Microgravimetric method

Ultramicrogravimetric kinetics The use of microgravimetric methods to follow polymer growth allows us to know the influence of each studied variable on the polymer production. No interference of possible parallel reactions, giving non-polymeric products, on the measured magnitude (the polymer weight) is expected. In addition, and related to in-situ determinations through the quartz crystal microbalance [77-9],... 

The barrier properties of the PCL-based composites were investigated. The transport properties, sorption and diffusion, were measured by a microgravimetric method . The studied model permeants were methylene chloride and water vapour for which the zero concentration diffusion coefficient Dq was determined. The presence of clay (hydrophilic platelets) in the composite gives rise to specific sites on which water molecules can be entrapped and immobilized, thus the water sorption increases on increasing the clay content, particularly for microcomposites containing Cloisite Na It was found out that the microcomposites as well as the intercalated nanocomposites have diffusion parameters for water vapour very near to those of pure PCL. 

Even refined electrochemical methods cannot alone provide full information about the molecular structure of the metal/ solution interface. Hence, many nonelectrochemical techniques have been developed in the past few decades to study the double layer. They include spectroscopic, microscopic, radiochemical, microgravimetric, and other methods. A combination of electrochemical (chronovoltammetry, chronocoulometry, impedance spectroscopy, etc.) and nonelectrochemical methods is often used in studying mechanisms of the electrode process. 

Metal NPs have received tremendous attention in the field of bio-analytical science, in particular the sequence-specific DNA detection [23,24]. This is attributed to their unique properties in the conjugation with biological recognition elements (e.g., DNA oligonucleotide probe) as well as in the signal transduction with optical [22,25], electrical [26], microgravimetric [27] and electrochemical [23,28-30] methods. 

The performance of the vacuum microbalance described in these pages illustrates the advantages of precision microgravimetric techniques in surface studies. The instruments are sensitive and make direct and continuous measurements of gravimetric effects attending rate processes or equilibrium conditions. They are adaptable to high vacuum operation. Methods are available for preparing sample surfaces of well-defined... 

Zhou XC, Huang LQ, Li SFY (2001) Microgravimetric DNA sensor based on quartz crystal microbalance comparison of oligonucleotide immobilization methods and the application in genetic diagnosis. Biosens Bioelectron 16 85-95... 

TLC (PC, as well) does not provide quantitative information of the highest precision and accuracy. Quantitative thin-layer chromatography can be performed by applying a known volume of the sample to a chromatoplate and developing the plate, followed by locating and recovering the separated substance by elution as described above. This isolated material can then be quantitatively determined by any of the usual methods of quantitative analysis such as titration, microgravimetric procedures and colour reactions. 

The electrochemical kinetics from Tafel slopes obtained at low overpotentials (region 1 in Figure 10.5) is related to the monomer oxidation on the metal and the polymerization initiation. At high overpotentials after the change of slope (region 2 in Figure 10.5) a reaction order equal to that obtained from microgravimetric determinations is attained. Both empirical kinetics overlap the one obtained from Tafel slopes at low overpotentials when a polypyrrole electrode is used. This means that the Tafel slope is an adequate method to study electrochemical polymerization (monomer oxidation on the polymer) when a polymeric electrode is used. 

Different electronic transduction methods to probe DNA recognition events on surfaces will be addressed in the present account. These include electrochemical transduction means such as amperometry, faradaic impedauce spectroscopy or chronopotentiometry, and microgravimetric, quartz-crystal-microbalance (QCM) measurements. 

---