Search results for "Calibration"
showing 10 items of 890 documents
Building energy performance forecasting: A multiple linear regression approach
2019
Abstract Different ways to evaluate the building energy balance can be found in literature, including comprehensive techniques, statistical and machine-learning methods and hybrid approaches. The identification of the most suitable approach is important to accelerate the preliminary energy assessment. In the first category, several numerical methods have been developed and implemented in specialised software using different mathematical languages. However, these tools require an expert user and a model calibration. The authors, in order to overcome these limitations, have developed an alternative, reliable linear regression model to determine building energy needs. Starting from a detailed …
Determination of Phenol by Preconcentration‐Direct Chemiluminescence in a FIA Assembly
2005
Abstract The determination of phenol in water samples is proposed with the aid of a flow‐injection system. The analytical procedure is based on the direct chemiluminometric emission by oxidation of the analyte with potassium permanganate in acidic medium. The flow assembly is provided with a solid‐phase reactor filled with a resin type XAD‐4 for analyte preconcentration. A large study of potential interferences, namely, amino acids reaching water through degradation of organic matter; metals and inorganic metal ions typically present in water interfering with the CL emission of the parent compound, was performed. The calibration graph was linear over the phenol concentration range 1.0–20.0 …
Photo‐Induced Chemiluminometric Determination of Acrolein in a Multicommutation Flow Assembly
2007
Abstract This paper deals with the determination of acrolein based on a strategy provided with a sensitive detection, the chemiluminescence; a “clean chemical” analyte treatment, the on‐line UV‐irradiation; and, a simple and quick automated system, the emergent multicommutation continuous‐flow methodology. The pesticide solution is irradiated (stopped‐flow) for 30 s; then, the resulting solution is introduced to the flow‐cell after being alternated with segments of the stream formed by potassium permanganate in strong acid solution and ethanol segments. The calibration range, from 1 to 1 mg l−1, resulted in a linear behavior over the range 5–100 µg l−1 and fitting the linear equation: I=75.…
Selection of calibration set samples in determination of olive oil acidity by partial least squares–attenuated total reflectance–Fourier transform in…
2003
Abstract A chemometric method has been applied for the determination of the free fatty acid (FFA) concentration in commercial olive oil samples of different types an origins by using Fourier transform infrared spectroscopy (FTIR) attenuated total reflectance (ATR) measurements. Different methods for selecting the training set, including hierarchical cluster analysis, were applied and compared. The prediction capabilities of partial least squares (PLS) multivariate calibration methods, net analyte signal (NAS) preprocessing followed by PLS or classical least squares (CLS) regression method of ATR–FTIR data were evaluated. Several aspects, like spectral range to be considered, different prepr…
Determination of carbonates in waters by on-line vapor generation FTIR
1998
Abstract An electrically heated gas-permeation unit (GPU) has been employed for the vapor-generation Fourier transform infrared (FTIR) determination of total carbonate in waters. The developed method is based on the simultaneous injection of 100 μ l sample and 100 μ l nitric acid in a two-channel manifold with a merging zone, which provides the generation of CO 2 through the GPU, heated at 90°C, from which CO 2 is swept by a stream of N 2 to a long-path infrared gas cell. Absorbance measurements were made in the range from 2500 to 2150 cm −1 and the corresponding flow injection recordings were obtained as a function of time. The areas of these peaks are interpolated in a calibration equatio…
Flow spectrophotometric determination of ammonium ion
1999
Abstract A flow procedure is proposed for the determination of ammonium ion. The sample in basic medium is forced through a solid-phase reactor containing immobilized AgCl on polymeric pearl beads. The released Ag + , complexed with the ammonia, gives a blue ternary complex with the aid of bromopyrogallol red and 1,10-phenanthroline which is spectrophotometrically monitored at 636 nm. The calibration graph is linear over the range 1–20 μg ml −1 ammonium ion, detection limit ( s / n = 3) 0.35 μg ml −1 and relative standard deviation (slope) 1.9 % ( n = 7). The sample throughput is 48 h −1 . The influence of foreign compounds is studied and the procedure is applied to ammonium ion determi…
Determination of aluminum at the parts per billion level by solvent extraction and flame atomic emission spectrometry
1991
A new method for the determination of aluminum at the parts per billion level, by N 2 O/ C 2 H 2 flame emission spectrometry with prior solvent extraction with acetylacetone or 8-hydroxyquinoline in 4-methylpentan-2-one, has been performed. The influence of extraction conditions and instrumental parameters on the sensitivity, precision, and dynamic range of the emission calibration curves have been studied. The limit of detection is between 5 and 10 ppb for both ligands, the variation coefficient being 0.2 and 3% at levels of 75 and 25 ppb, respectively. The method has been applied to the determination of Al in water and the results obtained are compared with those found by the standard add…
Development and characterization of a thermal inkjet-based aerosol generator for micro-volume sample introduction in analytical atomic spectrometry
2011
A novel system for the introduction of liquid samples into analytical plasmas for atomic spectrometric analysis is presented in this manuscript for the first time. The proposed “drop-on-demand” (DOD) aerosol generator is based on the use of a modified thermal inkjet cartridge. This system employs a lab-built microcontroller, which allows accessing all parameters important for driving the dosing cartridge for the generation of pL-droplets from sample volumes in the μL range. The droplet generation frequency, thus the resulting liquid flow rate, is variable over a wide range from the generation of isolated droplets up to a theoretical flow rate of approximately 2 mL min−1, with parallel opera…
Determination of chromium(III) and chromium(VI) in mineral water by bidirectional electrostacking and electrothermal atomic absorption spectrometry
2001
Abstract A feasibility investigation was carried out on the use of bidirectional electrostacking for simultaneous separation and pre-concentration of Cr(III) and Cr(VI) and their electrothermal atomic absorption spectrometry (ETAAS) determination. The bidirectional electrostacking manifold was improved, and the effects of sample tube cross-section and electrostacking time on the pre-concentration factor were investigated. Results indicate that the sample tube cross-section and electrostacking time are the main influence factors on the electrostacking pre-concentration, as well as the electric field strength and ionic mobility. The method developed was suitable for the simultaneous separatio…
2,4,6-Triphenylpyrylium Ion Encapsulated into Zeolite Y as a Selective Electrode for the Electrochemical Determination of Dopamine in the Presence of…
2002
2,4,6-Triphenylpyrylium ion immobilized inside the supercages of zeolite Y enhances by 1-2 orders of magnitude the response of electrochemical oxidation of dopamine in neutral aqueous media accompanied by a remarkable inhibition of post-electron-transfer reactions. The negative charge of the zeolite framework in which the 2,4,6-triphenylpyrylium ion is incorporated blocks the electrochemical oxidation of the negative ascorbate ion, enabling the determination of micromolar concentrations of dopamine in the presence of a large excess (10(3)-10(4) times) of ascorbate in phosphate buffer (pH 7.4). Under optimized conditions, linear calibration plots were obtained for a differential pulse detect…