Kudema-Danish

Snyder column Kudema Danish concentrator Nitrogen evaporation Vacuum... 

Snyder columns are designed to allow highly volatile solvents to escape while retaining semivolatile analytes of interest. Snyder columns are generally fitted onto the tops of flasks containing extracts, and column design permits solvent to escape as the flask is heated. The analytes of interest condense from a gas to a liquid phase and fall back into the solvent reservoir. The Kudema-Danish concentrator is a Snyder column with a removable collection tube attached to the bottom. As solvent is evaporated, the extract is collected in the collection tube. 

The sample is extracted with dichloromethane by using one of three techniques Soxhlet extraction (10 g of sample with 300 mL of solvent for 16 h), blender extraction (25 g of sample with sodium sulfate and 3 X 150 mL of solvent), or sonication (25 g of sample with sodium sulfate and 3 X 150 mL of solvent) (21). Once the sample has been extracted, the solvent volume is reduced by using either rotary evaporation or a Kudema-Danish apparatus. 

Glassware. All special borosilicate glassware was fabricated in-house. Kudema-Danish (K-D) evaporators and the modified Snyder columns were constructed as per the design described previously (25) adsorption glass... 

Therefore, an additional cleaning and quality assurance step was used. Columns of 100 mL of resin were prepared and eluted with 200 mL of ether. The ether was then concentrated to 1 mL by Kudema-Danish evaporation and analyzed by a capillary GC with an FID. This analysis showed that many peaks were not removed after 200-fold concentration, and additional resin cleaning steps were needed. Alternate elution of the resin with successive single bed volumes of... 

The concentration procedure was performed on the sample within 3 days of arrival at the laboratory. Upon arrival, all ether extract samples were stored at —10 °C in a freezer. The ether elution after the water was frozen out was further dried by passage through anhydrous sodium sulfate. The sample was then concentrated by a Kudema-Danish evaporator to 2 mL. After concentration, 1.0 mL of the 2-mL concentrated sample was base extracted to remove the chemicals interfering with the capillary GC analysis. The base extraction procedure developed in this study is the following ... 

Analytical Procedures. Hydrophobic Neutral Fraction. The hydro-phobic neutral fraction, which was desorbed in methylene chloride, was concentrated to an appropriate volume (1 mL) in a Kudema-Danish apparatus. Then, under a stream of N2 and after addition of the internal standard (i.e., hexa-methylbenzene), this fraction was analyzed by GC-FID and GC-MS. 

Hydrophobic Base Fraction. The hydrophobic base fraction was adjusted to pH 10. A 50-/uL aliquot of the aqueous solution was subjected to HPLC analysis to test for the presence of 5-chlorouracil. The remaining aqueous solution was solvent extracted with methylene chloride. The extract was first concentrated in a Kudema-Danish apparatus, then under a stream of N2, and analyzed by GC-FID and GC-MS. 

Each of these six organic fractions was reduced to a volume of about 5 mL in a Kudema-Danish concentrator under a three-ball Snyder column and then to a volume of 1.0 mL under a gentle stream of dry nitrogen. These concentrates, or their methylated derivatives adjusted to the same concentration, were analyzed as described in the next section. 

The ether was concentrated by Kudema- Danish evaporation and then solvent exchanged to hexane to give a final volume of 0.3-0.4 mL. To quantify the compounds present, the samples were spiked with a known amount of anthracene-dio as an internal standard just prior to injection. The concentrated extracts were analyzed by capillary GC-mass spectrometry (GC-MS). 

A final 4-L aliquot of concentrator effluent was collected and extracted sequentially with dichloromethane at neutral, acidic (pH 2), and alkaline (pH 11) pH by using two extractions at each pH. The dichloromethane extracts were pooled and further concentrated by using Kudema-Danish evaporators. Analytical results from this residue were used in mass balance determinations under the conservative assumption that the concentrations of compounds present in the column effluent were relatively constant and that there was good partitioning of each into dichloromethane. 

Samples were eluted in the reverse direction by using the Milton-Roy pump with the pulse dampener removed. The eluant flow (50-75 mL/min at 200-300 lb/in.2) was monitored at 254 nm by using an Altex 153 detector with a biochemical flow cell. Elution with each solvent was continued until the detector response returned to base line. All columns were eluted with acetonitrile this solvent was preceded by 4.5 M NaCl/0.04 M HC1 and 0.04 M HC1 elutions on the MP-1 column and by 4.5 M NaCl and distilled water elutions on the MP-50 column. The aqueous column effluents were adjusted to pH 2 (MP-1) or pH 11 (MP-50) and then extracted three times with dichloromethane. The acetonitrile column effluents were saturated with NaCl to separate the water, which was extracted twice more with acetonitrile. Fifty percent aliquots of the processed organic solvents from each respective column were concentrated in Kudema-Danish evaporators to a final volume of about 10 mL (any remaining water was removed as the low-boiling azeotrope in the process) to give 25,000 1... 

Sample Concentration Experiments. A CLLE quality assurance blank was run by extracting 90 L of Milli-Q water with three CLLE samplers in a parallel configuration and concentrating the composited extract to 4 mL by Kudema-Danish evaporation. The 22,500-fold concentrate was analyzed by GC-flame ionization detection (GC-FID) and GC-MS. Thirty-two peaks were observed by using GC-FID analysis, but because of their low concentrations, only four contaminants were identified by GC-MS cyclohexene, 2-cyclohexen-1-one, n-butyl phthalate, and bis(2-ethylhexyl) phthalate. Cyclohexene is a solvent preservative that has been identified in commercial high-purity methylene chloride (16), and 2-cyclohexen-l-one is its air oxidation product. The phthalates are ubiquitous laboratory contaminants and have also been identified in commercial methylene chloride (17). 

Concentration can be performed under a gentle stream of inert gas or with a micro-concentration apparatus (e.g., Kudema-Danish sample concentrator, Supelco, or microconcentrator). This step generates volatile losses (mainly very volatile compounds that have a boiling point lower than the solvent) and will modify the quantitative ratio. 

After drying (removal of water), the extract is quantitatively transferred into a Kudema-Danish flask equipped with a concentrator tube and a Snyder column for sample concentration. The apparatus is placed in a water bath and ether is evaporated out. Use boiling chips in all heating operations. The volume of the extract is concentrated down to 1 to 2 mL. 

A 1-L aliquot, or any appropriate volume of accurately measured aqueous sample, is extracted with methylene chloride by liquid-liquid extraction. The extract is concentrated to 1 mL or any small volume on a Kudema-Danish setup. A florisil column cleanup may be necessary if the sample is dirty, or the presence of interferences is known or suspected or if A-nitrosodiphenylaminc is to be determined. 

Figure 2.13. Liquid-liquid extraction apparatus (a) separatory funnel and (b) evaporative Kudema-Danish sample concentrator. (Reprinted with permission from Ref. 46. Copyright 2002 Kimble/Kontes.)...

Goldberg and Weiner [46] used solvent-heavier-than-water, two-cycle liquid extractors to concentrate phenols at the pg L 1 level from water into dichloromethane. The non-aqueous solution containing the extract was concentrated by Kudema-Danish concentrators, and this was followed by gas chromatography. Overall concentration factors were around 1000 with efficiencies 23.1-87.1%. Determinations could be made with accuracy of only 15-20% because of solute losses during concentration. The range of concentration used was of the order of lpg L 1. 

Place 40 g of anhydrous sodium sulfate into a coarse, sintered-glass Buchner funnel, wash with about 20 mL of dichloromethane, and discard the washing. Dry the combined dichloromethane extract by passing it through the sodium sulfate bed in the Buchner funnel, and collect the extract directly in the Kudema-Danish evaporative concentrator. Wash the sodium sulfate bed with an additional 20 mL of dichloromethane, and collect the washing in the Kudema-Danish evaporative concentrator. 

Concentrator Use a Kudema-Danish concentrator having a 500-mL flask, available from Kontes Glass Co., Vineland, NJ (Catalog No. K-57000), or equivalent. 

Kudema-Danish (KD) Apparatus. 500 mL evaporating flask, 10 mL graduated concentrator tubes with ground glass stoppers, three ball macro-Synder column. 

The remaining extract was filtered through a bed of sodium sulfate, concentrated to low volume in a Kudema Danish evaporator, and then rinsed onto a column of activated Florisil. The Florisil column was eluted successively with 6 and 15% diethyl ether in hexane. Both eluates were concentrated to 0.2- to 0.3-ml. volumes to provide samples for identification by gas chromatography. The activity of the Florisil was checked by chromatographing a solution of hexane containing aldrin, heptachlor epoxide, dieldrin, endrin, and the n-butyl ester of 2,4-D. The column was judged acceptable when the first three compounds appeared in the 6% eluate and the last two in the 15% eluate. 

Concentrating Apparatus. Kudema-Danish concentrator, 250-ml. capacity. 

The combined extracts, contained over the sodium sulfate in the 125-ml. Erlenmeyer flask, are decanted quantitatively into a Kudema-Danish concentrating apparatus. Remove most of the hexane by heating on a fluidized sand bath at 100°C. Since all the hexane is not evaporated, the temperature of the extract will not exceed the boiling point of hexane. 

Apparatus. Separatory funnels, with Teflon stopcocks—125-ml. and 4-liter capacities Kudema-Danish evaporators with Snyder three-ball columns Immerex extractor, A. H. Thomas Cat. No. 1228-E chromatographic tubes—25 mm. o.d. x 300 mm. glass tube with sintered glass in bottom and Teflon stopcock. 

The volume of extract for the four types of sample ranged from about 125 to about 300 ml. Because of the high sensitivitv of the electron capture detectors, it was not necessary to concentrate the samples except for the soil sample which was taken on July 8, 1965. The extract in this case was condensed to about 5 ml. in a Kudema-Danish evaporator. 

There was no detector response at the dichlobenil retention time with any of the pre-treatment samples. Recoveries of 90% for soil, vegetation, and water and 83% for fish were established by adding known amounts of dichlobenil to unprocessed samples and then carrying these samples through the entire process. Recovery in the Kudema-Danish concentration step was 90%. 

Finally the sludge is extracted with 2x25 ml dichloromethane (DCM-3). The dichloromethane-extracts are combined and spiked with 50 pg each of the following deuterated internal standards toluene-ds, naphthalene-dio biphenyl-dio, phenanthrene-dio, pyrene-dio, crysene-d and phenol-dg. The extract is dried with sodium sulphate, and concentrated to 5 ml at 30 C using a modified Kudema Danish destination. When necessary the volume is further reduced to 1,0 ml under a gentle stream of nitrogen at 30°C prior to GC-MS analysis. 

To understand the requirements for Kudema-Danish evaporative concentration. 

Pre-concentration is concerned with the reduction of a larger sample into a smaller sample size. It is most commonly carried out by using solvent evaporation procedures after an extraction technique (see, for example, Chapters 7 and 8). The most common approaches for solvent evaporation are rotary evaporation, Kudema-Danish evaporative concentration, the automated evaporative concentration system (EVACS) or gas blow-down . In all cases, the evaporation method is slow, with a high risk of contamination from the solvent, glassware and blow-down gas. 

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