Determination of Ascorbic Acid Level in Orange Juice using an

Open-source Poteniostat & Screen Printed Electrodes

Ahmad M. Ali, Iman Morsi and Maha Sharkas

Arab Academy for Science & Technology, Department of Electronics & Communication Engineering,

Abu Qear, Alexandria, Egypt

Keywords: Ascorbic Acid, Poteniostat, Cyclic Voltammetry, Orange Juice.

Abstract: In this research we describe the use of cyclic voltammetry concept in order to determine the level of

Ascorbic Acid in orange juice. The proposed method consists of an open-source poteniostat and screen

printed electrodes. The Current result from the chemical reaction is proportional to the concentration of the

Ascorbic Acid. This method was applied to different commercial samples of orange juice and the results

were used to determine which one has the most preservation of Ascorbic Acid.

1 INTRODUCTION

Ascorbic Acid (Vitamin C) is a water-soluble

vitamin that is highly needed to the human body.

The human body needs Ascorbic Acid (AA) to

produce collagen to make connective tissue. (AA) is

also important the body to absorb iron, heal wounds,

build red blood cells and to fight infections. Since

orange is a great source of (AA) our study is

conducted on different samples of orange juice.

There are several factors that affect the amount

of (AA) in orange juice such as heat, light, exposure

to oxygen and how the juice is made during the

manufacturing process. In this research we focused

the study on the effect of storage temperatures on,

both, fresh and packed orange juice.(Royston and

Angela, 2003).

According to the present life style, people prefer

depending on the packed juices as they are versatile,

accessible and just ready to drink. Consequently,

these products must be periodically checked to

ensure that they contain the right amount of each

nutritional element needed by the human body.

Considerately, the proposed method in this

research is to determine the level of (AA) in orange

juice which reflects the quality of the juice. By

exposing a variety of orange juice samples to

different storage temperatures and checking the

preservation of (AA).

There are some classical techniques for the

determination and assessment of (AA) such as:

titration with an oxidant solution, Chromatographic

methods and Fluorimetric methods. (A.M. Pisoschi

et al., 2008)

The need for another method arises from the

complexity of the previous methods, the expensive

components used and the use of large equipment. On

the other hand, the proposed method consists of a

hand-held poteniostat in the size of cell phone,

screen printed electrodes and a laptop to save the

readings. Fig.1

Figure 1: The poteniostat used in the research and the

screen printed electrodes.

2 BACKGROUND

Several researches have studied the determination of

ascorbic acid in orange juice or in other fruits. Each

study and research utilizes different equipment to

perform the cyclic voltammetry technique.

Fundamentally, Cyclic Voltammetry (CV) is a

Ali, A., Morsi, I. and Sharkas, M.

Determination of Ascorbic Acid Level in Orange Juice using an Open-source Poteniostat & Screen Printed Electrodes.

DOI: 10.5220/0005793700580063

In Proceedings of the 5th International Confererence on Sensor Networks (SENSORNETS 2016), pages 58-63

ISBN: 978-989-758-169-4

technique to study the behavior of electrochemical

reactions. In the CV, information about the samples

undergoing the test is obtained by measuring the

output anodic current as the input voltage varied (J.

Randles and Trans.Far, 1948).

To preform cyclic voltammetry on a certain

chemical element three electrodes are needed

(working, reference and counter) electrodes, a

poteniostat to vary the potential of the working

electrode and a recording device to measure the

output current.

It is worth mentioning that a research to

determine (AA) level in commercial fruit juices was

done using a potentiostat-galvanostat KSP,

laboratory made by SlawomirKalinowski and Pt disc

electrode as a working electrode, saturated calomel

electrode as the reference electrode and the counter

electrode was Pt strip. This setup proved its accuracy

in the determination and recovery of (AA) level in

fruit juices (Pisoschi et al., 2008).

The complication facing this method is that the

test must be done in a chemistry lab, as the

equipment used is static.

Another research was done on the determination

of (AA) level in orange juice using a poteniostat and

a lead pencil electrode. This method proved a

satisfactory determination of (AA) but with a

minimum concentration of 0.0326 mg/mL to

produce a linear determination curve (D. King et al.,

2010).

3 EXPERIMENTAL WORK

3.1 Samples

Three samples were taken from a freshly squeezed

orange juice and stored at 25 ºC, 18 ºC and 12 ºC for

the first experiment.

For the second experiment two samples from

commercial orange juice and one sample from a

freshly squeezed juice were stored at 18 ºC.

KCl solution with a concentration of 0.1 mole/L

was added to all samples as the KCL ions chemically

interact with (AA) ions and enhance the electric

conductivity of the (AA) molecules so that the anodic

current can be measured be the poteniostat.

3.2 Poteniostat and Screen Printed

Electrodes

3.2.1 Poteniostat

Poteniostats are amplifiers used to control the

voltage between working and reference electrodes.

A simple design of poteniostat is shown in Fig.2

(A.V. Gopinath and D.Russel, 2005).

Figure 2: Circuit Diagram of a simple poteniostat.

Several models and designs of poteniostats are

available in the market but due to their

uneconomical cost (range of thousands dollars) and

their huge equipment that is required to be fixed in a

certain place as they are not portable (A.V. Gopinath

and D.Russel, 2005).

The poteniostat used in this research is an open-

source device designed by a team in the

biochemistry department, University of California

Santa Barbra (Rowe AA et al., 2011).

The total cost of the used poteniostat is in the

range of (100$) which is inexpensive compared to

any model of a commercially available poteniostat.

Moreover, the poteniostat used is considered a

hand held device with a USB power supply. It can

be used anywhere due to its portability.

3.2.2 Screen Printed Electrodes

The elimination of bulky materials and instruments

is a major concern in the electrochemistry. The

printed electrodes offer high accuracy, low cost and

more portability.

A major advantage in using Screen Printed

Electrodes (SPE) is that it needs small sample

volume (~ µL) when compared to the traditional

solid electrodes (W. Wonsawat, 2014).

The SPE used in this research is manufactured by

Bio-Logic Science Instruments.

SPE consists of a Graphite working and counter

electrodes, and Ag/AgCl reference electrode with an

alumina substrate. Additionally, the SPE used allows

a low sample volume (25 µL-100 µL) which is a

great advantage in the on-site detection of the

sample under test.

Determination of Ascorbic Acid Level in Orange Juice using an Open-source Poteniostat & Screen Printed Electrodes

4 PROCEDURES

Two experiments were done to determine the level

of (AA) in orange juice. Both were done using the

cyclic voltammetry with the following parameters:

start voltage 200 mV, end voltage 900 mV, slope 50

mV/S, sample rate 5 mV/sample and number of

cycles equal to 1. The current has been evaluated at

550 mV because (AA) is highly chemically active at

this voltage so best current reading is taken at 550

mV (Rowe AA et al., 2011).

Both experiments were run for 7 days, with a

daily reading for each sample.

The SPE used was mechanically cleaned with

distilled water after each reading, also a potential is

applied on the SPE (-200 mV to 200 mV) after each

reading to ensure there is no interaction between the

sample under test and the electrode material (W.

Wonsawat,

2014).

For each reading 10 µL of KCl was added to 20

µL of orange juice sample and the mixture was

tested by the SPE and the poteniostat and the result

of each reading is stored in the PC.

4.1 Experiment 1

In the first experiment three samples of freshly

squeezed orange juice were taken and stored at 25

ºC, 18 ºC and 12 ºC, in order to study the effect of

storage temperature on fresh orange juice. Fig.3

shows the cyclic voltammetry of (AA) at different

storing temperatures.

Figure 3a: Cyclic Voltammetry output of Fresh orange

juice stored at 25 ºC.

Figure 3b: Cyclic Voltammetry output of Fresh orange

juice stored at 18 ºC.

Figure 3c: Cyclic Voltammetry output of Fresh orange

juice stored at 12 ºC.

4.2 Experiment 2

In the second experiment three samples were used,

two of which were from commercial orange juice ,

one of them was a Natural Identical product and the

other was a Nectar product while the third sample

was a freshly squeezed orange juice, in order to study

which type will have the ability to preserve (AA) for

more time keeping the storage temperature (18 ºC.)

stable. Fig.4 shows the cyclic voltammetry for the

samples.

SENSORNETS 2016 - 5th International Conference on Sensor Networks

Figure 4.a: Cyclic Voltammetry output of Natural Identical

orange juice stored at 18 ºC.

Figure 4.b: Cyclic Voltammetry output of Nectar orange

juice stored at 18 ºC.

5 RESULTS AND DISCUSSION

According to Randles-Sevcik equation:

= 2.69.10

3/2

1/2

(1)

Where c is the concentration, v is the voltage scan

rate, A is the electrode surface, D is the diffusion

coefficient, n is the number of electrons transferred

during the process and I

is the anodic current. (A.M.

Pisoschi et al., 2008)

It is obvious that the, concentration is directly

proportional to the anodic current. Accordingly, the

anodic current can be used as a mirror to the

concentration for the study of the (AA) behavior at

different storage temperatures.

5.1 Experiment 1 Results

Starting with the cyclic voltammetry curves, we can

deduce that for a freshly squeezed orange juice, the

lower the storage temprature, the more slower losing

the (AA).

The anodic current values at 550 mV were taken

to plot the relation between the anodic current and

measurments time because at 550 mV the ascorbic

acid ions are dominant over other ions in the orange

juice as shown in Fig5.

By performing a fitting curve to deduce the

equation that shows an approximate form of the

production time of the juice and hence control

techniques can be applied to accomplish different

qualities depending on the level of (AA). This

relationship is given by the following equations.

Figure 5.a: The anodic current at 550 mV at daily basis for

a fresh orange juice at 25 ºC.

y=-30.5357x+ 984.2857 (2)

Figure 5.b: The anodic current at 550 mV at daily basis for

a fresh orange juice at 18 ºC.

Determination of Ascorbic Acid Level in Orange Juice using an Open-source Poteniostat & Screen Printed Electrodes

y=-28.0357x+993.8571 (3)

Figure 5.c: The anodic current at 550 mV at daily basis for

a fresh orange juice at 12 ºC.

y=-22.0357x+988.1429

(4)

Equations (2, 3, 4) can be adopted to determine how

long has the juice been produced on top of checking

the expiry date that gives an indication for the

suitable use date.

5.2 Experiment 2 Results

Arising from the cyclic voltammetry curves of the

three samples we can deduce that at the same storage

temperature, the freshly squeezed orange can

preserve (AA) for more time than the Natural

Identical and the Nectar. Fig.6 shows the degradation

rate of (AA) of the three juice samples at the same

temperature which is 18 ºC.

Figure 6a: The anodic current at 550 mV at daily basis for

a Natural Identical orange juice at 18 ºC.

y=-29.7500x+985.5714 (5)

Figure 6.b: The anodic current at 550 mV at daily basis for

a Nectar orange juice at 18 ºC.

y=-30.2143x+993.0000 (6)

We can also use equations (5, 6) to determine how

long has the juice been produced and check its

expiry date. Ergo, it can give an indication for the

best use date.

6 CONCLUSIONS

In this research we show how to employ the cyclic

voltammetry concept to determine the (AA) level in

orange juice. In this work we used an open-source

poteniostat which was chosen based upon its

inexpensiveness, portability and reliability for (AA)

measurements. Additionally, we used a low cost

screen printed electrodes for the complete process.

The results show that the freshly squeezed orange

juice at the lowest possible storage temperature can

preserve (AA) more than any type of orange juice at

the same temperature.

Wherefore, the deduced relation between the

anodic current and the time can be used to determine

the quality of the juice and an approximation to the

production and expiry dates.

REFERENCES

Royston, Angela (2003). Vitamins and Minerals for a

Healthy Body. Chicago, Illinois:Heinemann Library.

A.M. Pisoschi,A.F. Danet and S. Kalinowski “Ascorbic

Acid Determination in Commercial Fruit

JuiceSamples by Cyclic Voltammetry”Journal of

Automated Methods and Management in Chemistry,

vol.2008, no. 937651.

J. Randles, Trans. Far. Soc., 44 (1948) 327.

SENSORNETS 2016 - 5th International Conference on Sensor Networks

D. King, J. Friend and J. Karuki “Measuring Vitamin C

Content of CommercialOrange Juice Using a Pencil

Lead Electrode” Journal of Chemical Education,

vol.87 no.5, pp 507-508, May 2010.

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Rowe AA, Bonham AJ, White RJ, Zimmer MP, Yadgar

RJ, Hobza TM, et al. (2011) CheapStat: An Open-

Source, “Do-It-Yourself” Potentiostat for Analytical

and Educational Applications. PLoS ONE 6(9):

e23783. doi:10.1371/journal.pone.0023783.

W. Wonsawat “Determination of Vitamin C (Ascorbic

Acid) in Orange Juices Product”, International

Journal of Biological, Food, Veterinary and

Agricultural Engineering, vol.8, no.6, 2014.

Determination of Ascorbic Acid Level in Orange Juice using an Open-source Poteniostat & Screen Printed Electrodes