The recoveries of 16 isomers of chlorophenols (CPs)
from the adsorbent (XAD-2) of the MM5 train are
affected by hydrochloric acid (HCl) present in the
incinerator flue gas. At 2.05 and 5.53 mg/L in flue
gas, HCl caused desorption of CPs from XAD-2. The
desorption is dependent upon the number of chloro
substituents in the CPs. The Soxhlet extraction
behaviors
of CPs from XAD-2 in the presence or the absence
of HCl were also studied in the laboratory. The
results explain the previously reported low recovery
of pentachlorophenol from XAD-2 when the flue gas
contained none or very low concentrations of HCl. An
extraction procedure for complete CPs recoveries
from XAD-2 is proposed that involved two sequential
extractions: first with dichloromethane and then
with the addition of 1.0 mL of 1.0 M aqueous HCl on
XAD-2 and followed by the subsquent extraction
with dichloromethane. This procedure does not affect
other semivolatile compounds on XAD-2 and leads
to [13C6]pentachlorophenol surrogate
recovery of 90 ±
6%. An extraction anomaly of CPs using dichloromethane from the combined synthetic acidic condensate and acidic ethylene glycol is presented.
Toluene is suggested as the solvent for complete CPs
extraction from the combined liquids. This acid
effect led to a suggestion of using at least one surrogate
isomer for each CP group on XAD-2 of the MM5
train.
The effect of hydrochloric acid (HCl) at 0.17, 2.05, and 5.53 mg/L in incineration flue gas on the recoveries of 16 polycyclic aromatic hydrocarbons (PAHs) from XAD-2 adsorbent of the MM5 (Modified Method 5) train was investigated. At constant concentrations of moisture (14%), carbon dioxide (7%), and oxygen (10%), 2.05 and 5.53 mg/L HCl decreased the recoveries of benzo[a]pyrene, perylene, anthracene, and acenaphthylene. At 5.53 mg/L HCl, only 6, 8, 32, and 46% of these PAHs, respectively, were recovered from XAD-2. The recoveries of other PAHs were 88-112% with relative standard deviations of 3-13% at all acid concentrations in flue gas. Acid effect occurred primarily during sampling of flue gas, and a smaller acid effect occurred during sample processing, in which the XAD-2 containing HCl, PAHs, and moisture was Soxhlet extracted using dichloromethane. The hypothesis is that these PAHs formed cation radicals in the presence of HCl, which was followed by subsequent reaction with water to yield quinones. The extraction of PAHs from synthetic acidic condensate and acidic ethylene glycol of the MM5 train was not dependent on pH. Extractions from various acidities of these combined solutions gave recoveries of 76-102% with relative standard deviations of 4-13%. The implications of all the above-mentioned effects on the selection of surrogates and interpretation of analytical results for MM5 sampling and analysis are discussed.
The effect of hydrochloric acid (HCl) at 0.17, 2.05, and 5.53 mg/L in incineration flue gas on the recoveries of nine congeners and isomers of dichloro-to hexachlorobenzenes (CBs) and nine congeners of dichloro-to decachlorobiphenyls (PCBs) from XAD-2 adsorbent of the MM5 (Modified Method 5) train was investigated. At constant concentrations of moisture (14%), carbon dioxide (7%), and oxygen (10%), 2.05 and 5.53 mg/L HCl in flue gas decreased the recoveries of dichloro-, trichloro-, and tetrachlorobenzenes. At 5.53 mg/L HCl, the decrease in recoveries of these compounds was 23-40%. The lower the number of the chloro substituents of the CBs, the greater the acid effect was. Pentachloro-and hexachlorobenzenes were not affected, and the mean recoveries were 93 ( 4 and 92 ( 8%, respectively. This acid effect on dichloro-to tetrachlorobenzenes occurred during sample processing in which the CBs/PCBs on XAD-2 containing acid and moisture were Soxhlet extracted using dichloromethane. PCBs were not affected, and the mean recovery was 100 ( 6%. The best recoveries for the liquid-liquid extraction of CBs/PCBs using toluene from the combined synthetic acidic condensate and ethylene glycol of the MM5 train were obtained at acidic and nearly neutral pH. A base effect was observed at pH > 7. The implications of an acid effect on the selection of surrogates and interpretation of analytical results for MM5 sampling and analysis were discussed.
The recoveries of chlorobenzenes (CBs), polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs) from the acid-base-on-silica column (ABS), the silver nitrate-on-silica column (SNS), and the alumina column (ALM) were investigated using eluents with various concentrations of dichloromethane in hexane. PCBs recoveries from the ABS and ALM columns are generally increased with increasing number of chloro substituents. However, PCBs recoveries are also complicated by the inductive and resonance contributions due to the different conformation and electron density of the congeners. The recoveries of PCBs with lower number of chloro substituents decreased with increasing silver nitrate content coated on silica. With 2% dichloromethane in hexane (as normally used in MM5 analysis), the recoveries of all CBs and trichloro- to decachlorobiphenyls from ABS, 10% SNS, and ALM columns in series are ≥80%. However, the 2,4-dichlorobiphenyl is only 16% recovered, and monochlorobiphenyls are not recovered at all. Under these conditions, the recoveries of PCDDs/PCDFs from ABS and 10% SNS columns in series are ≥80%. With 60% dichloromethane in hexane, PCDDs/PCDFs recoveries from ALM column are ≥80%. The implication of the selective adsorption of PCBs on the fractionation of CBs/PCBs and PCDDs/PCDFs from these MM5 cleanup columns is discussed.
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