On-site Quantitative Analysis Research Articles

Inorganic–organic hybrid nonwoven fabrics with colorimetric detection capability for borate ions in aqueous solutions

Abstract A nonwoven fabric sheet with an immobilized colorimetric reagent was prepared to detect borate anions in aqueous media. The fabric comprised immobilized chromotropate and 1-butanesulfonate anions and chromotropate, as the colorimetric reagent, per anion exchange capacity of the layered double hydroxide. The resulting sheet quantitatively detected borate anions through photoluminescence measurements. Thus, it can be used for onsite quantitative analysis of dissolved boron in water, with promising potential for water quality monitoring and, consequently, sustainable and safe water resources globally.

A novel colorimetric sensor through peroxymonosulfate activated by CoFe@CN nanozymes for on-site resorcinol detection

The presence of resorcinol (RS) in water contaminated with pollutants may engender environmental and ecosystem risks. In this study, we developed rapid and efficient colorimetric methods for the on-site quantitative determination of RS. Specifically, a synthetic nanozyme composed of nitrogen-doped carbon-coated cobalt-iron (CoFe@CN) was utilized to initiate the oxidation reaction of 3,3′,5,5′-tetramethylbenzidine (TMB) with the activator of peroxymonosulfate (PMS). Compared to the activator of hydrogen peroxide (H2O2), PMS demonstrated a sixfold enhancement in catalytic efficacy, markedly elevating the detection performance. Density Functional Theory calculations indicate that RS can serve as a reducing agent for oxTMB, confirming the theoretical feasibility of this process. A linear relationship between inhibition rate (IR %) of RS concentration and absorbance was established and the colorimetric analysis revealed a linear relationship between RS concentration and gray scale values over the range of 0–45 μM, with a detection limit of 3.39 μM. Furthermore, smartphone-based analysis of color images allows for on-site quantitative analysis of RS concentration, leveraging portability and real-time detection capabilities. This study provides pioneering analytical support for on-site water quality monitoring within the ecological environment.

Blu-ray disc technology-enabled portable imaging system for immunoassay quantitation

In this work, we have developed a portable laser scanning imaging system derived from Blu-ray disc technology for high-throughput biochip and sensor array characterization. This portable imaging system was constructed by adapting a standard Blu-ray drive to perform the scanning or imaging of an entire disc or interested regions. In addition, we have compiled a complete operating software program to process the raw data, generate the assay image, and perform quantitative analysis. Furthermore, the developed BD-LSI system was successfully applied to the quantitative detection of Anti-Müllerian hormone (AMH), which is an important biomarker of reproductive potential, in standard physiological buffers and serum samples. The achieved detection limit is as low as 18 pg/mL with a dynamic range of up to 25 ng/mL, which meets the needs of clinical diagnosis. As validated by comparing with the Clinical Laboratory Improvement Amendments (CLIA) data on the same set of samples, the consistent results confirm that this BD-LSI system holds promise for multiplex on-site quantitative analysis at community clinics and even at home settings for self-monitoring of individual health.

A colorimetric/electrochemical microfluidic biosensor using target-triggered DNA hydrogels for organophosphorus detection

Organophosphorus compounds are widely distributed and highly toxic to the environment and living organisms. The current detection of organophosphorus compounds is based on a single-mode method, which makes it challenging to achieve good portability, accuracy, and sensitivity simultaneously. This study designed a multifunctional microfluidic chip to develop a dual-mode biosensor employing a DNA hydrogel as a carrier and aptamers as recognition probes for the colorimetric/electrochemical detection of malathion, an organophosphorus compound. The biosensor balanced portability and stability by combining a microfluidic chip and target-triggered DNA hydrogel-sensing technologies. Moreover, the biosensor based on target-triggered DNA hydrogel modified microfluidic developed in this study exhibited a dual-mode response to malathion, providing both colorimetric and electrochemical signals. The colorimetric mode enables rapid visualization and qualitative detection and, when combined with a smartphone, allows on-site quantitative analysis with a detection limit of 56 nM. The electrochemical mode offers a broad linear range (0.01–3000 μM) and high sensitivity (a limit of detection of 5 nM). The two modes could validate each other and improve the accuracy of detection. The colorimetric/electrochemical dual-mode biosensor based on target-triggered DNA hydrogel modified microfluidic chip offers a portable, simple, accurate, and sensitive strategy for detecting harmful environmental and food substances.

Upconversion-based hydrogel kit with Python-assisted analysis platform for sample-to-result detection of organophosphorus pesticide

On-site quantitative analysis of pesticide residues is crucial for monitoring environmental quality and ensuring food safety. Herein, we have developed a reliable hydrogel portable kit using NaYbF4@NaYF4: Yb, Tm upconversion nanoparticles (UCNPs) combined with MnO2 nanoflakes. This portable kit is integrated with a smartphone reader and Python-assisted analysis platform to enable sample-to-result analysis for chlorpyrifos. The novel UCNPs maximizes energy donation to MnO2 acceptor by employing 100 % of activator Yb3+ in the nucleus for NIR excitation energy collection and confining emitter Tm3+ to the surface layer to shorten energy transfer distance. Under NIR excitation, efficient quenching of upconversion blue-violet emission by MnO2 nanoflakes occurs, and the quenched emission is recovered with acetylcholinesterase-mediated reactions. This process allows for the determination of chlorpyrifos by inhibiting enzymatic activity. The UCNPs/MnO2 were embedded to fabricate a hydrogel portable kit, the blue-violet emission images captured by smartphone were converted into corresponding gray values by Python-assisted superiority chart algorithm which achieves a real-time rapid quantitative analysis of chlorpyrifos with a detection limit of 0.17 ng mL−1. At the same time, pseudo-color images were also added by Python in “one run” to distinguish images clearly. This sensor detection with Python-assisted analysis platform provides a new perspective on pesticide monitoring and broadens the application prospects in bioanalysis.

A smartphone-integrated nanosensor based on N, P co-doped graphene quantum dots for fluorescence detection of acid red 18 in food

Exploring graphene quantum dots (GQDs) that can be done to contaminant residue detection has been widely concerned. Herein, we develop nitrogen and phosphorus co-doped graphene quantum dots (N, P-GQDs) with a strong green emission (quantum yield: 0.582) by using the resorcinol and phosphonitrilic chloride trimer as precursors via the one-step hydrothermal method. The synthesized N, P-GQDs exhibit excellent photostability and excitation-independent characteristic. Meaningfully, N, P-GQDs exhibit good fluorescence response to acid red 18 (AR18) and possess a good linear relationship over the range of 0–50 μM (the detection limit: 27 nM). Meanwhile, the fluorescence resonance energy transfer is considered as the possible sensing mechanism. Furthermore, a smartphone-assisted sensing platform is designed for the detection of AR18, which can realize on-site quantitative analysis and exhibit excellent on-site detection capability (the detection limit: 43 nM). Therefore, the present strategy has a prospective value for the application in the on-site monitoring of AR18.

One-step reagentless colorimetric analysis platform of biomineralized Ce-UiO-66 for universal detection of biomarkers

Enzymatic colorimetric analysis system is a sensitive and facile onsite quantitative analysis methodology for disease diagnosis, which undergoes a two-step process: (1) H2O2 generation through catalytic oxidation of biomarkers (glucose, uric acid, xanthine, etc.) by corresponding oxidases and (2) catalytic production of reactive oxygen species from H2O2 by peroxidase/peroxidase-like nanozymes to induce color change of chemical chromogenic agents. However, natural enzymes and chemical chromogenic agents are easily oxidized/degraded under harsh environments, thereby being restricted to well-equipped laboratories and seriously limiting their applications. Herein, natural oxidase-encapsulated Ce-UiO-66 (oxidase@Ce-UiO-66), prepared via a facile one-step approach under mild conditions, was exploited to construct a reagentless colorimetric smartphone analysis platform for quantitative analysis of various disease biomarkers. Ce-UiO-66 as carrier of oxidases not only enhanced their stability under long-term storage but also preserved their activity for H2O2 generation through catalytic oxidation of biomarkers under various environments. Subsequently, Ce-UiO-66 served as a dose-dependent chromogenic agent of H2O2 due to the Ce-UiO-66-to-CeO2 phase transition, leading an apparent color evolution from white into orange. Based on the corresponding oxidase@Ce-UiO-66, the smartphone-enabled colorimetric analytic system was developed to achieve a facile, sensitive, and specific onsite detection of glucose (limit of detection (LOD): 35 μM and a wide range of 39–20,000 μM), uric acid (LOD: 21 μM and a wide range of 26–3400 μM), and xanthine (LOD: 3.9 μM and a wide range of 15.6–500 μM), giving their promises for clinic diagnosis.

Simple colorimetric assay using pectin hydrogel reagent coupled with camera-based photometry for trace arsenic determination.

Humans mainly ingest arsenic through contaminated drinking water, causing serious health effects. The World Health Organization (WHO) has set the permissible limit of arsenic in drinking water at 0.01 mg/L and concentrations should be regularly determined to ensure a safe supply. In this study, a leucomalachite green (LMG) pectin-based hydrogel reagent was prepared that selectively reacted with arsenic over other metals including manganese, copper, lead, iron, and cadmium. Pectin, optimized at 0.2% (w/v), was used to form the hydrogel matrix. Arsenic reacts with potassium iodate in sodium acetate buffer medium to liberate iodine that then oxidizes LMG entrapped in pectin hydrogel to form a blue product. Camera-based photometry/ImageJ software was used to monitor the color intensity, eliminating the need for a spectrophotometer. The intensity of gray in the red channel was chosen as optimal for the red, green, and blue (RGB) analysis. The colorimetric assay revealed a dynamic detection range toward arsenic solution standards of 0.003-1 mg/L, covering the WHO recommendation of below 0.01 mg/L arsenic in drinking water. The assay gave recovery rates between 97 and 109% at a 95% confidence interval, with precision of 4-9%. Concentrations of arsenic in the spiked drinking water, tap water, and pond water samples monitored by the developed method agreed well with conventional inductively coupled plasma optical emission spectrometry. This assay showed promise for on-site quantitative analysis of arsenic in water samples.

Assessing the radiation contamination of large areas using advanced technologies.

Military, disaster management and in many cases civilian tasks include surveying of a given section of terrain that is likely to be contaminated with radioactive materials. Such a measurement series can form the basis for the complete recultivation and decontamination of large areas. This survey can take place after an emergency situation. This paper will use concrete surveys to illustrate the efficiency of new measurement technologies and developments. All these technologies aim to carry out radiation reconnaissance tasks as quickly and accurately as possible. Different hot spots were found during on-foot radiation reconnaissance. During in-situ measurements, a Bayesian-based isotope identifying algorithm was used and the measured data were validated with results from gamma spectroscopy in the laboratory. A rapid on-site quantitative analysis was also performed by evaluating the samples taken next to the hot spots. In addition to the measurement, the data were generated and stored in a standard N42 format ideal for data exchange. Many issues were solved like how the measurement data are associated with relevant additional information (e.g. time and coordinate), and how the measurement results can be shared with other partner organisations. Another important consideration was the preparation of the team conducting the measurement. The total cost of the survey was significantly reduced by the fact that the measurement was manageable by one technician and one expert. A quality assurance system had to be established to meetall relevant standards and strict documentation requirements. In addition to operating at high background radiation, these measurements presented additional challenges due to the low activity of hidden and mixed radioactive sources.

A sensing platform for on-site detection of glutathione S-transferase using oxidized Pi@Ce-doped Zr-based metal-organic frameworks(MOFs)

The development of point-of-care testing (POCT) for glutathione S-transferase (GST) is an effective way to establish the mechanism of targeted monitoring of cancer chemotherapy drug metabolism. Assays for GST with high sensitivity as well as on-site screening have been urgently required to monitor this process. Herein, we synthesized oxidized Pi@Ce-doped Zr-based metal–organic frameworks (MOFs) by electrostatic self-assembly between phosphate and oxidized Ce-doped Zr-based MOFs. It was found that the oxidase-like activity of oxidized Pi@Ce-doped Zr-based MOFs was substantially increased after phosphate ion (Pi) assembly. And a stimulus-responsive hydrogel-based kit was constructed by embedding oxidized Pi@Ce-doped Zr-based MOFs into a PVA (polyvinyl alcohol) hydrogel system, we integrated a portable hydrogel kit with a smartphone for real-time monitoring of GST for quantitative and accurate analysis. The color reaction was triggered based on oxidized Pi@Ce-doped Zr-based MOFs with 3,3′,5,5′-tetramethylbenzidine (TMB). However, in the presence of glutathione (GSH), the above color reaction was hindered due to the reducibility of GSH. Catalyzed by GST, GSH can react with 1-chloro-2,4-dinitrobenzo (CDNB) to form an adduct, which caused the color reaction to occur again, resulting in the color response of the kit. In combination with ImageJ software, the kit image information acquired by smartphone could be converted into hue intensity, providing a direct quantitative tool for the detection of GST with a detection limit of 0.19mU·L−1. Based on the advantages of simple operation and cost-effectiveness, the introduction of the POCT miniaturized biosensor platform will meet the requirements of on-site quantitative analysis of GST.

A novel metal-organic framework of Co-hemin for portable and visual colorimetric detection of 2,4-dichlorophenoxyacetic acid.

On-site quantitative analysis of 2,4-dichlorophenoxyacetic acid (2,4-D) is of significant importance for addressing increasing concerns about public health and environmental quality. Here, a novel metal-organic framework (MOF) of Co-hemin is synthesized and first used for on-site colorimetric monitoring of 2,4-D. 2,4-D as an inhibitor of alkaline phosphatase could specifically suppress the production of ascorbic acid, which restrained in situ etching of Co-hemin and further triggered the colorimetric response. In the colorimetric assay, Co-hemin displayed good oxidase-like activity without addition of H2O2, which could avoid the shortcomings of H2O2 such as toxicity and instability. The Co-hemin biosensor exhibited a relatively low detection limit of 33 ng mL-1 for 2,4-D by the UV method. Moreover, a smartphone based RGB analysis system for the sensitive detection of 2,4-D was developed, and exhibited a good linear relationship between the RGB model parameter and the concentration of 2,4-D. The operability and accuracy of the Co-hemin biosensor were confirmed by the quantitative determination of 2,4-D in real samples, such as serum and tap water. Also, the Co-hemin based colorimetric biosensor showed good selectivity and specificity. Moreover, the developed assays displayed good application in constructing complex logic gates. This work not only provided a portable and visual platform for on-site monitoring of 2,4-D, but also expanded application prospects in the field of complex biological analysis.

Aptamer-Based Electrochemical Biosensors for the Detection of Salmonella: A Scoping Review.

The development of rapid, accurate, and efficient detection methods for Salmonella can significantly control the outbreak of salmonellosis that threatens global public health. Despite the high sensitivity and specificity of the microbiological, nucleic-acid, and immunological-based methods, they are impractical for detecting samples outside of the laboratory due to the requirement for skilled individuals and sophisticated bench-top equipment. Ideally, an electrochemical biosensor could overcome the limitations of these detection methods since it offers simplicity for the detection process, on-site quantitative analysis, rapid detection time, high sensitivity, and portability. The present scoping review aims to assess the current trends in electrochemical aptasensors to detect and quantify Salmonella. This review was conducted according to the latest Preferred Reporting Items for Systematic review and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) guidelines. A literature search was performed using aptamer and Salmonella keywords in three databases: PubMed, Scopus, and Springer. Studies on electrochemical aptasensors for detecting Salmonella published between January 2014 and January 2022 were retrieved. Of the 787 studies recorded in the search, 29 studies were screened for eligibility, and 15 studies that met the inclusion criteria were retrieved for this review. Information on the Salmonella serovars, targets, samples, sensor specification, platform technologies for fabrication, electrochemical detection methods, limit of detection (LoD), and detection time was discussed to evaluate the effectiveness and limitations of the developed electrochemical aptasensor platform for the detection of Salmonella. The reported electrochemical aptasensors were mainly developed to detect Salmonella enterica Typhimurium in chicken meat samples. Most of the developed electrochemical aptasensors were fabricated using conventional electrodes (13 studies) rather than screen-printed electrodes (SPEs) (two studies). The developed aptasensors showed LoD ranges from 550 CFU/mL to as low as 1 CFU/mL within 5 min to 240 min of detection time. The promising detection performance of the electrochemical aptasensor highlights its potential as an excellent alternative to the existing detection methods. Nonetheless, more research is required to determine the sensitivity and specificity of the electrochemical sensing platform for Salmonella detection, particularly in human clinical samples, to enable their future use in clinical practice.

A visual and reversible nanoprobe for rapid and on-site determination of hexavalent chromium and lysine based on dual-emission carbon quantum dots coupled with smartphone.

A straightforward, largely instrument-free, smartphone-based analytical strategy for hexavalent chromium and lysine (Lys) on-site detection via exploitation of dual-emission carbon quantum dots (DECQDs) has been demonstrated. DECQDs show dual-emission peaks at 439 and 630nm with the excitation at 375nm. As a dual-mode detection probe, the fluorescence and ultraviolet adsorption spectra of DECQDs vary with hexavalent chromium concentrations. Most importantly, Lys can restore the fluorescence of the hexavalent chromium added DECQD nanoprobe and change the color of the probe under natural light. At the same time, based on the participation of smartphones, the prepared DECQD probes favor the establishment of visual smart sensors that can also be used for the in-situ detection of targets. The on-site quantitative analysis exhibited a linear range of 5.3-320μM with a detection limit of 1.6μM towards Cr(VI) and the differentiation of Lys variation from 1 to 75mM with a detection limit of 0.3mM. The probe has beenapplied for the first time to enable vision-based colorimetric in complex samples such as water, milk and egg. The recoveries of Cr(VI) and Lys in real samples were between 90 and 104%, and the relative standard deviation (RSD) was as low as 0.4%. This work offers new perspectives for fundamental understanding and new design of functional luminescent materials that areapplicable for food-safetyand rapid and intelligent inspection. A straightforward, large instrument-free, smartphone-based analytical strategy with dual-emission carbon quantum dots was developed for hexavalent chromium and Lys on-site detection via fluorescent and colorimetric twofold readout measure.

High selective inner filter effect based method and its application in 2,4,6-trinitrophenol detection

We develop an upgraded inner filter effect (IFE) based sensing method that is able to distinguish interfering compounds from an analyte, even though the interferents absorb at the excitation wavelength, as long as they have different molar attenuation coefficients (ε) from the analyte's. As a proof-of-principle, we explore the selective 2,4,6-trinitrophenol (TNP) sensing method which is the best one in terms of selectivity in all IFE-based methods. The method is successfully applied to detect TNP in real water samples and to explore a paper strip test for TNP. Furthermore, combining the test paper with the color recognizer App of a smartphone, a low-cost, real-time, and on-site quantitative analysis method of TNP is acquired.

Amines-mediated β-glucose pentaacetate to generate photoluminescent polymer-carbon nanodots for visual monitoring the freshness of shrimp

In this paper, a portable fluorescence-based functional hydrogel loaded with β-d-glucose pentaacetate (β-D-GP) is designed for high-sensitive quantification of amine vapor and visual monitoring of freshness of shrimp. We found for the first time that amine vapor can mediate β-D-GP to generate photoluminescent polymer-carbon nanodots (PCNDs) with good optical properties. On this basis, a functional hydrogel sensing platform is simply formed by solidifying β-D-GP in agarose hydrogels. When exposure to the volatile amines released from the spoilage of shrimp, β-D-GP in hydrogel is immediately mediated by amines to generate PCNDs, resulting in obvious fluorescence-based color variation of functional hydrogel. Notably, a smartphone is used to obtain digital photographs and RGB (Red/Green/Blue) information of hydrogels for on-site quantitative analysis. The gray value of G/(R + B) of hydrogel shows good linearity with trimethylamine (TMA) vapor concentration in the range of 0–59.49 × 10−9 mol dm−3. More importantly, the G/(R + B) value of functional hydrogel is successfully used to assess the freshness of shrimp. Consequently, this strategy provides a low-cost, portable fluorescence analysis device with promising applications in achieving high-sensitive, nondestructive, and on-site food safety evaluation of animal-derived aquatic products.

Paper-based multicolor sensor for on-site quantitative detection of 2,4-dichlorophenoxyacetic acid based on alkaline phosphatase-mediated gold nanobipyramids growth and colorimeter-assisted method for quantifying color

On-site quantitative analysis of pesticides is important for food safety. Colorimetric gold nanobipyramids (AuNBPs) sensors are powerful methods for on-site detection. However, a single quantitative method and the instability of AuNBPs in solution limit the practicability of those sensors. Here, a paper-based multicolor AuNBPs sensor involved a colorimeter-assisted method for quantifying color was developed for quantitative detection of 2,4-dichlorophenoxyacetic acid (2,4-D), a common herbicide. The novelty of this study lies in developing a general paper-based quantitative on-site method (PQOM) for colorimetric AuNBPs sensors. Firstly, a paper-based analytical device (PAD) consisting of a nylon membrane, absorbent cotton layers, and two acrylic plates was fabricated to deposit AuNBPs. We demonstrated the PAD could improve the stability of AuNBPs and the detection sensitivity of AuNBPs sensors. Then, a handheld colorimeter was first used to quantify the color change of AuNBPs on the PAD based on the CIELab color space. Finally, as proof of concept, the PQOM was successfully employed to quantify 2,4-D by combining with an alkaline phosphatase-mediated AuNBPs growth method. In this method, 2,4-D specifically inhibited alkaline phosphatase activity to suppress the generation of l-ascorbic acid, thereby mediating AuNBPs growth. The developed sensor exhibited seven 2,4-D concentration-related colors and detected as low as 50 ng mL−1 2,4-D by naked-eye observation and 18 ng mL−1 2,4-D by a colorimeter. It was applied to detect 2,4-D in the spiked rice and apple samples with good recovery rates (91.8–112.0%) and a relative standard deviation (n = 5) < 5%. The success of this study provides a sensing platform for quantifying 2,4-D on site.

Insect Protein Content Analysis in Handcrafted Fitness Bars by NIR Spectroscopy. Gaussian Process Regression and Data Fusion for Performance Enhancement of Miniaturized Cost-Effective Consumer-Grade Sensors.

Future food supply will become increasingly dependent on edible material extracted from insects. The growing popularity of artisanal food products enhanced by insect proteins creates particular needs for establishing effective methods for quality control. This study focuses on developing rapid and efficient on-site quantitative analysis of protein content in handcrafted insect bars by miniaturized near-infrared (NIR) spectrometers. Benchtop (Büchi NIRFlex N-500) and three miniaturized (MicroNIR 1700 ES, Tellspec Enterprise Sensor and SCiO Sensor) in hyphenation to partial least squares regression (PLSR) and Gaussian process regression (GPR) calibration methods and data fusion concept were evaluated via test-set validation in performance of protein content analysis. These NIR spectrometers markedly differ by technical principles, operational characteristics and cost-effectiveness. In the non-destructive analysis of intact bars, the root mean square error of cross prediction (RMSEP) values were 0.611% (benchtop) and 0.545–0.659% (miniaturized) with PLSR, and 0.506% (benchtop) and 0.482–0.580% (miniaturized) with GPR calibration, while the analyzed total protein content was 19.3–23.0%. For milled samples, with PLSR the RMSEP values improved to 0.210% for benchtop spectrometer but remained in the inferior range of 0.525–0.571% for the miniaturized ones. GPR calibration improved the predictive performance of the miniaturized spectrometers, with RMSEP values of 0.230% (MicroNIR 1700 ES), 0.326% (Tellspec) and 0.338% (SCiO). Furthermore, Tellspec and SCiO sensors are consumer-oriented devices, and their combined use for enhanced performance remains a viable economical choice. With GPR calibration and test-set validation performed for fused (Tellspec + SCiO) data, the RMSEP values were improved to 0.517% (in the analysis of intact samples) and 0.295% (for milled samples).

Smartphone-Assisted Robust Sensing Platform for On-Site Quantitation of 2,4-Dichlorophenoxyacetic Acid Using Red Emissive Carbon Dots.

On-site quantitative analysis of pesticide is of significant importance for addressing serious public health issues in clinical, food, and environmental settings. Herein, we designed a novel smartphone-assisted sensing platform for on-site monitoring of 2,4-dichlorophenoxyacetic acid (2,4-D) based on carbon dots/cobalt oxyhydroxide nanosheet (CDs/CoOOH) composite. In this work, a red emissive CDs/CoOOH composite was proposed as a signal indicator for shielding background interference, enhancing anti-interference capability. 2,4-D as an inhibitor of alkaline phosphatase could specifically suppress the production of ascorbic acid, which restrained in situ etching of the CDs/CoOOH composite and further triggered the fluorescence response of the biosensor. By employing a lab-on-smartphone based device and self-designed application software, the fluorescence image was directly captured and analyzed with a sensitive detection limit of 100 μg L-1 for 2,4-D. Merging the CDs/CoOOH composite-based fluorometric system with the smartphone-assisted optical reader, such a cost-effective and portable platform provided a new sight for on-site monitoring of pesticide and expanded application prospect in the field of biological analysis.

Convenient environmentally friendly on-site quantitative analysis of nitrite and nitrate in seawater based on polymeric test kits and smartphone application.

Nowadays, nitrate (NO3-) and nitrite (NO2-) in aquatic ecosystems have increased due to various anthropogenic activities leading to deterioration of the ecosystem and can accelerate eutrophication. A Griess reagent-doped hydrogel test kit and a zinc powder-doped starch film were thus developed for on-site quantitative analysis of nitrate and nitrite. A clear colorless hydrogel tablet (diameter 1.5cm 2mm thickness) turned pink-violet after reacting with a standard solution of nitrite while the gray zinc-doped starch film (8.36μm thickness) fabricated on the inner lid of small plastic tube was used for the in-tube reduction of nitrate to be nitrite. The use of this film followed by nitrite testing using the hydrogel tablet was used as a nitrate test. Both the materials developed were used in conjunction with digital image colorimetry (DIC) using smartphone application for on-site quantitative analysis of nitrite and nitrate. Good linearity (R2>0.99) ranges of 0.05 to 5mgL-1 for nitrite and 1 to 50mgL-1 for nitrate were obtained and detection limits of 50μgL-1 for nitrite and 0.32mgL-1 for nitrate were achieved. Good accuracy was obtained in terms of a relative error in a range of 0.75 to 2.68% with inter-day precision in a range of 0.20 to 0.50%RSD (n=3). Quantitative analysis of nitrate and nitrite in 10 seawater samples taken in Phuket was in good agreement with the standard method (95% confidence level). Since the method developed employs test kits synthesized using biodegradable polymers and DIC using a smartphone application, it will allow the rapid on-site quantitative detection of nitrate and nitrite in a more convenient and environmentally friendly system.

Indirect Competitive Immunoassay on a Blu-ray Disc for Digitized Quantitation of Food Toxins.

We report herein a Blu-ray disc technology enabled immunoassay (namely, assay-on-a-Blu-ray) protocol for the quantitation of food toxins. In particular, commercial Blu-ray discs (BDs) are activated as substrates to create indirect competitive immunoassays with the aid of microfluidic channel plates for the quantitation of aflatoxins; an unmodified Blu-ray drive is employed to read the digitized signal (error counts generated from gold/silver-particle-enhanced binding sites); and a free disc-quality control software is adapted to process the raw data. The performance of this BD-based digital detection platform has been tested for the quantitation of aflatoxin B1 (AFB1) in spiked corn samples and validated with standard high-performance liquid chromatography measurements. The detection limit attained is as low as 0.27 ppb with a dynamic response range up to 200 ppb, which meets the standards established by government agencies worldwide for food products. We truly believe that the application potential of such a BD-technology-based, portable device for multiplex on-site quantitative analysis of food products as well as environmental and biomedical samples in real time is unlimited.