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1.
An on-line Hg reduction technique using stannous chloride as the reductant was applied for accurate and precise mercury isotope ratio determinations by multi-collector (MC)-ICP/MS. Special attention has been paid to ensure optimal conditions (such as acquisition time and mercury concentration) allowing precision measurements good enough to be able to significantly detect the anticipated small differences in Hg isotope ratios in nature. Typically, internal precision was better than 0.002% (1 RSE) on all Hg ratios investigated as long as approximately 20 ng of Hg was measured with a 10-min acquisition time. Introducing higher amounts of mercury (50 ng Hg) improved the internal precision to <0.001%. Instrumental mass bias was corrected using 205Tl/203Tl correction coupled to a standard-sample bracketing approach. The large number of data acquired allowed us to validate the consistency of our measurements over a one-year period. On average, the short-term uncertainty determined by repeated runs of NIST SRM 1641d Hg standard during a single day was <0.006% (1 RSD) for all isotope pairs investigated (202Hg/198Hg, 202Hg/199Hg, 202Hg/200Hg, and 202Hg/201Hg). The precision fell to <0.01% if the long-term reproducibility, taken over 11 months (over 100 measurements), was considered. The extent of fractionation has been investigated in a series of sediments subject to various Hg sources from different locations worldwide. The ratio 202Hg/198Hg expressed as δ values (per mil deviations relative to NIST SRM 1641d Hg standard solution) displayed differences from +0.74 to −4.00‰. The magnitude of the Hg fractionation per amu was constant within one type of sample and did not exceed 1.00‰. Considering all results (the reproducibility of Hg standard solutions, reference sediment samples, and the examination of natural samples), the analytical error of our δ values for the overall method was within ±0.28‰ (1 SD), which was an order of magnitude lower than the extent of fractionation (4.74‰) observed in sediments. This study confirmed that analytical techniques have reached a level of long-term precision and accuracy that is sufficiently sensitive to detect even small differences in Hg isotope ratios that occur within one type of samples (e.g., between different sediments) and so far have unequivocally shown that Hg isotope ratios in sediments vary within approximately 5‰. 相似文献
2.
MeHg and inorganic Hg compounds were measured in aqueous media for isotope ratio analysis using aqueous phase derivatization,
followed by purge-and-trap preconcentration. Compound-specific isotope ratio measurements were performed by gas chromatography
interfaced to MC-ICP/MS. Several methods of calculating isotope ratios were evaluated for their precision and accuracy and
compared with conventional continuous flow cold vapor measurements. An apparent fractionation of Hg isotopes was observed
during the GC elution process for all isotope pairs, which necessitated integration of signals prior to the isotope ratio
calculation. A newly developed average peak ratio method yielded the most accurate isotope ratio in relation to values obtained
by a continuous flow technique and the best reproducibility. Compound-specific isotope ratios obtained after GC separation
were statistically not different from ratios measured by continuous flow cold vapor measurements. Typical external uncertainties
were 0.16‰ RSD (n = 8) for the 202Hg/198Hg ratio of MeHg and 0.18‰ RSD for the same ratio in inorganic Hg using the optimized operating conditions. Using a newly
developed reference standard addition method, the isotopic composition of inorganic Hg and MeHg synthesized from this inorganic
Hg was measured in the same run, obtaining a value of δ
202Hg = −1.49 ± 0.47 (2SD; n = 10). For optimum performance a minimum mass of 2 ng per Hg species should be introduced onto the column. 相似文献
3.
Microwave digestion and isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-SFMS) has been applied to the
determination of Pb in rice flour. In order to achieve highly precise determination of low concentrations of Pb, the digestion
blank for Pb was reduced to 0.21 ng g−1 after optimization of the digestion conditions, in which 20 mL analysis solution was obtained after digestion of 0.5 g rice
flour. The observed value of Pb in a non-fat milk powder certified reference material (CRM), NIST SRM 1549, was 16.8 ± 0.8 ng
g−1 (mean ± expanded uncertainty, k = 2; n = 5), which agreed with the certified value of 19 ± 3 ng g−1 and indicated the effectiveness of the method. Analytical results for Pb in three brown rice flour CRMs, NIST SRM 1568a,
NIES CRM 10-a, and NIES CRM 10-b, were 7.32 ± 0.24 ng g−1 (n = 5), 1010 ± 10 ng g−1 (n = 5), and 1250 ± 20 ng g−1 (n = 5), respectively. The concentration of Pb in a candidate white rice flour reference material (RM) sample prepared by the
National Metrology Institute of Japan (NMIJ) was observed to be 4.36 ± 0.28 ng g−1 (n = 10 bottles).
Figure Digestion blank of Pb was carefully reduced to approximately 0.2 ng g-1 which permitted the highly precise determination of Pb at low ng g-1 level in foodstuff samples by ID-SFMS 相似文献
4.
Hg stable isotope analysis by the double-spike method 总被引:2,自引:0,他引:2
Recent publications suggest great potential for analysis of Hg stable isotope abundances to elucidate sources and/or chemical
processes that control the environmental impact of mercury. We have developed a new MC-ICP-MS method for analysis of mercury
isotope ratios using the double-spike approach, in which a solution containing enriched 196Hg and 204Hg is mixed with samples and provides a means to correct for instrumental mass bias and most isotopic fractionation that may
occur during sample preparation and introduction into the instrument. Large amounts of isotopic fractionation induced by sample
preparation and introduction into the instrument (e.g., by batch reactors) are corrected for. This may greatly enhance various
Hg pre-concentration methods by correcting for minor fractionation that may occur during preparation and removing the need
to demonstrate 100% recovery. Current precision, when ratios are normalized to the daily average, is 0.06‰, 0.06‰, 0.05‰,
and 0.05‰ (2σ) for 202Hg/198Hg, 201Hg/198Hg, 200Hg/198Hg, and 199Hg/198Hg, respectively. This is slightly better than previously published methods. Additionally, this precision was attained despite
the presence of large amounts of other Hg isotopes (e.g., 5.0% atom percent 198Hg) in the spike solution; substantially better precision could be achieved if purer 196Hg were used. 相似文献
5.
Lyudmila A. Belyakova Oleksandra M. Shvets Diana Yu. Lyashenko 《Central European Journal of Chemistry》2008,6(4):581-591
The present work investigates the adsorptive interactions of Hg(II) ions in aqueous medium with hydroxylated silica, aminopropylsilica
and silica chemically modified by β-cyclodextrin. Batch adsorption studies were carried out with various agitation times and
mercury(II) concentrations. The maximum adsorption was observed within 15–30 min of agitation. The kinetics of the interactions,
tested with the model of Lagergren for pseudo-first and pseudo-second order equations, showed better agreement with first
order kinetics (k1 = 3.4 ± 0.2 to 5.9 ± 0.3 min−1). The adsorption data gave good fits with Langmuir isotherms. The results have shown that β-cyclodextrin-containing adsorbent
has the largest adsorption specificity to Hg(II): K
L
= 4125 ± 205 mmol−1. “β-cyclodextrin-NO3-” inclusion complexes with ratio 1: 1 and super molecules with composition C42H70O35 ⊎ 3 Hg(NO3)2 are formed on the surface of β-cyclodextrin-containing silica.
相似文献
6.
Radix Scrophulariae (Xuanshen) is one of the famous Chinese herbal medicines widely used to treat rheumatism, tussis, pharyngalgia, arthritis,
constipation, and conjunctival congestion. Harpagoside and cinnamic acid are the main bioactive components of Xuanshen. The
purpose of this study was to develop an HPLC–UV method for simultaneous determination of harpagoside and cinnamic acid in
rat plasma and investigate pharmacokinetic parameters of harpagoside and cinnamic acid after oral administration of Xuanshen
extract (760 mg kg−1). After addition of syringin as internal standard, the analytes were isolated from plasma by liquid–liquid extraction. Separation
was achieved on a Kromasil C18 column, and detection was by UV absorption at 272 nm. The described assay was validated in terms of linearity, accuracy,
precision, recovery, and limit of quantification according to the FDA validation guidelines. Calibration curves for both analytes
were linear with the coefficient of variation (r) for both was greater than 0.999. Accuracy for harpagoside and cinnamic acid ranged from 100.7–103.5% and 96.9–102.9%, respectively,
and precision for both analytes were less than 8.5%. The main pharmacokinetic parameters found for harpagoside and cinnamic
acid after oral infusion of Xuanshen extract were as follows: C
max 1488.7 ± 205.9 and 556.8 ± 94.2 ng mL−1, T
max 2.09 ± 0.31 and (1.48 ± 0.14 h, AUC0–24 10336.4 ± 1426.8 and 3653.1 ± 456.4 ng h mL−1, 11276.8 ± 1321.4 and 3704.5 ± 398.8 ng h mL−1, and t
1/2 4.9 ± 1.3 and 2.5 ± 0.9 h, respectively. These results indicated that the proposed method is simple, selective, and feasible
for pharmacokinetic study of Radix Scrophulariae extract in rats.
Figure Radix Scrophulariae 相似文献
7.
Costa D Fernandes E Santos JL Pinto DC Silva AM Lima JL 《Analytical and bioanalytical chemistry》2007,387(6):2071-2081
In the present study, a new fluorescence microplate screening assay for evaluating scavenging activity against singlet oxygen
(1O2) was implemented. The chemical generation of 1O2 was promoted using the thermodissociable endoperoxide of disodium 3,3′-(1,4-naphthalene)bispropionate (NDPO2). The detection of 1O2 was achieved using dihydrorhodamine 123 (DHR), a nonfluorescent molecule that is oxidizable to the fluorescent form rhodamine
123 (RH). The combined use of a 1O2-selective generator and a highly sensitive probe (DHR) was then successfully applied to perform a screening assay of the
1O2 scavenging activities of ascorbic acid, penicillamine, cysteine, N-acetylcysteine (NAC), methionine, reduced glutathione (GSH), dihydrolipoic acid, lipoic acid, and sodium azide. All of these
antioxidants exhibited concentration-dependent 1O2 scavenging capacities. They could be ranked according to observed activity: ascorbic acid> cysteine> penicillamine> dihydrolipoic
acid > GSH> NAC> sodium azide> lipoic acid (IC50 values of 3.0 ± 0.2, 8.0 ± 0.7, 10.9 ± 0.8, 25.2 ± 4.5, 57.4 ± 5.9, 138 ± 13, 1124 ± 128, 2775 ± 359 μM, mean±SEM, respectively)
> methionine (35% of scavenging effect at 10 mM). In conclusion, the use of NDPO2 as a selective generator for 1O2 and its fluorescence detection by the highly sensitive probe DHR is shown to be a reliable and resourceful analytical alternative
means to implement a microplate screening assay for scavenging activity against 1O2.
Generation and detection of singlet oxygen 相似文献
8.
Cho SK Shim SH Park KR Choi SH Lee S 《Analytical and bioanalytical chemistry》2006,386(7-8):2027-2033
Three hundred and thirty two bacterial colonies were isolated from soil contaminated by an oil spill. All the bacteria were
cultured in a liquid medium individually, and the surface tensions of the media were compared. The bacterium whose culture
medium had the lowest surface tension was identified as Pseudomonas sp. G11. A biosurfactant was produced by cultivation of the Pseudomonas sp. G11 in the LB media. For extraction of the biosurfactant, two solvent systems were used (n-hexane and a 2:1 (v/v) mixture of chloroform/MeOH), and the results were compared. Various experimental conditions (solvent
composition, flow rate, etc.) were tested to optimize the analysis of the biosurfactant by asymmetrical flow field-flow fractionation
(AsFlFFF). The biosurfactant was successfully separated from the culture medium by AsFlFFF when pure water was used as the
carrier. From the retention data, the hydrodynamic diameter (d
H) and molecular weight (M) of the biosurfactant were determined by AsFlFFF. The molecular weight was determined by using pullulans as the calibration
standards. The d
H and M were 49 nm and 2.3 × 105 Da when extracted with n-hexane, and 39 nm and 1.13 × 105 Da when extracted with the 2:1 mixture of chloroform/MeOH, respectively.
Figure Separation of biosurfactant from its culture medium by flow FFF 相似文献
9.
The redox characteristics of the drug domperidone at a glassy-carbon electrode (GCE) in aqueous media were critically investigated
by differential-pulse voltammetry (DPV) and cyclic voltammetry (CV). In Britton–Robinson (BR) buffer of pH 2.6–10.3, an irreversible
and diffusion-controlled oxidation wave was developed. The dependence of the CV response of the developed anodic peak on the
sweep rate (ν) and on depolizer concentration was typical of an electrode-coupled chemical reaction mechanism (EC) in which an irreversible
first-order reaction is interposed between the charges. The values of the electron-transfer coefficient (α) involved in the rate-determining step calculated from the linear plots of E
p,a against ln (ν) in the pH range investigated were in the range 0.64 ± 0.05 confirming the irreversible nature of the oxidation peak. In
BR buffer of pH 7.6–8.4, a well defined oxidation wave was developed and the plot of peak current height of the DPV against
domperidone concentration at this peak potential was linear in the range 5.20 × 10−6 to 2.40 × 10−5 mol L−1 with lower limits of detection (LOD) and quantitation (LOQ) of 6.1 × 10−7 and 9.1 × 10−7 mol L−1, respectively. A relative standard deviation of 2.39% (n = 5) was obtained for 8.5 × 10−6 mol L−1 of the drug. These DPV procedures were successfully used for analysis of domperidone in the pure form (98.2 ± 3.1%), dosage
form (98.35 ± 2.9%), and in tap (97.0 ± 3.6%) and wastewater (95.0 ± 2.9%) samples. The method was validated by comparison
with standard titrimetric and HPLC methods. Acceptable error of less than 3.3 % was also achieved.
Figure In aqueous media at pH 7.6- 8.4, the DPV and cyclic voltammetry of the drug domperidone (I) at GCE showed an irreversible
and diffusion controlled oxidation wave. The values of the electron transfer coefficient (α) involved in the rate determining
step were found in the range 0.64± 0.05 confirming the irreversible nature of the peak. The analysis of the drug in pure form
and in wastewater samples was successfully achieved 相似文献
10.
Guyon F Gaillard L Salagoïty MH Médina B 《Analytical and bioanalytical chemistry》2011,401(5):1555-1562
High-performance liquid chromatography linked to isotope ratio mass spectrometry (HPLC-co-IRMS) via a Liquiface? interface has been used to simultaneously determine 13C isotope ratios of glucose (G), fructose (F), glycerol (Gly) and ethanol (Eth) in sweet and semi-sweet wines. The data has
been used the study of wine authenticity. For this purpose, 20 authentic wines from various French production areas and various
vintages have been analyzed after dilution in pure water from 20 to 200 times according to sugar content. If the 13C isotope ratios vary according to the production area and the vintage, it appears that internal ratios of 13C isotope ratios (
R13\textC {R_{{{}^{{13}}{\text{C}}}}} ) of the four compounds studied can be considered as a constant. Thus, ratios of isotope ratios are found to be 1.00 ± 0.04
and 1.02 ± 0.08 for
R13\textC\textG/F {R_{{{}^{{13}}{{\text{C}}_{{{\text{G/F}}}}}}}} and
R13\textC\textGly/Eth {R_{{{}^{{13}}{{\text{C}}_{{{\text{Gly/Eth}}}}}}}} , respectively. Moreover,
R13\textC\textEth/Sugar {R_{{{}^{{13}}{{\text{C}}_{{{\text{Eth/Sugar}}}}}}}} is found to be 1.15 ± 0.10 and 1.16 ± 0.08 for
R13\textC\textGly/Sugar {R_{{{}^{{13}}{{\text{C}}_{{{\text{Gly/Sugar}}}}}}}} . Additions of glucose, fructose and glycerol to a reference wine show a variation of the
R13\textC {R_{{{}^{{13}}{\text{C}}}}} value for a single product addition as low as 2.5 g/L−1. Eighteen commercial wines and 17 concentrated musts have been analyzed. Three wine samples are suspicious as the
R13\textC {R_{{{}^{{13}}{\text{C}}}}} values are out of range indicating a sweetening treatment. Moreover, concentrated must analysis shows that 13C isotope ratio can be also used directly to determine the authenticity of the matrix. 相似文献
11.
J. M. Santana-Casiano M. González-Dávila F. J. Millero 《Journal of solution chemistry》2008,37(6):749-762
The stability constants for the hydrolysis of Cu(II) and formation of chloride complexes in NaClO4 solution, at 25 °C, have been examined using the Pitzer equations. The calculated activity coefficients of CuOH+, Cu(OH)2, Cu2(OH)3+, Cu2(OH)22+, CuCl+ and CuCl2 have been used to determine the Pitzer parameter (β
i
(0), β
i
(1), and C
i
) for these complexes. These parameters yield values for the hydrolysis constants (log 10
β
1*, log 10
β
2*, log 10
β
2,1* and log 10
β
2,2*) and the formation of the chloride complexes (log 10
β
CuCl* and
that agree with the experimental measurements, respectively to ±0.01,±0.02,±0.03,±0.06,±0.03 and ±0.07.
The stability constants for the hydrolysis and chloride complexes of Cu(II) were found to be related to those of other divalent
metals over a wide range of ionic strength. This has allowed us to use the calculated Pitzer parameters for copper complexes
to model the stability constants and activity coefficients of hydroxide and chloride complexes of other divalent metals. The
applicability of the Pitzer Cu(II) model to the ionic strength dependence of hydrolysis of zinc and cadmium is presented.
The resulting thermodynamic hydroxide and chloride constants for zinc are
and
. For cadmium the thermodynamic hydrolysis constants are
and
. The Cu(II) model allows one to determine the stability of other divalent metal complexes over a wide range of concentration
when little experimental data are available. More reliable stepwise stability constants for divalent metals are needed to
test the linearity found for the chloro complexes. 相似文献
12.
Mg isotope fractionation in biogenic carbonates of deep-sea coral, benthic foraminifera, and hermatypic coral 总被引:1,自引:0,他引:1
Yoshimura T Tanimizu M Inoue M Suzuki A Iwasaki N Kawahata H 《Analytical and bioanalytical chemistry》2011,401(9):2755-2769
High-precision Mg isotope measurements by multiple collector inductively coupled plasma mass spectrometry were applied for
determinations of magnesium isotopic fractionation of biogenic calcium carbonates from seawater with a rapid Mg purification
technique. The mean δ26Mg values of scleractinian corals, giant clam, benthic foraminifera, and calcite deep-sea corals were −0.87‰, −2.57‰, −2.34‰,
and −2.43‰, suggesting preferential precipitation of light Mg isotopes to produce carbonate skeleton in biomineralization.
Mg isotope fractionation in deep-sea coral, which has high Mg calcite skeleton, showed a clear temperature (T) dependence from 2.5 °C to 19.5 °C: 1,000 × ln(α) = −2.63 (±0.076) + 0.0138 (±0.0051) × T(R
2 = 0.82, p < 0.01). The δ26Mg values of large benthic foraminifera, which are also composed of a high-Mg calcite skeleton, can be plotted on the same
regression line as that for deep-sea coral. Since the precipitation rates of deep-sea coral and benthic foraminifera are several
orders of magnitude different, the results suggest that kinetic isotope fractionation may not be a major controlling factor
for high-Mg calcite. The Mg isotope fractionation factors and the slope of temperature dependence from deep-sea corals and
benthic foraminifera are similar to that for an inorganically precipitated calcite speleothem. Taking into account element
partitioning and the calcification rate of biogenic CaCO3, the similarity among inorganic minerals, deep-sea corals, and benthic foraminiferas may indicate a strong mineralogical
control on Mg isotope fractionation for high-Mg calcite. On the other hand, δ26Mg in hermatypic corals composed of aragonite has been comparable with previous data on biogenic aragonite of coral, sclerosponges,
and scaphopad, regardless of species differences of samples. 相似文献
13.
A matrix removal procedure has been developed for the determination of trace elements, including As, Cd, Co, Cr, Cu, Hg, Ni,
Pb, Sb, Se, Sn, Tl, Zn and V, in siliceous materials by inductively coupled plasma mass spectrometry (ICP-MS). Soil and sediment
samples were dissolved in a mixture of HNO3 and HF in sealed vessels by using a microwave oven. Silicon matrix in the solutions was precipitated as sparingly soluble
sodium fluorosilicate (Na2SiF6) by adding 0.5 mL of 300 mg mL−1 NaCl solution. Simultaneous precipitation of sodium and silicon was achieved in highly acidic solutions containing 30–40%
(v/v) HNO3. A mixture of methanol and nitric acid afforded back-extraction of the trace elements without significant dissolution of
the Na2SiF6. Samples were analyzed by ICP-MS for trace elements and residual silicon. Calibration was made by aqueous multi-element standard
solutions. Up to 95% of the silicon was successfully removed yielding solutions suitable for introduction to ICP-MS. The method
was validated by analysis of two NIST certified reference materials; SRM 2711 (Montana Soil) and SRM 2704 (Buffalo River Sediment).
Accurate results were obtained for all elements, including those for As, Hg and Se that suffer from losses due to the presence
of their volatile species when silicon was converted to volatile SiF4 via heat-assisted evaporation to dryness. The recoveries from the SRM samples varied between 80% (Cr) and 109% (Hg). No significant
interferences were observed from molecular ions of chloride and residual sodium on 75As, 63Cu, 60Ni, 77Se and 51V.
Correspondence: Zikri Arslan, Department of Chemistry, Jackson State University, Jackson, MS 39217, USA 相似文献
14.
Boulyga SF Heilmann J Prohaska T Heumann KG 《Analytical and bioanalytical chemistry》2007,389(3):697-706
A method for the direct multi-element determination of Cl, S, Hg, Pb, Cd, U, Br, Cr, Cu, Fe, and Zn in powdered coal samples
has been developed by applying inductively coupled plasma isotope dilution mass spectrometry (ICP-IDMS) with laser-assisted
introduction into the plasma. A sector-field ICP-MS with a mass resolution of 4,000 and a high-ablation rate laser ablation
system provided significantly better sensitivity, detection limits, and accuracy compared to a conventional laser ablation
system coupled with a quadrupole ICP-MS. The sensitivity ranges from about 590 cps for 35Cl+ to more than 6 × 105 cps for 238U+ for 1 μg of trace element per gram of coal sample. Detection limits vary from 450 ng g−1 for chlorine and 18 ng g−1 for sulfur to 9.5 pg g−1 for mercury and 0.3 pg g−1 for uranium. Analyses of minor and trace elements in four certified reference materials (BCR-180 Gas Coal, BCR-331 Steam
Coal, SRM 1632c Trace Elements in Coal, SRM 1635 Trace Elements in Coal) yielded good agreement of usually not more than 5%
deviation from the certified values and precisions of less than 10% relative standard deviation for most elements. Higher
relative standard deviations were found for particular elements such as Hg and Cd caused by inhomogeneities due to associations
of these elements within micro-inclusions in coal which was demonstrated for Hg in SRM 1635, SRM 1632c, and another standard
reference material (SRM 2682b, Sulfur and Mercury in Coal). The developed LA-ICP-IDMS method with its simple sample pretreatment
opens the possibility for accurate, fast, and highly sensitive determinations of environmentally critical contaminants in
coal as well as of trace impurities in similar sample materials like graphite powder and activated charcoal on a routine basis.
Figure LA-ICP-IDMS allows direct multi-element determination in powdered coal samples 相似文献
15.
Ming-Zhou Zhang Min-Zi Wang Zong-Lun Chen Jie-Hong Fang Mei-Ming Fang Jun Liu Xiao-Ping Yu 《Analytical and bioanalytical chemistry》2009,395(8):2591-2599
A multianalyte lateral-flow immunochromatographic technique using colloidal gold-labeled polyclonal antibodies was developed
for the rapid simultaneous detection of clenbuterol and ractopamine. The assay procedure could be accomplished within 5 min,
and the results of this qualitative one-step assay were evaluated visually according to whether test lines appeared or not.
When applied to the swine urines, the detection limit and the half maximal inhibitory concentration (IC50) of the test strip under an optical density scanner were calculated to be 0.1 ± 0.01 ng mL−1 and 0.1 ± 0.01 ng mL−1, 0.56 ± 0.08 ng mL−1, and 0.71 ± 0.06 ng mL−1, respectively, the cut-off levels with the naked eye of 1 ng mL−1 and 1 ng mL−1 for clenbuterol and ractopamine were observed. Parallel analysis of swine urine samples with clenbuterol and ractopamine
showed comparable results obtained from the multianalyte lateral-flow test strip and GC-MS. Therefore, the described multianalyte
lateral-flow test strip can be used as a reliable, rapid, and cost-effective on-site screening technique for the simultaneous
determination of clenbuterol and ractopamine residues in swine urine.
相似文献
16.
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
17.
Relativistic energy-consistent small-core lanthanide pseudopotentials of the Stuttgart–Bonn variety and extended valence
basis sets have been used for the investigation of the dimers La2 and Lu2. It was found that the ground states for La2 and Lu2 are most likely 1∑
g
+ (σ
g
2π
u
4) and 3∑
g
− (4f
144f
14σ
g
2σ
u
2πu
2), respectively. The molecular constants including error bars were derived from multireference configuration interaction as
well as coupled-cluster calculations, taking into account corrections for atomic spin–orbit splitting as well as possible
basis set superposition errors. The theoretical values for La2 (R
e=2.70±0.03 ?, D
e=2.31±0.13 eV, ωe=186±13 cm−1) show good agreement with the experimental binding energy (D
e=2.52±0.22 eV), but the experimental vibrational constant in an Ar matrix (ωe=236±0.8 cm−1) is significantly higher. For Lu2 the theoretical values (R
e=3.07±0.03 ?, D
e=1.40±0.12 eV, ωe=123±1 cm−1) are in overall excellent agreement with experimental data (D
e=1.43±0.34 eV, ωe=122± 1 cm−1). The electronic structures of La2 and Lu2 are compared to those other lanthanide dimers and trends in the series are discussed.
Received: 25 March 2002 / Accepted: 2 June 2002 / Published online: 21 August 2002 相似文献
18.
The deuterium-isotope effects on the ionization constants of β-naphthol (2-naphthol) and boric acid, Δlog 10
K=[log 10
K
D2O−log 10
K
H2O], have been determined from measurements in light and heavy water at temperatures from 225 °C≤t≤300 °C and pressures near steam saturation. β-Naphthol is a thermally-stable colorimetric pH indicator, whose ionization constant lies close to that of H2PO4− (aq), the only acid for which Δlog 10
K is accurately known at elevated temperatures. A newly designed platinum flow cell was used to measure UV-visible spectra
of β-naphthol in acid, base, and buffer solutions of H2PO4−/HPO42− and D2PO4−/DPO42−, from which the degree of ionization at known values of pH and pD was determined. Values of the ionization constants of β-naphthol in light and heavy water were calculated from these results, and used to derive a model for
and
over the experimental temperature range with an estimated precision of ±0.02 in log 10
K. The new values of K
H2O and K
D2O allowed us to use β-naphthol as a colorimetric indicator, to measure the equilibrium pH and pD of the buffer solutions B(OH)3/B(OH)4− and B(OD)3/B(OD)4− up to 300 °C, from which the ionization constants of boric acid were calculated. The magnitude of the deuterium isotope effect
for H2PO4− (aq) is known to fall from Δlog 10
K=−0.62 to Δlog 10
K=−0.47, on the “aquamolal” concentration scale, as the temperature rises above 125 °C, but then remains almost constant. Although
the temperature range is more limited, the new results for β-naphthol and boric acid appear to show a similar trend. 相似文献
19.
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
20.
Measurements of the electrophoretic mobility (u
E) of particles of colloidal α-alumina were made as a function of pH, electrolyte concentration and electrolyte type (NaCl,
NaNO3 and KCl) using two similar instrumental techniques. Significant differences (50% or less) in the values of u
E of particles in NaCl were obtained from the two instruments; however, the isoelectric points (IEPs) (the pH at which u
E=0), estimated from the two sets of measurements, occurred at 7.5 ± 0.3 and 7.8 ± 0.05 and were not significantly different.
The latter estimate corresponds with those for particles in KCl and NaNO3 of 8.05 ± 0.11 and 7.95 ± 0.18, respectively, made using the same instrument and indicate that the IEP was a weak function
of electrolyte type. When cations acted as counterions (pH > IEP), the absolute magnitudes and the ranges of u
E with electrolyte concentration were found to be significantly less than when anions acted as counterions (IEP > pH). Estimates
of the zeta potential (ζ), made using various procedures, showed variations of up to 25% at low ratios of electrical-double-layer
thickness (κ
−1) to particle radius (a) (κa∼10) and were of a similar scale to differences in u
E, but no significant variations (95% confidence) in ζ were obtained at high values (κa∼200).
Received: 12 July 2000 Accepted: 17 October 2000 相似文献