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AnalytesMatrixAnalytical methodAnalysis conditions156 target analytes screened120 satisfactorily determined71 and 73 compounds quantifiedWastewater and receiving waters in South AfricaUHPLC-Orbitrap MSESIOrbitrap analyserAnalytical column: XBridge™ C18, 100 mm × 2.1 mm, 3.5 μmMobile phase: [A] 0.1% formic acid in water and [B] 0.1% formic acid in acetonitrileElution programme: 0–2% B, progressed to 98% B in 15 minutes, then a hold in 2 minutes, and returned to the initial conditions[100]17-α-ethynylestradiol [EE2], 17-β-estradiol [E2], estrone [E1], testosterone, progesterone, diclofenac, primidoneTropical estuarine sedimentsLC-MS/MSESI[+]/[−] modesTriple quadrupole analyserAnalytical column: Kinetex XB C18, 30 mm × 2.1 mm, 1.7 μmMobile phase:for negative ionization mode [A] 0.2% NH₄OH in 95% water [95 : 5, H₂O:OS] [OS consists of 60% methanol and 40% acetonitrile] and [B] 0.2% NH₄OH in 95% OS [95 : 5, OS: H₂O]. for positive ionization mode [A] 95% water [95 : 5, H₂O:OS] [OS] and [B] 95% OS [95 : 5, OS: H₂O].Elution programme: for negative ionization mode 0 – 3 minutes 5% B progressed to 95% in 4 minutes and then holding it constant for 2 minutes and returned to the initial conditionsfor positive ionization mode 0–3 minutes 5% B progressed to 95% in 3 minutes and then holding it constant for 2 minutes and returned to the initial conditions[89]Ceftazidime, meropenem, amoxicillinCiprofloxacin, lincomycin, clindamycin, erythromycin, azithromycin, clarithromycin, tylosin, sulfamethazine, sulfamethoxazole, trimethoprim, tetracycline, minocyclinechlortetracycline, oxytetracyclinetriclosan, triclocarban, vancomycinchloramphenicolEnvironmental water samples [surface water, treated wastewater effluents]UHPLC -MS/MSESI [+]/[−] modesTriple quadrupole analyserAnalytical column: Poroshell 120EC-C18, 100 mm × 3.0 mm, 2.7 μmMobile phase: [A] 0.1% formic acid in water and [B] 0.1% formic acid in a 50 : 50 [v/v] mixture of methanol and acetonitrileElution programme: 0–1.5 minutes 10% B progressed to 90% B at 15 minutes, held until 22 minutes, and returned to the initial conditions[87]40 multiclass antibiotics from cephalosporin, fluoroquinolone, lincosamide, macrolide,nitroimidazole, quinolone, sulfonamide and tetracycline groupsEnvironmental matricesLC-MS/MSIon source: ESITriple quadrupole/linear ion trap analyserAnalytical column: Kinetex C18, 100 mm × 2.1 mm, 2.6 μmMobile phase: [A] 0.001% formic acid in water and [B] methanolElution programme: 0–0.01 minutes 5% B progressed to 10% B at 3.0 minutes, then to 28% B at 6.0 minutes, 70% B at 11.0 minutes, 85% B at 13 minutes, and finally returned to the initial conditions[88]acetaminophen, acetazolamide, acetylsalicylic acid, amiodarone, amoxicillin, ampicillin, atenolol, azithromycin, caffeine, carbamazepine, ciprofloxacin, diclofenac, clarithromycin, cyclophosphamide, erythromycin A, flumequine, gemfibrozil, hydrochlorothiazide, ibuprofen, josamycin, ketoprofen, lorazepam, losartan, metoprolol, metronidazole, niflumic acid, nordiazepam, 19-norethindrone, norfloxacin, ofloxacin, oxazepam, oxolinic acid, phenazone, piperacillin, roxithromycin, spiramycin, sulfadiazine, sulfamethazine, tylosine sulfamethoxazole, tetracycline, trimethoprimThree fish species hake [Merluccius merluccius], red mullet [Mullus surmuletus], sole [Solea solea] and one crustacean species shrimp [Palaemon serratus]UPLC-MS/MSIon source: ESI[+]/[−]Triple quadrupole analyserAnalytical column: C18 Acquity UPLC HSS T3, 50 mm × 2.1 mm, 1.8 μmMobile phase:for positive ionization mode [A] 0.1% formic acid in water and [B] acetonitrilefor negative ionization mode [A] 0.01% formic acid and eluent [B] acetonitrileElution programme: 0–2 minutes 2% [B] progressed to 60% at 4 minutes, then to 100% at 6 minutes, held 1 minute and returned to the initial conditions[92]56 antimicrobial drugs (tetracyclines, sulfonamides,β-lactams, macrolides and quinolones)Wastewater and sea waterUPLC-MS/MSIon source: ESI[+]Triple quadrupole analyserAnalytical column: ACQUITY UPLC®BEH C18 column [100 mm × 2.1 mm] with a 1.7 μm particle sizeMobile phase: [A] 0.1% formic acid in water and [B] acetonitrileElution programme: 0 minutes – 1% B at progressed to 99% B at 10 minutes and then returned to the initial conditions[95]

List of abbreviations: ACN: acetonitrile; dSPE: dispersive solid-phase extraction; ESI: electrospray ionization; EtOAc: ethylacetate; FA: formic acid; FUSLE: focused ultrasonic solid-liquid extraction, HPLC: high-performance liquid chromatography; HRMS: high-resolution mass spectrometry; LCL: lowest calibrated level; LLE: liquid-liquid extraction; MAE: microwave-assisted extraction; MDL: method detection limit; MQL: method quantification limit; MRM: multiple reaction monitoring; MS: mass spectrometry; MS/MS: tandem mass spectrometry; NSAIDs: non-steroidal anti-inflammatory drugs; SIM: selected ion monitoring; SPE: solid-phase extraction; SRM: selected reaction monitoring; UAE: ultrasound-assisted extraction; UPLC: ultra-performance liquid chromatography; UV: ultraviolet light.

2.4 Conclusion and Future Trends

Despite the undoubtedly impressive development of research methodologies that has been made, there are still numerous methodological challenges to overcome. Isolation and pre-concentration of analytes remains a key step in environmental analysis. Significant dilution of pharmaceuticals in seawater samples and condensation of contaminants in wastewater require modification of existing SPE procedures. Furthermore, most SPE sorbents are disposable, which is costly and contrary to the principles of green analytical chemistry. Therefore, the development of suitable sample preparation methods that fit within the principles of green analytical chemistry remains a necessary and challenging task. Alternative sampling methods, such as composite samples or passive samplers, can provide a more representative chemical profile. In addition, an inappropriate extraction method can affect matrix effects, which are indicated as a major problem in the analysis of trace pharmaceuticals using the LC/MS technique. Matrix effects can limit the usefulness of coupled techniques in quantitative analysis, especially when performing compound determinations in environmental, food, wastewater or biological samples. Typically, suppression or enhancement of the analyte response is accompanied by reduced precision and accuracy of subsequent measurements. Various ways to reduce the influence of matrix components, including the use of isotopically labelled standards, changes in mass spectrometer operating conditions and chromatographic conditions, and modifications to the sample extraction procedure can be used [31]. If matrix effects cannot be minimized sufficiently, appropriate calibration techniques to determine matrix effect values are currently in practice. Further work in this area should be carried out and, in particular, standardisation of methodologies should be attempted.

In recent years, the performance of LC instrumentation, in particular HRMS, has increased, and other tools, e.g. HILIC and IMS, have been recognized as promising additions for the analysis of difficult compounds. It is also necessary to carry out research primarily aimed at the identification of a broad spectrum of pharmaceuticals, including the use of non-target and suspect screening approaches. Many different data processing strategies have been developed in recent years. However, structure elucidation remains a difficult and time-consuming task. In the future, it is likely that data processing and software capabilities will increase, enabling approaches to process large amounts of data. The reproducibility and comparability of non-target and suspect screening is already being discussed and should become an important research topic in the near future.

References

      1 1 Roig, B. and D’Aco, V. (2016). Distribution of pharmaceutical residues in the environment. In: Pharmaceuticals in the Environment, 1st edn (ed., R.E. Hester and R.M. Harrison), 34–69. Cambridge: Royal Society of Chemistry. doi: 10.1039/9781782622345.

      2 2 Kümmerer, K. (2008). Pharmaceuticals in the environment – a brief summary. In: Pharmaceuticals

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