Charcoal spiked

Fiber type and working conditions for the HS-SPME method are reported in Table 5.13. It is worth mentioning that it is necessary to calibrate the method every time the fiber is changed using a wine pre-treated with charcoal, spiked with different quantities of standard solutions, as established in the calibration method proposed (Fedrizzi et al. 2007a 2007b). 

Analytical Desorption Recovery. Spiking with known amounts of JP-4 and PD-680 was done in two ways. First, known amounts were injected into the center of the front portion of the charcoal tube (SKC, NIOSH approved charcoal tubes). Secondly, the vapor monitors (3M 3500 organic vapor monitors) were spiked by injecting known amounts through the center elutriation port of the monitor cap, onto a piece of filter paper placed between the elutriation cap and the diffusion plate of the vapor monitor (2). The filter paper was removed after 24 hours and analyzed Tor any unvaporized portion. The monitor was analyzed as described earlier. The spiking was done at three levels, roughly corresponding to 0.5X, 1.0X, and 2.OX the occupational standard of these hydrocarbons, for a 10 liter air volume. 

The report (5) on the study recommended that a less active charcoal be tested. A literature survey did not yield any conclusive evidence for successful collection by recovery from alternative sorbents. On the basis of the little information available, we selected petroleum charcoal and three porous polymers to test (petroleum charcoal is less active than coconut charcoal). All the porous polymers were based on aromatic monomers, and they should be good collectors for nonpolar aromatics. Aliquots of 113 pg diphenyl were spiked onto these sorbents, and the samples were desorbed with various solvents. The results are given below. 

Techniques of Purification. The purification techniques have included column and batch adsorption, extraction, dialysis, and column and paper chromatography. Liberal use was made of the fact that the gibberellate anion is not soluble in ethyl acetate, whereas the free acid is soluble, and that charcoal will adsorb GA3 from aqueous solutions but release it with acetone (26). As a rough rule, preliminary concentration by a factor of about 105 was necessary before significant use of paper chromatography could be made. For kudzu vine and pinto bean, a known amount of GA3 was added to an aliquot of the plant extract and taken through the same procedure as the initial extract. These controls are subsequently referred to as "spiked extracts, to differentiate them from the initial or "natural extract. 

The charcoal tube samples were desorbed with 2 ml. of chrcanatoquality carbon disulfide (CS2), dispensed with an automatic pipette, in vials with Teflon-lined septum caps. Vials were agitated for 30 minutes on an SKC developing vibrator equipped with an automatic timer. Standards and spiked charcoal tubes with known amounts of solvent were prepared with Hamilton syringes. A Varian Model 1800 Gas Chromatograph equipped with a flame ionization detector was used to analyze the CS2-desorbed samples. Two GC colums were used ... 

HPLC-DA-UVD was used for confirmation of the presence of HAA from Table 2.A-B, extracted from charcoal-grilled meat by the Gross and Griitter method (Section III.A.5), in parallel with ELD. Due to the complexity of the matrix, the standards addition method was applied, spiking with authentic analytes. The only HAA found in concentrations over the LOD were benz[a]acridine (17), MelQ (25b) and MelQx (26a)139. After suitable extraction and cleanup from fried meat, compound 23a was determined by HPLC-FLD (Xcx = 316 nm, = 370 nm) other HAA (Table 2.B) also present in the sample... 

Chlorinated phenolic compounds in air-dried sediments collected downstream of chlorine-bleaching mills were treated with acetic anhydride in the presence of triethylamine. The acetylated derivatives were removed from the matrix by supercritical fluid extraction (SEE) using carbon dioxide. The best overall recovery for the phenolics was obtained at 110°C and 37 MPa pressure. Two SEE steps had to be carried out on the same sample for quantitative recovery of the phenolics in weathered sediments. The SEE unit was coupled downstream with a GC for end analysis . Off-line SEE followed by capillary GC was applied in the determination of phenol in polymeric matrices . The sonication method recommended by EPA for extraction of pollutants from soil is inferior to both MAP and SEE techniques in the case of phenol, o-cresol, m-cresol and p-cresol spiked on soil containing various proportions of activated charcoal. MAP afforded the highest recoveries (>80%), except for o-cresol in a soil containing more than 5% of activated carbon. The SEE method was inefficient for the four phenols tested however, in situ derivatization of the analytes significantly improved the performance . 

Recoveries also depend on the wine matrix white and red wines differ for volatiles and polyphenols, and contents of alcohol and sugars. For quantitative analysis, internal standards have to be spiked to the sample in suitable concentration, such as dimethyl sulfide-d6 (d6-DMS) 25 pg/L, dipropyl disulfide (DPDS) 25 pg/L, 4-methylthiazole (MT) lOpg/L, and 3-(methylthio)-l-hexanol (MTH) 50pg/L. A white wine matrix can be used [e.g., 10% v/v ethanol, sugar content <4g/L, and a polyphenolic content of 115mg/L expressed as (+)-catechin] for preparation of standard solutions to calculate the calibration curve for analytes, containing total S02 corrected to 100 g/L and previously treated twice with charcoal 3 g/L to remove sulfur and less polar volatile compounds (higher alcohols are not removed). 

Several separation and preconcentration methods for analysis of 3-MH, 3-MHA, and 4-MP, were reported (Tominaga et al., 1998 Schneider et al, 2003 Mateo-Vivaracho et al., 2007). Recently, HS-SPME-GC/MS method with limits of quantification (LOQs) of a dozen ng/L (close to the sensory thresholds of 3-MH and 3-MHA) was proposed (Fedrizzi et al., 2007b). This method does not include determination of 4-MP because the sensory threshold of this compound in wines ( 0.4 ng/L) is too low. The method has to be calibrated using a white wine pretreated with charcoal, corrected to a total S02 100 g/L, and spiked with different quantities of standard solutions. The optimized HS-SPME conditions (temperature, sampling time, solution pH) are reported in Table 5.6. 

The evolved gases are spiked with a known amount of 99+% He (obtained from Oak Ridge National Laboratory) and cryogenically concentrated on charcoal held at 16 K. After transfer to the charcoal is complete, the charcoal is warmed to 37 K, and the now purified He is admitted into a quadrupole mass spectrometer. The " He/ He ratio is measured in static mode over a period of about two minutes, after which the entire system is pumped. 

Ethylene oxide was spiked onto charcoal tubes and the following recovery data was obtained. 

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