Protection measures purging

To prevent oxidation of substances on the layer, protective measures must be taken even before the samples are applied. Using the CAMAG Linomat IV with inert gas blanket, nitrogen (for example) can be applied before and during application of the sample. To develop thin-layer chromatograms with exclusion of O2, the chamber is purged with CO2 if the substances are not affected by this gas, or alternatively with N2. For this, a lid fitted with a tube with a double-valve gas supply system is useful [20, p.69]. 

It must further be observed that inertization is acknowledged as a protective measure only if it is continuously supervised by measurements. A vacuum purge inertization of an apparatus repeated once or twice without any subsequent supervision cannot be accepted as a preventive protecting measure. 

Outgassing of constructional components (oxygen adsorbed on parts of the measuring cell) and dead volume Switch on the flow of protective gas to the microbalance several hours before measurement. Purge the vacuum connection as well. Only open the furnace briefly to insert the sample. Active replacement of air through slight evacuation to about 1 kPa. Then flood with the desired purge gas (if necessary twice). 

USEPA = United States Environmental Protection Agency. No specified time interval between field measurements. If the purge volume is small, collect measurements with enough frequency to evaluate stabihty. If the purge volume is large, take field measurements approximately 15 min apart. FLDEP = Florida Department of Environmental Protection. Allowable variation between two consecutive readings taken at least 2-3 min apart following the collection of one well volume. ... 

EPA. 1989c. Measurement of volatile organic compounds in water by purge and trap capillary column gas chromatography with photoionization and electrolytic conductivity detectors in series -method 502.2. Cincinnati, OH U.S. Environmental Protection Agency, Environmental Monitoring Systems Laboratory. 

After maintenance or repair, the door will be closed and subsequently locked, and inlet and outlet valves are opened to start the purging procedure and subsequent normal operation. The mode of operation is leakage compensation, i.e. the protective gas outlet pipe and the common purge flow or volume measuring device are active during purging only. 

The FT-IR spectrometer (Bruker Vertex 70) and the MCT (mercury cadmium telluride) detector are moved out of the accelerator room to be protected against radiation (Fig. 4). The infrared beam is guided on a distance of six meters by dried air or Nj-purged gold coated optical conduits and mirrors. The spectra are obtained from 100 scans with a 4 cm" resolution. Under our conditions, 24 seconds are required to record a spectrum. It is thus possible to follow the evolution of the spectra after irradiation by recording spectra every 30 seconds, for example. In all cases, spectra of irradiated samples are recorded with reference to the same sample just before irradiation, which allows detecting the effects of irradiation by measuring its... 

The possible procedures which may be employed to reduce a contamination error depend on the source. A viscous sample which sticks to the glass bulb may require multiple solvent rinses that is, rinsing with a solvent which dissolves the sample. In order to prevent a gas contamination, the sample must be protected from the contaminant by blanketing the sample with an inert gas. To remove a gas contaminant from the sample prior to the pH measurement, the sample can be purged with an inert gas. 

The term back pressure describes the position of the EPC valve behind the injector in the split exit line, in combination with a mass flow controller in front of the injector (see Figure 2.48). In this widely used carrier gas regulation scheme for split/splitless injectors, the pressure sensor is typically found in the septum purge line close to the injector body to ensure a pressure measurement close to the column head. A filter cartridge may need to be used to protect the regulation unit from any carrier gas contamination. 

Constructional measures have to be incorporated between the balance and the furnace to protect the balance against the effects of heat radiation and the ingress of corrosive decomposition products. In most cases the balance housing is purged with a protective gas. 

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