Freeze drying sample

Dried or freeze dried samples can be extracted with water-immiscible solvents such as EtOAc or diethyl ether. For quantitative extraction, dried samples are preferably rehydrated at different times for example, 5 to 10 min for dried mangoes, 30 min for lyophihzed red peppers and pasta. Rehydration is followed by extraction with acetone or MeOH. Bixin and norbixin from a mix dry powder of annatto and com can quantitatively be extracted with MeOH followed by acetone. In order to improve pigment recovery, extruded foods require pre-digestion with enzymes to liberate the pigment from the matrix. ... 

Figure 2. SDS-PAGE of culture supernatants. Freeze-dried samples were resuspended in distilled water, mixed with an equal volume of sampling buffer and heated to 100°C for 5 min. lOpl aliquots were applied to the gel. The right lane contains standards of Mr 14-66 kDa. Lanes 2, 3, 4 and 1 are increasing dilutions of the supernatant respectively.

Xanthans from several different sources were used in this study Xanthan samples A, B and C were kindly provided as freeze dried powder of ultrasonic degraded xanthan by Dr. B. Tinland, CERMAV, Grenoble, France. The molecular weights of these samples were determined experimentally in dilute solution by Dr. B. Tinland. Xanthan D was kindly provided as pasteurized, ultrafiltrated fermentation broth by Dr. G. Chauveteau, Institut Francais du Petrole, France. Xanthan E was kindly provided as a freeze dried sample from Dr. I. W. Sutherland, Edinburgh, Scotland. Xanthan F was obtained as a commercial, powdered material (Kelzan, Kelco Inc., a Division of Merck, San Diego CA.). Xanthan G was obtained as a commercial concentrated suspension (Flocon 4800, Pfizer, New York, NY)... 

The addition of water or the use of an aqueous solvent mixture is important for the extraction of other organic analytes from dry foodstuffs or dehydrated foods. It is particularly necessary in aiding the permeation of solvent through freeze-dried samples. 

Solutions of microgels from EUP and bifunctional comonomers are rather stable over weeks and months. However, on exposing freeze-dried samples of microgels from ECP of EUP and S to 02 or N2, insoluble fractions are formed which increase with exposure time and temperature. As insolubilization is prevented in... 

Soxhiet extraction of freeze-dried samples with toluene, Chromatographie clean-up quantification by means of GC-MS... 

In conclusion, we have demonstrated that high resolution TEM is a valuable complement to x-ray fiber diffraction analysis and chemical structural elucidation. Its application provided information about the organization of pectin in cell walls and in calcium-free gels. Using freeze-dried samples that were Pt/C replicated, we demonstrated tobacco pectin filaments in a gel to be of the same diameter as the filaments on the noncutinized lower epidermal surface of senescing Coker 319 tobacco leaves. These filaments were 7.1 3A and 4.6 4.8A, respectively, and roughly the same diameter, 7A, as fiber-diffraction modeled citrus pectin (32). Replicated... 

Calculation. Subtract the weight of the empty crucible from that of the crucible plus NDF to obtain the weight of NDF in 0.5 g sample. Divide by the sample weight and multiply by 100 to obtain the % NDF in the freeze-dried sample. Multiply this figure by 100/(100-moisture content) to obtain the % NDF in DM. Subtract the empty crucible weight from the weight of crucible plus ash and multiply by 100/weight of NDF to obtain the % ash in the NDF. 

Calculation. Draw a baseline on the chart under all the sample peaks by connecting the baseline from aspirating wash at the start, between trays and at the end. Read the concentration of the sample solutions by comparing the peak heights of the samples with the standards using a chart reader (see Chapter 1, Chart reader ). Divide the concentration in pg mb of soluble carbohydrate in the sample solution by 10 to get the % water soluble carbohydrate in the freeze-dried sample. Multiply by 100/(100 - % moisture) to give the percentage water soluble carbohydrate in the sample DM. 

In the case of samples collected from mine air, the bubbler solution was concentrated by freeze drying. Samples were transferred to wide mouth jars, frozen to -25°C and freeze-dried under 0.5 cm Hg vacuum in a Vacudyne, Inc. Pilot Freeze Dryer. Once reduced to dryness, 1 mL of distilled/deionized water was added to the samples. After shaking to ensure complete dissolution,... 

Bacterial mutagenesis tests have been conducted with distilled water solutions of the freeze-dried residues [concentrated up to 3000-fold (7)] and partially freeze-dried samples [concentrated 10-fold (49)]. High salt concentrations in such concentrates may cause toxicity problems in the bacterial tests. The use of dimethyl sulfoxide, methanol, or supercritical carbon dioxide to extract the organics from the freeze-dried residues for mutagenicity test purposes should be investigated. 

Freeze-Dried Samples. Solid Materials and Tissues. These are first cut into approximately 1-inch cubes, frozen on a Teflon cookie sheet in a freezer, and placed in 1200-ml. freeze-dry flasks to capacity. The flasks are attached to the freeze-dried (lyophilizer) manifold, the valves are opened to vacuum, and the flasks are evacuated. The water from the tissues is trapped on a condenser. The dry tissues (drying time about 2-3 days) are removed from the lyophilizer and compressed into thin-walled aluminum cans with a Carver Laboratory press fitted with a special die, at about 24,000 lb. pressure (total). From 150-250 grams of the dry material, representing 500-1000 grams of fresh tissue, can be packed into a single can. The cans are sealed with a hand sealer and set aside for counting. Samples can be removed from the cans at a later date for chemical analysis or beta-emitter analyses. 

The authors usually freeze-dry samples for convenience and analyze later with the cell walls and cell-wall fractions. 

For freeze-dried samples, extract the dry sample ( 0.3 to 1 g dry weight starting from 2 to 3 g fresh weight) with diethyl ether and apply the equations given for diethyl ether (UNIT F4.3). Extraction of freeze-dried plant material with diethyl ether is performed by grinding in a mortar. It is also possible to use 80% acetone or 100% methanol, but diethyl ether has proved to be an excellent solvent for quantitative extraction of chlorophylls and carotenoids from freeze-dried plant material. 

Add 3 ml of 100% acetone (for <200 mg fresh sample) or diethyl ether (for freeze-dried samples with low chlorophyll content) and grind with a pestle. 

Mix 10 g of ground freeze-dried samples (accurately weighed) with 100 ml of 80% aqueous methanol in a 500-ml Erlenmeyer flask. 

In this alternative procedure, absolute methanol rather than aqueous methanol is used to extract the polyphenolics from fresh plant material instead of freeze-dried samples. Raw plant material is washed, dried, and then immediately extracted. This protocol employs a blender to first macerate the plant material to increase the sample surface area for better contact of the solvent and the sample. 

Extraction (adapted from Bushway 1986 (369)) freeze-dried sample powder stirred in THF-H20-ACN. Extract centrifuged, supernatant collected and concentrated in a rotary evaporator, with added HC1, suspension centrifuged and pH adjusted with NH4OH to pH 10-11. Water bath at 70°C, 30 min. The precipitate collected and boiled in MeOH. Hot suspension filtered and evaporated. ACN-H20 added. 

Fractionation with organic solvents is mainly done to remove proteins, large peptides, and non-proteinaceous material such as fat. In a method developed by Harwalkar and Elliott (1971) and adopted by Lemieux et al. (1990), Puchades et al. (1990), and Visser et al. (1983), freeze-dried samples of cheese were extracted using methanol (to precipitate large peptides and proteins), chloroform (to remove fat), and water. The final extract... 

Organophosphorus types Plants Solvent extraction from freeze-dried sample GC with ECD - [70]... 

Figure 14.12. Quantification of carbohydrates and peptides in dissolved organic matter in tributaries of the Yenisei river (Siberia) by conventional wet-chemical methods (Kawahigashi et al., 2004) and Py-FIMS of freeze-dried samples.

Extraction and extract separation. The freeze dried samples were ground and extracted with chloroform for one hour at 55°C. Free sulfur was removed by percolating the extracts over an activated copper column. Resulting extracts were separated using thin layer chromatography (Merck precoated T.L.C. Silica-gel 60f-254) with cyclohexane as the eluting solvent. Three fractions were obtained an immobile polar fraction, an "intermediate fraction, and a saturated/unsaturated hydrocarbon fraction. 

FW = fresh weight DW = dry weight FDS = freeze-dried sample. cData obtained from bar graphs. 

IT = Italy PRC = People s Republic of China UK = United Kingdom. FW = fresh weight EDS = freeze-dried sample ns = not sped bed. Orange juice. 

The method of sample preparation to be used for a given analysis is governed by the nature and concentration of the analyte, the nature (solid or liquid) and type of matrix, the available sample amount, and also by the instrumental technique employed. Freeze-dried samples will require some form of digestion or dissolution in order to be analyzed by a classic atomic technique (i.e., using nebuliza-tion). Liquids might be analyzed by direct nebulization, but this is not always possible due to matrix interferences. Milk pretreatment may be necessary under such circumstances. 

The stability of SeMet and TMSe+ in freeze-dried oyster and in the enzymatic extracts stored at different temperatures (— 18, 4, and 20°C) was studied. The results obtained for the freeze-dried sample showed that SeMet and TMSe+ were stable for at least 12 months under all the conditions tested. However, Se species in the enzymatic extracts were only stable for 10 days if stored at 4°C in Pyrcx containers [99]. 

The methanol-to-water ratio in the extraction mixture is usually determined on the basis of the water content of the sample. Methanol alone is generally used if fresh, untreated samples are dealt with, because the natural water content (reaching even 90 percent m/m) in practice adds to methanol [109, 110] however, in some studies, nonaqueous methanol has used been also for freeze-dried samples [26, 111, 112]. The methanol-to-water ratio mostly chosen is around 1 1 v/v (40 60, 50 50, 60 40). However, also the 10 90 ratio is also used [100], not to mention cases where the full mixture scale from 0 to 100 percent methanol has been exploited [113, 114]. The study by Helgesen and Larsen [115], where a 10 percent (v/v) methanol mixture was used for the extraction of As species from carrots because of its antibacterial effect, is noteworthy. 

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