Determination of oligoelements in parenteral formulations by planar chromatography and spectrophotometry

The authors have studied the chromatographic behavior of parenteral preparations for pediatric use containing inorganic cations. After separation and identification by thin-layer chromatography, Mn2+, Zn2+, and Cu2+ were analyzed by a method based on reaction with an appropriate reagent and extraction with an organic solvent which yielded elution and preconcentration, resulting in an appropriate solution for colorimetric quantitation. Cr3+ cation was determined by atomic absorption spectrophotometry after appropriate chromatographic separation, using microcrystalline cellulose (adsorbent) and an acetone:water:hydrochloric acid mixture (80:5:8) as the mobile phase.

Measurement of atmospheric formaldehyde using a drop collector and in-situ colorimetry

A sensitive and affordable approach is described for the in-situ measurement of ambient formaldehyde. Air is sampled around a 100 microliter aqueous drop containing 3-methyl-2-benzothiazoline hydrazone. After a desired period of sampling (typ. 5 min) and a waiting period of 10 min for the reaction to be completed, a second reagent (FeCl3) is added to the drop by means of a conjoined conduit. A blue product is formed and is read after an additional 10 min of reaction by a fiber-optic/light emitting diode based photodetector. A fresh drop is then formed and the process begins anew. As demonstrated here, the limit of detection is similar to 6.25 mu g m(-3) HCHO but can be significantly improved by using longer sampling times and a sampling rate higher than 100 mi min(-1) used in most of this work. This is the first example of a chromogenic drop sensor that utilizes sequential reagent addition.

Decomposição de argilas em forno de microondas e determinação simultânea dos seus constituintes principais por espectrometria de emissão óptica em plasma indutivamente acoplado

ANALYSIS OF CLAYS BY INDUCTIVELY COUPLED PLASMA OPTICAL EMISSION SPECTROMETRY AFTER CLOSED-VESSEL MICROWAVE-ASSISTED ACID DECOMPOSITION. In this work a closed-vessel microwave-assisted acid decomposition procedure for clays was developed. Aluminum, Ca, Fe, K, Mg, Na, Si, and Ti were determined in clay digestates by inductively coupled plasma optical emission spectrometry. The most critical parameter for total decomposition of clays was the composition of the reagent mixture. The applied power and the heating time exerted a less critical influence. Best decomposition conditions were attained using a reagent mixture containing 4 mL aqua regia plus 3 mL HF and the heating program was implemented in 12 min. The accuracy of the results was demonstrated using two standard reference materials and a paired t-test showed a good agreement between determined and certified values at a 95% confidence level.

A Semi-Continuous Analyzer for the Fluorimetric Determination of Atmospheric Formaldehyde

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Electrochemistry of organometallic compounds. Part II. Oxidations of alkyl and aryl derivatives of bis(salicylaldehyde)ethylenediimine cobalt(III) in dimethylformamide

The influence of the axial organic ligand R on the electrochemical oxidation of the compounds [RCoIII(salen)DMF)], where salen is bis(salicylaldehyde)ethylenediimine, and R CH3, C2H5, n-C3H7, n-C4H9, s-C4H9, i-C4H9, CH2Cl, CF3CH2, c-C6H11CH2, c-C6H11, C6H5, C6H5CH2, p-CH3C6H4CH2, and p-NO2C6H4CH2, was studied by means of cyclic voltametry in dimethylformamide (DMF), 0.2 M in tetraethylammonium perchlorate (TEAP), at 25 and -20°C, with a platinum disc working electrode. The above-mentioned compounds can be classified according to their electrochemical behavior. (a) The complexes with R CH3, C2H5, n-C3H7, n-C4H9, c-C6H11CH2, and C6H5 undergo a reversible one-electron oxidation in the 10-50 V s-1 potential scan range. At slower scan rates, the oxidized product decomposes chemically. At -20°C, this chemical step is slow, and a reversible one-electron electrochemical oxidation is observed. (b) The compounds with R CH2Cl, C6H5CH2, p-CH3C6H4CH2 and p-NO2C6H4CH2 undergo a quasi-reversible one-electron oxidation at room temperaure. At -20°C, the electrochemical process becomes more complex. A following chemical reactions is coupled to the quasi-reversible one-electron transfer. Two reduction peaks are observed. (c) The compounds with R i-C4H9, s-C4H9, and c-C6H11 undergo a reversible one-electron oxidation at -20°C. At room temperature, the irreversible chemical reaction following the electron transfer step is too fast to allow the isolation of the electrochemical step. (d) At -20°C, the derivatives with R C2H5, c-C6H11 CH2 and c-C6H11 are adsorbed at the electrode surface. Evidence indicates that the reagent in these reactions is the pentacoordinated species [RCoIII(salen)]. A linear free-energy relationship between E1/2 (for reversible processes) and the Taft polar parameters o* was obtained with a slope of ρ* = 0.25 ± 0.03. As expected, the benzyl derivatives which present mesomeric effects do not fit this polar correlation. The rated of the electrochemical oxidation is also affected by the nature of the ligand R. For the ligands which are strong electron-withdrawing groups and for the benzyl derivatives, the rate of the electrochemical oxidation of the metal ion decreases at room temperature. At lower temperatures, it is suggested that the oxidation to the CoIV-R species is followed by a chemical reaction in which this complex is partly transformed into a CoIII(R*) species, which is reduced at a much more cathodic potential than the Co(IV) species. © 1979.

OBTENCAO DE MESALAZINA (5-ASA) POR CARBOXILACAO DE P-AMINOFENOL

The 5-aminosalicylic acid is usually prepared: 1. by the reduction of the azodye from diazotized aniline and salicylic acid and the posterior reduction of the formed compound; 2. for carboxylation with carbon dioxide under high pressure of p-aminophenol. Both do not present high yield, but the carboxylation process of p-aminophenol can easily be used and can reduce the obtainment process of 3 steps to only 2. Another advantage of this process is the fact that the product is produced without contaminants, because only one solid reagent (p-aminophenol) and the agent of carboxylation (CO2) is used.

Analytical chemistry in a liquid film/droplet

The measurement of nitrogen dioxide at the parts-perbillion level is described. The experimental arrangement consists of two optical fibers placed on opposite sides of and in contact with a liquid film (14-57 μL in volume) supported on a U-shaped wire guide and two tubular conduits (one of which constitutes the means for the delivery of the liquid), light from a green (555 nm) light-emitting diode enters the liquid film, composed of Griess-Saltzman reagent. The transmitted light is measured by a referenced photodetection arrangement. Sample gas flows past the droplet at a low flow rate (typically 0.10-0.25 L/min). The response is proportional to the sampling period and the analyte concentration. The limit of detection for this nonoptimized arrangement is estimated to be <10 ppb by volume for a 5 min sample. Some unusual characteristics are observed. The initial absorbance, when most of the analyte/reaction product is still near the surface, is higher than that when the content of the droplet is fully mixed. The signal depends on the sample flow rate in a nonmonotonic fashion, first increasing and then decreasing with increasing sampling rate; the specific chemistry involved in the collection and determination of NO2 may be responsible.

Characterization of a monoclonal antibody recognizing mast cells

Immunohistochemical screening for monoclonal antibodies prepared by immunization of mice with a rat osteoblastic cell population led to identification of one antibody that reacted against a small population of cells present in the soft connective tissue compartment of 21 days fetal rat calvaria. The morphology of the cells and the immunohistochemical staining characteristics (a distinct intracellular granular pattern) suggested that the antibody might be reacting specifically against mast cells. We used combined histochemistry and immunohistochemistry to further characterize this antibody, designated RCJ102. Cryosections containing calvaria bone, soft connective tissues and skin were prepared from the top of the head of 21 days fetal rats, and from adult rats cryosections of lung, muscle, adipose tissue and small intestine were prepared. Some sections were labelled by indirect immunofluorescence with RCJ102; corresponding sections were labelled histochemically with toluidine blue. There was a direct correspondence between mast cells identified histochemically and cells labelling with RCJ102 in all tissues except intestine, in which the mast cell detectable by histochemistry were not labelled by RCJ102. These results suggest that the RCJ102 antibody will be a valuable new reagent for further elucidation of the heterogeneity described between connective tissue and intestinal mucosal mast cells.

Spectrophotometric determination of manganese in steels by on-line electrochemical oxidation

The aim of this work is to propose a flow spectrophotometric procedure for manganese determination in steel based on electrochemical oxidation of Mn(II) to Mn(VII) at a Pt electrode surface by means of the catalytic effect of Ag(I). The on-line oxidation step was obtained by injecting sample and electrolyte solution directly into an electrolytic cell. After electrolysis, the injectate was homogenized by bubbling air. The permanganate ions produced were passed through the spectrophotometer where absorbance was monitored at 545 nm. Effects of direct current, silver concentration, timing, flow rates, concentration and composition of support electrolyte were investigated. Direct current and silver content manifested themselves as the most relevant parameters. For determination of manganese in the 5.00 - 150 mg L -1 range (r=0,9998) and 60 s electrolysis time, the sample throughput was 20 h -1. Accuracy was assessed by analyzing ten steel standard reference materials. Results are precise (R.S.D. <3%) and in agreement with certified values of reference materials and with standard methods at 95% confidence level.

Determination of mercury in agroindustrial samples by flow-injection cold vapor atomic absorption spectrometry using ion exchange and reductive elution

A flow-injection system with a Chelite-S® cationic resin packed minicolumn is proposed for the determination of trace levels of mercury in agroindustrial samples by cold vapor atomic absorption spectrometry. Improved sensitivity and selectivity are attained since mercuric ions are on-line concentrated whereas other potential interferents are discarded. With on-line reductive elution procedure, concentrated hydrochloric acid could be replaced by 10% w/v SnCl2, in 6 M HCl as eluent. The reversed-intermittent stream either carries the atomic mercury, to the flow cell in the forward direction or removes the residue from reactor/gas liquid separator to a discarding flask in the opposite direction. Concentration and volume of reagent, acidity, flow rates, commutation times and potential interfering species were investigated. For 120 s preconcentration time, the proposed system handles about 25 samples h-1 (50.0 500 ng l-1), consuming about 10 ml sample and 5 mg SnCl2 per determination. The detection limit is 0.8 ng l-1 and the relative standard deviation (RSD) (n = 12) of a 76.7 ng l-1 sample is about 5%. Results are in agreement with certified value of standard materials at 95% confidence level and good recoveries (97-128%) of spiked samples were found. (C) 2000 Elsevier Science B.V.

Cloning, overexpression, and purification of functional human purine nucleoside phosphorylase

Purine nucleoside phosphorylase (PNP) catalyzes the phosphorolysis of the N-ribosidic bonds of purine nucleosides and deoxynucleosides. A genetic deficiency due to mutations in the gene encoding for human PNP causes T-cell deficiency as the major physiological defect. Inappropriate activation of T-cells has been implicated in several clinically relevant human conditions such as transplant tissue rejection, psoriasis, rheumatoid arthritis, lupus, and T-cell lymphomas. Human PNP is therefore a target for inhibitor development aiming at T-cell immune response modulation. In addition, bacterial PNP has been used as reactant in a fast and sensitive spectrophotometric method that allows both quantitation of inorganic phosphate (Pi) and continuous assay of reactions that generate P i such as those catalyzed by ATPases and GTPases. Human PNP may therefore be an important biotechnological tool for P i detection. However, low expression of human PNP in bacterial hosts, protein purification protocols involving many steps, and low protein yields represent technical obstacles to be overcome if human PNP is to be used in either high-throughput drug screening or as a reagent in an affordable P i detection method. Here, we describe PCR amplification of human PNP from a liver cDNA library, cloning, expression in Escherichia coli host, purification, and activity measurement of homogeneous enzyme. Human PNP represented approximately 42% of total soluble cell proteins with no induction being necessary to express the target protein. Enzyme activity measurements demonstrated a 707-fold increase in specific activity of cloned human PNP as compared to control. Purification of cloned human PNP was achieved by a two-step purification protocol, yielding 48 mg homogeneous enzyme from 1 L cell culture, with a specific activity value of 80 U mg -1. © 2002 Elsevier Science (USA). All rights reserved.

Spectrophotometric flow-injection determination of sulphite in white wines involving gas diffusion through a concentric tubular membrane

A flow-injection system is proposed for the spectrophotometric determination of sulphite in white wines. The method involves analyte conversion to SO2, gas diffusion through a Teflon® semi-permeable membrane, collection into an alkaline stream (pH 8), reaction with Malachite green (MG) and monitoring at 620 nm. With a concentric tubular membrane, the system design was simplified. Influence of reagent concentrations, pH of donor and acceptor streams, temperature, timing, surfactant addition and presence of potential interfering species of the wine matrix were investigated. A pronounced (ca. 100%) enhancement in sensitivity was noted by adding cetylpyridinium chloride (CPC). The proposed system is robust and baseline drift is not observed during 4 h operating periods. Only 400 μL of sample and 0.32 mg MG are required per determination. The system handles 30 samples per hour, yielding precise results (r.s.d. < 0.015 for 1.0 - 20.0 mg L-1 SO2) in agreement with those obtained by an alternative procedure.

Quantitative analysis of potentially toxic metals in alginates for dental use

Alginate is one the materials most employed in practice to make dental impressions. Substances like zinc, cadmium and lead silicate, which are included in several alginate brands with the aim of improving their physical, chemical and mechanical properties, are a source of serious concern as regards their toxicity. The most serious chronic effect of oral exposure to cadmium is renal toxicity. Assimilation of lead has deleterious effects on the gastrointestinal tract, hematopoietic system, cardiovascular system, central and peripheral nervous systems, kidneys, immune system, and reproductive system. Chronic oral exposures to zinc have resulted in hypochromic and microcyte anemia in some individuals. The aim of the present study was to measure the cadmium, lead and zinc contents of seven brands of alginate for dental use on sale in Brazil. The samples were weighed and placed in the Teflon cups of a closed-system microwave oven. Aqua regia (4mL concentrated HCI:HNO3, 3:1 v/v) and hydrofluoric acid (2mL concentrated HF) were added to the samples, which were then subjected to heating. The samples were then cooled to room temperature and diluted to 25 mL in deionized water in a volumetric glass flask. The samples were diluted in duplicate and analyzed against a reagent blank. The analyses were performed in an atomic absorption flame spectrophotometer. Neither lead nor cadmium was detected. Zinc contents ranged from 0.001% to 1.36% by weight. The alginates exhibited low contents of the metals under study and gave no cause for concern regarding toxicity; even so, it is advisable to monitor potentially toxic materials continually and to analyze their plasmatic levels in the professionals working with them.

Emprego do reagente de fenton como agente coagulante na remoção de substâncias húmicas de água por meio da flotação por ar dissolvido e filtração

Fenton 's reagent was used as coagulant agent to treat water with high true color (100 ± 5 HU) caused by the introduction of humic substances extracted from peat, using dissolved air flotation. The pair value of coagulant dosage x coagulation pH was optimized to posterior construction of coagulation diagrams, reaching apparent color removal efficiency slightly superior to 60%. It was tried to simulate a treatment with complete cycle, carrying out an experiment with sand filtration after flotation, obtaining an effluent with excellent quality, presenting remnant apparent color, turbidity and absorbance of 253.7 nm less or equal to 2 HU, 0.40 TU and 0.009 cm -1, respectively, and residual total iron < 0.005 mg/L and DOC < 0.001 mg/L.

Agronomic effectiveness of cationic phosphate impurities present in superphosphate fertilizers as affected by soil pH

The general concept that low-water-soluble phosphorus (P) fertilizers should be more agronomically effective when applied to acidic soils was developed based on sources containing mainly calcium (Ca)-P compounds, but it may not hold true for sources with different chemical composition. To obtain information related to this issue, two important iron (Fe)-potassium (K)-P compounds present in superphosphates [Fe 3 KH 8 (PO 4 ) 6·6H 2 O, H8, and Fe 3 KH 14 (PO 4 ) 8·4H 2 O, H14] were prepared and characterized. These P sources were used to provide 30 and 60 mg P kg -1 as neutral ammonium citrate (NAC)+H 2 O-soluble P. Reagent-grade monocalcium phosphate (MCP) was used as a standard P source with high water solubility with an additional rate of 120 mg P kg -1 included. Also, mixtures of both Fe-K-P compounds and MCP were prepared to provide 0, 25, 50, 75, and 100% of the total P as MCP. All sources were applied to a clayey loamy acid soil (pH 5.3) classified as Rhodic Kanhapludult. The soil was incubated at two rates (0 and 10 g kg -1 ) of lime, which resulted in pH 5.4 and 6.8. Upland rice was cultivated to maturity. The H14 compound confirmed to be a highly effective source of P for the rice plants at both soil pH, as opposed to the H8, which was poorly effective when applied alone. When mixed with water-soluble P (WSP), the H8 was able to provide P to the plants with the maximum yield of upland rice reached with 54.8 and 80.5% of WSP for pH 5.4 and 6.8, respectively. The high agronomic performance of the H14 compound clearly indicates that this low-water-soluble P source cannot be deemed as ineffective at high soil pH. Copyright © Taylor & Francis Group, LLC.