Analytical Sciences
Online ISSN : 1348-2246
Print ISSN : 0910-6340
ISSN-L : 0910-6340
Volume 19 , Issue 4
Showing 1-34 articles out of 34 articles from the selected issue
Reviews
  • Fuming XIE, Craig S. BRUNTLETT, Yongxin ZHU, Candice B. KISSINGER, Pet ...
    2003 Volume 19 Issue 4 Pages 479-485
    Published: 2003
    Released: November 19, 2003
    JOURNALS FREE ACCESS
    The preclinical bioanalytical process with animal models begins with sampling biological fluids and tissue. The goal is to understand oral absorption kinetics, distribution, metabolism, excretion, blood brain barrier penetration, drug-drug interactions, and the influences on biomarkers, hematology, electrophysiology, cardiology, blood pressure and behavior. An overview is obtained by periodic blood sampling of 8 - 12 samples over a total time span of 10 - 24h. Urine, feces, bile and microdialysates can augment the information available from whole blood. In today’s preclinical environment, the majority of samples are processed by LC/MSMS augmented by robotic sample preparation tools. These tools save labor and improve precision for smaller volume/lower concentration samples. Our laboratories have been engaged in a project that is focused on improving both the quality and throughput for laboratory animal studies, while providing for reduced numbers of animals and enhanced animal comfort. We have implemented a robotic system that can accomplish most of the above goals for laboratory rats, dogs and primates. Studies with mice are at an earlier stage, but feasibility has been demonstrated. This presentation is a progress report on this evolving research program in cooperation with multiple pharmaceutical and drug development companies. We will illustrate results and discuss future directions.
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  • Haruhiko SEYAMA, Mitsuyuki SOMA
    Type: Others
    Subject area: Others
    2003 Volume 19 Issue 4 Pages 487-497
    Published: 2003
    Released: November 19, 2003
    JOURNALS FREE ACCESS
    The surface chemical compositions of solid samples from environmental and geological sources can differ from the bulk or average compositions, because of changes caused by adsorption, dissolution, oxidation, etc. Accordingly, analytical information on surface layers is important for a better understanding of the environmental chemistry involving solid surfaces. The rapid development of surface-analytical techniques has enabled us to probe the surface chemistry of environmental and geological solid samples of complex composition. This article demonstrates some examples of important items of information that can be obtained by applying surface-analytical techniques, such as X-ray photoelectron spectroscopy and secondary ion mass spectrometry, to environmental and geological samples. The surface analysis of fly ashes, soils, sediments and weathered silicate minerals is reviewed.
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Original Papers
  • Sung Bae KIM, Takeaki OZAWA, Yoshio UMEZAWA
    Subject area: Others
    2003 Volume 19 Issue 4 Pages 499-504
    Published: 2003
    Released: November 19, 2003
    JOURNALS FREE ACCESS
    A new screening assay was described for the determination of endocrine disrupting chemicals (EDCs), such as synthetic estrogens, with an array-type DNA glass slide having characteristics of 1) a high sample throughput, 2) a compact size allowing a small sample volume, and 3) a sensitive determination based on the estrogen-dependent binding of the human estrogen receptor α (hERα) with its estrogen responsive element (ERE; Vit. A2 gene promoter). We devised a glass slide on which a thin agarose gel was mounted. Avidin was then covalently immobilized on each well of the glass slide after the gel was activated by a NaIO4 solution. Also, the biotinylated ERE as a DNA probe was immobilized on the gel layer through avidin-biotin binding. After the estrogen-dependent binding of a yellow fluorescent protein-fused hERα (YFP-hERα) to ERE on the gel layer, the fluorescence intensity of YFP-hERα quantitatively extracted into the gel was directly determined with a fluorescence microplate reader. Pre-incubation of YFP-hERα with estrogen at 37°C for 30min enhanced the estrogen-dependent hERα-ERE binding. The determined hormonal activities of estrogens on the interaction of YFP-hERα with ERE were as follows in their decreasing order: diethylstilbestrol (DES) > 17β-estradiol (E2) ≈ ethynylestradiol (EE2) > 4-hydroxy tamoxifen (OHT) > clomiphene (Clo). The present method provides a sensitive estrogen-dependent dose-response curve down to ∼10-13 M in the case of DES. This method will become a competitive alternative to the conventional in vitro assays, such as a DNA-binding assay using radioisotopes.
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  • Jozef ORLICKÝ, Katarína GMUCOVÁ, Ilja THURZO, Jur ...
    Type: Others
    Subject area: Others
    2003 Volume 19 Issue 4 Pages 505-509
    Published: 2003
    Released: November 19, 2003
    JOURNALS FREE ACCESS
    Aqueous solutions of ascorbic acid in unsupported and supported aqueous solutions and real samples were studied by the kinetics-sensitive double-step voltcoulommetric method with the aim to contribute to a better understanding of its behavior in biological systems. The data obtained from measurements made on analytes prepared in the laboratory, as well as those made on real samples (some commercial orange drinks, flash of the fresh fruits) point to the redox reaction of L-ascorbic acid (L-AH2) being very sensitive to both the presence of dissolved gaseous species (O2, CO2) and the ionic strenght in the analyte. Either the dissolved gaseous species, or the higher ionic strength caused by both the presence of supporting electrolyte and increased total concentration of ascorbic acid, respectively, give birth to the degradation of L-AH2. Naturally, the highest percentage of L-AH2 was spotted in fresh fruit.
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  • Mallipattu SREEDHAR, Tukiakula Madhusudana REDDY, Kami Reddy SIRISHA, ...
    Type: Others
    Subject area: Others
    2003 Volume 19 Issue 4 Pages 511-516
    Published: 2003
    Released: November 19, 2003
    JOURNALS FREE ACCESS
    A sensitive adsorptive stripping voltammetric method for the determination of dinitrophenolic herbicides, dinoseb (DSB) and dinoterb (DTB) at a bare carbon paste electrode (CPE) and a clay modified carbon paste electrode (CMCPE) was developed. A systematic study of various experimental conditions, such as the pH, accumulation variables and composition of a modifier on the adsorptive stripping response, were examined by using differential pulse voltammetry. A significant improvement was observed in the sensitivity by using the present method with CMCPE. When CMCPE was used, a linear response was obtained over the concentration range 2 × 10-10 to 3 × 10-7 M and 6 × 10-10 to 6 × 10-7 M with lower detection limits of 1 × 10-10 M and 5.4 × 10-10 M for dinoseb and dinoterb, respectively, at an accumulation time of 100 s. The interference from other herbicides and ions on the stripping signals of both compounds was also evaluated. The described method was applied to estimate of the dinoseb and dinoterb in environmental samples.
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  • Jianzhong LI, Purnendu K. DASGUPTA
    Type: scientific monograph
    Subject area: Infomation Science
    2003 Volume 19 Issue 4 Pages 517-523
    Published: 2003
    Released: November 19, 2003
    JOURNALS FREE ACCESS
    Atmospheric H2O2 is typically determined by enzymatically mediated fluorogenic reactions that do not discriminate between H2O2 and organic peroxides. Reactions of Ti(IV) with H2O2 has also been the basis of colorimetric measurements of H2O2 but is too insensitive. A more sensitive determination is possible with the Ti(IV)-4-(2-pyridylazo)resorcinol (PAR) complex, however, unreacted PAR must be chromatographically separated. A titanium(IV)-porphyrin complex, oxo[5,10,15,20-tetra(4-pyridyl)porphyrinato]titanium(IV) [TiO(tpypH4)4+], (TiTPyP) was introduced for the measurement of aqueous H2O2. In this paper, we show that TiTPyP can be used for measuring H2O2(g), it does not respond to CH3HO2. With a proper membrane collector, practically there is no interference from concurrently present gaseous SO2 and O3. The approach permits a S/N = 3 limit of detection (LOD) of 26 pptv with a 50 mm path liquid core waveguide (LCW) absorbance detector and a light emitting diode based light source. This is adequate for real atmospheric measurements.
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  • Katsumi SAITOH, Koichiro SERA, Tadashi SHIRAI, Tatsuji SATO, Matsuo OD ...
    Type: Others
    Subject area: Others
    2003 Volume 19 Issue 4 Pages 525-528
    Published: 2003
    Released: November 19, 2003
    JOURNALS FREE ACCESS
    The purpose of this study is to clarify the chemical characterization of PM2.5 and PM10 in diesel exhaust particles (DEP). Sampling of PM2.5 and PM10 in DEP was carried out in November 1999 using an automobile exhaust testing system at the National Traffic Safety and Environment Laboratory, with a diesel truck (engine type: direct injection, displacement: 7961 cc, carrying weight: 2020 kg, equivalent inertia weight: 5600 kg) placed on a chassis dynamometer. Sampling conditions included idling, constant speed of 40 km/h, M-15 test pattern and 60%-revolution/40%-load of maximum power. Samples were collected on a polycarbonate membrane filter (Nuclepore®, pore size: 0.8 μm) using a MiniVol Portable Air Sampler (Airmetrics Co., Inc.). The concentrations of several elemental and ionic species in the PM2.5 and PM10 samples were determined by particle induced X-ray emission (PIXE) and ion chromatography analysis. PIXE analysis of the PM2.5 and PM10 samples revealed 15 elements, of which Na, Mg, Si, S, Cl, Ca, Fe and Zn were found to be the major components. Ionic species were Cl-, No2-, No3-, So42-, Na+, NH4+, K+ and Ca2+. Concentrations of elements and ionic species under the sampling condition of 60%-revolution/40%-load were highest in comparison with those of the other sampling conditions. The elemental and ionic species data were compared for PM2.5 and PM10; PM2.5 concentrations were 70% or more of PM10 concentrations for the majority of elements, and concentrations of ionic species in PM2.5 and PM10 were almost identical.
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  • Ghiasse ABBASSE, Baghdad OUDDANE, Jean Claude FISCHER
    Type: Others
    Subject area: Others
    2003 Volume 19 Issue 4 Pages 529-535
    Published: 2003
    Released: November 19, 2003
    JOURNALS FREE ACCESS
    It is well-documented that organic compounds form strong complexes with most metals in aquatic systems, and that seawater is a complex medium which contains a large variety of organic and inorganic ligands, including colloidal matter. We suggest that most trace metals are complexed in seawater and that some inorganic metals complexes are either labile or not stable. In contrast, metal-organic complexes are often stable and need various and specific treatments to be dissociated. In this paper we try to illustrate a good tendency of some trace metals to be complexed by organic ligands in seawater. A solid-phase extraction method was applied using a C18 column as a resin that is able to separate metals complexed by neutral organic ligands, and the chelamine resin to separate metal species that are present as labile inorganic complexes. The determination of total dissolved metal concentrations was achieved by formatting a metal-8-hydroxyquinoline complex, followed by adsorption on C18 columns and ICP-AES analysis.
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  • Jongki HONG, Do-Gyun KIM, Jung-Ju SEO, Chulhyun LEE, Chaejoon CHUNG, K ...
    Type: Others
    Subject area: Others
    2003 Volume 19 Issue 4 Pages 537-542
    Published: 2003
    Released: November 19, 2003
    JOURNALS FREE ACCESS
    The electrical decomposition of 4-chlorophenol in water was examined with iridium dioxide doped on a titanium electrode. A number of electrical degradation products of 4-chlorophenol, such as hydroquinone and chlorohydroquinone via the addition of hydroxyl radicals, and dichlorophenol through addition of chlorine radical, were observed as major products. Moreover, hydroxylated chlorobiphenylethers, hydroxylated dibenzo-p-dioxin/furans and hydroxylated chlorobiphenyls formed by a dimerization process during the electrolysis process of 4-chlorophenol were also observed. On the other hand, benzoquinone, muconic acid and aldehyde derivatives that were further oxidative products of hydroquinone formed by photocatalysis process, were not observed. The electrical decomposition products of 4-chlorophenol were trimethylsilylated and then identified by gas chromatography-mass spectrometry. The degradation rate of 4-chlorophenol in water by iridium oxide electrode was measured against the electrical process duration. After iridium electrical process for 120 min, about 50% of 4-chlorophenol was converted into a number of products through oxidation processes. On the basis of the identified products, the degradation pathways of 4-chlorophenol under electrolysis process were proposed.
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  • Nobuko MAKIHATA, Tatsuhiko KAWAMOTO, Kiyoshi TERANISHI
    Type: Others
    Subject area: Others
    2003 Volume 19 Issue 4 Pages 543-549
    Published: 2003
    Released: November 19, 2003
    JOURNALS FREE ACCESS
    Ten carbamate pesticides including four suspected endocrine disruptors, methomyl, benomyl(carbendazim), aldicarb and carbaryl, were simultaneously analyzed by LC/ESI/MS. The influence of the matrix on the variation of the ion signal intensities of (M + H)+ and adduct ions was investigated. Although the intensities of three oxamyl ions changed depending on the matrix, the variation in the concentration calculation of oxamyl was reduced by using the sum total of the area value of two ions. The limits of the quantitation of ten pesticides without a concentration procedure were from 0.4-30μg/l. The solid-phase recovery rates of ten pesticides spiked into tap water and raw water were in the range of 69-111%. Using this method, the concentrations of the pesticides in tap and raw water sampled at 14 monitoring points in Hyogo Prefecture were determined. Carbendazim in three raw water samples and carbofuran in one of these three samples were detected at low concentrations (less than 0.32μg/l).
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  • Tomas NEZEL, Gleb ZHYLYAK, Gerhard J. MOHR, Ursula E. SPICHIGER-KELLER
    Type: Others
    Subject area: Others
    2003 Volume 19 Issue 4 Pages 551-556
    Published: 2003
    Released: November 19, 2003
    JOURNALS FREE ACCESS
    The reactions within a recently introduced NO2-sensitive polymeric membrane based on aquacyanocobalt(III)-cobyrinate are described. The detailed reaction mechanism was investigated in three ways: using UV/VIS-spectroscopy, determining the reaction products and investigating the influence of other gases. It could be shown that the membrane’s high sensitivity and selectivity derives from the remarkable reaction of NO2 with this cobyrinate derivative, which yields nitric and nitrous acid. This reaction can be transduced with a consecutive protonation of the included chromoionophore into an optical signal, which allows the detection of NO2 in the ppb-range.
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  • Chao LU, Jin-Ming LIN, Carmen W. HUIE, Masaaki YAMADA
    Type: Others
    Subject area: Others
    2003 Volume 19 Issue 4 Pages 557-561
    Published: 2003
    Released: November 19, 2003
    JOURNALS FREE ACCESS
    In the absence of any special luminescent reagents, a weakly chemiluminescent emission was observed during the decomposition of hydrogen peroxide, catalyzed by transition-metal ions, such as Cu(II) and Co(II), in basic aqueous solution. The chemiluminescent intensity was significantly enhanced by the addition of ethyldimethylcetylammonium bromide and uranine. The signal-to-noise ratio (S/N) was proportional to the concentrations of Cu(II) and Co(II). Based on these phenomena, a flow-injection chemiluminescent method for the simultaneous separation and determination of Cu(II) and Co(II) was developed. The detection limits of the present chemiluminescent method for Cu(II) and Co(II) were 7.5 and 0.01 ng/ml, respectively. After ion chromatographic separation of Cu(II) and Co(II) by an IonPac CS5A column with oxalic acid and lithium hydroxide monohydrate as the eluent, the present chemiluminescent system was used as a post-column detector for these two transition metal ions in natural water samples.
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  • Eleftheria T. MALLIOU, Constantinos G. ANTONIOU, John E. KOUNDOURELLIS
    Type: Others
    Subject area: Others
    2003 Volume 19 Issue 4 Pages 563-568
    Published: 2003
    Released: November 19, 2003
    JOURNALS FREE ACCESS
    Derivative spectrophotometric procedures and an isocratic high performance liquid chromatographic method for the determination of butamyrate citrate (Sinecod®, Safarol®) in cough syrups have been developed. In the spectrophotometric method, direct measurement of the drug at its absorption maxima is impossible because of interference from different absorbing excipients. Extraction of butamyrate citrate was performed with n-pentane/isopropyl alcohol. Quantification was carried out through the use of 1D derivative at a trough depth of 253.6 nm where interferences from other coextracted compounds are negligible. The extraction efficiency expressed as a % recovery and precision were assessed by fortifying placebo syrup(s) with known amounts of the compound. Also, a reversed phase high performance liquid chromatographic method was used with a mobile phase containing 0.015 M aqueous tetraethylammonium hydrogen sulfate, methanol and acetonitrile 40:30:30 adjusted to pH 3.50 with ammonium hydroxide. The retention behavior of butamyrate citrate as a function of both pH and salt concentration in the aqueous portion of the mobile phase was investigated. Quantification was achieved with UV detection at 258 nm based on peak area. The HPLC method clearly separates the analyte from its degradation products derived after storage of samples under different stress conditions such as acid, alkaline, temperature, oxygen and light. The described methods were successfully applied to the determination of butamyrate citrate in commercial pharmaceutical products and in placebo syrups prepared in the laboratory with good accuracy and precision. The results of the present study show that the use of the derivatives and the HPLC procedure provide precise and sensitive methods for the determination of the compound in pharmaceutical formulations.
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  • Masaki MIFUNE, Katsuyoshi SUGIMOTO, Akimasa IWADO, Hiromichi AKIZAWA, ...
    Type: Others
    Subject area: Others
    2003 Volume 19 Issue 4 Pages 569-573
    Published: 2003
    Released: November 19, 2003
    JOURNALS FREE ACCESS
    A flow injection analysis system of hydrogen peroxide was developed. The present system is based on measuring of the absorbance of a quinoid dye formed by the following reaction catalyzed by peroxidase: Phenol + 4-Aminoantipyrine + 2H2O2 → Quinoid dye + 4H2O. A column packed with aminopropyl-glass beads modified with a manganese(III)-tetra(4-carboxyphenyl)porphine derivative (Mn-TCPPG column), which has peroxidase-like activity, was used in place of an immobilized peroxidase column in the above reaction. The linear range of the calibration curve was 0.4 - 80 μg/ml hydrogen peroxide. The relative standard deviation of this system was 2.97% (n = 100, 10 μg/ml hydrogen peroxide 20 μl injection). The Mn-TCPPG column has sufficiently stability for the continuous injection of hydrogen peroxide untill 100 times. The advantageous feature of the Mn-TCPPG column was a less-electrostatic interaction between the mother glass beads and the anionic chromogen or quinoid dye formed and the stability in terms of the storage, temperature and moisture. The determination of serum glucose was achieved by attaching an immobilized glucose oxidase column to this system without deproteinization.
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  • Liande ZHU, Yingxiu LI, Guoyi ZHU
    Type: Others
    Subject area: Others
    2003 Volume 19 Issue 4 Pages 575-578
    Published: 2003
    Released: November 19, 2003
    JOURNALS FREE ACCESS
    A flow-injection electrochemiluminescent method for L-cysteine determination has been developed based on its enhancement of the electrochemiluminecence of luminol at a glassy carbon electrode. This method is simple and sensitive for cysteine determination. Under the selected experimental parameters, the linear range for cysteine concentration was 1.0 × 10-6 - 5.0 × 10-5 mol/l, and the detection limit was 0.67 μmol/l (S/N = 3). The relative standard deviation for 11 measurements of 1.0 × 10-5 mol/l cysteine was 4.5%. The proposed method has been applied to the detection of cysteine in pharmaceutical injections with satisfactory results.
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  • Jamshid L. MANZOORI, Ghasem KARIM-NEZHAD
    Type: Others
    Subject area: Others
    2003 Volume 19 Issue 4 Pages 579-583
    Published: 2003
    Released: November 19, 2003
    JOURNALS FREE ACCESS
    A new approach for developing a cloud-point extraction-flame atomic absorption spectrometric method has been described and used for the determination of cobalt. In this approach, water was removed from the final diluted surfactant rich phase obtained in cloud-point extraction procedure. The results indicated that removing water from this phase increased the enhancement factor by 4-fold. 1-(2-Pyridylazo)-2-naphthol (PAN) and octylphenoxypolyethoxyethanol (Triton X-114) were used as a hydrophobic ligand and a nonionic surfactant, respectively. The chemical variables affecting the preconcentration step were optimized. The effect of the water concentration in the final diluted methanolic surfactant solution on the analytical signal was investigated. The results showed that the analytical signal decreased by 30% and 52% in 15% and 25% water concentrations in methanol, respectively. An enhancement factor of 115 was obtained for cobalt extracted from only 10 ml of a sample. The detection limit obtained under the optimal condition was 0.38 μg l-1. The proposed procedure was applied to the determination of cobalt in urine samples.
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  • Junichi NAKAJIMA, Yoshihiro HIRANO, Koichi OGUMA
    Type: Others
    Subject area: Others
    2003 Volume 19 Issue 4 Pages 585-588
    Published: 2003
    Released: November 19, 2003
    JOURNALS FREE ACCESS
    A flow-injection on-line preconcentration-electrothermal atomic absorption spectrometric (ETAAS) method coupled with a coprecipitation method has been developed for the determination of lead in seawater. The combination of two preconcentration procedures, coprecipitation with iron(III) hydroxide and solid-phase extraction with a lead-selective resin, Pb·SpecTM, allowed the determination of lead at the ng kg-1 level. Lead in 250 g of a sample solution was collected by coprecipitation with 10 mg of iron. The precipitate was dissolved in 25 ml of 1 mol l-1 nitric acid; then, a 4-ml aliquot of the sample solution was introduced into the flow-injection system to preconcentrate and separate lead from iron on a Pb·Spec microcolumn. The sorbed lead was eluted with a 1.0 × 10-4 mol l-1 EDTA solution. The 30-μl portion of the eluate corresponding to the highest analyte concentration zone was injected into a graphite furnace. The overall enhancement factor was about 200 for 250 g of the sample. The average and standard deviation of ten blank values obtained were 1.7 ng and 0.38 ng, respectively. The recovery was 93.7 ± 5.0% for seawater spiked with 20 ng kg-1 lead. The proposed method is applicable to the analysis of seawater for lead at slightly higher levels.
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  • Han-wen SUN, Wei-jun KANG, Shu-xuan LIANG, Jing HA, Shi-gang SHEN
    Type: Others
    Subject area: Others
    2003 Volume 19 Issue 4 Pages 589-592
    Published: 2003
    Released: November 19, 2003
    JOURNALS FREE ACCESS
    A rapid and sensitive method has been proposed for the sequential determination of chromium(III) and total chromium in water samples by flame atomic absorption spectrometry combined with a flow injection on-line preconcentration on a double-microcolumn. The chromium(III) and total chromium in samples were retained on a double-microcolumn with a cation exchange resin, respectively, and eluted directly into a nebulizer by 3 mol L-1 HNO3. The characteristic concentration (gives a derivative absorbance of 0.0044) and the detection limit (3σ) for chromium were 0.512 μg L-1 and 0.647 μg L-1 for a preconcentration time of 1 min, respectively. This is an improvement of 20 and 14-times than those of conventional FI-FAAS. The proposed method allows the determination of chromium in the range of 0 - 90 μg L-1 with a relative standard deviation of 3.63% at the 10 μg L-1 level. The method has been applied for the analysis of chromium in reference water of National Research Center for Certified Reference Materials (GBW08607) and other water samples with satisfactory results.
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  • Hirofumi ISOYAMA, Tetsuo UCHIDA, Takashi NAGASHIMA, Osamu OHIRA
    Type: Others
    Subject area: Others
    2003 Volume 19 Issue 4 Pages 593-597
    Published: 2003
    Released: November 19, 2003
    JOURNALS FREE ACCESS
    A PTFE Babington nebulizer equipped with a hood was investigated for inductively coupled plasma atomic emission spectrometry in conjunction with a PTFE cyclone chamber, in order to nebulize various sample solutions containing high salts, hydrofluoric acid and/or suspended solid. A hood of 3 mmφ (nozzle side) - 5 mmφ (outlet side) and 6 mm in length gave a comparable or higher sensitivity compared to a system with a commercially available concentric nebulizer and a glass cyclone chamber. Moreover, the present nebulizer was fully interchangeable with a concentric one at normal argon pressure, attaining sufficient stability, a short wash-out time and good nebulizing of high matrices solutions. The present system was successfully applied to the determination of trace impurities in highly pure silica powders.
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  • O. DELGADO-VASALLO, J.L. PEÑA, E. San Martín MARTÍ ...
    Type: Others
    Subject area: Others
    2003 Volume 19 Issue 4 Pages 599-602
    Published: 2003
    Released: November 19, 2003
    JOURNALS FREE ACCESS
    We report here on the use of the photoacoustic technique for the determination of low concentrations of total iron in corn meal samples. The determination of this element in food is of considerable interest because several foods are currently enriched with it at proper levels in order to increase the resistance of people, after consumation, to several diseases, such as anemia. The proposed technique is based on an open photoacoustic cell configuration in conjunction with a suitable colorimetric method. We applied it to a measurement of the total iron concentration in corn meal samples. The results agree very well with those obtained using a conventional spectrophotometric method, showing the possibilities of new experimental methodologies based on photothermal methods to perform this kind of study, with the advantage of a higher sensitivity and increment of the range of appreciable absorbance.
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