33, 56, 80, 81, 84, 86, 105, 107] with mixed fill (ion exchange-reverse phase), and
those of high-purity silica RPC-18 [46, 49, 51, 52, 70, 71, 74, 80, 89, 107] are
effective for extracting non-polar or moderately polar compounds. Strata X [19, 43,
57, 64, 69, 73, 76, 77] consists of a polymeric sorbent and is used over a wide range
pH values. The ENVI 18, designed for water samples, is less used [70, 75, 83]. Diskshaped cartridges tolerate higher sample flows [53, 67, 121]. Both the cartridges and
the disks can be coupled with detection equipment to perform the process automatically [51–54, 67, 123]. Molecularly printed polymer (MIP) cartridges have been
used in recent years [65, 68].
The cartridges must be preconditioned according to the manufacturer’s instructions. It is usual to wash them first with methanol [5, 7, 8, 17, 19, 24, 52, 56, 57, 62,
64, 66, 70–73, 75, 76, 82–84, 105, 106, 108, 112] followed by deionized water [5, 7,
8, 16, 17, 49, 62, 66, 70–73, 85, 110], which can be acidified to the pH of the sample
[5, 7, 16, 19, 24, 28, 33, 43, 52, 56, 57, 64, 73, 75, 76, 83, 84, 86, 105, 108]. Ethyl
acetate [16, 33], n-hexane [28, 49, 78], dichloromethane [49, 110], acetonitrile [86],
tert-butyl methyl ether [110], and acetone [28, 43] are also used. Sometimes, before
washing with methanol, cartridges are washed with ethyl acetate [8, 62, 72, 106],
n-hexane [52, 84, 106], or acetone [52, 75, 84].
After conditioning, the extraction cartridge is loaded with the aqueous solution of
the sample, and the next step depends on the selected analytical method. Some
authors wash with deionized water [5, 19, 43, 50, 57, 62, 66, 71, 74, 75, 110], while
others wash with a methanol-water mixture [8, 16, 17, 24, 53, 70, 76, 83, 86]. The
cartridges are then dried under vacuum [5, 16, 24, 33, 52, 53, 57, 64, 70, 71, 74, 75,
83, 107] or with N 2 gas [7, 28, 43, 46, 50, 51, 56, 62, 66, 84, 105, 110]. The process
can be manual or automated [46, 62, 108, 113].
Extraction of the analyte retained in the cartridge is carried out with an organic
solvent. The most commonly used solvents are ethyl acetate [8, 62, 66, 74, 77, 79,
80, 107], acetone [28, 51, 56, 67, 83, 114], methanol [7, 17, 19, 24, 48–50, 52, 57,
64–67, 69, 71–73, 75, 80, 88, 91, 107, 110, 112, 114], and mixtures thereof [16, 33,
70, 77, 86, 88, 107, 110]. N-hexane [66] and dichloromethane [67] are used but to a
lesser extent. The extracted analyte is evaporated to dryness and reconstituted for the
final analysis step. Evaporation to dryness is almost always carried out under an
atmosphere of N 2 [7, 8, 16, 17, 28, 33, 49, 59, 63, 67, 68, 71, 78–81, 83, 93, 94, 99,
102, 107] although some authors do so under a vacuum [19, 24, 52, 70]. The final
reconstitution allows the sample to be concentrated several hundred times,
depending on the subsequent analysis.
The need to increase the extraction efficiencies, use smaller volumes of samples
and organic solvents, reduce extraction times, and simplify times and costs of the
stages prompted the development of microextraction techniques. These techniques
use very little or no organic solvent, isolate and concentrate analytes, have greater
specificity and selectivity, are highly enriched, rapid, and allow automation [42, 45,
50, 55, 58, 59, 82, 89, 94–98, 103, 104, 118, 121, 122]. The microextraction of
NSAIDs from water samples has been carried out both in solid and liquid phases
(SPME and LPME, respectively).
92
K. Isaac-Olivé et al.
those of high-purity silica RPC-18 [46, 49, 51, 52, 70, 71, 74, 80, 89, 107] are
effective for extracting non-polar or moderately polar compounds. Strata X [19, 43,
57, 64, 69, 73, 76, 77] consists of a polymeric sorbent and is used over a wide range
pH values. The ENVI 18, designed for water samples, is less used [70, 75, 83]. Diskshaped cartridges tolerate higher sample flows [53, 67, 121]. Both the cartridges and
the disks can be coupled with detection equipment to perform the process automatically [51–54, 67, 123]. Molecularly printed polymer (MIP) cartridges have been
used in recent years [65, 68].
The cartridges must be preconditioned according to the manufacturer’s instructions. It is usual to wash them first with methanol [5, 7, 8, 17, 19, 24, 52, 56, 57, 62,
64, 66, 70–73, 75, 76, 82–84, 105, 106, 108, 112] followed by deionized water [5, 7,
8, 16, 17, 49, 62, 66, 70–73, 85, 110], which can be acidified to the pH of the sample
[5, 7, 16, 19, 24, 28, 33, 43, 52, 56, 57, 64, 73, 75, 76, 83, 84, 86, 105, 108]. Ethyl
acetate [16, 33], n-hexane [28, 49, 78], dichloromethane [49, 110], acetonitrile [86],
tert-butyl methyl ether [110], and acetone [28, 43] are also used. Sometimes, before
washing with methanol, cartridges are washed with ethyl acetate [8, 62, 72, 106],
n-hexane [52, 84, 106], or acetone [52, 75, 84].
After conditioning, the extraction cartridge is loaded with the aqueous solution of
the sample, and the next step depends on the selected analytical method. Some
authors wash with deionized water [5, 19, 43, 50, 57, 62, 66, 71, 74, 75, 110], while
others wash with a methanol-water mixture [8, 16, 17, 24, 53, 70, 76, 83, 86]. The
cartridges are then dried under vacuum [5, 16, 24, 33, 52, 53, 57, 64, 70, 71, 74, 75,
83, 107] or with N 2 gas [7, 28, 43, 46, 50, 51, 56, 62, 66, 84, 105, 110]. The process
can be manual or automated [46, 62, 108, 113].
Extraction of the analyte retained in the cartridge is carried out with an organic
solvent. The most commonly used solvents are ethyl acetate [8, 62, 66, 74, 77, 79,
80, 107], acetone [28, 51, 56, 67, 83, 114], methanol [7, 17, 19, 24, 48–50, 52, 57,
64–67, 69, 71–73, 75, 80, 88, 91, 107, 110, 112, 114], and mixtures thereof [16, 33,
70, 77, 86, 88, 107, 110]. N-hexane [66] and dichloromethane [67] are used but to a
lesser extent. The extracted analyte is evaporated to dryness and reconstituted for the
final analysis step. Evaporation to dryness is almost always carried out under an
atmosphere of N 2 [7, 8, 16, 17, 28, 33, 49, 59, 63, 67, 68, 71, 78–81, 83, 93, 94, 99,
102, 107] although some authors do so under a vacuum [19, 24, 52, 70]. The final
reconstitution allows the sample to be concentrated several hundred times,
depending on the subsequent analysis.
The need to increase the extraction efficiencies, use smaller volumes of samples
and organic solvents, reduce extraction times, and simplify times and costs of the
stages prompted the development of microextraction techniques. These techniques
use very little or no organic solvent, isolate and concentrate analytes, have greater
specificity and selectivity, are highly enriched, rapid, and allow automation [42, 45,
50, 55, 58, 59, 82, 89, 94–98, 103, 104, 118, 121, 122]. The microextraction of
NSAIDs from water samples has been carried out both in solid and liquid phases
(SPME and LPME, respectively).
92
K. Isaac-Olivé et al.