共查询到20条相似文献,搜索用时 62 毫秒
1.
V. A. Maihara I. B. Gonzaga V. L. Silva D. I. T. Fávaro M. B. A. Vasconcellos S. M. F. Cozzolino 《Journal of Radioanalytical and Nuclear Chemistry》2004,259(3):465-468
Due to its essential characteristics, the daily dietary selenium intake of individuals should be monitored accurately. In the current work, daily selenium intake of different Brazilian population groups based on duplicate portion diet analysis was evaluated and compared with the new estimated average requirement values (EAR), to assess if selenium deficiency or excess could be observed in these groups. Selenium content was determined by neutron activation analysis (NAA). The average daily dietary selenium intake found was 26.3 (±8.3) ·g/day for children from the city of São Paulo, 37.4 (±16.0) ·g/day for children from Belém, 107 (±107) ·g/day for children from Macapá, 28.4 (±7.5) ·g/day for institutionalized elderly, 32 (±6) ·g/day for non-institutionalized elderly and 37 (±17) ·g/day for university students from São Paulo. Most daily dietary selenium intake range observed were below the EAR values. The values obtained for children groups from Belém and Macapá cities, whose intake levels were much higher than the recommendation, were an exception. 相似文献
2.
I. Sziklai-László D. Majchrzak I. Elmadfa M. á. Cser 《Journal of Radioanalytical and Nuclear Chemistry》2009,279(2):585-590
The metabolic roles of vitamin E and selenium are closely related, and to a very great extent, each can compensate for the
deficiency of the other. The aim of the study was to determine and compare the Se and vitamin E (α- and γ-tocopherol) contents
of breast milk and commercially available infant formulas in Hungary. The Se content was measured by instrumental neutron
activation analysis (INAA), while the α-, and γ-tocopherol concentrations were determined by high performance liquid chromatography
(HPLC). The mean Se concentration was 17.4±2.8 μg/L in transitional and 13.8±2.3 μg/L in mature milk. It was found that, all
of the starter (ST), the follow-on (FO) and the specialized formulas (SF) had lower Se content than breast milk. Transitional
breast milk resulted in a higher Se intake (14 μg/day) than mature milk (11 μg/day). The daily Se intakes in Hungarian infants
were within the Recommended Dietary Allowance (RDA) range. The natural vitamin E contents of human milk were similar during
the early and late lactation. Mature breast milk had 3.30±1.13 mg/L α-TE concentration and this was significantly higher than
that of in ST (1.98±1.57), and FO (1.77±0.78), or in SF ready to feed preparations (1.03±0.74). The present study suggests
that the formulas for the optimal development of young infants, should contain concentrations of these antioxidants on a level
which is comparable to that of the human milk. 相似文献
3.
Appraisal of venomous metals in selected crops and vegetables from industrial areas of the Punjab Province 总被引:1,自引:0,他引:1
Due to the inadequate water sources, usually sewerage water and industrial effluents are being use for irrigation of the agricultural
land around the industrial areas in Pakistan wherein crops and vegetables are cultivated. As untreated effluents contain heavy
elements, toxic metals and organic pollutants that may find its way through food chain to general public and may cause health
hazards. It is, therefore, mandatory to assess the toxic metals in such crops and vegetables. In this regard, samples of corn,
millet, cabbage, spinach and potato were collected within the vicinity of industrial areas of the Faisalabad and Gujranwala
regions. The food samples were analyzed using neutron activation analysis (NAA) technique. The highest concentration values
of Arsenic (1.9 ± 0.1 μg/g) and Cobalt (0.85 ± 0.01 μg/g) were found in cabbage whereas Manganese (91.6 ± 0.2 μg/g), Antimony
(0.15 ± 0.03 μg/g) and Selenium (1.1 ± 0.1 μg/g) were observed in spinach and Chromium (9.63 ± 1.3 μg/g) was found in millet
crop. The observed concentrations of all the toxic and heavy metals in crops and vegetables are higher than those reported
in the literature. 相似文献
4.
Biological materials containing trace amounts of mercury and selenium were examined using neutron activation analysis. They
were analyzed using Compton suppression and γ–γ coincidence counting. The 279 keV photopeak of activated mercury (203Hg) was analyzed in order to observe the mercury content in these samples. Selenium, an element found in many biological samples,
interferes with the analysis of 203Hg when activated (75Se). Because the selenium interference comes from a cascading emission, Compton suppression was utilized to reduce this interference.
In order to fully characterize the selenium content in the samples, γ–γ coincidence was used which reduced the background
and eliminated bremsstrahlung interference produced from neutron activated phosphorous through the 31P(n, γ)32P reaction which is a pure beta emitter. As a result, we determined the mercury and selenium concentrations in three standard
reference materials, which contain varying ratios of mercury to selenium concentrations. This study also showed that these
types of concentrations can be determined from small (<500 mg) sample masses. Further work needs to be done on wet samples
that require dehydration, as mercury can be lost through this process. 相似文献
5.
Selenomethionine content of candidate reference materials 总被引:1,自引:0,他引:1
Selenium has been identified as an antioxidant of importance in the diet. Accurate determination of its chemical forms depends
on the availability of suitable reference materials (RMs). Two candidate reference materials for determination of selenomethionine
(Semet) in food-related materials, a standard wheat gluten sample (NIST RM 8418 Wheat Gluten) and a commercial selenium enriched
yeast, have been examined by use of a gas chromatography–isotope dilution mass spectrometry (IDMS) procedure, after treatment
of the matrix with 0.1 mol L–1 hydrochloric acid containing stannous chloride, addition of CNBr, and extraction with chloroform. This procedure results
in cleavage of the CH3Se group to form volatile CH3SeCN. Addition of isotopically enriched 74Semet to an analytical sample enables estimation of the naturally occurring protein-bound 80Semet by IDMS without a protein-digestion process.
We found that the Wheat Gluten RM contains a significant amount of Semet as a portion of its assigned value of 2.58 μg Setotal g–1. Commercial selenium yeast tablets are labeled as containing an elevated level of “organic selenium”, usually as Semet. The
sample we investigated contained 210 μg Setotal g–1 sample as determined separately by IDMS, measuring elemental selenium after digestion. 73% of this total (153±21 μg SeSemet g–1; n = 23) was present as Semet. Thus, these two materials contain significant amounts of their total selenium content as Semet
and would be good candidates for further study and characterization as reference materials for determining this important
food component.
The CNBr reaction used will also enable the determination of Se-(methyl)selenocysteine, the biological role of which is of
recent interest. In addition to matrix RMs for Semet, it is important to have standard materials of the pure substance. We
have examined a sample of a candidate standard material of selenomethionine being prepared by the USP. It was confirmed that
this material is pure selenomethionine.
Received: 13 December 2000 / Revised: 5 March 2001 / Accepted: 12 March 2001 相似文献
6.
K. Shiraishi Y. Muramatsu I. P. Los V. N. Korzun N. Y. Tsigankov P. V. Zamostyan 《Journal of Radioanalytical and Nuclear Chemistry》1999,242(1):199-202
Total diet samples for Ukrainians and Japanese were collected by duplicate portion studies in relation to the Chernobyl accident.
Stable iodine and bromine in the diet samples were determined by using ICP-MS after chemical separation. Daily intakes of
iodine for Ukrainians and Japanese were found to be 110±104 and 1770±1610 μg per person per day, respectively. Daily intakes
of Br were as follows: Ukrainians 3.47±2.12 mg; Japanese 11.4±2.4 mg. Daily iodine intake in Ukrainians was lower than the
recommended dietary allowance (150 μg) and showed the relationship of high prevalence of goiter in this area. 相似文献
7.
J. Steven Morris Vickie L. Spate Ruth Ann Ngwenyama David J. Waters 《Journal of Radioanalytical and Nuclear Chemistry》2012,291(2):439-444
Toenails and fingernails are routinely used to estimate selenium status in epidemiological studies; however, literature validating
nail selenium concentration as a surrogate for critical organs is limited. In this study diets of intact male dogs were selenium
supplemented at two physiological levels (3 and 6 μg/kg/day) in two different forms, selenomethionine and selenium-enriched
bioformed yeast. The selenium-adequate basal diet consumed by the treatment and control groups during the 4-week run-in period
and throughout the trial contained 0.3 ppm selenium. After 7 months the dogs in the two treatment groups and the control group
were euthanized. Representative tissue samples from prostate, brain, liver, heart and skeletal muscle were collected, rinsed
and frozen. Toenail clippings from multiple toes were also collected. Selenium was determined by neutron activation analysis
using Se77m (half life = 17.4 s) at the University of Missouri Research Reactor Center. NIST SRM 1577, Bovine Liver was analyzed
as a quality control. The analysts were blinded to control and treatment group assignments. As expected, tissue selenium levels
increased proportionally with supplementation. A slightly greater increase in tissue selenium was observed for the purified
selenomethionine compared to the bioformed yeast; however this trend was significant only for brain tissue. Toenail selenium
concentrations and tissue selenium were highly correlated (p < 0.003) with Pearson coefficients of 0.759 (skeletal muscle), 0.745 (heart), 0.729 (brain), 0.723 (prostate), and 0.632
(liver). The toenail biologic monitor accurately assesses selenium status in skeletal muscle, heart, brain, prostate, and
liver in the canine model. 相似文献
8.
Minakata K Nozawa H Gonmori K Yamagishi I Suzuki M Hasegawa K Watanabe K Suzuki O 《Analytical and bioanalytical chemistry》2011,400(7):1945-1951
An electrospray ionization tandem mass spectrometric (ESI-MS-MS) method has been developed for the determination of cyanide
(CN–) in blood. Five microliters of blood was hemolyzed with 50 μL of water, then 5 μL of 1 M tetramethylammonium hydroxide solution
was added to raise the pH of the hemolysate and to liberate CN– from methemoglobin. CN– was then reacted with NaAuCl4 to produce dicyanogold, Au(CN)2–, that was extracted with 75 μL of methyl isobutyl ketone. Ten microliters of the extract was injected directly into an ESI-MS-MS
instrument and quantification of CN– was performed by selected reaction monitoring of the product ion CN– at m/z 26, derived from the precursor ion Au(CN)2– at m/z 249. CN– could be measured in the quantification range of 2.60 to 260 μg/L with the limit of detection at 0.56 μg/L in blood. This
method was applied to the analysis of clinical samples and the concentrations of CN– in the blood were as follows: 7.13 ± 2.41 μg/L for six healthy non-smokers, 3.08 ± 1.12 μg/L for six CO gas victims, 730 ± 867 μg
for 21 house fire victims, and 3,030 ± 97 μg/L for a victim who ingested NaCN. The increase of CN– in the blood of a victim who ingested NaN3 was confirmed using MS-MS for the first time, and the concentrations of CN– in the blood, gastric content and urine were 78.5 ± 5.5, 11.8 ± 0.5, and 11.4 ± 0.8 μg/L, respectively. 相似文献
9.
C. K. Baskett V. L. Spate J. S. Morris H. D. Anderson M. M. Mason C. L. Reams T. P. Cheng K. R. Zinn G. M. Hill R. P. Dowdy 《Journal of Radioanalytical and Nuclear Chemistry》1995,195(1):97-108
The principal objective of this study was to determine if the use of a stable enriched tracer of Se-76 could be used to determine the delay time between a dietary intake of selenium and its appearance in fingernails and toenails. Selenium is an essential trace element in human nutrition. It has been studied at the Missouri University Research Reactor (MURR) for the past 15 years using an Instrumental Neutron Activation Analysis (INAA) technique. The principal route of human exposure to selenium is through the diet. Selenium concentrations of nails, blood, hair, and urine have been used as indicators of dietary selenium intake. In this study, a cohort consisting of seven men and five women ingested three selenium supplements of 150 g each over a three day period. The selenium was enriched in Se-76 (96.48%) and ingested as selenite in orange juice following an overnight fast. Fingernails and toenails were collected prior to the selenium supplementation and for several months afterward to be used as biochemical indicators. The peak76Se concentration in the fingernails and toenails occurred at 19–23 and 16–32 weeks after supplementation, respectively. 相似文献
10.
Joana P. N. Ribeiro Luís M. Magalhães Marcela A. Segundo Salette Reis José L. F. C. Lima 《Analytical and bioanalytical chemistry》2010,397(7):3005-3014
In the present work, a fluorimetric automatic method based on multisyringe flow injection analysis (MSFIA) was developed for
in vitro evaluation of scavenging capacity against nitric oxide (NO) using 4,5-diaminofluorescein (DAF-2) as an NO-selective
fluorogenic probe. The MSFIA manifold was assembled to perform the in-line generation of NO and the competitive reaction of
putative scavenger molecules and DAF-2 with NO at conditions close to those found in vivo regarding temperature (37°C), pH
(7.4), and concentration of NO (less than 1 μM). This approach allowed the evaluation of scavenging capacity against NO by
endogenous antioxidant molecules, pharmaceutical compounds, and human plasma. IC50 values were calculated for rutin (1.30 ± 0.02 μM, positive control), cysteine (321 ± 8 μM), reduced glutathione (1106 ± 93 μM),
uric acid (134 ± 12 μM), dipyrone (1.36 ± 0.06 μM), and captopril (363 ± 28 μM). A high degree of automation was attained
as the successive dilution of antioxidant standard solutions required for IC50 assessment was performed automatically, in a dilution chamber placed in the flow system. A determination throughput of 16 h-1 and a good precision were attained (relative standard deviation between 1.6 and 9.0%), fostering the application of the proposed
method to routine/screening analysis of scavenging capacity against NO. 相似文献
11.
M. López-Sánchez M. J. Ayora-Cañada A. Molina-Díaz M. Siam W. Huber G. Quintás S. Armenta B. Lendl 《Analytical and bioanalytical chemistry》2009,394(8):2137-2144
A mid-infrared enzymatic assay for label-free monitoring of the enzymatic reaction of fructose-1,6-bisphosphatase with fructose
1,6-bisphosphate has been proposed. The whole procedure was done in an automated way operating in the stopped flow mode by
incorporating a temperature-controlled flow cell in a sequential injection manifold. Fourier transform infrared difference
spectra were evaluated for kinetic parameters, like the Michaelis–Menten constant (K
M) of the enzyme and V
max of the reaction. The obtained K
M of the reaction was 14 ± 3 g L−1 (41 μM). Furthermore, inhibition by adenosine 5′-monophosphate (AMP) was evaluated, and the K
MApp value was determined to be 12 ± 2 g L−1 (35 μM) for 7.5 and 15 μM AMP, respectively, with V
max decreasing from 0.1 ± 0.03 to 0.05 ± 0.01 g L−1 min−1. Therefore, AMP exerted a non-competitive inhibition. 相似文献
12.
M. Tufail Sabiha-Javied N. Akhtar J. Akhter 《Journal of Radioanalytical and Nuclear Chemistry》2010,283(3):585-590
Wheat is staple food of the people of Pakistan. Phosphate fertilizers, used to increase the yield of wheat, enhance the natural
radioactivity in the agricultural fields from where radionuclides are transferred to wheat grain. A study was, therefore,
carried out to investigate the uptake of radioactivity by wheat grain and to determine radiation doses received by human beings
from the intake of foodstuffs made of wheat grain. Wheat was grown in a highly fertilized agricultural research farm at the
Nuclear Institute of Agriculture and Biology (NIAB), Faisalabad, Pakistan. The activity concentration of 40K, 226Ra and 232Th was measured in soil, single superphosphate (SSP) fertilizer, and wheat grain using an HPGe-based gamma-ray spectrometer.
Soil to wheat grain transfer factors determined for 40K, 226Ra and 232Th were 0.118 ± 0.021, 0.022 ± 0.004 and 0.036 ± 0.007, respectively, and the annual effective dose received by an adult person
from the intake of wheat products was estimated to be 217 μSv. 相似文献
13.
D. Leyva J. Estévez A. Montero I. Pupo 《Journal of Radioanalytical and Nuclear Chemistry》2012,291(3):699-705
A sensitive and non chromatographic analytical procedure for the separation of inorganic selenium species in natural water
has been performed. A combination of APDC coprecipitation and determination by an absolute thin layer Energy dispersive X-ray
fluorescence spectrometry method was used. The influence of various analytical parameters such as element concentration, oxidation
states and pH on the recoveries of Se (IV) was examined. The presence of organic matter and bicarbonate anions, typical components
in Cuban groundwater samples, was also tested. Negligible matrix effects were observed. At pH 4 a 100% recovery was found
for Se (IV). The coprecipitation recovery of the oxidized selenium species (Se (VI)) was null for the selected concentration
range (5–100 μg L−1). When the Se (VI) was reduced by heating the solution with 4 mol L−1 HCl, quantitative recovery was also obtained. The determination of total selenium was conducted by the application of the
oxidation–reduction process and the analytical procedure for Se (IV). Se (VI) content was calculated as the difference between
total selenium and Se (IV). The detection limit was 0.13 μg L−1. The relative standard deviation was lower than 3.5% for 5 μg L−1 of Se (IV). The trueness of the method was verified by using standardized hydride generation-atomic absorption spectrometry
technique. The results obtained using the EDXRF technique were in good agreement with the ones determined by HG-AAS. The proposed
method was applied to the determination of Se (IV) in surface water and groundwater samples. 相似文献
14.
N. T. Silva N. F. Nascimento L. S. Cividanes C. A. Bertran G. P. Thim 《Journal of Sol-Gel Science and Technology》2008,47(2):140-147
Diphasic cordierite gels were prepared from colloidal silica, aluminum and magnesium nitrates and citric acid. The mechanism
of xerogel decomposition was studied by infrared spectroscopy (FT-IR) and thermal gravimetric analysis (TGA). The thermal
decomposition of the xerogel forms a solid mixture of MgO, Al2O3 and SiO2 at around 250 °C. Cordierite crystallization was studied by X-ray diffraction (XRD) and differential thermal analysis (DTA).
Xerogels were initially thermally treated, and this sample crystallized to μ-cordierite at 850 °C, at 900 °C α-cordierite
crystallizes and at 1150 °C α-cordierite is the major phase and μ-cordierite is totally consumed. The apparent activation
energy for cordierite crystallization process was determined based on the Johnson-Mehl-Avrami-Kolmogorov (JMAK) theory, Ligero
methods and the Arrhenius law for dependence of activation energy with temperature. The apparent activation energy was (466.8 ± 34.3) kJ/mol,
the exponent of Avrami was (1.9 ± 0.2) and the frequency factor was (1.55 × 1020) s−1. The Avrami value indicates a nucleation controlled process, which can be a consequence of the high xerogel homogeneity,
a consequence of the early and simultaneous formation of the MgO, Al2O3 and SiO2 mixture. 相似文献
15.
Camp CL Sharp BL Reid HJ Entwisle J Goenaga-Infante H 《Analytical and bioanalytical chemistry》2012,402(1):367-372
The determination of total deoxyribonucleic acid (DNA) concentration is of great importance in many biological and bio-medical
analyses. The quantification of DNA is traditionally performed by UV spectroscopy; however the results can be affected greatly
by the sample matrix. The proposed method quantifies phosphorus in digested calf thymus DNA and human DNA by high performance
liquid chromatography (HPLC) combined with inductively coupled plasma mass spectrometry (ICP-MS). The method presented showed
excellent baseline separation between all four DNA mono-nucleotides and 5′UMP. The ability of LC-ICP-MS to provide an internal
check that only DNA derived phosphorus was counted in the assay was demonstrated by establishing a mass balance between the
total phosphorous signal from undigested DNA and that from the speciated DNA. Column recoveries ranging from 95% to 99% for
phosphorus resulted in a mass balance of 95% ± 0.5% for standard nucleotides, determined by LC-ICP-MS, compared to total DNA
determined by flow injection coupled to ICP-MS (FI-ICP-MS). The method for quantification was validated by analysis of NIST
SRM 2,372; a total speciated DNA recovery of 52.1 ng/μL, compared with an expected value of 53.6 ng/μL, was determined by
external calibration. From repeat measurements, a mass balance of 97% ± 0.5% for NIST DNA was achieved. The method limits
of detection for individual nucleotides were determined between 0.8 and 1.7 μg L−1 (31P) for individual nucleotides by LC-ICP-MS, and 360 ng L−1 for 5′AMP by direct nebulisation. 相似文献
16.
Herranz S Ramón-Azcón J Benito-Peña E Marazuela MD Marco MP Moreno-Bondi MC 《Analytical and bioanalytical chemistry》2008,391(5):1801-1812
Specific polyclonal antibodies against s-triazine herbicides were obtained by preparing immunogens coupling home-synthesized haptens derivatives of simazine (6-chloro-N-ethyl-N′-ethyl-1,3,5-triazine-2,4-diamine) to lysine groups of hemocyanin from keyhole limpets and bovine serum albumin carrier proteins.
Three highly sensitive rabbit antisera were obtained and evaluated with a battery of six enzyme tracers derived from triazine
structures in an optimized ELISA format. The antiserum As8 and the HRP-2f tracer, which yield the best assay sensitivity for
simazine (detection limit 0.11 ± 0.02 μg L−1, IC50 0.88 ± 0.04 μg L−1), were applied to the development of a sensitive flow-through immunoassay for the analysis of this herbicide. The automated
assay was based on a direct competitive immunosorbent assay and fluorescence detection. The optimized method presents an IC50 value of 0.35 ± 0.04 μg L−1 with a detection limit of 1.3 ± 0.9 ng L−1 and a dynamic range from 0.010 to 7.5 μg L−1 simazine. The generic nature of the antiserum was shown by good relative cross-reactivities with other triazines such as
atrazine (420%) or propazine (130%) and a lower response to terbutylazine (6.4%) and desethyl-atrazine (2.2%). No cross-reactivity
was obtained for nonrelated pesticides such as 2,4-dichlorophenoxyacetic acid or linuron and the assay could be applied as
a screening method for triazine herbicides. The total analysis time was 30 min per determination and the immunosensor could
be reused for more than 150 cycles without significant loss of activity. The immunosensor has been successfully applied to
the direct analysis of simazine in surface water samples at the nanogram per liter level. The results obtained by comparative
analysis of the immunosensor with a chromatographic procedure for triazines showed a close correspondence. 相似文献
17.
Fábio A. Silva Cilene C. F. Padilha Gustavo Rocha de Castro Paulo dos Santos Roldan Ana R. de Araujo Nogueira Paula M. Moraes Pedro M. Padilha 《Central European Journal of Chemistry》2011,9(1):119-125
This paper proposes a method to determine selenium in samples of fish muscle and liver tissue using ultrasound assisted extraction
process, and analysed by graphite furnace atomic absorption spectrometry (GFAAS). The selenium content was extracted by 0.10
M HCl at the optimal extraction conditions which were established as follows: sample mass of 100 mg; granulometry of the sample
<60 μm; sonication time of five 40 s cycles; and sonication power of 136 W. The selenium determinations were performed by
GFAAS, at a drying temperature of 120°C/250°C, pyrolysis temperature of 1300°C, atomization temperature of 2300°C, and cleaning
temperature of 2800°C. Palladium nitrate was used as a chemical modifier coinjected with the samples, and tungsten as a permanent
modifier. The concentration of selenium determined in the pool of fish muscle and liver tissue were 280.4±4.2 e 592.3±6.7
μg kg−1, respectively. The accuracy and precision of the proposed extraction method were evaluated using certified standard Bovine
Muscle — NIST 8414. The results obtained by the ultrasonic extraction method were equivalent to those obtained by the method
of acid mineralization of samples in a microwave oven 相似文献
18.
An analytical method for the speciation of selenomethionine, selenocystine, selenite and selenate by high performance liquid
chromatography (HPLC) with atomic spectrometric detection is presented. An organic polymeric strong anion exchange column
was used as the stationary phase in combination with an aqueous solution of 6 mmol L–1 of salicylate ion at pH 8.5 as the mobile phase which allowed the isocratic separation of the four selenium analytes within
8 minutes. The separated selenium species were detected on-line by flame atomic absorption spectrometry (FAAS) or inductively
coupled plasma mass spectrometry (ICP-MS). The signal-to-noise ratio of the FAAS detector was optimized using a hydrogen-argon
entrained-air flame and a slotted-tube atom trap (STAT) in the flame. The limit of detection (3 σ) achieved by the HPLC-FAAS
system was 1 mg L–1 of selenium (100 μL injections) for each of the four selenium species. More powerful selenium detection was achieved using
an ELAN 5000 ICP-MS instrument. Selenium was measured at m/z = 82. The ICP-MS signal intensity was enhanced by a factor of
3–4 after addition of 3% methanol to the chromatographic mobile phase and by using an increased plasma power input of 1300
W. The limit of detection achieved under these conditions was 1 μg L–1 (100 μL injections). The HPLC-ICP-MS system was used for selenium speciation of selenite and selenate in aqueous solutions
during a BCR certification exercise and for selenium speciation in the certified reference material, BCR No. 402 White Clover.
Extraction experiments revealed that the selenium species in the biological material were extractable only in the presence
of water in the extraction medium. The results indicated that selenate and a compound of unknown identity U were present in
the plant sample.
Received: 4 September 1996 / Accepted: 12 December 1996 相似文献
19.
Summary An ion-chromatographic procedure is described for the determination of selenium (VI) at μg L−1 level in the presence of anions and heavy metal ions. Maximum permissible concentrations and effects from each interfering
substance were investigated for the Se concentration range 12.5–1,000 μg L−1. The method, optimized for the detection of SeO
4
2−
, gives results suitable for speciation analysis. Total selenium can be determined after complete conversion to selenate ion
by oxidation with KMnO4. The detection limit of selenium is 4.8 μg L−1 (0.96 ng for 200 μL sample).
Paper presented at the 41st Pittsburgh Conference, New York, March 5–9, 1990. 相似文献
20.
John K. Osiri Hamed Shadpour Steven A. Soper 《Analytical and bioanalytical chemistry》2010,398(1):489-498
A poly(methyl methacrylate) microfluidic chip was used to perform a two-dimensional (2-D) separation of a complex protein
mixture in short development times. The separation was performed by combining sodium dodecyl sulfate micro-capillary gel electrophoresis
(SDS μ-CGE) with microemulsion electrokinetic chromatography (μ-MEEKC), which were used for the first and second dimensions,
respectively. Fluorescently labeled Escherichia coli cytosolic proteins were profiled by this 2-D approach with the results compared to a similar 2-D separation using SDS μ-CGE × μ-MEKC
(micelle electrokinetic chromatography). The relatively short column lengths (effective length = 10 mm) for both dimensions
were used to achieve separations requiring only 220 s of development time. High spot production rates (131 ± 11 spots min−1) and reasonable peak capacities (481 ± 18) were generated despite the fact that short columns were used. In addition, the
use of μ-MEEKC in the second dimension was found to produce higher peak capacities compared to μ-MEKC (481 ± 18 for μ-MEEKC
and 332 ± 17 for μ-MEKC) due to the higher plate numbers associated with μ-MEEKC. 相似文献