Column oven test

The column oven is switched on and the displays and connections are checked visually. In the case of complaint the necessary measures are planned and documented. 

The test is performed at 20 °C and 40 °C. If the oven is not designed for cooling the 20 °C test is renounced. In addition, the oven can also be tested at a higher temperature, namely the one which is used on a regular base. 

The temperature in the column compartment can be very different depending on the oven type, therefore the temperature probe is attached as follows  

The location of the temperature probe must be documented (e.g. measured at the column ). 

The oven is stabilized at the setpoint temperature for at least 30 min before the measurement is performed. For the test the experimental temperature, measured by the temperature probe, and the oven display are registered and documented for 30 min in intervals of 10 min. 

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If the column is not located within the oven during the test sequence the column oven test (Section 25.7.) can be performed simultaneously. 

A temperature accuracy test of the column oven measured with a calibrated thermal probe is used. An acceptance criterion of 35 2°C is adopted. 

To test for temperature accuracy of a column oven, one should place the temperature probe/sensor of a calibrated/verified electronic thermometer (with at least 0.5°C precision) into the oven. The probe/sensor should not make contact with anything inside the oven. With the oven door closed, allow the temperature to stabilize for at least 20 min at each tested temperature (e.g., 30, 45 and 60°C). The thermometer s temperature should then be recorded at each temperature. The difference between the actual and set temperature should typically be within 1°C. 

It is recommended that OQ test the following on an HPLC system flow accuracy, pump compositional accuracy, pressure pulsations, column oven temperature accuracy/stability, detector noise/drift and wavelength accuracy, autosampler injection precision and carryover. 

A series of tests of instrument performance has been proposed31 and can be used to determine (1) packed column injector performance, (2) column oven heating and cooling specifications, and (3) FID performance ratings. 

Once in the column, compounds in the test mixture are separated by virtue of differences in their capacity factors, which in turn depend on their vapor pressure and degree of interaction with the stationary phase. The capacity factor, which governs resolution and retention times of components of the test mixture, is also temperature dependent. The use of temperature-programmable column ovens takes advantage of this dependence to achieve efficient separation of compounds differing widely in vapor pressure. 

The present operating procedure describes the procedure and the documentation for the performance qualification (PQ) of HPLC systems It can be used for both isocratic and gradient systems with UV detection and it is independent of the instrument manufacturer. The procedure includes the tests of pump, autosampler, UV detector and column oven. It can be put into practice immediately. 

Figure 7 Schematic diagram of semipreperative-scale SFC chromatograph 1 carbon dioxide supply 1 a regulator 2 prechiller/heat exchanger 3 SD-1 Varian pump with (7) 200-mLpump head with special check valves 4 modifier reservoir 5 SD-1 modifier pump with (6) 200-mL standard pump heads 8 check valve 9 inlet pressure transducer 10 injection valve 11 check valve to prevent blow-back 12 mixer 13 fluid temperature preconditioner 14 column 15 column oven 16 uv detector 17 outlet pressure transducer 18 back-pressure regulator 1 9 evaporator 20 restrictor 21 trim heater 22 selection valve 23 peak detector 24 bank of collection vessels (or cassette) 25 individual collection tubes/bottles 26 pressure relief valves 27 waste container, waste vent. The manual cassette can be replaced with an automated cassette fed by a robot holding 128, 25 x 150-mm or 338, 16 x 150-mm test tubes, or with 7 large bottles.

In the test, a sample aliquot diluted with a viscosity-reducing solvent is introduced into the gas chromatographic system, which uses a nonpolar open tubular capillary gas chromatographic column for eluting the hydrocarbon components of the sample in the order of increasing boiling point. The column oven temperature is raised at a reproducible linear rate to effect separation of the hydrocarbons. Quantitation is achieved with a flame ionization detector. The sample retention times are compared with those of known hydrocarbon mixtures, and the cumulative corrected area of the sample determined to the 371°C (700°F) retention time is used to calculate the percentage of oil volatilized at 371°C (700°F). 

Several tests were performed to assure that the measured retention volumes reflected sorbate retention in the miniature adsorption column. Thermocouple-based measurements of the injection valve compartment (which is mounted outside the column oven) revealed a 2 C lag in temperature from that recorded in the column oven. This small temperature difference had a negligible effect on the solute retention volume at flow rates of 0.5 ml/min and is further minimized at higher carrier gas flow rates due to prior thermal equilibration of the gas in the column oven. The contribution of instrument dead volume was assessed by measuring the retention voliune of a test solute (methanol) in the chromatographic system in the absence of the adsorption column. The system dead volvime was found to be less than 0.1 ml, a negligible contribution to the measured sorbate retention volumes. 

Operating devices may be miscalibrated after a while, for example the temperature accuracy of a GC column oven or the wavelength accuracy the optical unit of a UV/visible detector. This can have an impact on the performance of an instrument. Therefore a calibration program should be in place to recalibrate critical instrument items. All calibrations should follow documented procedures and the results should be recorded in the instrument s logbook. The system components should be labeled with the date of the last and next calibration. The label on the instrument should include the initials of the test engineer, the form should include his/her printed name and the full signature. 

Despite the many advances in capillary gas chromatography instrumentation and the remarkable resolution achievable, it has proven difficult to standardize a test method for the analysis of a mixture as complex as petroleum naphtha. Because of the proliferation of numerous, similar columns and the endless choices of phase thickness, column internal diameter, length, etc., as well as instrument operating parameters, many laboratories use similar but not identical methods for the capillary GC analysis of petroleum naphthas. Even minute differences in column polarity or column oven temperature, for example, can change resolution or elution order of components and make their identiflcation an individual interpretive process rather than the desirable, objective application of standard retention data. To avoid this, stringent column specifications and temperature and flow conditions have been adopted in this test method to ensure consistent elution order and resolution and reproducible retention times. Strict adherence to the specified conditions is essential to the successful application of this test method. 

A coherent plastic layer from a few mm to 2—3 cm thick separates the semicoke and coke from the unfused coal in the coke oven. Coking properties are assessed in Russia and some other countries by a measurement of the thickness of this plastic layer. A standardized test widely used in eastern Europe is the best known of this type (6) and involves a penetrometer used to measure the thickness of the plastic layer in a column of coal heated from the bottom. The various standard tests give results that are similar but do not give close correlations with each other. 

Dry column chromatography 494 Dry packing, columns (LC) 349 Dry test meter 843 Dual oven (GC) 62 Durapak phases (GC) 125 Dwell time, gradient elution, (LC) 489, 563... 

A soil infiltration test was devised to screen a large number of compounds within a limited time span. The amounts used are far in excess of quantities used in field application. A 5% diamide solution in isopropanol, 15 mL, was added to 50 g soil, air dried overnight, and then placed in a vacuum oven at 50° for 1 hr to remove traces of isopropanol. The treated soil, 10 g, was placed in a 25 X 500 mm glass chromatographic column with a coarse porosity fritted disc on top of a detachable adapter base. The soil was tapped down lightly with a wooden dowel to a depth of 12 mm in order to prevent channeling. Forty-five cm of water covered the soil. The period required for 200 ml distilled water to penetrate through 10 g of treated soil was recorded as the infiltration time. The test was arbitrarily discontinued after 2 weeks. 

Diastereomer ratios were determined by gas chromatography. Since the aldol adduct undergoes retroaldol reaction on the column, it must be silylated prior to injection. Approximately 5 mg of the crude adduct is filtered through a short plug of silica gel to remove any trace metals. The material is taken up into 1-2 mL of dichloromethane in a 2-raL flask or small test tube. To this solution are added 4-5 drops of N,N-diethyl-1,1,1-trimethylsilylamine and a small crystal of 4-(N,N-dimethylamino)pyridine (Note 11), The solution is stirred for 2 hr and injected directly onto the column. (Column conditions 30 m x 0.32 mm fused silica column coated with OB 5, 14 psi hydrogen carrier gas, oven temperature 235°C). 

Activity Measurements. To test catalytic properties of various samples partial oxidation of methanol to formaldehyde was studied in a flow micro-reactor operating under normal atmospheric pressure (10). For each run about 0.2 g of catalyst sample was used and the activities were measured at 173 C in the absence of any diffusional effects. The feed gas consisted of 72, 2 and by volume of nitrogen, oxygen and methanol vapor respectively. Reaction products were analysed with a 10% Carbowax 20 M column (2m long) maintained at 60 C oven temperature. 

The sulfide 1 (0.75 mmol) is dissolved in dichloromethane (2-3 mL) and adsorbed over silica supported sodium periodate (20%, 1.36 g, 1.28 mmol) that is wetted with 0.3 mL of water by thoroughly mixing on a vortex mixture. The adsorbed powdered material is transferred to a glass test tube and is inserted in an alumina bath (alumina 100 g, mesh 65-325, Fisher scientific bath 5.7 cm diameter) inside the microwave oven. The compound is irradiated for the time specified in the table and the completion of the reaction is monitored by TLC examination. After completion of the reaction, the product is extracted into ethyl acetate (2x15 mL). The removal of solvent at reduced pressure affords crude sulfoxide 2 that contains less than 5% sulfone. The final purification is achieved by column chromatography over silica gel column or a simple crystallization. 

Clayfen (1.0 g) is thoroughly mixed with the sulfide (2 mmol) in a test tube. The reaction mixture is placed in an alumina bath inside the microwave oven and is irradiated for the stipulated time. On completion of the reaction, monitored by TLC, the products were extracted with CH2C12 (3x10 mL). The solvent was removed on a rotary evaporator and the crude product, thus obtained, was charged on a silica gel column. The fractions eluted by chloroform-hexane (1 1) provided sulfone and final elution in chloroform afforded pure sulfoxide. 

Aldehyde/ketone (5 mmol), amine (5 mmol), diethyl phosphite (5 mmol) and montmorillonite (1.5 g, Aldrich, montmorillonite, KSF) were admixed in a Pyrex test tube and exposed to microwave irradiation at 450 W using a (BPL, BMO, 700T, indicates the commercial name of microwave oven) focused microwave oven for an appropriate time (pulsed irradiation 1 min with 20 s interval). After complete conversion of the reaction, as indicated by TLC, the reaction mixture was directly charged on a small silica gel column and eluted with a mixture of ethyl acetate-hexane (3 7) to afford corresponding pure a-amino phosphonate. 

Methoxybenzaldehyde lb (136 mg, 1 mmole) and NH2OHHCl (84 mg, 1.2 mmole) were mixed thoroughly with NH4OAC (108 mg, 1.4 mmole). The resulting powder was taken in a test tube, kept in an alumina bath inside a micro-wave oven and irradiated for 1 min. The mixture was removed from the oven, cooled and shaken with CHC13 (15 mL). After filtration, the filtrate was concentrated and the residue was subjected to column chromatography over silica gel using hexane-EtOAc (7 3) as eluent to afford 4-methoxybenzonitrile 2b (119 mg, 90%). 

A mixture of carbonyl compound 1, iodobenzene diacetate (1.5 equiv.), and orga-nosulfonic acid (4.5 equiv.) was placed in a test tube placed inside the alumina bath and irradiated for 10-40 s at ten-second intervals in a domestic microwave oven at full power (600 W). After cooling at room temperature the mixture was extracted with dichloromethane (2x20 mL), washed with H20, and dried over MgS04. The mixture was evaporated and the residue was column chromatographed with ethyl acetate-hexane (1 3) to give the desired a-organosulfonyloxy carbonyl compound 2. 

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