Standard stock solutions

Lead caprate. Prepare a standard stock solution by dissolving 0.1323 g of the solid in 2 mL of naphthenic acid with warming. Add 20 mL of 4-methylpentan-2-one (methyl isobutyl ketone), cool and then make up to the mark in a 100 mL graduated flask with more of the ketone. 

Prepare a fresh set of protein standards by diluting the 2.0 mg per ml BSA stock standard (stock solution) as shown in Table 14.2. There will be sufficient volume for three replications of each diluted BSA standard, if necessaiy. 

A standard stock solution of sirolimus was prepared in methanol. Controls and standard working solutions were prepared by spiking blank whole blood with the stock solution. Standards, controls, and patient whole blood (10 fi. ) were transferred to 1.5 mL polypropylene tubes, mixed with 40 fiL of 0.1M zinc sulfate solution, precipitated with 100 fiL of methanol containing the IS (2 fig/L), vor-texed vigorously for 5 sec, and centrifuged at 10,500 g for 5 min. Supernatants were collected and assayed. The injection volume was 20 fiL. The retention times of sirolimus and ascomycin were 0.93 and 0.89 min, respectively. The total run time was 2.5 min. Representative MRM chromatograms of a patient sample are shown in Figure 11.6. 

Since certified reference materials for seawater nutrient analysis are currently unavailable, individual laboratories must prepare their own standard solutions for instrument calibration. Standard stock solutions are prepared at high concentrations (mM) so that they can be used for months without significant alterations in concentration. Working low-concentration standard solutions are unstable and need to be prepared daily by diluting stock solutions with distilled water or low-nutrient seawater. In this case, the accuracy of nutrient analysis at a given laboratory is highly dependent upon the accuracy of the daily preparation of the calibration solutions. 

Analysis was carried out by difference spectrophotometry. A one-point standard calibration for the determination of aspirin in dextropropoxyphene compound capsules was prepared by adding a known amount of aspirin to the sample from a standard stock solution. Stated content in the capsules ... 

The following standard stock solutions were prepared in order to calibrate the instrument for sodium and potassium ... 

The correlation coefficient, y-intercept, and slope of the regression line should be included. A plot of the data should be included. For the establishment of linearity, a minimum of five concentrations are recommended. It may be demonstrated directly on the active substance (by dilution of a standard stock solution). 

Standard stock solutions of formate anion were prepared from reagent grade sodium formate. Standard solutions of other organic anions were prepared for assessment of potential interferences. Injections of 3 mL were made to fill a sample loop of 100 yL volume. 

Another approach is to prepare a stock solution of high concentration. Linearity is then demonstrated directly by dilution of the standard stock solution. This is more popular and the recommended approach. Linearity is best evaluated by visual inspection of a plot of the signals as a function of analyte concentration. Subsequently, the variable data are generally used to calculate a regression line by the least-squares method. At least five concentration levels should be used. Under normal circumstances, linearity is acceptable with a coefficient of determination (r2) of >0.997. The slope, residual sum of squares, and intercept should also be reported as required by ICH. 

Calculation of concentration of standard stock solution in miligram/mL... 

Stable isotope internal standard stock solutions ... 

Pentadecanoic acid (PDA internal standard), stock solution 1 mg/ml in methanol. Dissolve 100 mg of PDA in 100 ml of methanol in a volumetric flask. Store refrigerated. Stable for 1 month. 

Internal standard stock solution weigh 33 mgofthe 18-methyl-C19 0 methylester and dissolve it in 50 ml of chloroform (approximately 2 mmol/1, store at 6°C). 

Standard stock solution in MeOH then diluted with mobile phase Sample dissolved in ACN then with water then with mobile phase LOD 0.12 /ig/ml LOQ 0.39 g/ml Rec 99.62% [31]... 

Standard Stock Solution 1 Transfer about 25 mg of benzoic acid reference standard, accurately weighed, to a 250-mL volumetric flask, add 5.0 mL of Stock Solution, dilute with Mobile Phase to volume, and mix. 

Standard Stock Solution 2 Dissolve an accurately weighed quantity of mandelic acid reference standard (previously dried in vacuum at 75°C for 4 hours) quantitatively in Mobile Phase to obtain a solution having a known concentration of about 5 mg/mL. 

A sample is diluted in an appropriate volume of internal standard stock solution and an aliquot of the sample is injected into a gas chromatograph/mass spectrometer monitoring m/e 349 and 351. The peak areas of the TPTM and internal standard are integrated and expressed as the ratio of TPTM -Internal Standard and the ratio of those areas respectively are used to construct a standard curve. The amount of TPTM present is then calculated from the standard curve. 

If the standard stock solution is delivered from a centralized stock solution the throughput can be increased significantly. Solubility obtained from organic stock solutions leads to kinetic solubility data (see also chapter 1.2). 

Bevan introduced a high-throughput alteration of the method. He uses 10 mM DMSO stock solutions for a precipitation assay. In many biological assays 10 mM DMSO stock solutions are the standard stock solution, from which aliquots are added to the various assays. 10 mM DMSO stock solutions are readily available and the sample preparation can be minimized. 

A solution with the concentration of 1.5 pM paclitaxel in methanol-water 1 1 was prepared by dilution of the internal standard stock solution in order to obtain an internal standard working solution. 

The internal standard stock solution was diluted with methanol to a working concentration 1 mg/L. 

Standards stock solution 20 ng/ml Apidra in insulin free human serum standard matrix insulin free human serum... 

Internal Standard Stock Solution Transfer 100.0 mg of 95% M-tricosane (obtainable from Chemical Samples Co.) into a 10-mL volumetric flask, dissolve in and dilute to volume with M-heptane, and mix. 

Diluted Standard Preparations Pipet 0.1, 0.25, 1.0, 2.5, and 5.0 mL, respectively, of the Stock Standard Preparation into five 10-mL volumetric flasks. Pipet 0.25 mL of the Internal Standard Stock Solution into each flask, dilute each to volume with methylene chloride, and mix. These solutions contain, respectively, 20, 50, 200, 500, and 1000 xg/mL of each toluenesulfonamide, plus 250 pig of M-tricosane. 

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