Vial equilibration method

Tissue blood partition coefficients for total MEHP (ionized and nonionized) were determined experimentally using a vial-equilibration method with correction for pH (Table 3-5). 

Rosier JA, Van Peteghem CH. 1987. Determination of toxicologically important partition coefficients of carbon disulfide by means of the vial equilibration method. Br J Ind Med 44 212-213. 

Tissue blood partition coefficients for total and nonionized mono- -butyl phthalate were estimated from their n-octanol water partition coefficients (Kq,), using the approach reported by Poulin and Krishnan (1995). Tissue blood partition coefficients for total mono- -butyl phthalate (ionized and nonionized) were determined experimentally using a vial-equilibration method with correction for pH (Table 3-4). 

The vial equilibration method is the most common in vitro method for determining partition coefficients for volatile or semivolatile materials and has been used most successfully for volatile organic solvents (Gargas et al., 1988). Tissues are harvested from the species of interest and incubated with the test compoxmd imtil equilibrium is reached between the tissue and the headspace in the vial. The blood/air or tissue/air partition coefficients are given by the ratio of the concentrations of the chemical in the blood or tissue relative to its concentration in the headspace. Tissue-blood partition coefficients are calculated from the respective tissue/air and blood/air values. A number of operational equations have been derived to calculate these ratios xmder specific experimental conditions. Time to steady state is critical and should be optimized for the test compoxmd. Metabolism of the compound in exposed tissue samples must be controlled. Analysis is performed by gas chromatography in a verified linear range. Human tissues can be obtained from tissue bank organizations to provide species specificity to models developed with human data. To estimate... 

The fifth major improvement was to use a fast generic gradient method for the analysis of the samples, which usually takes place in an overnight run of. sample vials from 24 compounds. The fast generic HPLC methods have been discussed in Chapter 2. The method applied here was a 3.5 min gradient from 0 to 95% acetonitrile using a Supelcosil-ABZ 30 x 4.6 mm column with a 1.5 ml/min flow rate. Together with the re-equilibration time the cycle time for each sample was 7.5 min. 

Sample set or sequence method Controls and documents parameters of autosampler and sample/standard information Injection sequence vial, inject volume, injections, run time Functions inject samples, equilibrate, calibrate, quantitate Standard/sample info name, amount, sample weight, label claim, level... 

The molar mass of a newly synthesized organic compound was determined by the method of isothermal distillation. In this procedure two solutions, each in an open calibrated vial, are placed side by side in a closed chamber. One of the solutions contained 9.3 mg of the new compound, the other 13.2 mg of azobenzene (molar mass 182). Both were dissolved in portions of the same solvent. During a period of three days of equilibration, solvent distilled from one vial into the other until the same partial pressure of solvent was reached in the two vials. After this there was no further net distillation of solvent. Neither of the solutes distilled at all. The volumes of the two solutions at equilibrium were then read on the calibration marks of the vials. The solution containing the new compound occupied 1.72cm and the azobenzene solution occupied l.02cm. What is the molar mass of the new compound The mass of solvent in solution may be assumed to be proportional to the volume of the solution. 

Alternatively, a direct-immersion SPME method with DVB/CAR/ PDMS fiber (50/30 pm, 2 cm length) has been proposed. An aliquot of 15 mL of wine is transferred into a 20-mL vial and equilibrated at 30 °C for 5 min, then the fiber is immerged into the solution for 30 min under stirring. The fiber is then desorbed into the GC injection port at 250 °C (Fan et al., 2007). 

In Chapter 18, we described solvent extraction and solid-phase extraction sample preparation methods, which are applicable to GC analyses as well as others. A convenient way of sampling volatile samples for GC analysis is the technique of head-space analysis. A sample in a sealed vial is equilibrated at a fixed temperature, for example, for 10 min, and the vapor in equilibrium above the sample is sampled and injected into the gas chromatograph. A typical 20-mL glass vial is capped with a silicone rubber septum lined with polytetrafluoroethylene (PTFE). A syringe needle can be inserted to withdraw a 1-mL portion. Or the pressurized vapor is allowed to expand into a 1-mL sample loop at atmospheric pressure, and then an auxiliary carrier gas carries the loop contents to the GC loop injector. Volatile compounds in solid or liquid samples can be determined at parts per million or less. Pharmaceutical tablets can be dissolved in a water-sodium sulfate solution... 

Other physical tests may allow routine in-place evaluation of the microbiological integrity of vials. Headspace gas analysis is one such method. Many sterile products are held under nitrogen or some other gas in vials. The gas content of the headspace should, with a perfect seal, remain constant over time rather than becoming equilibrated with the atmosphere under a less than perfect seal. This type of analysis is amenable to chemical methodology and is likely done routinely in pharmaceutical production for reasons other than evaluation of microbiological integrity. 

Polydimethylsiloxane rods (1 mm X 10 mm) are an effective sorbent for PAHs from aquatic solutions.Each rod is placed in a vial with only 15 ml of sample and shaken for 3 h. The rods are then extracted with 100 ml of ACN H20 (4 1, v v) with 10 min of sonication prior to analysis. When HPLC-FLD is utilized for analysis, recoveries of 62 to 97% were obtained with limits of detection of 0.1 to 1.2 ng 1 when a total of four desorptions were combined. The method was applied to the semiquantitative screening of scrubber dust slurry from copper processing. Further quantitation by pressurized liquid extraction-HPLC-FLD showed that the concentration of B[k]F and PHN were 8.9 mg kg and 135.6 mg kg respectively. Since the PDMS rod is thicker than the PDMS coating on typical stir bars, longer equilibration times are required, yet the rods are inexpensive and disposable. 

Before analysis, the bacterial cultures should be transferred into standard 20 ml headspace vials and sealed with PTFE-lined Teflon caps to equilibrate the headspace. Sample handling is a critical step affecting the analysis by E-nose. The quality of the analysis can be improved by adopting an appropriate sampling technique. To introduce the volatile compounds present in the headspace (HS) of the sample into the E-nose s detection system, several headspace sampling techniques have been used in E-nose. Typically, the methods of headspace sampling (Ayoko, 2004) include static headspace (SHS) technique, purge and trap (P T) technique, stir bar sorptive extraction (SBSE) technique, inside-needle dynamic... 

Kapoulas, 1962). In brief, this method is based on polar and neutral lipids different solubility in pre-equilibrated petroleum ether and ethanol (87%). Polar lipads were soluble in ethanol while neutral lipids were soluble in petroleum ether. The obtained lipad fractions were weighed and stored under nitrogen in sealed vials at -20 °C until used - after a short period of time - for the biological assay. 

To conduct a water sorption study, the product was stored in desiccators with solid salt or saturated salt solutions for 48 h of equilibration at an ambient temperature (Figure 8). The salts included phosphorus pentoxide, lithium chloride, potassium acetate, magnesium chloride, potassium carbonate, and sodium chloride, which generated relative humidities of, approximately, 0, 11, 23, 33, 43, and 75%, respectively. The vials were sealed immediately after equilibration. The moisture in the lyophilized product was determined by the Karl Fischer method. 

Headspace methods are used extensively for the determination of residual monomers and other residues in polymer compositions after dissolution or dispersion in a suitable solvent and equilibration in a sealed vial at constant temperature prior to chromatography of the headspace gas. For samples in the form of fine powders or thin films, the technique can be applied directly to the solid and liquid samples. (Tables 5.2 and 5.3). 

Marsili compared SPME and dynamic headspace (DH) GC/MS techniques for the analysis of light-induced lipid oxidation products in milk (4). In the SPME method, 3 g of milk (2% milkfat) and 4-methyl-2-pentanone internal standard (10 jL of a 20 ppm solution in methanol) were placed in a 9-mL vial and capped. A 75- j,m Carboxen-1006/PDMS fiber was inserted into the headspace above the milk sample. Hie Carboxen/PDMS fiber has a combination of micro-, meso-, and macro-pores ranging from 6 to 50A. The volatile flavor compounds that are the best indicators of light-induced oxidation in milk are pentanal, hexanal, and dimethyl disulfide. The Carboxen/PDMS fiber was selected for this study because it is well suited for the analysis of low-molecular-weight volatiles. Adsorption of volatiles from the milk onto the SPME fiber was conducted at 45 C for 15 min with stirring. The sealed vial was allowed to equilibrate for 2 min at 45 C before the SPME fiber was inserted. 

---