Solid Sample Holders

Gel electrophoresis is an important technique for separating high-molecular-weight (MW) biological molecules, such as deoxyribonucleic acid (DNA), lipoproteins, immunoglobulins, and 

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Dry Oil Oxidation Fluorescence may be measured within or over an oil or within or over an emulsion of lipid in water providing the pH is below 5.5. When plate fluorescence is to be measured, solid sample fluorescence spectrophotometry is necessary (23). A Hitachi Solid Sample Holder Attachment for Model MPF-2A Hitachi-Perkin Elmer Fluorescence Spectrophotometer (Figure 4) was... 

Finally, the polyamide oxidative fluorescence is unmistakably quenched when the fluorescing plate is treated with sodium meth-oxide or IN sodium hydroxide, dried, and viewed under long-wave UV light, a test developed by Malshet, et al. (27). Methanol or water alone has no effect. Strong acid restores the fluorescence. We were not able to quantitate this quenching and restoration, because of the risk of damage to the solid sample holder. 

Perkin Elmer Model MPF-2A and MPF 44-B fluorescence spectrophotometers were used to measure fluorescence spectra of samples. The powder sample was placed in the solid sample holder attached to the instruments, which measures the reflectance fluorescence at 60° v/ith the exciting beam at 30°C to the sample surface. The samples were dried at 60°C in vacuum and kept in a desiccator containing P2O5. 

The openness of the structures formed in each phase was evaluated with fluorescence quenching using the Cary Eclipse spectrophotometer, Varian, Palo Alto, CA and its front-face accessory (accessory solid sample holder, Varian,... 

Some elements (S, Se, Te, P, As, Sb, Bi, Ge, Sn, Pb) in liquid samples arc conveniently converted into their volatile hydrides before being passed into the plasma, as discussed in Part A (Chapter 15). For some samples, any volatile solvent is first evaporated in a sample holder, which is then heated strongly to vaporize the resulting solid residue, as discussed in Part C (Chapter 17). 

For the DRIFTS study, the Nafion-Ti02 slurries were sonicated for 2 hours, dried at ambient conditions for 5 hr, and ground with a pestle and mortar until a fine powder catalyst was formed. 30 mg of the resulting catalysts were placed on top of 80 mg of inert CaF2 powder (325 mesh, Alfa Aesar) in a DRIFTS cell s sample holder. The sample holder was enclosed by a dome with two IR transparent ZnSe windows and a third CaF2 window for UV illumination. For the ATR study, the Nafion-Ti02 slurries, which were sonicated for two hours, were cast directly on the surface of the ATR ZnSe crystal to form a continuous solid film. The films were enclosed with a stainless steel cover equipped with a CaF2 window for UV illumination. 

Direct insertion probe pyrolysis mass spectrometry (DPMS) utilises a device for introducing a single sample of a solid or liquid, usually contained in a quartz or other non-reactive sample holder, into a mass spectrometer ion source. A direct insertion probe consists of a shaft having a sample holder at one end [70] the probe is inserted through a vacuum lock to place the sample holder near to the ion source of the mass spectrometer. The sample is vaporized by heat from the ion source or by heat from a separate heater that surrounds the sample holder. Sample molecules are evaporated into the ion source where they are then ionized as gas-phase molecules. In a recent study, Uyar et al. [74] used such a device for studying the thermal stability of coalesced polymers of polycarbonate, PMMA and polylvinyl acetate) (PVAc) [75] and their binary and ternary blends [74] obtained from their preparation as inclusion compounds in cyclodextrins. 

Steady state fluorescence spectra were recorded using a spectrofluorimeter (Fluorolog TCSPC Horiba Jobin Yvon) equipped with a sample holder for solids. 

SIMS is one of the only mass spectrometric techniques that allow solid samples to be analysed without any extraction of compounds or matrix addition. Generally, no specific preparation technique is required, and solid samples can directly be analysed if they are small enough to be fixed on the sample holder. In most cases, this means that the sample size must not be more than 1 cm. 

Mercury porosimetry is based on the fact that mercury behaves as a nonwetting liquid toward most substances and will not penetrate the solid unless pressure is applied. To measure the porosity, the sample is sealed in a sample holder that is tapered to a calibrated stem. The sample holder and stem are then filled with mercury and subjected to increasing pressures to force the mercury into the pores of the material. The amount of mercury in the calibrated stem decreases during this step, and the change in volume is recorded. A curve of volume versus pressure represents the volume penetrated into the sample at a given pressure. The intrusion pressure is then related to the pore size using the Washburn equation... 

An XRPD system equipped with a heatable sample holder has been described, which permitted highly defined heating up to 250°C [55]. The system was used to study the phase transformation of phenan-threne, and the dehydration of caffeine hydrate. An analysis scheme was developed for the data that permitted one to extract activation parameters for these solid-state reactions from a single non-isothermal study run at a constant heating rate. 

More modern systems (diffractometers) follow the same principles but the diffracted X-rays are detected with a solid state detector, as described earlier. Typically, the X-ray source is static and the sample and detector are rotated, with the detector moving at twice the angular velocity of the sample to maintain the equivalent angle. Such instruments typically make use of relatively large samples compressed into the window of a 35 mm sample holder. However, where the sample size is restricted, as is common with archaeological applications, a smaller sample (a few mg) can be attached to a silica wafer. In all cases the sample needs to be hnely ground to ensure a uniform diffracted beam. 

The analyte, either solid or admixed to some liquid matrix, is introduced into the FAB ion source by means of a probe bearing a sample holder or FAB target. The... 

DSC can also be used to determine starch retrogradation. After heating potato starch (30% (w/w)) to 180°C, samples are cooled to 5°C. Once the temperature reaches 5°C, the sample is immediately removed from the DSC and stored at low temperature. After a certain number of days, the sample pan is placed into the sample holder of the DSC, and heated from 5 to 180°C at 10°C /min. The instrument is calibrated using indium and an empty pan as a reference. The enthalpy (AH) of phase transitions is measured from the endotherm of DSC thermograms based on the mass of dry solid. Transition temperatures such as onset, peak, and completion temperature are also measured. 

If one wants to measure spectra in reflection, the task of building a sample holder is much simpler, because it can be machined in one piece from solid copper that... 

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