Sequential injection titration with spectrophotometric detection for the assay of acidity in fruit juices.

A simple sequential injection analysis (SIA) with spectrophotometric detection for an assay of acidity in fruit juice was investigated. An alkaline reagent (sodium hydroxide), a sample and an indicator (phenolphthalein) were first aspirated and stacked as adjacent zones in a holding coil. With flow reversal through a reaction coil to the detector, zone penetration occurred, leading to a neutralization reaction that caused a decrease in the color intensity of the indicator being monitored for absorbance at 552 nm. The effects of various parameters were studied. Linear calibration graphs for acidities of 0.2 - 1.0 and 0.5 - 2.5% w/v citric acid as a standard, with a relative standard deviation of 1% (acidity of 0.3 - 0.6% w/v as citric acid, n=11) and a sample throughput of 30 samples h(-1), were achieved. The developed method was validated by a standard titrimetric method for assaying the acidity of fruit juice samples.     

Examination of the distribution of nicosulfuron in sunflower plants by matrix‐assisted laser desorption/ionisation mass spectrometry imaging

Matrix‐assisted laser desorption/ionisation mass spectrometry imaging (MALDI‐MSI) has been used to image the distribution of the pesticide nicosulfuron (2‐[[(4,6‐dimethoxypyrimidin‐2‐yl)aminocarbonyl]aminosulfonyl]‐N,N‐dimethyl‐3‐pyridinecarboxamide) in plant tissue using direct tissue imaging following root and foliar uptake. Sunflower plants inoculated with nicosulfuron were horizontally sectioned at varying distances along the stem in order to asses the extent of translocation; uptake via the leaves following foliar application to the leaves and uptake via the roots from a hydroponics system were compared. An improved sample preparation methodology, encasing samples in ice, allowed sections from along the whole of the plant stem from the root bundle to the growing tip to be taken. Images of fragment ions and alkali metal adducts have been generated that show the distribution of the parent compound and a phase 1 metabolite in the plant. Positive and negative controls have been included in the images to confirm ion origin and prevent false‐positive results which could originate from endogenous compounds present within the plant tissue. Copyright © 2009 John Wiley & Sons, Ltd.     

The Prevalence of Childhood Dysphonia: A Cross-Sectional Study

There is only very limited information on the prevalence of voice disorders, particularly for the pediatric population. This study examined the prevalence of dysphonia in a large cohort of children (n = 7389) at 8 years of age. Data were collected within a large prospective epidemiological study and included a formal assessment by one of five research speech and language therapists as well as a parental report of their child's voice. Common risk factors that were also analyzed included sex, sibling numbers, asthma, regular conductive hearing loss, and frequent upper respiratory infection. The research clinicians identified a dysphonia prevalence of 6% compared with a parental report of 11%. Both measures suggested a significant risk of dysphonia for children with older siblings. Other measures were not in agreement between clinician and parental reports. The clinician judgments also suggested significant risk factors for sex (male) but not for any common respiratory or otolaryngological conditions that were analyzed. Parental report suggested significant risk factors with respect to asthma and tonsillectomy. These results are discussed in detail.     

N<Subscript>2</Subscript>O catalytic decomposition — effect of pelleting pressure on activity of Co-Mn-Al mixed oxide catalysts

The effect of pelleting pressure (0–10 MPa) during the preparation of Co-Mn-Al mixed oxide catalyst on its texture and activity for N₂O catalytic decomposition was examined for small grain sizes used in laboratory experiments, and for model industry catalyst particles. Adsorption/desorption measurements of nitrogen, mercury porosimetry and helium pycnometry were used for detail characterization of porous structure. A volume of micropores of about 20 mm³ g⁻¹ was evaluated using modified BET equation. This value did practically not change with the increasing pelletization pressure except that of the sample formed at the pressure of 10 MPa. Although an increase of pelleting pressure caused an increase in bulk density and a decrease in pore size and pore volume of the prepared catalyst (resulting in lower values of N₂O effective diffusion coefficient), no direct correlation between pelleting pressure used and catalyst activity has been found. In contrary, estimation of the internal diffusion limitation according to the Weisz-Prater criterion indicated that even laboratory experimental data obtained for catalyst grains with particle size lower than 0.315 mm pelletized at higher pressures could be influenced by internal diffusion. Estimation of the internal mass transfer limitation in industrial catalyst particles described by the effectiveness factor showed that effectiveness factor of about 0.07 and 0.2 can be obtained for spheres with the radius of 1.5 mm and 0.5 mm, respectively, if pelleting pressure of about 6 MPa was used for the catalyst preparation. Presented at the 35th International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 26–30 May 2008.     

Flow-injection and sequential-injection determinations of paracetamol in pharmaceutical preparations using nitrosation reaction.

A simple FI and two different SI systems have been investigated for the determination of paracetamol by employing a simple reagent for a nitrosation reaction. It is based on the on-line nitrosation of paracetamol with sodium nitrite in an acidic medium. The formed nitroso derivative species reacts further with sodium hydroxide to convert it to a more stable compound. The yellow product is continuously monitored at 430 nm. The FI system is very simple and cost effective for fast manual operation (60 injections/h; y = 0.268x + 44.314, r2 = 0.9910 for 400 - 1000 mg/l and y = 0.1687x + 145.72, r2 = 0.9970 for 1000 - 2500 mg/l). The two SI systems with different components and configurations are automated and optimized for the conditions for which no extra dilution is to be required for sample handling: one with a syringe pump and two selection valves (60 samples/h; y = 0.1488x - 4.7297, r2 = 0.9946 for 400 - 1000 mg/l and y = 0.0858x + 63.933, r2 = 0.9849 for 1000 - 2500 mg/l); the other is simpler and more cost-effective, with an autoburette and only one selection valve (15 samples/h; y = 0.0072x + 1.1467, r2 = 0.9977 for 200 - 1000 mg/l and y = 0.0028x + 5.4699, r2 = 0.9879 for 1000 - 2500 mg/l). They have all been applied to assay paracetamol in pharmaceutical preparations. The obtained results agree with those by the US Pharmacopeia method.     

Employing peroxidase from Thai indigenous plants for the application of hydrogen peroxide assay

Thai local plants known as banana stalk, banana blossom, banana, sugar-cane, oroxylum indicum fruit, sesbania grandiflora fruit, and pigeon pea fruit were utilized for screening peroxidase enzyme to replace costly horseradish peroxidase in the hydrogen peroxide assay. The highest peroxidase activity was found in banana stalk extracted solution. The kinetic parameters, i.e., Michaelis–Menten constant (Km) and maximum velocity (Vmax) of banana stalk peroxidase were carried out. The optimum pH and thermal stability of this enzyme were also studied. Furthermore, crude banana stalk peroxidase was applied for the determination of hydrogen peroxide in a disinfection solution without any purification. The influent parameters affecting the developed method were cautiously studied and optimized. The calibration curve of standard hydrogen peroxide was achieved between 2.0 and 10.0 μmol L^?1 with correlation coefficient (r ²) 0.995. The method validations of detection limit (LOD), limit of quantification (LOQ) and precision were investigated. The concentrations of hydrogen peroxide achieved by the developed method were correlated with the enzymatic method using commercial available horseradish peroxidase.     

An affinity-based strategy for the design of selective displacers for the chromatographic separation of proteins

We describe an affinity-based strategy for designing selective protein displacers for the chromatographic purification of proteins. To design a displacer that is selective for a target protein, we attached a component with affinity for the target protein to a resin-binding component; we then tested the ability of such displacers to selectively retain the target protein on a resin relative to another protein having a similar retention time. In particular, we synthesized displacers based on biotin, which selectively retained avidin as compared to aprotinin on SP Sepharose high performance resin. In addition, we have extended this approach to develop an affinity-peptide-based displacer that discriminates between lysozyme and cytochrome c. Here, a selective displacer was designed from a lysozyme-binding peptide that had been identified and optimized previously using phage-display technology. Our results suggest a general strategy for designing highly selective affinity-based displacers by identifying molecules (e.g., peptides) that bind to a protein of interest and using an appropriate linker to attach these molecules to a moiety that binds to the stationary phase.