Injection commutator

Then there is a unique injective k-linear map X o(R) - VCR) such that for every Aq In a and f R->A0 the following diagram commutes ... 

We may assume that f is a morphism in CL" Since df is injective, f is surjective, hence the first inequality is obvious. We have a commutative diagram ... 

Fig. 5.6. (A) Flow-injection manifold for the wet digestion of shellfish slurry samples C carrier solution, P peristaltic pump, 1C injector commutator, W waste, r restrictor. (B) Dynamic manifold for the analysis of sludge slurries in an on-line digestion-reduction system by Fl-HG-AFS IV injection valve, AFS atomic fluorescence spectrometer, P peristaltic pump. (Reproduced with permission of the Royal Society of Chemistry.)...

F.J. Krug, H. Bergamin-Filho, E.A.G. Zagatto, Commutation in flow injection analysis, Anal. Ctiim. Acta 179 (1986) 103. 

The versatility, ruggedness and simplicity of sequential injection systems have been often recognised [76—78]. In fact, different analytical procedures could be carried out using the same manifold, commutation could be better exploited, and reagent addition was carried out only in the presence of the sample, thus reducing reagent consumption and waste generation. 

Multi-commuted flow analysers are characterised by enhanced flexibility and easy operation and combine some of the attractive characteristics of both segmented and unsegmented flow analysis. In this way, segmented flow, flow injection and sequential injection analytical procedures are efficiently implemented in multi-commuted flow manifolds. 

Another alternative for designing multi-commuted flow systems operating in the pumping mode is to exploit syringes as fluid propulsion devices. This led to the proposal of multi-syringe flow injection analyser by Albertus et al. in 1999 [109] as an advanced means of managing multichannel flow analysis. 

The multi-port selection valve of a sequential injection analyser can be regarded as an advanced commuting device, which selects one inlet port to be commuted to any one outlet port at a time. Also, the entire manifold can be accommodated in such a valve, leading to the lab-on-valve concept [84]. 

Proper exploitation of multi-commutation has led to the inception of different flow analysers such as the multi-pumping flow system, the multi-syringe flow injection system, the flow-batch system, the discontinuous flow system [153] and the all injection system [154],... 

L. Albertus, A. Cladera, V. Cerda, A robust multisyringe system for process flow analysis. Part II. A multi-commuted injection system applied to the photometric determination of free acidity and iron(III) in metallurgical solutions, Analyst 125 (2000) 2364. 

In early applications [2], a by-pass transmission line was incorporated in the valve in order to avoid disruption in the manifold during the time interval needed for the sampling loop to be displaced from the load to the inject position. With currently available valves and commutators, this bypass line is no longer necessary, even if manual sample insertion is required. 

An alternative way to implement hydrodynamic injection is to use an injector—commutator [60]. With this strategy (Fig. 6.12), volumes as low as 600 nL can be precisely injected and the sample carrier stream is not stopped, resulting in a more stable flow. The other advantages of hydrodynamic injection are maintained. 

Zone sampling has usually been performed by using two loop-based injectors (Fig. 7.4) or a double injection valve/commutator furnished with external sampling loops [25,26]. 

Loop-based injection is used for sample insertion and a similar procedure is used for displacing the tubular detector D between monitoring sites a and b (Figs 7.9 and 7.10, lower). Consequently, this strategy has usually been accomplished using two loop-based injectors or a double injection valve/commutator [81], where a flow cell with two small transmission lines replaces one of the sampling loops. Although the flow system can be manually operated, computer-controlled valves or commutators have been preferred. 

Diverse Water, whole blood, culture cells Ultrasound-assisted filtration UV-Vis Diverse Multi-commuted flow injection system with three parallel analytical paths pressurised gas as the fluid propellent [150]... 

Placement of the mini-column prior to the sample introduction port can also be useful in unsegmented flow analysis, as demonstrated in the flow injection spectrophotometric determination of molybdenum in plant digests [236]. This method relied on the influence of molybdate anions on the rate of iodide oxidation by hydrogen peroxide under acidic conditions, and some potential interfering cations needed to be separated. To this end, a cation-exchange resin mini-column was attached to the central sliding bar of an injector-commutator hence, it could be displaced between two different streams. Initially, the sample solution was pumped... 

FIGURE 8.19 Flow diagram of an unsegmented flow system with SPE after the injection port. S/E = sample or eluent R, — optional make-up reagent L — sampling loop C = sample carrier stream MC = mini-column R2 — reagent Rc — coiled reactor D — detector IC — injector-commutator shaded area — alternative IC position arrows = sites where pumping is applied. For details, see text. 

Phenylephrine hydrochloride Pharmaceutical formulations Dowex 50 W X8 ion-exchange resin UV-Vis 5.8 mg I, 1 Multi-commuted flow injection system sequential sample and eluent insertions [509]... 

A special type of injection valve, developed and most frequently used by the Brazilian group in Piracicaba, is called a commutator by its inventors, and features a three-layer sandwich design, with the middle layer sliding between the two outer layers (Fig. 2.6). This valve is also capable of performing very many complicated functions, described in detail by Krug et al.[6]... 

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