Dielectric barrier discharge plasma pre-treatment to facilitate the acetylation process of corn starch under heating/cooling cycles.

The objective of the current work was to evaluate the impacts of dielectric barrier discharge plasma and repeated dry-heat treatments on the acetylation process of corn starch. The combined modification resulted in a higher substitution degree of acetate groups on starch chains compared to the acetylation treatment alone. This outcome was linked to the increase in surface area and structural organization level of granules achieved through the application of plasma and heating/cooling cycles, respectively. The successful esterification of starch structure was verified through FTIR (1710 cm-1) and 1H NMR (2 ppm). With the increase in plasma treatment duration up to 20 min, gelatinization enthalpy increased (10.81 J/g) due to the cross-linking reaction. Starch acetate produced through the combined treatment could find the application in the development of low-calorie food formulations due to its high resistant starch (70.5 g/100 g) and low viscosity (43 mPa s).

Solid state cationization reaction of microporous starch with betaine hydrochloride under repeated heating/cooling cycles: Design of a green approach for corn starch modification.

In this research, the cationization process of microporous starch with betaine hydrochloride (BHC) in the presence of H3PO4 (as a catalyst) under heating/cooling cycles was reported for the first time. Granular microporous starch was initially prepared from normal corn starch (NS) through amyloglucosidase treatment. Then, solid state cationization reaction of microporous starch (MS) with betaine hydrochloride (BHC) was performed under repeated dry-heat modification. The cationic microporous starch showed higher substitution degree (0.031) and reaction efficiency (89.1 %) in comparison with cationic starch based on NS (0.021, 60.3 %), which this can be attributed to the increased probability of effective collision between BHC molecules and starch granules after enzymatic treatment. The analysis of cationic starches by FTIR and 13C NMR confirmed the presence of cationic functional groups on starch chains. Further examinations on the modified starches by single and dual treatments were accomplished with respect to morphology, particle size distribution, X-ray powder diffraction (XRD), colour parameters, zeta potential, amylose content, viscosity, solubility, and swelling power. The greenness of the suggested dual treatment (score: 82) in this work was evaluated and compared to a conventional method reported in literature (score: 67) on the preparation of cationic starches.

Ultra-trace determination of cadmium in water and food samples by a thin-film microextraction using a supported liquid membrane combined with smartphone-based colorimetric detection.

A mixture of n-octanol and dithizone was introduced as an effective and novel extraction agent in a thin-film microextraction technique for the pre-concentration of cadmium ions. The extraction agent was immobilized on small pieces of porous polypropylene flat membrane as a supported liquid membrane. The analyte extraction was performed by immersing the modified film in the sample solution, and via a complex formation between the immobilized dithizone on the film and cadmium ions. After the thin-film microextraction process, the colored cadmium-dithizone complex was directly measured by a smartphone colorimetric analysis. Under optimized conditions, the linear dynamic range, the limit of detection, and the limit of quantification were 0.5-300.0, 0.1, and 0.4 µg L-1, respectively. The developed technique was successfully employed to quantify cadmium ions in water and food samples. The high relative recovery values (95.0-103.0%) along with relative standard deviations of less than 2.5% were obtained for the spiked samples.

Solid state malic acid esterification on fungal α-amylase treated corn starch: Design of a green dual treatment.

For the first time, the current work applied fungal α-amylase treated corn starch in granular form to produce solid state malate-esterified starch (MES). The pores and channels created on the granules after the enzymatic modification could provide more possibilities for malic acid to esterify the starch, resulting in the increase of substitution degree (0.084) and reaction efficiency (86.6%) compared to NS. Based on the obtained results, the dual treatment significantly increased solubility, amylose content, and syneresis, but reduced transparency, viscosity, digestibility rate, and swelling power compared to those of NS. The occurrence of esterification onto starch chains was confirmed by FT-IR at 1720 cm-1. Other techniques including SEM, XRD, and DSC were employed to examine changes in the structure of starch granules after applying each treatment. Also, the greenness of the combined modification (score: 77) was proved by using a new methodology named Eco-Scale.

Exploiting agarose gel modified with glucose-fructose syrup as a green sorbent in rotating-disk sorptive extraction technique for the determination of trace malondialdehyde in biological and food samples.

This research reports for the first time on the application of agarose gel impregnated with high fructose corn syrup (AG/HFCS) as a biodegradable and eco-friendly extraction phase in rotating-disk sorptive extraction (RDSE). The gel disk is driven by a rotary rod attached to an electric stirrer during extraction. Malondialdehyde (MDA) was chosen as a model analyte, and was extracted from biological and food samples using the proposed technique after derivatization with 2-thiobarbituric acid (TBA). Due to the hydrophilic nature of the sorbent phase, MDA was concentrated efficiently. After extraction, MDA was quantified directly in the gel disk by solid phase visible spectrophotometry and smartphone-based Red-Green-Blue (RGB) detection. The procedure used no organic solvents, showed clear advantages in terms of simplicity and short analysis time (5 min), and showed potential as a green analytical method. The extraction procedure was studied and optimized to maximize the partition of MDA into the gel. Under optimized conditions, the method provided linear dynamic ranges of 5.5-1000 ng mL-1 for biological samples and 62.5-12500 ng g-1 for food samples with correlation coefficients (R2) higher than 0.9975, relative recoveries between 88.3 and 103.3% along with relative standard deviation (RSD) values less than 3.5%. Accordingly, the proposed method can be employed by analytical laboratories for the rapid determination of MDA in complex matrix of body fluids and food samples under the principles of green chemistry.

An analytical strategy based on the combination of ultrasound assisted flat membrane liquid phase microextraction and a smartphone reader for trace determination of malondialdehyde.

In the present work, a new cleanup process entitled ultrasonic assisted flat membrane liquid phase microextraction (UA-FM-LPME) was introduced. The UA-FM-LPME procedure in two phase format was applied for the extraction-preconcentration of malondialdehyde (MDA) as an analyte model from the biological samples after a derivatization reaction. In the designed extraction setup, the simultaneous use of two flat sheet membranes and the application of ultrasonic radiation provided the efficient mass transfer of MDA into the acceptor phase in a short extraction time (2 min). The collected organic phase was then analyzed through Red-Green-Blue (RGB) image analysis and high-performance liquid chromatography coupled with ultraviolet-visible spectroscopy (HPLC-UV/Vis) as detection methods. The key parameters affecting the extraction process were studied and optimized in detail. The effect of the sugaring out on the partition of MDA into the extraction phase was examined for the first time. Under optimal conditions, linearity was observed in the concentration range of 8-1000 ng mL-1 for HPLC, and 10-1000 ng mL-1 for RGB analysis, with the coefficient of determination (R2) values higher than 0.9973. The introduced method also offered satisfactory relative standard deviations (RSDs) less than 4.0%. In order to examine the reliability of the technique in complicated matrices, three different biological samples (urine, saliva and blood plasma) were analyzed and the acceptable results in terms of relative recoveries (89.7-102.4%) were obtained. The designed setup in combination with RGB analysis will provide a low-cost alternative technique for rapid determination of MDA in clinical diagnosis or biochemical analysis without the need to complex, time consuming and expensive analytical instruments.

Hollow fiber liquid-phase microextraction based on the use of a rotating extraction cell: A green approach for trace determination of rhodamine 6G and methylene blue dyes.

In this work, a novel mode of hollow fiber liquid-phase microextraction (HF-LPME) technique namely rotating extraction cell solvent bar microextraction (REC-SBME) was introduced. The proposed method was applied for the preconcentration of methylene blue (MB) and rhodamine 6G (RG) in some real samples, including soft drink, lipstick, environmental water, and wastewater samples. In the extraction setup, two pieces of hollow fibers were fixed on a mechanical support and immersed in a rotating extraction cell containing the sample solution during the extraction process. The rotation of the extraction cell by using an electric motor led to an enhancement in the mass transfer of the dyes from the sample solution into the organic acceptor phase. In the developed procedure, the UV-Vis spectrophotometry and HPLC-UV/Vis were employed as detection methods for the analysis of the acceptor phase and the obtained results were compared. Optimization of the extraction factors affecting the method, including organic solvent type, sample solution pH, extraction time, rotational rate, the volume of sample and acceptor solutions, salt addition, and temperature was performed in order to obtain the best preconcentration factor. Linear dynamic range obtained by HPLC-UV/Vis and spectrophotometry was observed in the ranges of 2.5-1200 ng mL-1 for RG and 1.6-600 ng mL-1 for MB with R2 more than 0.9971. Also, relative standard deviation (RSD) values (n = 3) less than 3.8% were obtained. The good conformity of the obtained results makes UV-Vis spectrophotometric method an ideal tool for routine analysis of trace dyes in the complex matrices after REC-SBME.

Solvent stir bar microextraction technique with three-hollow fiber configuration for trace determination of nitrite in river water samples.

In this work, trace determination of nitrite in river water samples was studied using solvent stir bar microextraction system with three-hollow fiber configuration (3HF-SSBME) as a preconcentration step prior to UV-Vis spectrophotometry. The obtained results showed that the increase in the number of solvent bars can improve the extraction performance by increasing the contact area between acceptor and sample solutions. The extraction process relies on the well-known oxidation-reduction reaction of nitrite with iodide excess in acidic donor phase to form triiodide, and then its extraction into organic acceptor phase using a cationic surfactant. Various extraction parameters affecting the method were optimized and examined in detail. Detection limit of 1.6 µg L-1 and preconcentration factor of 282 can be attained after an extraction time of 8 min under the optimum conditions of this technique. The proposed method showed a linear response up to 1000 µg L-1 (r2 = 0.996) with relative standard deviation values less than 4.0%. The accuracy of the developed method was assessed using the Griess technique. Finally, the proposed method was successfully employed for quantification of nitrite in river water samples (Ghezelozan, Zanjan, Iran).

A four-hollow fibers geometry of revolving solvent bar microextraction setup for the enrichment of trace ammonia.

In this work, for the first time, a revolving solvent bar microextraction (RSBME) system was introduced as an efficient alternative method to conventional SBME. The setup proposed for RSBME provides a stable and repeatable method to increase the preconcentration factor. In order to provide the maximum extraction capacity of the organic acceptor phase, four-hollow fibers were applied. In this setup, an electrical motor driving rotator was employed as mechanical support for the hollow fibers and also to stir the donor phase during extraction time. The applicability of this technique was assessed by preconcentration-determination of ammonia in the environmental water samples. The effective factors on the RSBME efficiency were examined and optimized. Under the optimized RSBME conditions, ammonia was quantified by microcell UV-Vis spectrophotometry, with extensive linearity ranging from 15 to 1000 µg L-1 (R2 = 0.9972), and RSD values less than 3.5%. A preconcentration of 372-fold with the detection limit of 4.5 µg L-1 was achieved. The green character of this technique was evaluated based on the analytical Eco-Scale tool and compared with a reference method. The setup proposed can be applied for the simultaneous extraction of acidic and basic compounds from biological and environmental samples in the near future.

Solvent-stir bar microextraction system using pure tris-(2-ethylhexyl) phosphate as supported liquid membrane: A new and efficient design for the extraction of malondialdehyde from biological fluids.

A novel and efficient device of solvent stir-bar microextraction (SSBME) system coupled with GC-FID detection was introduced for the pre-concentration and determination of malondialdehyde (MDA) in different biological matrices. In the proposed device, a piece of porous hollow fiber was located on a magnetic rotor by using a stainless steel-wire (as a mechanical support) and the whole device could stir with the magnetic rotor in sample solution cell. The device provided higher pre-concentration factor and better precision in comparison with conventional SBME due to the reproducible, stable and high contact area between the stirred sample and the hollow fiber. Organic solvent type, donor and acceptor phase pH, temperature, electrolyte concentration, agitation speed, extraction time, and sample volume as the effective factors on the SSBME efficiency, were examined and optimized. Pure tris-(2-ethylhexyl) phosphate (TEHP) was examined for the first time as supported liquid membrane (SLM) for the determination of MDA by SSBME method. In contrast to the conventional SLMs of SBME in the literature, the SLM of TEHP was highly stable in contact with biological fluids and provided the highest extraction efficiency. Under optimized extraction conditions, the method provided satisfactory linearity in the range 1-500 ng mL-1, low LODs (0.3-0.7 ng mL-1), good repeatability and reproducibility (RSD% (n = 5) < 4.5) with the pre-concentration factors higher than 130-fold. To verify the accuracy of the proposed method, the traditional spectrophotometric TBA (2-thiobarbituric acid) test was used as a reference method. Finally, the proposed method was successfully applied for the determination and quantification of MDA in biological fluids.

The cooperative effect of reduced graphene oxide and Triton X-114 on the electromembrane microextraction efficiency of Pramipexole as a model analyte in urine samples.

A new design of electromembrane microextraction coupled with high-performance liquid chromatography was developed for the determination of Pramipexole as a model analyte in urine samples. The presence of reduced graphene oxide in the membrane and Triton X-114 in the donor phase augments the extraction efficiency of Pramipexole by the proposed method. Dispersed reduced graphene oxide in the organic solvent was held in the pores of the fiber wall by capillary forces and sonication. It is possible that the immobilized reduced graphene oxide acts as a sorbent, affording an additional pathway for analyte transportation. Besides, the presence of Triton X-114 in the donor phase promotes effective migration of ionic analytes across the membrane. The parameters influencing the extraction procedure, such as type and concentration of surfactant, type of organic solvent, amount of reduced graphene oxide, sonication time, applied voltage, extraction time, ionic strength, pH of the donor and acceptor solutions, and stirring rate were optimized. The linear working ranges of the method for preconcentration- determination of Pramipexole in water and urine samples were found to be 0.13-1000 and 0.47-1000ngmL-1 with corresponding detection limits of 0.04 and 0.14ngmL-1, respectively. The proposed method allows achieving enrichment factors of 301 and 265 for preconcentration of the analyte in water and urine samples, respectively. The method was successfully applied for the determination of Pramipexole in the urine samples.

Electromembrane extraction-preconcentration followed by microvolume UV-Vis spectrophotometric determination of mercury in water and fish samples.

Electromembrane extraction technique combined with microvolume UV-Vis spectrophotometric detection was proposed for the preconcentration-determination of mercury in water and fish samples. The optimized conditions for preconcentration step were: the applied potential 70V, bis(2-ethylhexyl) phosphate as the extractant in 1-octanol 2% v/v, extraction time 10min, stirring rate 700rpm, acceptor and donor solutions pH 3 and 7, respectively. The linear range was found to be 2.3-950.0µgL-1 and 40-9500µgkg-1 in water and fish samples, with corresponding detection limits of 0.7µgL-1 and 12µgkg-1, respectively. The method showed satisfactory repeatability and reproducibility (CV<6%). Methodological validation was performed by using cold vapor atomic absorption spectroscopy. The proposed method provided a rapid, sensitive and accurate method which is applicable for routine analysis of total mercury contents in water and fish samples.

Determination of melamine in dairy products using electromembrane-LPME followed by HPLC.

This study presents the application of electromembrane microextraction technique combined with HPLC-UV detection for fast extraction-preconcentration and determination of melamine in dairy products. It is based on the extraction of charged melamine molecules migrated from 6.5 mL feed solution through a liquid membrane immobilized in the pores of a hollow fiber into 20 µL of the acceptor solution. The best performance was achieved by using 2-nitrophenyloctylether, tris-(2-ethylhexyl) phosphate (10%) and di-(2-ethylhexyl)phosphate (10%) as the extraction solvent; application of a potential of 90 V as the driving force and by adjusting the pH of feed and receiving phases at 5.5 and 1, respectively. The working range was 7-8000 ng mL(-1), with detection limit of 2.0-5.8 ng mL(-1). The enrichment factor was in the range 82-192. Intra- and inter-day relative standard deviations were less than 6.6%. Extraction and relative recoveries for different samples were between 25-59% and 85-95%, respectively.