High mass sensitive

It is seen that with 1 ml samples the peak for a concentration of 1 ppm is well off scale and a clearly defined peak was observed for 10 ppb. When a 10 ml sample was used, acetophenone at a concentration of 1 ppb could just be detected. Under the conditions used, the ultimate mass sensitivity of the system was about 10 ng. This level of sensitivity was achieved, on the one hand, by the sample concentrating process, and on the other, as a result of the high mass sensitivity of small bore columns. 

It is seen that there are a large number of compounds capable of dispersive interactions with the reverse phase, contained in the serum that have been extracted and separated. Again the results have been obtained, partly as a result of the extraction and concentration properties of the sampling system, and partly as a result of the high mass sensitivity of the small bore columns. 

High mass sensitivity, significantly better than with LC... 

The quality of an analytical separation technique is not only characterized by its separation efficiency but also by its detection sensitivity. UV-VIS spectrophotometry and fluorescence are commonly used simple detection methods for CEC. However, not all compounds absorb UV light and even fewer compounds fluoresce. Although high mass sensitivity can be achieved, the concentration sensitivity in CEC is generally poor since short optical path lengths that equal the internal diameter of the capillary are used. Dittmann et al. [55] discussed thoroughly the limits of sensitivity in CEC detection. 

The main peculiarities of modem CE are great analytical versatility, high separation efficiency, high mass sensitivity, extremely low demands on sample volumes, short analysis times (usually < 30 min), minimum consumption of solvents (running buffer) and other consumables (e.g., capillaries), possibility of interfacing with different detection systems (including mass spectrometry), and simplicity of the basic instrumentation. 

The high mass sensitivity calculated in the previous example justifies the term microbalance in describing the sensing capabilities of the quartz resonator. Equation 3.9 can be used to calculate fr uency shifts for surface accumulations that behave as ideal mass layers. A real film behaves as an ideal mass layer if it is sufficiently thin and rigid so that it moves synchronously with the oscillating device surface. On a TSM resonator, this condition is realized if the acoustic phase shift across the film is small, i.e., ir. The phase shift is... 

The high mass sensitivity of ETSM sensors renders them particularly suited for the analysis of monolayer and submonolayer films. In fact, the earliest applications of the ETSM involved studying the electrochemical deposition of monolayers, including the formation of metal oxides [207], electrosorption of halides [208], and the underpotential deposition of metal atoms [209-213]. In some cases, the electrovalency (i.e., the ratio of moles of electrons transferred at the electrode to moles of adsorbate deposited) was found to vary with adsorbing species the adsorption of iodide onto gold, for example, occurs with complete charge transfer from the halide to the electrode, whereas the adsorption of bro-... 

In recent years, CE has been successfully applied in the field of biochemical and analytical chemistry. It has been found to be attractive for pharmaceutical analysis because of its advantages related to excellent separation efficiency, high mass sensitivity, minimal use of samples and solvents, and the possibility of using different direct and indirect detection systems. This review focuses on analytical assays for barbiturates by CE. 

As advantages, capillary separation techniques demonstrate high separation efficiency. On occasion, the number of theoretical plates available from these approaches has exceeded 1 million [29]. Also, very small sample volumes, on the order of 100 to 0.5 nL, are needed for these techniques. This can be an advantage for sample-limited situations, which are often encountered in bioanalysis. High mass sensitivity (the absolute weight of analyte injected) can be achieved, as the narrow capillary concentrates the sample plug and allows less opportunity for band broadening. 

Capillarycoil probe that with a receiver coil that is 10-100 times smaller than that of the conventional probe. High mass sensitivity Less sample and solvent consumption... 

Strength and the sample concentration, po is the permeability of free space, Q is the quality factor of the coil, coo is the Larmor angular frequency, K is the volume of the coil, F is the noise figure of the preamplifier, k is Boltzmann s constant, is the probe (as opposed to sample) temperature, and A/is the bandwidth (in Hz) of the receiver. It can be seen that the concentration sensitivity 5c (SIN per pM concentration of analyte) is poor for microcoils. This is due to the fact that microcoil probes have very small observation volumes and therefore contain a very small amount of analyte. However, if the sample can be concentrated into a small volume, then the microcoil can more easily detect the signal. This high mass sensitivity 5m (SIN per pmol of analyte) is characteristic of microcoil NMR probes. In essence, the use of microcoil probes enhances the mass sensitivity 5m at the expense of the concentration sensitivity 5c. To better understand the relationship between sensitivity and coil diameter, a detailed analysis was reported by Peck et Their results showed that mass sensitivity increases monotonically with decreasing coil diameter within the 1mm to 50 pm range they studied. However, the concentration sensitivity decreases, and therefore there is a trade-off between Sc and 5m that depends on coil diameter. 

Procedures for the production of large quantities of fused silica capillaries were developed to fill the growing demand for capillary gas chromatography columns. The advent of laser induced fluorescence (LIF) and electrochemical (EC) detectors provided the high mass sensitivity necessary for detection in nanoliter volumes. Jorgenson and Lucas published several key papers on modern CE in 1981. Since then CE has experienced exponential growth to the point where there are well over 2000 articles published annually involving CE. 

Nowadays, most HPLC separations are performed on conventional analytical columns, 10-25 cm long, 3-4.6 mm in diameter, and packed with 3-10 pm uniform particles (recently even with 1-2 pm size). With short high-speed columns, 1.5-5 cm long, simple separations can be accomplished in 1-3 min, with significantly reduced analysis time and solvent consumption. Separations on microbore columns, 15-25 cm long and 1-2 mm ID, need even less mobile phase and allow detection of high mass sensitivity. These columns are useful for analyses of small... 

In addition to UV detection, two other more sensitive and selective detection systems have attracted attention for the analysis of drugs and metabolites in biological samples laser-induced fluorescence (LIF) and mass spectrometry (MS). A powerful detection system is that which is based on LIF. The LIF detection provides extremely high mass sensitivity, but it is only applicable to some analytes that absorb in the 325 nm (helium-cadmium) or 488 nm (argon) region, as lasers are only commercially available for these wavelengths. Derivatization with fluorescent tags is an alternative for non-fluorescent species. "- ... 

An examination of equation (14.24) reveals that the change in velocity is proportional to mass per unit area. Zip, and this relationship provides the theoretical basis of mass response for SAW devices. It should also be noted that velocity change is a function of the frequency of operation, o. As a consequence, the sensitivity of mass response of an SAW device increases with frequency. Since SAW devices operating at frequencies higher than 1 GHz are possible, extremely high mass sensitivities can be achieved. 

CE-LIF Rapid analysis allowing for temporal resolution on the order of seconds High mass sensitivity Off- and on-line analysis, with the latter increasing temporal resolution 3 sec—5 min 0.06-85 nM [131-133,138]... 

A typical schematic diagram of a QCM is shown in Figure 6. It consists of a polymer-coated quartz crystal and a pair of electrodes. QCM sensors are widely used for the characterization of thin layers, fluids, and gases due to their high mass sensitivity and diuabiUty. Hie sensing principle relies on the fact that changes in the mass of the polymer due to analyte... 

---