Publications by authors named "Apichai Phonchai"

5 Publications

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A portable electrochemical sensor for detection of the veterinary drug xylazine in beverage samples.

J Pharm Biomed Anal 2021 May 8;198:113958. Epub 2021 Feb 8.

Center of Excellence for Trace Analysis and Biosensors (TAB-CoE), Prince of Songkla University, Hat Yai, Songkhla, 90112, Thailand; Center of Excellence for Innovation in Chemistry, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla, 90112, Thailand; Division of Health and Applied Sciences, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla, 90112, Thailand. Electronic address:

A portable electrochemical sensor was developed to determine xylazine in spiked beverages by adsorptive stripping voltammetry (AdSV). The sensor was based on a graphene nanoplatelets-modified screen-printed carbon electrode (GNPs/SPCE). The electrochemical behavior of xylazine at the GNPs/SPCE was an adsorption-controlled irreversible oxidation reaction. The loading of graphene nanoplatelets (GNPs) on the modified SPCE, electrolyte pH, and AdSV accumulation potential and time were optimized. Under optimal conditions, the GNPs/SPCE provided high sensitivity, linear ranges of 0.4-6.0 mg L (r = 0.997) and 6.0-80.0 mg L (r = 0.998) with a detection limit of 0.1 mg L and a quantitation limit of 0.4 mg L. Repeatability was good. The accuracy of the proposed sensor was investigated by spiking six beverage samples at 1.0, 5.0, and 10.0 mg L. The recoveries from this method ranged from 80.8 ± 0.2-108.1 ± 0.3 %, indicating the good accuracy of the developed sensor. This portable electrochemical sensor can be used to screen for xylazine in beverage samples as evidence in cases of sexual assault or robbery.
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http://dx.doi.org/10.1016/j.jpba.2021.113958DOI Listing
May 2021

A portable sol-gel urea colorimetric method for the determination of urea in feedstuffs.

Food Chem 2020 Jul 2;319:126545. Epub 2020 Mar 2.

Department of Applied Science, Faculty of Science, Prince of Songkla University, Songkhla 90112, Thailand.

A sol-gel urea colorimetric method was developed for the determination of urea in feedstuffs. The sol-gel platform contained p-dimethylaminobenzaldehyde (p-DMAB) as the reagent entrapped within polymer network. The urea analysis relied on the formation of Schiff base under acidic conditions. The colorimetric product was imaged with a Smartphone. Under optimized conditions, the calibration curve for urea was linear over the concentration range of 2.5-100 and 100-1000 mg L with a good coefficient of determination (r > 0.99). The limit of detection (LOD) and limit of quantification (LOQ) were 0.1 and 0.5 mg L, respectively. The intra-day and inter-day precisions were 0.83-3.01%RSD and 2.20-5.47%RSD, respectively. Accuracy of urea analysis ranged from -1.15 to 2.76%. The proposed method was stable for at least 90 days. The amount of urea in feedstuff sample was determined. The developed method is easy to use with small samples and reagent consumption in field conditions for monitoring the quality of feedstuff.
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http://dx.doi.org/10.1016/j.foodchem.2020.126545DOI Listing
July 2020

Rapid measurement of indole levels in Brassica vegetables using one millilitre binary organic extraction solvent and capillary electrophoresis-UV analysis.

Phytochem Anal 2020 Jul 8;31(4):522-530. Epub 2020 Jan 8.

Department of Chemistry and Centre of Excellence for Innovation in Chemistry and Flow Innovation-Research for Science and Technology Laboratories (FIRST Labs), Faculty of Science, Mahidol University, Rama VI Rd, Bangkok, 10400, Thailand.

Introduction: Brassica vegetables contain high levels of indole compounds which have been found to provide health benefits, especially as cancer-preventive agents. An efficient and rapid method using solvent extraction with capillary electrophoresis (CE) and ultraviolet (UV) detection was developed for the determination of four major indoles from four types of Brassica vegetables.

Materials And Methods: Freeze-dried samples of four Brassica vegetables, i.e. broccoli, cauliflower, Chinese cabbage and cabbage, were selected. Hence, 1 mL of the binary solvent dimethylformamide (DMF)-methanol, 4:1 (v/v), was used for sample extraction. The extracts were diluted with the running buffer and directly analysed using CE with UV detection of four indole compounds.

Results: The binary solvent DMF-methanol, 4:1 (v/v) was selected from studies of the extraction efficiency of standard indoles spiked in ivy gourd (as the negative control sample) and using diphenylamine as the internal standard. Recovery was 80(±10)-120(±3)% for the four indoles: indole-3-carbinol (I3C), indole-3-acetonitrile (I3A), indole-3-acetic acid (IAA), and 3,3'-diindolylmethane (DIM). For direct analysis suitable dilution of the extract with the running buffer was required. The linear range of the quantitation is 0.75-25.0 μg/mL, limit of detection (LOD) of 0.14-0.52 μg/mL and r > 0.998. The amount of indole in the Brassica vegetables are in the order I3C > > IAA, I3A > DIM.

Conclusion: A rapid method for extraction and quantitation of four indoles in four Brassica vegetables using CE with UV detection was developed. It has the potential as an efficient technique for generating data for use in agricultural and nutritional studies.
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http://dx.doi.org/10.1002/pca.2916DOI Listing
July 2020

Development of a solid-phase extraction method with simple MEKC-UV analysis for simultaneous detection of indole metabolites in human urine after administration of indole dietary supplement.

Talanta 2017 Nov 8;174:314-319. Epub 2017 Jun 8.

Department of Chemistry and Center of Excellence for Innovation in Chemistry and Flow Innovation-Research for Science and Technology Laboratories (FIRST Labs), Faculty of Science, Mahidol University, Rama VI Rd., Bangkok 10400, Thailand. Electronic address:

This work presents the development of a solid phase extraction method with simple MEKC-UV analysis for the simultaneous determination of indole-3-carbinol (I3C) and its metabolites (3, 3'-diindolylmethane (DIM), indole-3-carboxaldehyde (I3CAL), indole-3-acetonitrile (I3A)) in human urine after oral administration of an indole dietary supplement. Solid phase extraction (SPE) method was applied for the first time for simultaneous analysis of these indole metabolites. The MEKC separation method was developed in a previous work. Three commercial SPE cartridges, each with different sorbent materials, were investigated: Sep-Pak C18, Oasis HLB and Oasis WCX. The Sep-Pak C18 material provided the highest extraction recovery of 88-113% (n = 9), for the four target indole metabolites (I3C, DIM, I3CAL and I3A). The optimal washing and elution solutions were 40% methanol/water (v/v) and 100% methanol, respectively, and optimal elution volume was 2.0mL. The specificity of the proposed SPE method was evaluated with negative control urine samples (n = 10) from healthy volunteers who had not taken the dietary supplement or vegetables known to contain indole compounds. Linear calibration curves were in the range of 0.2-25μgmL (r > 0.998) using diphenylamine (DPA) as the internal standard. Intra-day and inter-day precisions were 3.5-12.3%RSD and 2.7-14.1%RSD, respectively. Limits of detection and quantification were 0.05-0.10μgmL and 0.10-0.50μgmL, respectively. The four target indole compounds were separated within only 5min by MEKC-UV analysis. Urine from 5 subjects who had taken a dietary supplement containing I3C and DIM were found to contain only the DIM metabolite at concentrations ranging from 0.10 to 0.35µgmL. Accuracy of the proposed method based on the percentage recovery of spiked urine samples were 70-108%, 82-116%, 82-132% and 80-100% for I3C, I3CAL, I3A and DIM, respectively. The Sep-PakC18 cartridge was highly effective in extraction and sample cleanup for the downstream simultaneous detection of urinary indole metabolites by MEKC-UV method.
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http://dx.doi.org/10.1016/j.talanta.2017.06.019DOI Listing
November 2017

Lab-on-a-disc for simultaneous determination of total phenolic content and antioxidant activity of beverage samples.

Lab Chip 2016 08;16(17):3268-75

Department of Biomedical Engineering, School of Life Sciences, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea and Center for Soft and Living Matter, Institute for Basic Science (IBS), Ulsan 44919, Republic of Korea.

In this paper, we present a fully integrated and automated lab-on-a-disc for the rapid determination of the total phenolic content (TPC) and antioxidant activity (AA) of beverage samples. The simultaneous determinations of TPC and AA on a spinning disc were achieved by integrating three independent analytical techniques: the Folin-Ciocalteu method that is used to measure TPC, the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) method and the ferric reducing antioxidant power method that are used to measure AA. The TPC and AA of 8 different beverage samples, including various fruit juices, tea, wine and beer, were analyzed. Unlike conventional labor-intensive processes for measuring TPC and AA, our fully automated platform offers one-step operation and rapid analysis.
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http://dx.doi.org/10.1039/c6lc00646aDOI Listing
August 2016