Total internal reflected resonance light scattering determination of protein in human blood serum at water/tetrachloromethane interface with Arsenazo-TB and Cetyltrimethylammonium bromide

A direct quantification of protein in human blood serum samples is proposed based on the measurement of total internal reflected resonance light scattering (TIR-RLS) at water/tetrachloromethane (H₂O/CCl₄) interfaces. At pH 4.10 and in the presence of Cetyltrimethylammonium bromide (CTAB), the interaction of Arsenazo-TB (ATB) with human serum albumin (HSA) results in strong enhanced TIR-RLS signals with the maximum spectra peak located at 330 nm. The enhanced TIR-RLS intensity at 330 nm was found to be proportional to the concentration of HSA in the range 0.5-42.3 μg/ml and its limit of determination (3σ) is 198 ng/ml. The content of HSA in blood serum samples were determined with the recovery of 97-103% for standard addition experiment.     

Spectroscopic diagnosis of colonic dysplasia.

We have developed a method for defining diagnostic algorithms for pathologic conditions based on fluorescence spectroscopy. We apply this method to human colon tissue and show that fluorescence can be used to diagnose the presence or absence of colonic adenoma. This method uses fluorescence excitation-emission matrices (EEM) to identify optimal excitation regions for obtaining fluorescence emission spectra which can be used to differentiate normal and pathologic tissues. In the case of normal and adenomatous colon tissue, these were found to be: 330, 370, and 430 nm +/- 10 nm. At these excitation wavelengths, emission wavelengths for use in diagnostic algorithms are identified from average difference and ratio of the spectra from normal and pathologic tissues. In colon tissue, at 370 nm excitation, 404, 480, and 680 nm were found to be useful emission wavelengths for diagnosing the presence of adenoma in vitro. The basis of colon tissue autofluorescence was investigated using EEM of pure molecules and relevant excitation-emission maxima in the literature.     

Enhancement of the fluorescence of the beryllium-morin complex by non-ionic surfactants

The effect of surfactants on the fluorescence of the beryllium-morin system has been studied. Non-ionic surfactants strongly enhance the fluorescence intensity of the beryllium complex. The addition of Triton X-100 makes possible the fluorimetric determination of submicrogram quantities of beryllium in feebly acidic media (pH 5.8-6.2, hexamine buffer). The fluorescence is excited at 440 nm and measured at 530 nm. The calibration graph is linear up to 10 ng/ml Be and the detection limit is 0.04 ng/ml. The relative standard deviation is 2.2% for beryllium at 0.5 ng/ml concentration and 0.7% for 5.0 ng/ml. The effects of 25 ions commonly found in water have also been studied; Zn(2+) and F(-) give the main interference. The method has been applied to the determination of beryllium in water pollution quality-control samples with satisfactory results.     

Isonitroso-4-Methyl-2-Pentanone for Solvent Extraction and Spectrophotometric Determination of Palladium (II) at Trace Level

Abstract

Isonitroso-4-methyl-2-pentanone (HIMP) is proposed as a new reagent for extraction and photometric determination of Pd(II). The reagent forms a yellow complex with palladium in the pH range 4.0-5.0. The complex extracted into chloroform was measured at 330 nm. The molar absorptivity was found to be 5.37 × 10³ 1 mol^?1 cm^?1 and Sandell's sensitivity 20 ng cm^?2 Beer's law was obeyed over the concentration range 0.1-10.0 μg/ml of palladium. The method is applicable for palladium estimation in Ores and catalysts.     

Flow injection determination of methamidophos using online photo-oxidation and fluorimetric detection

A photochemical method for the determination of methamidophos using a flow injection system is proposed. The method is based on the rapid decomposition of methamidophos in the presence of peroxydisulphate upon irradiation with UV light. The phosphate generated in the photochemical process is made to react with molybdate in dilute nitric acid to form phosphomolybdic acid, which oxidises thiamine to thiochrome. The thiochrome can then be fluorimetrically monitored at 440 nm with excitation at 375 nm. The method shows a linear range between 14 and 1400 ng ml(-1) with a limit of detection of 1.7 ng ml(-1). The repeatability was 0.3% expressed as relative standard deviation (n=10) and the reproducibility, studied on five different days, was +/-3%. The sample throughput was 70 injections per h. The reliability of the method for routine analysis of water and vegetable samples is demonstrated.     

Spectrophotometric determination of manganese by using redox reaction of tris(2,2'-bipyridine)osmium(II) with Mn7+.

This paper reports on the analytical application of the oxidation reaction of [Os(bpy)3]2+ by Mn7+ (MnO4-). The present study developed a very simple, sensitive and selective spectrophotometric method for the determination of manganese in an acidic medium. Three analytical wavelengths were employed in the UV and visible regions at 290, 315 and 480 nm. Beer's law was obeyed up to a concentration of 330 ng ml(-1) of Mn7+ at different wavelengths with regression equations 0.001 - 0.0042C(Mn), 0.001 + 0.0021C(Mn), and 0.001 - 9.34 x 10(-4)C(Mn) at 290, 315 and 480 nm, respectively. Under the optimum conditions, the achieved detection limits were 0.72, 1.37 and 3.32 ng ml(-1) at 290, 315, and 480 nm, respectively. In addition to the high sensitivity of the method (0.24 ng cm(-2) at 290 nm, 0.45 ng cm(-2) at 315 nm and 1.0 ng cm(-2) at 480 nm), it can be used for the determination of manganese in the presence of a large number of anions and cations, since it tolerates most of the potential interferents. The relative standard deviation was 0.5% (n = 11) for 90 ng ml(-1) manganese. The method was successfully applied to the determination of manganese in water from different resources.     

Zur Analytik von Morocromen in biologischem Material

Zusammenfassung Morocromen-Eigenschaften (Löslichkeit, Extraktion, Stabilität, UV, Fluorescenz, DC) werden beschrieben. Aus biologischem Material (Blut, Organe, Galle, Speichel, Schweiß, Faeces und Urin) ist Morocromen bei pH 8,6 mit Chloroform nahezu quantitativ extrahierbar. Quantitative Bestimmung ist UV-spektroskopisch (330 nm), besser fluorimetrisch durchführbar: direkte Bestimmung bei 330/440 nm als Morocromen oder nach Abbau (4 N H₂SO₄, 100° C) zum stärker fluorescierenden 7-Amino-Derivat bei 309/483 nm ist bei Mengen von <0,01–5 g/ml nach vorheriger DC möglich.Die untere Nachweisgrenze liegt zwischen 0,02 g/ml (Blut) und 0,008 g/ml (Urin), die Reproduzierbarkeit zwischen 0,7% (Blut) und 3,0–3,6% (Urin). Die Methoden sind für pharmakokinetische Untersuchungen geeignet.

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Analysis of morocromen in biological material

Summary Properties of morocromen (solubility, extractability, stability, UV-, fluorescence and TLC-properties) are described. Morocromen can be extracted quantitatively from biological material (blood, organs, bile, saliva, sweat, faeces and urine) with chloroform at pH 8.6. Quantitative determination can be carried out either by UV-spectroscopy (330 nm), or even better by fluorometry: direct determination at 330/440 nm as morocromen or after degradation (4N H₂SO₄, 100° C) to the more intensely fluorescing 7-amino-derivative (at 309/483 nm) is possible with amounts of <0.01 to 5 g/ml after previous TLC. The lower detection limit is between 0.02 g/ml (blood) and 0.008 g/ml (urine), reproducibility between 0.7% (blood) and 3.0–3.6% (urine). The methods can be used for pharmacokinetic measurements.

     

HPLC with fluorescence detection of methamphetamine and amphetamine in segmentally analyzed human hair

A sensitive high-performance liquid chromatographic method with fluorescence detection for determining methamphetamine and its major metabolite, amphetamine, in abusers' hair segments was developed. Methamphetamine and amphetamine in hair samples collected from addicts were extracted into acidified methanol, derivatized with 4-(4,5-diphenyl-1H-imidazol-2-yl)benzoyl chloride, separated isocratically on an ODS column using TRIS-HCl buffer (0.1 mol dm-3, pH 7.0)-methanol (30 + 70 v/v) as the mobile phase and the derivatives were detected fluorimetrically at 440 nm (lambda ex 330 nm). Calibration curves obtained by using control human hair spiked with standard solutions were linear (r > or = 0.999) up to at least 676.1 ng mg-1 for amphetamine and 746.1 ng mg-1 for methamphetamine. The detection limits at a signal-to-noise ratio of 3 were 51.4 and 74.6 pg mg-1 hair for amphetamine and methamphetamine, respectively. Using control hair spiked with standard solutions, the intra- and inter-day relative standard deviations (n = 5) were < or = 8.6% for both the target compounds. The method was successfully applied to the segmental analyses of methamphetamine abusers' hair samples.     

BIOLUMINESCENCE OF THE BRITTLE STAR OPHIOPSILA CALIFORNICA

The light-emitting principle of the brittle star Ophiopsila californica has been isolated and purified. It was found to be a green-fluorescent photoprotein (molecular weight 45000) which emits green light (λ_max 500 nm) when H₂O₂ is added, independently of the presence or absence of O₂. The green fluorescence (emission maximum 500 nm, excitation maximum 440 nm) spectrally coincided with the H₂O₂-triggered luminescence, indicating that the green fluorescent chromophore is the light-emitter of the photoprotein luminescence.     

Electrochemical and PM-IRRAS studies of the effect of cholesterol on the properties of the headgroup region of a DMPC bilayer supported at a Au(111) electrode

Polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) was employed to investigate the interaction of cholesterol with the headgroups of dimyristoylphosphatidycholine (DMPC) molecules under a static electric field. DMPC/cholesterol (7:3 molar ratio) mixtures form a bilayer on a Au(111) electrode surface by fusion and spreading of small unilamellar vesicles. PM-IRRAS experiments provided detailed information concerning the conformation and hydration of headgroups of DMPC bilayers in the presence and absence of 30% cholesterol. The presence of 30% cholesterol increases the space between the headgroups of DMPC molecules and hence increases the hydration of the DMPC/cholesterol mixed bilayer. The conformational state of the headgroups of DMPC molecules in the mixed bilayer is also significantly changed. The phosphate group is closer to the surface compared with the pure DMPC bilayer. The conformation of the -O-C-C-N moiety changes from gauche to trans in the presence of cholesterol.     

Spherical and vesicular ionic aggregates in Zn‐neutralized sulfonated polystyrene ionomers

Ionic aggregates in a series of Zn‐neutralized poly(styrene‐co‐styrene sulfonate) (SPS) random ionomers have been imaged using scanning transmission electron microscopy. The Zn‐rich aggregates were found to have two shapes: solid spheres (Type I) and shells or vesicles (Type II). Type I aggregates range in a maximum diameter from 4 to 10 nm, whereas Type II aggregates range in a maximum diameter from 9 to 55 nm with a vesicle wall thickness of ∼ 3 nm. Lightly neutralized ionomers exhibited only Type I aggregates, whereas higher neutralization levels exhibited both Type I and II aggregates. Lightly neutralized ionomers also showed evidence of macrophase separation at the micron size scale. These direct observations of ionic aggregates contradict previous interpretations of small‐angle X‐ray scattering data with respect to size, size dispersity, shape, and spatial distribution. In addition, the aggregates observed in SPS differ markedly from the nearly monodisperse ∼ 2‐nm spherical aggregates observed in Zn‐neutralized poly(ethylene‐co‐methacrylic acid). The presence of vesicular aggregates encourages a re‐examination of the morphologies and properties of styrenic ionomers. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 477–483, 2001     

Enhancement of the fluorescence of the zinc-morin complex by a non-ionic surfactant

A method is described for the fluorimetric determination of zinc, based on formation of a zinc-morin complex in the presence of a non-ionic surfactant. The complex has practically no fluorescence in the absence of surfactant, but the addition of Genapol PF-20 (non-ionic surfactant, ethylene oxide-propylene oxide condensate) makes possible the fluorimetric determination of low concentrations of zinc as it enhances the fluorescence of the complex about 75-fold. Maximum fluorescence is produced at pH 4.7 +/- 0.2 (acetic acid-acetate buffer), with 1.5% surfactant and 0.009% morin. The fluorescence is excited at 433 nm and measured at 503 nm. The calibration graph is linear up to 150 ng/ml zinc concentration and the detection limit is 3 ng/ml. The relative standard deviation (11 replicates) is 2.4% for zinc at 20 ng/ml concentration and 1.7% for 100 ng/ml. Of 29 ions studied, Al(3+), Be(2+), Zr(4+) and Cd(2+) strongly increase the fluorescence of the system, and Fe(3+), Ni(2+), Cu(2+), Ti(IV) and Co(2+) decrease the fluorescence signal.     

Study of Interfacial Charge Transfer from an Electron Rich Organic Molecule to CdTe Quantum Dot by using Stern-Volmer and Stochastic Kinetic Models

Photoinduced electron transfer (PET) from N-methylaniline (NMA) to a photoexcited CdTe quantum dot (QD*) is studied in toluene. The PET mechanism at low to moderate quencher (NMA) concentrations (<0.08 M) remains mostly collisional with some contributions from QD-NMA complex formation. However, at high quencher concentrations (>0.10 M), QDs form larger numbers of static complexes with NMA molecules leading to a steep positive deviation in the steady-state Stern–Volmer curves. An isothermal titration calorimetry (ITC) study confirms the formation of QD-NMA complexes (K∼150 M⁻¹) at high quencher concentrations. Fitting our experimental data using a stochastic kinetic model indicates that the number of NMA molecules attached per QD at highest NMA concentration (∼0.16 M) used in this study decreases from ∼0.76 to ∼0.47 with reducing the QD size from ∼5.2 nm to ∼3.2 nm. However, the PET rate increases with decreasing QD size, which is commensurate with the observation that the chemical driving force (ΔG) increases with decreasing the QD particle size. We have analyzed the PET kinetics mainly by using Stern-Volmer fittings. However, in some cases Tachiya's stochastic kinetic model is used for stoichiometric analysis, which seems to be useful only at high quencher concentrations. The measured PET rate coefficients in all the cases are found to be at least an order of magnitude lower when compared to the diffusion-controlled rate of the reaction medium.     

Direct Determination of Benzo(a)pyrene and Pyrene in Solid Environmental Samples by Jet-Cooled Spectroscopy

Abstract

We report the direct determination of two polycyclic aromatic hydrocarbons (PAH), Benzo(a)Pyrene [B(a)P] and Pyrene (Pyr), in solid environmental samples, i.e. a marine sediment and scrapings from the interior walls of a steel foundry, by the supersonic jet/laser induced fluorescence technique. We have found limits of detection (LOD) for these samples of 900ng (1.8ppm) for B(a)P and 200ng (0.4ppm) for Pyr. The LOD's for prepared solutions were 100 ng for B(a)P and 40 ng for Pyr. In validating the procedure we have also analyzed a standard mixture of PAH. The results of our analyses of the solid environmental samples agree well with those obtained by chromatography in other laboratories. We have found evidence of incomplete recovery of PAH from soil sediments by a prolonged low temperature Soxhlet extraction using methylene chloride.     

Rapid, sensitive and fully automated high-performance liquid chromatographic assay with fluorescence detection for sulmazole and metabolites

Sulmazole (2-[(2-methoxy-4-methylsulfinyl)phenyl]-3H-imidazo [4,5-b] pyridine; AR-L 115 BS) and two metabolites (sulfide, sulfone) were quantified from directly injected body fluids (plasma, urine, bile) after high-performance liquid chromatographic separation. No internal standard is needed, which is particularly advantageous when fluorescence detection is established. After automated pre-column enrichment on Corasil C18 (37-50 microns), the parent compound and biotransformation products could be backflushed and chromatographed on ODS-Hypersil (5 microns) with a mixture of 0.075 mol/l phosphate buffer-acetonitrile (2:1), an elution rate of 2.0 ml/min and fluorimetric detection (lambda ex = 330 nm; lambda em = 370 nm). A hydroxylated metabolite of sulmazole which occurs preferentially in urine (and bile) can be quantified in the above-mentioned solvent system diluted 1:1 with water, but with different fluorescence characteristics (lambda ex = 345 nm; lambda em = 515 nm). The assay was linear in the range 8-1000 ng/ml. The lower limit of detection was about 8 ng/ml or 80 pg with coefficients of variation between 0.4 and 5.8% for sulmazole.     

Fe3O4表面原位引发可控/“活性”聚合制备磁性聚苯乙烯纳米粒子

采用化学共沉淀方法合成了Fe3O4纳米粒子, 用3-甲基丙烯酰氧基丙基三甲氧基硅烷(3-MPS)对其进行表面接枝修饰, 然后以苯乙烯(St)为单体, 过氧化苯甲酰(BPO)为引发剂, 4-羟基-2,2,6,6-四甲基哌啶-1-氧化物自由基(HTEMPO·)为稳定自由基介质, 采用可控/“活性”自由基聚合技术在修饰后的Fe3O4纳米粒子表面原位引发聚合, 制备了粒径小、分布窄、磁含量高的磁性聚苯乙烯（PS）纳米粒子. X射线衍射(XRD)研究表明, 所合成的Fe3O4粒子为尖晶石结构. 凝胶渗透色谱(GPC)分析表明, 聚苯乙烯的分子量与反应时间呈较好的线性关系. 透射电镜(TEM)观察表明, 所制备的磁性聚苯乙烯纳米粒子的粒径在20-30 nm之间. 热重(TG)分析得到磁性聚苯乙烯纳米粒子的磁含量为62.6%. 振动样品磁强计(VSM)测试结果表明, 磁性聚苯乙烯纳米粒子的比饱和磁化强度为31.7 emu·g-1, 呈现单磁畴结构.     

Spectrophotometric Determination of Cystine with O-Phthalaldehyde in the Absence of Thiol

Abstract

A spectrophotometric method for the determination of cystine with o-phthalaldehyde (OPA) in the absence of thiol is described. When cystine is heated at 60[ddot]C for 30 min in a low excess of OPA (pH 9.5), a very stable derivative with 1:2 stoichiometry (cystine:OPA) and an absorption maximum at 335 nm (E = 4600) is formed. At pH < 1 the derivative is protonated (protonation constants: log K¹ = 5.88 and log K² = 3.70 at I = 0.1 and 20[ddot]C) and another absorption band at 440 nm (E = 3800) appears, which allows the determination of cystine in the presence of other amino acids.     

Multilayer vesicles and vesicle clusters formed by the fullerene-based surfactant C60(CH3)5K

The self-assembly behavior of a fullerene-based surfactant, C60(CH3)5K, in water was studied using a combination of static and dynamic light scattering, as well as transmission electron microscopy, and compared to that of the compound C60(C6H5)5K. Both fullerene surfactant systems spontaneously assemble into large vesicles consisting of closed spherical shells formed by bilayers, with critical aggregation concentrations (CAC) lower than 10(-6) g ml(-1). At low concentrations, the aggregate sizes of C60(CH3)5K (radius R approximately 26.8 nm) and C60(C6H5)5K (R approximately 17.0 nm) were found to be substantially different from each other, showing that the change of the substituents surrounding the polar cyclopentadienide head group makes it possible to control the size of the resulting aggregates. Furthermore, the C60(CH3)5K vesicles were found to exist in two qualitatively different types of aggregation with a critical reaggregation concentration (CRC) located at 3.30 x 10(-6) g ml(-1). Above the CRC, larger aggregates were observed (R approximately 37.6 nm), showing a more complex form of supramolecular aggregation, e.g., in terms of multi-bilayer vesicles and/or of clusters of bilayer vesicles.     

Simultaneous determination of beryllium and aluminium in mixtures using derivative spectrophotometry

The spectrophotometric determination of beryllium and aluminium with 5,8-dihydroxy-1,4-naphthoquinone in the presence of a non-ionic surfactant is reported. Absorption maxima, molar absorptivity and Sandell's Sensitivity of 1:2 (M:L) beryllium and aluminium complexes are, 585 nm and 598 nm, 1.63 x 10(4) l.mole(-1).cm(-1) and 2.04 x 10(4) l.mole(-1).cm(-1), and 0.55 ng/cm(2) and 1.32 ng/cm(2) respectively. Beer's law is obeyed between 7.20-3.96 x 10(2) ng/ml beryllium and 1.08 x 10(1)-1.08 x 10(3) ng/ml aluminium. A method for simultaneous determination of beryllium and aluminium in their mixture using derivative spectra is described. The range 3.6 x 10(1)-3.6 x 10(2) ng/ml beryllium could be determined in the presence of 1.08 x 10(2)-1.08 x 10(3) ng/ml aluminium, and vice versa.     

Interaction between anionic surfactants and oil dye in the aqueous solutions

The interactions between 4-phenylazo-1-naphthylamine and 6 sodium alkyl sulfates have been studied by a spectrophotometer. At lower concentrations than each CMC, 3 surfactants (octyl, decyl and dodecyl sulfate) and the dye formed hydrophobic complexes with a binding molar ratio of 11, while the others (tetradecyl, hexadecyl, and octadecyl sulfate) and the dye made 21 complexes. The wavelength of the maximal absorption is 440 nm in the former, and 520 nm in the latter. In the neighborhood of each CMC region, thermochromism occurred in every surfactant solution. The temperature at which the maximal absorption moved from 520 nm to 440 nm increased with an increase in the number of carbon atoms in the surfactant molecules. At higher concentrations than each CMC, in the case of the octyl and decyl sulfate, the maximal absorption occurred at the 440 nm band above room temperature; in the case of the dodecyl, tetradecyl, and hexadecyl sulfates, the maximal absorption occurred at the 520 nm band, regardless of temperature. In the case of octadecyl sulfate, the maximal absorption moved from 610 nm to 520 nm with increase in temperature. It is found that the protonation equilibrium of the dye is dependent on the micellar structure through the differences in the alkyl chain lengths of the surfactants, and the differences in interaction with surfactant crystals.