Detectable compounds, trends

During 1991, water-quality samples were analyzed from a network of 303 wells across 12 states, while a subset of the 303 wells was sampled from 1992 to 1994 (Kolpin and Burkart, 1991 Kolpin et al., 1993, 1994,1995, 1996, 1997, 1998, 2000) (Figure 30.3A). Atrazine was detected in samples from 22.4% of the 303 wells (Table 30.1). Two atrazine degradation products, DEA and DIA, also were some of the most frequently detected compounds in these studies. The trend, as shown by the frequencies of detection, reflects the relative stability of these compounds. 

Irth, H. and Brinkman, U. A. Th. 1990. Ligand exchange for trace enrichment and selective detection of ionic compounds. Trends Anal. Chem., 9 235-241. 

G. Surpateanu, S. Fourmentin, D. Landy, G. G. Surpateanu and P. Decock, Cyclodextrin Derivatives Used in the Detection and the Remediation of Volatile Organic Compounds , Trends Heterocycl. Chem., 2006, 11, 63. 

Figure 4.41. Trend analysis over 12 batches of a bulk chemical. The sieve analysis shows that over time crystals larger than 250 /urn were reduced from a weight contribution in the range of a few percent of the total to about 1% in favor of smaller sizes. Impurity C appears to follow the trend given by the lead compound for the competing side reaction 1. The very low moisture found for sample 3 could be due to a laboratory error because during drying one would expect ethanol to be driven off before water. Methanol is always below the detection limit.

Evaluation of trends in /pp coupling constants in solid-state 31P NMR spectra of P-phospholyl-NHPs allowed one to establish an inverse relation between the magnitude ofM and P-P bond distances [45], The distance dependence of. /pp is in line with the dominance of the Fermi contact contribution, and is presumably also of importance for other diphosphine derivatives. At the same time, large deviations between lJvv in solid-state and solution spectra of individual compounds and a temperature dependence of lJ77 in solution were also detected (Fig. 1) both effects... 

In STP effluents, total extractable estrogens and conjugates have been detected at levels up to 1 /jg/L [9,11,26]. Despite the wide variability in terms of removal efficiency reported for different WWTPs, a general trend has been observed with respect to the identity of the compounds most frequently detected in WWTP effluents. Thus, of the various compounds most commonly monitored - namely, estradiol, its metabolites estriol and estrone, and the synthetic estrogen ethynylestradiol - estrone is the most ubiquitous both in WWTP effluents and in environmental waters in general, while the most potent estrogens estradiol and ethynylestradiol have only occasionally been detected [26,40-42]. As for the conjugates, the very few studies that have attempted their determination pointed out estrone sulfates as the most abundant, while glu-curonides are most often found below the limit of detection [26,36,38,39]. 

In a well-equipped laboratory it is mandatory that these three techniques be coupled with a mass spectrometric detector in order to achieve a combination of resolution of mixtures, positive identification of separated organics and the high sensitivity that is essential when dealing with environmental samples. The penetration of mass spectrometers in recent years is indicated by the fact that of the 50 types of organic compound that have been determined by gas chromatography in 21 cases mass spectrometric detection is discussed. This trend will, no doubt, continue. 

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 examining Results sections move by move, we looked at how authors refer to hgures and tables, how they use compound labeling, and how they highlight trends in the data. We examined how to report values below detection limits and how to use R to consolidate reactions in a synthesis paper. In this part of the chapter, we analyze a few writing conventions that are characteristic of the entire Results section, including verb tense, voice, and word choice. 

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