Table 2.

Experimental conditions for several antibiotics.

Antibiotic	Column Type	Mobile Phase	Program’s Elution	Detector	References
Cefpiramide and relative impurities	1D: Kromasil C8 analytical column (250 mm × 4.6 mm, 5 µm). 2D: Shimadzu Shim-pack GISS C18 analytical column (124 mm × 2.1 mm, 1.9 µm).	1D: (A) 30 mM phosphate/methanol (75:25, v/v) and (B) phosphate buffer (30 mM, pH 7.5)/methanol (50:50, v/v) / 2D: (A) ammonium formate solution (10 mM) and (B) methanol.	1D: gradient conditions: Time (min) B% 0            0 12          0 32          100 33          0 The mobile phase flow rate was 0.80 mL/min. 2D: gradient conditions: Time (min) B% 0                5 5                95 5.5–9          5 The mobile phase flow rate was 0.30 mL/min.	Ion trap/time-of- flight mass spectrometer (Shimadzu Corp., Kyoto, Japan), equipped with an electrospray ionization (ESI) source in positive and negative mode.	[39]
Polymerized impurities of cephalosporins: cefodizime, cefmenoxime, and cefonicid	1D: Xtimate SEC-120 analytical column (7.8 mm × 30 cm, 5 m). 2D: Method A: Shimadzu Shim-pack GISS C18 analytical column (50 mm × 2.1 mm, 1.9 m). Method B/C: ZORBAX SB-C18 analytical column (4.6 × 150 mm, 3.5 m).	1D: (A) 0.005 mol/L dibasic sodium phosphate solution and (Β) 0.005 mol/L sodium dihydrogen phosphate solution (61:39, v/v)] acetonitrile v/v)]. 2D: Method A: (A) ammonium formate solution (10 mM) and (B) acetonitrile. Method B: (A) acetic acid solution (0.1%, v/v) and (B) acetonitrile. Method C: (A) ammonium formate solution (10 mM) and (B) ammonium formate (8 mM) in [acetonitrile/water (4:1, v/v)] solution.	1D: gradient conditions: Time (min) B% 0            5 18          20 20          5 The mobile phase’s flow rate was 0.80 mL/min and the injection volume was 30 μL. 2D: gradient elution Method A: Time (min) B% 0                5 5                95 5.5–9          5 Method B: Time (min) B% 0            5 12          15 45          60 55          5 Method C: Time (min) B% 0            12 9            16 15          20 18          40 19          12 The mobile phase flow rate was 0.40 mL/min.	Ion trap/time-of- flight mass spectrometer (Shimadzu Corp., Kyoto, Japan), equipped with an electrospray ionization (ESI) source in positive and negative mode.	[41]
Impurities in cefonicid sodium	1D: GRACE Alltima C18 analytical column (250 mm × 4.6 mm, 5 μm)/2D: Shimadzu Shim-pack GISS C18 analytical column (50 mm × 2.1 mm, 1.9 μm).	1D: (A) 0.02 mol·L−1 ammonium dihydrogen phosphate solution in H2O with 40% aqueous ammonia solution) and (B) methanol. 2D: (A) 10 mmol·L−1 ammonium formate solution and (B) methanol.	1D gradient elution: Time (min) B% 0–10            16 10–30          60 41                16 The mobile phase flow rate was 0.80 mL/min. 2D gradient elution: Time (min) B% 0                5 5                95 5.5–9          5 The mobile phase flow rate was 0.30 mL·min−1.	Ion trap/time-of- flight mass spectrometer (Shimadzu Corp., Kyoto, Japan), equipped with an electrospray ionization (ESI) source in positive and negative mode.	[40]
Meropenem	1D: Shim-Pack CLC ODS (6 mm × 150 mm, 5 μm, Shimadzu, Kyoto, Japan)/2D: Shim-pack GISS C18 column (50 mm × 2.1 mm, 1.9 μm, Shimadzu, Kyoto, Japan) used at 40 °C.	1D: (A) 0.1% triethylamine/acetonitrile (96:4, v/v) and (B) 0.1% triethylamine/acetonitrile (70:30, v/v) / 2D: (A) 10 mM ammonium formate and (Β) methanol.	1D: Gradient elution Time (min) B% 0            0 18          10 55          60 56          0 The flow rate was 1.5 mL·min−1. 2D: Gradient elution mode: Time (min) B% 0                5 5                95 5.5–9          5 The flow rate was 0.30 mL min−1.	Ion trap/time-of- flight mass spectrometer (Shimadzu Corp., Kyoto, Japan), equipped with an electrospray ionization (ESI) source in positive and negative mode.	[43]
Amoxicillin	1D: Shim-pack GIS C18 (4.6 mm × 250 mm, 5 μm)/2D: Shim-pack GIS C18(4.6 mm × 150 mm, 5 μm).	1D: ammonium dihydrogen phosphate/tetrahydrofuran/methanol (730∶12.5∶300) / 2D: 1% formic acid aqueous solution (A)/acetonitrile (B).	Isocratic conditions: the flow rate was 1 mL/min.	UV detector at 254 nm.	[46]
Benzylpenicillin, Flucloxacillin, Amoxicillin Riperacillin, the beta-lactamase inhibitors Clavulanic acid and Clindamycin, Macrolide antibiotics, and Tazobactam clindamycin	1D: XBridge® C8 Direct Connect HP column (10 µm particle size, 2.1 × 30 mm)/2D: Acquity UPLC® BEH C18 (1.7 µm particle size, 2.1 × 100 mm i.d.; Waters) analytical column equipped with an Acquity UPLC® BEH C18 VanGuard precolumn (1.7 µm particle size, 2.1 × 5 mm i.d.; Waters).	1D: 100% H2O with 0.1% formic acid/2D: (A) water containing 0.1% formic acid and (B) acetonitrile containing 0.1% formic acid.	1D: Isocratic elusion at a flow rate of 1.0 mL/min. 2D: Gradient elution Time (min) B% 0.0          10 1.8          10 4.5          45 5.0          100 6.0          100 6.1          10 The flow rate was 700 µL/min.	A triple-quadrupole mass spectrometer (TSQ ENDURA) (Thermo Scientific, Reinach, Switzerland), equipped with an electrospray ionization source in positive mode.	[44]
Vancomycin	1D: Reversed-phase Diamonsil C18(2) column (100 mm × 4.6 mm, 5 μm, China; C1). Middle column: a strong cation-exchange column (20 mm × 4.6 mm, 5 μm, ANAX, China; MC). 2D: Inertsil ODS-3 column (150 mm × 4.6 mm, 5 μm, GL Science Inc., Japan; C2).	1D: (A) 20 mmol/L ammonium acetate buffer and (Β) acetonitrile (88:12, v/v)/ 2D: (A) 50.0 mmol/L Ammonium acetate buffer (pH 5.0) and (B) acetonitrile (85:15, v/v), mobile phase C.	1D: isocratic elusion with a flow rate of (A) 1.2 mL/min, (Β) 1.6 mL/min, and (C) 1.5 mL/min.	UV detector at 282 nm.	[42]
Amoxicillin, cloxacillin, oxacillin, and linezolid	1D: Perfusion column (POROS R1/20, 20 m, 2.1 mm × 30 mm, Applied Biosystems, Darmstadt, Germany)/2D: Pentafluorophenyl (PFP) analytical column (Phenomenex Kinetex, 2.6 m, 2 mm × 50 mm, Aschaffenburg, Germany).	1D: (A) water + 0.1% formic acid, (B) MeOH + 0.1% formic acid, (C) water/10 mM ammonium formate, with formic acid, and (D) ACN + 0.1% formic acid.	Isocratic conditions: a flow rate of 4.0 mL/min over 0.70 min. Gradient conditions: Time (min) D% 0               10 0.75          10 3.20          98 3.80          10 3.81          10	A TQD triple-quadrupole mass spectrometer) equipped with an electrospray ionization source (Waters, St Quentin, France) in positive mode.	[45]
Sulfonamides, Beta-agonists, and (Steroid) hormones	Self-made: 1D: Waters HSS Cyano (1.8 µm, 1 × 150 mm), Waters BEH C18 (1.8 µm, 1 × 150 mm), Waters Phenyl (1.8 µm, 1 × 150 mm) and a Phenomenex Kinetix (2.6 µm, 1.0 × 150 mm) column. 2D: Waters Phenyl column (1.7 µm, 2.1 × 50 mm). Commercial LC × LC	1D: (A) water/acetonitrile (90:10) containing 0.1% formic acid and (Β) water/acetonitrile (10:90) containing 0.1% formic acid. 2D: (A) water/acetonitrile (90:10) containing 0.1% formic acid and (B) water/acetonitrile (10:90) containing 0.1% formic acid.	1D gradient conditions: Time (min) B% 0            80 27          80 28          0 2D gradient conditions: Time (min) B% 0            0 45          40 50          100	Ion trap/time-of- flight mass spectrometer (Waldbronn, Germany), was equipped with an electrospray ionization (ESI) source in positive mode.	[48]
The polymerized impurities in cefotaxime sodium and cefepime 2D HPSEC/RP-HPLC system 2D RP-HPLC/RP-HPLC system	1D: a TSK-gel G2000SWxl column (7.8 mm × 30 cm, 5 μm) from TOSOH Corporation (Tokyo, Japan). 2D: Agilent ZORBAX SB-C18 analytical column (4.6 mm × 150 mm, 3.5 μm) (Santa Clara, CA, USA). 1D: Kromasil (Nouryon, Bohus, Sweden) 100-5-C18 analytical column (4.6 mm × 250 mm, 5 μm). 2D: Shimadzu Shim-pack GISS C18 analytical column (50 mm × 2.1 mm, 1.9 μm)	1D: phosphate buffer of dibasic sodium phosphate solution/0.005 mol/L sodium dihydrogen phosphate solution, 61:39 (v/v), and acetonitrile at 95:5 (v/v). 2D: (A) 10 mM ammonium formate solution and (B) acetonitrile. 1D: For cefotaxime sodium injection, the mobile phases were 0.05 M disodium hydrogen phosphate solution (A) and methanol (B). For cefepime, the mobile phases were 0.05 M ammonium dihydrogen phosphate solution (A) and acetonitrile (B). 2D: (A) 10 mM ammonium formate solution and (B) acetonitrile.	1D: Isocratic conditions: a flow rate of 0.50 mL/min 2D: Gradient elution Time (min) B% 0–20            5 20–21          40 21–29          5 The flow rate of the mobile phase was 0.40 mL/min. 1D for cefotaxime, gradient elution: Time (min) B% 0–10            15 10–30          15 30–40          70 40–41          70 41–50          15 The flow rate was 0.8 mL/min and the injection volume was 20 μL. 1D for cefepime: the gradient program was set as follows: Time (min) B% 0                 10 10               10 30               70 40               70 41–50         10 The flow rate was 1.00 mL/min. 2D, gradient conditions: Time (min) B% 0–5            5–95 5.5–5.5       5	1D: PDA detector in the range of 200–400 nm. 2D: UV detection wavelength of 254 nm. 1D: PDA detector in the range of 200–400 nm. 2D: Ion trap/time-of-flight mass spectrometer (Shimadzu Corp., Kyoto, Japan), equipped with an electrospray ionization (ESI) source in positive and negative mode.	[41]