Delayed extraction advantages

State-of-the-art ToF-MS employs reflection lenses and delayed extraction [176] to improve resolution by minimising small differences in ion energies, and in these cases up to 12000 mass resolution (FWHM, m/z 600) is available. This is sufficient for most modern applications. Solid probe ToF-MS (or direct inlet high-resolution mass spectrometry, DI-HRMS) is a breakthrough. DIP-ToFMS is a thermal separation technique. Advantages of DIP-ToFMS are ... 

Other types of mass spectrometer have been used to record MALDI spectra magnetic sector instruments equipped with an array detector initially offered the advantage of higher resolution than was available with the early linear TOF instruments but these spectrometers have now largely been replaced with reflectron-TOF instruments using delayed extraction ion sources. Mass spectrometers operated with higher than normal ion source pressures to... 

This is a more realistic response than case 1 because it allows for a time delay as well as first-order behavior, and can be applied to many chemical processes. The delay time may not be clearly identified as transport lag but may be imbedded in higher order dynamics. Hence, this is an approximate but very useful model, especially for staged systems such as distillation or extraction columns. An extension of this model is second order plus time-delay, the response of which is equivalent to case 2 or case 4 with an initial time delay. The advantage over first-order models is that an additional model parameter can give greater accuracy in fitting process data. 

In the amplifier per wire method the pulses on the orthogonal cathode planes are extracted independently from each wire and the centroid position in x and y is thereby determined. The main advantage of this system is a higher count rate capacity ( 106s 1) compared with use of delay lines ( =105s 1). This method is used by Kahn et al (1982b) at LURE for example. 

The original aqueous phase remaining after the extraction with ether is made alkaline with concentrated ammonium hydroxide solution added drop by drop and extracted twice with 100 ml of chloroform to which 10 ml of ethanol has been added. The two extracts are combined and extracted with 50 ml of 0.1A sulfuric acid. The aqueous phase is separated, made alkaline with ammonium hydroxide, and reextracted with two 50 ml volumes of chloroform. The chloroform is dried with sodium sulfate, and carefully evaporated to dryness after addition of one or two drops of dilute hydrochloric acid to prevent the loss of volatile compounds. This gives Fraction D. It will be noted that no attempt has been made to subdivide this fraction. As has been said before, there is little advantage to be gained from doing so, and every unnecessary manipulation leads to delay and loss of material. 

The coupling of sensors with flow injection analysis (FIA) is already a very popular option. The flow regime offers important advantages over discrete manual measurements that include (1) Sample preparation processes such as reagent mixing, selectivity enhancement (e.g., removal of large molecular mass interferents such as protein by dialysis in clinical assays), and solvent extraction can all be carried out online. The improved sample preparation and more reproducible sample delivery result in improved measurement precision and accuracy. Drift is less of a problem as measurements are made of peak heights relative to a baseline. (2) Improved sensor lifetime in flow analysis, the sensor may be exposed to the sample for only a short period of time, and maintained in a friendlier matrix between measurements that can help counteract or delay the deleterious effects of the sample. (3) Automation the entire analysis can be... 

Advantages of ACOMP include its versatility as a generalized approach, its ability to make fundamental measurements without recourse to empirical models and calibration, its capacity for providing a data-rich stream of complementary information from multiple independent detectors, yielding multifaceted characteristics of polymerization reactions, and its use of the front end to extract, dilute, and condition a sample stream that allows sensitive detectors to provide reliable data without exposing them to harsh reactor or sample conditions. Disadvantages include the mechanical complexity of the front end, the delay time between a continuous fluid element s extraction from the reactor and downstream measurement by the detector train, and a small but continuous waste stream. ACOMP is more invasive than probes that can be placed at an outside reactor window, but are no more invasive than in situ probes, in that in either case access to the reactor contents is required. 

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