Fluorine contamination, mobility, and risks in soils at a phosphate-gypsum waste landfill: a new analytical method and comparison with previous methods.

This study used a new X-ray fluorescence (XRF)-based analytical method with better precision and sensitivity to evaluate the fluorine concentrations in soil. It was hypothesized that the XRF method with a pellet-synthesizing procedure may effectively analyze the fluorine concentrations in soil with ease and reliability. The total fluorine concentrations determined using XRF were compared with those determined using three different types of analytical protocols-incineration/distillation, alkaline fusion, and aqua regia extraction procedures. Among the three procedures, the incineration/distillation procedure did not show reliable precision and reproducibility. In contrast, the total fluorine concentrations determined using the XRF analysis were linearly correlated with those determined using the alkaline fusion and aqua regia extraction procedures. Based on the results of the Korean waste leaching procedure and toxicity characteristics leaching procedure, the leachability of fluorine from soil and waste was not directly related to total fluorine concentrations in soil. Risk assessment also revealed that the fluorine-rich soils did not show non-carcinogenic toxic effects, despite exceeding the regulation level (800 mg/kg) in South Korea for total fluorine concentrations in soil. Our results suggest that XRF analysis in combination with the newly developed pretreatment method may be a promising alternative procedure for easily and rapidly determining the total fluorine concentration in soil. However, further efforts are needed to evaluate fluorine leachability and its associated risks in fluorine-contaminated soils.

Differential mRNA profiles reveal the potential roles of genes involved in lactate stimulation in mouse macrophages.

Lactate is a glycolysis end product, and its levels are markedly associated with disease severity, morbidity, and mortality in sepsis. It modulates key functions of immune cells, including macrophages. In this investigation, transcriptomic analysis was performed using lactic acid, sodium lactate, and hydrochloric acid-stimulated mouse bone marrow-derived macrophages (iBMDM), respectively, to identify lactate-associated signaling pathways. After 24 h of stimulation, 896 differentially expressed genes (DEG) indicated were up-regulation, whereas 792 were down-regulated in the lactic acid group, in the sodium lactate group, 128 DEG were up-regulated, and 41 were down-regulated, and in the hydrochloric acid group, 499 DEG were up-regulated, and 285 were down-regulated. Subsequently, clinical samples were used to further verify the eight genes with significant differences, among which Tssk6, Ypel4, Elovl3, Trp53inp1, and Cfp were differentially expressed in patients with high lactic acid, indicating their possible involvement in lactic acid-induced inflammation and various physiological diseases caused by sepsis. However, elongation of very long chain fatty acids protein 3 (Elovl3) was negatively correlated with lactic acid content in patients. The results of this study provide a necessary reference for better understanding the transcriptomic changes caused by lactic acid and explain the potential role of high lactic acid in the regulation of macrophages in sepsis.

Comparative study on liquid versus gas phase hydrochloric acid hydrolysis for microcrystalline cellulose isolation from sugarcane bagasse.

Microcrystalline cellulose (MCC) was successfully synthesized from sugarcane bagasse using a rapid, low-temperature hydrochloric acid (HCl) gas treatment. The primary aim was to develop an energy-efficient "green" cellulose extraction process. Response surface methodology optimized the liquid-phase hydrolysis conditions to 3.3 % HCl at 117 °C for 127 min to obtain MCC with 350 degree of polymerization. An alternative gas-phase approach utilizing gaseous HCl diluted in hot 40 °C air was proposed to accelerate MCC production. The cellulose pulp was moistened to 15-18 % moisture content and then exposed to HCl gas, which was absorbed by the moisture in the cellulose fibers to generate a highly concentrated acidic solution that hydrolyzed the cellulose. The cellulose pulp was isolated from depithed bagasse through soda pulping, multistage bleaching and cold alkali purification. Hydrolysis was conducted by saturating the moist cellulose fibers with gaseous HCl mixed with hot air. Extensive analytical characterization using FT-IR, XRD, SEM, TGA, DSC, particle size, and porosity analyses verified comparable physicochemical attributes between MCC samples prepared via liquid and gas phase methods. The gas-produced MCC revealed 85% crystallinity, 71 Å crystallite dimensions, and thermally stable rod-shaped morphology with an average diameter below 200 µm. The similar material properties validate the proposed gas-based technique as an equally effective yet more energy-efficient alternative to conventional aqueous acid hydrolysis for fabricating highly pure MCC powders from lignocellulose. This sustainable approach enables the value-addition of sugarcane bagasse agro-industrial residue into cellulosic nanomaterials for wide-ranging industrial applications. In summary, the key achievements of this work are rapid MCC production under mild temperatures using HCl gas, optimization of liquid phase hydrolysis, successful demonstration of gas phase method, and extensive characterization verifying equivalence between both protocols. The gas methodology offers a greener cellulose extraction process from biomass.

An Alternative Procedure for a Win-win African-Swiss Cooperation in Gold Production in Africa.

The growth of Africa as a major gold (Au) exporter can not only strengthen economic ties with other parts of the world, but also lead to solutions to global industrial challenges, and the only way to stop gold smuggling out of gold-producing African countries seems to be having multiple refineries in Africa, for which developing gold-producing African countries might need technological assistance provided by a more developed country, especially Switzerland. In this Note, the chemistry of gold mining was discussed, and the idea is conveyed that if aqua regia is used as a main reagent in both gold mining and the electrolytic refinement of gold, then the two systems of gold mining and gold refining can be coupled industrially and geographically, and such a coupling can facilitate the growth of home-grown gold refineries in gold-producing African countries. It is also discussed that with Swiss companies finding it economical to properly use aqua regia in Africa as described, a win-win African-Swiss cooperation will be established that will benefit both the Swiss companies and gold-producing African countries. Further, it is concluded that the addressed cooperation will be accompanied by four of the seventeen goals called 'Sustainable Development Goals' by the United Nations.

Comparative study on composition and functional properties of brewer's spent grain proteins precipitated by citric acid and hydrochloric acid.

Brewer's spent grain (BSG) is an abundant agro-industrial residue and a sustainable low-cost source for extracting proteins. The composition and functionality of BSG protein concentrates are affected by extraction conditions. This study examined the use of citric acid (CA) and HCl to precipitate BSG proteins. The resultant protein concentrates were compared in terms of their composition and functional properties. The BSG protein concentrate precipitated by CA had 10% lower protein content, 5.8% higher carbohydrate, and 5.4% higher lipid content than the sample precipitated by HCl. Hydrophilic/hydrophobic protein and saturated/unsaturated fatty acid ratios increased by 16.9% and 26.5% respectively, in the sample precipitated by CA. The formation of CA-cross-linkages was verified using shotgun proteomics and Fourier transform infrared spectroscopy. Precipitation by CA adversely affected protein solubility and emulsifying properties, while improving foaming properties. This study provides insights into the role of precipitants in modulating the properties of protein concentrates.

A high loading nanocarrier for the 5-fluorouracil anticancer drug based on chloromethylated graphene.

In the present work, we report a facile and simple strategy to functionalize graphene with the chloromethyl (CH2Cl) functional group as a nanoplatform for effectual loading of the 5-fluorouracil (5-FU) anticancer drug. To achieve the highest loading capacity, hydrochloric acid concentration, the quantity of paraformaldehyde, ultrasonic treatment time, and stirring duration were all carefully optimized. The results revealed that the optimum conditions for functionalizing graphene were obtained at 70 mL of hydrochloric acid, 700 mg of paraformaldehyde, and times of 35 min and 2 h of ultrasonication and stirring. Later, the drug (5-FU) was loaded onto CH2Cl-functionalized graphene through hydrogen bonding and π-π interactions. The chemical structure of the functionalized material and the loading of the 5-FU drug were confirmed by FTIR analysis, scanning electron microscopy, and X-ray photoelectron spectroscopy. The 5-FU loading capacity of as-prepared materials was determined using the ion chromatography instrument. Our findings demonstrate that chloromethylated graphene is a very excellent nano-platform for high-efficiency drug loading, yielding a loading capacity of 52.3%, comparatively higher than pure graphene (36.54%).

[A case of acute respiratory distress syndrome induced by inhalation of hydrogen chloride].

Poisoning induced by inhalation of hydrogen chloride has significant effects on the respiratory system. It can cause severe pulmonary edema and acute respiratory distress syndrome (ARDS) in the early stage, and even death in critical cases. As a novel treatment for ARDS, the efficacy of sivelestat sodium in infection-induced ARDS has been widely verified, but its application in ARDS caused by chemical poisoning is still scarce in literature. Here we report a case of ARDS induced by hydrogen chloride inhalation which was successfully treated with sivelestat sodium and conventional treatment.

DTTZ suppresses ferroptosis and reverses mitochondrial dysfunction in normal tissues affected by chemotherapy.

Conventional antineoplastic therapies cause severe normal tissue damage and existing cytoprotectants with acute toxicities or potential tumor protection limit their clinical application. We evaluated the selective cytoprotection of 2,2-dimethylthiazolidine hydrochloride in this study, which could protect normal tissue toxicity without interfering antineoplastic therapies. By using diverse cell lines and A549 xenograft model, we discovered a synthetic aminothiol 2,2-dimethylthiazolidine hydrochloride selectively diminished normal cellular ferroptosis via SystemXc-/Glutathione Peroxidase 4 pathway upon antineoplastic therapies without interfering the anticancer efficacy. We revealed the malignant and non-malignant tissues presenting different energy metabolism patterns. And cisplatin induces disparate replicative stress, contributing to the distinguishable cytoprotection of 2,2-dimethylthiazolidine in normal and tumor cells. The compound pre-application could mitigate cisplatin-induced normal cellular mitochondrial oxidative phosphorylation (OXPHOS) dysfunction. Pharmacologic ablation of mitochondria reversed 2,2-dimethylthiazolidine chemoprotection against cisplatin in the normal cell line. Combined, these results provide a potential therapeutic adjuvant to selectively diminish normal tissue damages retaining antineoplastic efficacy.

Eco-friendly anti-corrosion performance of chitosan modified with fused heterocyclic compound on mild steel in acidic medium.

This study aims to explore the prevention of chitosan modified with a fused heterocyclic compound as a sustainable corrosion inhibitor for mild steel in 1 M HCl. Electrochemical instruments, including potentiodynamic polarization techniques, and electrochemical impedance spectroscopy (EIS), were employed to evaluate the corrosion protection performance. The outcomes showed that the chitosan modified with a fused heterocyclic compound has outstanding inhibition performance, with an inhibition effectiveness of 98.25 % at 100 ppm. The anti-corrosion features of modified chitosan were ascribed to the presence of hetero atoms in modified chitosan composite which leads to the creation of a protective layer, The modified chitosan composite behaved as mixed-typed inhibitors, as shown by the PDP results. The modified chitosan composite adsorbs on mild steel in the investigated corrosive media via chemisorption interactions, and its adsorption followed the Langmuir adsorption model. Furthermore, increasing the temperature from 303 to 333 K enhanced the corrosion rate, most likely due to the desorption of the inhibitor agent from the steel surface.

HSP70 Is a Critical Regulator of HSP90 Inhibitor's Effectiveness in Preventing HCl-Induced Chronic Lung Injury and Pulmonary Fibrosis.

Exposure to hydrochloric acid (HCl) can provoke acute and chronic lung injury. Because of its extensive production for industrial use, frequent accidental exposures occur, making HCl one of the top five chemicals causing inhalation injuries. There are no Food and Drug Administration (FDA)-approved treatments for HCl exposure. Heat shock protein 90 (HSP90) inhibitors modulate transforming growth factor-ß (TGF-ß) signaling and the development of chemical-induced pulmonary fibrosis. However, little is known on the role of Heat Shock Protein 70 (HSP70) during injury and treatment with HSP90 inhibitors. We hypothesized that administration of geranylgeranyl-acetone (GGA), an HSP70 inducer, or gefitinib (GFT), an HSP70 suppressant, alone or in combination with the HSP90 inhibitor, TAS-116, would improve or worsen, respectively, HCl-induced chronic lung injury in vivo and endothelial barrier dysfunction in vitro. GGA, alone, improved HCl-induced human lung microvascular endothelial cells (HLMVEC) barrier dysfunction and, in combination with TAS-116, improved the protective effect of TAS-116. In mice, GGA reduced HCl toxicity and while TAS-116 alone blocked HCl-induced chronic lung injury, co-administration with GGA, resulted in further improvement. Conversely, GFT potentiated HCl-induced barrier dysfunction and impaired the antidotal effects of TAS-116. We conclude that combined treatments with HSP90 inhibitors and HSP70 inducers may represent a novel therapeutic approach to manage HCl-induced chronic lung injury and pulmonary fibrosis.

DSC, TGA-FTIR and FTIR Assisted by Chemometric Factor Analysis and PXRD in Assessing the Incompatibility of the Antiviral Drug Arbidol Hydrochloride with Pharmaceutical Excipients.

Arbidol hydrochloride is an antiviral product widely used in Russia and China for the treatment of, among other diseases, influenza. In recent years, it has turned out to be highly effective against COVID-19. However, there is little knowledge about its physicochemical properties and its behavior in the presence of various pharmaceutical excipients, which could be useful in the development of new preparations by increasing its solubility and bioavailability. For this reason, binary mixtures composed of arbidol hydrochloride and selected pharmaceutical excipients such as chitosan, polyvinylpyrrolione K-30 and magnesium stearate were prepared and subjected to differential scanning calorimetry (DSC), thermogravimetry combined with Fourier transform infrared spectrometry (TGA-FTIR) and Fourier transform infrared spectrometry (FTIR) analyses. In order to obtain clarity in the interpretation of the outcomes, chemometric calculations with factor analysis (FA) were used. Additionally, a powder X-ray diffraction (PXRD) and an intrinsic dissolution rate study were performed for arbidol hydrochloride itself and in the presence of excipients. As a result of the study, it was revealed that arbidol hydrochloride may undergo polymorphic transformations and be incompatible with chitosan and magnesium stearate. However, mixing arbidol hydrochloride with polyvinylpyrrolidone K-30 guarantees the obtaining of durable and safe pharmaceutical preparations.

Acid induced dispersive liquid-liquid microextraction based on in situ formation of hydrophobic deep eutectic solvents for the extraction of bisphenol A and alkylphenols in water and beverage samples.

This study describes the development of an acid induced dispersive liquid-liquid microextraction method based on the in situ formation of hydrophobic deep eutectic solvents for the extraction of bisphenol A and alkylphenols from environmental water and beverage samples. Hydrochloric acid altered the hydrophilic-hydrophobic state of fatty acid salts to obtain hydrophobic fatty acids, which formed hydrophobic deep eutectic solvents with analytes in situ to extract the analytes. Under optimized conditions, the limits of detection and limits of quantitation were 0.03-0.1 µg L-1 and 0.12-0.3 µg L-1, the intraday and interday relative standard deviations were less than 3.9 %, and the enrichment factor was 29-32. The recoveries of bisphenol A and alkylphenols were 95.9-104.9 % and 86.9-105.0 %, respectively. The extraction process used only hydrochloric acid and fatty acid salts, and the extraction process required less than 1 min. This method has the advantages of simplicity, speed, low cost and environmental friendliness.

Development of a fluorometric Cuboni test for the semi-quantitative measurement of urinary estrogen levels and pregnancy detection in mares.

The aim of the present study was to develop a semi-quantitative urine pregnancy test for mares based on the Cuboni reaction and to verify the reliability of this test. The urine specimens were hydrolyzed by heating in the presence of hydrochloric acid. The resulting free estrogens were extracted from the urine matrix using toluene. Sulfuric acid was added to the toluene extract and the mixture was heated again. The lower layer in the test tube containing sulfuric acid was used for fluorescence measurements with excitation at 355 nm and measurement at 535 nm. The fluorometric Cuboni test revealed that the fluorescence counts in urine samples collected after the second trimester of gestation were significantly higher than those obtained from barren mares. The levels of estrogens, including equilin, estrone and estardiol-17ß exhibited a dose-dependent increase in fluorescence counts, whereas other steroids, such as progesterone, testosterone, and cortisol, did not affect fluorescence. Heat treatment of urine samples with hydrochloric acid significantly increased the fluorescence counts in those collected after the second trimester of gestation compared to non-pregnant samples, implying the presence of large amounts of conjugated estrogens in pregnant mare urine. Fluorescence counts in urine samples obtained during pregnancy showed a positive relationship with estrone concentrations as measured by enzyme immunoassay. The results of the present study showed that the fluorometric Cuboni test facilitates urine fluorescence counts depending on the urinary estrogen content and is capable of discriminating between pregnancy and non-pregnancy states beyond the second trimester of gestation in mares.

Effects of repeated etching cycles using 15% hydrochloric acid on enamel loss and relative attenuation coefficient in resin infiltration.

BACKGROUND: Resin infiltration is used to mask enamel opacities and the recommended etching cycles are three. However, anecdotal evidence suggests that favorable esthetics outcomes can be obtained by increasing the etching cycles. AIM: To determine the incremental and total enamel loss when enamel surfaces are exposed to multiple etching cycles and to assess the relative attenuation coefficient after multiple etching cycles and resin infiltration treatment. METHODS: Ninety extracted sound human premolars teeth were divided into 9 groups (n = 10); with each consecutive group having one additional etching cycle up to 9 cycles. The teeth were scanned with optical coherence tomography and enamel loss and attenuation coefficient were measured with MATLAB software. Enamel loss (one-way ANOVA, p ≤ 0.05) and attenuation coefficient (two-way ANOVA, p ≤ 0.05) were statistically analyzed. RESULTS: There was a significant total enamel loss of more than 33% found at the 7th etching cycle and more. There was no statistically significant difference in the incremental mean depth of penetration of resin between various etching cycles (F(8, 134) = [2.016], one-way ANOVA, p = 0.185). CONCLUSION: This study recommends that etching should not be repeated more than seven cycles to prevent excessive enamel loss. Following eight etching cycles, resin infiltration penetration appears approximately equal to that of healthy enamel.

VALOR-CKD: A Multicenter, Randomized, Double-Blind Placebo-Controlled Trial Evaluating Veverimer in Slowing Progression of CKD in Patients with Metabolic Acidosis.

SIGNIFICANCE STATEMENT: Metabolic acidosis is a common complication of CKD and is associated with more rapid decline of kidney function, but well-powered controlled randomized trials testing the effect of treating metabolic acidosis on slowing CKD progression have not been conducted. The VALOR-CKD study randomized 1480 individuals with CKD and metabolic acidosis, across 320 sites to placebo or veverimer (a novel hydrochloric acid binder). The findings did not demonstrate the efficacy of veverimer in slowing CKD progression, but the difference in serum bicarbonate between placebo and drug arms was only approximately 1 mEq/L. Veverimer was safe and well tolerated. BACKGROUND: Metabolic acidosis is common in CKD, but whether its treatment slows CKD progression is unknown. Veverimer, a novel hydrochloric acid binder that removes acid from the gastrointestinal tract, leads to an increase in serum bicarbonate. METHODS: In a phase 3, double-blind, placebo-controlled trial, patients with CKD (eGFR of 20-40 ml/min per 1.73 m 2 ) and metabolic acidosis (serum bicarbonate of 12-20 mEq/L) from 35 countries were randomized to veverimer or placebo. The primary outcome was the composite end point of CKD progression, defined as the development of ESKD (kidney transplantation or maintenance dialysis), a sustained decline in eGFR of ≥40% from baseline, or death due to kidney failure. RESULTS: The mean (±SD) baseline eGFR was 29.2±6.3 ml/min per 1.73 m 2 , and serum bicarbonate was 17.5±1.4 mEq/L; this increased to 23.4±2.0 mEq/L after the active treatment run-in. After randomized withdrawal, the mean serum bicarbonate was 22.0±3.0 mEq/L and 20.9±3.3 mEq/L in the veverimer and placebo groups at month 3, and this approximately 1 mEq/L difference remained stable for the first 24 months. A primary end point event occurred in 149/741 and 148/739 patients in the veverimer and placebo groups, respectively (hazard ratio, 0.99; 95% confidence interval, 0.8 to 1.2; P = 0.90). Serious and overall adverse event incidence did not differ between the groups. CONCLUSIONS: Among patients with CKD and metabolic acidosis, treatment with veverimer did not slow CKD progression. The lower than expected bicarbonate separation may have hindered the ability to test the hypothesis. CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER: VALOR-CKD, NCT03710291 .

Rice husk hydrochar prepared by hydrochloric acid assisted hydrothermal carbonization for levofloxacin removal in bioretention columns.

Hydrochars are promising adsorbents in pollutant removal for water treatment. Herein, hydrochloric acid (HCl) co-hydrothermally treated hydrochars were prepared from rice husk biomass at 180 °C via a one-step hydrothermal method. Adsorption behaviors of levofloxacin (LVX) on hydrochars were evaluated. The specific surface area and pore volume of the hydrochar synthesized in 5 mol/L HCl (5H-HC) were almost 17 and 8 times of untreated hydrochar, respectively. The 5H-HC sample exhibited the highest LVX adsorption capability at room temperature (107 mg/g). Thermodynamic experimental results revealed that adsorption was a spontaneous endothermic process. Yan model provided the best description of the breakthrough behavior of LVX in bioretention column, indicating that the adsorption on the samples involved several rate-limiting factors including diffusion and mass transfer. The results show that facile HCl co-hydrothermal carbonization of waste biomass can produce novel hydrochars with high LVX adsorption ability.

Effect of white jade snail secretion on antioxidant capacity and intestinal microbial diversity in mouse model of acute gastric ulcer.

BACKGROUND: In the present work, acute gastric ulcer models were constructed by administering hydrochloric acid/ethanol. The mice ingested white jade snail secretion (WJSS) through gastric infusion. Ulcer areas in gastric tissue were recorded, and malondialdehyde (MDA) and superoxide dismutase (SOD) were also measured. Notably, high-throughput 16S rDNA analysis of intestinal flora and determination of amino acid composition in feces were performed to understand the effect of WJSS on model mice. RESULTS: Compared with the control group, the ulcer area in the WJSS low-, medium- and high-concentration groups declined by 28.02%, 39.57% and 77.85%, respectively. MDA content decreased by 24.71%, 49.58% and 64.25%, and SOD relative enzyme activity fell by 28.19%, 43.37% and 9.60%, respectively. The amounts of amino acids in the low-, medium- and high-concentration groups were slightly lower, and probiotic bacteria such as Bacteroidetes and Lactobacillales increased in different-concentration WJSS groups. Adding WJSS contributes to the establishment of beneficial intestinal flora and the absorption of amino acids. CONCLUSION: Our results showed that WJSS has a beneficial effect on inhibiting hydrochloric acid-ethanolic gastric ulcers, suggesting that WJSS has excellent potential as a novel anti-ulcer agent. Combined with ulcer area, MDA content, SOD content, gut probiotics and other indicators, a high concentration of WJSS had the best protective effect on acute gastric ulcer. © 2023 Society of Chemical Industry.

Effect of hydrochloric acid and citric acid with ultrasound processing on characteristics of superfine-ground pectic polysaccharides from okra (Abelmoschus esculentus L.) peel.

The structural properties and biological activities of okra pectic polysaccharides (OPs) were impacted by various extraction methods. Based on commonly grinding (40, 100 meshes) and superfine grinding okra powders, two extraction solvents (hydrochloric acid, HA; citric acid, CA) were used firstly. Next, the extraction yield, physical and chemical properties, molecular structure and functional properties of OPs were analyzed by non-ultrasonic treatment and ultrasound-assisted superfine grinding method. The outcomes demonstrated that the extraction yield of OPs rose as the particle size of the powder decreased. HA-OPs had higher molecular weight (Mw), apparent viscosity and emulsification ability than CA-OPs. CA-OPs had higher esterification degree (DE), solubility and total sugar content, and higher amounts of rhamnogalacturonan-I (RG-I) segments. Compared with OPs without ultrasound-assisted extraction, ultrasound-assisted superfine grinding extraction exhibited higher sugar content, antioxidant capacity, emulsification ability, lower Mw, DE and apparent viscosity. Finally, the correlation between structure and function of OPs was further quantified. The antioxidant capacity was positively correlated with RG-I content, and negatively correlated with DE and Mw. The emulsification ability was mainly positively correlated with the GlcA of OPs. This study provides a theoretical basis for the development of OPs foods with clear structure-function relationship, which would be instructive for the application of OPs in food and cosmetics.

[Determination of furosine in liquid milk by high performance liquid chromatography-quadrupole time-of-flight mass spectrometry].

Furosine is often used both domestically and internationally as an indicator of the degree of heating to evaluate milk quality. However, in actual detection, the complexity of the milk matrix may lead to the inaccurate quantification of furosine in liquid milk. Therefore, in this study, an efficient and accurate method based on high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (HPLC-Q-TOF/MS) was established to determine furosine in liquid milk. A 2.00 mL milk sample was hydrolyzed with 5 mL 12.00 mol/L hydrochloric acid solution and 1 mL water at 110 ℃ for 12 h. After hydrolysis, vortex-mixing and filtration were performed. The filtrate was diluted six times with 6.00 g/L ammonium acetate solution and then analyzed. Gradient elution was performed with 0.20% formic acid aqueous solution and acetonitrile solution as mobile phases, followed by chromatographic separation on an AQ-C18 column (150 mm×3.5 mm, 5 µm). The data were collected by Q-TOF/MS with an electrospray ionization source operated in positive-ion mode. The accuracy of the quantification of furosine in milk was assessed by investigating the effects of the hydrochloric acid concentration (0.30, 1.25, and 3.00 mol/L) in the furosine solution on the MS response. The results showed that high hydrochloric acid concentrations inhibited the response signals. A good linear relationship was obtained in the mass concentration range of 0.05-2.00 mg/L, with a correlation coefficient (r) of 0.994. The limit of detection of the method was 0.50 mg/100 g, which meets the requirements of actual sample detection. The average recoveries of furosine ranged from 79.9% to 119.7% at three spiked levels of 1.52, 3.03, and 15.17 mg/100 g, with relative standard deviations of 1.4%-2.6%. The method was applied to detect 303 samples from 101 batches of pasteurized milk sold in the market, and the contents of furosine in these samples ranged from 5.1 to 11.9 mg/100 g. The proposed method is characterized with high efficiency, recovery, sensitivity, and accuracy. Thus, it can be used for the determination of large quantities of samples and provides technical support for the continuous promotion of the high-quality development of the whole dairy industry chain.

Erosion behaviour of human, bovine and equine dental hard tissues.

Dental hard tissues from different species are used in dental research, but little is known about their comparability. The aim of this study was to compare the erosive behaviour of dental hard tissues (enamel, dentin) obtained from human, bovine and equine teeth. In addition, the protective effect of the pellicle on each hard tissue under erosive conditions was determined. In situ pellicle formation was performed for 30 min on enamel and dentin samples from all species in four subjects. Calcium and phosphate release was assessed during 120 s of HCl incubation on both native and pellicle-covered enamel and dentin samples. SEM and TEM were used to examine surface changes in native enamel and dentin samples after acid incubation and the ultrastructure of the pellicle before and after erosive exposure. In general, bovine enamel and dentin showed the highest degree of erosion after acid exposure compared to human and equine samples. Erosion of human primary enamel tended to be higher than that of permanent teeth, whereas dentin showed the opposite behaviour. SEM showed that eroded equine dentin appeared more irregular than human or bovine dentin. TEM studies showed that primary enamel appeared to be most susceptible to erosion.