DuPont liquid chromatograph

The DuPont Model 830 liquid chromatograph (Fig.3.32) makes use of a pneumatic single-displacement pump which works on the pneumatic amplification principle (Fig.3.33). Compressed gas at a pressure of 0—100 p.s.i. is delivered to the large piston head. The amplification factor for this pump is 45 1. Thus pressures of up to 4500 p.s.i. are possible for solvent delivery, although the system has a recommended working range of up to... 

A Perkin-Elmer MPF-2A Fluorescence Spectrophotometer was used to determine the excitation and emission wavelengths required for achieving maximum fluorescence intensity for the pesticides studied. The MPF-2A contained a 150 watt xenon arc and an excitation monochromator with a grating blazed at 300 nm as the excitation unit a Hamamatsu R 777 photomultiplier tube (sensitivity range 185 - 850 nm) and an emission monochromator grating blazed at 300 nm as the emission detection unit. A DuPont Model 848 Liquid Chromatograph was used for HPLC (Figure 2). The accessory injection device included a Rheodyne Model 70-10 six-port sample injection valve fitted with a 20 y liter sample loop. A Whatman HPLC column 4.6 mm x 25 cm that contained Partisil PXS 1025 PAC (a bonded cyano-amino polar phase unspecified by the manufacturer) was used with various mobile phases at ambient temperature and a flowrate of 1.25 ml/minute. 

RP-HPLC Step B Dried, pooled 1-min fractions were further purified by reversed phase Iff LXI on a Zorbax C-8 150 SP column (DuPont) on a 1090 liquid chromatograph equipped with a photodiode array detector and Chemstation (Hewlett Packard). The samples were eluted with a linear gradient from 5 to 60% acetonitrile in 0.25 N triethvlammonium phosphate (TEAR), pH 2.20, over one hr at 28 C and 0.4 ml/min. Fractions were collected over 1 min intervals and concentrated in the Speed-Vac to remove the acetonitrile. 

The D4 content of the samples was determined by reverse-phase high-pressure liquid chromatography (HPLC) with a Varian 5500 liquid chromatograph. A DuPont Zorbax ODS (Cis) column was used with a Wilmad infrared detector set at 12.45 xm to monitor the Si-CHa vibration. The mobile phase was an 83 17 mixture of acetonitrile and acetone at a flow rate of 0.8 mL/min. A Rheodyne injector valve operating on compressed air was used with a 10-p,L sample loop for reproducible injection volumes. Ethyl acetate was used to dissolve the samples for analysis. 

Gel Permeation Chromatography. A Waters (model 150-C ALC/GPC) liquid chromatograph with a refractive index detector was used for molecular weight characterization. The unit was equipped with two sets of silanized Dupont blmodcLl columns (Zorbax PSM 60S/100S), with molecular weight range 2 x 10z to 10° and total retention volume of 24 ml. Samples were cut across the plaque thickness as with DSC. Polymer solutions were prepared 1n N,N -dimethyl -formamide, DMF, at 0.1%... 

Eckfeldt JH, Nelson KM. Salicylate determined with a microcentrifugal analyzer, and compared with DuPont aca, Trinder, and liquid-chromatographic methods. Chn Chem 1983 29 839-41. 

In the DuPont 848 liquid chromatograph, a special Haskel mini-pump is used, derived from the Haskel Model M. The volume of the cylinder is small (about 2 ml). In the original Haskel Model M pump, the return of the piston is actuated by an air selector valve and a spring, so that the liquid pressure is not constant because the gas piston must compress the spring during its forward stroke. In the modified pump, the spring is replaced with a small counter-pressure. The main characteristics of commercial pneumatic amplifier pumps are summarized in Table I. 

The liquid chromatograph used was a Perkin Elmer Series 3 with an LC-55S scanning UV detector. Samples were injected on a Rheodyne 7105 sample-loop high pressure injection port. The columns used were the Dupont Instruments Zorbax ODS and Zorbax C8. 

DuPont Model 830 liquid chromatograph, equipped with a DuPont Model 837 spectrophotometer. Extinction at 380 nm recorded by means of a Hewlett-Packard Model HP 3380 A integrator Column... 

Liquid chromatograph (DuPont, Model 830) equipped with a differential refractometer detector Column... 

Figure 1. Analytical anion-excbange HPLC of a commercial oligofdA) preparation on a SAX column. Sample. 10 fig oligofdA) column, Whatman Partisil 10 SAX (4.6 x 250 mm) apparatus, DuPont 850 liquid chromatograph with a DuPOnt UV spectrophotometer set at 270 nm with 0.04 AUFS (absorbance units full scale) elution, linear gtadieni from 1 mM potassium phosphate, pH 6.3, 60% (v/v) formamide to 0.3 M potassium phosphate, pH 6.3, 60% (v/v) formamide in 75 min flow-rale, 1 ml/min.

Figure 14. (a) Semi-preparative anion-exchange HPLC on a RP-NH2-column of a nuclease digest of an aminoacyl-tRNA. Sample, 3 A2 units of a ribonuclease T1 digest of [ C]Phe-tRNA (yeast) column, LiChrosorb RP-NH2 (4.6 x 250 nm) apparatus, DuPont 850 liquid chromatograph with a DuPont UV spectrophotometer set at 260 nm with 1.28 AUFS elution, linear gradient from () to 0.1 M ammonium phosphate, pH 4.5, in 15 min, ftom 0.1 to 0.3 M ammonium phosphate, pH 4.5. in 10 min and from 0.3 to 1 M ammonium phosphate, pH 6.0, in 10 min flow-rate, 1.5 ml/min. Radioactivity was monitored off-... 

The chromatograph had an all glass linear splitter (split 80 1) and a helium linear velocity of 23 cm/sec. A Perkin-Elmer fused silica column was used which measured 0.235 mm id, x 25 m long and which was coated with OV-101 (methyl silicone) liquid phase. The column was held 4 min at 45°C then programmed at 3°c/min to 120°C. Mass spectra were obtained using tandem gas chromatography/mass spectrometry. The column effluent was passed into the ion source of a DuPont Model 21-491 mass spectrometer (DuPont Instrument Division, Wilmington, Delaware). Mass spectra were obtained at 70 eV and a source temperature of 200°C. 

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