Detection frequency

I CRS interferogram with a frequency of A = coj + 2c0j - cOq, where cOp is the detected frequency, coj is the narrowband frequency and coj the Raman (vibrational) frequency. Since cOq and coj are known, Wj may be extracted from the experimentally measured RDOs. Furthemiore, the dephasing rate constant, yj, is detemiined from the observed decay rate constant, y, of the I CRS interferogram. Typically for the I CRS signal coq A 0. That is, the RDOs represent strongly down-converted (even to zero... 

An important extension to the simplest upconversion experiment at a single detection frequency M2 is the practice of measuring time-resolvedfluorescence spectra, that is, the shape of the fluorescence spectrum... 

Vibronic relaxation of XeF in solid Ar at 25 K was studied by pumping vibronic transitions with a subpicosecond UV pulse, and detecting frequency-resolved emission with a fast optical gate [25]. XeF has two sites in Ar, one... 

If the detected frequency of the flashing light scattered by a microscopic object when crossing the fringes is multiplied by the fringe distance, the veltKity component of the scattering object normal to the beam bisector and parallel to the laser beam plane is determined. 

As it can be observed in Fig. 2, three out of the 16 investigated compounds, namely, heroin, lysergic acid diethylamide (LSD), and its metabolite 2-oxo, 3-hydroxy-LSD (O-H-LSD), were not detected in any wastewater sample. Two other target analytes, 6-acetyl morphine (6ACM) and A9-tetrahydrocannabinol (THC), were only present in influent wastewaters and with low detection frequencies. The most ubiquitous compounds, present in all influent and effluent wastewater samples analyzed, were the cocaine metabolite benzoylecgonine, and the amphetamine-like compounds ephedrine (EPH) and 3,4-methylenedioxymethamphetamine (MDMA or ecstasy). Cocaine, cocaethylene (CE, transesterification product of cocaine formed after the joint consumption of cocaine and ethanol), and morphine (MOR) were detected in all influent, but not in all effluent wastewaters (see Fig. 2). 

However, signal also depends on detector data acquisition rate noise increases with increased detection acquisition rate. Since GCxGC peaks are narrow, necessitating higher detection frequencies, S/N ratio improvements are not as great as might be initially anticipated. 

One of the disadvantages concerns the fact that in axial magnets it is rather difficult to use probes with solenoid RF coils. The difficulties are related to sample insertion/removal complications and to numerous spatial constraints, exacerbated by the presence of a glass dewar for sample-temperature control (see Section VI). This is unfortunate because the alternative saddle coils are substantially less efficient, especially at the relatively low excitation/detection frequencies used in FFC NMR. 

In addition, seasonal variations may also influence the levels of APIs found. A seasonal influence on the FQs and TCs detection frequency in Coimbra (Portugal) municipal and hospital wastewaters was reported [34, 55]. Seasonal variations of up to a factor of four were also reported in a Finnish river [99, 100]. Seasonal variations can also affect the efficiency of WWTPs and river discharges since in winter the microbial activity is reduced due to low temperatures and the dilution effect is higher. Ultimately, at a wider level, geographical situation and climate may also explain different contamination scenarios between countries in different climatic zones [99, 100]. 

Compounds Country Detection frequency Population Exposure estimate (ng/day) Particularities References... 

Levels and detection frequency of TBBPA are generally lower than those of PBDEs and HBCDs in human samples. Consistent with its phenolic structure that can be rapidly conjugated in human hver and subsequently excreted in bile [36], TBBPA has a short human half-life that has been reported to be as low as 2 days in human plasma [28, 37]. In addition, HBCD and PBDEs are additive BERs, while TBBPA is a reactive BFR, meaning that TBBPA is chemically bound to the polymer structure and, thus, the leaching or release of TBBPA into the environment is limited [38]. Therefore, levels of TBBPA are often lower and detection of this... 

TBBPA concentrations in human plasma in the low ng/g lipids range have been reported (Table 2). Concentrations and detection frequency of TBBPA in adipose tissue are even lower due to the relatively low lipophilic properties of TBBPA ( ow = 5), and the metabolic fate of this BFR. 

Food So far only a handful of studies have investigated the presence of OPFRs in food samples. In a market basket study performed by the US FDA [87], most of the OPFRs (EHDPP, TCEP, TC/PP, TnBP, TPP, TCP) were found only at the ng/g level. More than 91% of the results were below the quantification limit in most t3q>es of samples. Higher detection frequencies were observed for TPP in margarine and caramels (mean 45 ng/g). 

In urine, OPFR metabolites have been detected, but the median concentrations of the diaryl and dialkyl phosphates remained mostly below the quantification limit. Ranges of concentrations of dialkyl and diaryl phosphates are shown in Table 4. In the study of Schindler et al. [302, 303], the detection frequency was highest for BCEP (50%), followed by DPP (30%), BCPP (12%), and DBP (3%). Di-w-cresyl and di-/7-cresyl phosphate were not found in any sample, probably due to lower exposure in the indoor environment. Reemtsma et al. [304] found also monoaryl and alkyl phosphates in human urine, of which the monobutyl phosphate was the... 

Compound Matrix Country Population Concentrations/exposure Detection frequency Particularities References... 

Similar biomonitoring studies in Belgium and China conducted with adolescents (14—16 years) and children and students (3-24 years), respectively, showed a high detection frequency of more than 90% [154, 156]. However, mean and median values were lower compared to the US data. In the Chinese study, females had a statistically higher least square geometric mean concentration than males. They also observed a decreasing tendency with age in the 7-24 age group [156]. 

Serum and plasma Serum and plasma samples partially mimic the trend observed in human milk samples. Overall, polycyclic musks can be detected more frequently and at higher concentrations compared to the nitro musk compounds (Table 8). HHCB is by far the most common of the polycyclic musks as production and use of this compound increased at the same time as production and use of nitro musks decreased [168]. However, MX still seems to be a common contaminant in human serum, with a considerably high detection frequency compared to AHTN. A high percentage of the population is still exposed to nitro musk compounds [168], although a moderate decline in MX and a strong decline in MK are observed. 

In a study of Casas et al. [155], 120 pregnant women and 30 of 4-year-old boys were involved. The median urine concentration of the 4-year-old boys (4.2 ng/mL) was approximately double of the median concentration of the pregnant women (2.2 ng/mL). Other different studies conducted in the USA have focused on children exposure [152, 217, 218]. In all three studies, detection frequency was more than 94% which demonstrates the ubiquitous exposure of the complete population. 

In the study done by Wang et al. [277] on PCPs from Canada, the compound with the highest detection frequency was D5, with a top concentration of... 

Alternate Protocol 1 Detection Frequency With Gas Chromatography/... 

The detection frequency method uses a number of sniffers to quantify an odor in the GC effluent from a single concentration. The underlying assumption is that any random sample of sniffers will functionally express a range of sensitivities, so that some sniffers will detect an odor and others will not. The conclusion is that the fraction of a group that detects an odor is related to the group potency of the odor, a notion that can be supported by the large diversity in odor thresholds observed in humans. 

Verification requires sniffing an authentic standard to verify that the component and the standard have the same retention index and odor quality. Figure Gl.8.3 shows a typical detection-frequency chromatogram. 

Figure G1.8.3 Sniffing chromatogram of eight volatile compounds in a reference mix obtained by the detection frequency method using eight assessors (see Alternate Protocol 1). Compounds 1, 100 ng 2-butanone 2, 20 ng diacetyl 3, 500 ng ethyl acetate 4, 100 ng 3-methyl-1-butanol 5, 20 ng ethyl butyrate 6,100 ng hexanal 7, 100 ng 2-heptanone 8, 500 ng a-pinene.

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