Nitrites pretreatment procedures and the analytical responses obtained are

Nitrites are well known additives used in food industry as
preservatives. Their ability to increase the shelf life and quality of food
makes it an important ingredient in storage process 1. Nitrites are anti-oxidants which helps in inhibiting the
growth of Clostridium Botulinum
spores in frozen meat and its products 2,3. Major concern on nitrites lies in
the formation of N-nitrosamines, which are potential carcinogens and causes detrimental
effects .  Nitrites can exert acute toxic
effects in humans mainly in infants causing methemoglobinemia 4-7. Nitrites
are vasodilators causing decrease of blood pressure and also the ingested
nitrite causes gastrointestinal illness. Hence, these nitrites exert toxicity and
there is a requisite to keep a check on the presence of nitrites in food and
other edible products 8,9.

Several techniques like chromatography, spectrophotometry, spectrofluorimetry
and chemiluminescence have been reported in the quantification of nitrite at trace
level concentration 10,11. Though these methods are widely used in nitrite
quantification, they require prolonged sampling procedures, use of carcinogenic
or toxic dyes/reagents and require skilled personnel to operate some of these
instruments. In recent years, electrochemical techniques have been widely
explored by the chemists to find suitable sensing platforms in overcoming the limitations
of the above-mentioned techniques. The electrochemical sensing strategies can
be designed selectively to suit the nature of analyte as well as its
complexicity. These electrochemical sensors are easy to fabricate which provide
very good sensitivity and selectivity to the target analyte. They are less
expensive and can be used in the wide potential window 12.

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In recent years, chemically modified electrodes (CMEs) have
been extensively used in the quantitative analysis and sensor technology. The use
of these electrodes in electroanalysis has gained a significant focus very
recently in the form of use and throw type disposable sensors.  These CMEs are target specific, simple and
sensitive and can be used in various forms like carbon paste electrodes, modified
glassy carbon electrode with carbon nanotubes or a wide variety of nanocomposite
materials. Several such modifications have been recently reported in the development
of nitrite sensors 13-15.

These conventional solid electrodes are expensive and
require frequent time-consuming electrode pretreatment procedures and the
analytical responses obtained are less reproducible. The use of screen-printed
electrodes (SPEs) in electroanalysis is pronounced recently and gained a
significant attention by the electrochemists due to their target analyte
specificity, configuration and easy adaptation. SPEs are mass produced solid
microelectrode strips which are inexpensive, easy to carry and hand held
sensors. These eco-friendly small electrode miniatures include advantages like
on-site determination of target species, low cost, portability, high reproducibility
and low sample volume in the quantification of target analyte. Moreover, the
working electrode surface of the SPEs can be modified using wide range of
modifier molecules 16-19.

Chitosan(CS) is ? -1,4 glucosamine and a conducting
biodegradable polymer. It is known to show a good electrochemical activity for the
detection of nitrite ions 20-21. In order to enhance the sensitivity with
reduced ohmic drop, several metal nanoparticles and have been incorporated into
the CS matrix and used as a composite material in nitrite measurement 22-23. These modifications enhance the conductivity of
matrix and  increase the electron
transfer activity on the electrode surface. Metal nanoparticles such as Au, Fe,
Cu, Co, Zn have been used as an electrocatalysts in the electrode fabrication
technology in the measurement of nitrite due to their redox activity and high
electrocatalytic nature 24-28. Ag metal nanoparticles (AgNPs) have been
explored as a potent material for nitrite ion sensing due to their high electrocatalytic
activity and non-toxicity 29-31.

There are no reports available on the use of silver metal nanoparticles
incorporated chitosan matrix in the quantification of nitrite till now. This is
the first report which describes about the use of silver metal
nanoparticles-chitosan(AgNP/CS) composite in the measurement of nitrite at
trace level. This composite has been embedded on the surface of graphite
screen-printed electrodes and used as a disposable sensor strips in the nitrite
quantification at trace level concentration.