Nitrogen, as a purge gas

Some workers have reported loss of volatile organic Cr compounds at low temperatures, especially in tissue samples and in plants. Recent papers seem not to be troubled by this problem, probably because of the improved experimental conditions. Some workers have used nitrogen as a purge gas instead of argon. It has been shown that narrow CN bands introduce a continuum correction error at the 357.9-nm line in the presence of nitrogen. Argon should be used. Contamination of plasticware, pipets, etc. is a problem with Cr. Older Eppendorf pipets have stainless steel springs which can introduce Cr contamination. 

Samples of PMMA were heated in a vacuum oven at 120°C for 24 hours to drive off any moisture that had been absorbed. One sample of approximately 15 mg was placed in aluminum pans in a TA Instruments DSC 2920. The sample was equilibrated at 25°C and then heated from 25°C to 180°C at 10°C/min for the first run. The sample was then cooled slowly, again equilibrated at 25°C and the heating process was repeated for a second run. All of these tests used nitrogen as a purge gas. The glass transition function in TA Instrumental Analysis was used to calculate the Tg of the material by finding the inflection point in the Tg step. 

If nitrogen is being used as a purge gas, a moderate amount becomes trapped in the lattice of the frozen PF, at — 196°C and its removal necessitates a series of subsequent freeze-pump-tbaw cycles. After completion of the PO3 addition, a gas purge of 20 min is used to sweep the PF3... 

Melting behaviour A Perkin-Elmer Model DSC-2 differential scanning calorimeter with nitrogen as the purge gas has been used. The samples of 7-8 mg weight cut from the same sheets as in GPC and X-ray measurements were analysed by heating from 310 to 460 K at 10 degree/min rate. 

Why is nitrogen gas commonly used as a purge gas in infrared spectrometers Can you name another gas that can be used as a purge gas ... 

Table 4 summarizes commercial and precommercial gas separation appHcations (86,87). The first large-scale commercial appHcation of gas separation was the separation of hydrogen from nitrogen ia ammonia purge gas streams. This process, launched ia 1980 by Monsanto, was followed by a number of similar appHcations, such as hydrogen—methane separation ia refinery off-gases and hydrogen—carbon monoxide adjustment ia oxo-chemical synthetic plants. 

The mercury analyses were conducted using a Coleman Instruments mercury analyser (MAS-50) equipped with a recorder. The aqueous sample solution was contained in a 250 ml Pyrex glass bubbler placed at one end of a sampling train employing nitrogen as the purging and carrier gas. A schematic diagram of the entire system is shown in Fig. 5.12. 

Reineccius and Liardon [207] studied volatiles evolved from heated thiamine solutions. Samples of 2% thiamine hydrochloride in various 0.2M buffers were heated under various conditions. A temperature of 40°C and a sampling time of 45 min were found to minimize artifact formation and yet produce sufficient volatiles for analysis. Nitrogen was used as the purge gas at a flow rate of 50 ml/min. Several materials were evaluated as absorbents, with graphite found to be the optimum. A microwave desorption system was used to rapidly desorb the trapped volatiles onto a fused silica capillary column. Twenty-five compounds were identified in the headspace of the heated thiamine solutions. 

Differential scanning calorimetery (DSC) was used to measure heat capacity as a function of temperature. The DSC used in this study was a Perkin-Elmer model DSC-2. Liquid nitrogen was used as a heat sink and helium was used as the purge gas. Samples were usually about 30 mg, and a heating rate of 20°C/min was used for measuring Tgs and Tms. 

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