Tandem method

The dansyl derivative 9-azidononyl-5-(dimethylamino)naphthalene-l-sulfonate 35 was used by Yi and collaborators [91] as an azido-fluorescent label in a tandem method of sulfonium alkylation and click chemistry for the modification of biomolecules. Fluorescent labeling of a protein was successfully carried out after simple incubation of BSA with sulfonium salt 36 followed by azido-containing fluorophore 35, at room temperature. 

If however, detection was the objective, 5 ng/ml limit was practical in the tandem method. As with the other HPLC techniques, this method was compared to the reference HPLC-MS technique. Table V gives data obtained on plasma from a marijuana smoker using both methods. The only notable variance between the two methods occurred with the two hour sample which was received by our laboratory in a broken tube. 

When charge-transfer bonds are obscured by those of the original donors and acceptors, one may find of value a difference method [1] (e.g., Forster s tandem method [70]). Four cuvets of equal path length are used, two containing the charge-transfer complex solutions in series in the indicator beam of a double-beam spectrophotometer, and two cuvets, one with the unreacted donor and the other with unreacted acceptor solution, also in series in the reference beam. A difference spectrum is thus obtained which, however, needs special care in its interpretation. 

In conclusion, tandem methods with the use of different detectors of high efficacy are currently the best choice for analysis of dmg impurities. They allow both identification and quantification of the impurities present in medications, even at such low levels as parts per million (ppm) or parts per billion (1/10, ppb). 

Using two dosimeters with different energy dependencies, it is possible to determine the effective energy. This method, called the Tandem Method , consists of using... 

Asymmetric Tandem Methods Involving Unstable Imines etc. 

Of all tandem methods, SFE-HPLC is the most difficult coupling system to use. The main reason lies in linking a separation step at high pressure and generating a gas in the interface with a chromatographic technique, which commonly works under lower pressure and uses a liquid as a mobile phase. For this reason, in most applications, the analytes are collected offline and later analyzed by HPLC. SFE-HPLC has been performed for only a few specific applications. " ... 

Another interesting tandem method is SFE-capillary electrophoresis (SFE-CE). 

Tandem methods for chemical measurements are now widely accepted and employed even when tandem is defined in the narrowest sense, such as two-dimensional gas chromatography or tandem mass spectrometry. Tandem or triple quadrupole MSs became commercially available in the early 1980s, and today these instruments are routine concepts as linear quadrupole analyzers or as ion traps. Tandem or sequential methods result in loss of signal current, yet noise is lost more so thus, S/N is increased. 

The pitch and catch technique is a test with a transmitter and a receiver transducers where the path of the ultrasonic beam is not straight line but follows a complex path (the beam is reflected one or more times before reaching the receiver). Different configurations can be distinguished direct pitch and catch, in which the receiver is placed where the reflected ultrasonic beam is expected if there is no discontinuity indirect pitch and catch, in which the receiver is placed where the ultrasonic beam is expected to be if reflected by a discontinuity (Figure 12.8). Tandem method is a typical example of direct pitch and catch test. Delta testing is an example of an indirect pitch and catch test. 

Use of this tandem method resulted in a model ethylene/CO copolymer (Figure 2, polymer 2) that had a Tm (134 °C) close to that observed in our linear ADMET polyethylene (Figure 4, second entry) [17]. Since carbonyl and methylene groups have similar space filling characteristics, the CO functional group may be expected to cause very little disruption of the lamellar crystal lattice of polyethylene. 

In 2011, a palladium-catalyzed ring opening of furans as a source of a,p-unsaturated aldehydes was developed.In the presence of a palladium catalyst, heterocyclic compounds can be produced. In this procedure, furans may be ring-opened via pallado-catalyzed reactions leading to a,p-unsaturated aldehydes and ketones tethered to indole and isoquinoline moieties. Fu and co-workers developed a simple and efficient copper-catalyzed one-pot tandem method for the synthesis of benzimidazo[l,2-Z>]isoquinolin-ll-one derivatives... 

A one-pot tandem method for the synthesis of pyridazino[4,5-fc][l,4]thiazine-diones via Smiles rearrangement has been reported (Scheme 173). ... 

The data given in Table 30 include the results of five consecutive crackings carried out by the tandem method. In the five cycles not all the recycle material formed initially was cracked completely. It was not possible to carry out further cycles, because the absolute quantity of recycle material produced after cycle V was not sufficient to charge the autoclave in the normal way. If this quantity is relatively small compared with the initial fuel oil, it can be disregarded without the risk of introducing substantial errors... 

The results of the individual stages of the experimental determination of the steady-state parameters under laboratory conditions, by the tandem method, are given in Fig. 26. 

The object of the multiple-cracking experiments was to obtain data concerning the yields of the cracking products corresponding to total conversion of the heavy reflux into gas, petrol, kerosene, light reflux and cracking residue, i.e. the yields of the products from the cracking of heavy reflux in the entire round process of conversion. In order to obtain these data, the heavy reflux was cracked by the tandem method shown in Fig. 36. 

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