Column packings reaction detectors

Fig. 2.4p shows three types of post-column reactor. In the open tubular reactor, after the solutes have been separated on the column, reagent is pumped into the column effluent via a suitable mixing tee. The reactor, which may be a coil of stainless steel or ptfe tube, provides the desired holdup time for the reaction. Finally, the combined streams are passed through the detector. This type of reactor is commonly used in cases where the derivatisation reaction is fairly fast. For slower reactions, segmented stream tubular reactors can be used. With this type, gas bubbles are introduced into the stream at fixed time intervals. The object of this is to reduce axial diffusion of solute zones, and thus to reduce extra-column dispersion. For intermediate reactions, packed bed reactors have been used, in which the reactor may be a column packed with small glass beads. 

Analytical Procedures. The extracts from exposure pads, hand rinses, and apple leaves were evaporated to dryness in the 40-45°C water bath, and the carbaryl residues were determined by the procedure of Maitlen and McDonough (4). In this procedure, the residues were hydrolyzed with methanolic potassium hydroxide to 1-naphthol which was then converted to the mesylate derivative by reaction with methanesulfonyl chloride. The carbaryl mesylate was quantitated with a Hewlett Packard Model 5840A gas chromatograph (GLC) equipped with a flame photometric detector operated in the sulfur mode. The GLC column was a 122 cm x 4.0 mm I.D. glass column packed with Chromosorb G (HP) coated with 5% OV 101. The column was operated at a temperature of 205°C with a nitrogen flow rate of 60 ml/min. 

The GC determination of metal halides is complicated by the instability in chromatographic systems and different analytical solutions. Fluorides and chlorides are the halides that are used most often for different groups of metals the former are more volatile, but they also tend to be more reactive. The GC analysis of metal chlorides and fluorides necessitates highly inert column packings and inert chromatographic accessories, particularly the injection port, material of the column and the detector. Conversion of metal ions into halides involves different halogenation techniques. Direct reactions of metals... 

FIGURE 14-3. Separation of aspirin reaction mixture on a low-efficiency column. Column Bondapak C18/Porasil B (37-75 p.m) 2 mm ID x 61 cm. A-H are times noted on the chromatogram. Mobile phase MeOH/4% HOAc in H2O (35/75). Flow rate 1 mL/min. Detector UV at 254 nm, 0.2 AUFS. Sample 10 p,L of aspirin solution. (Note Actual separation will depend upon the quality of the mobile phase and column packing). 

Catalytic activity was determined in a tubular packed b isothermal reactor at 500 K and 1 atm. A gas mixture was fed to the reactor at 350 cm min (CO 3%, HjO 26% Hj 48% N2 23% v/v) the catalyst weight was 0.04 g with a particle size of 0.177-0.250 mm. Reactants were analyzed by gas chromatography, using a thermal conductivity detector. Two packed columns were employed to analyze the reaction mixture. One was packed with 5A molecular sieve to separate hydrogen, nitrogen and CO, while COj was analyzed in a column packed with Porapak Q. Absence of diffusional control was experimentally verified by measuring the reaction conversion with catalyst particles of various sizes. The b was diluted (D%=10% v/v) with inert particles to provide isothermal conditions. 

Figure 16.6 lactate dehydrogenase isoenzymes were detected by their activity. Either lactate -F NAD + or pynivate -f NADH was a post-column addition. The reaction detector wasalOcmxS mm i.d. column packed with 150 pm glass beads (as diol derivative) at 40 °C. Detection principle NADH absorbs at 340 nm whereas NAD does not. 

Homologation experiments were conducted in a 300 ml pressure reactor ( M/s Parr Inst., Co. U.S.A ). In a typical run, known amount of catalyst is mixed with known volumes of aqueous HI and methanol (total volume 50 ml) and placed in the reaction vessel. The reactor was pressurized to 30 atm CO and was maintained at 150 C. After 11 h contact time, the reactor was cooled to room temperature and analyzed for the products. Dimethyl ether formation was confirmed by passing the gaseous product through iodine in CS2 solution which gave tany colour. It was quantitatively analyzed by gas chromatography using molecular sieve 13X packed s.s column and TCD detector. Acetic acid and dimethylacetate were analyzed by GC ( Shimadzu, Japan ) and confirmed by their standards. 

Detector F ex 335 em 455 following post-column reaction with o-phthalaldehyde reagent solution (Pierce) pumped at 1 mL/min. The mixture flowed through a 250 X 4.6 column packed with 40 pm glass beads (Whatman) to the detector. 

The reaction gases were analyzed using an online Hewlett Packard Model 5890 GC equipped with a thermal conductivity detector (TCD) and two columns in series. The first column, 9 ft x 1/8 in. o.d. stainless-steel column packed with 60/80 mesh Hayesep R, was used to separate hydrocarbons, CO2 and N2O from O2, N2, and CO. The second column, a 6 ft x 1/8 in. o.d. stainless-steel column packed with 45/60 mesh molecular sieve 5A, was used to separate O2, N2, and CO. After injection of a sample into the Hayesep R column at 35 °C, O2, N2, and CO were allowed to elute into the molecular sieve column. The molecular sieve column was then bypassed and the CO2 and N2O were separated and eluted from the Hayesep R column and into the TCD. The molecular sieve column was then placed back on-line and the O2, N2, and CO were separated and detected by TCD while oven temperature increased 20 °C/min from 35 to 100 °C. Finally, the molecular sieve column was bypassed again and hydrocarbons were separated and eluted from the Hayesep R column when oven temperature increased 35 °C/min to 220 C. The reaction results... 

Baughman et al 7 studied the gas chromatographic behaviour of methylmercury compounds on a glass column (6ft x 0.25in) packed with 5% of DECS on Chromosorb W and operated at 160°C, and of phenylmercury compounds on a similar column packed with 3% of OV-1 on Chromosorb W and operated at 150 C. Flame ionization and Ni electron-capture detectors were used. Dimethyl- and diphenylmercury were stable under these conditions, but combined glc-ms confirmed that methyl- and phenylmercury salts decompose during gas chromatography. Reliable determination of methylmercury salts were achieved only on columns specially treated so as to make the decomposition reaction reproducible. Phenylmercury salts, which decompose extensively, could not be determined by gas chromatography. 

Owing to poor volatihty, derivatization of nicotinic acid and nicotinamide are important techniques in the gc analysis of these substances. For example, a gc procedure has been reported for nicotinamide using a flame ionisation detector at detection limits of - 0.2 fig (58). The nonvolatile amide was converted to the nitrile by reaction with heptafluorobutryic anhydride (56). For a related molecule, quinolinic acid, fmol detection limits were claimed for a gc procedure using either packed or capillary columns after derivatization to its hexafluoroisopropyl ester (58). 

A number of analytical techniques such as FTIR spectroscopy,65-66 13C NMR,67,68 solid-state 13 C NMR,69 GPC or size exclusion chromatography (SEC),67-72 HPLC,73 mass spectrometric analysis,74 differential scanning calorimetry (DSC),67 75 76 and dynamic mechanical analysis (DMA)77 78 have been utilized to characterize resole syntheses and crosslinking reactions. Packed-column supercritical fluid chromatography with a negative-ion atmospheric pressure chemical ionization mass spectrometric detector has also been used to separate and characterize resoles resins.79 This section provides some examples of how these techniques are used in practical applications. 

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