Extractive Atmospheric Monitoring

There are two ways to monitor the concentrations of trace gases in the atmosphere by FT-IR spectrometry. The first is to draw the atmosphere in the region of interest into a long-path gas cell, and the second is to measure the spectrum of the atmosphere in situ. The first approach, which is known as extractive monitoring [1], is covered in this section, and the second, known as open-path FT-IR spectrometry (OP/FT-IR) [2], is covered in Section 22.2. 

Fourier Transform Infrared Spectrometry, Second Edition, by Peter R. Griffiths and James A. de Haseth Copyright 2007 John Wiley Sons, Inc. 

Most extractive measurements are made with the use of multipass gas cells with a pathlength of 20 or 40 m. The construction of these cells was described in Section 11.2. Some of these cells are reasonably small and may be mounted in the sample compartment of the spectrometer. Typical detection limits are on the order of 100 parts per billion by volume (ppbv). 

Data may be output in a number of ways [1]. The measured concentrations of one or more species may simply be plotted as a function of the time of day. The 

95% confidence interval may be added to these plots. Alternatively, for a given time of day, the concentration of all species of interest may be shown as a fraction of the maximum allowed concentration on a bar chart. 

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Cooking oils, fhiit squashes, water, wine, spirits Solution extracts of absorption tubes (atmospheric monitoring)... 

R. L. Spellicy and J. D. Webb, Atmospheric monitoring using extractive techniques, in Handbook of Vibrational Spectroscopy, J. M. Chalmers and R R. Griffiths, Eds., Wiley, Chichester, West Sussex, England, 2002, Vol. 2, p. 1721. 

C. Aguilar, I. Feirer, R Bonnll, R. M. Marce and D. Barcelo, Monitoring of pesticides in river water based on samples previously stored in polymeric cartridges followed by on-line solid-phase extraction-liquid cliromatography-diode array detection and confirmation by atmospheric pressure chemical ionization mass spectrometry . Anal. Chim. Acta 386 237-248 (1999). 

In the AOAC procedure, the beer was treated with dilute HCl and sulfamic acid, and the added acid was then neutralized by addition of dilute alkali. Volatile nitrosamines were collected by atmospheric pressure distillation. The distillate was made alkaline and extracted with DCM. The extract was dried and concentrated to 1.0 ml and an aliquot was analyzed by GC-TEA. We used these concentrates, without further cleanup, for evaluating the GCMS high resolution selected ion monitoring procedure. 

Polymeric precolumns of styrene-divinylbenzene were used by Aguilar et al. to monitor pesticides in river water. Water samples (50 mL) were trace enriched on-line followed by analysis using LC combined with diode-array detection. LC atmospheric pressure chemical ionization (APCI) MS was used for confirmatory purposes. It was found that after the pesticides had been extracted from the water sample, they could be stored on the precartridges for up to 3 months without any detectable degradation. This work illustrates an advantage of SPE for water samples. Many pesticides which may not be stable when stored in water, even at low temperature, may be extracted and/or enriched on SPE media and stored under freezer conditions with no detectable degradation. This provides an excellent way to store samples for later analysis. 

A mixture of 1 (100 mg, 0.2 mmol) and ammonium trifluoromethanesulfonate (377 mg, 2.2 mmol) in THE (10 mL) was reacted with NaBH(OEh)3 (2 equiv) at room temperature under an argon atmosphere. The reaction was monitored by TLC analysis. After the reaction was complete, the solvent was removed by a rotary evaporator, the mixture extracted with ethyl acetate, dried over anhydrous Na2S04, and concentrated. 

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