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Freezing recovery methods

Pish silage prepared by autolysis of rainbow trout viscera waste was investigated as a substrate for the plastein reaction using pepsin (pH 5.0), papain (pH 6—7), and chymotrypsin (pH 8.0) at 37°C for 24 h (152). Precipitation with ethanol was the preferred recovery method. Concentration of the protein hydrolysate by open-pan evaporation at 60°C gave equivalent yields and color of the final plastein to those of the freeze-dried hydrolysate. [Pg.471]

Other information of the composite structure can also be obtained by studying the recovery behavior fi-om the stress softening effect. This is especially interesting in the composites made by the freeze-drying method (28), where the recovery curves of the CB composite lie above the G of the first strain cycle (Figure 13(b)). [Pg.102]

Figure 13. The composites were reinforced with 20 wt % filler and prepared by freeze-drying method (a) SSF composite (b) CB composite. Only T and o strain cycles are shown. R indicates the recovery curve after the samples were conditioned at 140 for 24 hours. Measured at 1 Hz and 140 C. (Reproducedfrom reference 28.)... Figure 13. The composites were reinforced with 20 wt % filler and prepared by freeze-drying method (a) SSF composite (b) CB composite. Only T and o strain cycles are shown. R indicates the recovery curve after the samples were conditioned at 140 for 24 hours. Measured at 1 Hz and 140 C. (Reproducedfrom reference 28.)...
Some more recent field techniques have focused on the location of the preparation of field fortification samples and have taken some of the responsibility for the preparation of the field fortification samples from the field personnel and placed them with the analytical laboratory. For example, it is becoming more common for the analytical laboratory to prepare air sample field fortifications in the analytical laboratory, freeze them, and ship them to the field for use in a frozen state. Whereas there may be some advantage to this technique in that the air tube fortification samples may possibly be fortified more accurately in the laboratory under controlled conditions than if done in the field, there are some inherent scientific problems with this method. First, one reason for the field fortification is to test the ruggedness of the field techniques of the researcher under extreme field conditions. Second, the act of freezing and thawing the sorbent matrix within the air mbe itself may have an impact on the recovery of the analyte from the air tube after exposing the sorbent to field conditions... [Pg.1014]

Mann and Mitchell [58] described a simple colorimetric method for estimation of (-D)-penicillamine in plasma. Blood containing 2-50 pg of penicillamine was mixed with 0.1 M EDTA solution in tromethamine buffer solution. 0.1 mL of this solution was adjusted to pH 7.4 and centrifuged. To a portion of the plasma was added 3 M HCL, the mixture was freeze-dried, and a suspension of the residue in ethanol was centrifuged. The supernatant liquid was mixed with tromethamine buffer solution (pH 8.2) and 10 mM 5,5 -dithiobis-(2-nitrobenzoic acid) in phosphate buffer solution (pH 7.0), the mixture was shaken with ethyl ether, and the absorbance of the separated aqueous layer was measured at 412 nm. The mean recovery was 60% (four determinations), and the calibration graph was linear for the cited range. [Pg.145]

In order to preclude this problem and the necessary frequent regeneration of the anion system s suppressor column, an ion chromatography exclusion scheme was utilized. Samples collected in a mine environment were reliably concentrated by freeze-drying and then analyzed on an ICE system with dilute hydrochloric acid eluent. The precision of the ICE method was experimentally determined to be 2.5% in a concentration range of 1 to 10 yg/mL. The accuracy was not independently determined but good precision and recovery yield confidence that measured values are within 5% of the true value. No interferences were observed in the ICE system due to strong acids, carbonic acid or other water soluble species present in mine air subject to diesel emissions. [Pg.610]

Extraction of fat by supercritical carbon dioxide was investigated as an important option for minimizing the expanded use of frequently flammable and carcinogenic solvents in food analysis. Unfortunately, the presence of moisture in foods has an adverse effect on the quantitative extraction of fat by supercritical fluid extraction (SEE). Hence, samples have to be lyophilized first. The total fat content of freeze-dried meat and oilseed samples was found to be comparable to values derived from Soxhlet-extracted samples (26). Besides, only small amounts of residual lipids could be recovered by an additional extraction of the SFE-extracted matrix by the Bligh and Dyer solvent extraction procedure. As far as the minor constituents are concerned, it was found that the extraction recovery ranged from 99% for PC to 88% for PA. Hence, Snyder et al. concluded that SFE can be used as a rapid, automated method to obtain total fat, including total phospholipids, from foods (26). [Pg.256]

Fig. 3.2.2. Activity recovery of LDH after freezing by three methods A, cooled in LN2 and transfered to a -40 °C freezer B, frozen on the shelves of the freeze-drier ramped from 25 to -40 °C at 0.5 °C/min C placed in a freezer at -40 °C. LDH concentration (1) 5 (2) 25 (3) 50 pg/mL (part of Figure 3 from [3.70])... Fig. 3.2.2. Activity recovery of LDH after freezing by three methods A, cooled in LN2 and transfered to a -40 °C freezer B, frozen on the shelves of the freeze-drier ramped from 25 to -40 °C at 0.5 °C/min C placed in a freezer at -40 °C. LDH concentration (1) 5 (2) 25 (3) 50 pg/mL (part of Figure 3 from [3.70])...
Thus upon comparing the economics of the two methods, embryos and sperm, it is very apparent that the freezing of embryos is considerably more expensive due to the need for more resources for example, with a C57BL/6 background, to produce 250 two-cell embryos for cryopreservation by IVF requires >15 females. If strains are never recovered or only recovered once or twice, then the bulk of this expense remains forever frozen. In contrast, cryopreserving sperm has a low initial cost as only few animals (1-3 males) and relatively little labor and materials are required (12). It is upon recovery from sperm by in vitro fertilization (IVF) that animals and labor are used, but then only the required number animals per recovery are used as the IVF process can be scaled to produce the desired number of offspring. [Pg.26]

Yandenburg et al. [92] compared extraction of additive Irganox 1010 from freeze-ground polypropylene polymer by pressurized fluid extraction (PFE) and MAE with reflux, ultrasonic, shake-flask, and Soxhlet extraction. PFE and MAE were faster than any conventional method with comparable extraction efficiency. The times to reach 90% recovery by PFE using propan-2-ol at 150°C and acetone at 140°C were 5 and 6 minutes, respectively. Reflux with chloroform was found to be the fastest method performed under atmospheric pressure with 90% recovery in 24 minutes. Reflux with cyclohexane propan-2-ol (1 1) required 38 minutes. Ultrasonic, shake-flask, and Soxhlet extraction required about 80 minutes (90%) extraction). The total sample preparation time for PFE was 15 minutes, MAE 28 minutes, and reflux with chloroform was 45 minutes. [Pg.178]

The assay has been validated and the results of validation demonstrate that the standard curve is linear over the concentration range of 100-2000 ng/mL. The assay is reproducible and accurate, with recovery of the analyte and internal standard in the range of 80-90 %. The analysis requires 0.5 mL of plasma and has a limit of quantification of 70 ng/mL. The stability of plasma samples stored at -20 °C has been demonstrated for up to 12 weeks. Autoinjector stability has been demonstrated for over 13 h and freeze-thaw stability has been demonstrated for 3 freeze-thaw cycles. The procedure has a sample throughput of at least 30 specimens per day. The assay meets the guidelines for bioanalytical methods validation for human studies (Shah et al. 1991). [Pg.642]


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