3D-printed portable device for illicit drug identification based on smartphone-imaging and artificial neural networks.

In this manuscript, a 3D-printed analytical device has been successfully developed to classify illicit drugs using smartphone-based colorimetry. Representative compounds of different families, including cocaine, 3,4-methylenedioxy-methamphetamine (MDMA), amphetamine and cathinone derivatives, pyrrolidine cathinones, and 3,4-methylenedioxy cathinones, have been analyzed and classified after appropriate reaction with Marquis, gallic acid, sulfuric acid, Simon and Scott reagents. A picture of the colored products was acquired using a smartphone, and the corrected RGB values were used as input data in the chemometric treatment. ANN using two active layers of nodes (6 nodes in layer 1 and 2 nodes in layer 2) with a sigmoidal transfer function and a minimum strict threshold of 0.50 identified illicit drug samples with a sensitivity higher than 83.4 % and a specificity of 100 % with limits of detection in the microgram range. The 3D printed device can operate connected to a rechargeable lithium-ion cell portable battery, is inexpensive, and requires minimal training. The analytical device has been able to discriminate the analyzed psychoactive substances from cutting and mixing agents, being a useful tool for law enforcement agents to use as a screening method.

Partial least squares modelization of energy dispersive X-ray fluorescence.

As a proof of concept, a green methodology has been developed for the energy dispersive X-ray fluorescence (ED-XRF) determination of calcium, potassium, iron, magnesium, aluminum, chromium, strontium, phosphorus and nickel in the peel of untreated kaki fruit (Diospyros kaki. L) samples. ED-XRF spectra of fifty-six kakis purchased in the local area of LLombay (Valencia) were obtained directly from samples without any previous treatment and without sample damage just after cleaning the fruit with distilled water. Inductively Couple Plasma Optical Emission Spectrometry (ICP-OES) was used as a reference method to determine the mineral elements after microwave assisted acid digestion. XRF spectra and concentration values obtained by ICP-OES were processed using partial least squares (PLS) data treatment to build the corresponding chemometric models for prediction of mineral profile of samples. PLS-ED-XRF permits a direct and accurate determination of Ca and K in kaki peel. For Al, Fe, Mg, Ni and Sr screening semiquantitative results were obtained. Concentrations obtained directly by the internal calibration of instrument, using GeoChem Trace model, were also compared with data predicted by chemometric models being found that PLS models must replace the calibration of the instrument for thus kind of analysis.

Direct determination by portable ED-XRF of mineral profile in cocoa powder samples.

The present study has exploited the rapidity of the analysis and the multi-elemental capability of the energy dispersive X- ray fluorescence (ED-XRF) technique for the mineral profile determination in cocoa powder. A fast, cheap and environmental sustainable method without reagent consumption or toxic waste generation has been proposed. The samples can be prepared in the form of pellets of 13 mm in diameter and 2-3 mm thickness. The different internal calibrations used by ED-XRF equipment did not provide accurate results when comparing the mineral profile with the concentration obtained by Inductively Couple Plasma Optical Emission Spectroscopy (ICP-OES) after microwave assisted digestion of samples. For direct ED-XRF analysis of the cocoa samples, an external calibration using as standards the cocoa samples diluted with sugar was prepared. The analytical parameters of Relative Standard Deviation and Limit of Detection for the determined elements are adequate to the concentration levels found in the samples.

Chronic urticaria after implantation of a mitral annuloplasty ring in a nickel-allergic patient

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Ecofriendly in-line process monitoring: a case study. Anthracene photodegradation in the presence of refuse-derived soluble bio-organics.

Photodegradation of anthracene has been studied in aqueous solutions containing soluble bio-organic substances isolated from urban refuse. To perform a preliminary rapid feasibility study of this process while reducing the amount of analytical effort and reagents, an experimental set-up was developed comprising a Teflon coil surrounding a UV-lamp and coupled with an in-line spectrofluorimeter. In this fashion only few millilitres of solution are needed to study the degradation process. Furthermore, the in-line spectroscopic approach enables monitoring of the process without consumption of reagents. Additional studies by liquid chromatography and use of toxicity tests clearly indicated that the apparent inhibition effect of bio-organic compounds on anthracene degradation is not relevant. The results imply that urban refuse may be used as an auxiliary in the recovery of polycyclic aromatic hydrocarbons from contaminated soil by washing, without deleterious effects on the photodegradation of anthracene and other aromatic pollutants.

A multicommuted flow system with solenoid micro-pumps for paraquat determination in natural waters.

A flow system designed with solenoid micro-pumps is proposed for the determination of paraquat in natural waters. The procedure involves the reaction of paraquat with dehydroascorbic acid followed by spectrophotometric measurements. The proposed procedure minimizes the main drawbacks related to the standard chromatographic procedure and to flow analysis and manual methods with spectrophotometric detection based on the reaction with sodium dithionite, i.e. high solvent consumption and waste generation and low sampling rate for chromatography and high instability of the reagent in the spectrophotometric procedures. A home-made 10-cm optical-path flow cell was employed for improving sensitivity and detection limit. Linear response was observed for paraquat concentrations in the range 0.10-5.0 mg L(-1). The detection limit (99.7% confidence level), sampling rate and coefficient of variation (n=10) were estimated as 22 microg L(-1), 63 measurements per hour and 1.0%, respectively. Results of determination of paraquat in natural water samples were in agreement with those achieved by the chromatographic reference procedure at the 95% confidence level.

Extraction of polycyclic aromatic hydrocarbons from cookies: a comparative study of ultrasound and microwave-assisted procedures.

The chromatographic determination of 15 polycyclic aromatic hydrocarbons (PAHs) in cookies has been improved in order to obtain a fast method with a low limit of detection through the combination of microwave-assisted extraction (MAE), oil saponification and solid-phase extraction clean-up before the injection of purified extracts in a C18 201TP52 (5 microm, 250 x 2.1 mm) column. Using acetonitrile-water as mobile phase, with a 50% to 95% w/w acetonitrile gradient for a fixed flow of 0.250 ml min(-1), 15 PAHs were separated in 45 min. The column temperature was maintained at 15 degrees C; and fluorimetric detection was made at a fixed excitation wavelength of 264 nm and emission measurements at the best wavelength for each analyte, from 352 nm for 11H-benzo[b]fluorene to 500 nm for indeno[1,2,3-c,d]pyrene. Recoveries for all 15 PAHs varied between 96 +/- 4 and 105% +/- 4%; and the limits of detection ranged from 0.015 ng g(-1) for chrysene to 0.7 ng g(-1) for phenantrene. Results were compared with those obtained by conventional Soxhlet extraction during 8-h refluxing with toluene, demonstrating that the methodology proposed is appropriate to quantify PAHs in cookies. Furthermore, the microwave-assisted method was faster and used less solvent than the conventional and ultrasound-assisted methods. The extraction time was reduced to 9 min compared with the 8 h required for Soxhlet extraction and 60 min required for ultrasound-assisted treatment, and the solvent consumption has been reduced to 25 ml compared with the 155 and 90 ml required using Soxhlet and ultrasound, respectively.

Chromium speciation using activated alumina microcolumns and sequential injection analysis-flame atomic absorption spectrometry.

A new procedure has been developed for chromium speciation in water by sequential injection analysis and flame atomic absorption spectrometry. The method involves the online retention of Cr(VI) anionic species and Cr(III) cationic species on alumina microcolumns, prepared by packing activated alumina in polytetrafluoroethylene tubes, followed by selective elution of Cr(VI) with 2 mol l(-1) NH(4)OH and of Cr(III) with 0.2 mol l(-1) HNO(3). Studies were carried out on the effect of retention and elution conditions for both Cr species. The limit of detection values, established as the concentration corresponding to three times the standard deviation of blank measurements divided by the slope of the calibration line, achieved were 42 mug l(-1) for Cr(VI) and 81 mug l(-1) for Cr(III). The relative standard deviation of three independent determination of natural spiked samples were lower than 10% for concentration levels between 0.5 and 2 mg l(-1) of Cr. The developed procedure was applied to the analysis of two effluent sewage waters, and results obtained compared well with those obtained by a batch procedure. Recovery studies on natural spiked samples provided results between 93 and 103% for Cr(VI) and from 100 to 106% for Cr(III) for samples spiked with single species. For samples spiked with both Cr(VI) and Cr(III), the average recoveries varied from 86 to 101% for Cr(VI) and from 91 to 117% for Cr(III).

Chromium speciation in liquid matrices: a survey of the literature.

A thorough review of the literature published (1983 - March 1999) on chromium speciation in liquid samples is presented, and analytical techniques used in the 404 articles are summarized. The discussion focuses on atomic spectrometric techniques, which are mainly employed for chromium speciation in liquid matrices (134 articles). Details on the type of pretreatment, species, samples, techniques and analytical features of the methodologies proposed are given.

Atomic fluorescence spectrometric determination of trace amounts of arsenic and antimony in drinking water by continuous hydride generation.

A highly sensitive and simple method has been developed for the determination of As(III), total As, Sb(III) and total Sb in drinking water samples by continuous hydride generation and atomic fluorescence spectrometry (HGAFS). For As determination, water samples aspirated in a carrier of 2 mol l(-1) HCl were merged with a reducing NaBH(4) 3%(m/v) solution, with sample and NaBH(4) flow rates of 12.5 and 1.5 ml min(-1) respectively. The hydride generated in a 170 cm reaction coil was transported to the detector with an Ar flow of 400 ml min(-1), and a limit of detection between 5 and 20 ng l(-1) was obtained. For Sb determination, 2.5 mol l(-1) HCl and 2%(m/v) NaBH(4) were employed, with respective flow rates of 9.7 and 2 ml min(-1). The hydride generated in a 50 cm reaction coil was transported to the detector with an Ar flow rate of 300 ml min(-1), and a limit of detection between 6 and 14 ng l(-1) was obtained. Determination of the total concentration of these elements was obtained after a previous reduction with KI. Recovery studies of different added concentrations of these species in natural water samples were between 93 and 104% for As(III), 96-103% for As(V), 93-101% for Sb(III) and 90-119% for Sb(V).

Spectrophotometric determination of phenol and resorcinol by reaction with p-aminophenol.

Based on the reaction with p-aminophenol, a series of procedures have been developed for the spectrophotometric determination of phenol and resorcinol. Three basic approaches have been studied: (i) a batch procedure, using the dissolved oxygen as oxidant, (ii) a stopped-flow procedure by use of KIO(4) as oxidant and (iii) a flow injection (FI) procedure developed in the presence of KIO(4). Phenol can be accurately determined at 626 nm, in the stopped-flow mode, after a reaction time of 45 min in 0.005M NaOH, 0.004M KIO(4) and 500 mug/ml of PAP. The development of a manifold, which incorporates a sample parking, is a convenient approach which makes it possible to measure, in the stopped-flow mode, four solutions in one hour. The limit of detection of this method corresponds to 64 ng/ml of phenol Resorcinol can be determined by FI at 540 nm in 0.006M NaOH, 0.0002M KIO(4) and 50 mug/ml PAP with a limit of detection of 6.6 ng/ml and a sample throughput of 300 injections per hour. A combination between the FI procedure for the determination of resorcinol and the stopped-flow procedure for phenol determination provides accurate results in the analysis of spiked samples containing both phenol and resorcinol.

On-line microwave-assisted digestion of solid samples for their flame atomic spectrometric analysis.

A new procedure has been developed for the on-line digestion of solids in a microwave oven. The direct injection in a water carrier flow of dispersions of solid samples in concentrated nitric acid, the merging of these slurries with 30% (v/v) H(2)O(2) and the microwave-assisted digestion in a Teflon coil of 100 cm permit a fast and quantitative extraction of Cu and Mn from different solid matrices, such as vegetables, powdered dietary products and sewage sludges. The development of an appropriate interphase, in which digested samples are cooled and degassified, previous to their introduction into the nebulizer of a flame atomic absorption spectrometer, makes possible the full automatization of the digestion and measurement steps of the elemental analysis of solids and it provides a sample frequency of 180 injections per hour. The developed procedure has also been applied for Pb and Zn determination in certified sewage sludge samples, with accurate results obtained for Pb but low results found for Zn.