Formaldehyde Detection using Thin Film Sensor based on Chitosan

Crosslinked with Glutaraldehyde

I. Nainggolan

, P. Faradilla

, T. I. Nasution

, H. Agusnar

Chemistry Department, Faculty of Mathematics and Natural Science, Universitas Sumatera Utara, Medan 20155,

Sumatera Utara, Indonesia

Physics Department, Faculty of Mathematics and Natural Science, Universitas Sumatera Utara, Medan 20155, Sumatera

Utara, Indonesia

Keywords: Chitosan, Electrodeposition, Formaldehyde, Film, Sensor.

Abstract: In this study, chitosan was crosslinked with glutaraldehyde to fabricate a formaldehyde sensor. Chitosan based

sensor was used for formaldehyde detection in various concentration (1 ppm; 1,5 ppm; and 2 ppm). The sensor

fabrication was performed using electrodeposition method to form a film sensor. The cross-linking agent is

glutaraldehyde, the aim of adding glutaraldehyde is to enhance the sensing properties of chitosan sensor

especially the life time of the sensor. The existence of glutaraldehyde which was crosslinked with chitosan

has been proved by FTIR spectra. Formaldehyde was dropped onto chitosan film surface and the response of

the chitosan sensor towards formaldehyde was recorded as output voltage. The average of output voltage

values for three times measurements were within the range of 0,0143 V to 0,0286 V. Increasing concentration

of formaldehyde showed the increasing of output voltage value. The sensors showed good sensitivity and fast

response.

1 INTRODUCTION

In Indonesian traditional markets, the control of

government on utilization of prohibited and

dangerous substance in food, especially formalin, is

still weak. It emerges a fret as well as a worry to the

customer, which may cause harm to human health

(Noordiana, 2011). Although adding formalin to

foods is forbidden as stated in The Regulation of

Indonesian Minister of Health No.

1168 /

Menkes /PER/X/1999, some industries, especially

small/home scale industries still add it in foods and sell

them to traditional markets. The Indonesian Agency for

Drug and Food Control found that many testing samples

of food products of Small-Medium Industries are proven

to be positive containing formalin (Media Industry,

2006). According to WHO standard in 2002, the

maximum formalin content contained in food is 1 mg/l

equivalent to 1 ppm (WHO, 2002). Nowadays, the

common method to detect formalin in food is gas

chromatography-mass spectroscopy (GC-MS) but the

analysis tool is expensive and time consuming. It is

highly desirable to develop a sensitive, cheap and

easy-to-use method for formaldehyde detection.

Chitosan as a natural polymer is attractive

sensitive material with several plus properties.

Recently it has been found that chitosan can be

dramatically modified and blended to be used as an

effective sensitive material. It is of interest because

of the possibility to enhance sensitivity and

selectivity due to modification of chitosan structure,

excellent film-forming ability, high mechanical

strength, adhesive, high heat stability (Yang, 2013).

The high chitosan solubility in acidic media also

makes chitosan easily deposited to form film onto a

substrate (Sun,2011). The advantages of non-porous

film layers offer high permeability, mechanical

strength, and selectivity (Kanti, 2004).

Decreasing the mechanical properties of chitosan

in wet conditions can be reduced by the addition of

crosslinking. Cross-linking is the most effective

method for improving membrane properties.

Commonly used crosslinking agents are

glutaraldehyde, trisodium citrate, sulfuric acid, and

pentasodium tripolyphosphate (Safitri, 2016).

Nainggolan, I., Faradilla, P., Nasution, T. and Agusnar, H.

Formaldehyde Detection using Thin Film Sensor based on Chitosan Crosslinked with Glutaraldehyde.

DOI: 10.5220/0010096610391041

In Proceedings of the International Conference of Science, Technology, Engineering, Environmental and Ramiﬁcation Researches (ICOSTEERR 2018) - Research in Industry 4.0, pages

1039-1041

ISBN: 978-989-758-449-7

1039

Utilization of chitosan as a sensitive sensor

material is rarely performed whereas chitosan has

amine (-NH

2) and hydroxyl (-OH) groups in its

molecular structure which enable chitosan as a

sensitive material. The high chitosan solubility in

acidic media also makes chitosan easily deposited in

the form of film onto a substrate (Sun, 2011). So,

chitosan is a potential sensitive material to be a

sensing material to detect formaldehyde.

2 MATERIALS AND METHOD

2.1 Materials and Instruments

Materials which were used in this experimental work

are chitosan with deacetylation degree 80% (medium

molecular weight), glutaraldehyde, CH3COOH 2%,

H2SO4, HNO3, CoCl2 0,01 M, KSCN 1 M, HCl 2 N

(Merck). Printed circuit board (PCB) was used as a

substrate of sensor. Vacuum oven, hot plate, magnetic

stirrer, centrifuge, ultrasonic were used to fabricate

the sensors. A set of FTIR Shimadzu IR prestige-21

was used to characterize the chitosan film and an

electronic set-up was used to test the sensor.

2.2 Preparation of Chitosan Solution

Chitosan powder was supplied by Sigma–Aldrich

(medium molecular weight), it was dissolved in acetic

acid 2% then stirred using a magnetic bar stirrer for

24 hours at room temperature to prepare the chitosan

solution gel.

2.3 Preparation of Chitosan Film

Sensor

Chitosan film was made by chitosan solution using

electrodeposition method. On this process, printed

circuit board (PCB) was used as a substrate of sensor.

The electrodeposition process of chitosan films

illustrates as in Figure 1. The supplied voltage was

fixed at 2,5 volts and left to dry for 5 minutes at 105

in oven. Chitosan film was cross-linked using

glutaraldehyde 25%. CoCl2 0,01 M was used as a

template, KSCN 1 M and HCl 2 N were used as

template remover during crosslinking process.

Formaldehyde solutions with various concentration

(1 ppm; 1,5 ppm; 2 ppm; 5 ppm; and 10 ppm) were

used to test the sensitivity of the chitosan film sensor.

Formaldehyde solution was dropped onto chitosan

film

sensors. Sensor testing was performed using

amperometric method, amperometric method is a

method for detecting analyte using amperometry and

the output was showed based on the characteristic of

sensor. The response of the chitosan sensor towards

formaldehyde was recorded as output voltage.

Figure 1: Deposition Process of Chitosan Film Sensor

3 RESULTS AND DISCUSSION

Chitosan is positively charged in acidic condition

thus it would assemble onto the PCB surface to form

a chitosan film sensor. Glutaraldehyde as a cross-

linking agent made the sensing properties of chitosan

high especially the shelf life of the sensor. The cross-

linked chitosan sensor gave response (output voltage)

to the formaldehyde in various concentration. The

cross-linked chitosan sensor showed good stability in

measurement, there is no any fluctuation in output

voltage. The measurements were repeated three

times. The output voltage values of chitosan sensor

when detecting formaldehyde for 1; 1,5 and 2 ppm

are reported in Table 1.

Table 1: The output voltage of chitosan sensor when

detecting formaldehyde.

Formaldeh

de Outpu

Concentration

Volta

(ppm)

Average

(V)

0,0143

1,5

0,0213

0,0286

Table 1 shows the output voltage of chitosan sensor

when its surface was dropped by formaldehyde

standard solution. The output voltage values show the

ICOSTEERR 2018 - International Conference of Science, Technology, Engineering, Environmental and Ramiﬁcation Researches

1040

sensitivity of chitosan sensor during detecting various

concentration of formaldehyde. The average of output

voltage values for three times measurements were

within the range of 0,0143 V to 0,0286 V. The highest

output value (0,0286 V) was observed when chitosan

sensor detecting 2 ppm of formaldehyde, while the

lowest value (0,0143 V) was observed during the

sensor was dropped by 1 ppm of formaldehyde. As

shown by the table, increasing concentration of

formaldehyde shows the increasing in output value.

Figure 2: FTIR Spectra of Cross-linked Chitosan and

Chitosan Films

The cross-linked process of chitosan has been

done successfully. FT-IR was used to check the

existence of cross-linking based on functional groups

of chitosan. The spectrum of cross-linked chitosan

shows in Figure 2. The hydroxyl groups (O-H

vibration) are showed by band at 3425 cm

-1

for cross-

linked chitosan film and band at 3410 cm

-1

for

chitosan film. The presence of amine group is

strengthened in 1651 cm

-1

(chitosan cross-linked and

chitosan). From the FTIR spectrum, the cross-linking

has been showed at band 1720 cm

-1

for aldehyde

group.

4 CONCLUSIONS

The experimental results of chitosan sensor showed that

chitosan sensor was capable to detect formaldehyde in

various concentration. The chitosan sensor can

differentiate the various concentration of formaldehyde.

The sensitivity of chitosan sensors has been proven by

the different output voltage values which were showed

by the sensors during tested with different concentration

of formaldehyde. Increasing concentration of

formaldehyde showed the increasing on sensor output

voltage values. The highest sensor

output value

(0,0286 V) was showed during the sensor detecting 2

ppm of formaldehyde, while the lowest value (0,0143

V) was showed during the sensor detecting 1 ppm of

formaldehyde.

ACKNOWLEDGEMENT

This work was financially supported by TALENTA

USU research grant No. 2590/UN5.1.R/PPM/2018

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