Page 201 - Materials Chemistry, Second Edition

182 Life Cycle Assessment of Wastewater Treatment

the extraction of some compounds. Okuda et al. (2009) compared UAE and PLE for
the extraction of 66 pharmaceuticals from sludge. Fifteen percent of the pharmaceu-
ticals were better extracted by PLE using water conditioned at pH 2 as extraction
solvent, whereas 33% of the pharmaceuticals were better extracted using methanol
conditioned at pH 4. The others were better extracted by UAE. Barron et al. (2008)
reported a multiresidue determination of 27 frequently prescribed and consumed
pharmaceuticals in digested sludge. The optimized method involved two PLE cycles
with MeOH:water (1:1, v/v), 60 °C, and 1500 p.s.i. The total extraction solvent vol-
ume was 53 mL for 1 g of sludge. Afterward, clean-up by SPE with Oasis HLB
cartridges and LC-MS/MS determination was applied. Recoveries were higher than
60% for 75% of the pharmaceutical compounds. Seira et al. (2013) applied PLE to the
determination of two widely administered anticancer drugs (ifosfamide and cyclo-
phosphamide). They found that extraction solvent was the most decisive extraction
factor and that interactions between some parameters also appeared very influential.
Matrix effect was described as the most limiting analytical step for quantification, to
different extents depending on the analyte and the type of sludge.

9.2.1.3 Microwave-Assisted Extraction (MAE)
In MAE, microwave energy is used to heat solvents in contact with solid or liquid
samples and to promote partition of the analytes from the sample matrix into the
extraction solvent. The main variables to optimize are type and volume of extraction
solvent, temperature, extraction time, and microwave power (Sánchez-Prado et al.,
2015; Dobor et al., 2010). Dorival-García (2015) applied MAE to the determination of
17 strongly sorbed quinolones in compost samples, achieving recoveries in the range
from 72% to 96% and inter-day precision lower than 4% for most of the compounds.
Speltini et al. (2015) applied a new low-pressurized microwave platform, improv-
ing the extraction recoveries of fluoroquinolone residues from compost in compari-
son with conventional MAE. Evans et al. (2015) reported an analytical method for
multiresidue determination of chiral pharmaceutically active compounds, including
β-blockers, antidepressants, and amphetamines, in wastewater and digested sludge.
The method allowed the determination of the enantiomers of 11 pharmaceuticals in
digested sludge. The method was validated for 1 and 3 g of sludge. Extraction was
carried out with 20 mL of MeOH:water (1:1, v/v) heated to 120 °C for 30 min, and
extract clean-up was carried out with OASIS MAX cartridges (Waters, UK). OASIS
HLB cartridges were rejected, because interfering compounds were not successfully
removed, resulting in an increase in the backpressure of the chiral LC column. Most
of the recoveries were in the range from 65% to 140%. Intra- and inter-day precision,
expressed as relative standard deviation (RSD%), were in the range 4.3%–44.1%
and 5.1%–51.7%, respectively. Petrie et al. (2016) reported a multiresidue analytical
method for the determination of pharmaceutical compounds (estrogens, antibiotics,
anti-hypertensives, anti-inflammatories, lipid regulators, anti-histamines, anti-dia-
betics, β-blockers, H2 receptor agonists, X-ray contrast media, cytostatics, anesthet-
ics, anti-depressants, anti-epileptics, analgesics, stimulants, and others) and some
of their metabolites together with other emerging contaminants in wastewater, river
water, and digested sludge. Digested sludge (0.5 g) was extracted with 25 mL of
MeOH:water (pH: 2) (1:1,v/v) by MAE at 110 °C for 30 min, then clean-up by SPE