1,485 research outputs found
Computer-controlled ion-selective electrode switch
The construction of a microcomputer-controlled electrode switch for
use in potentiometric determinations is described. This can be coupled to most of the analytical equipment usually found in laboratories, to enable a setting up of automatic systems capable of performing sequential determinations with several ion-selective
electrodes. The assessment of its analytical usage and behaviour are discussed
Usefulness of a detector inlet overpressure and stream splitting in FIA systems to deal with food sample pre-treatment requirements. Application to wine analysis
The use of stream splitting to obtain high sampling rate flow injection analysis (FIA) large dispersion manifolds to deal with pre-treatment requirements in the analysis of food components with a high concentration is described. This procedure is illustrated in the FIA determination of calcium using an atomic absorption detector and in the colorimetric determination of phosphate in wines. These manifolds proved to be an advantageous alternative to those including mixing chambers and diluters, as they are simpler and provide higher sampling rates (60–240 samples h−1 are achieved). Also described here is the use of an overpressure at the entrance to the atomic absorption nebulizer to minimize matrix physical interferences, by presenting the results obtained for the FIA—atomic absorption copper determination in wines. The results obtained for several wine samples by the developed FIA methodologies were in good agreement with those provided by the reference methods
Determination of metoprolol, acebutolol and propranolol in pharmaceutical formulations using the same SIA system
A mechanized system for the determination of beta-blockers in pharmaceutical formulations is presented. Using the Sequential Injection Analysis (SIA) technique it was achieved a simple, economical and versatile methodology adaptable to any pharmaceutical control involving these substances. It does not require any pre-treatment for the samples, as they must only be dissolved in acid before analysis. Linear calibration plots were obtained for metoprolol (40.52 - 250 mg L-1), acebutolol (32.85 - 140 mg L-1) and propranolol (16.58 - 120 mg L-1). A R.S.D. lower than 5% was attained. The methodology was used in tablets, injections and prolonged-release capsules. Common excipients used in pharmaceuticals do not interfere. Statistical comparison of the results obtained with the proposed methodology and with the official methods showed good agreement (95% confidence level). SIA system produces only 2.50 mL of effluents per determination whereas the reference methodologies consume around 140 mL
Inhibition of human neutrophil oxidative burst by pyrazolone derivatives
The risk of agranulocytosis associated with the use of pyrazolone drugs at therapeutical doses and for short periods of time has been considered
to be very low. However, little or no attention at all has been devoted to the possible hindrance of neutrophil burst and scavenging of neutrophilgenerated
reactive oxygen species (ROS) by these compounds. Such an effect could be beneficial in the case of overactivation of neutrophils but
could also be highly detrimental if the number of circulating neutrophils is already decreased. Thus, the aim of the present study was to evaluate
the putative inhibitory effect of the pyrazolones dipyrone, aminopyrine, isopropylantipyrine, and antipyrine against human neutrophil burst and
their scavenging activity against O2
S!, H2O2, HOS, ROOS, and HOCl. The obtained results showed that dipyrone and aminopyrine prevent
phorbol-12-myristate-13-acetate-induced neutrophil burst with high efficiency, while isopropylantipyrine had little effect and antipyrine had no
effect at all. Dipyrone and aminopyrine were highly potent scavengers of HOS and HOCl, while, in accordance with the neutrophil burst results,
isopropylantipyrine had little effect and antipyrine had no effect at all against these two ROS. None of the studied pyrazolones was capable of
scavenging O2
S! or H2O2, while dipyrone was shown to be the most reactive against ROOS
Sequential injection system for the spectrophotometric determination of reducing sugars in wines
A sequential injection system for the spectrophotometric determination of reducing sugars in wines is described.
The methodology is based on the formation of a coloured complex produced by the reaction of copper (I) with
2,9-dimethyl-1,10-phenanthroline (neocuproine), after reduction of copper (II) to copper (I) by reducing sugars. In the
present SI system, a dialysis unit was incorporated not only to allow the sample dilution, but also to minimise the
interference of some coloured compounds. In this way, direct sample introduction into the system was possible,
without any previous treatment of the wine samples. The proposed method can be applied to the determination of
reducing sugars in two concentration ranges: from 2 to 25 g l 1 (table wines) and from 20 to 140 g l 1 (Port wines).
To perform determinations in these two ranges, the manifold configuration remained the same; just a few operational
parameters were changed in the controlling software. A sampling-rate of 14–18 samples per hour was obtained with
good repeatability for ten consecutive injections of wine samples (relative standard deviations (RSD) B2.1%). The
results obtained from 19 wine samples were comparable to those obtained by the reference method.info:eu-repo/semantics/publishedVersio
Determination of iron in soils by flow injection atomic absorption spectrometry
A single-channel flow injection system was optimized for the determination
of available iron (Fe) in soil extracts by atomic absorption spectrophotometry.
This method of introducing the samples in the spectrophotometer worked
particularly well in preventing blockage of the burner head which was
observed in the conventional introduction of Fe for its determination by atomic
absorption spectrophotometry. The appropriate selection of the manifold
parameters, such as injection volume, tube length and flow rate, allowed
introduction of any soil extract without requiring any pre-treatment. This
system allowed determinations at a detection limit of 0.36 mg L-1 to 5 mg L-1,
with an output of 300 determinations per hour. The results obtained for
analysis of 15 soil extracts were in good agreement with those provided by
the colorimetric method, with average relative deviations of 1.6%. Relative
standard deviations of 4.8, 2.5, and 2.3% were obtained for contents of 1.03,
1.85, and 3.99 mg Fe L-1, respectively
Flow injection systems for elemental soil analysis determinations
Flow injection analysis (FIA) is becoming an important automated procedure
for the elemental analysis of agricultural and environmental samples. This
paper reviews the application of the FIA technique for soil elemental analysis
determinations, giving short descriptions of the required flow manifolds by
highlighting some of their most important features
Determination of aluminum (III) in crystallized fruit samples using a multicommutated flow system
A multicommutated flow system was developed for the determination of aluminum in crystallized
fruit samples. Spectrophotometric determination is based on the reaction of aluminum with chrome
azurol S. The binary sampling technique was implemented to improve mixing conditions and to
minimize reagent consumption. Three different working zones were established (0.5-5.0, 5.0-25.0,
and 10.0-100 ppm) using the zone sampling approach, allowing us to adapt the extent of the in-line
dilution. The influence of the chemical and physical parameters on the performance of the system
was studied. Detection limits of 0.1, 0.6, and 0.8 ppm were obtained for the lowest, the medium, and
the highest dispersion system, respectively. The procedure was applied to the determination of
aluminum in crystallized fruit extracts. The results were in agreement with those obtained by the
reference flame atomic absorption procedure at a 95% confidence level. Repeatability (RSD) was
better than 2.4% in all of the three application zones
Automatic miniaturized flow methodology with in-line solid-phase extraction for quinine determination in biological samples
The present work describes an analytical platform based on a multipumping flow injection analysis (MPFS) technique combined with in-line solid-phase extraction (SPE). The flow network has been tested with the determination of quinine in biological samples using fluorometry as the detection technique. Amberlite XAD-4 resin has been used as a solid phase and the implementation of a pH control strategy resulted in a simple and environmental approach for the preconcentration of quinine.
Two solenoid valves allowed the deviation of the flow towards the resin column to carry out SPE procedures. The influence of parameters such as concentration, flow rate and volume of the different solutions on the sensitivity and performance of the MPFS was studied. Dynamic calibration ranges (0.78–150 ng mL 1) for quinine determination were applied by using a variable sample volume (120– 1000 mL). The developed methodology provided high relative extraction recoveries from human urine samples (85–115%). The proposed automatic methodology turns out to be very efficient and sustainable compared to the available procedures and it could prove to be an attractive alternative tool to perform in-line sample pre-treatment and subsequent direct determination of relevant organic compounds in pharmaceutical and clinical analyses
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