Kuderna-Danish evaporative concentrator

When sampling is completed, the sampler is disassembled, and the XAD-2 is removed and Soxhlet-extracted for 24 hours, using approximately 100 mL of methylene chloride. The resulting extract is concentrated to approximately 1 mL using a Kuderna-Danish evaporative concentrator. This concentrate is placed in a Teflon sealed vial and analyzed by combined GC/MS. The gas chromatographic and mass spectrometrie conditions used for analysis are given in Table IX. 

The volatiles from crushed neem seeds were purged with nitrogen, trapped onto Amberilte XAD-4 resin traps at room temperature, recovered and concentrated Into diethyl ether using a Kuderna-Danish evaporative concentrator at 30 "C, and analyzed by means of capillary gas chromatography/mass spectrometry (GC/MS). For comparative purposes, similar volatile concentrates were prepared from freshly chopped onion bulbs and garlic cloves, and blank controls were simultaneously prepared for each of the three test samples. 

Kuderna-Danish evaporative concentrator equipment with a Snyder or Vigreux column for macro-and microanalysis, depending on the scale of the construction. 

Aqueous distillates are extracted, usually with dichloro-methane (DCM), concentrated to small volumes, generally in a Kuderna-Danish evaporator, and examined by gas chromatography (GC) using a specific detection system. Additional chromatographic cleanup may be required, depending on the complexity of the sample and specificity of the chromatographic detector. 

Kido et al. [6] determined basic organic compounds such as quinoline, acridine, aza-fluorene, and their N-oxides in marine sediments found in an industrial area. The sediments were extracted with benzene by using a continuous extractor for 12h. Hydrochloric acid solution (IN) was added to the benzene extracts, and the mixture was shaken for 5min the acid layer separated from the benzene layer was made alkaline by the addition of sodium hydroxide, and the alkaline aqueous solution was extracted with diethyl ether the ether extracts were then dehydrated with anhydrous sodium sulphate and concentrated with a Kuderna-Danish evaporator. The concentrations were separated and analysed by gas chromatography-mass spectrometry and gas chromatography high-resolution mass spectrometry. 

Sample concentration is sometimes needed to increase the analyte concentration or to eliminate the extraction solvents, which might be incompatible with the HPLC mobile phase. Evaporation is carried out in open hoods, ovens, rotary evaporators, Kuderna-Danish evaporators, freeze driers or lyophilizers. 

Kuderna-Danish evaporator Apparatus for sample concentration, consisting of a small (10 ml) graduated test-tube connected directly beneath a 250 or 500 ml flask. A steam bath provides heat for evaporation with the concentrate collecting in the test-tube. 

The aliquot designated for extraction at neutral pH was extracted three times, with fresh 100-mL acetone/hexane (50/50). An ultrasonic cell disruptor, in pulsed mode at 50 percent duty cycle, was employed to enhance the contact between the extraction solvent and soil. Following each extraction, the soil was allowed to settle, the solvent decanted, and the combined supernatants from the neutral pH extraction were dried through a column of anhydrous sodium sulfate (5-cm bed height 3-cm diameter). Concentration of the extract was performed using a Kuderna-Danish evaporator. Final volume was adjusted to 1 mL using nitrogen blowdown evaporation. 

Kimoto et al. have used Ambersorb XE-340 to remove trace levels of volatile nitrosamines from tap water. In order to wet the adsorbent, it was first covered for 1 h with methanol and then washed with distilled water. Ambersorb XE-340 was packed in a 26 X 260 mm copper pipe equipped with a copper fitting on both ends. One fitting was connected to the faucet and the other to a valve which controls the flow rate. Water was sampled for 8.5 to 11.75 h. At the end of the water sampling, methanol was added to remove the water from the column. DCM (700 ml) was next passed through the column. The first 500 ml DCM contained more than 92% of the A-nitrosamines. The extracts were dried over anhydrous Na2S04 and concentrated in a Kuderna-Danish evaporator. 

Snyder column. Discard the first 10 % of the distillate, and continue distillation until about 20 % of the original volume remains in the distillation flask. Test the purity of the distillate by preparing an aliquot portion after 100 1 concentration in a Kuderna-Danish evaporator and checking... 

Concentrate the extract in a rotary evaporator or in a Kuderna-Danish evaporator to approx. 1 ml (without an air flow). Inject the extract into a chromatographic column of 12 mm diameter and 15 cm height, which has previously been packed to half height with n-hexane, then to a height of 7 cm with florisil and above that 1 cm of hexane-toluene mixture 1 1, maintaining a drop rate of 1 to 2 drops/second (3 to 5 ml/min). For the separation of non-polar interfering substances (in particular polychlorinated biphenyls... 

Column Extraction. Aqueous samples and distillates were added to glass chromatographic tubes or plastic syringe barrels containing 0.5 g Celite 560 per g of sample. After 20 to 30 min of equilibration, the columns were eluted with 100 ml of DCM [for NDMA, NPYR and N-nitrosomorpholine (NMOR) or ethyl acetate (for NDELA and BHP)]. Residual solvent was removed from the columns by applying nitrogen pressure. Extracts were dried with Na S0, and concentrated to 1 ml in a Kuderna-Danish apparatus (NuMA, NPYR, and NMOR) in a 50 C water bath or in a rotary evaporator for NDELA and BHP, using a 30 C water bath. 

Large volumes of solvent or indeed aqueous samples can be dried in a rotary evaporator operated under vacuum or at reduced pressure. The liquid evaporated is condensed into a reservoir. An alternative is to use a Kuderna-Danish concentrator which can also reduce several hundreds of millilitres of solvent to a few millilitres. The apparatus is shown in Figure 8.3. 

When trace quantities of materials are extracted, it is necessary to evaporate most of the solvent to concentrate the desired compound for further analysis. This can be difficult to do without losing the desired compound as well. The two most common ways of removing large volumes of solvent without appreciable loss of the desired compound are a Kudema-Danish concentrator and a rotary evaporator. The former is preferred for low-boiling solvents (< 100 "C, acetonitrile, acetone, methylene chloride), and the latter for higher-boiling solvents. A Kuderna-Danish concentrator is shown in Figure 9-6. 

Concentration of the solvent extract to 1 ml with a rotary evaporator, Kuderna-Danish, or under nitrogen flow... 

The 5 to 6 L of DCM recovered from the extractor was evaporated to 25 mL in a mantel-heated flask equipped with a 12-ball Snyder condenser. Final concentration to 1 mL was made in a water-bath-heated smaller flask with a Kuderna-Danish condenser. The suspended sediments were soxhiet extracted overnight with an acetone/hexane mixture. After back extraction with water to remove the acetone, the extract was concentrated to 1 mL by the above procedure. The extract was cleaned up on a minicolumn packed with 2 cm Na2S04/4 cm 40% H2SO4 in silica gel/2 cm florisil. Final gas chromatographic analysis was performed using dual capillary columns (SE54 and OV17) with electron capture detectors. Further method details and recovery efficiencies of the procedures have been previously reported (Oliver and Nicol 1982). 

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