Detection Of Acid Research Articles

Development of acidochromic colloidal polymer nanoparticles containing azobenzene derivatives as eco-friendly time-dependent anticounterfeiting inks

N,N-dihydroxyethyl azobenzene compounds with different functional groups of hydrogen, electron-donating hydroxyl (OH), and electron-withdrawing nitro (NO2) were synthesized by a two-step diazotization and coupling method. Colloidal poly(methyl methacrylate) (PMMA) nanoparticles, prepared by emulsifier-free emulsion polymerization, were doped with 3 wt% of the three azobenzenes to prepare acidochromic colloids. Acidochromic properties of all the azobenzenes and the polymer colloids were investigated in acidic buffers. Azobenzene compounds doped on polymer particles showed different colors in buffers with different pH values due to the presence of different functional groups, which makes them highly applicable as acid detectors. The electron-withdrawing NO2 functional group caused a small bathochromic shift in the azobenzene spectrum, and the azobenzene containing OH functional group showed higher bathochromic shift than the unsubstituted azobenzene. The colloidal PMMA nanoparticles doped with the three azobenzene compounds were used as eco-friendly inks for stamping and hand-signing on cellulosic papers. Exposure to acidic HCl vapor resulted in different coloration of the printed marks due to the protonation of the azobenzenes. These colors of the protonated forms were decayed with time and also after exposure to triethylamine vapor. The stamped patterns showed a high fatigue and no change in color intensity up to 20 cycles. This shows that these polymeric inks can be used as anticounterfeiting inks for security-marking of confidential documents and banknotes. The developed inks showed time-dependent characteristics and responsivity to acid and base vapors, which make them highly applicable in security marking of confidential documents and also detection of acid and base.

A unique AIE multi-responsive half-salamo-like fluorescence sensor for temperature, pH and Cu2+/S2- ions in aqueous media

A novel multi-stimulus responsive small molecule fluorescent sensor DHS was developed. DHS with solvent-dependent properties exhibited active AIE effects, which is rare in salamo-like compounds. DHS has an excellent reversible thermal response and pH fluorescence response under various external stimuli (temperature and acid-base conditions). The response mechanism is supported by relevant studies and theoretical calculations. In addition, DHS can be used as a highly selective and sensitive fluorescent probe for the sequential detection of Cu2+ and S2– in water. DHS exhibits very prominent detection limit (48.59 nM) for Cu2+, which is superior to most small molecule fluorescent sensors of the same type. The experiments showed that the sensor DHS can be used for the ions detection in portable test strips and actual water samples. This study reveals a new strategy for the construction of salamo-like compounds with AIE properties, which can be beneficial for research in the fields of temperature sensing, acidity detection and ion recognition.

Dual-Response Photofunctional Covalent Organic Framework for Acid Detection in Various Solutions

The detection of acid in different solution environments plays a significant role in chemical, environmental and biological fields. However, reducing the constraints of detecting environment, such as aqueous, organic solvents and mixed phases of aqueous and organic phases, remains a challenge. Herein, by combining N, N, N′, N′-tetrakis(4-aminophenyl)-1,4-phenylenediamine (TPBD) and terephthalaldehyde (TA) via Shiff-base condensation, we constructed a covalent organic framework (COF) TPBD-TA COF. The COF exhibits color change from red to dark red as well as fluorescence quenching with the increase of acid contents in either aqueous or organic solvents, or a mixture of aqueous and organic solvents, due to the weak donor-acceptor interactions within the COF as well as the weak proton ionization ability of the solutions. Therefore, regardless of the detection environment, TPBD-TA COF can realize color and fluorescence dual-response to acid with the detection limit as low as 0.4 μmol/L and 58 nmol/L, respectively, due to the protonation of the nitrogen atoms on imine bonds of the COF.

Production of high-affinity monoclonal antibody and development of immunoassay for 3-methyl-quinoxaline-2-carboxylic acid detection in swine muscle and liver

Production of high-affinity and specific antibodies to small molecules with molecular weight (MW) lower than 200 Da is challenging. Here, we designed a novel hapten, named hapten H6, for the detection of 3-methyl-quinoxaline-2-carboxylic acid (MQCA, MW of 189 Da), a residual marker of olaquindox, one of important veterinary antibiotics. The hapten H6 maintained all structural features of MQCA, especially in mulliken atomic charge distribution. Then, a monoclonal antibody (mAb) named 8C9 was obtained with an IC50 value of 0.2 µg/L, yielding a 15.5- to 88.5-fold improvement compared to previously prepared specific antibodies against MQCA. In addition, mAb 8C9 exhibited ignorable cross-reactivity with other structural analogs. Finally, a highly sensitive and specific indirect competitive ELISA based on mAb 8C9 was developed for the detection of MQCA in swine muscle and liver samples with limit of detection values of 0.04 µg/kg and 0.09 µg/kg, respectively.

Exploration on Solvatochromic Sensing Probe of Phenol Blue for L‐Lactic Acid Detection: Effective Strategy to Obtain Reliable Capacitive Sensor

Exploration on Solvatochromic Sensing Probe of Phenol Blue for L‐Lactic Acid Detection: Effective Strategy to Obtain Reliable Capacitive Sensor

Exploration on Solvatochromic Sensing Probe of Phenol Blue for L‐Lactic Acid Detection: Effective Strategy to Obtain Reliable Capacitive Sensor

AbstractThis study systematically investigates a capacitive sensor applied with phenol blue (PhB)‐based sensing medium for detection of L‐lactic acid (LA), as a health monitoring indicator. PhB is a substance with solvatochromic effect, inducing the change in capacitance by exposure to polar molecules. However, the capacitive LA sensor with a flat‐structured PhB/polyvinylchloride (PVC) composite‐sensing medium is observed to have a problem in that sensing capacitance variation saturate quickly with increasing the LA solution concentration. This main cause can be analyzed that the interaction of proton from LA molecule with the lone pair electrons of the PhB molecule acts as a major factor on the sensing characteristics rather than the solvatochromic behavior of PhB molecule. Therefore, a strategy is adopted to introduce a porous structure to the PhB/PVC composite‐sensing medium to maximize the interaction of PhB with protons, which is implemented through solvent and non‐solvent exchange methods. Consequently, the sensitivity and linearity of the porous‐structured LA sensor are 2.99 pF mm−1 and 0.966 over LA concentrations ranging from 0 to 100 mm, respectively, which is a significant improvement over that of the flat‐structured one. Notably, the sensing performance remained unchanged even after a month of storage under normal ambient conditions.

Molecularly imprinted core-shell Au nanoparticles for 2,4-dichlorophenoxyacetic acid detection in milk using surface-enhanced Raman spectroscopy

Surface-enhanced Raman spectroscopy (SERS) has been extensively investigated for rapid and sensitive detection of trace level chemical contaminants in foods. Lack of selectivity to the targeted molecules in food matrices and fairly poor spectral reproducibility remain the main challenges for practical SERS applications. Herein, an ingenious strategy was proposed to hybridize molecularly imprinted polymers (MIPs) with gold nanoparticles as the functional SERS substrate for selective separation and detection of 2,4-dichlorophenoxyacetic acid (2,4-D), a systemic herbicide that has acute toxicity and potential cancer risk. The core-shell AuNPs@MIPs nanoparticles were finely tailored by wrapping an ultrathin layer of MIPs shell on the surface of AuNPs, which allowed selectively separating and enriching 2,4-D to the near surface of AuNPs and ensured the enhancement of Raman scattering signal of the analyte. Embedding an internal standard (i.e., 4-aminothiophenol) inside AuNPs@MIPs for SERS spectral calibration improved the quantification accuracy for 2,4-D. Three-dimensional finite difference time domain (3D-FDTD) simulation demonstrated the maximal electric field enhancement presented in the gap between adjacent AuNPs@MIPs with the theoretical enhancement factor (EF) as high as 5.85 × 106. Chemometric models established using SERS spectra showed accurate differentiation and quantification results for 2,4-D in milk at various contamination levels with a limit of detection (LOD) of 0.011 μg/mL. Our approach to integrate MIPs with noble metallic nanoparticles has great potential for selective and quantitative detection of analytes using SERS for practical agri-food analysis.

Electrochemical Sensor Based on Carbon-Incorporated WSe2 Nanosheets for Simultaneous Detection of Ascorbic Acid, Dopamine, and Uric Acid

The development of sensitive and selective electrodes for electrochemical detection of ascorbic acid (AA), dopamine (DA) and uric acid (UA) is essential for early diagnosis and effective treatment. In this work, a nanocomposite of two-dimensional WSe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> nanosheets with carbon black (WSe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> @C) was prepared by facile hydrothermal method and used to modify a glassy carbon electrode (GCE) to fabricate an electrochemical sensing platform for simultaneous determination of AA, DA and UA. The as-prepared nanocomposite was characterized in terms of structural and morphological analyses through X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The electrochemical and electrocatalytic behaviors of the modified electrode (GCE-WSe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> @C) were investigated using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The sensing performance of GCE-WSe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> @C electrode was tested against AA, DA and UA, resulting in enhanced electrocatalytic properties compared to GCE-WSe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and GCE-C electrodes. The GCE-WSe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> @C electrode displayed wide linear ranges of 8.0 - <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2456 \mu \text{M}$ </tex-math></inline-formula> for AA, 1.0 - 49.0 & 72.8 - <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$381.4 \mu \text{M}$ </tex-math></inline-formula> for DA and 1.0– 24.8 & 36.9– <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$185.2 \mu \text{M}$ </tex-math></inline-formula> for UA with low detection limits of 3.2, 0.18 and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.42 \mu \text{M}$ </tex-math></inline-formula> , respectively. In addition, the developed electrode demonstrated high reproducibility and stability for electrochemical detection of AA, DA and UA.

Electrochemical detection of uric acid in undiluted human saliva using uricase paper integrated electrodes

In this study, we introduce a uricase-immobilized paper (UOx­-paper) integrated electrochemical sensor for detection of uric acid (UA) in saliva. The UOx was immobilized on the detection zone in the wax-patterned paper substrate. This UOx-paper was integrated with a Prussian blue­-modified, screen-printed carbon electrode after electropolymerization of o-phenylenediamine to construct an electrochemical cell for small-volume (20 μL) of samples. First, we optimized the fabrication conditions of UOx-paper. Next, the amperometric response of the UOx-paper-based electrochemical UA sensor was analyzed using a known concentration of UA standard solution in artificial saliva at an applied potential of − 0.1 V (versus Ag pseudo-reference electrode). The UOx-­paper based electrochemical UA sensor showed a sensitivity of 4.9 μA·mM−1 in a linear range of 50 to 1000 μM (R2 = 0.998), high selectivity and good reproducibility, as well as a limit of detection of 18.7 μM (0.31 mg/dL) UA. Finally, we quantified the UA levels in undiluted saliva samples of healthy controls (n = 20) and gout patients (n = 8). The levels were correlated with those measured with conventional salivary UA enzymatic assays as well as serum UA levels. The UOx-paper-based electrochemical UA sensor is a user-friendly and convenient tool to assess salivary UA levels.

Advanced Technologies in On-Site Detection of Genetically Modified Products

Transgenic technology is significantly impacting life today. However, with the advancement of genetically modified technologies and the success of genetically modified product commercialization, new challenges have arisen for associated detecting technologies. The need for fast, precise, and portable systems for the on-site detection of genetically modified products has increased dramatically in recent years. This perspective examined the currently available technological support for portable immune biosensing, discussed a portable detection device for ultrafast PCR, and an on-site detection biosensor based on functional nucleic acid and superior detection devices in the field. Moreover, the on-site sequencing of genetically modified organisms was mentioned briefly. Lastly, the future outlook of genetically modified products detection was concluded and discussed in order to provide a comprehensive reference for future research and development in related fields.

Derivative Matrix-Isopotential Synchronous Spectrofluorimetry and Hantzsch Reaction: A Direct Route to Simultaneous Determination of Urinary δ-Aminolevulinic Acid and Porphobilinogen.

Early and sensitive detection of δ-aminolevulinic acid (δ-ALA) and porphobilinogen (PBG) is the cornerstone of diagnosis and effective treatment for acute porphyria. However, at present, the quantifying strategies demand multiple solvent extraction steps or chromatographic approaches to separate δ-ALA and PBG prior to quantification. These methods are both time-consuming and laborious. Otherwise, in conventional spectrofluorimetry, the overlapping spectra of the two analytes cause false diagnosis. To overcome this challenge, we present a two-step approach based on derivative matrix-isopotential synchronous fluorescence spectrometry (DMISFS) and the Hantzsch reaction, realizing the simple and simultaneous detection of δ-ALA and PBG in urine samples. The first step is chemical derivatization of the analytes by Hantzsch reaction. The second step is the determination of the target analytes by combining MISFS and the first derivative technique. The proposed approach accomplishes following advantages: 1) The MISFS technique improves the spectral resolution and resolves severe spectral overlap of the analytes, alleviating tedious and complicated pre-separation processes; 2) First derivative technique removes the background interference of δ-ALA on PBG and vice versa, ensuring high sensitivity; 3) Both the analytes can be determined simultaneously via single scanning, enabling rapid detection. The obtained detection limits for δ-ALA and PBG were 0.04 μmol L−1 and 0.3 μmol L−1, respectively. Within-run precisions (intra and inter-day CVs) for both the analytes were <5%. Further, this study would serve to enhance the availability of early and reliable quantitative diagnosis for acute porphyria in both scientific and clinical laboratories.

Direct In Vivo Analysis of CBD- and THC-Acid Cannabinoids and Classification of Cannabis Cultivars Using SpiderMass

In recent years, cannabis and hemp-based products have become increasingly popular for recreational use, edibles, beverages, health care products, and medicines. The rapid detection and differentiation of phytocannabinoids is, therefore, essential to assess the potency and the therapeutic and nutritional values of cannabis cultivars. Here, we implemented SpiderMass technology for in vivo detection of cannabidiolic acid (CBDA) and ∆9-tetrahydrocannabinolicacid (∆9-THCA), and other endogenous organic plant compounds, to access distribution gradients within the plants and differentiate between cultivars. The SpiderMass system is composed of an IR-laser handheld microsampling probe connected to a mass spectrometer through a transfer tube. The analysis was performed on different plant organs from freshly cultivated cannabis plants in only a few seconds. SpiderMass analysis easily discriminated the two acid phytocannabinoid isomers via MS/MS, and the built statistical models differentiated between four cannabis cultivars. Different abundancies of the two acid phytocannabinoids were found along the plant as well as between different cultivars. Overall, these results introduce direct analysis by SpiderMass as a compelling analytical alternative for rapid hemp analysis.

Quantitative Detection of Amino Acids and Carnitine in Human Blood and Quality Control of Peptide Drugs

In order to deal with the biochemical metabolic disorder and the lack of end metabolites caused by hereditary metabolic diseases, a quantitative detection method of amino acids and carnitine in human blood and the quality control method of polypeptide drugs were proposed. First, a method for the detection of 10 amino acids and 32 acylcarnitine metabolites in human blood was established and analyzed by liquid chromatography tandem mass spectrometry. Through the experimental research on typical peptide drugs, combined with the classical synthesis process and the PLS-DA model of human body in different regions, the relevant detection methods for the quality control of peptide drugs were established, which provided a reference for the formulation of peptide drug quality standards. The experimental results show that the quantitative detection method proposed in this paper can effectively detect the content of most amino acids and acylcarnitine. The classical detection method achieved a loss of 16.74% smaller mass-to-charge ratio, and based on this, the quantitative standard for polypeptide drug delivery was determined, which verifies the correctness and superiority of the detection method in this paper.

A New Phenylazo-Based Fluorescent Probe for Sensitive Detection of Hypochlorous Acid in Aqueous Solution.

In this paper, we designed and synthesized a novel phenylazo-based fluorescent probe (RHN) for the sensing and imaging of hypochlorous acid (HClO) in mitochondria in living cells. In this process, HClO promoted the oxidation of the phenylazo group to generate a free Rhodol fluorophore moiety, which in turn restored strong fluorescence and realized the detection of HClO. As expected, RHN exhibited high selectivity, high sensitivity and rapid response, with detection limits as low as 22 nM (1.155 ng/mL). Importantly, the results of the cell imaging experiments indicated that RHN has the ability to image and sense HClO in mitochondria, which is of great significance for exploration of the specific role of HClO in both the immune system and diseases.

A Fluorescence Immunochromatographic Strip Based on Quantum Dot Nanobeads for the Rapid Detection of Okadaic Acid

A Fluorescence Immunochromatographic Strip Based on Quantum Dot Nanobeads for the Rapid Detection of Okadaic Acid

Development of a highly efficient virus-free regeneration system of Salvia miltiorrhiza from Sichuan using apical meristem as explants

BcakgroundThe dry root and rhizome of Salvia miltiorrhiza are used to treat cardiovascular diseases, chronic pain, and thoracic obstruction over 2000 years in Asian countries. For high quality, Sichuan Zhongjiang is regarded as the genuine producing area of S. miltiorrhiza. Given its abnormal pollen development, S. miltiorrhiza from Sichuan (S.m.-SC) relies on root reproduction and zymad accumulation; part of diseased plants present typical viral disease symptoms and seed quality degeneration. This study aim to detected unknown viruses from mosaic-diseased plants and establish a highly efficient virus-free regeneration system to recover germplasm properties.ResultsTobacco mosaic virus (TMV) and cucumber mosaic virus (CMV) were detected from mosaic-diseased plants. Primary apical meristem with two phyllo podium in 0.15–0.5 mm peeled from diseased plants were achieved 73.33% virus-free rate. The results showed that the medium containing MS, 0.5 mg/L 6-BA, 0.1 mg/L NAA, 0.1 mg/L GA3, 30 g/L sucrose and 7.5 g/L agar can achieve embryonic-tissue (apical meristem, petiole and leaf callus) high efficient organogenesis. For callus induction, the optimal condition was detected on the medium containing MS, 2 mg/L TDZ, 0.1 mg/L NAA by using secondary petiole of virus-free plants under 24 h dark/d condition for 21 d. The optimal system for root induction was the nutrient solution with 1/2 MS supplemented with 1 mg/L NAA. After transplant, the detection of agronomic metric and salvianolic acid B content confirmed the great germplasm properties of S.m.-SC virus-free plants.ConclusionsA highly efficient virus-free regeneration system of S.m.-SC was established based on the detected viruses to recover superior seed quality. The proposed system laid support to control disease spread, recover good germplasm properties in S.m.-SC.

Droplet Digital PCR (ddPCR) Analysis for Detecting Shiga-Toxin-Producing Escherichia coli (STEC)

Verocytotoxin-producing Escherichia coli, also referred to as Shiga-toxin-producing Escherichia coli (STEC), can be transmitted to humans through person-to-person contact, consumption of contaminated food or water, or by direct contact with animals. Its clinical and economic consequences have prompted the development of alternative approaches to the official method of analysis “UNI CEN ISO/TS 13136: 2012”, which describes the identification of STEC through the detection of its main virulence genes. Recently, droplet digital PCR (ddPCR) has been proposed as a technique for the sequence-specific detection and direct quantification of nucleic acids. The present study aimed to investigate if ddPCR could be able to detect STEC in less time than that required by the official method. This study consisted of the ddPCR of slices of beef contaminated with STEC and of the sponges used for beef official control at the slaughter stage. The results showed the ability of ddPCR to detect STEC in slices of beef already after sample incubation for 7 h at 37 °C while, in the case of sponges used for official controls, 9 h at 37 °C was needed. In this way, the ddPCR could represent an efficient method for detecting STEC and providing results in less time than the official method.

Swab test in biological fluids as predictor of COVID-19 transmission risk during surgery: a prospective cross-sectional study from an Italian COVID center

BackgroundThe contamination of body fluids by Severe Acute Respiratory Syndrome Coronavirus 2 during surgery is current matter of debate in the scientific literature concerning CoronaVIrus Disease 2019. Surgical guidelines were published during the first wave of the COVID-19 pandemic and recommended to avoid laparoscopic surgery as much as possible, in fear that the chimney effect of high flow intraperitoneal gas escape during, and after, the procedure would increase the risk of viral transmission.AimThe aim of this study was to evaluate the possibility of SARS-CoV-2 transmission during surgery by searching for viral RNA in serial samplings of biological liquids.MethodsThis is a single center prospective cross-sectional study. We used a real-time reverse transcriptase (RT) polymerase chain reaction (PCR) test to perform swab tests for the qualitative detection of nucleic acid from SARS-CoV-2 in abdominal fluids, during emergency surgery and on the first post-operative day. In the case of thoracic surgery, we performed a swab test of pleural fluids during chest drainage placement as well as on the first post-operative day.ResultsA total of 20 samples were obtained: 5 from pleural fluids, 13 from peritoneal fluids and two from biliary fluid. All 20 swabs performed from biological fluids resulted negative for SARS-CoV-2 RNA detection.ConclusionTo date, there is no scientific evidence of possible contagion by laparoscopic aerosolization of SARS-CoV-2, neither is certain whether the virus is effectively present in biological fluids.

Simultaneous determination of four organic acids in beverages by capillary electrophoresis coupled with ultraviolet detector

A simple and rapid capillary electrophoresis method with direct ultraviolet (UV)&amp;nbsp;detection was set up for the determination of four organic acids in beverages. The method&amp;nbsp;included dilution and filtration as simple sample preparation steps. The electrophoretic&amp;nbsp;separation and detection of oxalic, malic, citric and lactic acids in wines and beers were&amp;nbsp;performed in 8 min. For the method validation, linearity, detection and quantification limits,&amp;nbsp;repeatability and recovery in wine and beer matrices were studied. Good linearity was&amp;nbsp;observed from 25 to 500 mg/L for all acids excluding lactic acid, for which it started from&amp;nbsp;50 mg/L. The limits of quantitation of oxalic, malonic and citric acid were set 9.5 to 28.5&amp;nbsp;mg/L. Repeatability of this method was from 3.2 to 7.3%, recoveries ranged from 90.1 to&amp;nbsp;110.1%. The validated method was applied to the analysis of different wines and beers and&amp;nbsp;showed great variability in their composition.

Adult acute respiratory distress syndrome due to human parvovirus B19 infection after cardiac surgery: a case report

BackgroundInfection with human parvovirus B19 (PB19) is very common in pediatric patients. Symptoms and signs depend on the infected patient’s immune and hematopoietic status and can range from an asymptomatic condition to life-threatening disease.Case presentationA 69-year-old man received elective mitral valvular replacement and tricuspid valvuloplasty under cardiopulmonary bypass and suffered acute respiratory distress syndrome on postoperative day 8. Through the detection of positive serum IgM and human PB19-specific nucleic acids in serum and bronchoalveolar lavage fluid via metagenomic next-generation sequencing (mNGS), acute human PB19 infection was confirmed. The patient was ventilated and the pulmonary infiltration was attenuated six days later.ConclusionA combination of serum human PB19 DNA by mNGS and positive serum human PB19 IgM could provide higher diagnostic sensitivity for acute human PB19 infection. The method of mNGS may be a new choice for detecting rare or atypical pathogens in severe complicated pneumonia. The infection of human PB19 was possibly self-limited.