Alternative methods disadvantages

One alternative method for preparing field fortifications solutions/suspensions is to prepare each fortification sample of each matrix in a separate mini-vial in the analytical laboratory and ship the vials to the field for use. This procedure precludes the use of pipets in the field and may be useful when Field Scientists not experienced in the use of pipets are involved in the field fortification process. One disadvantage of this procedure is that the mini-vials, if not designed correctly, will be hard to handle in the field, and surface tension of the suspension or fortification solution will tend to leave unacceptable amounts of the solution/suspension in the vial or at the lip of the vial and not on the matrix in question. This procedure may lead to cross-contamination of samples as the field fortification liquid is forced from the top... 

PCR is an alternative method to the much more used regression method PLS (Section 4.7). PCR is a strictly defined method and the model often gives a very similar performance as a PLS model. Usually PCR needs more components than PLS because no information ofy is used for the computation of the PCA scores this is not necessarily a disadvantage because more variance of X is considered and the model may gain stability. 

Each chapter of this book describes an analytical technique and discusses its basic theory, applications, weaknesses and strengths, and advantages and disadvantages, and, where possible, compares it to alternate methods. The aim is not to go into significant theoretical considerations of the technique, but rather to provide information on how and when to apply the method with examples. 

An alternative method of generating nitrilium salts for a cycloaddition reaction is by the decomposition of an aryldiazonium fiuoroborate (80) in the presence of a suitable nitrile. This method has the disadvantage... 

Further disadvantage of the alkyne-azide cycloaddition is the lack of regiospecificity. On the other hand, cycloadditions of azides to alkenes are, in most cases, regioselective and afford 1,5-disubstituted triazolines . Therefore, the regioselective cycloaddition of an azide to an alkene, followed by aromatization (see Section 4.01.5.3.1) is an alternative method for the synthesis of 1,2,3-triazoles. 

The stable transformation of plants has been used routinely as a method to express vaccine and therapeutic proteins. A number of disadvantages such as the length of time taken for transgenic plants to be generated and containment (i.e., preventing the escape of transgenes into the environment) have brought about a search for alternative methods by which to express proteins in plants. One such alternative is the utilization of plant virus expression systems. 

Several alternative methods for the determination of sialic acid in body fluids and tissues have been described. Most of these methods make use of the classic periodate-TBA assay in combination with purification using HPLC [13]. Another method makes use of fluorometric HPLC of sialic acids after derivatization with a fluorogenic compound [9]. The most promising new method for the determination of free sialic acid in urine (and probably also other body fluids and tissues) is the HPLC-tandem mass spectrometry method [19]. This method is rapid, accurate, and sensitive, and is more robust than earlier methods. The only disadvantage is the expensive equipment that is required, which makes it only economical for specialized metabolic laboratories. Since this equipment is used for many different metabolic assays, the investment is certainly warranted, and nowadays almost essential for any metabolic laboratory. 

In the alternative method (85), a second sampler, consisting of a Teflon particle filter followed by a quartz filter, is operated in parallel with a quartz-filter sampler. The carbon recovered from the quartz backup filter of this second sampler is subtracted from the organic C determination of the first sampler (Q - TQ strategy). The rationale for this alternative approach is to minimize the extent of sorption of vapor-phase carbon on the first (particle-collection) filter, which, otherwise, might significantly diminish the amount retained on the backup quartz filter. The need for an additional sampler and very accurate air volume measurements is a disadvantage. 

The most commonly used technique for the determination of hydrogen peroxide in an industrial environment is the classical manual titration of a bath sample with potassium permanganate after acidification with sulphuric acid. In the past, numerous attempts have been made to perform the determination by means of an instrumental technique however, disadvantages were always encountered, which, up to now, have hindered the breakthrough of an alternative method. 

A range of alternative methods exists at each tier, each with its own advantages and disadvantages. Although there is substantial experience with uncertainty analysis in some fields (e.g. climate change), it would be premature to make prescriptive recommendations on which methods to use in exposure assessment. For example, when discussing the use of probabilistic methods for microbial risk assessment, the former European Commission Scientific Steering Committee concluded that a quick harmonisation at the present state-of-... 

Measurement of the electrical conductivity of emulsions has been considered as an alternative method since oil-in-water emulsions exhibit higher conductivity than water-in-oil emulsions (Rshl, 1972). However, this method which has been used with some success to control the level of water in butter (Prentice, 1953), has the disadvantage of being dependent on ion concentration. Therefore, certain added ions increase conductivity but might not increase stability to inversion. 

The number of disadvantages outweigh the advantages of radioimmunoassays and this leads to development of non-radioisotopic immunoassay methods. Many substances can be firmly attached to the antibody without changes in binding properties towards the antigen. This principle has been used in some methods to be competitive with radioisotopic methods. In order for alternate methods to function as alternatives to radioisotopic... 

The disadvantages of both wet and dry ashing which have only been outlined here, have led to the development of alternative methods for sample oxidation based on these two techniques. These are wet ashing using vapour phase attack or at elevated pressures, and dry ashing at low temperatures and pressures with reactive 02. 

---