共查询到20条相似文献,搜索用时 46 毫秒
1.
A method is presented for determining optimal peak integration intervals on the basis of known peak shapes and noise characteristics. General theoretical considerations lead to conditions yielding optimal integration intervals. Examples of frequently occurring peak shapes and noise types are given, such as gaussian or skewed peak shapes, with band-limited first-order noise or flicker noise superimposed. The optimal integration intervals are approximately independent of the signal-to-noise ratio, and they are considerably smaller than the integration intervals normally used. The resulting expected peak area estimation errors are compared with the estimation error resulting from peak maximum amplitude measurement. On the basis of this comparison, rules of thumb are proposed to determine whether piak maximum measurement or peak integration yields the best results. Simulation of different peak shapes with noise superimposed confirms the results obtained. A flexible method is presented for the optimal measurement of the area of peaks with an unknown shape. This on-line method is simple, and could be used as a simple peak-finding procedure. The method requires almost no computer memory, and can be implemented on a microcomputer. A simulated example of this procedure is given. 相似文献
2.
The conventional approach to the measurement of peak capacity of reserved-phase columns under gradient elution assumes that all peaks have constant peak width, but this assumption can lead to inaccurate measurement of peak capacity. An integration approach employing a series of alkylphenones as model compounds was employed to more accurately measure the peak capacity for small molecule compounds under gradient elution. The base peak width of alkylphenones was plotted against retention time and a peak width function over retention time was established by polynomial regression. The peak capacity was then calculated by integrating the inverse of the peak width function over a gradient window. Compared to the conventional method, the integration method is not based on the assumption of equal peak width, thus providing a more accurate measurement of the peak capacity of reserved-phase columns, especially shorter ones packed with sub-2 μm particles under gradient elution. 相似文献
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A novel method for measuring the zeta potential of PDMS–electrolyte solution interface is presented in this paper. When an electrolyte solution passes the electrode coated with PDMS film, an electrical current will be induced due to the electrostatic potential difference between the PDMS–air interface and the PDMS–electrolyte solution interface. Based on this principle, the relationship between the measured electrical signal and the zeta potential of PDMS–electrolyte solution interface is experimentally investigated. The results show that the magnitude of the measured signal is linearly proportional to this potential difference. An empirical correlation between the zeta potential and the measured voltage signal was obtained. Good agreement was found when comparing the zeta potential calculated by this empirical equation with that reported in the published journal papers. The zeta potential measurement method presented in this paper is simple and accurate and can be used for measuring zeta potentials of other dielectric–electrolyte interfaces. 相似文献
5.
An optimised capillary electrophoresis-electrospray mass spectrometric method is presented for the identification and determination of diazepam and its metabolites N'-desmethyldiazepam, oxazepam and temazepam. By investigating constituent parts of the capillary electrophoresis-electrospray mass spectrometric interface and optimising their function, a relatively fast and reproducible method is described for the identification and determination of selected 1,4-benzodiazepines. Optimisation of sheath and auxiliary gas flows, capillary tip tapering, capillary tip positioning, sheath liquid composition and flow rate and pressure application during the separation step have led to acceptable relative standard deviation (RSD) values for migration time and peak area, correlation coefficients and limits of detection. This has been achieved as a result of stabilising the electrospray current prior to analysis, a procedure that takes a matter of minutes when using the method described. Sequential product ion fragmentation (MS(n)) characterisation of 15 1,4-benzodiazepines is also presented and mechanisms for the observed fragmentation patterns proposed. 相似文献
6.
Summary In this paper, we report and discuss the adsorption isotherms of hydro-organic mixtures and of compounds used as mobile phase
in reversed phase and normal phase high performance liquid chromatography (RP-HPLC and NP-HPLC, respectively). This work is
the first attempt to study the solid-liquid interface between two types of chromatographic silica surfaces and pure organic
adsorbates from water and from organic eluents by HPLC. Frequently, among the dynamic techniques the method of choice for
the measurement of an adsorption isotherm is frontal analysis. We suggest here the combination of the technique based on peak
asymmetry calibration and peak profiles, which allows calculations directly from integration data. The group of systems studied
permits the analysis of the intermolecular interactions on the silica surface. Particular attention was given to the system
methanol-water and the measurement of the adsorption ofn-octanol from methanol on RP-silica was also carried out. 相似文献
7.
A. Lodini 《Radiation Physics and Chemistry》2001,61(3-6):227-233
Neutron diffraction is a well-established non-destructive method for the measurement of residual stress deep inside materials. This paper gives a short overview of the use of neutrons for materials research and measurement techniques. Neutron diffraction has been applied in determining residual stresses in metal matrix composites. Measurement and prediction of residual stress for plastic deformation are presented. More recently, the neutron diffraction technique has also been applied for the determination of plastic strain which results from microstructural defects and leads to peak broadening. Influence of the shot penning treatment on austenitic steel is presented. 相似文献
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O. V. Zui 《Fresenius' Journal of Analytical Chemistry》1995,351(2-3):209-211
A highly sensitive, rapid and selective method is described for the determination of chloride in waters, based on oxidation by potassium permanganate in sulphuric acid medium, gas extraction of the chlorine formed and its chemiluminescence detection by luminol. The detection limit is 4 g/l, the time required for an analysis 4 min with peak height measurement and 8 min with peak area measurement. The method has been applied to the analysis of natural waters. 相似文献
10.
Vissers JP Blackburn RK Moseley MA 《Journal of the American Society for Mass Spectrometry》2002,13(7):760-771
A variable flow "peak trapping" liquid chromatography (LC) interface has been developed for the coupling of nanoscale LC to electrospray ionization mass spectrometry (ESI-MS). The presented peak trapping LC interface allows for the extended analysis time of co-eluting compounds and has been employed for the identification of proteins via tandem mass spectrometry (MS/MS). The variable flow process can be controlled either manually or in a completely automated manner where the mass spectrometer status determines the status of the variable flow interface. When the mass spectrometer operates in MS survey mode, the interface is operated in a so-called "high-flow" mode. Alternatively, the interface is operated in a "low-flow" mode during MS/MS analysis. In the "high-flow" mode of the variable flow process the column flow rate is typically around 200 nL/min, whereas in the "low-flow" mode the column effluent is introduced into the source of the mass spectrometer at 25 nL/min. In addition to the flow reduction during MS/MS analysis, the gradient is paused to preserve the peptide separation on the analytical nanoscale LC column. The performance of the variable flow nanoscale LC/MS/MS interface is demonstrated by the automated analysis of standard peptide mixtures and protein digests utilizing variable flow, data-dependent scanning MS/MS techniques, and automated database searching. 相似文献
11.
A novel method of interfacing the acoustic flame detector (AFD) with modified supercritical fluid chromatography (SFC) is presented. By applying resistive heating directly to the burner region between the restrictor outlet and the acoustic flame, infrequent severe noise, baseline drifting, and peak deformations that can occasionally be observed with the AFD are eliminated. For example, by increasing the interface temperature only a few hundred degrees Celsius, such sporadic noise in the detector can be reduced nearly ten-fold resulting in smooth stable operation of the AFD. Further, for various levels of methanol modified supercritical carbon dioxide mobile phase examined, the interface was observed to reduce detector noise in each to a common minimal range near 10-25 Hz when an appropriate temperature was achieved. The method is simply assembled, inexpensive to construct, and robust in its daily operation. Overall, the heated interface developed and presented facilitates reliable AFD operation in modified SFC, and supports further exploration and implementation of this sensor as an alternative universal detector in separations requiring an organic cosolvent in the mobile phase. 相似文献
12.
Thermodynamics‐based models have been demonstrated to be useful for predicting retention time and peak widths in gas chromatography and two‐dimensional gas chromatography separations. However, the collection of data to train the models can be time consuming, which lessens the practical utility of the method. In this contribution, a method for obtaining thermodynamic‐based data to predict peak widths in temperature‐programmed gas chromatography is presented. Experimental work to collect data for peak width prediction is identical to that required to collect data for retention time prediction using approaches that we have presented previously. Using this combined approach, chromatograms including retention times and peak widths are predicted with very high accuracy. Typical errors in retention time are < 0.5%, while errors in peak width are typically < 5% as demonstrated using polycycic aromatic hydrocarbons and a mixture containing compounds with aldehyde, ketone, alkene, alkane, alcohol, and ester functionalities. 相似文献
13.
Santiago Codesido Nicolas Drouin Sabrina Ferré Julie Schappler Serge Rudaz Víctor González-Ruiz 《Electrophoresis》2021,42(19):1875-1884
CE–MS is increasingly gaining momentum as an analytical tool in metabolomics, due to its ability to obtain information about the most polar elements in biological samples. This has been helped by improvements of robustness in peak identification by means of mobility-scale representations of the electropherograms (mobilograms). As a necessary step toward facilitating the use of CE–MS for untargeted metabolomics data, the authors previously developed and introduced ROMANCE, a software automating mobilogram generation for large untargeted datasets through a simple and self-contained user interface. Herein, we introduce a new version of ROMANCE including new features such as compatibility with other types of data (targeted MS data and 2D UV-Vis absorption-like electropherograms), and the much needed additional flexibility in the transformation parameters (including field ramping and the use of secondary markers), more measurement conditions (depending on detection and integration modes), and most importantly tackling the issue of quantitative peak conversion. First, we present a review of the current theoretical framework with regard to peak characterization, and we develop new formulas for multiple marker peak area corrections, for anticipating peak position precision, and for assessing peak shape distortion. Then, the new version of the software is presented and validated experimentally. We contrast the multiple marker mobility transformations with previous results, finding increased peak position precision, and finally we showcase an application to actual untargeted metabolomics data. 相似文献
14.
Peters S Vivó-Truyols G Marriott PJ Schoenmakers PJ 《Journal of chromatography. A》2007,1146(2):232-241
A new resolution metric for two-dimensional chromatography is proposed and tested. This resolution measurement is based on the concept of the (one-dimensional) valley-to-peak ratio, which has been adapted and modified for two-dimensional chromatography. Two questions are considered related to the computation of the resolution of a given (two-dimensional) peak. First, the concept of peak neighbourhood is revised, since it changes drastically from one- to two-dimensional chromatography. In a chromatogram resulting from a two-dimensional analysis, one peak may be surrounded by more than two neighbouring peaks. However, the neighbouring peaks can be remote from the peak or some interfering peaks may be in between. In these cases, it is not meaningful to compute the resolution between them. A method is proposed to determine whether a resolution measurement between two two-dimensional peaks is reasonable. Second, a measurement of the valley-to-peak ratio in two-dimensional chromatography is proposed. The measurement is based on the concept of the saddle point (which is defined for two-dimensional surface plots). A study of the correlation of the valley-to-peak ratio with the error obtained for quantification is presented. The new metric can be used as an estimator of the quantification errors. Also, valley-to-peak ratios can be calculated for one or more target peak(s) to estimate the separation quality of the entire chromatogram. This makes the proposed measurement suitable for optimisation purposes. Although the algorithm was developed for GC x GC, preliminary studies suggested that its application to other two-dimensional separation methods (e.g. LC x LC) should only require minor modification (if any). 相似文献
15.
Ute Bergmann Sabine Apelt Nasrin B. Khojasteh René Heller 《Surface and interface analysis : SIA》2020,52(12):1111-1116
A novel Rutherford backscattering spectrometry (RBS) method is presented to investigate the interface between a solid surface and a surrounding liquid. The introduced measurement system allows to observe and quantify adsorption at the solid–liquid interface and the formation of the electrochemical double layer (EDL). BaCl2 as a bicomponent electrolyte and a Si3N4 membrane surface are chosen as a model system to prove the capabilities of the setup. The results of these RBS measurements are combined with electrochemical impedance spectroscopy (EIS) to validate the findings for the solid–liquid interface under study. Complementary results and discrepancies regarding the formation of the EDL are discussed. 相似文献
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《Electrophoresis》2018,39(14):1754-1762
A novel and fully automated sequential injection analysis manifold coupled to a capillary electrophoresis apparatus with amperometric detection, is described. The sequential injection manifold was isolated from the high voltage by inserting an air plug into the circuit. Small buffer reservoirs were used to avoid the need to pump fresh buffer to the interface during the electrophoretic separation. No decoupling device was used to mitigate the interference from the high voltage electric field, instead the potential shift induced by the separation voltage, was accounted for. The new hydrodynamic injection method presented is based on the overpressure created in the circuit when a pinch valve is closed for a predetermined time. The injection method yields RSD values of peak height and area below 2.55 and 1.82%, respectively, at different durations of valve closure (n = 5). The capillary and working electrode alignment was achieved by adapting a commercial available capillary union. When the electrode was replaced, the alignment method proved to be very reliable, yielding RSD values of peak height and area lower than 2.64 and 2.08%, respectively (n = 8). Using this system with a gold microelectrode, dopamine, and epinephrine could be quantified within the concentration range of 1–500 μM and detected at a concentration of 0.3 μM. The methods here presented could be applied for the development of new capillary electrophoresis systems with amperometric detection and/or to the design of fully automated systems for online process monitoring purposes. 相似文献
18.
The identification of toxic oligopeptides employing CE-ESI-MS is presented. The analytes studied ama- and phallotoxins are of significant forensic interest because over 90% of the lethal cases of fungus poisoning in man are caused by species of Amanita which contain these toxins. A CE method was developed to separate the toxins alpha-, beta- and gamma-amanitin, phalloidin and phallacidin. Their fragmentation patterns in MS(n) experiments were investigated in the positive and in the negative ion mode, also the influence of the sheath liquid mixture of the used interface on the S/N. Method validation included the determination of the LOD and the repeatability of the migration time and peak area for both detection modes. With the optimized method LODs of 13-79 ng/mL (17-87 nmol/L) were reached. The CE-MS procedure was successfully applied to the identification of ama- and phallotoxins in extracts of air-dried mushroom samples. 相似文献
19.
Quantitative Detection for Porphyromonas gingivalis in Tooth Pocket and Saliva by Portable Electrochemical DNA Sensor Linked with PCR 下载免费PDF全文
Keiichiro Yamanaka Shinichi Sekine Takahiro Uenoyama Masahiro Wada Tomohiko Ikeuchi Masato Saito Yoshinori Yamaguchi Eiichi Tamiya 《Electroanalysis》2014,26(12):2686-2692
Here, a quantitative electrochemical analysis of periodontal bacteria in gingival crevicular fluid (GCF) and saliva by direct polymerase chain reaction (PCR) is presented. The electrochemical measurement was performed by mixing with PCR products and electrochemical indicator (bisbenzimidazole trihydrochloride). The peak current of indicator is reduced due to slower diffusion when the dye intercalates into the amplified DNA, and the degree of reduction in the peak current is correlates with the quantity of amplified DNA. Therefore, a quantitative analysis is possible by using our electrochemical method at the end point of PCR. In the GCF testing, The number of Porphyromonas gingivalis (Pg) detected by our electrochemical method at the end point of PCR were almost same compared with that were calculated by the conventional method of quantitative real? time PCR. In the saliva testing, the relationship between number of Pg in saliva and average pocket depth, and age‐dependence were also clearly observed. Since the saliva sample is obtained in a non‐invasive manner, this method is useful for the primary screening of periodontal disease. Moreover, our detection method is simple and uses a hand‐held potentiostat making it suitable for development of an on‐site periodontal diagnosis system. 相似文献
20.
Wan H Ostlund A Jönsson S Lindberg W 《Rapid communications in mass spectrometry : RCM》2005,19(12):1603-1610
A novel drug-protein binding measurement method based on high-performance frontal analysis and capillary electrophoresis (HPFA/CE) is presented. A single run measurement approach is proposed to circumvent utilization of a calibration curve that is often performed with HPFA. A sensitive mass spectrometer is applied as a detector enabling the measurement of in vitro protein binding at lower drug concentrations. Unbound free fraction and binding constants can be determined by a single run measurement by consecutive injections of an internal drug standard, a buffer plug and a drug-protein mixture. Effects of injection volumes on peak height and plateau profile were investigated in two different separation systems, non-volatile buffer and volatile buffer, with UV and mass spectrometry detection, respectively. A simplified one-to-one binding model is employed to evaluate the proposed method by using both single and multiple drug concentrations to measure the unbound free fraction and calculate the binding constants of some selected compounds. The method is suitable for rapid and direct screening of the binding of a drug to a specific protein or drug-plasma protein binding. 相似文献