Aliquot liquid

Sample preparation Tablets. Grind 5 tablets to a fine powder, dissolve in 100 mL MeOH 0.5% acetic acid 1 1, filter (paper), inject an aliquot. Suppositories. Cut up 3 suppositories, add to 100 mL MeOH 0.5% acetic acid 1 1, heat at 40° until all the fat melts, shake, filter (paper), iiyect a 25 pL aliquot. Liquid formulations. Dilute 10 mL formulation to 100 mL with MeOH 0.5% acetic acid 1 1, iiyect a 25 pL aliquot. 

Sample preparation Capsules and Tablets. Leach 1 g of groimd capsule or tablet with 250 mL 0.4 mg/mL 2,5-dihydroxybenzoic acid in water, sonicate for 10 min, centrifuge at 2500 rpm for 5 min, inject an aliquot. Liquid formulations. Dilute 4-25 mL of the formulation to 250 mL with 0.4 mg/mL 2,5-dihydroxybenzoic acid in water, inject an aliquot. 

Hydrolysis of the ester is achieved by refluxing in aqueous N or 2N NaOH solution until the insoluble ester dissolves. The solution is then cooled, and the alcohol is extracted into a suitable solvent, e.g. ether, toluene or alcohol-free chloroform. The extract is dried (CaS04, MgS04) and distilled, then fractionally distilled if liquid or recrystallised if solid. (The p-nitrobenzoic acid can be recovered by acidification of the aqueous layer.) In most cases where the alcohol to be purified can be readily extracted fi-om ethanol, the hydrolysis of the ester is best achieved with N or 2N ethanolic NaOH or 85% aqueous ethanolic N NaOH. The former is prepared by dissolving the necessary alkali in a minimum volume of water and diluting with absolute alcohol. The ethanolic solution is refluxed for one to two hours and hydrolysis is complete when an aliquot gives a clear solution on dilution with four or five times its volume of water. The bulk of the ethanol is distilled off and the residue is... 

Dissolve in Et20, add quinol (500mg for 300mL), dry over Na2S04, filter, evaporate and distil under dry N2. It is a clear liquid if dry and decompose very slowly. In the presence of H2O traces of tributyl tin hydroxide are formed in a few days. Store in sealed glass ampoules in small aliquots. It is estimated by reaction with aq NaOH when H2 is liberated. CARE stored samples may be under pressure due to liberated H2. [J Appl Chem 7 366 1957.]... 

Radioactivity Analysis. Samples of urine, feces, and tissues were combusted to COo and analyzed for radioactivity (5). By using this method the recovery of radioactivity from samples spiked with C was 95 dt 5%. To determine the radioactivity expired as CO2, 5-ml aliquots of the solution used to trap the CO2 were added to 15 ml of a scintillation counting solution containing 4 grams 2,5-diphenyloxazole (PPO) and 0.1 grams l,4-bis-2(5-phenyloxazolyl)-benzene (POPOP) per liter of 1 1 toluene 2-methoxyethanol. Samples were counted for radioactivity in a Nuclear Chicago Mark II liquid scintillation counter. Counting eflSciency was corrected by the internal standard technique. 

These two methods produce different release profiles in vitro. Figure 5 demonstrates the release kinetics of BCNU from wafers loaded with 2.5% BCNU pressed from materials produced using these two methods. The wafers containing tritiated BCNU were placed into beakers containing 200-ml aliquots of 0.1 M phosphate buffer, pH 7.4, which were placed in a shaking water bath maintained at 37 C. The shaking rate was 20 cycles/min to avoid mechanical disruption of the wafers. The supernatant fluid was sampled periodically, and the BCNU released was determined by liquid scintillation spectrometry. The BCNU was completely released from the wafers prepared by the trituration method within the first 72 hr, whereas it took just about twice as long for the BCNU to be released from wafers... 

D-Xylulose 5-phosphate (ii-threo-2-pentulose 5-phosphate, XP) stands as an important metabolite of the pentose phosphate pathway, which plays a key fimction in the cell and provides intermediates for biosynthetic pathways. The starting compound of the pathway is glucose 6-phosphate, but XP can also be formed by direct phosphorylation of D-xylulose with li-xylulokinase. Tritsch et al. [114] developed a radiometric test system for the measurement of D-xylulose kinase (XK) activity in crude cell extracts. Aliquots were spotted onto silica plates and developed in n-propyl alcohol-ethyl acetate-water (6 1 3 (v/v) to separate o-xylose/o-xylulose from XP. Silica was scraped off and determined by liquid scintillation. The conversion rate of [ " C]o-xylose into [ " C]o-xylulose 5-phosphate was calculated. Some of the works devoted to the separation of components necessary while analyzing enzyme activity are presented in Table 9.8. 

High-performance liquid chromatographic determination Inject an aliquot (Vi) of the soil and crop samples into the HPLC system. 

SFE is used mainly for nonpolar compounds [e.g. polychlorinated biphenyls (PCBs)]. Typically, small aliquots of soil (0.5-10 g) are used for extraction. The extraction solvent is a supercritical fluid, most commonly carbon dioxide, which has properties of both a liquid and gas. The supercritical fluid easily penetrates the small pores of soil and dissolves a variety of nonpolar compounds. Supercritical carbon dioxide extracts compounds from environmental samples at elevated temperature (100-200 °C) and pressure (5000-10 000 psi). High-quality carbon dioxide is required to minimize... 

Control urine should be collected from individuals who have no apparent past history of exposure to the active ingredient. This control urine must be stored frozen until used for field fortification purposes. The urine is then thawed, shaken well, and a certain amount should be aliquoted into a small jar/bottle to use for field fortification. The active ingredient is then added to the urine using a 1-mL volumetric pipet, the solution is shaken well, and the sample is immediately frozen. Occasionally, the fortified sample can be left at room temperature or at some lower temperature in a liquid state to simulate field storage during collection of the urine sample. After leaving the sample at such temperatures for the prescribed length of time, the sample is immediately stored frozen. 

For liquid/liquid partitioning, sodium chloride and a mixture of cyclohexane and ethyl acetate are added to the homogenate. The mixture is again intensively mixed and allowed to stand until the phases separate. An aliquot of the organic phase is dried with sodium sulfate and concentrated. The concentrated residue is mixed with ethyl acetate and the same volume of cyclohexane. Remaining water is eliminated with a mixture of sodium sulfate and sodium chloride, and the solution is filtered. The extract is subjected to cleanup by GPC (Module GPC). 

Crop material is homogenized with acetonitrile-water (9 1, v/v). The crop extract is centrifuged and an aliquot is rotary evaporated to a small volume. The sample is subjected to a Cig solid-phase extraction (SPE) cleanup procedure. The concentrated eluate is subjected to liquid chromatography/tandem mass spectrometry (LC/MS/MS) analysis. 

Soil is extracted twice with methanol-1 N hydrochloric acid (3 1, v/v), centrifuging between each extraction. An aliquot of the combined soil extract is diluted with acidified (pH 1)5% (w/v) sodium chloride solution and subjected to liquid-liquid partitioning with dichloromethane. The dichloromethane extract is evaporated and the residue is dissolved in mobile phase prior to quantitation by LC/MS/MS. 

Inject an aliquot of the HPLC-ready sample solution into the high-performance liquid chromatograph. 

Milbemectin consists of two active ingredients, M.A3 and M.A4. Milbemectin is extracted from plant materials and soils with methanol-water (7 3, v/v). After centrifugation, the extracts obtained are diluted to volume with the extraction solvent in a volumetric flask. Aliquots of the extracts are transferred on to a previously conditioned Cl8 solid-phase extraction (SPE) column. Milbemectin is eluted with methanol after washing the column with aqueous methanol. The eluate is evaporated to dryness and the residual milbemectin is converted to fluorescent anhydride derivatives after treatment with trifluoroacetic anhydride in 0.5 M triethylamine in benzene solution. The anhydride derivatives of M.A3 and M.A4 possess fluorescent sensitivity. The derivatized samples are dissolved in methanol and injected into a high-performance liquid chromatography (HPLC) system equipped with a fluorescence detector for quantitative determination. 

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