Relative Detection Limits Research Articles

Silicon quantum dots based fluorescent probes for detecting methyl parathion pesticide residues in potato, tap water and Yellow River

In this paper, a novel ratiometric fluorescent probe based on silicon quantum dots (SiQDs) has been developed for the sensitive detection of methyl parathion pesticide residues. The silicon quantum dots were prepared by a simple hydrothermal reaction process using 3-Aminopropyltriethoxysilane (APTES) as silicon resource and were characterized by the analysis of transmission electron microscopy, FTIR spectroscopy, and X-ray photoelectron spectroscopy. The silicon quantum dots displayed characteristic blue fluorescence emission at 440 nm. Tyrosinase can catalyze the oxidation of tyramine to form dopamine. Then, dopamine can interact with silicon quantum dots and effectively change the position of its fluorescence emission for redshiftting to 540 nm. In the presence of organic phosphorus pesticides (OPPs), the activity of tyrosinase was inhibited, resulting in the inability to generate dopamine and the fluorescence emission at 440 nm remaining unchanged. As a model of organic phosphorus pesticides, methyl parathion (MP) was determined using this method, and the fluorescence intensity response values showed a good linear relationship with methyl parathion concentration in the range of 50–90 nM, with a detection limit of 0.149 nM. Due to its good performance of relative low detection limit, good selectivity and high reproducibility, this sensing system has been successfully applied to the detection of methyl parathion in environmental water samples and potato samples, which showed good prospects for application in the detection of organic phosphorus pesticide residues in more real samples.

Qualitative detection of E. coli in distributed drinking water using real-time reverse transcription PCR targeting 16S rRNA: Validation and practical experiences

Escherichia coli (E. coli) plays a central role as an indicator for fecal contamination to predict the possible presence of microbial pathogens in drinking water. Current detection methods for E. coli are based on time-consuming culture-based techniques. There is a strong need for methods to detect fecal contamination rapidly in distributed drinking water to prevent outbreaks of waterborne disease and support water utilities to efficiently manage their operations like actions to repair or maintain distribution pipes, to minimize impact on consumers. This study describes the validation and application of a qualitative real time reverse transcription PCR (RT-PCR) method targeting 16S ribosomal RNA (rRNA) for rapid detection of E. coli in distributed drinking water. The RT-PCR assay targets 16S rRNA, a highly abundant RNA in viable cells, enabling robust detection at the required sensitivity of 1 CFU/100 ml. The validation was performed by comparing the RT-PCR method with the culture-based chromogenic reference method (CCA) using the protocol and criteria described in ISO 16,140–2:2016. The validation demonstrated that this RT-PCR method can be used to specifically detect E. coli in a broad range of drinking water samples with at least the same limit of detection as the culture method (Relative Limit Of Detection = 0.75, range 0.43–1.43). The inclusivity study showed that the RT-PCR method was able to detect a broad range of E. coli strains derived from different sources and geographic areas, including pathogenic serotype O157 strains that are not detected with the culture method. The exclusivity study determined that other bacterial genera are not detected with this RT-PCR. However, Escherichia fergusonii was detected and, based on “in silico” analysis, it is expected that also E. albertii and E. marmotae and Shigella species will be detectable using this RT-PCR. An interlaboratory study confirmed that the RT-PCR and culture method have comparable sensitivities when tested by different participants at different laboratories. The application of RT-PCR to confirm the hygienic quality of distributed drinking water after actions to repair or maintain distribution pipes was compared with the culture method on 8076 routine samples, analyzed by the drinking water laboratories in the Netherlands. This comparison study showed a 96.4 % agreement between RT-PCR and culture. In 3.3 % of the samples E. coli was detected with RT-PCR and not with the culture method and in 0.1 % of the samples E. coli was only detected by culture confirming either a higher sensitivity for RT-PCR or the detection of RNA from uncultivable cells. Finally, the application of RT-PCR was highlighted during a contamination event in Belgium where we demonstrate the potency of RT-PCR as a tool to rapidly monitor the spread of microbial contamination and to monitor the effect of measures to remove the contamination This is the first fully validated rapid nucleic based method for detection of E. coli in distributed drinking water. These results demonstrate that this RT-PCR method can be used as a rapid alternative to the culture method to monitor E. coli in distributed drinking water. However, it should be emphasized that nucleic acid based detection methods rely on highly different detection principles (detection of captured nucleic acids present in a sample) than culture base methods (presence of cells cultivable on a selective medium) resulting in occasional different analysis results. Varying treatment and disinfection steps (UV, chlorine, monochloramine, Ozone) or environmental factors (decay) can influence the results and cause differences between RT-PCR and culture methods.

Green DES based microextraction method for monitoring brilliant black BN (E151) in diverse food matrices

A green deep eutectic solvent (DES) based microextraction method was established for separation and spectrophotometric determination of E151 in food matrices. DES composed of tetra pentyl ammonium bromide and 1-octanol (1:5) was used. Important analytical microextraction parameters including pH, volume of DES and time of vortex mixing were optimized using Box-Behnken design of Response Surface Methodology. The other variables including composition ratio of DES and sample volume were optimized by one variable at a time optimization process. The method exhibited linear behaviour for E151 having concentration range between 132–12000 µg/L with 30 preconcentration factor. The relative standard deviation, detection limit and quantitation limit were determined to be 5 %, 40 and 132 µg/L, respectively. The scores of analytical greenness and applicability for the method were determined to be 0.69 and 62.5, respectively. pK values of E151 were determined. Extraction mechanisms of E151 were elucidated. The method was applied to foodstuffs and water samples to determine their E151 contents by analyte addition recovery tests with recovery values ranging between 94–103 %.

Evaluation of 5 Polymerase Chain Reaction Assays for the Detection of Mpox Virus.

In 2022, the global dissemination of mpox virus (MPXV) outside endemic regions prompted the expansion of diagnostic testing worldwide. This study assesses the performance characteristics of 5 real-time polymerase chain reaction (PCR) assays in detecting MPXV during the 2022 outbreak. Clinical specimens collected from patients across Ontario, Canada, were tested on the following assays: RealStar Orthopoxyvirus PCR and FlexStar Monkeypox virus PCR (Altona Diagnostics), Novaplex MPXV (Seegene), VIASURE Monkeypox virus Real Time PCR Reagents (CerTest Biotec), and a laboratory-developed test. Positive percent agreement (PPA), negative percent agreement (NPA), relative limit of detection (LOD), and precision were evaluated and MPXV lineages were determined using an amplicon-based whole-genome sequencing (WGS) assay. Swabs were collected from various anatomic sites (65 positive and 30 negative). All assays demonstrated 100% NPA (95% confidence interval, 88.4%/88.1%-100.0%), with PPA ranging from 92.2% (82.7%-97.4%) to 96.9% (89.3%-99.6%). LOD and precision were comparable across assays, with coefficient of variations <3%. WGS analysis identified 6 lineages, all belonging to subclade IIb. The assays exhibited excellent PPA, NPA, LOD, and precision. Ongoing performance monitoring is essential to detect assay escape mutants and ensure universal detection of evolving MPXV strains.

Deep-learning assisted zwitterionic magnetic immunochromatographic assays for multiplex diagnosis of biomarkers

Magnetic nanoparticle (MNP)-based immunochromatographic tests (ICTs) display long-term stability and an enhanced capability for multiplex biomarker detection, surpassing conventional gold nanoparticles (AuNPs) and fluorescence-based ICTs. In this study, we innovatively developed zwitterionic silica-coated MNPs (MNP@Si-Zwit/COOH) with outstanding antifouling capabilities and effectively utilised them for the simultaneous identification of the nucleocapsid protein (N protein) of the severe acute respiratory syndrome coronavirus (SARS-CoV-2) and influenza A/B. The carboxyl-functionalised MNPs with 10% zwitterionic ligands (MNP@Si-Zwit 10/COOH) exhibited a wide linear dynamic detection range and the most pronounced signal-to-noise ratio when used as probes in the ICT. The relative limit of detection (LOD) values were achieved in 12 min by using a magnetic assay reader (MAR), with values of 0.0062 ng/mL for SARS-CoV-2 and 0.0051 and 0.0147 ng/mL, respectively, for the N protein of influenza A and influenza B. By integrating computer vision and deep learning to enhance the image processing of immunoassay results for multiplex detection, a classification accuracy in the range of 0.9672–0.9936 was achieved for evaluating the three proteins at concentrations of 0, 0.1, 1, and 10 ng/mL. The proposed MNP-based ICT for the multiplex diagnosis of biomarkers holds substantial promise for applications in both medical institutions and self-administered diagnostic settings.

Determination of chromium in foodstuffs by using novel adsorbent in vortex assisted-dispersive solid phase micro-extraction method: An application of multivariate techniques

A new graft copolymer composed of polystyrene and polylinoleic acid (PLinas) with the sodium salt of iminodiacetate (Ida) was synthesized and used as an adsorbent. The vortex-assisted dispersive solid-phase micro-extraction (VA-dSPµE) method was used for the extraction and pre-concentration of chromium. Multivariate methodologies, such as factorial design and 3D surface plots, were applied for screening and optimizing effective extraction parameters. The influence of diverse analytical parameters, such as pH, sample volume, and interfering ions, on the extraction of chromium was studied. The calibration standard curve exhibited a linear range from 0.01 to 0.50 μg L−1. The relative standard deviation and limit of detection were found to be 1.65 % and 0.003 μg L−1, respectively. Extraction recoveries were found in the range of 96 to 99 % by using certified reference materials (CRMs). The adsorbent capacity of PLinas-Ida was found to be 112 mg g−1. The VA-dSPµE method demonstrated its effectiveness in the pre-concentration and determination of chromium within samples of foodstuffs by graphite furnace-atomic absorption spectrometry (GF-AAS).

Development of a loop-mediated isothermal amplification assay for the rapid detection of Styphnolobium japonicum (L.) Schott as an adulterant of Ginkgo biloba (L.)

BackgroundSpecies adulteration is a concern in herbal products, especially when plant substitutes of lower economic value replace valuable botanicals. Styphnolobium japonicum is well known as a potential adulterant of Ginkgo biloba, which is one of the most demanded medicinal plants due to its wide use in pharmaceuticals, food supplements, and traditional medicine. Despite bearing some resemblance to ginkgo's flavonol composition, S. japonicum lacks many of G. biloba's desired therapeutic properties. To prevent adulteration practices, it is crucial to implement rigorous quality control measures, including fast and simple diagnostic tools that can be used on-field. PurposeThis study aims to develop for the first time a species-specific loop-mediated isothermal amplification (LAMP) method for the fast identification of S. japonicum in ginkgo-containing products. MethodsA set of four specific primers (SjF3, SjB3, SjFIP, and SjBIP) and loop primers (SjLF and SjLB) were designed for a LAMP based assay using the 5.8S partial sequence and the internal transcribed spacer 2 of nuclear ribosomal DNA of S. japonicum. ResultsThe successful amplification of the LAMP assay was inspected through visual detection, with the highest intensity recorded at the optimal conditions set at 68 °C for 40 min. The primers showed high specificity and were able to accurately discriminate S. japonicum from G. biloba and 49 other species of medicinal plants. Furthermore, the proposed LAMP assay proved to be fast, selective, and highly sensitive, as demonstrated by the absolute and relative limits of detection, which were reached at 0.5 pg for S. japonicum DNA and 0.01 % S. japonicum in G. biloba, respectively. ConclusionsThis novel approach allows easy identification and discrimination of S. japonicum as a potential adulterant of G. biloba, thus being a useful tool for quality control. Compared to chromatographic or PCR-based methods, the assay proved to be fast, sensitive and did not require expensive equipment, thus offering the possibly usage in field analysis.

Comparison of two novel one-tube nested real-time qPCR assays to detect human-infecting Cyclospora spp.

Human-infecting Cyclospora spp. currently include three coccidian parasites that cause the gastrointestinal disease cyclosporiasis in humans. They are often spread through contaminated produce, including leafy greens and berries. The increased availability of sensitive molecular tests for the diagnosis of cyclosporiasis is an important advancement, allowing public health agencies to better understand the scope and source of cyclosporiasis outbreaks. To improve the diagnosis of infected patients, rapidly detect outbreaks, and keep the food supply safe, it is important to continue to develop sensitive, reliable, and inexpensive tests to detect human-infecting Cyclospora spp. In this report, we describe the development and evaluation of two novel one-tube nested qPCR assays for the detection of human-infecting Cyclospora spp. in clinical stool samples, one targeting cytb and the other targeting coxI. Of these, the assay targeting the cytb mitochondrial locus possessed strong performance characteristics compared to a routinely used 18S assay, including a markedly improved (approximately 10-fold lower) relative detection limit of 0.613 oocysts per gram of feces. This is compared to coxI that has a relative detection limit equal to that of the 18S assay. Given the strong performance characteristics of the cytb assay, we propose that it may be useful to diagnostic laboratories wishing to screen clinical fecal specimens suspected of containing human-infecting Cyclospora spp.IMPORTANCEHuman-infecting Cyclospora spp. cause gastrointestinal distress among healthy individuals contributing to morbidity and putting stress on the economics of countries and companies in the form of produce recalls. Accessible and easy-to-use diagnostic tools available to a wide variety of laboratories would aid in the early detection of possible outbreaks of cyclosporiasis. This, in turn, will assist in the timely traceback investigation to the suspected source of an outbreak by informing the smallest possible recall and protecting consumers from contaminated produce. This manuscript describes two novel detection methods with improved performance for the causative agents of cyclosporiasis when compared to the currently used 18S assay.

A microfluidic biosensor for the diagnosis of chronic wasting disease

Cervids are affected by a neurologic disease that is always fatal to individuals and has population effects. This disease is called chronic wasting disease (CWD) and is caused by a misfolded prion protein. The disease is transmitted via contact with contaminated body fluids and tissue or exposure to the environment, such as drinking water or food. Current CWD diagnosis depends on ELISA screening of cervid lymph nodes and subsequent immunohistochemistry (IHC) confirmation of ELISA-positive results. The disease has proven to be difficult to control in part because of sensitivity and specificity issues with the current test regimen. We have investigated an accurate, rapid, and low-cost microfluidic microelectromechanical system (MEMS) biosensing device for the detection of CWD pathologic prions in retropharyngeal lymph nodes (RLNs), which is the current standard type of CWD diagnostic sample. The device consists of three novel regions for concentrating, trapping, and detecting the prion. The detection region includes an array of electrodes coated with a monoclonal antibody against pathologic prions. The experimental conditions were optimized using an engineered prion control antigen. Testing could be completed in less than 1 hour with high sensitivity and selectivity. The biosensor detected the engineered prion antigen at a 1:24 dilution, while ELISA detected the same antigen at a 1:8 dilution. The relative limit of detection (rLOD) of the biosensor was a 1:1000 dilution of a known strong positive RLN sample, whereas ELISA showed a rLOD of 1:100 dilution. Thus, the biosensor was 10 times more sensitive than ELISA, which is the currently approved CWD diagnostic test. The biosensor’s specificity and selectivity were confirmed using known negative RPLN samples, a negative control antibody (monoclonal antibody against bovine coronavirus BCV), and two negative control antigens (bluetongue virus and Epizootic hemorrhagic disease virus). The biosensor’s ability to detect pathogenic prions was verified by testing proteinase-digested positive RLN samples.

Development and Validation of an Efficient Multiplex PCR Assay for Simultaneous Detection of Six Common Foodborne Pathogens and Hygiene Indicators.

Microbial contamination in foods could lead to illnesses and substantial losses in both food industry and public health sectors. Rapid detection of microbial hazards (i.e., pathogens, hygiene indicator microorganisms) can accelerate surveillance and diagnostic processes reducing transmission and minimizing undesirable consequences. This study developed a multiplex PCR (m-PCR) for the detection of six common foodborne pathogens and hygiene indicators using specific primers for uidA of Escherichia coli, stx2 of Escherichia coli O157:H7, invA of Salmonella spp., int of Shigella spp., ntrA of Klebsiella pneumoniae, and ail of Yersinia enterocolitica and Yersinia pseudotuberculosis. Sensitivity of the m-PCR was 100 fg or ∼20 bacterial cells. Each primer set amplified only the targeted strain, and specificity was demonstrated by lack of nonspecific bands with DNA from 12 other bacterial strains. Following ISO 16140-2:2016, the relative limit of detection of the m-PCR was comparable to that of the gold-standard method; however, the processing time was five times faster. The m-PCR was applied to detect the six pathogens in 100 natural samples (50 pork meat and 50 local fermented food samples) and compared to results of the gold-standard method. Positive cultures for Klebsiella, Salmonella, and E. coli were 66%, 82%, and 88%, respectively, of meat samples and 78%, 26%, and 56%, respectively, of fermented food samples. Escherichia coli O157:H7, Shigella, and Yersinia were not detected in any of the samples by both standard and m-PCR methods. The developed m-PCR assay showed comparable results with the traditional culture technique proving its rapid and reliable detection of six foodborne pathogens and hygiene indicators in food.

Differential detection of sheep and goat meat using duplex real-time PCR and high-resolution melt analysis

Authenticity in meat and meat products is of paramount importance in preventing adulteration and ensuring food safety. Since morphologically indistinct samples like sheep and goat meat requires accurate and sensitive differentiation, we developed and validated a duplex real-time polymerase chain reaction (qPCR) assay with high-resolution melt analysis (HRMA) for simultaneous identification of sheep and goat meat. Species-specific amplicons with melting temperature of 78 °C for goat and 80 °C for sheep (with associated standard errors) was identified. The assay was optimized for basic PCR parameters and the HRMA detection was standardized based on melt curve shape, color and inflexion points. The absolute limit of detection (LODabs) and limit of quantification (LOQ) of the assay were found to be 0.39 ng and 0.78 ng of target DNA respectively. A sensitivity of 0.1% was obtained for both sheep and goat meat. The relative limit of detection (LODrel) was also found to be 5%. The linearity and efficiency were evaluated in both simplex and duplex assays. The assay applicability was evaluated using proficiency test samples and commercially available raw and processed meat samples. The obtained results showed that this closed-tube qPCR-HRMA method can be a rapid and sensitive detection technique for meat speciation.

The porous hollow cobalt-based oxides encapsulated with bimetallic PdAu Nanoparticles of electrochemical biosensor for highly sensitive pesticides detection

Efficient and portable electrochemical biosensors are received to evaluation of pesticides in the environment, which can make great significance for food safety. In this study, the Co-based oxides with a kind of hierarchical porous hollow and nanocages were constructed, in which the materials (Co3O4-NC) were encapsulated with PdAu nanoparticles (NPs). Due to the unique porous structure, the changeable valence state of cobalt and the synergistic effect of bimetallic PdAuNPs, PdAu@Co3O4-NC possessed excellent electron pathways, and showed more exposed active sites. Accordingly, the porous Co-based oxides have been applied to construct an acetylcholinesterase (AChE) electrochemical biosensor, which showed good performance for organophosphorus pesticides (OPs) detection. The optimum biosensing platform based on nanocomposites was applied to exhibit highly sensitive determination of omethoate and chlorpyrifos, with the relative low detection limit of 6.125 × 10−15 M and 5.10 × 10−13 M, respectively. And a wide detection range of 6.125 × 10−15 ∼ 6.125 × 10−6 M and 5.10 × 10−13 ∼ 5.10 × 10−6 M for these two pesticides were achieved. Therefore, the PdAu@Co3O4-NC may represent a powerful tool for ultrasensitive sensing of OPs, and have great potential application.

Determination of total nitrogen and phosphorus in soil by ion chromatography with conductivity detector following persulfate digestion method

This study introduces a new method to determine both TP and TN in one process, reducing the analytical cost and time. During this procedure, soil samples were digested in alkaline potassium persulfate (K2S2O8) at 150 °C for two hours in a reactor to convert organic N (including NH3/NH4+) and P species to the highest oxidation states NO3-, PO43-. After that, H2O2 removes the color of the digest, which could influence the efficiency of the analytical process. Finally, ions NO3- and PO43- were separated on the anion-exchange column and quantified by a conductivity detector. According to the spiked samples, which were made by mixing Bovine serum albumin (BSA) with organic nitrogen and triphenyl phosphate containing organic phosphorus with real soil matrix, the recovery of TN and TP was 85% and 97%, respectively. Both TN and TP linear concentration ranges were between 0.50 and 50 µg.mL-1. The results of relative standard deviation and limit of detection for TN were from 4.2%, and 0.31 mg.kg-1; and for TP were from 3.5%, and 0.25 mg.kg-1.

Stimulus-responsive strategy based on MnO2 nanosheet-modified mesoporous silica nanoprobes for accurate multiple mRNAs detection

Fluorescence detection of multiple mRNAs has attracted great attention for disease diagnosis. In this work, a stimulus-responsive strategy for highly sensitive and accurate multiple mRNAs detection was proposed. This stimulus-responsive detection system was prepared by mesoporous silica nanoparticles (MSN), manganese dioxide (MnO2) nanosheets, and DNA probes. DNA probes were loaded into the pores of MSN, which were closed with MnO2 nanosheets. In the presence of glutathione (GSH) and target mRNAs, MnO2 nanosheets were degraded by GSH, resulting in the release of DNA probes. These DNA probes hybridized to the corresponding target mRNA, thereby changing the fluorescence intensity of fluorophores of DNA probes, which could achieve the quantification of target mRNA. This system could simultaneously detect survivin mRNA and Thymidine kinase 1 mRNA at low background levels with relative limits of detection of 0.9 nM and 0.7 nM, respectively. Moreover, this assay has been successfully applied to detect multiple mRNAs with adequate anti-interference ability in the biological sample.

Determination of Organophosphate Ester Metabolites in Seafood Species by QuEChERS-SPE Followed by LC-HRMS

Organophosphate triesters are compounds widely used in industries and are ubiquitous in the environment, where they can be transformed into organophosphate diesters. Some organophosphate diesters are also used by industry. Several studies suggest organophosphate diesters can have toxic effects for reproduction, and hazardous and mutagenic properties. Due to the impact these compounds can have on marine biota and human beings through the consumption of fish and shellfish, it is necessary to study their presence in widely consumed seafood species. We therefore developed an analytical method for determining six of the most common organophosphate diesters in seafood. The procedure is based on the Quick, Easy, Cheap, Effective, Rugged and Safe extraction method and a solid phase extraction clean-up, followed by liquid chromatography coupled to high-resolution mass spectrometry. The method was optimised and validated for seafood with different lipid content, providing satisfactory relative recoveries (from 89 to 138%) and limits of detection (1.0-50 ng g-1 dry weight), as well as repeatability values (RSD% (n = 5, 100 ng g-1 (dry weight)) lower than 15%. Eight seafood species were analysed using this method and two organophosphate diesters were detected and quantified in all the samples, demonstrating the suitability of the method.

DNA extraction procedures and validation parameters of a real-time PCR method to control milk containing only A2 β-casein

Bovine milk mainly contains two types of β-casein: A1 and A2 variants. In recent years, a new variety of cows’ milk has emerged in dairy sector called “A2 milk”. This novel product is characterised by the absence of A1 β-casein, which has been associated with possible gastrointestinal discomfort due to β-casomorphin-7 (BCM-7) release during gastrointestinal digestion. In this context, methods to verify A1 allele absence in A2 milk are required as a quality control in the A2 milk commercialisation. Therefore, the aim of the present study was to develop a locked nucleic acid (LNA) probe-based duplex real-time PCR (qPCR) assay for A1 allele detection in A2 milk samples. Firstly, four DNA isolation methods from milk somatic cells were optimised and evaluated. Results suggests that the commercial kit NucleoSpin Tissue was the most suitable method in terms of DNA quality and amplificability for downstream applications. Then, optimisation and validation of the qPCR assay were carried out. For both A1 and A2 alleles, the absolute limits of detection of this qPCR assay were 7.3 DNA copies/reaction (2 x 10 −5 ng DNA) and 30.4 DNA copies/reaction (0.1 ng DNA) at a 95% confidence level with synthetic reference DNA samples and heterozygous genotyped DNA sample, respectively. The relative limits of detection were 2% (15 copies) and 5% (152 copies) for A1 allele in A2 samples at a 95% confidence with synthetic reference and genotyped DNA samples, respectively. The qPCR assay was robust, with intra- and inter-assay variability below 4.3%, and specific, differentiating between A1 and A2 alleles with 100% genotyping accuracy. In conclusion, this cost-effective and fast method could be used to discriminate A1 allele in A2 samples and, consequently, to verify A1 allele absence in “A2 milk” by screening commercial product on the market. • The LNA duplex qPCR assay developed could be used to verify A1 allele absence in “A2 milk”. • LNA probes reliably discriminated between A1 and A2 alleles. • The relative limits of detection reach up to 2% (15 copies) for A1 allele in A2 samples at a 95% confidence. • Milk is a challenging matrix for DNA isolation due to the presence of PCR inhibitors that leads to low DNA yield.

Determination of relative sensitivity factor, sputtering rate, and detection limits of deuterium in deuterium ion‐implanted Zircaloy‐4 using secondary ion mass spectrometer

Zirconium‐based alloys are extensively used in the nuclear industry as materials for reactor core components. These alloys are used in fuel cladding and pressure tubes with 1H2O or 2H2O as the primary heat exchange fluid. Continuous usage of pressure tubes and fuel cladding inside the reactor results in heavy ingress of hydrogen (1H) or deuterium (2H), which gives rise to the formation of hydrogen (or deuterium) precipitates in the host of zirconium matrix. This is called hydrogen (or deuterium) embrittlement phenomenon. Therefore, determination of hydrogen or deuterium concentration periodically in zirconium alloy pressure tubes and cladding are crucial for safe operation of nuclear reactors. Hence, in this work, secondary ion mass spectrometry (SIMS) has been utilized to determine the relative sensitive factor (RSF), sputtering rate, and detection limits of 2H in 2H+ ion‐implanted Zircaloy‐4 sample. SIMS analysis has been carried out using O2+ and Cs+ primary ion beams. Depth profiles of various elemental and molecular secondary ions have been monitored to determine the RSF values and detection limits of 2H in the sample under different primary ion beam analysis conditions. Sputtering rate under different analysis conditions has also been determined from the correlation between the projected range of 2H+ ions in Zircaloy‐4 sample determined from Stopping and Range of Ions in Matter (SRIM) software and the depth of the crater formed by primary ion beam bombardment process. The projected range of 2H+ ions in Zircaloy‐4 was estimated to be ~524.2 nm using the simulation carried out by SRIM software. The projected range, evaluated by SRIM software, was utilized for depth scale calibration of SIMS sputtered time profiles. The SIMS depth profiles were also calibrated by determining the depth of the SIMS crater by using optical depth profilometer. The values of range estimated by SRIM as well as optical profilometer were found to be in good agreement, within instrument uncertainty.

Toxic cadmium selective sequestration from food samples using melamine anchored magnetic cellulose by surface imprinting route

Cadmium is very toxic for living organisms hence selective and efficient control capturing of it is necessary. To reach this goal a novel imprinted polymer was developed using melamine anchored MnFe2O4 – cellulose. Magnetic cellulose was synthesized through an ultrasound-assisted precipitation route. Chloropropyltriethoxysilane was used to attach melamine to the magnetic cellulose surface. Response surface methodology employed to optimize effective parameters on cadmium adsorption. Time of 13 min, the dosage of 18 mg and pH of 8 was selected as optimum conditions. The relative standard deviation, detection limits and adsorption capacity were 2,5%, 0.50 µgL−1 and 138 mg g−1 respectively. The selectivity coefficient of Cd(II) relative to Cu(II), Co(II), Ni(II) and Pb(II) were 4, 5, 12 and 3, respectively. Regeneration of the sorbent was performed using HCl (0.5 mol L−1) as eluent. The method was used for cadmium preconcentration in fish, lettuce and liver with satisfactory results.

Interfacial charge changes induce the responsive behavior of two analytes based on novel carbon nanomaterials

Nanoscale technique has been regarded as the manipulation of organic and inorganic entities at the atomic level and unique features are acquired. Such surface-passivated nanodomains are exploring diverse roles by expanding the range of their prospects. The well-defined fluorescent framework based on carbon quantum dots has been described, which can be utilized to detect Fe3+ and ascorbic acid (AA). The growth of carbon dots has been realized in the presence of 3-Aminophenylboronic acid and citric acid and the synthesis route is based on hydrothermal condition. Under the excitation at 365 nm, the nanoparticles give rise to intensive blue emission at 450 nm. The addition of Fe3+ induces the signal suppression. Meanwhile, the presence of ascorbic acid can substantially recover the emission, which will be caused by the reduction of trivalent iron ions by ascorbic acid. The titration profile for both Fe3+ and ascorbic acid in the broad range of 5-450 μM and 10-350 μM are in the forms of linear equations. The relative low detection limits (394 nM and 448 nM) are determined for Fe3+ and AA respectively. The development of multiple targets sensing on the basis of carbon dots achieves a deeper understanding of fundamental properties in nanomaterials.

Closed-tube saltatory rolling circle amplification with hydroxynaphthol blue for visual on-site detection of peanut as an allergenic food

Peanut allergy as one of the major causes of food-induced anaphylaxis is usually life-threatening for specific individuals. Nowadays, the effective remedy is avoidance of consuming allergen-containing food, urging monitoring the presence of peanut in foods. Herein, we proposed a closed-tube saltatory rolling circle amplification (SRCA) assay with hydroxynaphthol blue (HNB) for visual on-site detection of peanut allergen, displaying highly specificity for Ara h 1-encoding gene. The results can be discriminated by naked eye without opening the tube, averting costly sophisticated apparatus and reducing the risk of cross-contamination. The assay was 1000-, 100- and 10-fold more sensitive than PCR, LAMP and SRCA, respectively. The relative limit of detection is 0.01% in a binary mixture. The relative sensitivity, specificity and accuracy of this method were 100%, 97.50% and 98.67%, respectively. Thus, the visual closed-tube HNB-SRCA assay with superiorities of easy-to-perform, cost-effective and user-friendly has excellent potential for on-site application of food allergy.