Page 199 - Materials Chemistry, Second Edition

180 Life Cycle Assessment of Wastewater Treatment

affordable for routinely monitoring pharmaceuticals in sewage sludge. In the mul-
tiresidue determination of pharmaceutical compounds with different physicochemi-
cal properties, compromise solutions have to be applied, such as, for instance, not
adjusting extraction solvent pH, which can result in good extraction recoveries for
some compounds but poor recoveries for the most acidic pharmaceuticals. The most
widely used extraction techniques for the determination of pharmaceuticals in sew-
age sludge are ultrasonic-assisted extraction (UAE), pressurized liquid extraction
(PLE), and microwave-assisted extraction (MAE) (Table 9.1). Some authors have
compared the efficiencies of several techniques for the extraction of pharmaceuticals
from sewage sludge (Dorival-García et al., 2013; Okuda et al., 2009). Dorival-García
et al. (2013) compared quinolone extraction from sewage sludge by UAE, MAE, and
PLE. They concluded that MAE and PLE were better options for quinolone extrac-
tion than UAE, because they enabled higher extraction efficiencies, easy operation,
a shorter analysis time, and a higher degree of automation than UAE. Okuda et
al. (2009) compared UAE and PLE for the extraction of 66 pharmaceutical com-
pounds and personal care products from sewage sludge, concluding that some com-
pounds were better extracted by UAE, whereas others were better extracted by PLE.
Recently, some easy and inexpensive methods have been reported for pharmaceuti-
cal determination in sewage sludge. These methods are the so-called quick, easy,
cheap, effective, rugged, and safe extraction (QuEChERS) (Peysson and Vulliet,
2013; Bourdat-Deschamps et al., 2014) and matrix solid-phase extraction (MSPD)
(Triñanes et al., 2016; Li et al., 2016). Regardless of the extraction technique applied,
samples are first dried (to express the concentration per dry weight), homogenized,
and sieved. To avoid the degradation or loss of pharmaceuticals at high temperatures,
drying by lyophilization is preferred.
9.2.1.1 Ultrasound-Assisted Extraction (UAE)
In UAE, solid-liquid extraction is carried out in an ultrasound bath. UAE is an effi-
cient and low solvent-consuming alternative to classical extraction techniques such
as Soxhlet, is inexpensive in comparison with PLE and MAE equipment (Albero et
al., 2015), and does not require the high temperatures applied in PLE, which could
degrade some compounds (Martín et al., 2010; Herrero et al., 2013). This extraction
technique is widely used for the extraction of organic pollutants from sewage sludge
(Zuloaga et al., 2012). The main variables to optimize are the type and volume of
extraction solvent and extraction cycles. Acetone, methanol (MeOH), and acetoni-
trile are the most commonly used extraction solvents for the determination of phar-
maceutical compounds. In general, two or three extraction cycles with fresh solvent
are applied with a total extraction time lower than 45 min (Albero et al., 2015). After
extraction, clean-up by SPE is usually applied to remove interfering compounds.
Some multiresidue methods have been reported using UAE. Gago-Ferrero et al.
(2015) developed a multiresidue method for the extraction of 148 pharmaceuticals
and illicit drugs from sewage sludge and determination by liquid chromatography-
tandem mass spectrometry (LC-MS/MS). UAE was carried out with MeOH and
acidified water containing ethylene diamine tetraacetic acid (EDTA). No clean-up
was applied. Absolute recoveries were in the range of 50%–110% for more than 77%
−1
of studied compounds. Limits of detection (LODs) were below 0.01 ng kg d.m.