Optimization and validation of RP-HPLC method for quantification of piperacillin in pharmaceutical formulation and in human blood plasma.

Abstract

Piperacillin, a broad-spectrum antibiotic frequently combined with tazobactam, is widely employed to treat infections caused by both Gram-positive and Gram-negative bacteria as well as anaerobes. Achieving therapeutic plasma concentrations of the drug is essential to ensure clinical efficacy. High-performance liquid chromatography (HPLC) represents a robust approach for accurate quantification of drug levels. In this study, a reverse-phase HPLC method was optimized and validated for the determination of piperacillin in pharmaceutical products and human plasma. Plasma proteins were precipitated with acetonitrile, followed by vortexing and reconstitution of the supernatant with mobile phase before injection. Chromatographic analysis was carried out using a Waters Alliance HPLC system equipped with a UV detector at 218 nm, operating at a flow rate of 1 mL/min. The mobile phase consisted of methanol, water, tetrabutylammonium chloride buffer, and phosphoric acid. The method demonstrated linearity across the range of 0.5–400 μg/mL, with a recovery of 99.9%. The limits of detection and quantification were 0.25 μg/mL and 0.5 μg/mL, respectively. Considerable inter-patient variability in maximum plasma concentrations (Cmax) was observed, even at identical dosing regimens. The developed method is accurate and reliable, and the results underline the importance of personalized dosing strategies based on individual plasma concentration profiles.

 1. Objective

To develop and validate a simple, accurate, and reliable RP-HPLC method for the quantification of piperacillin in pharmaceutical formulations and human plasma.

2. Materials and Reagents

Equipment:

•  Waters Alliance 2695 HPLC system
•  Waters 2996 photodiode array detector
•  XSelect HSS C18 analytical column (250 × 4.6 mm, 5 µm) with guard column (20 × 4.6 mm)
•  Autosampler (20 µL) with refrigerated carousel (5 ± 1 °C)
•  DLAB D3024 centrifuge

Reagents and standards:

•   Piperacillin reference standard (Biosynth Ltd., UK)
•   Commercial formulation ZOYSN (Global Pharma, Pakistan)
•   Methanol, HPLC grade (Dae-Jung Chemicals, Korea)

•   Water, HPLC grade (Dae-Jung Chemicals, Korea)
•   Sodium dihydrogen phosphate (Merck, Germany)
•   Tetrabutylammonium hydroxide, 40% aqueous solution (Merck)
•   Ortho-phosphoric acid (Merck)
•   Human plasma (Ayub Teaching Hospital, Abbottabad, Pakistan)
•   Acetonitrile, HPLC grade

 3. Chromatographic Conditions

 Column: XSelect HSS C18, 250 × 4.6 mm, 5 µm
Mobile phase (isocratic, pH 5.5):

Methanol: 510 mL
Water: 432 mL
  Phosphate buffer: 50 mL
  Tetrabutylammonium hydroxide solution: 8 mL

Flow rate: 1.0 mL/min
Column temperature: 25 °C
Injection volume: 20 µL
UV detection: 218 nm
 Run time: 27 minutes

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 4. Preparation of Standard Solutions

1. Prepare a stock solution of piperacillin at 1 mg/mL in mobile phase.
2. Prepare calibration standards at 0.25, 0.5, 1, 4, 40, 80, 200, and 400 µg/mL.
3. Spike each standard with 100 µL of human plasma to simulate biological matrix conditions.
4. Filter all solutions through 0.25 µm nylon membranes before injection.

5. Sample Preparation

Pharmaceutical formulation: 

Dissolve in mobile phase and filter (0.25 µm).

Patient plasma samples preparation:

  1. Centrifuge blood samples at 4,000 rpm for 10 min.
  2. Mix plasma with acetonitrile (1:3, v/v).
  3. Vortex for 3 min and centrifuge at 12,000 rpm, 10 min, 10 °C.
  4. Collect supernatant and reconstitute with 300 µL of mobile phase.
  5. Filter (0.25 µm) and transfer to HPLC vials.

6. Analytical Procedure

1. Prepare and degas the mobile phase.
2. Equilibrate the column with mobile phase.
3. Inject calibration standards and establish the calibration curve.
4. Inject pharmaceutical and plasma samples.
5. Identify and quantify piperacillin peaks based on retention time.

7. Method Validation

Linearity: 0.5 – 400 µg/mL (R² > 0.999)
Precision: RSD < 2 %
Accuracy: recovery ~99.9 %
LOD: 0.25 µg/mL
LOQ: 0.5 µg/mL
"Validation performed according to FDA guidelines for bioanalytical methods."

 8. Practical Notes

* Store standard solutions at 2–8 °C.
* Use only HPLC-grade solvents.
* Ensure sample stability before analysis.
* Clean and purge HPLC system after each run.