Field recovery

Field recovery samples are an important part of the quality control in DFR studies. Field fortifications allow the experimental data to be corrected for losses at all phases of the study from collection through sample transport and storage. Fresh laboratory fortifications monitor losses due to the analytical phase. This section details how the field recovery process was handled in the oxamyl tomato DFR study. 

Another consideration when planning field fortification levels for the matrices is the lowest level for fortification. The low-level fortification samples should be set high enough above the limit of quantitation (LOQ) of the analyte so as to ensure that inadvertent field contamination does not add to and does not drive up the field recovery of the low-fortification samples. Setting the low field fortification level too low will lead to unacceptably high levels of the analyte in low field spike matrix samples if inadvertent aerial drift or pesticide transport occurs in and around where the field fortification samples are located. Such inadvertent aerial drift or transport is extremely hard to avoid since wind shifts and temperature inversions commonly occur during mixer-loader/re-entry exposure studies. 

Low levels of 3,5,6-TCP were also observed in pre-exposure urine from most of the field workers. These 3,5,6-TCP levels were subtracted from urine field recovery samples and were used to correct levels of 3,5,6-TCP found in the post-exposure urine samples from these same workers. This procedure was necessary to calculate the amount of 3,5,6-TCP in the urine that was attributable to the exposure period. 

Table 5 presents data on field spike recoveries. Recoveries of chlorpyrifos from "low" spiked substrates in the California studies ranged from 62.5 to 126%, and recoveries of chlorpyrifos from "high" spiked substrates ranged from 93.7 to 133%. In the Florida, Arizona, and Michigan studies, all recoveries ("low" and "high") ranged from 61 to 158%. The field recoveries cited above were found to be reasonable and within the range of field recoveries seen in many worker exposure studies. 

Measurement bias is often called recovery , which can be expressed as a ratio (R), or a percentage (%R) and can be greater or less than 100%. In some fields of measurement, recovery refers to the amount of added (spiked) analyte recovered during analysis (equation (4.11)). In other fields, recovery is taken as an estimate of the proportion of the total analyte (native plus any added spike) present in a sample that is measured (recovered) by the method. The relationship between recovery and bias is shown in equation (4.12) ... 

Fig. 4. The HNCO-TROSY experiment for recording solely interresidual 1HN, 15N, 13C correlations in 13C/15N/2H labelled proteins. All 90° (180°) pulses for the 13C and 13C spins are applied with a strength of 2/ /l5 (p/ /3), where 2 is the frequency difference between the centres of the 13C and 13Ca regions. All 13Ca pulses are applied off-resonance with phase modulation by Q. A = 1/(4/hn) Tn = l/(4/NC ) S = gradient + field recovery delay 0 < k < TN/z2,max- Phase cycling i = y 4>2 = x, — x + States-TPPI 03 = x 0rec = x, — x.

Fig. 14. SeqHNCA-TROSY experiment for establishing sequential 1HN(i), 15N(i), 13Ca(i— 1) correlations in 13C/15N/2H enriched proteins. Durations of transfer delays A = 1/(4/Hn) 2Ta = 20-27 ms, depending on rotational correlation time of protein 2Tc = 5-7 ms S = gradient + field recovery delay 0 < k < Ta/t2,max- Phase cycling i = y (j>2 = y, — y + States-TPPI 0 = x 0ret. = x, — x. Semi-selective decoupling of 13C spins is attained using a SEDUCE-1 decoupling sequence.95...

Fig. 19. Pulse scheme of the MP-HNCA-TROSY experiment. Delay durations A = 1/(4/hn) 2T a = 27 ms 2Ta= 18-27 ms 2TN = 1/(2JNC-) <5 = gradient + field recovery delay 0 < k < Ta/t2,inax- Phase cycling scheme for the in-phase spectrum is 0i = y 02 = x, — x + States-TPPI 03 = x 0rec = x, — x 0 = y. For the antiphase spectrum, f is incremented by 90°. The intraresidual and sequential connectivities are distinguished from each other by recording the antiphase and in-phase data sets in an interleaved manner and subsequently adding and subtracting two data sets to yield two subspectra.

Sustained commercial application, however, did not occur until 1997, when Zheng et al. (7) described the successful stripping of oxygen from water used in secondary oil field recovery. In 1999 Trent et al. (8,9) introduced the first commercial application involving simultaneous absorption, reaction, and stripping. Both of these involve gas/liquid contact using a woven wire screen for the rotor internals. 

Removal of volatile components from the liquid phase to a gas phase has been the object of much study in RPB devices. One of the early successful applications was oxygen removal from water for use in secondary oil field recovery and boiler water feed (7). The oil field application demonstrated oxygen removal from 6-14 ppm to less than 50 ppb in both 50-T/h and 300-T/h RPBs using natural gas for stripping. The packing had 92% porosity and 500-m2/m3 volumetric surface area... 

Data are assigned to one of five classes, A through E, based on the results of experiments to determine the recovery of the analyte from fortified samples. Data from the three kinds of recovery experiments mentioned previously (laboratory recovery, storage stability and field recovery) are used to classify the exposure data. This is described in Table 5.1 (PHED, 1992). 

Data grade Laboratory recovery (%) CV for laboratory recovery Field recovery (%) Storage stability (%) Data corrected for ... 

D E 60-120 < 33 Field recovery, if available if not, then storage stability if not, then laboratory recovery Does not meet above criteria ... 

If a recovery of 90% or greater is obtained, no correction (based on field recovery) of the data is necessary. 

Interpretation of Residues Present Below the Limit of Detection Corrections for Incomplete Field Recovery 363 Characterization of Dissipation Kinetics 363 Outliers and Atypical Observations 364... 

Harmonized guidance for specific data analysis issues (i.e. corrections for incomplete field recovery, interpretation of residues present below the limit of detection, guidance for interpretation of outliers and atypical observations). 

Field recovery Data generated to determine the loss of analyte from sample-collection devices fortified in the field, when subjected to the same environmental conditions (e.g. temperature, light, relative humidity, wind, etc.) and duration as field-exposure samples (OECD, 1997 Norman, Ch. 10). 

Only recently has the problem of the loss of pesticide from patches used In the field been addressed ( ). Many studies do not report laboratory or field recovery data for sampling substrates or comment on correction for recovery of the data (,9). Serat ( ) found that cotton gauze retained only 30% of extractable parathlon and 70% of extractable dlcofol under field conditions. He concluded that In the absence of adequate controls to determine the quantity of chemical lost from the fabric collectors there Is no assurance that the extracted depositions represent anywhere near the actual values. This factor seriously limits the usefulness of many older exposure studies. New techniques using fluorescent markers (10) are promising and will undoubtedly lead to more quantitative estimates of contact exposure. 

Enhanced oil recovery (EOR) aims at increasing the oil fields recovery yield thanks to high pressure injection of gaseous carbon dioxide. This leads to maintaining high pressures in the reservoir and to improving oil displacement. When the oil reaches the surface, carbon dioxide is purged with the associated gas. 

Hazardous Decomp. Prods. Heated to decomp., emits very toxic fumes of POx and SOx Uses Biocide for water treatment, sec. oil field recovery flame retardant for cellulosic fabrics and blends... 

Alkyl dimethyl ethylbenzyl ammonium chloride Myristalkonium chloride biocide, sec. oil field recovery Tetrakis (hydroxymethyl) phosphonium sulfate biocide, ship bottom paints Triphenyltin fluoride biocide, slurries 7-Ethyl bicyclooxazolidine biocide, soaps 3,4,4 -Trichlorocarbanilide biocide, specialties... 

If a viscoelastic material is forced to flow from a large reservoir through a circular tube, the diameter of the extrudate is found to be larger than the tube diameter. Many researchers [61-65] have argued that that causes the die swell. They developed the following three points of view for the cause of the die swell polymer chain orientation within the capillary caused by the high shear field recovery of the elastic deformation and viscose heat effects. The most important concept is the recovery of the elastic deformation imposed in the capillary. 

---