A rapid lateral flow test for the determination of total type B fumonisins in maize

A one-step lateral flow test was developed for the quantitative determination of total type B fumonisins in maize with a test range up to 4,000 μg/kg and a limit of detection of 199 μg/kg. The test presented gives a result within 4 min, including 1 min strip drying, and does not require any sample cleanup steps after a previous 3-min sample extraction. Quantitative readout with a compact photometric strip reader will also indicate the best suited measurement range when needed. The test is based on a competitive immunoassay format where a ready-to-use antibody–colloidal gold particle complex is mixed with 50 μL sample extract in a microwell and used as a signal reagent. The test strip is inserted into the well and the mixed content migrates onto the strip, which contains a test zone and a control zone. Mycotoxin–protein conjugate coated on the test zone captures free signal reagent, and colored particles concentrate, forming a visible line. The intensity of the test line is dependent on the total fumonisin concentration in the sample. Naturally contaminated quality-control maize material was used for matrix-matched calibration of photometric readout. The test presented is both quantitative and rapid, with no cross-reactivity to other mycotoxins. The applicability of the lateral flow test was shown by the screening of 23 naturally contaminated maize samples. Relative standard deviations ranged from 1.7 to 32.9%.     

Determination of surface tension and contact angle from the shapes of axisymmetric fluid interfaces without use of apex coordinates

Drop shape techniques, such as axisymmetric drop shape analysis, are widely used to measure surface properties, as they are accurate and reliable. Nevertheless, they are not applicable in experimental studies dealing with fluid configurations that do not present an apex. A new methodology is presented for measuring interfacial properties of liquids, such as surface tension and contact angles, by analyzing the shape of an axisymmetric liquid-fluid interface without use of apex coordinates. The theoretical shape of the interface is generated numerically as a function of surface tension and some geometrical parameters at the starting point of the interface, e.g., contact angle and radius of the interface. Then, the numerical shape is fitted to the experimental profile, taking the interfacial properties as adjustable parameters. The best fit identifies the true values of surface tension and contact angle. Comparison between the experimental and the theoretical profiles is performed using the theoretical image fitting analysis (TIFA) strategy. The new method, TIFA-axisymmetric interfaces (TIFA-AI), is applicable to any axisymmetric experimental configuration (with or without apex). The versatility and accuracy of TIFA-AI is shown by considering various configurations: liquid bridges, sessile and pendant drops, and liquid lenses.     

Measurements of ambient ozone using indigo blue-coated filters

Ozone monitoring techniques utilize expensive instruments that are often large and heavy. These instruments are not easy to handle in the field, and their size also limits some sampling schemes, principally for indoor ozone determination. We have developed a lightweight, inexpensive, and sensitive method that offers flexibility to undertake measurements of ambient ozone in many environments, both indoor and outdoor. The method is based on the reaction of ozone with indigo blue dye. The indigo molecule contains 1 carbon double bond (C = C) that reacts with ozone and results in nearly colorless reaction products. During sample collection, 2 cellulose filters coated with 40 micro of 1.0 x 10(-3) M indigo blue were used. The determinations were done spectrophotometrically at 250 and 600 nm. The analytical parameters studied were sampling time and flow rate. Analytical curves were constructed with concentrations ranging from 37 to 123 parts per billion by volume (ppbv) of standard ozone, at 0.4 L/min and 15 min sampling time. The detection limits achieved were 6 and 9 ppbv, respectively, at 250 and 600 nm. Considering interferences, measurements made at 250 nm gave more reliable and specific values for ozone.     

Influence of the Operative Conditions on the Characteristics of Poly(D,L-lactide-co-glycolide) Synthesized in Supercritical Carbon Dioxide

Summary: The co-polymerizations of D,L -lactide and glycolide in supercritical carbon dioxide (scCO₂) using zinc (II) ethylhexanoate (ZnOct₂) as catalyst and methanol as initiator have been investigated. The influence of stirring rate (N), temperature (T), and mass carbon dioxide (m_CO2) on molecular weight distribution (MWD); co-polymer composition; and conversion has been studied by means an experimental factorial design. The stirring rate has the greatest influence on conversion. Due to the heterogeneous nature of the process the mass transfer enhancement, that the grater turbulence produces, favors greatly the incorporation of monomers into the polymer phase. An important decrease of molecular weight is observed independently of reaction conditions for high conversion values because some thermal degradation or rearrangement reactions are taking place. The influence of the initiator, methanol, on the molecular weight has been also studied. Methanol acts as an effective chain transfer agent initiating more growing chains than expected, what also contributes to get low molecular weights.     

Efficient syntheses of four stable-isotope labeled (1R)-menthyl (1S,2S)-(+)-2-phenylcyclopropanecarboxylates

Many carbenoid cyclopropanation reactions promoted by chiral catalysts give product mixtures reflecting impressive diastereo- and enantioselectivities. Few provide a single chiral product efficiently. This limitation has been overcome in cyclopropanations of styrene and isotopically labeled styrenes with alpha-diazoacetates. Convenient syntheses on a 20 g scale of each of four chiral isotopically labeled (1R)-menthyl (1S,2S)-2-phenylcyclopropanecarboxylates (the 1-d-3-(13)C, 1,(3S)-d2, 1,2,(3S)-d3, and 1,3,3-d3 isotopomers) of better than 99% ee have been realized.     

Near-infrared spectroscopic analysis of aging degradation in antique washi paper using a deuterium exchange method

The diffusion process of deuterated water (D₂O) in washi (Japanese traditional paper) was investigated by means of a deuterium exchange method and Fourier-transform near-infrared (FT-NIR) transmission spectroscopy. The samples were the modern (AD 2003) hand-made washi and those from an archival collection of cultural artifacts (AD 1791 and 1615). Four absorption bands were identified in the NIR spectral range from 7200 to 6000 cm⁻¹ which are due to OH groups in the amorphous, semi-crystalline and two types of crystalline regions of cellulose. The accessibility of D₂O increased with decreasing state of order of cellulose, and the saturation accessibility increased with the age of the samples. It was suggested that during aging hemicellulose, which forms a composite with cellulose in paper, was progressively hydrolyzed, resulting in the expansion of inter-molecular distance between cellulose chains. The oldest sample showed a low diffusion rate compared with the others. SEM observation of the textile structures indicated that the oldest sample had two layers due to beating. It was estimated that the tight surface layer blocked the diffusant in the initial stage of the diffusion process.     

BiOClO4-mediated deprotection of silyl ethers

TES- and TBS-protected alcohols undergo deprotection in good to excellent yield upon heating with 1 equiv of BiOClO₄-xH₂O in CH₂Cl₂. TBDPS- and TIPS-protected 2° alcohols are more resistant to deprotection. The use of this method in selective desilylation is, however, limited to the deprotection of alkyl silyl ethers in the presence of TBDPS-protected phenols.     

Synthesis and structural study of cyclopentane,indene and fluorene spiro-derivatives

The synthesis of three pharmacologically interesting series of cyclopentane, indene-2 and fluorine-9-spiro-5′-oxazolidine-2′, 4′-dione is described. Based on the data from ¹H and ¹³C nmr spectra, the main conformational features of the above mentioned compounds is established.     

PHOTODYNAMIC ACTIVITIES and SKIN PHOTOSENSITIVITY OF THE bis(DIMETHYLTHEXYLSILOXY)SILICON 2,3-NAPHTHALOCYANINE IN MICE

The photodynamic therapy (PDT) activity of the bis(dimethylthexylsiloxy)silicon 2,3-na-phthalocyanine (SiNc 8 ) was evaluated against the EMT-6 tumor implanted intradermally in BALB/c mice. The SiNc 8 was formulated in aqueous emulsions based on Cremophor EL or Solutol HS 15. The formulation was shown to affect plasma clearance and overall pharmacokinetics. Compared to Cremophor, Solutol promoted rapid plasma clearance and high liver retention of the dye, combined with a slight increase of dye tumor concentrations. The PDT action spectrum for tumor response of SiNc 8 in Cremophor (190 mW cm², 200 J cm², 24 h postinjection [p.i.] of 1 (jimol kg¹) showed a maximum at 780 nm, which corresponds to the absorption maximum of the monomelic dye as well as the in vivo maximum change in the “diffuse optical density” produced by the dye. The extent of tumor necrosis increased with augmented dye and light doses. Regardless of the formulation, at 1 h p.i. of 0.1 μmol kg^?! SiNc 8 , PDT efficiency (190 mW cm'², 400 J cm²) was high but accompanied by severe damage to normal tissues, at 24 h PDT resulted in complete tumor regression in 80% of the animals without adverse effects to adjacent tissues, while at 72 h p.i. PDT induced no tumor response with Cremophor and only a partial response with Solutol. At the latter time point, plasma dye clearance was nearly complete while tumor tissue levels remained high, suggesting that tumor response correlates with plasma rather than tumor dye levels. Skin sensitivity of SKhl mice to solar-simulated radiation was lower with SiNc 8 as compared to Photofrin®. Our data suggest the potential of SiNc 8 as a far-red absorbing photosensitizer in clinical PDT.     

Flow injection spectrophotometric determination of isoproterenol using an avocado (Persea americana) crude extract immobilized on controlled-pore silica reactor

An enzymatic reactor was constructed by the immobilization of polyphenol oxidase (PPO) from avocado (Persea americana) crude extract in an inorganic support of controlled pore silica (CPS), after a previous step of silanization. This inorganic support has been used as an excellent carrier to immobilize this enzyme and the enzymatic reactor was used in a flow injection system for the determination of isoproterenol in pharmaceutical products. The procedure is based on the oxidation reaction of this drug with immobilized PPO and the product obtained was monitored at 492 nm. This system presented an analytical curve from 1.23x10(-4) to 7.38x10(-4) mol l(-1) isoproterenol with a detection limit of 6.25x10(-5) mol l(-1). Recoveries of isoproterenol between 98.5 and 103.1%, a relative standard deviation (R.S.D.) less than 1% (n=10) and 36 determinations per h were obtained.