An ultra-selective fluorescence method with enhanced sensitivity for the determination of manganese (VII) in food stuffs using carbon quantum dots as nanoprobe

Facile Synthesis of Multifunctional Carbon Dots Derived from Camel Milk for Mn7+ Sensing and Antiamyloid and Anticancer Activities

Carbon dots (CDs) are promising biocompatible fluorescent nanoparticles mainly used in bioimaging, drug delivery, sensing, therapeutics, and various other applications. The utilization of natural sources and green synthetic approaches is resulting in highly biocompatible and nontoxic nanoparticles. Herein, we report an unprecedented facile and green synthesis of highly luminescent carbon dots derived from camel milk (CM) for sensing manganese (Mn7+) ions and for identifying the anticancer potential and antiamyloid activity against α-synuclein amyloids. α-Synuclein amyloid formation due to protein misfolding (genetic and environmental factors) has gained significant attention due to its association with Parkinson's disease and other synucleinopathies. The as-synthesized CM-CDs possess an average hydrodynamic diameter ranging from 3 to 15 nm and also exhibit strong photoluminescence (PL) emission in the blue region. The CM-CDs possess good water dispersibility, stable fluorescence under different physical states, and outstanding photostability. Moreover, the CM-CDs are validated as an efficient sensor for the detection of Mn7+ ions in DI water and in metal ion-polluted tap water. In addition, the CM-CDs have demonstrated a very good quantum yield (QY) of 24.6% and a limit of detection (LOD) of 0.58 μM for Mn7+ ions with no incubation time. Consequently, the exceptional properties of CM-CDs make them highly suitable for a diverse array of biomedical applications.

Jamun Seed-Derived Nitrogen-Doped Carbon Dots: A Novel Microwave-Assisted Synthesis for Ultra-Bright Fluorescence and Mn7+ Detection

For the synthesis of heteroatom-doped carbon nanostructures, biomass is considered as a promising option. Utilizing the microwave-assisted method, we have demonstrated an easy and straightforward one-pot synthesis of nitrogen-doped luminous carbon dots (NCDs) from jamun seed powder and guanidine hydrochloride. Structural and morphological analyses were performed using various analytical techniques. Under ultraviolet light of 315 nm, NCDs emit a bright blue fluorescence, possess a high quantum yield of 26.90%, exhibit strong water dispersion, and demonstrated excellent stability. The average particle size of the NCDs was found to be 7.5±1.2 nm, with a spherical shape. NCDs exhibit high selectivity and sensitivity in fluorescence quenching when exposed to Mn7+ ions. Over a concentration range of 2-30 µM, the fluorescence response (F0/F) shows a linear relationship with Mn7+ concentration, with a detection limit of 0.81 µM. The probe exhibited negligible interference and proved to be effective in accurately quantifying Mn7+ in spiked real-water samples.

Modification and validation of the simultaneous detection of 38 pesticide residues method by ultra-high-performance liquid chromatography/tandem mass spectrometry with QuEChERS extraction in different oil crops and products

RATIONALE

Oil crops and products are important food materials in daily life. Pesticide residues in food could directly and indirectly endanger human health. However, the method for detecting multiple pesticides simultaneously is limited. In this study, an easy and efficient method for the simultaneous determination of 38 pesticides in oil crops and products was established and validated.

METHODS

All samples were treated with a modified QuEChERS procedure followed by ultra-high-performance liquid chromatography/tandem mass spectrometry (UHPLC/MS/MS) analysis. Mass spectrometry was performed in positive and negative ion electrospray ionization mode. The mobile phase consisted of 0.1% formic acid in water and 0.1% formic acid in acetonitrile. The column used was a Poroshell 120 EC-C18 and the flow rate was 0.3 mL/min.

RESULTS

The method was validated so that the calibration curves for all pesticides had good linearity in the concentration range of 10-1000 μg/L with correlation coefficients (R² ) above 0.9945. The recovery rates were between 70.1 and 120.0%, with relative standard deviations (RSDs) (n = 6) ≤20.0%. The limits of quantification (LOQs) ranged from 0.5 to 10 μg/kg, limits of detection (LODs) ranged from 2.0 to 30 μg/kg, and the matrix effect (ME) ranged from -18.77 to 19.33%, respectively.

CONCLUSIONS

The method proved to be accurate, sensitive, and stable. It can be used for rapid screening and confirmation of 38 pesticide residues in oil crops and products which takes 10 min for sample extraction and clean-up with less requirement of solvents. This study provides a technical basis for regulatory analysis and quality supervision of foods.

A Comprehensive Review of Minerals, Trace Elements, and Heavy Metals in Saffron

Saffron is one of the most expensive spices in the world, and its popularity as a tasty food additive is spreading rapidly through many cultures and cuisines. Minerals and heavy metals are minor components found in saffron, which play a key role in the identification of the geographical origin, quality control, and food traceability, while they also affect human health. The chemical elements in saffron are measured using various analytical methods, such as techniques based on spectrometry or spectroscopy, including atomic emission spectrometry, atomic absorption spectrometry, inductively coupled plasma optical emission spectrometry, and inductively coupled plasma mass spectrometry. The present study aimed to review the published articles about heavy metals and minerals in saffron across the world. To date, 64 chemical elements have been found in different types of saffron, which could be divided into three groups of macro-elements, trace elements, and heavy metals (trace elements with a lower gravity/greater than five times that of water and other inorganic sources). Furthermore, the chemical elements in the saffron samples of different countries have a wide range of concentrations. These differences may be affected by geographical condition such as physicochemical properties of the soil, weather and other environmental conditions like saffron cultivation and its genotype.

Development of an ultrasensitive spectrophotometric method for carmine determination based on fluorescent carbon dots

A high-efficiency spectrophotometric method based on nitrogen-doped fluorescent carbon dots (N-FCDs) was developed for the ultrasensitive determination of carmine (CRM) in foodstuffs. The N-FCDs were fabricated via a one-pot hydrothermal method with m-phenylenediamine as the starting material. The detection principle was based on the fluorescence quenching effect of N-FCDs by CRM, where their interaction was due to the inner filter effect (IFE) and static quenching. A good linear relationship was established for CRM detection in a concentration range of 0.1-10.0 μM with a detection limit as low as 11.2 nM. The proposed method achieved satisfactory results for CRM determination in commercial food products with recoveries better than 98.6% and relative standard deviations (RSDs) less than 4.07%. The method established in this study was simple, ultrasensitive and reliable for rapid detecting CRM in a food matrix, which could be potentially used as a useful sensing agent for the analysis of additive food colourants.

Development of a highly sensitive fluorescence method for tartrazine determination in food matrices based on carbon dots

In this work, an ultrasensitive sensing system based on fluorescent carbon dots (CDs) was developed for the tartrazine (Tar) determination. The CDs were prepared via a simple one-pot hydrothermal method with m-phenylenediamine as the only precursor. The physical and chemical properties were in detail characterized by transmission electron microscopy (TEM), MALDI-TOF MS, UV-vis absorption and photoluminescence (PL) spectroscopy, elemental analysis, and Fourier transform infrared spectroscopy (FTIR). Upon exposure to Tar, the fluorescence of CDs was efficiently quenched via the dynamic interaction between CDs and Tar as well as the inner filter effect (IFE). With this information, the CDs were proposed as a fluorescence probe for Tar detection. It was found that CDs had high sensitivity and selectivity for Tar sensing, and the linear relationship was observed in the range of 0.01-25.0 μM with the corresponding detection limit (3σ/k) of 12.4 nM, which is much more sensitive than any of the existed CD-based sensing platform. The investigated sensing system was finally utilized for Tar sensing in various food matrices with a high degree of accuracy. The spiked recoveries were in a range of 96.4-105.2%, and the relative standard deviations (RSDs) were lower than 4.13%. This work highlights the great application prospects of CDs for Tar sensing in a rapid, simple, and sensitive way.

A sensitive spectrofluorimetry method based on S and N dual-doped carbon nanoparticles for ultra-trace detection of ferrocyanide ion in food salt samples

An ultra-sensitive spectrofluorimetry method was developed and validated for the rapid determination of ferrocyanide ions (hexacyanidoferrate(II), FeCN₆ ^4-, FCNs) by using sulphur (S) and nitrogen (N) dual-doped fluorescence carbon nanoparticles (S,N-FCNPs) as nanoprobe. The fluorescence of S,N-FCNPs was strongly reduced due to the dynamic interaction between S,N-FCNPs and FeCNs. The developed method proved to be highly sensitive and selective for FeCNs detection with linearity in three concentration ranges over four orders of magnitude, covering 0.01-200.0 μg/mL. A limit of detection (LOD) of 2.8 ng/mL was obtained. The method was successfully applied for the determination of FeCNs in a series of dietary food salt samples and gave satisfactory results; the spiked recoveries were 97.6‒104.6% with standard uncertainty less than 5.8%. The method proved to be applicable for ultra-trace detection of FeCNs in food salt samples, having advantages in great simplicity, rapid response, low cost, favourable selectivity, and high sensitivity.

Carbon quantum dots derived from the extracellular polymeric substance of anaerobic ammonium oxidation granular sludge for detection of trace Mn(vii) and Cr(vi)

Carbon quantum dots (CQDs) were synthesized via a hydrothermal method, in which extracellular polymeric substance (EPS) from anaerobic ammonium oxidation (anammox) granular sludge was used as a carbon precursor, while citric acid and ethylenediamine were applied as auxiliary carbon source and passivation agent, respectively. The synthesized CQDs, with orderly spherical shape and mean size of 7.15 nm, emitted blue fluorescent light under UV radiation of 365 nm. The CQDs had a high fluorescence yield (40.84%), with good water solubility and excellent spectroscopic properties. In addition, the CQDs exhibited selective, sensitive and distinctive fluorescence quenching behaviors for Cr(vi) and Mn(vii) in a PBS buffer solution (NaH₂PO₄–Na₂HPO₄) of pH 7, with a detection limit of 5.8 nM for Cr(vi) and 2.3 nM for Mn(vii). Owing to the nitrogen components from the EPS of anammox granules, the CQDs were well nitrogen-doped, promoting electron-transfer and leading to reduction between the CQDs and Mn(vii)/Cr(vi). These results indicate that CQD-based chemical sensing is a simple and efficient means for the fluorescence detection of Mn(vii) and Cr(vi).

Fluorescence detection of trace Mn(vii) or Cr(vi) by the CQDs prepared from anaerobic ammonium oxidation granular sludge.