Sains Malaysiana 47(4)(2018): 707-713

http://dx.doi.org/10.17576/jsm-2018-4704-08

An Optical Sensor Based on Immobilized Copper(II) Ions for the Determination of Free Glutamate in Food Samples

(Sensor Optik Berdasarkan Pemegunan Ion Kuprum(II) untuk Penentuan Glutamat Bebas dalam Sampel Makanan)

NOOR ZUHARTINI MD MUSLIM^1*, MUSA AHMAD², LEE YOOK HENG³

& BAHRUDDIN SAAD⁴

¹School of Health Sciences, Health Campus Universiti Sains Malaysia, 16150 Kubang Kerian, Kelantan Darul Naim, Malaysia

²Faculty of Science & Technology Universiti Sains Islam Malaysia, 71800 Bandar Baru Nilai, Negeri Sembilan Darul Khusus, Malaysia

³School of Chemical Sciences and Food Technology Faculty of Science & Technology, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor Darul Ehsan, Malaysia

⁴School of Chemical Sciences Universiti Sains Malaysia 11800 Pulau Pinang, Malaysia

Received: 10 August 2017/Accepted: 25 October 2017

ABSTRACT

An optical fiber chemical sensor for the determination of free glutamate in food samples was fabricated based on the immobilization of 0.1 M copper(II) nitrate trihydrate onto sol-gel glass powder which was then mixed with methyl cellulose to form a pellet. A distinctive colour change from light blue to dark blue was observed in the presence of glutamate in less than 1 min. The colour change was measured by reflectance spectrophotometer at 691 nm. A linear relationship between the reflectance intensity and glutamate concentration was observed in the range of 12.5 to 500 mM with a limit of detection of 10.6 mM. This method is also reproducible with a relative standard deviation of less than 5%, no effect on pH of the glutamate solution and a good recovery of above 80%. The sensor was used for the determination of glutamate in common food items such as soups and flavor enhancers. The results obtained from the fabricated sensor were found to be comparable with HPLC method.

Keywords: Copper(II) nitrate trihydrate; free glutamate; optical fiber chemical sensor; sol-gel glass powder

ABSTRAK

Sensor kimia gentian optik untuk penentuan glutamat bebas dalam sampel makanan telah direka bentuk berdasarkan pemegunan 0.1 M kuprum(II) nitrat trihidrat ke atas serbuk kaca sol-gel yang kemudiannya dicampur dengan metil selulosa untuk dijadikan pelet. Perubahan warna yang ketara daripada biru muda ke biru tua telah diperhatikan dengan kehadiran glutamat kurang daripada satu minit. Perubahan warna ini diukur dengan spektrofotometer pantulan pada 691 nm. Perhubungan linear antara keamatan pantulan dan kepekatan glutamat telah ditunjukkan dalam julat 12.5 ke 500 mM dengan had pengesanan adalah 10.6 mM. Kaedah ini juga boleh dihasilkan semula dengan sisihan piawai relatif kurang daripada 5% serta tidak memberi kesan kepada pH larutan glutamat dan perolehan semula yang bagus iaitu 80% ke atas. Sensor ini telah digunakan untuk menentukan glutamat dalam bahan makanan lazim seperti sup dan penyedap rasa. Keputusan yang diperoleh daripada sensor yang direka bentuk didapati boleh banding dengan keputusan yang diperoleh melalui kaedah HPLC.

Kata kunci: Glutamat bebas; kuprum(II) nitrat trihidrat; sensor kimia gentian optik; serbuk kaca sol-gel

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*Corresponding author; email: zuhartini@usm.my