Reagent degradation

Figure 7.11 shows another variation, associated with a lower sensitivity. Both fixed and unfixed peptide controls stain approximately equivalently, but both only stain the 50pg/mL peptide control. This lower sensitivity can be due to a suboptimal reagent concentration, reagent degradation, improper procedure, or partial instrument failure. 

The non catalytic blank run carried out at 70°C of the 0.01M phenol - 0.1M HP solution showed that no reagent degradation occurs without a catalyst at the selected reaction... 

Monotonic increases or decreases in the T plot are generally related to changes in calibration standards, or the Q.C. samples themselves. Failure to adequately preserve stored standards or samples will lead to this pattern. Slow, constant reagent degradation can also produce the TREND pattern. 

Another concern with packed-bed reactors is reproducibility. There are two parts to reproducibility can multiple packed-bed reactors be made reproducibly and what is the stability of the reactor The first question concerning reproducibility can be answered as follows. The art of packing a column is at times difficult and each individual analyst will have different success. However, all packed-bed reactors can be calibrated in the FIA system. A variation in the performance level between reactors of less than 10% is acceptable. The second reproducibility question concerns the loss in reactivity due to reagent degradation or saturation of the reactive sites. In the ideal case the reactivity of the column should not change with respect to time, thereby producing a reproducible signal for the same concentration of analyte. This is a more difficult problem. Ideally, the analyst should find the reactor conditions that will minimize loss of activity. In practice, especially with enzymes, this condition will not be met. Frequent calibrations will be needed to insure the most accurate results. 

Failure to store lodo-gen tubes under vacuum results in reagent degradation and ineffective iodination. 

Evolved gas analysis (trapped solvents, unreacted reagents, degradation products)... 

Acetate and triacetate are essentially unaffected by dilute solutions of weak acids, but strong mineral acids cause serious degradation. The results of exposure of heat-treated and untreated triacetate taffeta fabrics to various chemical reagents have been reported (9). Acetate and triacetate fibers are not affected by the perchloroethylene dry-cleaning solutions normally used in the United States and Canada. Trichloroethylene, employed to a limited extent in the UK and Europe, softens triacetate. 

Extraction of hemiceUulose is a complex process that alters or degrades hemiceUulose in some manner (11,138). Alkaline reagents that break hydrogen bonds are the most effective solvents but they de-estetify and initiate -elimination reactions. Polar solvents such as DMSO and dimethylformamide are more specific and are used to extract partiaUy acetylated polymers from milled wood or holoceUulose (11,139). Solvent mixtures of increasing solvent power are employed in a sequential manner (138) and advantage is taken of the different behavior of various alkaUes and alkaline complexes under different experimental conditions of extraction, concentration, and temperature (4,140). Some sequences for these elaborate extraction schemes have been summarized (138,139) and an experimenter should optimize them for the material involved and the desired end product (102). 

The acid is rather slow to react with aUphatic hydrocarbons unless a double bond or other reactive group is present. This permits straight-chain fatty alcohols such as lauryl alcohol [112-53-8] C22H2 0, to be converted to the corresponding sulfate without the degradation or discoloration experienced with the more vigorous reagent sulfur trioxide. This is important in shampoo base manufacture (see Hairpreparations). 

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