chain. The aim of the present study was to quantitate trace elements in chicken egg in accordance with FSSAI [1,2] Maximum Residual Limits (MRLs) as shown in Table 1. Experimental Chicken egg samples were purchased from local market. The edible part of egg was vortexed to homogenise the content. Table 1: FSSAI MRLs (ppm) for egg *The limit for Se is not available as per FSSAI, so value was taken arbitrarily. Sample Preparation About 500 mg of sample was weighed and transferred into microwave vessels. Samples were kept for pre digestion. After carefully adding 5 mL of suprapure nitric acid, 0.5 mL suprapure hydrogen peroxide and 1 mL ultrapure water. The vessels were then heated in microwave digestor system under controlled temperature program (Table 2). After digestion, samples were cooled to ambient temperature and transferred to a 50 mL volumetric flask and diluted with ultrapure water. Pre-spiked recovery samples were prepared at LOQ & 10 x LOQ levels. Table 2: Microwave digestion program Calibration standard preparation Calibration standards were prepared form 1000 ppm certified reference standards after appropriate dilutions, covering concentration range from 10 to 250 % of the MRL. The LOQ was set to 20 % of the MRLs in accordance with commission regulation (EU) 836/2011 [3] (Table 3). Table 3: LOQs (ppm) for egg in present work Application News NO. SP-010-ADI-066 ICPMS-2030 Trace elemental analysis of chicken egg using Shimadzu Inductively Coupled Plasma-Mass Spectrometer (ICP-MS) Elements FSSAI MRLs Arsenic (As) 1.1 Cadmium (Cd) 1.5 Copper (Cu) 30 Mercury (Hg) 1 Lead (Pb) 0.1 Selenium (Se)* 2.5 Tin (Sn) 250 Zinc (Zn 50 Ramp (min) Temp (C) Hold time (min) 10 120 05 10 180 30 Elements LOQs Arsenic (As) 0.22 Cadmium (Cd) 0.3 Copper (Cu) 6 Mercury (Hg) 0.2 Lead (Pb) 0.02 Selenium (Se) 0.5 Tin (Sn) 50 Zinc (Zn) 10
LC-08-ADI-00X Analytical Conditions A Shimadzu ICPMS-2030 coupled with auto sampler AS-10 (Figure 1) was used for analysis of measuring elements in egg. The detailed instrument configuration and operating parameters are summarized in Table 4. The elements Bi, Ge and Y were used as internal standards. Continuous Calibration Verification (CCV) checks were run in between to check drift of the system throughout the run. The standard of LOQ concertation was run as CCV. The concentrations of linearity standards are shown in Table 5. Table 4: Instrumental parameters Plasma torch Mini torch((P/N:S211-94018)) Radiofrequency 1.2 kW Sampling depth 5 mm Plasma gas flow rate 10 L/min Auxiliary gas flow rate 1.1 L/min Carrier gas flow rate 0.7 L/min Collision gas Helium Collision gas flow rate 6.0 mL/min Chamber Cyclone chamber Chamber temperature 5 °C Figure 1. Shimadzu ICPMS-2030 with Autosampler AS-10 Fig 2. Calibration curves obtained in present study Application News No. SP-10-ADI-066
LC-08-ADI-00X Table 5: Calibration of linearity standards in ppb prepared in present study Elements As Cd Cu Hg Pb Se Sn Zn Calibration Std Level 1 0 0 0 0 0 0 0 0 Calibration Std Level 2 1.1 1.5 30 1 0.1 2.5 25 50 Calibration Std Level 3 2.2 3 60 2 0.2 5 50 100 Calibration Std Level 4 5.5 7.5 150 5 0.5 12.5 125 250 Calibration Std Level 5 11 15 300 10 1 25 250 500 Calibration Std Level 6 22 30 600 20 2 50 500 1000 Calibration Std Level 7 27.5 37.5 750 25 2.5 62.5 625 1250 Table 6: Average % recovery and % RSD at LOQ, 10 x LOQ (n=4 replicates) Results The calibration standards showed good linear response with correlation coefficient (r) ≥ 0.999 for all elements. The content for all analyzed elements was lower than the set LOQ. The % recoveries obtained are given in Table 6. The recoveries at LOQ and 10 x LOQ levels were between 80 to 120 % for all elements. % RSD of result obtained for 4 preparation are less than 8 %, indicating good repeatability. Results of CCVs are shown in Table 7. Accuracy of CCVs was between 90 to 110 %. Elements LOQ % recovery LOQ % RSD 10 x LOQ % recovery 10 x LOQ % RSD As 102.9 2.7 104.6 0.7 Cd 97.5 1.4 103.2 0.7 Cu 89.8 1.6 104.5 1.1 Hg 99.6 4.2 98.3 3.8 Pb 109.5 6.4 100.8 4.1 Se 110.6 4.0 109.4 0.9 Sn 101.2 4.1 104.8 1.9 Zn 88.5 4.7 99.7 0.6 Application News No. SP-10-ADI-066 CCV standard As Cd Hg Pb Cu Se Sn Zn CCV 1 97.3 99.3 90.3 104.5 102.5 96.6 99.2 92.8 CCV 2 96.8 96.7 90.8 98.5 103.5 96.8 101.6 92.0 CCV 3 94.1 95.3 91.5 100.0 103.5 95.8 101.4 92.3 Table 7: Results for % accuracy of the CCVs
LC-08-ADI-00X Copyright © 2013 SHIMADZU ANALYTICAL (INDIA) PVT. LTD. All rights reserved. No part of this document may be reproduced in any form or by any means without permission in writing from SHIMADZU ANALYTICAL (INDIA) PVT. LTD. Shimadzu Analytical (India) Pvt.Ltd. 1 A/B, Rushabh Chambers, Makwana Road, Marol, Andheri (East), Mumbai- 400059, India. Tel: +91 22 29204741 Fax: +91 22 29205679 www.shimadzu.in First Edition: Sep. 2018 Conclusion Present work demonstrates a robust and reliable digestion method for determination of trace elements in egg by ICPMS 2030. The excellent spike recoveries obtained shows efficacy of the digestion method for a complex matrix like egg. The % recovery and % RSD obtained shows the reproducibility of the method. References [1] Food Safety and Standards (Contaminants, Toxins and Residues) Regulations, 2011 [2] Food Safety and Standards (Contaminants, Toxins and Residues) Regulations, 2006 [3] Commission regulation, EU No 836/2011 Application News No. SP-10-ADI-066 For Research Use Only. Not for use in diagnostic procedures.
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