Kuderna-Danish evaporative

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. 

A lead blank (500 L of distilled water containing 25 /xg/L of Pb(N03)2) was pumped onto the ion-exchange columns only. The aqueous eluents were combined with the acetonitrile eluant for each column NaCl was added to separate the aqueous and organic phases. After separation, the aqueous phase was extracted twice with acetonitrile. The extracts from each column were pooled and reduced in Kuderna-Danish evaporators to a final acetonitrile volume of 4-6 mL and then diluted to a known volume with distilled water for atomic absorption spectroscopic (AAS) determination of lead. AAS analysis was on an IL 951 with an air-acetylene flame the 217.0-nm lead line was used. 

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. 

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. 

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. 

Vacuum evaporator (if necessary, without condensor) or 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... 

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

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