Ultrasensitive and highly selective "turn-on" fluorescent sensor for the detection and measurement of melatonin in juice samples.

Melatonin (MLT), a hormone related to the regulation of brain functions, is directly related to sleep quality and is considered to be a possible adjuvant therapy for patients needing hospitalization for coronavirus disease 2019 pneumonia, and accurate measurement of MLT is crucial. Herein, a new, highly sensitive, and easy operation fluorescent probe was provided based on Zr metal-organic framework encapsulation into the molecularly imprinted polymer (MOF@MIP). By combining unique properties of MIP and fluorescent MOF, selectivity and operation of the applied method were significantly improved. Different characterization methods, such as XRD, FT-IR, and FE-SEM, were used to confirm the synthesis reliability. MOF@MIP was successfully used for the precise identification and ultrasensitive detection for trace amounts of MLT. The detection mechanism for the analytical system is based on the ''turn-on'' fluorescence (FL) signal in 404 nm. The findings proved that it is possible to detect trace amounts of MLT in real samples including grape, cherry, and sour cherry juice. The linear range and the limit of detection (LOD) for trace amounts of MLT were obtained as 1-100 ng/mL and 0.18 ng/mL, respectively.

Glutamine Supplementation Enhances the Effects of a Low FODMAP Diet in Irritable Bowel Syndrome Management.

Background and Aims: Although irritable bowel syndrome is one of the most common gastrointestinal disorders presented to gastroenterologists, therapeutic strategies are not yet well-established. Accordingly, we conducted a randomized, double-blind, placebo-controlled, clinical trial to evaluate the possible superiority of adding glutamine supplement to low fermentable oligo- di- monosaccharides and polyols (FODMAP) diet in patients with irritable bowel syndrome (IBS). Methods: Eligible adults were randomized to receive a low FODMAP diet either with glutamine (15 g/day) or a placebo for 6 weeks. The primary endpoint was a significant reduction in IBS-symptom severity score (IBS-SSS). Secondary endpoints were changes in IBS symptoms, stool frequency, consistency, and quality of life. Results: The study group enrolled 50 patients, among which 22 participants from each group completed the study protocol. The glutamine group had significant changes in total IBS-severity score, dissatisfaction of bowel habit and interference with community function (58% reduction; P < 0.001, 57% reduction; P < 0.001, 51% reduction; P = 0.043, respectively). Improvement in IBS-severity score of more than 45% was observed in 22 of 25 participants (88%) in the glutamine group, while it was only 15 of 25 participants (60%) in the control group (p = 0.015). No serious adverse events were observed. Conclusions: Our findings indicated the superiority of adding glutamine supplementation to a low FODMAP diet in amelioration of IBS symptoms while confirming the beneficial effects of a low FODMAP diet in IBS management.

Use of nanoporous Cu(II) ion imprinted polymer as a new sorbent for preconcentration of Cu(II) in water, biological, and agricultural samples and its determination by electrothermal atomic absorption spectrometry.

A new and selective Cu(ll) ion imprinted polymer was prepared by formation of 1-(2-pyridylazo)-2-naphthol complex for selective extraction and preconcentration of Cu ions. Polymerization was performed with ethylene glycol dimethacrylate as a crosslinking monomer and methacrylic acid as a functional monomer in the presence of 2,2'-azobis(isobutyronitrile) as an initiator via a bulk polymerization method. The Cu(ll) imprinted polymeric particles were characterized by scanning electron microscopy and IR spectrometry. The imprint Cu ion was removed from the polymeric matrix using 2 M HNO3. Optimum pH for maximum sorption was 5-8. Maximum sorbent capacity and the enrichment factor for Cu(ll) were 11.3 mg/g and 100, respectively. The RSD and LOD of the method were evaluated as +/-4.3% and 8.7 ng/L, respectively. The proposed method is simple, highly selective, and sensitive and can be applied to the determination of ultratrace amounts of Cu in water, biological, and agricultural samples.

Determination of nickel in water, food, and biological samples by electrothermal atomic absorption spectrometry after preconcentration on modified carbon nanotubes.

A new and sensitive SPE method using modified carbon nanotubes for extraction and preconcentration, and electrothermal atomic absorption spectrometric determination of nickel (Ni) in real samples at ng/L levels was investigated. First, multiwalled carbon nanotubes were oxidized with concentrated HNO3, then modified with 2-(5-bormo-2-pyridylazo)-5-diethylaminophenol reagent. The adsorption was achieved quantitatively on a modified carbon nanotubes column in a pH range of 6.5 to 8.5; the adsorbed Ni(II) ions were then desorbed by passing 5.0 mL of 1 M HNO3. The effects of analytical parameters, including pH of the solution, eluent type and volume, sample volume, flow rate of the eluent, and matrix ions, were investigated for optimization of the presented procedure. The enrichment factor was 180, and the LOD for Ni was 4.9 ng/L. The method was applied to the determination of Ni in water, food, and biological samples, and reproducible results were obtained.

Application of nanoclay for preconcentration of ultra trace amounts of palladium in environmental samples prior to its determination by ETAAS.

In the present work, a batch preconcentration technique using nanoclay with 5-(4-dimethylaminobenzylidene)rhodanine coupled with electrothermal atomic absorption spectrometry was developed for the separation and determination of trace amounts of palladium. In this method, the sample solution was stirred with nanoclay as an adsorbent. Then, adsorbed palladium was subsequently eluted with HCl in acetone (1.5 mol L−1) and, finally, this eluate was injected to electrothermal atomic absorption spectrometry. Under the optimum conditions, the limit of detection and linear dynamic range were found to be 2.6 and 10.0­133 ng L−1 (in original solution), respectively. Furthermore, the enrichment factor and relative standard deviation of seven replicate determinations were 148 and ±5.1 %, respectively. This suggested method is simple, selective and sensitive and can be applied to the extraction and determination of palladium in water, tea leaves, synthetic sample and certified reference material with satisfactory results.

Alumina coated with oxazolone derivative for extraction of trace amounts of cadmium and copper from water and plant samples.

A solid phase extraction procedure is proposed for simultaneous separation and preconcentration trace amounts of Cu(II) and Cd(II) using alumina coated with N'-{4-[4-{1-[4-(dimethylamino)phenyl]methylidene}-5-(4-H)oxazolone]phenyle}acetamide and determination by flame atomic absorption spectrometry. Using 0.1g of the sorbent, the metal ions were sorbed at pH 7 and recovered with 5.0 mL of 0.5 mol L(-1) HNO(3). It was found that extraction can be performed from the sample volumes of 2000 and 800 mL for Cu and Cd, respectively (preconcentration factors of 400 for Cu and 160 for Cd). Obtained sorption capacities for 1g sorbent were 8 mg Cu and 14 mg Cd. The linearity was maintained in the concentration range of 0.1 ng mL(-1) to 7.0 µg mL(-1) for Cu and 0.13 ng mL(-1) to 2.0 µg mL(-1) for Cd in the original solution. Eight replicate determinations of a mixture containing 1.0 µg mL(-1) each of the elements in the final solution gave relative standard deviation ±1.6 and ±1.3% for Cu and Cd, respectively. The detection limit was calculated as 0.06 and 0.05 ng mL(-1) for Cu and Cd, respectively. The proposed method was successfully applied to the determination trace amounts of Cu and Cd in the water and plant samples.

Polyacrylic acid-modified alumina for solid-phase extraction and preconcentration of trace iron and chromium from plant samples.

A new method is presented for simultaneous preconcentration of trace Fe(III) and Cr(III) by using polyacrylic acid-alumina as a sorbent. The separation/preconcentration conditions of analytes were investigated, including effect of pH, flow rate, elution conditions, sample volume, and interfering ions. At pH 4, the maximum sorption capacities of Fe3+ and Cr3+ were 8.0 and 13.0 mg/g, respectively, by the column method. The linearity was maintained in the concentration range of 0.175-6.0 x 10(3) ng/mL for iron and 0.175-8.0 x 10(3) ng/mL for chromium in the original solution. The RSD values under optimum conditions were +/- 1.73 and +/- 1.28% for 2.0 microg/mL Fe and Cr, respectively. The preconcentration factor was 400 for both of the elements, and detection limits were 0.025 and 0.023 ng/mL for Fe and Cr in the original solutions. The proposed method was successfully applied to the determination of trace amounts of Fe and Cr in plant samples.

Determination of trace amounts of nickel, manganese, cobalt, and zinc in environmental samples after separation and preconcentration by use of polyacrylic acid/alumina sorbent.

Manganese, nickel, cobalt, and zinc are elements that appear together in many real samples. In this work, a simple, rapid, and sensitive method has been used for the simultaneous separation and preconcentration of trace amounts of these elements using water-soluble polyacrylic acid on alumina as a sorbent in a glass column system. A solution containing Mn, Ni, Co, and Zn was passed through the column at pH 7, and desorption was carried with 5.0 mL of 0.03 M nitric acid. Linearity was maintained between 0.25-5.0 x 10(3), 0.04-6.0 x 10(3), 0.10-8.0 x 10(3), and 0.028-1.0 x 10(3) ng/mL for Ni, Mn, Co, and Zn, respectively, in the original solution. Eight replicate determinations of a mixture containing 1.0 microg/mL of each of the elements in the final solution gave relative standard deviations of 1.4, 1.5, 2.4, and 1.2% for Ni, Mn, Co, and Zn, respectively. The sorption capacities for Mn (mg/g sorbent) obtained were 16.0 for Mn, 9.0 for Ni, 12.0 for Co, and 10.0 for Zn. By using 5.0 mL elution solution, preconcentration factors of 400, 500, 700, and 460 could be obtained for Ni, Mn, Zn, and Co, respectively.

Solid-liquid extraction and preconcentration of trace nickel using 2-nitroso-1-naphthol-4-sulfonic acid (Nitroso-S) and TDBA onto benzophenone and determination by atomic absorption spectrometry.

Nickel was quantitatively retained by 2-nitroso-1-naphthol-4-sulfonic acid (Nitroso-S) and tetradecyldimethylbenzylammonium chloride (TDBA Cl) onto benzophenone in the pH range 5.0-6.0 from large volumes of aqueous solutions of various samples. After filtration, each solid mass consisting of a nickel complex and benzophenone was dissolved with 5 ml of dimethylformamide (DMF) and the metal was determined by atomic absorption spectrometry (AAS). About 0.6 microg of nickel could be concentrated from 200 ml of an aqueous sample, where its concentration was as low as 3.0 ng/ml. Eight replicate determinations of 2.5 microg/ml of nickel in the final DMF solution gave a mean absorbance of 0.112 with a relative standard deviation of 1.9%. The sensitivity for 1% absorption was 98 ng/ml. The interference of a number of anions and cations was studied and the developed optimized conditions were utilized for the trace determination of nickel in various alloys and biological samples.