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31.
Summary After a brief introduction of the subject, the paper focusses on the first step in any optimization procedure: the delineation
of the parameter space, wherein the global optimum is to be found. For organic modifier optimization in reversed-phase liquid
chromatography it is shown that the necessary information can be derived from a single water-methanol gradient. It first yields
an estimate of the total number of solutes in the sample, which is vital to define the peak capacity needed to achieve separation
at a certain confidence level. Next, the gradient allows the prediction of suitable isocratic methanol binary solvents, and
transfer rules formulate the iso-eluotropic composition of the common binary solvents (tetrahydrofuran and acetonitrile).
Because all predictions are based on a statistical analysis of a limited data base, attention is given to the practical situation
where an actual sample deviates from the average solute behaviour. Such deviations are revealed in the first isocratic run
and can be used to arrive at a better estimate of solute retention. 相似文献
32.
Summary A rapid and simple method for the determination of both lysinoalanine (LAL) and protein hydrolysate amino acids after derivatization
with dansyl chloride (5-dimethylaminoaphtalene-1sulfonyl chloride) and separation with RP-HPLC (UV detection) is presented.
LAL is analysed in less than 15 minutes and complete separation of 22 amino acids is achieved in less than 30 minutes using
single linear gradients of solvents (phosphate buffer and acetonitrile). Quantitative results obtained by HPLC compare well
with results of the ion-exchange chromatography (amino acid analyser). The importance of the duration of the derivatization
reaction and of the excess of reagent is discussed. As examples, the results of the determination of LAL in two samples of
base treated α-casein and 22 samples of soy protein and the results of the analysis of amino acids in two balanced diet mixtures
are presented.
Presented at the 15th International Symposium on Chromatography, Nürnberg, October 1984 相似文献
33.
Intercrystalline migration and a migration-assisted chemical reaction of adsorbed aromatic species between zeolite particles in physical contact were visualized by fluorescence microscopy coupled with a particle manipulation technique. The luminescence color characteristics of particular zeolite particles originating from the specific photochemistry of adsorbed species was exploited to follow the migration of the molecules. Two examples are shown that are relevant to the visualization of the time-dependent migration process: A one guest-two sets of zeolite crystals system: chrysene (Chry)-loaded zeolite Na+ -X (the sodium form of zeolite X) crystals were placed in contact with unloaded Tl+ -X (thallium-exchanged X) crystals and allowed to stand at room temperature. Initially, the blue fluorescence of Chry was detected only from the Na+ -X particles, but later, the development of green phosphorescence emission was discernible from the Tl+ -X which suggests that Chry migrated from the Na+ -X to the Tl+ -X crystals. A two guest-species systems: Electron-donating Chry-loaded Na+ -X crystals were placed in contact with electron-accepting 1,2,4,5-tetracyanobenzene (TCNB)-loaded Na+ -X or Na+ -Y crystals. With time, the former system (Chry/Na+ -X and TCNB/Na+ -X) gave rise to the emission of Chry-TCNB charge-transfer complexes resulting mainly from the migration of Chry while the latter system (Chry/Na+ -X and TCNB/Na+ -Y) afforded the same emission resulting largely from the migration of TCNB. The present investigation reveals that there is a certain direction for guest migration depending on the zeolite host and the nature of host-guest or guest-guest interaction. 相似文献
34.
Raman spectroscopy was applied for the direct non-destructive analysis of amiodarone hydrochloride (ADH), the active ingredient of the liquid formulation Angoron®. The FT-Raman spectra were obtained through the un-broken as-received ampoules of Angoron®. Using the most intense vibration of the active pharmaceutical ingredient (API) at 1568 cm−1, a calibration model, based on solutions with known concentrations, was developed. The model was applied to the Raman spectra recorded from three as-purchased commercial formulations of Angoron® having nominal strength of 50 mg ml−1 ADH. The average value of the API in these samples was found to be 48.56 ± 0.64 mg ml−1 while the detection limit of the proposed technique was found to be 2.11 mg ml−1. The results were compared to those obtained from the application of HPLC using the methodology described in the European Pharmacopoeia and found to be in excellent agreement. The proposed analytical methodology was also validated by evaluating the linearity of the calibration line as well as its accuracy and precision. The main advantage of Raman spectroscopy over HPLC method during routine analysis is that it is considerably faster and no solvent consuming. Furthermore, Raman spectroscopy is non-destructive for the sample. However, the detection limit for Raman spectroscopy is much higher than the corresponding for the HPLC methodology. 相似文献
35.
James V. Beitz C.W. Williams K.-S. Hong G.K. Liu 《Journal of solid state chemistry》2005,178(2):511-520
We have assessed the feasibility of carrying out time- and wavelength-resolved laser-induced fluorescence measurements of radiation damage in glassy silica. The consequences of alpha decay of Es-253 in LaPO4 nanophases embedded in silica were probed based on excitation of 5f states of Cm3+, Bk3+, and Es3+ ions. The recorded emission spectra and luminescence decays showed that alpha decay of Es-253 ejected Bk-249 decay daughter ions into the surrounding silica and created radiation damage within the LaPO4 nanophases. This conclusion is consistent with predictions of an ion transport code commonly used to model ion implantation. Luminescence from the 6D7/2 state of Cm3+was used as an internal standard. Ion-ion energy transfer dominated the dynamics of the observed emitting 5f states and strongly influenced the intensity of observed spectra. In appropriate sample materials, laser-induced fluorescence provides a powerful method for fundamental investigation of alpha-induced radiation damage in silica. 相似文献
36.
Hong Zheng Xiao-Lan ChenMing-Hui Hu Dong-Hui LiJin-Gou Xu 《Analytica chimica acta》2002,461(2):235-242
A new method based on near-infrared (near-IR) fluorescence recovery, employing a two-reagent system which is composed of an anionic heptamethylene cyanine (HMC) and a polycationic phthalocyanine dye, Alcian blue 8GX, is presented for the determination of nucleic acids. With a maximum excitation wavelength at 766 nm and a maximum emission wavelength at 796 nm, the fluorescence recovery is linear with the concentration of nucleic acids added. Factors including the acidity of the medium, the reaction time, the optimal ratio of the two reagents, as well as the influence of foreign substance were all investigated. Meanwhile, the mechanism of fluorescence recovery was also studied. Under the optimal conditions, the linear ranges of the calibration curves were 10-250 ng ml−1 for calf thymus DNA (CT DNA) and 10-200 ng ml−1 for yeast RNA. The detection limits were 6.8 ng ml−1 for CT DNA and 6.3 ng ml−1 for yeast RNA, respectively. The method has been applied to the analysis of practical samples and the recovery results were satisfactory. 相似文献
37.
Soran Loredana Coman Virginia Soran Albert Silvestru Cristian 《Central European Journal of Chemistry》2004,2(4):563-572
2-(Diethylaminomethyl)phenyl bromide and 1,3-bis(dimethylaminomethyl)-benzene, useful ligands for the synthesis of hypervalent
organometallic compounds, were prepared and characterized by NMR (1H, 13C, 2D experiments) spectroscopy. Their synthesis was monitored by the HPLC method. The compounds were eluted on a Nucleosil
120 Si column (5 μm, 25×0.4 cm) with n-hexane at room temperature using a 1.0 ml/min flow-rate. The maximum values of absorbance for the studied compounds, excepting
the diethylamine, were located in a narrow range around 212 nm, the wavelength used for their UV detection. The diethylamine
was detected at 190 nm. The calibration curves are straight lines with correlation factors r>0.995. The HPLC data are in good
agreement with those provided by NMR spectroscopy. 相似文献
38.
Petra A W Van Den Berg Koert Grever Arie Van Hoek Willem J H Van Berkel Antonie J W G Visser 《Journal of Chemical Sciences》2007,119(2):123-133
Conformational heterogeneity of the FAD cofactor in p-hydroxybenzoate hydroxylase (PHBH) was investigated with time-resolved polarized flavin fluorescence. For binary enzyme/substrate
(analogue) complexes of wild-type PHBH and Tyr222 mutants, crystallographic studies have revealed two distinct flavin conformations;
the ‘in’ conformation with the isoalloxazine ring located in the active site, and the ‘out’ conformation with the isoalloxazine
ring disposed towards the protein surface. Fluorescence-lifetime analysis of these complexes revealed similar lifetime distributions
for the ‘in’ and ‘out’ conformations. The reason for this is twofold. First, the active site of PHBH contains various potential
fluorescence-quenching sites close to the flavin. Fluorescence analysis of uncomplexed PHBH Y222V and Y222A showed that Tyr222
is responsible for picosecond fluorescence quenching free enzyme. In addition, other potential quenching sites, including
a tryptophan and two tyrosines involved in substrate binding, are located nearby. Since the shortest distance between these
quenching sites and the isoalloxazine ring differs only little on average, these aromatic residues are likely to contribute
to fluorescence quenching. Second, the effect of flavin conformation on the fluorescence lifetime distribution is blurred
by binding of the aromatic substrates: saturation with aromatic substrates induces highly efficient fluorescence quenching.
The flavin conformation is therefore only reflected in the small relative contributions of the longer lifetimes. 相似文献
39.
A. Manjon J. A. Ferragut J. C. Garcia-Borron J. L. Iborra 《Applied biochemistry and biotechnology》1984,9(2):173-185
Fluorescence spectra and soluble quenching of intrinsic protein fluorescence were used as indexes of conformational changes
suffered by frog epidermis tyrosinase. The activation process and the immobilization of the enzyme involving either free amino
groups or its carbohydrate moiety were studied. The conformational changes resulting from denaturation of each one of the
protein derivatives, as well as the effect of active center copper extraction, were followed by fluorescence studies.
The results showed that: (a) both activation and immobilization were accompanied by conformational changes of the protein
leading to more unfolded states; (b) neither enzyme nor immobilized enzyme were fully unfolded upon denaturation although
enzymic activity was lost; (c) the enzyme immobilized through its carbohydrate moiety was more unfolded upon denaturation
than the enzyme immobilized through amino groups, thus pointing to a higher conformational stabilization in the last situation;
and (d), that tryptophyl residues moved to a localization near the active site upon activation. 相似文献
40.
自然界中砷和砷的化合物一般可通过水、大气和食物等途径进入人体,危害人体健康,原子荧光光谱法测定砷含量被广泛应用。为准确测定样品中砷的含量,以原子荧光光谱法(AFS)测定土壤中总砷含量为例,重点研究高价态砷(Ⅴ)还原为低价态砷(Ⅲ)的实验条件,采用正交实验进行条件优化,建立适合的实验方法。通过设计L9(34)正交实验,高价态砷的还原反应与四个因素有关,即与反应温度、反应时间、盐酸加入量和硫脲的用量呈一定的正相关,结果表明,四个因素中硫脲用量的影响最为显著,其次是盐酸加入量、反应时间和反应温度。通过对四个因素的多水平检验,优化后的实验条件为:硫脲用量2.0 mL、盐酸加入量10%、反应时间20 min、温度20~35 ℃(即普通室温)。采用土壤标准物质验证优化后条件的可行性,得出砷的测定值在标准值范围内,RSD在2.2%~4.2%,精密度和准确性均满足质控要求。优化后的实验条件使得操作简便易行,提高了工作效率。 相似文献