Novel disposable and portable 3D-printed electrochemical apparatus for fast and selective screening of 25E-NBOH in forensic samples

The advent of new psychoactive substances (NPS) has caused enormous difficulty for legal control since they are rapidly commercialized, and their chemical structures are routinely altered. In this aspect, derivatives phenethylamines, such as 25E-NBOH, have received great attention in the forensic scenario. Hence, we propose portable and cost-effective (U$ 5.00) 3D-printed devices for the electrochemical screening of 25E-NBOH for the first time. The cell and all electrodes were printed using acrylonitrile butadiene styrene filament (insulating material) and conductive filament (graphite embedded in a polylactic acid matrix), respectively, both by the fused deposition modeling (FDM) 3D printing technique. The electrochemical apparatus enables micro-volume analysis (50-2000 μL), especially important for low sample volumes. A mechanistic route for the electrochemical oxidation of 25E-NBOH is proposed based on cyclic voltammetric data, which showed two oxidation processes around +0.75 V and +1.00 V and a redox pair between +0.2 and -0.2 V (vs. graphite ink pseudo-reference). A fast and sensitive square-wave voltammetry method was developed, which exhibited a linear working range from 0.85 to 5.1 μmoL-1, detection limit of 0.2 μmol L-1, and good intra-electrode precision (n = 10, RSD <5.3 %). Inter-electrode measurements (n = 3, RSD <9.8 %) also attested that the electrode production process is reproducible. Interference tests in the presence of other drugs frequently found in blotting paper indicated high selectivity of the electrochemical method for screening of 25E-NBOH. Screening analysis of blotting paper confirmed the presence of 25E-NBOH in the seized samples. Moreover, a recovery percentage close to 100 % was found for a spiked saliva sample, suggesting the method's usefulness for quantitative purposes aimed at information on recent drug use.

Miniaturized paper-based analytical device for the portable analysis of phyto-cannabinoids in plant and oral fluids

In this work, a low-cost and eco-friendly paper-based analytical device (PAD) method is described for the determination of phyto-cannabinoids in cannabis and oral fluids based on a simple colorimetric reaction. The PAD was able to distinguish tetrahydrocannabinol (THC)- and cannabidiol (CBD)-rich plant samples by using 4-aminophenol (4-AP) and later on to quantify total phyto-cannabinoid content (THC + CBD + CBN) in plant and oral fluids by using the Fast Corinth V reagent. The chemical and physical properties regarding paper type and reagent concentration in the PAD were optimized to achieve the best analytical performance. After that, analytical features were obtained, including a linear range of 0.01-0.1 mg mL-1, a limit of detection (LOD) of 0.003 mg mL-1, and a suitable precision, expressed as relative standard deviation (RSD) lower than 10%. Furthermore, no significant interferences were observed in colorimetric reactions when tea, herbs, and drug samples were analyzed. Additionally, the PAD proved color stability up to 1 month after the sampling at 25 °C. The developed PAD was suitable for determining total phyto-cannabinoid content in plants and oral fluids, obtaining good results compared to GC-MS. Overall, this method showed good reliability resulting in an operational on-site device for drug monitoring.

3D-printed electrochemical cells with laser engraving: developing portable electroanalytical devices for forensic applications

A new electrochemical device fabricated by the combination of 3D printing manufacturing and laser-generated graphene sensors is presented. Cell and electrodes were 3D printed by the fused deposition modeling (FDM) technique employing acrylonitrile butadiene styrene filament (insulating material that composes the cell) and conductive filament (lab-made filament based on graphite dispersed into polylactic acid matrix) to obtain reference and auxiliary electrodes. Infrared-laser engraved graphene, also reported as laser-induced graphene (LIG), was produced by laser conversion of a polyimide substrate, which was assembled in the 3D-printed electrochemical cell that enables the analysis of low volumes (50-2000 μL). XPS analysis revealed the formation of nitrogen-doped graphene multilayers that resulted in excellent electrochemical sensing properties toward the detection of atropine (ATR), a substance that was found in beverages to facilitate sexual assault and other criminal acts. Linear range between 5 and 35 μmol L-1, detection limit of 1 μmol L-1, and adequate precision (RSD = 4.7%, n = 10) were achieved using differential-pulse voltammetry. The method was successfully applied to beverage samples with recovery values ranging from 80 to 105%. Interference studies in the presence of species commonly found in beverages confirmed satisfactory selectivity for ATR sensing. The devices proposed are useful portable analytical tools for on-site applications in the forensic scenario.

A critical review of on-site inorganic arsenic screening methods

Approximately 94 to 220 million people worldwide are at risk of drinking well water containing arsenic > 10 µg/L, the WHO guideline value. To identify non-compliant domestic wells, assess health risks and reduce exposure, accurate and rapid on-site inorganic arsenic screening methods are desirable because all domestic wells worldwide need to be tested. Here, the principles, advantages and limitations of commonly used colorimetry, electrochemistry, and biosensing methods are critically reviewed, with the performance compared with laboratory-based benchmark methods. Most commercial kits are based on the classic Gutzeit reaction. Despite being semi-quantitative, the more recent and more expensive products display improved and acceptable accuracy and shorter testing time (∼10 min). Carried out by trained professionals, electrochemical methods are also feasible for on-site analysis, although miniaturization is desirable yet challenging. Biosensing using whole bacterial cells or bio-engineered materials such as aptamers is promising, if incorporated with function specific nanomaterials and biomaterials. Since arsenic is frequently found as arsenite in reducing groundwater and subject to oxidation during sampling, transportation and storage, on-site separation and sample preservation are feasible but the specific methods should be chosen based on sample matrix and tested before use. To eliminate arsenic exposure among hundreds of millions of mostly rural residents worldwide, we call for concerted efforts in research community and regulatory authority to develop accurate, rapid, and affordable tests for on-site screening and monitoring of arsenic in drinking water. Access to affordable testing will benefit people who are socioeconomically disadvantaged.

Lab at home: a promising prospect for on-site chemical and biological analysis

The continuing pursuit for a healthy life has led to the urgent need for on-site analysis. In response to the urgent needs of on-site analysis, we propose a novel concept, called lab at home (LAH), for building automated and integrated total analysis systems to perform chemical and biological testing at home. It represents an emerging research area with broad prospects that has not yet attracted sufficient attention. In this paper, we discuss the urgent need, challenges, and future prospects of this area, and the possible roadmap for achieving the goal of LAH has also been proposed.

Colorimetric analysis based on solid-phase extraction with sedimentable dispersed particulates: demonstration of concept and application for on-site environmental water analysis

A novel simple and functional colorimetric methodology for on-site environmental water analysis was proposed. This method combines coloration of the analyte and extraction of the colored species on dispersed particulates during their sedimentation in the same container. The whole analysis can be performed within 15 min by comprising the addition of 1 mL of sample solution into a 1.5-mL microtube containing the powders of coloring reagents and the sedimentable fine particulates as an adsorbent. The analyte is determined by comparing the sediment color with the standard color by visual inspection or the color information of the photo image. The potential of this methodology was demonstrated through developing colorimetry for Fe²⁺ with o-phenanthroline, NO₂^- by azo-dye formation, HCHO by the MBTH method, and PO₄^3- by the 4-aminoantipyrine method based on the enzyme reactions. The material, size, amount of the adsorbent particles, and other conditions were optimized for each analytes. The advantages of the methodology were as follows: high sensitivity, easy controllability of the sensitivity over the wide range by the amount, size, and material of the particulates, lower interference from the colored matrix components due to obtaining the color data from not the aqueous phase but the sedimented particulates, and acceleration of the color development rate by the particulates as seen in NO₂^- determination as consequence shorten the operation time. A simple device equipped with twin cells was proposed for on-site analysis which contains two successive different coloring operations. The developed methods were successfully applied to the environmental water samples with the good agreement of the results with those by the usual instrumental methods.

Development of a versatile smartphone-based environmental analyzer (vSEA) and its application in on-site nutrient detection

The citizen-science-based environmental survey can benefit from the smartphone technology used in chemical and biological sensing of a wide range of analytes. Quantification by smartphone-based colorimetric assays is being increasingly reported, however, most of the quantification uses empirical formula or complex exhaustive methods. In this study, a versatile and robust algorithm is proposed to overcome these limitations. A model is established to simulate and analyze the conversion process from the camera's spectral information into RGB (Red, Green, Blue) color information. Moreover, the feasibility of the algorithm for the quantification of different analytes is also explored. Based on this algorithm, a versatile smartphone-based environmental analyzer (vSEA) is built and its reliability, versatility, and analytical performance are comprehensively optimized. The good linearity (R² ≥ 0.9954) and precision (relative standard deviations < 5.3%) indicates that the vSEA is accurate enough to quantify the nutrients in most natural waters. Furthermore, the vSEA is used for the field measurement of five important nutrients, and the results show no significant difference compared to conventional methods. The vSEA offers a simpler and easier method for the on-site measurement of nutrients in natural water bodies, which can aid in the emergency monitoring of aqueous ecosystems and the performance of citizen-science-based research.

Total protein assay by PCA-based RGB-spectrum conversion methods with smartphone-acquired digital images

Total protein concentrations in the aqueous solutions were determined from the absorption spectra reproduced from smartphone-captured digital color images. We employed two different procedures for protein determination: the pyrogallol red molybdate method and Bradford's method. The principal-component-analysis-based reproduction process, which was previously reported by our research group, enabled the conversion of RGB values to score values for a linear combination of loading vectors to generate reproduced absorption spectra. The reproduced spectra were identical to those measured using a commercially available spectrophotometer. The total protein assays of commercial soymilk and human serum samples were carried out with both coloration reagents, and the obtained results were in good agreement with those attained using a conventional spectrophotometer. These results show that the proposed method enables smartphone-based ratiometric analysis of real samples without requiring any monochromating equipment.

Compact Eight-Channel Light-Sensing System for Bioassays

The present protocol introduces a new instrumental setup as a luminometer to simultaneously measure eight light samples with high sensitivity. The system consists of 8-channel photomultiplier tubes (8-PMTs) with different sensitivities to light. Therefore, it is critical to normalize the sensitivities of PMTs to light samples and integrate them as a system. We first introduce how to normalize the diverse light sensitivity among the PMTs using placental alkaline phosphatase (PLAP) as a model chemiluminescence light source. The normalized BBI system shows a statistically strong linear correlation graph to photon counts. The biomedical utility of this system is exemplified by (i) determining the alkaline phosphatase (AP) activities in mouse plasma samples as a cancer biomarker and (ii) diagnosing metastatic tissues during cancer progression using bioluminescent reporter.

Ratiometric fluorescent probe for the on-site monitoring of coexisted Hg2+ and F- in sequence

The monitoring of mercury and fluoride ions (Hg²⁺ and F^-) has aroused wide concerns owing to the high toxicity of Hg²⁺ and the duplicitous nature of F^- to human health. As far as we known, more than 100 million people in poverty-stricken areas are still at high risk of being over-exposed to Hg²⁺ and F^- via drinking water. Simple and cost-effective luminescent methods are highly promising for on-site water monitoring in rural areas. However, the development of multipurpose luminescent probes that are accurate and sensitive remains challenging. Herein, a new strategy for rationally designing a multipurpose ratiometric probe is present. The obtained probe is consisted of two emission units with energy transfer between them, which exhibit high coordination affinities to the two coexisted toxic targets (Hg²⁺ and F^-), respectively. Thus, two distinct routes for efficiently modulating the energy transfer in the probe are present to trigger the responses to the two targets in sequence. By detecting the shift of the emission color with a smartphone, an on-site water monitoring method is successfully established with the detection limits as low as 2.7 nM for Hg²⁺ and 1.9 μM for F^-. The present study can expend the toolbox for water monitoring in rural regions.

Development of a simple and rapid screening method for the detection of 1-(3-chlorophenyl)piperazine in forensic samples

1-(3-chlorophenyl) piperazine (mCPP) is a synthetic drug with hallucinogenic effects that has often been found in seized samples. In this context, easy to use point-of-care tests can be of great value in preliminary forensic analysis. Herein, we proposed a simple, fast, and portable electrochemical method for the detection of mCPP in seized samples. The method is based on the use of disposable screen-printed carbon electrodes (SPCE) and rapid screening procedures by square-wave voltammetry using minimal sample sizes (100 μL). mCPP showed an irreversible electrochemical oxidation process at +0.65 V on SPCE (vs Ag) using 0.04 mol L^-1 Britton Robinson (BR) buffer solution (pH 7) as the supporting electrolyte. The proposed method exhibited a linear correlation (r = 0.998) between peak current and mCPP concentration in the range of 1-30 μmol L^-1 (LOD = 0.1 μmol L^-1). Interference studies were performed for adulterants and other classes of drugs of abuse, which can also be found in seized samples containing mCPP, such as caffeine, amphetamine, methamphetamine, 1-benzylpiperazine, 3,4-methylenedioxymethamphetamine, methylone, mephedrone, ethylone and 3, 4-methylenedioxypyrovalerone. The developed method presents great potential as a rapid and simple screening tool to detect mCPP in forensic samples.

Open-source all-in-one LabToGo Office Chromatography

Print and media technologies were used uncommonly in the field of chromatography and explored in application to create a miniaturized all-in-one LabToGo system. This novel research field termed Office Chromatography (OC) uses additive manufacturing in terms of 3D printing of operational parts as well as open-source hard- and software. The OCLab2 presented here has been considerably extended in its functionalities. For inkjet printing of solutions, a newly designed printhead was manufactured controlled by a self-constructed ink-jet board, allowing to check the nozzles' resistance heating circuit. Plate heating was newly integrated, especially favorable for the demonstrated application of higher volumes of aqueous samples. The UV/Vis/FLD plate images were captured by a Raspberry Pi V2 camera module under illumination by novel light emitting diodes (LEDs) for highly selective RGBW color (Vis), UVC 278-nm (UV) and UVA 366-nm (FLD) detection, installed in a newly created miniature cabinet to protect from extraneous light. The spectral separation of differently colored food dyes was achieved by the fully addressable driver controlled RGBW LEDs. The software was newly written in R to speed-up the processes, supported by the new Raspberry Pi 4B computer with 4 GB RAM. The analysis of Stevia leaves for steviol glycosides yielded results comparable to the status quo. Different water samples were analyzed for bioactive compounds. Thereby, compounds of general cytotoxicity were effect-directed detected by bioluminescent A. fischeri bacteria. It allowed the bioanalytical screening for potential risks in tap water, surface waters, rain water, landfill leachates and biogas slurries.

On-site contactless surface analysis of modern paintings from Galleria Nazionale (Rome) by reflectance FTIR and Raman spectroscopies

Seven artworks representing the diversity of paints used around the 1960s and created by German and Italian painters (J. Albers, A. Bonalumi, L. Boille, T. Scialoja and M. Schifano) were studied on-site at the Galleria Nazionale d'Arte Moderna (Rome) with mobile instruments. We present a methodology based on Specular Reflectance Infrared Spectroscopy (SR-FTIR) adapted to unvarnished paintings. Complementary measurements have been performed by Raman spectroscopy. Characteristic bands regarding as-recorded infrared reflectance spectra and Kramers-Kronig Transformation-converted absorbance spectra are identified according to literature and reference spectra recorded on representative commercially available paints. To distinguish the different binders by SR-FTIR, we propose spectroscopic markers as the comparison of the intensity of carbonyl band around 1730-1735 cm^-1 with bands at ~1160 (for acrylic), ~1230 (for PVAc), and 1270 cm^-1 (for alkyds). On the other hand, oil/resin binders are characterized by intense and thin νCH₂, νCH₃ IR absorption bands around 2920-2850 cm^-1, combined with an intense 1260 cm^-1 band and a characteristic concave cradle shape (between ca. 1750 and 1260 cm^-1). The results obtained establish the relevance of the implemented mobile non-invasive infrared spectroscopy analytical approach by successfully identifying acrylic, vinylic, oil media and enamel paints, with or without opacifiers, which is supplemented by Raman analyses for pigment identification.

Development of an easy portable procedure for on-site determination of mercury and methylmercury

A portable measurement and speciation procedure for inorganic mercury (Hg_IN) and methylmercury (CH₃Hg) was developed. A portable sample pretreatment was optimized to determine total mercury content. A new home-made sorbent (CYXAD, CHYPOS 101 modified Amberlite XAD), was prepared to separate Hg_IN and CH₃Hg. Mercury species were determined using square wave anodic stripping voltammetry (SW-ASV) with a solid gold electrode (SGE) and using a portable potentiostat. A certified reference material, five freeze-dried samples and three fresh samples were analysed with conventional voltammetric analyzer, after dissolution of the samples in microwave oven, and with a portable potentiostat after the mild eating procedure. The results obtained by SW-ASV were compared with those obtained using Direct Mercury Analyser (DMA). The quantification with the portable method is comparable to that obtained with the DMA. Retention tests showed the selectivity of CYXAD for Hg_IN, its stability and the possibility to re-use the same aliquot of resin.

A filtration-assisted approach to enhance optical detection of analytes and its application in food matrices

Analysis of target analytes in food and environmental samples often required sophisticated instrumentation, which restrains the accessibility and portability of the analysis. Herein, we developed an instrument-free approach for rapid quantification of target analytes. The reported filtration-assisted approach enables image analysis of aggregates formed via interaction between analytes and silver nanoparticles (AgNPs). Two model analytes were chosen for aggregating AgNPs, potassium phosphate for neutralizing the charges and a di-thiol molecule (2,2'-(ethylenedioxy) diethanethiol (EDT)) for cross-linking. The mixtures of AgNPs and analytes were filtered onto filter membranes and analyzed using grey color intensity analysis. Based on the AgNPs-EDT platform, we demonstrated the detection of 1 µg/mL acrylamide in instant coffee and biscuit matrices was achievable. The filtration-assisted method provides a simple, fast and inexpensive approach for optical detection and quantification of analytes in food matrices.

On-site testing of multiple drugs of abuse in urine by a miniature dual-LIT mass spectrometer

There is an increasing need for rapid and on-site detection of emerging drugs of abuse. In this work, we developed a method using a miniature dual-LIT (linear ion trap) mass spectrometer recently developed with comprehensive tandem mass spectrometry analysis capability, for qualitative and quantitative analysis of multiple drugs of abuse. Paper-capillary spray cartridges were used with related workflow established to simplify overall analysis procedure. Quantitation of ketamine and methamphetamine was achieved by beam-type collision-induced dissociation on the miniature dual-LIT mass spectrometer and a linear concentration range of 100-5000 ng/mL was obtained. The system has been applied in analysis of real urine samples from individuals addicted to morphine and methamphetamine use. The changes of the ratio of cocaine to its metabolite benzoylecgonine were also explored to estimate the time of cocaine intaking.

Investigation of midazolam electro-oxidation on boron doped diamond electrode by voltammetric techniques and density functional theory calculations: Application in beverage samples

Midazolam (MID) is a sedative drug which can be added in beverage samples as drug-facilitated-sexual assault (date rape drug). This type of drug has short half-life in biological fluids (not detectable) which often prevents the correlation between drug abuse and crime. In this work, we described a simple and low-cost method for fast screening and selective determination of MID in beverage samples (vodka, whiskey and red wine). For the first time, the electrochemical oxidation of MID was used for this purpose. The oxidation mechanism was studied using electrochemical techniques (cyclic and square-wave voltammetry) and computational simulations (density functional theory calculations). Differential-pulse voltammetry, boron-doped diamond electrode (BDDE), and Britton-Robinson (BR) buffer (pH = 2) were selected as electrochemical analysis technique, working electrode and supporting electrolyte, respectively. Different linear response ranges (4-25 μmol L^-1 with r = 0.9972; 1-10 μmol L^-1 with r = 0.9951; 1-15 μmol L^-1 with r = 0.9982) and limits of detection (0.46, 0.43 and 0.33 μmol L^-1) were obtained for the analysis of vodka, whisky, and red wine solutions, respectively. The precision and accuracy were satisfactory considering the low relative standard deviation values (RSD < 6.3%, n = 15) and minimal sample matrix effects (recovery values between 87 and 103%).

A Fluorescence Sensing Method with Reduced DNA Typing and Low-Cost Instrumentation for Detection of Sample Tampering Cases in Urinalysis

This work presents a method to unequivocally detect urine sample tampering in cases where integrity of the sample needs to be verified prior to urinalysis. The technique involves the detection of distinct patterns of a triplex short tandem repeats system in DNA extracted from human urine. The analysis is realized with single-dye fluorescence detection and using a regular smartphone camera. The experimental results had demonstrated the efficacy of the analytical approach to obtaining distinct profiles of amplicons in urine from different sample providers. Reproducibility tests with fresh and stored urine have revealed a maximum variation in the profiles within an interval of 5 to 9%. Cases of urine sample tampering via mixture were simulated in the study, and the experiments have identified patterns of mixed genotypes from dual mixtures of urine samples. Moreover, sample adulteration by mixing a non-human fluid with urine in a volume ratio over 25% can be detected. The low cost of the approach is accompanied by the compatibility of the technique to use with different DNA sample preparation protocols and PCR instrumentation. Furthermore, the possibility of realizing the method in an integrated microchip system open great perspectives to conducting sample integrity tests at the site of urine sample reception and/or at resource-limited settings.

On-spot surface enhanced Raman scattering detection of Aflatoxin B1 in peanut extracts using gold nanobipyramids evenly trapped into the AAO nanoholes

Simple, rapid, convenient, and economical surface enhanced Raman scattering (SERS) substrate is developed for on-site evaluation of Aflatoxin B₁ (AFB₁) in food matrix using handheld Raman Spectrometer. Self-assembly of gold nanobipyramids (Au NBPs) into the nanoholes of anodic aluminum oxide (AAO) template/pattern using 'drop-dry' approach provides a reliable pathway for the rapid fabrication of highly active and uniform SERS substrate. It shows enhanced and reproducible SERS signals towards the probe molecule, 4-aminothiophenol (4-ATP) with a relative standard deviation (RSD) of less than 10% and an average enhancement factor (EF) of 1 × 10⁸. For practical application, the proposed method is demonstrated for the detection of aflatoxin B₁ (AFB₁) in peanut extracts. The results show that the AFB₁ in peanut extracts can be identified within 1 min, with a limit of detection of 0.5 μg/L. Compared with conventional ELISA based AFB₁ analysis, our method is much more efficient (1 min versus >30 min).

Quantitative Raman assays for on-site analysis of stockpiled drugs

We present a rapid Raman assay for on-site analysis of stockpiled drugs in aqueous solution. This approach was tested on Tamiflu (oseltamivir phosphate). Tamiflu is a drug approved by the FDA for treatment of influenza and is the most common antiviral included in stockpiles for use in the event of a national emergency. Rapid assays were performed on three concentrations (30, 45, and 75 mg) of oseltamivir using three different portable & handheld Raman instruments. PLS regression models were developed to establish a calibration curve and applied to the Tamiflu samples. Raman assay values were compared against the standard HPLC assay to demonstrate the viability of this approach, yielding an average assay value within 0.3% of that obtained from the HPLC analysis for the 35 different capsules analyzed. The Raman method demonstrates the potential for rapid screening of stockpiled pharmaceuticals on-site using portable Raman instrumentation and readily available consumables for sample preparation. In addition to routine screening to ensure product quality past the expiration date, this approach could also be used to assist in rapid deployment of such medications in the case of a national emergency.

Multi-capillary Column Ion Mobility Spectrometry of Volatile Metabolites for Phenotyping of Microorganisms

Rational strain engineering requires solid testing of phenotypes including productivity and ideally contributes thereby directly to our understanding of the genotype-phenotype relationship. Actually, the test step of the strain engineering cycle becomes the limiting step, as ever advancing tools for generating genetic diversity exist. Here, we briefly define the challenge one faces in quantifying phenotypes and summarize existing analytical techniques that partially overcome this challenge. We argue that the evolution of volatile metabolites can be used as proxy for cellular metabolism. In the simplest case, the product of interest is a volatile (e.g., from bulk alcohols to special fragrances) that is directly quantified over time. But also nonvolatile products (e.g., from bulk long-chain fatty acids to natural products) require major flux rerouting that result potentially in altered volatile production. While alternative techniques for volatile determination exist, rather few can be envisaged for medium to high-throughput analysis required for phenotype testing. Here, we contribute a detailed protocol for an ion mobility spectrometry (IMS) analysis that allows volatile metabolite quantification down to the ppb range. The sensitivity can be exploited for small-scale fermentation monitoring. The insights shared might contribute to a more frequent use of IMS in biotechnology, while the experimental aspects are of general use for researchers interested in volatile monitoring.

Droplet-counting Microtitration System for Precise On-site Analysis

A new microtitration system based on the counting of titrant droplets has been developed for precise on-site analysis. The dropping rate was controlled by inserting a capillary tube as a flow resistance in a laboratory-made micropipette. The error of titration was 3% in a simulated titration with 20 droplets. The pre-addition of a titrant was proposed for precise titration within an error of 0.5%. The analytical performances were evaluated for chelate titration, redox titration and acid-base titration.

A smartphone-based colorimetric reader coupled with a remote server for rapid on-site catechols analysis

The search of a practical method to analyze cis-diol-containing compounds outside laboratory settings remains a substantial scientific challenge. Herein, a smartphone-based colorimetric reader was coupled with a remote server for rapid on-site analysis of catechols. A smallest-scale 2×2 colorimetric sensor array composed of pH indicators and phenylboronic acid was configured. The array was able to distinguish 13 catechols at 6 serial concentrations, through simultaneous treatment via principal component analysis, hierarchical cluster analysis, and linear discriminant analysis. After both the discriminatory power of the array and the prediction ability of the partial least squares quantitative models were proved to be predominant, the smartphone was coupled to the remote server. All the ΔRGB data were uploaded to the remote server wherein linear discriminant analysis and partial least squares processing modules were established to provide qualitative discrimination and quantitative calculation, respectively, of the analytes in real time. The applicability of this novel method to a real-life scenario was confirmed by the on-site analysis of various catechols from a water sample of the Yangtze River; the feedback result in the smartphone showed the method was able to identify the catechols with 100% accuracy and predict the concentrations to within 0.706-2.240 standard deviation.

Evaluation of a multi-fiber exchange solid-phase microextraction system and its application to on-site sampling

Until recently, multiple solid-phase microextraction fibers could not be automatically desorbed in a single gas chromatographic sequence without manual intervention from an operator. This drawback had been a critical issue, particularly during the analysis of numerous on-site samples taken with various fiber assemblies. Recently, a Multi-Fiber Exchange system, designed to overcome this flaw found in other commercially available autosamplers, was released. In the current research, a critical evaluation of the Multi-Fiber Exchange system performance in terms of storage stability and long-term operation is presented. It was established in the course of our research that the Multi-Fiber Exchange system can operate continuously and precisely for multiple extraction/injection cycles. However, when the effect of residence time of commercial fibers on the Multi-Fiber Exchange tray was evaluated, results showed that among the evaluated fiber coatings, Carboxen/polydimethylsiloxane was the only coating capable of efficient storage on the tray for up to 24 h after field sampling without suffering significant loss of analytes (≤10% for benzene, toluene, ethylbenzene, o-xylene, decane, and limonene). Additionally, the system capability for high-throughput analysis was demonstrated by the unattended desorption of multiple fibers after on-site sampling of toluene, indoor air levels, in a polymer synthesis lab.

Fast on-site diagnosis of influenza A virus by Palm PCR and portable capillary electrophoresis

A method combining Palm polymerase chain reaction (PCR) and portable capillary electrophoresis (CE) was developed for rapid on-site analysis of influenza A (H1N1) virus. The portable CE system was suitable for rapid diagnosis which was able to detect a sample in ∼4 min after sample loading, while the 'Palm PCR' system allowed for high-speed nucleic acid amplification in ∼16 min. The analysis time from DNA sample to analysis of amplified target DNA molecule was only ∼20 min, which was significantly less than slab gel electrophoresis with other commercially available PCR machine. When the 100-bp DNA ladder was separated, the relative standard deviation values (n=5) for the migration times and peak areas of the 100 and 200-bp DNA molecules were 0.26 and 8.9%. The detection limits were 6.3 and 7.2 pg/μL, respectively. The combined method was also able to identify two influenza A-associated genes (the HA and NP genes of the novel H1N1 influenza). CE separation was achieved with a sieving matrix of 1% poly(vinylpyrrolidone) (Mr=1,300,000) in 1× TBE buffer (pH 8.45). The combined Palm PCR-portable CE system should provide an improved, fast on-site molecular genetic diagnostic method.