Evaluation of Postharvest Washing on Removal of Silver
Nanoparticles (AgNPs) from Spinach Leaves
Zhiyun Zhang
Huiyuan Guo
Thomas Carlisle
Arnab Mukherjee
Amanda Kinchla
Jason
C. White
Baoshan Xing
Lili He
10.1021/acs.jafc.6b02705.s001
https://acs.figshare.com/articles/journal_contribution/Evaluation_of_Postharvest_Washing_on_Removal_of_Silver_Nanoparticles_AgNPs_from_Spinach_Leaves/3810690
There
is increasing use of silver nanoparticles (AgNPs) as pesticides
for fruits and vegetables due to the particles’ unique antimicrobial
and insecticidal properties. However, residual AgNPs in harvested
produce may transfer through the food chain and pose a potential risk
to public health. The objective of this study is to determine whether
postharvest washing can effectively remove AgNPs that had accumulated
on fresh produce. Ten microliters of commercially available 40 nm
citrate coated AgNPs (0.4 mg/L) was dropped to a (1 × 1 cm<sup>2</sup>) spot on spinach leaves, followed by washing with deionized
water (DI water), Tsunami 100 (80 mg/L), or Clorox bleach (200 mg/L).
Then, the AgNP removal efficiency of the three treatments was evaluated
by surface-enhanced Raman spectroscopy (SERS), scanning electron microscopy
(SEM)–energy dispersive spectrometry (EDS), and inductively
coupled plasma mass spectrometry (ICP-MS). ICP-MS results showed that
deionized water removed statistically insignificant amounts of total
Ag (5%), whereas Tsunami 100 and Clorox bleach yielded 21 and 10%
decreases in total Ag, respectively (<i>P</i> < 0.05).
The increased removal efficiency resulted from AgNP dissolution and
Ag<sup>+</sup> release upon contact with the oxidizing agents in Tsunami
100 (peroxyacetic acid, hydrogen peroxide) and Clorox bleach (sodium
hypochlorite). According to the SERS results, the deionized water
and Tsunami 100 treatments removed nonsignificant amounts of AgNPs.
Clorox bleach decreased Ag NPs by >90% (<i>P</i> <
0.05);
however, SEM-EDS images revealed the formation of large silver chloride
(AgCl) crystals (162 ± 51 nm) on the leaf, which explained the
low total Ag removal from ICP-MS. This study indicates current factory
washing methods for fresh produce may not be effective in reducing
AgNPs (by water and Tsunami 100) and total Ag (by all three means).
This highlights the necessity to develop an efficient washing method
for NP removal from food surfaces in the future.
2016-08-22 00:00:00
Tsunami 100
SERS
surface-enhanced Raman spectroscopy
40 nm citrate
plasma mass spectrometry
AgNP removal efficiency
SEM
EDS
Tsunami 100 treatments
Clorox bleach
DI
SEM-EDS
deionized water
ICP-MS