Original stock solution

Distribution coefficients were measured employing batch methods. The solution (ml) to clay (mg) ratios were aporoximate-ly as follows 1 5 attapulgite 1 60 montmorilIonite and 1 25 kaolinite. The solutions were brines (NaCl) buffered with pH 5 acetate solution. The original stock solution contained 3 M NaCl and 1 M Na acetate buffer. The lower [Na] solutions were made by... 

Incubate aliquots of uninfected cells in the presence of the compounds at the appropriate concentrations for 72 h in 5% C02. See Subheading 3. for making up stock solutions. To find the maximum concentration tolerated by the uninfected cell cultures it may be necessary to increase the concentration of the original stock solutions by 10- or 100-fold. 

Because all the solute comes from the original stock solution, we can conclude that... 

A 50.0-mL portion of a stock solution was diluted to 500.0 mL. If the resulting solution was 2.00 M, what was the molarity of the original stock solution ... 

Two sets of T jump runs were taken at 20°C (final temper= ature) the first one was taken at constant dye concentration (D = 7x10 eq./ )( ) and varying PSS concentration (P) in the P/D ratio range 10 to 1000. The second set was taken at constant P/D ratio (P/D = 22) for various dilutions of an original stock solution. The experimental results are shown in figure 3 A and B. 

From the stock solution, obtain an aliquot which contains the amount of liquid originally needed. This is determined by the following proportion ... 

To make a dilution, you simply add a small quantity of a concentrated stock solution to an amount of pure solvent. The resulting solution contains the amount of solute originally taken from the stock solution but disperses that solute throughout a greater volume. Therefore, the final concentration is lower the final solution is less concentrated and more dilute. 

Table 5 Inhibition of Human Cytochrome P450-Mediated Metabolism by Aliquots of Aqueous Extracts of Herbal Tea and Bulk Spice (Country of Origin) (25mg/mL Stock Solutions)...

Stock solutions the original solutions prepared directly by weighing the reference standard of the analyte and dissolving it in the appropriate solvent. Usually, stock solutions are prepared at a concentration of 1 mg/mL in methanol and kept refrigerated at -20°C if there are no problems of stability or solubility. 

Sodium acetate buffer 0.1 M, pH 5.0 Dilute 1 M sodium acetate stock solution (81.04 g/1) with H20 and adjust to pH 5.0 with acetic acid. Make up to ten times the original volume with H20. 

The reservoir was filled with 3-4 L of the stock solution (original), and the entire system was rinsed thoroughly with approximately 1 L of solution, which was discarded. The volume of the cells, tubing, etc. was estimated to be approximately 200 10 mL, whereas the surge tank retained approximately 100 mL of fluid. Initially the concentration of the stock solution was determined to verify whether any loss had occurred during storage. After the run was started, the system was equilibrated by collecting at least 10 mL of the permeate from the slowest membrane, and the solution left in the reservoir was then called the feed solution . The actual volume of the feed solution was determined at time... 

It is neither necessary nor desirable to prepare large volumes of the working standard solution since there is always a question of the long-term stability of such solutions. Likewise, in most cases, the consumption of standard solution is in microliter units therefore, if it is desired to retain a stock solution, it should be the more concentrated original solution in small volume carefully kept in a freezer. From this, convenient small portions of working standard solutions can be prepared as needed. 

NOTE In the original Mytol formula it was recommended to use 60.0 grams of sodium sulfite to increase sharpness. However, the effect was insignificant and the result was reduced shelf-life for the stock solution. 

In their original paper, Cohen et al. (1980) also recommended that neither the aliquots taken from a particular serum pool nor the amount of IS added should be equal. Thus the intensity ratios observed usually differ, as do the pairs of calibration mixtures needed for bracketing them. This minimizes the effect of any error in a single calibration mixture, but complicates manipulations and calculations. When larger series of the same serum pool have to be analyzed, as for our BCR work (cf. Section 4.4), we prefer to prepare the standards from several independent stock solutions, and to keep the amount of internal standard constant for both samples and calibration standards. 

The ethanolic stock solution of trans-cannabidiol 10, originally analyzed by gas liquid chromatography TGLC) (column 3% OV-17 on 100-120 mesh Gas Chrom Q,... 

Concentrated (e.g. 5 x) buffer stock solutions are made up, and diluted for use both in the gels and reservoirs. The following buffers originally employed by Loening (1967) are commonly used, but numerous others are equally suitable ... 

Sample Solutions. The urine sample solutions all originated from one composite urine sample. The latter was made by combining 150-mL aliquots of the entire first-morning voids of 16, presumably healthy, male subjects. Aliquots of the composite were used to prepare three sets of sample solutions as indicated in Table IV. The solutions in each set were "spiked with internal reference elements and with appropriate volumes of multielement stock solution to make a (multiple) standard addition series (12). The final gallium and yttrium internal reference-element concentrations were 1.0 and 0.1 mg/L, respectively, for both the reference and standard addition solutions. The added analyte concentrations for both the reference and standard addition solutions were 0, 2, 4, 10, and 20 times the approximate "normal analyte concentrations for urine, as listed in Table II. 

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