Hp 1050 autosampler

Concentrations of metformin derivatives were determined by HPLC. The apparatus consisted of an Agilent 1100 binary pump (Agilent Technologies Inc., Wilmington, DE, USA), a 1100 micro vacuum degasser, an HP 1050 Autosampler and an HP 1050 variable wavelength detector, operated at 235 nm. The chromatographic separations were achieved on an Agilent Zorbax SB-C18 analytical column (4.6 mm × 150 mm, 5 μm) (Agilent Technologies Inc., Wilmington, DE, USA) by using isocratic elution of water containing 0.1% formic acid (pH ca. 3.0) and acetonitrile containing 0.1% formic acid with a ratio of 75:25 (v/v). The retention times of the compounds were circa 3.7–4.3 min at a flow rate of 1.0 mL/min at room temperature. The lower limit of quantification for the compounds was 1.0 μM. These HPLC methods were also accurate (100 ± 10% of nominal concentration), precise (RSD% < 10%) and selective (no interfering peaks) over the range 1–100 μM.

HPLC analysis was performed using an Agilent 1100 binary pump (Agilent Technologies Inc., Wilmington, DE, USA), a 1100 micro vacuum degasser, a HP 1050 Autosampler, a HP 1050 variable wavelength detector (operated at 235 nm). The chromatographic separations were achieved on a Supelco SupelcosilTM LC-SI analytical column (4.6 mm × 250 mm, 5 μm) (Supelco Inc., Bellefonte, PA, USA) by using isocratic elution of 25 mM of phosphate buffer with 0.3% of triethylamine at pH 4.7 and ACN with 0.1% of formic acid (30:70, v/v). Effluent was monitored at a wavelength of 254.4 nm, with a flow rate of 1.5 mL/min; the injection volume was 5 µL; retention time of 3.7 min. The column was maintained at 40 °C throughout the analysis.
Standard calibration curves were prepared at different dilutions of CZP: in Milli-Q^® water/ACN (1:1, v/v) with a linear regression coefficient determined in the range 0.5–200 μg/mL, which was 0.9999; in DMSO with a linear regression coefficient determined in the range 0.1–200 μg/mL, which was 1.

HPLC analysis was performed using an Agilent 1100 binary pump (Agilent Technologies Inc., Wilmington, DE, USA), a 1100 micro vacuum degasser, a HP 1050 Autosampler, and a HP 1050 variable wavelength detector (operated at 235 nm). The chromatographic separation was achieved on a Supelco Supelcosil^TM LC-SI analytical column (4.6 mm × 250 mm, 5 μm) (Supelco Inc., Bellefonte, PA, USA) by an isocratic elution of a formic acid 0.1% (v/v) solution in Milli-Q^® water and a formic acid methanol solution (0.1%, v/v) (40:60, v/v). Effluent was monitored at a wavelength of 278.4 nm, with a flow rate of 1 mL/min; the injection volume was 5 µL, retention time of MEL was 3.5 min. The column was maintained at 45.0 ± 0.2 °C throughout the whole analysis.
The standard calibration curves were prepared at different dilutions of MEL in Milli-Q^® water/methanol (1:1, v/v). The linear regression coefficient determined in the range 0.5–200 μg/mL was 0.9999.