Recent analytical methodologies and analytical trends for riboflavin (vitamin B2) analysis in food, biological and pharmaceutical samples

Simple fabrication of electrochemical sensor based on integration of dual signal amplification by the supporting electrode and modified nanochannel array for direct and sensitive detection of vitamin B2

Development of simple and reliable sensor for detecting vitamin content is of great significance for guiding human nutrition metabolism, overseeing the quality of food or drugs, and advancing the treatment of related diseases. In this work, a simple electrochemical sensor was conveniently fabricated by modification a carbon electrode with vertically-ordered mesoporous silica film (VMSF), enabling highly sensitive electrochemical detection of vitamin B2 (VB2) based on the dual enrichment of the analyte by the supporting electrode and nanochannels. The widely used glassy carbon electrode (GCE), was preactivated using simple electrochemical polarization, The resulting preactivated GCE (p-GCE) exhibited improved potential resolution ability and enhanced peak current of VB2. Stable modification of VMSF on p-GCE (VMSF/p-GCE) was achieved without introducing another binding layer. The dual enrichment effect of the supporting p-GCE and nanochannels facilitated sensitive detection of VB2, with a linear concentration ranged from 20 nM to 7 μM and from 7 μM to 20 μM. The limit of detection (LOD), determined based on a signal-to-noise ratio of three (S/N = 3), was found to be 11 nM. The modification of ultra-small nanochannels of VMSF endowed VMSF/p-GCE with excellent anti-interference and anti-fouling performance, along with high stability. The constructed sensor demonstrated the capability to achieve direct electrochemical detection of VB2 in turbid samples including milk and leachate of compound vitamin B tablet without the need for complex sample pretreatment. The fabricated electrochemical can be easily regenerated and has high reusability. The advantages of simple preparation, high detection performance, and good regeneration endow the constructed electrochemical sensor with great potential for direct detection of small molecule in complex samples.

Novel dual-recognition electrochemical biosensor for the sensitive detection of AFM1 in milk

Aflatoxin M1 (AFM1) is a highly carcinogenic and toxic compound that is commonly found in dairy foods such as milk. We developed an electrochemical MIP (molecularly imprinted polymer) and aptamer (Apt) based aptasensor (Apt-Au@PEIM/AFM1/MIP-Apt/AuNPs)/GCE) with dual-recognition signal amplification to detect AFM1 in milk. The MIP-Apt/AuNP/GCE sensor was prepared by synthesizing an MIP film through the electropolymerization of resorcinol on gold nanoparticles-modified electrodes. The dropwise addition of our cApt-Au@PEIM signal amplification probe could enhance the current signal response and improve the sensitivity of the sensor to detect AFM1. The AFM1 present in milk could prevent the probe from binding to the sensor, thereby drastically reducing the current signal. Under optimal experimental conditions, the sensor exhibits a linear range of 0.01-200 nM and a limit of detection of 0.07 nM (S/N = 3). The developed dual-recognition aptasensor would provide a novel and rapid method for specific detection of AFM1 in milk.

Nanomaterials for fluorescent detection of vitamin B2: A review

Vitamin B2 plays vital roles in maintaining human health. It is of tremendous significance to construct sensitive sensors of VB2. In this review, we first briefly presented the sensing mechanisms of fluorescent nanomaterials for sensing VB2. Subsequently, the advances of nanomaterials for fluorescent determination of VB2 were highlighted. And sensing performance of traditional approaches and fluorescent nanosensors was further compared. In last section, the challenges and perspectives concerning the topic were discussed.

Simultaneous determination of macrolides in water samples by solid-phase extraction and capillary electrophoresis

Solid-phase extraction (SPE) coupled with capillary electrophoresis (CE) for the determination of macrolide antibiotics (azithromycin, clarithromycin, roxithromycin, tylosin) and tiamulin in water samples was described in this article. These compounds were extracted with different types of sorbents ( Oasis HLB, C18, C8, SDB, and Strata-X) and different masses of sorbents (60 mg, 200 mg, and 500 mg) using different organic solvents (methanol, ethanol, and acetonitrile) and different pH values of water samples (pH 7.00, 8.00, and 9.00). It was found that the highest extraction efficiency of the studied compounds was obtained with 200 mg/3 mL C18 cartridges with methanol as eluent at pH 9.00 of the water sample. The developed SPE-CE method for macrolide antibiotics and tiamulin was validated for linearity, precision, repeatability, the limit of detection (LOD), the limit of quantification (LOQ), and recovery. Good linearity was obtained in the range of 0.3-30 mg L-1 depending on the drug, with correlation coefficients higher than 0.9958 in all cases except clarithromycin (0.9873). Expanded measurement uncertainties were calculated for each pharmaceutical, accounting for 20.31 % (azithromycin), 38.33 % (tiamulin), 28.95 % (clarithromycin), 26.99 % (roxithromycin), and 21.09 % (tiamulin). Uncertainties associated with precision and calibration curves contributed the most to the combined measurement uncertainty. The method was successfully applied to the analysis of production waste-water from the pharmaceutical industry.

Silicon Nanoparticle-Based Ratiometric Fluorescence Probes for Highly Sensitive and Visual Detection of VB2

In this work, blue fluorescent silicon nanoparticles (SiNPs) were prepared by a simple one-step hydrothermal method using (3-aminopropyl) triethoxy silane (APTES) and eriochrome black T as raw materials. The SiNPs showed favorable water solubility, thermal stability, pH stability, salt tolerance, and photobleaching resistance. At an excitation wavelength of 376 nm, the SiNPs emitted bright blue fluorescence at 460 nm. In the presence of vitamin B₂ (VB₂), the fluorescence intensity (FL intensity) of the SiNPs at 460 nm decreased obviously, and a new peak appeared at 521 nm. Based on this, a novel ratiometric fluorescence method was established for VB₂ detection. There was a good linear relationship between the fluorescence intensity ratio (F ₅₂₁/F ₄₆₀) and VB₂ concentration from 0.5 to 60 μM with a detection limit of 135 nM. This method was successfully applied to detect VB₂ content in the samples of vitamin B₂ drugs and beverages. Additionally, a simple paper sensor based on the SiNPs was designed to visualize detection of VB₂. With the support of color recognition software on a smartphone, the visual quantitative analysis of VB₂ was realized, ranging from 40 to 800 μM.

Transition metal composites for selective analysis of vitamin B2 in rice by ultrahigh-performance liquid chromatography-tandem mass spectrometry

A novel amino-functionalized zinc ferrite nanoparticles/MXene (ZnFe₂O₄-NH₂/MXene composite which consist of ZnFe₂O₄-NH₂ and single/few layers MXene was designed and synthesized as an efficient extractant for analysis of vitamin B₂ in rice first combined with ultrahigh-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). As a result, the single/few layer MXene was tightly attached to the spherical ZnFe₂O₄-NH₂ nanoparticles by electrostatic self-assembly interaction, which present large specific surface area and fast mass transfer rate. The relevant experimental parameters, including the pH of the solution, extraction time, adsorbent amount, desorption solvent, desorption solvent volume and desorption time were investigated and optimized. Under optimum conditions, the ZnFe₂O₄-NH₂/MXene composite exhibited excellent selectivity and adsorption capacity for vitamin B₂ through hydrogen bonding interactions and the metal-π complexation interaction. The adsorption kinetics, isotherms, and thermodynamic studies were systemically investigated to evaluate the adsorption mechanism and characteristics, which ascribed to chemical adsorption, monolayer adsorption and a spontaneous endothermic process. Furthermore, the performance of the proved method was validated with the good linear correlation coefficient (r = 0.999), low limit of detection (0.86 ng·mL^-1) and the limit of quantification (2.98 ng·mL^-1), satisfactory recoveries (81.7-102.5%) and reasonable accuracy (RSD<7.8%). The theoretical and technological underpinning for investigating the kinship amongst vitamin alterations and the degree of rice storage was set using this suggested approach to assess vitamin B₂ in rice from various years.

Sensitive riboflavin sensing using silver nanoparticles deposited onto screen-printed electrodes via controlled-energy spark discharges

In this work, we elaborated the graphite screen-printed electrodes (SPEs) modification with metal nanoparticles formed as a result of spark discharges produced between a metal wire electrode and SPE that are connected to an Arduino board-based DC high voltage power supply. This sparking device allows, on the one hand, the toposelective formation of NPs of controlled dimensions through a direct and liquid-free approach, and on the other hand, controls the number and energy of the discharges delivered to the electrode surface during a single spark event. This way, the potential damage to the SPE surface by the action of heat evolved during the sparking process is considerably minimized compared with the standard setup in which each spark event consists of multiple electrical discharges. Data demonstrated that the sensing properties of the resulting electrodes are significantly improved compared with those achieved when conventional spark generators are employed, as demonstrated for silver-sparked SPEs that exhibit enhanced sensitivity to riboflavin. Sparked AgNp-SPEs were characterized using scanning electron microscopy and voltammetric measurements in alkaline conditions. The analytical performance of sparked AgNP-SPEs was evaluated by various electrochemical techniques. Under optimum conditions, the detection range for DPV was from 1.9 (LOQ) to 100 nM riboflavin (R2 = 0.997), while a limit of detection (LOD, S/N 3) of 0.56 nM was achieved. The analytical utility is demonstrated for the determination of riboflavin in the real matrices of B-complex pharmaceutical preparation and an energy drink.

Ag NPs/PMMA nanocomposite as an efficient platform for fluorescence regulation of riboflavin

The fluorescence detection platform has broad application in many fields. In this paper, we report a simple and efficient fluorescence detection platform based on the synergistic effects of Ag nanoparticles (Ag NPs) and polymethylmethacrylate (PMMA). Ag NPs were introduced to realize the plasmon enhancement fluorescence and a thin PMMA layer was used to adjust the distance between Ag NPs and riboflavin. The thin PMMA layer not only enhances the fluorescence by enhancing adhesion of substrate, but also optimizes the plasmon enhancement fluorescence effect by serving as the spacer. The fluorescence enhancement factor based on this platform shows a trend of increasing with the decrease of the concentration of riboflavin, and the detection of riboflavin is realized based on this feature, the lowest detectable concentration is as low as 0.27 µM. In addition to the detection based on plasmon enhancement fluorescence, the detection of riboflavin at low concentrations can also be realized by the shift and broadening of the fluorescence peak due to the Ag NPs. The combination of the two ways of plasmon enhancement fluorescence and shift of the fluorescence spectra is used for the detection of riboflavin. These results show that the platform has great potential applications in the field of detection and sensing.

A facile fabrication of ratiometric electrochemical sensor for sensitive detection of riboflavin based on hierarchical porous biochar derived from KOH-activated Soulangeana sepals

Herein, a facile ratiometric electrochemical method was developed for sensitive sensing of riboflavin (RF) based on hierarchical porous biochar (HPB) modified electrode. In this sensing system, the reference paracetamol (PA) was directly added into electrolyte solution without the requirement of complex immobilization process. HPB derived from KOH-activated Soulangeana sepals displays hierarchical porous structure, high specific surface area and rich oxygen-containing functional groups, which is favorable for RF adsorption and enrichment. Besides, the excellent electronic conductivity and superior electrocatalytic activity of HPB can effectively promote the electrooxidation of RF. Moreover, the dual-signal strategy greatly improves the reproducibility and reliability of electrochemical detection. Based on the proposed ratiometric sensing platform, the sensor exhibits a wider linear range of 0.0007-10μM and a lower limit of detection of 0.2 nM. The method also presents good selectivity and has been applied to the determination of RF in milk samples with satisfactory results.

An integrated plastic microchip for enhancing electrophoretic separation using tunable pressure-driven backflows

Microfluidic CE (MCE) is an effective solution for rapid and sensitive determination of multiple analytes. Herein, a dynamic coated cyclic olefin copolymer microchip was developed having an on-chip micropump for fluid velocity adjusting in electrophoretic separations. This micropump was fabricated by constructing a polyacrylamide gel membrane at one channel terminal. Once applying electric field across the membrane, a pressure-driven flow generated automatically to balance the electroosmotic flow (EOF) mismatch at the channel-membrane interface. The influence of gel precursor concentration and operating voltages on the fluid velocity was carefully evaluated. Moreover, the highly integration of injection, separation, and pumping units of the MCE system minimized the dead volume and provides satisfied column efficiency. Experiments showed that by adjusting of pumping voltage reduced the fluid velocity by a factor of 6, resulting six- and threefold resolving power enhancements of rhodamine dye mixture and amino acid mixture, respectively. Furthermore, the developed MCE method was applied for rhodamines and amino acids quantitation in food and cosmetics, with standard addition recoveries of 87.3-106.9% and 89.9-117.4%, respectively. These results were also confirmed by standard HPLC method, revealing the application potential in fast and onsite analysis of complex samples.

Quinoa flour as a skim milk powder replacer in concentrated yogurts: Effect on their physicochemical, technological, and sensory properties

Milk standardization with solids (i.e., nonfat milk solids, MSNF) for yogurt manufacture is traditionally achieved by the addition of skim milk powder (SMP). However, the addition of SMP to milk‐based yogurt increases lactose content and decreases both protein content and gel firmness. Thus, in this work, quinoa flour (QF; 0%, 25%, 50%, 75%, and 100% w/w) was used to replace SMP in concentrated yogurt. The physicochemical, textural, and sensory properties and microstructure of the yogurt were evaluated during cold storage. Generally, protein content, water‐holding capacity, and L* value decreased, while syneresis, textural attributes, and viscosity increased with increasing QF content. The substitution of high levels of QF (>25%, w/w) for SMP led to significantly shorter fermentation times, as compared to the control sample. The scanning electron microscopy observations showed significant changes in the yogurt microstructure as a consequence of QF replacement. Samples with 25% (w/w) substitution of QF and control had the highest scores in overall acceptance. According to the results, QF could be applied as an interesting raw material for concentrating the milk‐based yogurt at substitution level of 25% (w/w).