Offline analysis

Shortly afterwards, this work was extended by the incorporation of a mass spectrometer into the system, thus enabling on-line NMR and MS data to be obtained with on-line collection of the eluent for off-line FT-IR spectroscopy [22]. The incorporation of the mass spectrometer required the addition of a small proportion of ammonium acetate, dissolved in methanol, to the deuterated chloroform used as the eluent in order to promote the ionisation of the analytes. The inclusion of methanol and ammonium acetate to the solvent obviously introduced new signals into the NMR spectra, and in addition resulted in the loss of exchangeable protons from the analytes which had been observable when chloroform alone was used as the solvent. This work demonstrated the feasibility of multiple hyphenation ( hypernation ) but the off-line nature of the FT-IR data acquisition, with the inevitable delay inherent in offline analysis, represents a slight disadvantage. In addition, volatile components may well be lost as the solvent is evaporated. This can be a problem that, together with analyte instability, is exacerbated with such interfaces when reversed-phase eluents are used since these require heating in order to ensure removal of the solvent. 

At last, the double focusing sector field mass spectrometer (EBQjQ2) should briefly be addressed. This mass analyser represents a highly sophisticated early design that has rarely been used for routine analysis especially for quantification. For detailed information on the functional principle the reader is referred to respective textbooks on mass spectrometry. We mention this technique as Kajbaf et al. used EBQjQ2 for detection and identification of the QTA cimetropium and its biotransformation products from liver microsomal mixtures in offline analysis of HPLC fractions after FAB ionization [23, 62] (Table 7). 

A group of scientists from Peking University [44,45] proposed conducting CE-IA in a thermally reversible hydrogel added to the buffer as a replaceable packing material. Antibodies were immobilized in the gel and a mixture of tracer and analyte was injected. The presence of gel enhanced the peak shapes and resolution, whereas immobilized antibody suppressed dissociation during the CE run. The latter makes this assay a kind of a mixture between on-line and offline analysis modes. 

More success was obtained using on-line solid phase extraction before offline analysis by capillary electrophoresis with matrix-assisted laser-desorption ionization (MALDI) MS [18]. Because microdialysis is a method used for analysis of small molecules and peptides, MALDI is not used frequently with microdia lysis sampling. Another disadvantage is that MALDI cannot be used on-line with the separation because it is a vacuum ionization technique. However, if the pep-tide is large enough (0 1000 Da) MALDI can be useful. For the analysis of peptides in dialysate an appropriate separation is important before mass spectrometric detection. In a comparison with direct sampling of dialysate in MALDI, capillary electrophoresis provides the high efficiency separations necessary to resolve all... 

For many operations measuring on-line is a preferred choice rather than waiting for the offline analysis in a laboratory. At present, the U. S. EPA has not usually allowed on-line methods to be used for fuel products certification. Many on-line methods are extensions of well-established test methods such as D 2622, D 4045, D 4294, D 5453, etc., while others were developed for on-line analysis only. Some of the known on-line methods based on vendor supplied information are given below. This is not intended as a complete list of such available technology. 

Realisation of the first approach - trapping and offline analysis - employs a miniature gas-sampling tube packed with a mixture of Tenax (molecular sieve) and Carbopak (activated charcoal) absorbent material. Such tubes are routinely used for environmental monitoring of hazardous industrial atmospheres whereby operators during the normal course of their duties carry a small tube (about the size of a pen) clipped to their clothes. A pump may be used to draw gas through the tube at a controlled rate and, at the end of the work period, the tube is sealed and sent for analysis. Heating the sorbent tube drives off the trapped material into a gas chromatograph for separation and quantification. 

According to (Cornell University 2008), the WSNs currently deployed are pre-programmed to send data to a central storage unit where they are available for consultation and offline analysis. This approach has at least two major inconveniences. The first is the inability to enable the user to dynamically change the system behavior. The second is that communication is... 

Electrospray appears to be useful especially when dealing with compounds that give poor APCI spectra due to thermal degradation (such as glucuronide conjugates). Meanwhile, electrospray and its derivative, nanoflow electrospray , have developed a niche in the analysis of proteins. They are especially useful as an ionization method combined with capillary electrophoresis, and for offline analysis of spots retrieved from chromatographic plates. 

Figure 1 (A) Steps involved in offline analysis. Time between sampling and a control decision being made can be days. (B) Steps involved in online analysis. Results obtained in seconds or minutes.

Sample system training The technicians should be familiar with the entire sample transportation and conditioning system. Several key questions should be asked Where does the sample come from and return Under what specific operating parameters, such as temperature, pressure, flow rate, should the sample system be operated How to monitor the system performance and how to isolate the sample system from process for offline service How to safely take a representative sample for offline analysis With a QA program and use of the statistical process control, the technicians should be trained to determine when to service the sample system, such as water wash to clear the sample line and when to replace some parts, such as a dirty Alter. 

The offline analysis of selected metabolites of the cells during a bioprocess can be performed by MS, NMR spectroscopy, or chromatographic separation procedures. The NMR technique is based on the specific response of atomic nuclei that are exposed to a magnetic field. This technique is able to resolve the structures of small biomolecules and thus to determine selected metabolites during a bioprocess or for metabolic flux analyses. Advanced MS techniques allow a high throughput analysis of complex mixtures of metabolites by the determination of the specific masses of the metabolites. 

The expression analysis by means of optical DNA chips is only useful for an offline analysis of selected critical bioprocess-relevant genes. The analysis time for the mRNA by these approaches from early cell disruption and RNA isolation to final data analysis lasts several hours. Alternative shorter and less labor-intensive techniques have been suggested and are... 

High selectivity of MS for the samples directly analyzed from the plate, without the need for extracting compounds from TLC and offline analysis. 

Table 6.2 Selection criteria for the reconstructed global muons in the offline analysis...

Although the simulation program Promaps was designed for offline analysis, it was early recognized that the concept also was suitable for online analysis. In 2009 an agreement between Goodtech Projects Services and Statnett SF in Norway... 

Data acquisition functions enable the system to deal with both online R MM and offline analysis by means of either selecting dynamic monitoring outputs or choosing existing historical database, respectively. 

The ProCompH- system samples both EGG and EMG at 32 samples per second, which is sufficient for both HRV and EMG power analysis. Our software logged the physiological data with a time stamp for offline analysis. The computer system used a 2.0 GHz Pentium 4 processor, running a Debian Linux operating system. 

Condition (i) is satisfied in implementations that provide immediate or eventual progress. In the limited progress model, condition (i) needs to be satisfied by complementing the implementation with offline analysis. 

The executors and the underlying runtime guarantee progress as defined in section 3, and if only limited progress is available, offline analysis is able to determine the minimum number of executors required for each task. 

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