Modified EMR-lipid method combined with HPLC-MS/MS to determine folates in egg yolks from laying hens supplemented with different amounts of folic acid

3D printing of electrochemical cell for voltammetric detection and photodegradation monitoring of folic acid in juice samples

In this study, compact 3D-printed carbon black (CB) electrodes were manufactured for using in folic acid (FA) analysis in fruit samples. Before application in FA analysis, the electrode surfaces were characterized by high-resolution scanning electron microscopy and voltammetry using well-known redox probes. Square wave voltammetric study presented linear responses in the range between 10 and 200 µmol/L (R2 > 0.99), exhibited a suitable detection limit (LOD) of ∼ 5.1 µmol/L and acceptable performance in terms of reproducibility and anti-interference experiments. The analysis of FA in four different food samples using the proposed method agreed statistically with a comparative technique based on spectrophotometric measurements. Moreover, results from photostability experiments indicated that FA can be degraded after 5 and 20 min of UV exposure. These results successfully demonstrated the analytical feasibility of the 3D-printed electrodes as sensing material and for monitoring the photostability of FA in different fruit matrices.

In situ electrodeposition of bismuth oxide nanowires @MWNT on the carbon fiber microelectrode for the sensitively electrochemical detection of folic acid

A microminiaturized electrochemical device, BiO@CNW/CFE was fabricated based on the in situ co-electrodeposition of bismuth oxide nanowires (BiNWs) and multi-walled carbon nanotubes (MWNTs) on the surface of carbon fiber electrode (CFE). The nanostructure of BiNWs could bind MWNTs on the surface of CFE during the precipitation of bismuth at the potential of -1.1 V. The vimineous nanostructure of BiO@CNW improved the surface area and electrochemical activity of the microelectrode. With the low background noise, folic acid (FA) can be detected sensitively by BiO@CNW/CFE based on the electrochemical reduction via the method of square wave voltammetry. The linear range of FA in sodium acetate-acetic acid buffer was achieved in the range of 5.00 nM-200 nM, the detection limit was estimated to be 0.63 nM. The recoveries of FA in human serum and artificial cerebral spinal fluid were between 99% and 103%, which indicates BiO@CNW/CFE was a reliable sensor for the detection of FA in biological samples.

Rapid Analysis of Residues of 186 Pesticides in Hawk Tea Using Modified QuEChERS Coupled with Gas Chromatography Tandem Mass Spectrometry

In this work, the QuEChERS method was modified and evaluated for the determination of 186 pesticides from caffeine-free and fatty hawk tea prior to their gas chromatography tandem mass spectrometry analysis for the first time. The results showed that the combination of MgSO₄ + PSA + MWCNTs plus EMR-Lipid provided the lowest matrix effect and best recovery; 117 of 186 pesticides manifested weak matrix effects. Thus, for accurate quantification, it is necessary to use matrix-matched calibration curves to compensate for the matrix effect. At the spiked level of 0.1 mg/kg, the average recoveries of 184 pesticides were in the range of 70-120% and the RSDs were 0.3-14.4% by the modified method. Good linearity was shown for 186 analytes at concentration of 0.01 mg/L~0.4 mg/L, and the correlation coefficients exceeded 0.99 for 182 pesticides. The detection limits of 186 pesticides by the modified QuEChERS method were 0.001-0.02 mg/kg, and the limits of quantification (LOQ) were 0.005 mg/kg~0.05 mg/kg. The necessity of solvent exchange is also explained in this work. The successful application of the modified QuEChERS in real samples proved that this method could be one of the routine options for analysis of herbal tea.

Efficient synthesis of yellow-green carbon quantum dots as a sensitive fluorescent probe of folic acid

Bright yellow-green carbon quantum dots (YGCDs) have been successfully synthesized by a simple and efficient hydrothermal method. Its luminescent absolute quantum yield reached 30.0% in 4 h, compared with that using common reported solvothermal method, the synthesis time was reduced more than 70% with tin oxide nano particles as a catalyst. Moreover, the fluorescence of YGCDs could be selectively quenched by folic acid (FA) molecules, and the relative fluorescence intensities of F/F0 was fitted perfectly in line decay curve versus the concentration of FA in the range of 2.0 × 10-8 mol/l ~ 1.0 × 10-5 mol/l (R2 = 0.9988). The detection limit of FA was below 2.0 × 10-8 mol/l, suggesting a promising fluorescent probe of folic acid.

Determination of Folic Acid Using Biosensors-A Short Review of Recent Progress

Folic acid (FA) is the synthetic surrogate of the essential B vitamin folate, alternatively named folacin, pteroylglutamic acid or vitamin B9. FA is an electroactive compound that helps our body to create and keep our cells healthy: it acts as the main character in a variety of synthetic biological reactions such as the synthesis of purines, pyrimidine (thus being indirectly implied in DNA synthesis), fixing and methylation of DNA. Therefore, physiological folate deficiency may be responsible for severe degenerative conditions, including neural tube defects in developing embryos and megaloblastic anaemia at any age. Moreover, being a water-soluble molecule, it is constantly lost and has to be reintegrated daily; for this reason, FA supplements and food fortification are, nowadays, extremely diffused and well-established practices. Consequently, accurate, reliable and precise analytical techniques are needed to exactly determine FA concentration in various media. Thus, the aim of this review is to report on research papers of the past 5 years (2016-2020) dealing with rapid and low-cost electrochemical determination of FA in food or biological fluid samples.

Identification of the prepared foods promising for dietary folate intake in Beijing, China

The aim of the present study was to analyze folate content and composition in foods consumed daily by Chinese people. The concentration of seven folate derivatives in sixty-four selected foods was determined by a liquid-chromatography tandem-mass spectrometry method. The total folate levels ranged from 0.28 to 129 µg/100 g fresh weight, with an average of 21.18 μg/100 g. The highest folate content was found in boiled egg yolk and waxy corn (>120 µg/100 g), abundant folate levels in cooked vegetables such as hot pepper, spinach, soybean sprout, stem lettuce, coriander, and broccoli (44-72 µg/100 g), and lowest in Coca Cola (0.28 µg/100 g). 5-Methyl-tetrahydrofolate was the major folate derivative in various foods, accounting for 72% of the total folates on average, with the highest being 90% in egg yolk. These data will enable estimation of the daily folate intake and allow dietary recommendations to improve folate status in humans.