Instrumental Detection Limits Research Articles

Novel automated identification and quantification database using liquid chromatography quadrupole time-of-flight mass spectrometry for quick, comprehensive, cheap and extendable organic micro-pollutant analysis in environmental systems

In order to protect human health and the environment, highly efficient, low-cost, labor-saving, and green analysis of toxic chemicals are urgently required. To achieve this objective, we have developed a novel database-based automated identification and quantification system (AIQS) using LC-QTOF-MS. Since the AIQS uses retention times (RTs), exact MS and MS-MS spectra, and calibration curves of 484 chemicals registered in the database instead of the use of standards, the targets can be determined with low-cost in a short time. The AIQS uses Sequential Window Acquisition of All Theoretical Fragment-ion Spectra as an acquisition method by which we can obtain accurate MS and MS-MS spectra of all detectable substances in a sample with minimal interference from co-eluted peaks. Identification is certainly done using RTs, mass error, ion ratios (a precursor to two product ions), and accurate MS and MS-MS spectra. Consequently, the chance of misidentification is very low even in dirty samples. To examine the accuracy of the AIQS, two collaborative tests were conducted. The first test used 208 pesticide standards at two concentrations (10 and 100 ng mL−1) using 7 instruments, and showed that average trueness was 106 and 95.2%, respectively, with relative standard deviations of 90% of the test compounds below 30%. The second collaborative study involved 5 laboratories carrying out recovery tests on 200 pesticides using 10 river waters. The average recovery was 71.6%; this was 15% lower than that using purified water probably due to the matrix effects. The average relative standard deviation was 30% worse than that of measurement of the standards. Both the recovery and reproducibility, however, satisfied the criteria of Analytical Method Validity Guidelines, Ministry of Health, Labour and Welfare, Japan. Instrument detection limits of 96% of the registered compounds are below 10 pg. The AIQS allows for easy addition of new substances and retrospective analysis after their addition. The results applied to actual samples showed that the AIQS has sufficient identification and quantification performance as a target screening method for a large number of substances in environmental samples.

An advanced LC-MS/MS protocol for simultaneous detection of pharmaceuticals and personal care products in the environment.

The development of appropriate analytical screening techniques for pharmaceuticals and personal care products (PPCPs) is the basis for studying the distribution and environmental impact of emerging contaminants (ECs). Mass spectrometry-based screening methods vary with the complexity of the target compounds. It is challenging to balanceboth positive and negative ion quantification with a low detection limit. To establish a set of experimental methods including extraction, chromatography-separation and mass spectrometry screening is one of the most important topics in PPCP research. This paper describes a universal and efficient qualification and quantification protocol for the simultaneous detection of 34 PPCPs in different environmental samples in a single analytical data acquisition run. Thirty-four representative PPCPs, which are widely distributed in the environment with high ecological toxicity and complex chemical structures, were selected as representative target ECs. The extraction of the target PPCPs was achieved using only one solid-phase extraction cartridge without the need to adjust the pH of samples. The enriched samples were detected by LC-MS/MS in both positive and negative ion modes simultaneously. The protocol was evaluated based on the accuracy, precision, detection limits and matrix effects. This method achieved simultaneous detection of PPCPs in both positive and negative ion modes, with a single analytical cycle of 12 min. The observed SPE recoveries were between 40% and 115%. The instrumental detection limits (IDL) varied from 0.01 to 1 pg, and the method detection limits (MDL) were between 0.002 and 3.323 ng/l in different matrices. Most of the PPCPs were subjected to matrix suppression below 30%. The method was successfully applied for quantitative analysis of the PPCPs in different environmental samples, including river samples, wastewater treatment plant (WWTP) samples and soil samples. This protocol developed a rapid and efficient detection method to simultaneous qualitative and quantitative 34 representative PPCPs in the environment. The IDL ranged from 0.01 to 1 pg and the MDL ranged from 0.002 to 3.323 ng/l in different matrices. The detection limit was one order of magnitude lower compared to previous studies. The protocol also provided a wide application range for different environmental matrices, which permitted the migration and transformation of PPCPs to be explored.

Development and Method Validation of Butyric Acid and Milk Fat Analysis in Butter Blends and Blended Milk Products by GC-FID.

Butyric acid is a short-chain saturated fatty acid with four carbon atoms in its molecule. It is unique to butter made from cow's milk and is an indicator to evaluate the quality of butter and milk products as stated in their ingredient labels. This study determined the milk fat content of butter blends and blended milk products by analyzing the content of butyric acid prepared as derivatives of methyl esters prior to injection into a gas chromatography flame ionization detector (GC-FID). Results revealed that this method had specificity, a linear relationship for concentration in the range of 0.04-1.60 mg/mL, a coefficient of determination (R2) > 0.999, an instrumental limit of detection (LOD) and a limit of quantitative analysis (LOQ) at 0.01% and 0.10% of total fat, respectively, and an instrumental working range of 0.10-3.60% of total fat. The results of a precision study using relative standard deviation (RSD) was 1.3%, while an accuracy study using the spiking method showed % recovery in the range of 98.2-101.9%. The method linearity range for milk fat analysis had a good linear correlation in the range of 3-100% of total fat (R2 > 0.999). Results for method LOD and LOQ were 1% and 3% of total fat, respectively. This method also had good precision (1.3% RSD) and accuracy (99.6-100.1% recovery), which indicates reliability in terms of precision and accuracy. This method, therefore, can be used to check claims about the quality of blended butter and blended milk products to ensure consumer confidence in product quality.

Trace determination of the hydrogen sulfide biomarker thiosulfate in human urine by HPLC coupled with element selective ICPMS/MS detection

Hydrogen sulfide is a toxic gas but also established as a naturally occurring gaseous signaling molecule in humans, playing key physiological roles with particular involvement in lung disease including COVID-19. Thiosulfate is the conventional biomarker of hydrogen sulfide and is excreted in human urine at low micromolar levels. Thiosulfate is amenable to detection by the element-selective inductively coupled plasma tandem mass spectrometry (ICPMS/MS), but sulfur speciation in human samples at trace levels is challenging due to the high complexity of human sulfur metabolome and the utility of this detector under such settings has not been demonstrated. We report a method for thiosulfate determination in human urine at trace physiological levels by HPLC-ICPMS/MS. The method involved one-step derivatization to improve chromatographic behavior followed by direct injection. The instrumental limit of detection was 1.4 μg S L−1 (0.02 μM or 0.1 pmol). In a group of samples from volunteers (n = 24), measured thiosulfate concentrations in the diluted urine matrix were down to 8.0 μg S L−1 with a signal-to-noise ratio >10. The method was validated for recovery (80–110%), repeatability (RSD% <5%), and linearity (r2 = 0.9999, at a tested working concentration range of 0.01–1.0 mg S L−1), and the accuracy was assessed by comparing with HPLC-ESIMS/MS which showed agreement within ±20%. This work demonstrates the applicability of HPLC-ICPMS/MS for sulfur speciation at trace levels in a matrix with complex sulfur metabolome as human urine and provides a sensitive method for the determination of the hydrogen sulfide biomarker.

Ultrafast and selective adsorption of pharmaceuticals from wastewater by precisely designed metal organic framework with missing linker defects

Pharmaceuticals and personal care products (PPCPs) are widely used and frequently detected in the environment. A series of novel, precisely designed metal-organic framework (MOF) materials with long-range ordered defective structure was proposed by tuning the node connectivity and missing linkers/clusters. The adsorption abilities of anti-inflammatory drugs were significantly improved (79.87 mg/g, 561.37 mg/g·min for ibuprofen (IBU)) over the defective UiO-66 (node connectivity = 7.8), which were 2.5 and 59.8 times higher than that over the defect-free one (32.16 mg/g, 9.39 mg/g • min). The adsorption rate constant of IBU was accelerated 1.12 × 104 times greater than that of the activated carbon. For the first time, the performance was evaluated under the environmentally relevant concentration (200 μg/L to 0.025 μg/L) with removal percentages ∼ 90% within 1 min. Theoretical calculations were conducted to study the mechanism. Furthermore, 15 micropollutants with various functional groups (sulfonamides, quinolones, macrolides, etc.) with high environmental risks proved our concept that electrostatic interaction could be the primary mechanism. Real wastewater in Beijing was sampled and evaluated the performance of removing the pharmaceuticals (concentration: 199.21 ± 3.65 ng/L ∼ 0.10 ± 0.01 ng/L), a complete removal can be achieved in only 3 min with concentrations below instrumental detection limits. This finding provides a promising strategy for designing materials for rapidly removing pharmaceuticals in water.

Novel immunochromatographic estimation of lamb content in meat products using IgG as biomarker

The aim of this study was to develop a novel immunochromatographic analysis (ICA) for the determination of lamb additives in raw meat and meat products. Sheep immunoglobulins of class G (IgG) served as the molecular identifier. The ICA was implemented in a sandwich format using anti-species antibodies labeled with gold nanoparticles. Sheep IgG was detected with the instrumental detection limit of 60 ng/mL and the cutoff of 10 ng/mL within 13 min. The high specificity of the ICA towards only sheep IgG was confirmed within the determination of immunoglobulins of other mammals and birds and analysis of extracts from the corresponding sorts of meat. It was shown that the test system can reliably determine 1% lamb additive in chicken meat. The test system was successfully used for lamb identification in dumplings of various compositions. The proposed ICA is a promising approach for the determination of species-specific immunoglobulins as biomarkers of composition and adulteration of meat products.

An aptamer lateral flow assay for visual detection of Microcystins-LR residue in fish

Microcystin-LR (MC-LR) contamination in aquatic foods is a serious health threat to people. Here, a simple aptamer-based colorimetric lateral flow assay (LFA) was developed for on-site and visual detection of MC-LR for the first time. This detection system was designed on the basis of competition for Apt-A2C aptamer between MC-LR and its partial complementary sequence. Apt-A2C modified gold nanoparticles (AuNPs) were used as the signal reporter to realize the colorimetric readout by naked eyes, and the signal intensity of test line was inversely proportional to the concentration of MC-LR in the sample solution. Under optimized conditions, this aptamer-based LFA platform can visually detect MC-LR as low as 2.5 ng/mL with a linear range of 1–50 ng/mL, and an instrumental limit of detection of 0.84 ng/mL using a scanning strip reader. The whole assay can be finished within 5 min, starting from sample loading to color acquisition. The developed aptamer-based LFA was successfully applied in the detection of MC-LR in spiked fish tissue samples with the recovery rates ranged from 74.3% to 85.6%, and the results agreed well with those of tandem mass spectrometry. Besides, it had excellent selectivity toward MC-LR as the detection results were not affected by the potentially interfering molecules in real aquatic food matrix. Therefore, the LFA strip is an easy-to-use tool for instrument-free detection of MC-LR, and it can be applied to other toxins in aquatic foods with available aptamers.

Green derivatization strategy coupled to high-resolution mass spectrometry (QTOF-MS) for patulin monitoring in fruit products

Mycotoxin monitoring is critical to ensure that foods are safe for human and animal consumption, so highly sensitive and selective detection methods are required by regulatory agencies. In this work, a new method for the analysis of patulin in fruit products was developed based on the high reactivity of the mycotoxin with sodium benzene-1,2-bis(thiolate). This previously unknown reaction occurs in buffered aqueous solution and results in a stable adduct that can be sensitively determined by tandem time-of-flight mass spectrometry. The proposed method is performed by a simple dilute-and-shoot procedure without the use of organic solvents and was able to determine patulin with an instrumental detection limit of 0.5 μg L−1. When the method was applied to the analysis of fortified apple and pear products, recovery values ranged from 95 to 100%. Finally, the applicability under real conditions was demonstrated by the successful analysis of reference and quality control materials.

AND Logic-Gate-Based CRISPR/Cas12a Biosensing Platform for the Sensitive Colorimetric Detection of Dual miRNAs.

Clustered regularly interspaced short palindromic repeats (CRISPR)-Cas (CRISPR-associated) system has been widely explored for the detection of disease-related nucleic acids. Nevertheless, the simultaneous detection of multiple nucleic acids within one assay using the CRISPR-Cas system is still challenging. In this study, we develop an AND logic-gate-based CRISPR-Cas12a biosensing platform to achieve the sensitive colorimetric detection of dual miRNAs. Specifically, the DNA probe was designed to recognize the binary input of miRNAs and to output trigger DNA, which activated the CRISPR-Cas12a system to cut single-stranded DNA (ssDNA). The ssDNA on magnetic beads (MBs) was cleaved by the activated CRISPR-Cas12a, causing the separation of glucose oxidase (GOx) from MB and the subsequent generation of a colorimetric signal. The color change induced by 1 pM of target miRNAs can be directly distinguished by the naked eye and the instrumental limit of detection reaches 36.4 fM. The overexpressed miR-205 and miR-944 in the real human serum can be detected, allowing us to differentiate between lung cancer patients and healthy people. Furthermore, the developed strategy achieves simultaneous detection of dual miRNAs using CRISPR-Cas12a with one kind of crRNA, avoiding sophisticated nucleic acid amplifications and the use of bulky instruments. The current method can broaden the CRISPR-Cas12a-based applications for multiple biomarkers detection and precise disease diagnosis.

Use of QuEChERS as a manual and automated high-throughput protocol for investigating environmental matrices

Environmental pollution has strong links to adverse human health outcomes with risks of pollution through production, use, ineffective wastewater (WW) remediation, and/or leachate from landfill. ‘Fit-for-purpose’ monitoring approaches are critical for better pollution control and mitigation of harm, with current sample preparation methods for complex environmental matrices typically time-consuming and labour intensive, unsuitable for high-throughput screening.This study has shown that a modified ‘Quick Easy Cheap Effective Rugged and Safe’ (QuEChERS) sample preparation is a viable alternative for selected environmental matrices required for pollution monitoring (e.g. WW effluent, treated sludge cake and homogenised biota tissue). As a manual approach, reduced extraction times (hours to ∼20 min/sample) with largely reproducible (albeit lower) recoveries of a range of pharmaceuticals and biocidal surfactants have been reported. Its application has shown clear differentiation of matrices via chemometrics, and the measurement of pollutants of interest to the UK WW industry at concentrations significantly above suggested instrument detection limits (IDL) for sludge, indicating insufficient removal and/or bioaccumulation during WW treatment. Furthermore, new pollutant candidates of emerging concern were identified – these included detergents, polymers and pharmaceuticals, with quaternary ammonium compound (QAC) biocides observed at 2.3–70.4 mg/kg, and above levels associated with priority substances for environmental quality regulation (EQSD). Finally, the QuEChERS protocol was adapted to function as a fully automated workflow, further reducing the resource to complete both the preparation and analysis to <40 min. This operated with improved recovery for soil and biota (>62%), and when applied to a largely un-investigated clay matrix, acceptable recovery (88.0–131.1%) and precision (≤10.3% RSD) for the tested pharmaceuticals and biocides was maintained. Therefore, this preliminary study has shown the successful application of a high-throughput QuEChERS protocol across a range of environmental solids for potential deployment in a regulated laboratory.

Determination of free amino acids in Eriocheir sinensis by ultra-high performance liquid chromatography-high resolution mass spectrometry

游离氨基酸不仅是一类重要的营养物质,更与中华绒螯蟹独特的滋味和香味密切相关。对游离氨基酸含量进行测定,能为中华绒螯蟹产品的品质评价和风味研究提供有价值的信息。该工作通过优选提取溶剂、优化仪器测定参数,最终使用5%(v/v)高氯酸水溶液提取目标物,采用XDB-C18色谱柱(100 mm×4.6 mm, 1.7 μm),以0.1%(v/v)甲酸水溶液-乙腈为流动相进行梯度洗脱,在电喷雾正离子电离、选择离子扫描模式下进行检测,外标法定量,建立了超高效液相色谱-高分辨质谱(UHPLC-HRMS)测定中华绒螯蟹中17种游离氨基酸含量的方法。结果表明,17种氨基酸在10.0~200.0 mg/L范围内线性关系良好,相关系数(R2)≥0.9990,仪器检出限为0.3 mg/L,仪器定量限为1.0 mg/L。在中华绒螯蟹可食部分中按三水平进行加标回收试验,各目标物的回收率在78.4%~105.3%之间。通过对仪器和方法精密度进行评估,发现17种氨基酸测定仪器重复性的RSD≤4.2%,方法重复性试验的RSD≤5.2%,再现性试验的RSD≤11.4%,精密度数据均在合理范围内。利用该研究建立的检测方法对20个中华绒螯蟹样本进行了实际样品检测,总结了17种游离氨基酸在蟹肉、蟹膏、蟹黄中的分布特点,验证了该方法是一种前处理简便、选择性好、准确度高的检测技术。

Investigation of Aggregation Behavior and Molecular Weight Changes of Asphaltene Model Compound

We investigate the aggregation of Violanthrone-78 (VO-78), a model asphaltene compound, in mixtures of toluene and n-heptane (heptol) using spectroscopic and dynamic and static light scattering techniques. The light scattering experiments were conducted using pure toluene and n-heptane, as well as 25/75, 50/50, and 75/25 heptol solvents. Furthermore, the concentration of VO-78 varied from 10-8 M to 10-3 M in these suspensions. The dynamic light scattering experiments were used to study the aggregate sizes from the intensity autocorrelation function at different n-heptane volume fractions. The results show the onset of aggregation of about 50 % n-heptane volume fractions. The aggregate sizes in toluene, within the range of concentrations examined, were below the instrument's detection limit (&lt; 5 nm) but increased with increasing dosages of n-heptane. On the other hand, the aggregate size in pure heptane was observed to be greater than the maximum limit of the instrument (&gt; 10 μm). Furthermore, the static light scattering experiments provided an anomalous behavior. Increasing concentrations of VO-78 in the solvent resulted in lowering the parameter Kc/Rq, where c is the molar concentration.

Quantum-dot-based sandwich lateral flow immunoassay for the rapid detection of shrimp major allergen tropomyosin

Tropomyosin (TM) has long been reckoned as the major allergen in shrimp is known to cause both food safety and public health concern all over the globe. In the present study, a simple, rapid, specific and accurate quantum-dot-based sandwich fluorescent lateral flow Immunoassay (LFIA) was developed for the detection of TM in processed foods. Fluorescent probes were prepared by EDC/NHS reaction of rabbit anti-TM polyclonal IgG with carboxylated quantum dots. Obtained results indicated that the visual detection limit (VDL) and the instrumental detection limit (IDL) of were 0.05 μg mL-1 and 0.01 μg mL-1, respectively. In addition, the detection time could be controlled within ten min. Furthermore, the established method showed no cross-reactivity with other species except shrimp. Moreover, the intra- and inter-assay coefficients of variation of the spiked samples were 8.87 %− 11.9 % and 7.75 %− 21.12 %. Besides, LFIA could detect 8 of 9 real food samples which were identified as TM-positive by the validated ELISA method. Additionally, 0.045 μg g-1 of incurred TM in model processed foods (roast fish fillet, boiled meatball and steamed meatball) also could be detected by the developed assay. These findings indicated that the LFIA developed in this research possess a great significance on the rapid and accurate detection of allergens in shrimp foodstuffs, related products and their production lines.

Validation of calcium (Ca) analysis in dolomite fertilizer using atomic absorption spectrophotometer (AAS)

The method of determining calcium (Ca) in dolomite fertilizer has been validated using atomic absorption spectrophotometer (AAS). Determining calcium (Ca) in dolomite fertilizer refers to the Indonesian National Standard (SNI) 02-2804-200. Based on the results of the calcium (Ca) test on dolomite fertilizer, the correlation coefficient (r) was 0.9949, and the % relative standard deviation (RSD) was 0.6472%, less than 2/3 CV Horwitz of 1.5963. The accuracy value is 100.30%, the precision value is 0.6471%, the detection limit for the LOD method is 0.2817, the LOQ is 0.9390, and the instrument detection limit is LOD 0.1159 and LOQ 0.3864. This study shows that the determination of calcium (Ca) in dolomite fertilizer using the SNI method using the Atomic Absorption Spectrophotometer (AAS) can be used with valid results.

Appraisal and Validation of a Method (MVU-AAS) Used for the Detection of a Toxic Metal Mercury (Hg) in Poultry Feed Available in Bangladesh

Toxic metal mercury (Hg) in poultry feed might affect seriously on the environment and human being. So continual or gradual analyses of toxic metal contents in poultry feedstuff are of prime significance for assessing the feed quality and consumer safety. In this study, a method named Mercury Vapor Unit Atomic Absorption Spectrometry (MVU-AAS) was used to analyze the content of Hg in poultry feed in compliance with the Council Directive 333/2007/EC, Commission Decision 657/2002/EC. The metal Hg was analyzed from the feed sample inthe laboratory by MVU-AAS (Model: AA-7000 Shimadzu, Japan) and the absorbance was read at 253.65 nm wavelength, The method was confirmed and validated by complying with the international guidelines and assessing a number of criteria say system suitability, precision studies, linearity check, uncertainty measurement and recovery % etc.. The results revealed that the coefficient of variation (CV%) for system suitability and precision was &lt;10% for the metal (Hg) detected in this study. The linearity of the calibration curves was excellent (r2&gt;0.998) at various concentrated levels. The limits of detection (LoD) value in feed was 0.007 mg/Kg and the limit of quantification (LoQ) value in feed sample was found 0.023 mg/Kg. The values of instrumental detection limit (IDL) and instrument quantification limit (IQL) were 0.045(μg/l), and 0.15(μg/l), respectively. The recovery (%) found for the metal was 92.29 %. The overall CV% of repeatability and reproducibility ranged from 3.27 % to 5.92 %. The value ranges from 12 to 16 was observed for the measurement uncertainty (%) of Hg in this study. The proposed validation criteria indicate that it is a reliable method that can be used easily for the routine analysis of toxic metal (Hg) content in poultry feed sample.

Method Validation and Uncertainty Estimation for Total Phosphorus Determination in Animal Feed Using UV-Vis Spectrophotometer

Objective: The study presents the validation protocol for the determination of total phosphorus content at parts per million (ppm) (μg/L) levels in animal feed by a UV-Vis spectrophotometer. Methods: The measured absorbance of solutions against the blank solution was at 400 nm with the spectrophotometer. A combined ammonium heptamolybdate tetrahydrate and ammonium monovanadate blue solution was used as a coloring reagent for detection. This method was validated by evaluation of statistical parameters such as linearity, sensitivity, limits of detection (LOD) and quantification (LOQ), precision, accuracy, and measurement uncertainty using a matrix blank (MB) against the phosphorus standard. Results: The Instrumental Detection Limit was 0.066 ppm and the Instrumental Quantification Limit was 0.22 ppm, respectively, while the phosphorus recovery and repeatability percent were 101.15% and 0.11%, respectively. However, the linearity of this method was 0.1 to 30 ppm. The measurement uncertainty of this method was 2.82%, following Commission Regulation (EC). Conclusion: The estimated parameters in the validation protocol, were found to meet the imposed performance criteria, and the procedure was validated for the intended use.

Development of a Tube Plasma Ion Source for Gas Chromatography-Mass Spectrometry Analysis and Comparison with Other Atmospheric Pressure Ionization Techniques.

A tube plasma ionization (TPI) open-air source for gas chromatography-mass spectrometry (GC-MS) was developed. This source is based on an inverse low temperature plasma configuration where the pin inner electrode is applying the high voltage and the grounded electrode is the housing itself. The ionization possibilities were tested by using an EPA mix of priority contaminants, showing that 68% of the analytes could undergo both proton-transfer and charge-exchange reactions. The potential of using different discharge gases (He and Ar) to ionize the analytes and auxiliary gases (He, N2, O2, and synthetic air) to transport the ions toward the MS was carefully investigated. Additionally, the addition of water was also tested to show the different ionization trends in the TPI source. Finally, the ionization by TPI under both dry and wet conditions was compared with other gas-phase atmospheric pressure ionization sources showing TPI could ionize a wider range of compounds (97%) than atmospheric pressure chemical ionization (APCI, 95%) and atmospheric pressure photoionization (APPI, 87%). Besides, the detection capability of TPI was better than APCI and APPI, achieving instrumental limits of detection down to 3 fg on column, which demonstrates the great potential of this ionization source for GC-MS determinations.

Efficacy of a vermifilter at mitigating greenhouse gases and ammonia emissions from dairy wastewater.

Dairy effluent is a potential source of gaseous pollutants associated with global warming and soil acidification. Mitigating such emissions during handling and storage requires substantial financial and labor input. This study evaluated a low-cost technology for mitigating gaseous emissions from dairy wastewater. For 9 mo, a pilot-scale vermifilter system installed on a commercial dairy farm was studied. Bimonthly samples of the dairy wastewater influent and effluent from the vermifilter system were collected. These samples' potential gas emissions (ammonia [NH3 ], methane [CH4 ], carbon dioxide [CO2 ], and nitrous oxide [N2 O]) were measured using a closed-loop dynamic flux chamber method. Results indicated the following reductions in emissions of these gases by the vermifilter system: 84-100% for NH3 , 58-82% for CO2 , and 95-100% for CH4 . Nitrous oxide emissions were mainly below our instrument detection limits and were thus not reported. The vermifilter showed the potential of reducing the global warming potential from the dairy wastewater by up to 100%. This study further indicated that higher ambient temperatures led to higher emissions of CH4 (R2 =.56) and NH3 (R2 =.53) from untreated dairy wastewater. Overall, the vermifilter system has potential to mitigate gaseous emissions from dairy wastewater.

Electrochemical detection of gram-negative bacteria through mastoparan-capped magnetic nanoparticle

The increasing number of multidrug resistance microorganisms is an alarming threat, and their rapid detection is essential to prevent nosocomial, foodborne, or waterborne infections. Many peptides derived from the venom of wasp Synoeca surinama have antimicrobial activity against Gram-positive and Gram-negative bacteria. Synoeca-MP, an antimicrobial peptide (AMP) from mastoparan family, seems to increase bacterial membrane permeability, promoting cytotoxicity and membrane disruption. Here Synoeca-MP was evaluated as biorecognition element tethered over chitosan-coated magnetic nanoparticles (Fe3O4-Chit). The transducing layer of the biosensor was developed from the self-assembling of 4-mercaptobenzoic acid (4-MBA) monolayer onto gold substrate. Atomic force microscopy (AFM) analyses confirmed the biointeraction between AMP and different pathogens membranes. The fabrication and performance of the biosensing assembly were characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Detection of Enterococcus faecalis (G+), Klebsiella pneumoniae (G-), Pseudomonas aeruginosa (G-), and Candida tropicalis was assessed in a recognition range from 101 to 105 CFU.mL−1. An instrumental limit of detection of 10 CFU.mL−1 was obtained for each specimen. However, the device presented a preferential selectivity towards Gram-negative bacteria. The proposed biosensor is a sensitive, fast, and straightforward platform for microbial detection in aqueous samples, envisaged for environmental monitoring applications.

Silver-enhanced lateral flow immunoassay for detection of microcystin-LR in drinking water

ABSTRACT An immunochromatographic test system based on the indirect competitive format has been developed for the rapid control of cyanotoxin microcystin-LR (MC-LR) in drinking water. To increase the assay sensitivity, a hydroquinone-based reduction of silver ions on the surface of gold nanoparticles as part of the immune complexes formed on the immunochromatographic membrane has been carried out. This stage allows for the enhancement of the colouration in test strip zones. The developed test system is characterised by an instrumental limit of detection of 0.05 ng/mL, a cut-off of 0.5 ng/mL, and a working range of the detectable concentrations of 0.08–0.42 ng/mL. The assay duration was 17 min. The applicability of the test system for MC-LR detection in drinking water is demonstrated. The assay recoveries vary from 90% to 120%.