Toxicity detection of sodium nitrite, borax and aluminum potassium sulfate using electrochemical method

Detection of Sodium Formaldehyde Sulfoxylate, Aluminum, and Borate Compounds in Bread and Pasta Products Consumed by Residents in Jilin Province, China

ABSTRACT

Food additives are widespread in the human diet; however, their excessive intake can have an impact on the quality of health. This study evaluated food additives in bread and pasta products consumed by residents in various regions of Jilin Province, People's Republic of China, from 2019 to 2021. We collected samples of bread and six types of pasta products from farmers' markets and morning markets and used high-performance liquid chromatography, UV-visible spectrophotometry, and graphite furnace atomic absorption spectrometry to detect the content of the following food additives: sodium formaldehyde sulfoxylate, aluminum, and borate compounds. For 836 samples in total, we detected the presence of sodium formaldehyde sulfoxylate, aluminum, and borate compounds in excess rates reaching 3.5, 10, and 4.7%, respectively. Aluminum in fried breadsticks exceeded the standard by 40%. The results of this study can be used to assess the overall pass rate of bread and pasta products sold in Jilin Province and support the detection of possible food safety problems.

HIGHLIGHTS

Low consumption and portable technology for dithionite detection based on potassium ferricyanide differential spectrophotometry method in related advanced oxidation processes

Carbon neutrality has been received more attention and emerged in wastewater treatment processes. Due to the development of treating technologies with the rising of new-emerging pollutants, the coupled chemical processes also should remain current for the goal of carbon-neutral operation. Among of those updated strategies, several advanced oxidation processes (AOPs) based on dithionite (DTN, S₂O₄^2-), a common water treatment agent, have been established for refractory organic contaminations removal. However, in terms of DTN detection, the traditional formol-titration method has several application limits including the low detection sensitivity and high consumption of formaldehyde. In this study, compared with traditional method, a low energy consumption technology has been developed based on the potassium ferricyanide with the carbon consumption decreasing by about 5 times. Moreover, detection limit of DTN (mmol/L level) also was lower than the titration method. The method was established based on the fact that every 1 mol of DTN can react with 2 mol [Fe(CN)₆]^3- under alkaline condition. According to that potassium ferricyanide (K₃ [Fe(CN)₆]) has the maximum absorption at 419 nm wavelength, a fitting equation based on the linear relationship between the absorbance variation of K₃ [Fe(CN)₆] and DTN amount in the ranges of 0-30 μmol with the detection limit of 0.6 μmol was established with the determination coefficient of 0.99935. It was found that there was no obvious influence of the ubiquitous foreign species with the amount lower than 6 mM, 4 mM, 6 mM, 4 mM and 1 mg/L for Cl^-, HCO₃^-, NO₃^-, SO₄^2- and NOM, respectively. Moreover, methanol and tert-butanol were employed to verify the influence of the presence of organic matters on the determination of DTN and no impact was observed in this study. The proposed method provides a new way for DTN detection with stable and countable performance in the related AOPs with the low electric energy and carbon source consumption and high detection efficiency.

Fabrication of a Novel, Cost-Effective Double-Sided Indium Tin Oxide-Based Nanoribbon Electrode and Its Application of Acute Toxicity Detection in Water

Microelectrode plays a crucial role in developing a rapid biosensor for detecting toxicity in water. In this study, a nanoribbon electrode (NRE) with amplified microelectrode signal was successfully prepared by electrodepositing 2-allylphenol on a double-sided indium tin oxide glass. The NRE provided a simple mean for obtaining large steady-state current response. Its advantages were discussed by contrasting the toxicity detection of 3,5-dichlorophenol (DCP) with single microelectrode, microelectrode array, and millimeter electrode as working electrodes in which potassium ferricyanide (K₃[Fe(CN)₆]) was adopted as a mediator, and Escherichia coli was selected as bioreceptor. At a constant potential of 450 mV, the current reached a steady state within 10 s. The biosensor was constructed using the NRE as working electrode, and its feasibility was verified by determining the toxicity of DCP. A 50% inhibitory concentration (IC₅₀) of 3.01 mg/L was obtained by analyzing the current responses of different concentrations of DCP within 1 h. These results exhibited that the proposed method based on the as-prepared NRE was a rapid, sensitive, and cost-effective way for toxicity detection in water.

An unexpected discovery of 1,4-benzoquinone as a lipophilic mediator for toxicity detection in water

Since most toxicological risk assessments are based on individual single-species tests, there is uncertainty in extrapolating these results to ecosystem assessments. Herein, we successfully developed a mediated microbial electrochemical biosensor with mixed microorganisms for toxicity detection by microelectrode array (MEA). In order to fully mobilize all the mixed microorganisms to participate in electron transfer to amplify the current signal, 1,4-benzoquinone (BQ) was used as the lipophilic mediator to mediate the intracellular metabolic activities. Hydrophilic K₃[Fe(CN)₆] was employed as an extracellular electron acceptor to transport electrons from hydroquinone (HQ) to the working electrode. Under the optimal conditions of 50 mM phosphate buffer solution (PBS), 0.4 mM BQ, 10 mM K₃[Fe(CN)₆] and OD₆₀₀ = 0.5 bacteria concentration, the half-maximal inhibitory concentration (IC₅₀) values measured with the composite-mediated respiration (CM-RES) of BQ-K₃[Fe(CN)₆] for Cu²⁺, Cd²⁺ and Zn²⁺ were 5.95, 7.12 and 8.86 mg L^-1, respectively. IC₅₀ values obtained with the single mediator K₃[Fe(CN)₆] were 2.34, 5.88 and 2.42 mg L^-1 for the same samples. The results indicate that the biosensor with the single mediator K₃[Fe(CN)₆] had higher sensitivity to heavy metal ions than the biosensor with composite mediators. After verification, we found that the addition of BQ cannot amplify the current. The IC₅₀ value of 0.89 mg L^-1 for BQ was obtained using K₃[Fe(CN)₆] as the single mediator. This suggests that BQ is highly toxic, which explained why the sensitivity of the biosensor with the combined mediator BQ-K₃[Fe(CN)₆] was lower than that of the biosensor with the single mediator K₃[Fe(CN)₆]. At the same time, this also implies that toxicity itself cannot be ignored when it is used as an electronic mediator in a mediated microbial electrochemical biosensor.

Recent advances in controlling denitritation for achieving denitratation/anammox in mainstream wastewater treatment plants

Denitratation (NO₃^-→NO₂^-)/anammox is a promising method for anammox application in mainstream wastewater treatment plants (WWTPs) to reduce oxygen and organic matter consumption. Achieving nitrite production via denitratation and controlling denitritation (NO₂^-→N₂) is the basis of the denitratation/anammox process. To control denitritation, the denitrifying biocommunity and growth rate are critically reviewed for biocommunity optimization. Then, the short-term and long-term effects of pH on denitritation were summarized and the possible mechanism was discussed, along with the effect of C/N ratio and organic matter type on denitritation. Meanwhile, the strategies for producing nitrite via controlling denitritation are discussed, as well as the processes for achieving nitrogen removal via denitratation/anammox in WWTPs. Finally, the practical application of denitratation/anammox in a full-scale mainstream WWTP is documented.

A novel ultrasensitive surface plasmon resonance-based nanosensor for nitrite detection

Nitrite is a common food additive, however, its reduction product, nitrosamine, is a strong carcinogen, and hence the ultra-sensitive detection of nitrite is an effective means to prevent related cancers. In this study, different sized gold nanoparticles (AuNPs) were modified with P-aminothiophenol (ATP) and naphthylethylenediamine (NED). In the presence of nitrite, satellite-like AuNPs aggregates formed via the diazotization coupling reaction and the color of the system was changed by the functionalized AuNPs aggregates. The carcinogenic nitrite content could be detected by colorimetry according to the change in the system color. The linear concentration range of sodium nitrite was 0-1.0 μg mL-1 and the detection limit was determined to be 3.0 ng mL-1. Compared with the traditional method, this method has the advantages of high sensitivity, low detection limit, good selectivity and can significantly lower the naked-eye detection limit to 3.0 ng mL-1. In addition, this method is suitable for the determination of nitrite in various foods. We think this novel designed highly sensitive nitrate nanosensor holds great market potential.

Small Microbial Three-Electrode Cell Based Biosensor for Online Detection of Acute Water Toxicity

The monitoring of toxicity of water is very important to estimate the safety of drinking water and the level of water pollution. Herein, a small microbial three-electrode cell (M3C) biosensor filled with polystyrene particles was proposed for online monitoring of the acute water toxicity. The peak current of the biosensor related with the performance of the bioanode was regarded as the toxicity indicator, and thus the acute water toxicity could be determined in terms of inhibition ratio by comparing the peak current obtained with water sample to that obtained with nontoxic standard water. The incorporation of polystyrene particles in the electrochemical cell not only reduced the volume of the samples used, but also improved the sensitivity of the biosensor. Experimental conditions including washing time with PBS and the concentration of sodium acetate solution were optimized. The stability of the M3C biosensor under optimal conditions was also investigated. The M3C biosensor was further examined by formaldehyde at the concentration of 0.01%, 0.03%, and 0.05% (v/v), and the corresponding inhibition ratios were 14.6%, 21.6%, and 36.4%, respectively. This work provides a new insight into the development of an online toxicity detector based on M3C biosensor.

New applications of genetically modified Pseudomonas aeruginosa for toxicity detection in water

A novel mediator-free method based on genetically modified bacteria was developed for detecting water toxicity, where genetically modified Pseudomonas aeruginosa (GM P. aeruginosa) was selected as the biosensor strain and pyocyanin (PYO) produced by this strain was used as the indicator. The toxicity response of GM P. aeruginosa to 3, 5-dichlorophenol (3, 5-DCP) was measured electrochemically and spectroscopically, and the half maximal inhibitory concentration (IC₅₀) of 3, 5-DCP was determined to be 15.1 mg/L. Strikingly, the toxicity of sample solution with 3, 5-DCP could also be estimated visually by naked eyes at a concentration as low as 10 mg/L. The present study provided a convenient, sensitive and cost-effective method for water toxicity detection, and extended biosensing application of the genetically modified bacterium.