Blank Intensity Research Articles

Magnetic dispersive solid phase extraction for simultaneous enrichment of cadmium and lead in environmental water samples

A new magnetic dispersive solid phase extraction (MDSPE) method and graphite furnace atomic absorption spectrometry (GFAAS) have been combined for the simultaneous enrichment of Cd and Pb from environmental water samples including seawater, and subsequent sequential determination of both analytes. For the preconcentration, a shell structured Fe3O4@graphene oxide nanospheres was synthetized and characterized. This nanosorbent presents a large contact area and has a high surface density of polar groups. With the optimized method, the experimental detection and determination limits, calculated as the concentration of analyte giving signals equivalent to three and ten times, respectively, the standard deviation of the blank plus the net blank intensity, were 0.005 µg L−1 (detection limit) and 0.017 µg L−1 (determination limit) for Cd; and 0.008 µg L−1 (detection limit) and 0.026 µg L−1 (determination limit) for Pb. The method offers good precisions (RSD < 3.5%) and a preconcentration factor of 200. The accuracy of the proposed method was verified using certified reference materials (SLRS-5, SPS-SW2) and by determining the analytes content in spiked seawater and tap water samples collected from Málaga (Spain). The determined values by external calibration were in good agreement with the certified values and the recoveries for the spiked samples were around 100% in all cases.

Innovative Methods for the Integration of Immunosensors Based on Magnetic Nanoparticles in Lab-on-Chip

Commonly immunoassay using magnetic nanoparticles (MNP) are performed under the control of permanent magnet close to the micro-tube of reaction1. Using a magnet gives a powerful method for driving MNP but remains unreliable or insufficient, for a fully integrated immunoassay on lab-on-chip. The aim of this study is to develop a novel lab-on-chip (Figure 1.B) for high efficient immunoassays to detect pathogenic bacteria with microcoils employed for trapping MNP during the biofunctionalization steps. Studies on bacteria are mainly based on E. Coly2,3 which is a non-pathogenic bacteria and can be find everywhere. In our case we use ovalbumin which is defined as a biodefense model protein. The objectives are essentially to optimize their efficiency for biological recognition, by assuring a better bioactivity (antibodies-ovalbumin), and detect small concentrations of the targeted protein (∼10 pg/mL).The fluidic microsystem is made of PDMS, which is micro-molded in SU8, it had channels with 50 μm height and 500 μm width. Microfluidic conditions permit a faster biofonctionnalisation step than in test tube and allow capture and detection of biological elements integrated in lab-on-chip.Microcoils are electrodeposited on silicon using cupper. They are microfabricated with cupper wire of 10 μm height, 10 μm width, 10 μm space between wire and 45 spires. Microcoils are encapsulated in microfluidic chip by covering them with a spin-coated thin layers of PDMS. Microcoils give a local and efficient trapping of MNP and a fully integrated device.Biological activity is studied respecting ELISA protocol with ovalbumin as protein of interest. To graft the primary antibody and protect the free area of MNP we used carboxylic as terminal group for grafting antibodies and BSA (Bovine Serum Albumin) for passivation (Figure 1.A). We characterize this method by measuring the intensity of the antibody of detection using FITC (Fluorescein isothiocynathe). Intensity is detected by fluorescent microscope connected to the microfluidic plateform and images are processed using a home-made script.First we studied the response of immunoassays complex function of MNP size (200 nm, 300 nm and 500 nm), we confirmed that with a lower diameter we increase the intensity detected, following specific surface formula (1), (2), (3). [Display omitted] Regarding the magnetic force needed (depending of several parameters including magnetic field and parameters of the particle) and the intensity detected we selected 300 nm size of NPM.We studied the response of immunoassays complex function of ovalbumin concentration. We realized different immunoassays by controlling MNP (Figure 1.C&D) in test tube and in microfluidic device using a magnet. The comparison between these two experiments allow us to show an improved limit of detection (L.O.D. = I0– 3 × σD ; σD: standard deviation, I0: Blank Intensity) using microfluidic conditions and controlling MNP trapping with a magnet.In conclusion, we developed an original and innovative fully-integrated immunoassay on lab-on-chip in order to detect bacteria. We use ovalbumin as a Biodefense model protein, magnetic nanoparticles and ELISA protocol to perform immunoassay. We demonstrate the advantage of microfluidic chip with a optimize limit of detection (less four time). Adding microcoils, we hope obtain a fully integrated lab-on-chip which should allow us to attain optimal specificity and sensitivity for the detection of very low bacteria concentration for biodefense applications. We developed an original and innovative fully-integrated immunoassays on LOC which will open the route to a very high sensitive and specific immunoassay platform.

Forensic analysis of arsenic poisoning in Japan by synchrotron radiation X‐ray fluorescence

Synchrotron radiation X‐ray fluorescence (SR‐XRF) analysis reports of a poisoning case by arsenic, 25 July 1998, Japan, for forensic investigation purposes are reviewed. In these forensic analyses, SPring‐8 and KEK‐PF beamlines were used for minor element (Sn, Sb, Mo, Bi, Ba) analysis in the arsenic pesticide specimens, sampled at the crime scene as well as the neighborhood of the suspect. For this case, two kinds of documents were submitted to court: one was a qualitative analysis and said to be a ‘pattern recognition’ by Prof. Nakai, and the other was, by Profs Taniguchi and Hayakawa, a quantitative analysis after background subtraction, normalized by the sample thickness, where calibration curves were made with reference to the inductively coupled plasma atomic emission spectrometry (ICP‐AES) analysis for reference samples. The final decision of the court was a death sentence based on the qualitative ‘pattern recognition’. The present review concludes that the quantitative analysis by Profs Taniguchi and Hayakawa was scientifically more important than the ‘pattern recognition’ qualitative analysis, because the Taniguchi‐Hayakawa report used novel but reliable data processing methods. The Sn, Sb, and Mo Kα intensities were normalized with respect to the As (major element) Kα (10.5 keV) intensity as a thick target, whereas the Bi and Ba Kα intensities were normalized by the Rayleigh scattering (for 116 keV incident beam) as a thin target. The Taniguchi‐Hayakawa report was the first quantitative report in high‐energy SR‐XRF analysis. The most important conclusion in the present review is that the ICP‐AES was more reliable over these SR‐XRF analyses, because even the beamline selection was not possible without the knowledge of the impurity elements obtained by the ICP‐AES. Five elements (Se, Sn, Sb, Pb, and Bi) were used in ICP‐AES for identification compared with only three elements (Sn, Sb, and Bi) in SR‐XRF. High blank intensity resulted from using Pb for X‐ray collimator in the beamline. Overlapping of the analytical lines of minor Se and major As prevented the use of Se for identification. Recent analysis of Fe, Zn, Mo, and Ba in Nakai's raw spectra measured in 1998 reveals the arsenic stored in the kitchen of the condemned criminal in the death row was significantly different from that of the paper cup used for poisoning. Copyright © 2013 John Wiley &amp; Sons, Ltd.

X‐ray fluorescence analysis of Co, Ni, Pd, Ag, and Au in the scrapped printed‐circuit‐board ash

A method for the quantitative analysis of Co, Ni, Pd, Ag, and Au in the scrapped printed‐circuit‐board ash by X‐ray fluorescence (XRF) spectrometry using loose powder was developed. The printed‐circuit‐board samples were converted to ash pyrolytically in porcelain crucibles by sequential heating using a gas burner and electric furnace, and then were ground with a ball mill. The calibrating standards were prepared by adding the appropriate amounts of NiO powder and aqueous standard solutions containing Co, Pd, Ag, and Au to the base mixtures of Al2O3 (5.0 mass%), SiO2 (49 mass%), CaCO3 (11 mass%), Fe2O3 (3.3 mass%), and CuO (30 mass%) as a matrix. Then, 10 g of the resulting mixtures were dried and homogenized for 90 min with a V‐type mixing machine. Specimens for XRF analysis were prepared from the so‐called loose‐powder method in which powder samples were compacted into a hole (12.0‐mm diameter and 5.0‐mm height) in an acrylic plate and covered with a 6‐µm thickness of polypropylene film. Matrix effects were corrected using the intensity value of Compton scattering for PdKα, AgKα, and AuLβ2, and that of background scattering at 35.8° (2θ) for CoKα and NiKα. The detection limits corresponding to three times the standard deviation of the blank intensity were 2.5–45 µg g−1. The proposed method was validated against the pressed‐powder‐pellet method by comparing the calibration curves. Moreover, the concentrations of Co, Ni, Pd, and Ag determined using the proposed XRF method were approximately the same as those resulting from an atomic‐absorption‐spectrometric analysis. Copyright © 2013 John Wiley &amp; Sons, Ltd.

X-ray fluorescence analysis of trace metals in environmental water using preconcentration with an iminodiacetate extraction disk

A simple and convenient x-ray fluorescence analysis procedure for trace amounts of Mn, Fe, Co, Ni, Cu, Zn, Cd, Hg and Pb in water was developed using preconcentration with an iminodiacetate extraction disk (IED). The IED was coated on both faces with commercially available laminate film to prevent x-ray damage to the IED by strong x-irradiation (4 kW; 50 kV, 80 mA) of the wavelength-dispersive x-ray fluorescence spectrometer. Lamination of the IED prolongs its life from 7 to about 200 min at 4 kW irradiation while negligibly decreasing the x-ray fluorescence. Lowering the power of primary x-rays to less than 1.5 kW compensated for the Hg evaporation. Linear calibration curves were obtained over the range 500 µg–5 mg for Mn, Fe, Co, Ni, Cu, Zn, Cd, Hg and Pb. Detection limits corresponding to three times the standard deviation of the blank intensity were 0.1–0.4 µg for Mn, Co and Ni, 0.5–0.8 µg for Fe, Cu, Zn and Pb and 7 µg for Cd. A spike test for 10 µg of eight analytes, excluding Mn, showed good recoveries (90–100%) for city water and rainwater. Analytical results for municipal tap water and rainwater agreed well with values obtained using atomic absorption spectrometry. Copyright © 2006 John Wiley & Sons, Ltd.

Increased digitalis-like immunoreactive substances in neonatal plasma measured using fluorescence polarization immunoassay

To better define the reported increased digitalis-like immunoreactive substances (DLIS) in neonatal plasma, we studied the relation among plasma DLIS level, blank intensity (BLK-I) value at FPIA measurement and plasma total bilirubin level. The DLIS levels were measured in 10 neonates with or without jaundice and 10 infants in good health, using fluorescence polarization immunoassay (FPIA) and microparticle enzyme immunoassay (MEIA). BLK-I value and plasma total bilirubin level were also measured simultaneously. In neonates with jaundice, DLIS using FPIA, BLK-I and total bilirubin level were 0.58 +/-0.13 ng/mL, 2598 +/- 408, and 17.98 +/- 1.13 mg/dL, respectively, before phototherapy, and 0.33 +/-0.06 ng/mL, 1886 +/- 237, and 15.16 +/- 2.07 mg/dL after phototherapy. Corresponding values in neonates without jaundice were (DLIS: 0.34 +/-0.04 ng/mL; BLK-I: 1,764 +/- 278; total bilirubin: 10.37 +/- 4.54 mg/dL); in healthy infants (0.12 +/-0.06 ng/mL, 400.7 +/- 4.6 and 0.42 +/- 0.13 mg/dL, respectively) and in healthy volunteers (0.10 +/-0.07 ng/mL, 403.1 +/- 8.4, and 0.58 +/- 0.30 mg/dL, respectively). Using MEIA, DLIS was not detected in 10 neonates, 10 infants and 20 healthy volunteers. A fluorescent compound related to bilirubin increased the BLK-I value in the measurement of neonatal plasma using FPIA. The fluorescence was not the result of endogenous digitalis-like factors.

Performance optimization of a commercially available iminodiacetate resin for the determination of Mn, Ni, Cu, Cd and Pb by on-line preconcentration inductively coupled plasma-mass spectrometry

The on-line preconcentration performance characteristics of a commercially available iminodiacetate resin (Toyopearl AF-Chelate 650M) were investigated. The method was optimized for several parameters, including buffer pH, rinsing of matrix salts from the resin, elution acid type and strength, and the nebulizer gas flow rate. An ammonium chloride buffer with a pH of 8.80 was mixed with the sample on-line prior to loading. This pH was found to be optimal for Mn, Cu, Cd and Pb, whereas a pH of ≥9.2 was optimal for Ni analysis. Column rinse experiments showed that both buffer and water reduce Na concentrations to <100 μM in the rinse solution within 3 min. It was also determined that using 1 M HNO 3 acid for column elution yielded higher intensities for Mn, Ni, Cu and Pb, while 1 M HCl yielded higher count rates for Cd. The change from the optimization solution, with a 0.2% HNO 3 acid concentration, to the 10% elution acid required a reduction in the nebulizer gas flow rate of 0.05 l min −1 in order to obtain reduced blank intensity ratios. Calibrations performed using standard solutions (1 ml) with concentrations ranging from 0 to 10 pg ml −1 (ppt) resulted in regression coefficients of 0.990–0.998. Method detection limits of 1.1, 0.08, 0.47, 0.06 and 0.16 pg ml −1 for Mn, Ni, Cu, Cd and Pb, respectively, were obtained. Accuracy was demonstrated by results from runs of the certified standard reference materials (SRMs), CASS-4, a newly available coastal seawater reference standard and NASS-4, an open ocean seawater reference material.

Chemiluminescence derivatization of methylglyoxal using 2-aminonicotinic acid.

To develop a sensitive and selective chemiluminometric method for the determination of methylglyoxal, we used 2-aminonicotinic acid as the chemiluminescence derivatization reagent. 2-Aminonicotinic acid reacts with methylglyoxal in an acidic solution at 37 degrees C for 4 h and gave a chemiluminescence in N,N'-dimethylformamide containing sodium tert-butoxide. The detection limit (blank intensity plus three-times its standard deviation of methylglyoxal) for methylglyoxal is 233 fmol in the reaction mixture.