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1.
Vesuvianite, a complex sorosilicate, often contains variable (from trace-to-minor-element) amounts of H, B and F. We describe
a microanalytical study of H, B and F in vesuvianite by means of Electron Probe Microanalysis (EPMA), Secondary Ion Mass Spectrometry
(SIMS), and single-crystal Fourier-Transform InfraRed (FTIR) spectroscopy. Most crystals investigated are B- (up to 3.67 wt%
B2O3) and F-rich (up to 2.38 wt%); H2O ranges from 0.243 to 0.665 wt%. The H data obtained by SIMS allowed us to calibrate the quantitative analysis of H2O by FTIR spectroscopy. The resulting molar absorption coefficient (ɛ
i
= 100 000 ± 2000 L · mol−1 · cm−2) is in excellent agreement with working curves available from the literature. Moreover, the SIMS data allowed us to obtain
the calibration curve to estimate the B2O3 content on the basis on the FTIR absorbance: a
i
= 34000 ± 1400 · B2O3 (wt%). 相似文献
2.
Mohammad A. Mottaleb 《Mikrochimica acta》1999,132(1):31-39
A reversed-phase high performance liquid chromatography (RP-HPLC) method, with acetic acid and sodium perchlorate phase modifiers,
was developed to separate a mixture of linear alkylbenzene sulphonates (LAS), containing 10 to 13 carbon atoms. The effects
of methanol-water compositions and concentrations of used modifiers were investigated and compared. The separation achieved
with 50 mg L−1 acetic acid was found satisfactory whereas a concentration of 10 g L−1 sodium perchlorate was preferred. Chromatograms obtained with UV and Fourier transform infrared (FTIR) detection showed almost
similar features and HPLC-FTIR interface spectra of LAS components exhibited excellent agreement of absorption features to
those of standard FTIR spectrum and no thermal degradation was found to occur.
Received May 20, 1998 Revision March 25, 1999. 相似文献
3.
Lottmann A Cadé E Geagea ML Delhomme O Grand C Veilleraud C Rizet AL Mirabel P Millet M 《Analytical and bioanalytical chemistry》2007,387(5):1855-1861
In to order increase sensitivity and to reduce the background induced by matrix effects, a method was developed that uses
flash chromatography to separate various compounds present in atmospheric aerosol samples prior to their analysis with different
analytical techniques (GC–MS, GC–FID, HPLC). For this purpose, flash chromatography using a 4 g silica gel column crossed
by eluent at a flow rate of 20 mL min−1 was used. An eluent with enhanced polarity is needed to separate nonpolar (linear and branched alkanes), semipolar (PAH,
nitro-PAH and cholesterol) and polar (methoxyphenols, alkanoic acids, and levoglucosan) compounds. Three combinations of solvents
were used: hexane for the nonpolar fraction (F1), toluene/hexane for the semipolar fraction (F2) and dimethylformamide for
the polar fraction (F3). The use of different eluents for each fraction allows separation of the sample to be accomplished
with good repeatability and satisfying yields [85 ± 5% for F1, 81 ± 8% (PAHs), 89 ± 6% (nitro-PAHs) and 74 ± 7% (cholesterol)
for F2 and 79 ± 7% (n-alkanoic acids), 40 ± 11% (methoxyphenols) and 77 ± 6% (levoglucosan) for F3]. The methoxyphenol yields were low due to losses
during the concentration/evaporation step. This method was then applied to analyse the organic composition of particles collected
at an urban site in Strasbourg (France). 相似文献
4.
Noreen R Chien CC Delugin M Yao S Pineau R Hwu Y Moenner M Petibois C 《Analytical and bioanalytical chemistry》2011,401(3):845-852
Fourier transform infrared (FTIR) imaging has been used as a molecular histopathology tool on brain tissue sections after
intracranial implantation and development of glioma tumors. Healthy brain tissue (contralateral lobe) as well as solid and
diffuse tumor tissues were compared for their collagen contents. IR spectra were extracted from IR images for determining
the secondary structure of protein contents and compared to pure product spectra of collagens (types I, III, IV, V, and VI).
Multivariate statistical analyses of variance and correspondence factorial analysis were performed to differentiate healthy
and tumor brain tissues as well as their classification according to their secondary structure profiles. Secondary structure
profiles revealed that no collagen was present in healthy tissues; they are also significantly different from solid and diffuse
tumors (p < 0.05). Solid and diffuse tumors could be discriminated with respect to the secondary structure profile of fibrillar and
non-fibrillar collagens, respectively. We can thus propose to develop FTIR imaging for histopathology examination of tumors
on the basis of collagen contents. 相似文献
5.
R. DellAnna P. Lazzeri M. Frisanco F. Monti F. Malvezzi Campeggi E. Gottardini M. Bersani 《Analytical and bioanalytical chemistry》2009,394(5):1443-1452
The discrimination and classification of allergy-relevant pollen was studied for the first time by mid-infrared Fourier transform
infrared (FT-IR) microspectroscopy together with unsupervised and supervised multivariate statistical methods. Pollen samples
of 11 different taxa were collected, whose outdoor air concentration during the flowering time is typically measured by aerobiological
monitoring networks. Unsupervised hierarchical cluster analysis provided valuable information about the reproducibility of
FT-IR spectra of the same taxon acquired either from one pollen grain in a 25 × 25 μm2 area or from a group of grains inside a 100 × 100 μm2 area. As regards the supervised learning method, best results were achieved using a K nearest neighbors classifier and the leave-one-out cross-validation procedure on the dataset composed of single pollen grain
spectra (overall accuracy 84%). FT-IR microspectroscopy is therefore a reliable method for discrimination and classification
of allergenic pollen. The limits of its practical application to the monitoring performed in the aerobiological stations were
also discussed.
Figure Traditional and innovative methods for the identification of airborne pollen grains 相似文献
6.
Tim De Meyer Davy Sinnaeve Bjorn Van Gasse Ernst-R Rietzschel Marc L. De Buyzere Michel R. Langlois Sofie Bekaert José C. Martins Wim Van Criekinge 《Analytical and bioanalytical chemistry》2010,398(4):1781-1790
Proton nuclear magnetic resonance (1H-NMR)-based metabolomics enables the high-resolution and high-throughput assessment of a broad spectrum of metabolites in
biofluids. Despite the straightforward character of the experimental methodology, the analysis of spectral profiles is rather
complex, particularly due to the requirement of numerous data preprocessing steps. Here, we evaluate how several of the most
common preprocessing procedures affect the subsequent univariate analyses of blood serum spectra, with a particular focus
on how the standard methods perform compared to more advanced examples. Carr–Purcell–Meiboom–Gill 1D 1H spectra were obtained for 240 serum samples from healthy subjects of the Asklepios study. We studied the impact of different
preprocessing steps—integral (standard method) and probabilistic quotient normalization; no, equidistant (standard), and adaptive-intelligent
binning; mean (standard) and maximum bin intensity data summation—on the resonance intensities of three different types of
metabolites: triglycerides, glucose, and creatinine. The effects were evaluated by correlating the differently preprocessed
NMR data with the independently measured metabolite concentrations. The analyses revealed that the standard methods performed
inferiorly and that a combination of probabilistic quotient normalization after adaptive-intelligent binning and maximum intensity
variable definition yielded the best overall results (triglycerides, R = 0.98; glucose, R = 0.76; creatinine, R = 0.70). Therefore, at least in the case of serum metabolomics, these or equivalent methods should be preferred above the
standard preprocessing methods, particularly for univariate analyses. Additional optimization of the normalization procedure
might further improve the analyses. 相似文献
7.
Jemma G. Kelly Plamen P. Angelov Júlio Trevisan Anastasia Vlachopoulou Evangelos Paraskevaidis Pierre L. Martin-Hirsch Francis L. Martin 《Analytical and bioanalytical chemistry》2010,398(5):2191-2201
Although the UK cervical screening programme has reduced mortality associated with invasive disease, advancement from a high-throughput
predictive methodology that is cost-effective and robust could greatly support the current system. We combined analysis by
attenuated total reflection Fourier-transform infrared spectroscopy of cervical cytology with self-learning classifier eClass.
This predictive algorithm can cope with vast amounts of multidimensional data with variable characteristics. Using a characterised
dataset [set A: consisting of UK cervical specimens designated as normal (n = 60), low-grade (n = 60) or high-grade (n = 60)] and one further dataset (set B) consisting of n = 30 low-grade samples, we set out to determine whether this approach could be robustly predictive. Variously extending the
training set consisting of set A with set B data produced good classification rates with three two-class cascade classifiers.
However, a single three-class classifier was equally efficient, producing a user-friendly, applicable methodology with improved
interpretability (i.e., better classification with only one set of fuzzy rules). As data from set B were added incrementally
to the training set, the model learned and evolved. Additionally, monitoring of results of the set B low-grade specimens (known
to be low-grade cervical cytology specimens) provided the opportunity to explore the possibility of distinguishing patients
likely to progress towards invasive disease. eClass exhibited a remarkably robust predictive power in a user-friendly fashion
(i.e., high throughput, ease of use) compared to other classifiers (k-nearest neighbours, support vector machines, artificial neural networks). Development of eClass to classify such datasets
for applications such as screening exhibits robustness in identifying a dichotomous marker of invasive disease progression. 相似文献
8.
Othman AM El-Houseini ME El-Sofy MS Aboul-Enein HY 《Analytical and bioanalytical chemistry》2011,400(3):787-795
The activity of the α-l-fucosidase (AFU) enzyme represents an excellent test for diagnosis of hepatocellular carcinoma (HCC) and fucosidosis recognized
in inborn disorder of metabolism and increases the sensitivity of detection to 95.5% in patients with HCC. Therefore, the
determination of the activity of AFU enzyme is very important and can be used as a screening tool for the early diagnosis
of tumors for HCC patients. A simple, accurate, and sensitive potentiometric method was developed for measuring the activity
of AFU. The method was based upon measuring the concentration of 2-chloro-4-nitrophenol (2-chloro-4-NP) using a 2-chloro-4-NP-rhodamine
B ion pair in a PVC membrane sensor. The electrode shows a linear, reproducible, and stable potentiometric response with an
anionic Nernstian slope of −51.13 ± 0.6 mV/decade over a wide range of concentrations 10−5–10−2 M and a detection limit of 1.0 × 10−6 M of 2-chloro-4-NP. The membrane exhibits a fast response time of 30 s, over a pH range of 4.0–6.5. The selectivity coefficients
indicate excellent selectivity for 2-chloro-4-NP over a number of interfering species, e.g., chloride, nitrate, sulfate, chromate
urea, albumin, glucose, uric acid, and total protein. The prepared sensor has been used successfully for the determination
of 2-chloro-4-NP produced from the hydrolysis of 2-chloro-4-NP-α-l-fucopyranoside substrate. It was also applied for the determination α-l-fucosidase enzyme of 33 serum samples of healthy subjects and patients. The average recoveries ± RSD for the healthy subjects,
cirrhosis of chronic hepatitis C and B, and HCC serum samples were 102.6 ± 1.01%, 101.5 ± 0.95%, and 100.1 ± 1.1%, respectively.
The results obtained are in good agreement with those obtained by standard methods. 相似文献
9.
Ewa Bobrowska-Grzesik 《Mikrochimica acta》2001,136(1-2):31-34
Derivative spectrophotometry was applied for the simultaneous determination of amoxycillin and clavulanic acid in pharmaceutical
preparations: “Augmentin” inj. and tablets and “Amoksiklav” drops and tablets, in solutions after hydrolysis with sodium hydroxide.
As the absorption spectra overlap strongly (amoxycillin λmax = 247 nm and 290 nm, clavulanic acid λmax = 258 nm) the first and the second derivative spectrophotometric procedure was elaborated for their determination. Amoxycillin
was determined at λ = 257.9 nm (1-st derivative spectra) or λ = 273 nm (2-nd derivative) while clavulanic acid at λ = 280.3 nm
(1-st derivative) or λ = 285 nm (2-nd derivative spectra). The Beer’s law is obeyed in the range of 0.004–0.04 mg/ml for amoxycillin
and 0.002–0.02 mg/ml for clavulanic acid.
Received December 6, 1999. Revision August 1, 2000. 相似文献
10.
Kilpatrick LE Neta P Yang X Simón-Manso Y Liang Y Stein SE 《Journal of the American Society for Mass Spectrometry》2012,23(4):655-663
Tandem mass spectra of peptide ions, acquired in shotgun proteomic studies of selected proteins, tissues, and organisms, commonly
include prominent peaks that cannot be assigned to the known fragmentation product ions (y, b, a, neutral losses). In many
cases these persist even when creating consensus spectra for inclusion in spectral libraries, where it is important to determine
whether these peaks represent new fragmentation paths or arise from impurities. Using spectra from libraries and synthesized
peptides, we investigate a class of fragment ions corresponding to yn-1 + 10 and yn-1 + 11, where n is the number of amino acid residues in the peptide. These 10 and 11 Da differences in mass of the y ion were
ascribed before to the masses of [+ CO – H2O] and [+ CO – NH3], respectively. The mechanism is suggested to involve dissociation of the N-terminal residue at the CH-CO bond following
loss of H2O or NH3. MS3 spectra of these ions show that the location of the additional 10 or 11 Da is at the N-terminal residue. The yn-1 + 10 ion is most often found in peptides with N-terminal proline, asparagine, and histidine, and also with serine and threonine
in the adjacent position. The yn-1 + 11 ion is observed predominantly with histidine and asparagine at the N-terminus, but also occurs with asparagine in positions
two through four. The intensities of the yn-1 + 10 ions decrease with increasing peptide length. These data for yn-1 + 10 and yn-1 + 11 ion formation may be used to improve peptide identification from tandem mass spectra. 相似文献
11.
Pavel Horváth František Schauer Ivo Kuřitka Ota Salyk Martin Weiter Norbert Dokoupil Stanislav Nešpůrek Vlastimil Fidler 《Monatshefte für Chemie / Chemical Monthly》2001,132(1):177-183
Summary. The photoluminescence of plasma-prepared polysilanes during the change from linear 1D Si chains to an amorphous 3D Si network
was studied. The excitonic absorption band with a maximum at 353 nm in 1D Si experiences a blue shift and broadening upon
introduction of branching and networking defects. With the gradual transition from 1D to 3D structure, an extensive redistribution
of oscillator intensity along the absorption edge, accompanied by a decrease of the resolution of the σ-σ* band, was observed. In the short wavelength region of the excitation spectra there is an enormous increase of excitonic emission
at 328 nm. This effect is tentatively attributed to the excitation of the phenyl group or to the phenyl-silicon bond as confirmed
by effusion spectra of the phenyl species.
Received July 10, 2000. Accepted (revised) September 8, 2000 相似文献
12.
Boris Orel Marjeta Maček Jože Grdadolnik Anton Meden 《Journal of Solid State Electrochemistry》1998,2(4):221-236
Niobium oxide (Nb2O5) films and powders have been obtained via the sol-gel route from an NbCl5 precursor. XRD spectra revealed that films with pseudohexagonal (TT-phase) and orthorhombic (T-phase) structure were formed
at 500 °C and 800 °C, respectively, while at 300 °C films were amorphous. Infrared (IR) and Raman spectra of powders and
films of Nb2O5 in different polymorphic forms were detected, and vibrational band assignments were made. Electrochromic properties of amorphous
films and films with the TT-phase were established from in situ ultraviolet visible (UV-Vis) spectroelectrochemical measurements
and correlated with ex situ IR transmission spectra of charged films. Ex situ IR spectra revealed that charging of amorphous
films is accompanied by variations of the Nb-O stretching mode intensity, while, for films with the TT- and T-phase, splitting
of the Nb3-O stretching modes and the appearance of polaron absorption were noted with Li+ ion insertion. Ex situ X-ray diffraction (XRD) spectra of charged films with the TT-phase showed changes of the unit cell
dimensions with charging. The influence of the polaron absorption on the ex situ near-grazing incidence angle (NGIA) IR reflection-absorption
spectra of charged/discharged films is discussed in detail.
Received: 21 August 1997 / Accepted: 9 October 1997 相似文献
13.
C. Petibois M. Cestelli-Guidi M. Piccinini M. Moenner A. Marcelli 《Analytical and bioanalytical chemistry》2010,397(6):2123-2129
FTIR microscopy with a focal plane array (FPA) of detectors enables routine chemical imaging on individual cells in only a
few minutes. The brilliance of synchrotron radiation (SR) IR sources may enhance the signal obtained from such small biosamples
containing small amounts of organic matter. We investigated individual cells obtained from a cell culture specifically developed
for transmission FTIR imaging using either a Globar or an SR source coupled to the same instrumentation. SR-IR source focussing
was optimized to control the energy distribution on the FPA of detectors. Here we show that accessing the IR absorption distribution
from all the organic contents of cells at 1 × 1 μm pixel resolution was possible only with high circulating current (≥1.2
A) illuminating a limited number of the FPA’s detectors to increase the signal-to-noise ratio of IR images. Finally, a high-current
SR ring is mandatory for collecting FTIR images of biosamples with a high contrast in minutes. 相似文献
14.
A novel method for the determination of proteins at nanogram levels was proposed based on the decrease of resonance light
scattering (RLS) signal resulting from the interaction of dibromo-o-nitrophenylfluorone (DBONPF)-sodium lauroyl glutamate
(SLG) with proteins. At pH 2.97, the decrease RLS intensity was proportional to the concentration of proteins in the range
of nanogram levels with 3σ detection limits being 3.4 ng mL−1 for bovine serum albumin (BSA), 1.7 ng mL−1 for human serum albumin (HSA), 4.1 ng mL−1 for γ-globulin (γ-IgG), 4.4 ng mL−1 for egg albumin, 6.2 ng mL−1 for pepsin (Pep) and 3.7 ng mL−1 for α-chymotrypsin (Chy). The method is no protein-to-protein variability, simple, rapid, practical and relatively free
from interference from coexisting substance, as well as much more sensitive than most of the reported methods. The proposed
method was successfully applied to determine total protein in human serum samples. 相似文献
15.
Ramesh Kumar Banjare Manoj Kumar Banjare Sandhyarani Panda 《Journal of solution chemistry》2020,49(1):34-51
A comprehensive study the effect of acetonitrile (ACN) with four cationic surfactants, viz. tetradecyltrimethylammonium bromide (TTAB), cetyltrimethylammonium bromide (CTAB), cetylpyridinium chloride (CPC) and cetylpyridinium bromide (CPB) was made by using the conductivity, surface tension, fluorescence and FTIR techniques. Significant micellar, interfacial and thermodynamic properties were studied by the tensiometeric and conductivity methods. The critical micelle concentration (CMC), aggregation number (Nagg), and Stern–Volmer constants (Ksv) have also been studied by the steady state fluorescence method using pyrene as probe. The fluorescence study also supports the CMC results obtained from conductivity and surface tension. FTIR was used to ascertain that the strength of intermolecular interactions such as hydrogen bonding, ion–ion pair interactions and induced dipole interactions between the surfactants and ACN depend upon the head-group of the surfactants. The interaction of surfactants with ACN is energetically favorable and occurs via direct interactions between the surfactants and ACN. The results further revealed that the strength of interactions between the surfactants and ACN follows the order: TTAB > CTAB > CPC > CPB. 相似文献
16.
Gazi E Dwyer J Lockyer NP Gardner P Shanks JH Roulson J Hart CA Clarke NW Brown MD 《Analytical and bioanalytical chemistry》2007,387(5):1621-1631
Prostate cancer (CaP) cells preferentially metastasise to the bone marrow, a microenvironment that plays a substantial role
in the sustenance and progression of the CaP tumour. Here we use a combination of FTIR microspectroscopy and histological
stains to increase molecular specificity and probe the biochemistry of metastatic CaP cells in bone marrow tissue derived
from a limited source of paraffin-embedded biopsies of different patients. This provides distinction between the following
dominant metabolic processes driving the proliferation of the metastatic cells in each of these biopsies: glycerophospholipid
synthesis from triacylglyceride, available from surrounding adipocytes, in specimen 1, through significantly high (p ≤ 0.05) carbohydrate (8.23 ± 1.44 cm−1), phosphate (6.13 ± 1.5 cm−1) and lipid hydrocarbon (24.14 ± 5.9 cm−1) signals compared with the organ-confined CaP control (OC CaP), together with vacuolation of cell cytoplasm; glycolipid synthesis
in specimen 2, through significantly high (p ≤ 0.05) carbohydrate (5.51 ± 0.04 cm−1) and high lipid hydrocarbon (17.91 ± 2.3 cm−1) compared with OC CaP, together with positive diastase-digested periodic acid Schiff staining in the majority of metastatic
CaP cells; glycolysis in specimen 3, though significantly high (p ≤ 0.05) carbohydrate (8.86 ± 1.78 cm−1) and significantly lower (p ≤ 0.05) lipid hydrocarbon (11.67 ± 0.4 cm−1) than OC CaP, together with negative diastase-digested periodic acid Schiff staining in the majority of metastatic CaP cells.
Detailed understanding of the biochemistry underpinning the proliferation of tumour cells at metastatic sites may help towards
refining chemotherapeutic treatment. 相似文献
17.
On the basis of flow injection analysis technology, a simple, accurate, and sensitive method has been developed for the determination
of volatile phenols in environmental water samples by using CdTe/ZnSe nanocrystals as a fluorescent probe. The influences
of coexisting metal ions and volatile phenol substitutes were also investigated. The method developed for analysis of volatile
phenols displayed very good linearity in the range from 1.0 × 10−8 to 4.0 × 10−7 g L−1, with a correlation coefficient greater than 0.995 and a detection limit down to 2.7 × 10−9 g L−1 (signal-to-noise ratio 3). The proposed method was successfully applied to determine the content of volatile phenols in environmental
water samples, and the quantitative recoveries were 93.4–106.1%. A possible reaction mechanism for the quenching of fluorescence
is discussed using UV–vis absorption spectra, fluorescence spectra, and time-resolved luminescence spectra of volatile phenols
obtained by titrating a CdTe/ZnSe nanocrystal aqueous solution and zeta potential data. 相似文献
18.
Kelly JG Ahmadzai AA Hermansen P Pitt MA Saidan Z Martin-Hirsch PL Martin FL 《Analytical and bioanalytical chemistry》2011,401(3):957-967
Fine needle aspirates (FNAs) of suspicious breast lesions are often used to aid the diagnosis of female breast cancer. Biospectroscopy
tools facilitate the acquisition of a biochemical cell fingerprint representative of chemical bonds present in a biological
sample. The mid-infrared (IR; 4,000–400 cm−1) is absorbed by the chemical bonds present, allowing one to derive an absorbance spectrum. Complementary to IR spectroscopy,
Raman spectroscopy measures the scattering by chemical bonds following excitation by a laser to generate an intensity spectrum.
Our objective was to apply these methods to determine whether a biospectroscopy approach could objectively segregate different
categories of FNAs. FNAs of breast tissue were collected (n = 48) in a preservative solution and graded into categories by a cytologist as C1 (non-diagnostic), C2 (benign), C3 (suspicious,
probably benign) or C5 (malignant) [or C4 (suspicious, probably malignant); no samples falling within this category were identified
during the collection period of the study]. Following washing, the cellular material was transferred onto BaF2 (IR-transparent) slides for interrogation by Raman or Fourier-transform IR (FTIR) microspectroscopy. In some cases where
sufficient material was obtained, this was transferred to low-E (IR-reflective) glass slides for attenuated total reflection–FTIR
spectroscopy. The spectral datasets produced from these techniques required multivariate analysis for data handling. Principal
component analysis followed by linear discriminant analysis was performed independently on each of the spectral datasets for
only C2, C3 and C5. The resulting scores plots revealed a marked overlap of C2 with C3 and C5, although the latter pair were
both significantly segregated (P < 0.001) in the Raman spectra. Good separation was observed between C3 and C5 in all three spectral datasets. Analysis performed
on the average spectra showed the presence of three distinct cytological groups. Our findings suggest that biospectroscopy
tools coupled with multivariate analysis may support the current FNA tests whilst increasing the sensitivity and associated
reliability for improved diagnostics. 相似文献
19.
Interactions between the moieties responsible for the conformations and hydrophobic microdomains in poly(styrene-4-sulphonate)
(PSS) and its copolymers with n-butylvinylether (BVE) were studied by their emission spectra and the lifetimes of the phenyl groups and pyrene used as a
photochemical probe. The emission spectra of PSS shows bands due to dimers and higher aggregates as well as the characteristic
excimer band. At low concentrations, the random copolymers have spectra similar to that of the free monomer, whereas the block
copolymers have spectra like that of PSS. At higher concentrations, the random copolymer also shows these excimer bands, due
to interchain interactions. Results from the emission of pyrene prove that the behaviour of the copolymers with approximately
40% BVE seems to be relatively independent of having random or block configurations. Except at low concentrations (<0.05 g/dl),
where the block copolymer already has a conformation with “stable” hydrophobic microdomains, both types of copolymers behave
similarly. There is an initial aggregate equilibrium between individual chains and aggregates, associated with a relocation
of the probes. At higher concentrations, both copolymers suffer a severe change in conformation, due to the formation of “stable”
hydrophobic microdomains, resulting from interchain interactions. In both cases the lifetimes of pyrene are of the order of
240 ± 10 ns.
Received: 27 August 1998 Accepted: 11 January 1999 相似文献
20.
Luciano Callipo Patrizia Foglia Riccardo Gubbiotti Roberto Samperi Aldo Laganà 《Analytical and bioanalytical chemistry》2009,394(3):811-820
A method for carbonic anhydrase II (CA II) absolute quantification in human serum is presented. This method is based on high-performance
liquid chromatography (HPLC)-Chip microfluidic device incorporating a nanoelectrospray source interfaced to a triple quadrupole
mass spectrometer. The fraction containing CA II was isolated by preparative reversed-phase HPLC, and peptides obtained from
the tryptic digest of the protein mixture were separated by the HPLC-Chip system. The multiple-reaction monitoring acquisition
mode of a selected suitable CA II peptide and peptide internal standard allowed the selective and sensitive determination
of a CA II. Absolute recovery of the method was 52 ± 12%, while analytical recovery was 81 ± 10%. For the eight samples analyzed,
the matrix effect was found to be only −14 ± 6%. A comparison among three regression lines type which were obtained by external
calibration, matrix-matched calibration, and standard addition method, respectively, demonstrated that the first one is adequate
in obtaining good accuracy and precision. Method quantification limit for CA II in serum was estimated to be 2 fmol/mL. CA
II mean concentration in sera from eight healthy subjects was found to be 56 pmol/mL (relative standard deviation 24%). 相似文献