HPLC-UV and GC-MS Methods for Determination of Chlorambucil and Valproic Acid in Plasma for Further Exploring a New Combined Therapy of Chronic Lymphocytic Leukemia

Overview of therapeutic drug monitoring and clinical practice

With the rapid development of clinical pharmacy in China, therapeutic drug monitoring (TDM) has become an essential tool for guiding rational clinical drug use and is widely concerned. TDM is a tool that combines pharmacokinetic and pharmacodynamic knowledge to optimize personalized drug therapy, which can improve treatment outcomes, reduce drug-drug toxicity, and avoid the risk of developing drug resistance. To effectively implement TDM, accurate and sophisticated analytical methods are required. By researching the literature published in recent years, we summarize the types of commonly monitored drugs, therapeutic windows, and clinical assays and track the trends and hot spots of therapeutic drug monitoring. The purpose is to provide guidelines for clinical blood drug concentration monitoring, to implement individualized drug delivery programs better, to ensure the rational use of drugs for patients, and to provide a reference for the group to carry out related topics in the future.

A High-Performance Liquid Chromatography—Mass Spectrometry Method for Simultaneous Determination of Vancomycin, Meropenem, and Valproate in Patients with Post-Craniotomy Infection

Vancomycin (VAN), meropenem (MER), and valproate (VPA) are commonly used to treat intracranial infection post-craniotomy and prevent associated epilepsy. To monitor their levels, we developed a novel bioassay based on liquid chromatography–tandem mass spectrometry (LC–MS/MS) for simultaneous determination of these three drugs in human serum and cerebrospinal fluid (CSF). Sample preparation by protein precipitation using acetonitrile was followed by HPLC on a Zorbax 300SB-C8 column (150 mm × 4.6 mm, 5 μm) maintained at 40 °C. The lower limit of quantification (LLOQ) was 5 ng/mL for MER, 0.1 μg/mL for VAN, and 1 μg/mL for VPA in serum and 50 ng/mL for MER, 1 μg/mL for VAN, and 2 μg/mL for VPA in CSF. This method was validated with satisfactory linearity, sensitivity, precision, accuracy, recovery, matrix effects, and stability for all analytes. The assay was then successfully applied to evaluate VPA, MER, and VAN levels in serum and CSF from patients with intracranial infection administrated by intrathecal injection. Compared with intravenous injections, an intrathecal injection can provide sufficient therapeutic effects even if the CSF levels did not reach the effective concentration reported. Our method provided a detection tool to study the effective concentrations of these three drugs in CSF from patients administered via intrathecal injection.

Valproic acid determination by liquid chromatography coupled to mass spectrometry (LC-MS/MS) in whole blood for forensic purposes

Valproic acid (VPA) is a well-known drug prescribed as anti-epileptic. It has a narrow therapeutic range and shows great individual differences in pharmacodynamics and pharmacokinetics. Consequently, the therapeutical drug monitoring (TDM) in patient's plasma is of crucial importance. Liquid chromatography coupled to mass spectrometry (LC-MS/MS) has gained importance in TDM applications for its features of sensitivity, selectivity and rapidity. However, in case of VPA, the LC-MS/MS selectivity could be hampered by the lack of a sufficient number of multiple reaction monitoring (MRM) transitions describing the molecule. In fact, the product ion scan of deprotonated molecules of VPA does not produce any ion and thus most LC-MS/MS methods are based on the detection of the unique MRM transition m/z 143➔143. In this way, the advantages of selectivity in LC-MS cannot be effectively exploited. In the present method, stable analyte adducts were exploited for the determination of VPA in blood. An Acquity HSS C18 column and mobile phases consisting of 5-mM ammonium formate and acetonitrile both added 0.1% formic acid were used. Source worked in negative acquisition mode and parameters were optimized to increase the adduct (m/z 189) and dimer (m/z 287) stability, and their fragmentation were used to increase the selectivity of MRM detection. The method has been validated according to the toxicological forensic guidelines and successfully applied to 10 real blood samples. Finally, the present method showed suitable for the rapid LC-MS/MS detection of VPA in whole blood, demonstrating the possibility to increase specificity by exploiting stable in-source adducts. This should be considered of utmost importance in the case of forensic applications.

Use of TLC-Densitometric Method for Determination of Valproic Acid in Capsules

Determination of valproic acid in the drug was carried out on the aluminum silica gel 60F₂₅₄ plates and using acetone-water-chloroform-ethanol-ammonia at a volume ratio of 30:1:8:5:11 as the mobile phase, respectively. Two methods of detection of valproic acid were used. The first was a 2% aqueous CuSO₄×5H₂O solution, and the second was a 2',7'-dichlorofluorescein-aluminum chloride-iron (III) chloride system. The applied TLC-densitometric method is selective, linear, accurate, precise, and robust, regardless of the visualizing reagent used for the determination of valproic acid in Convulex capsules. It has low limits of detection (LOD) and limits of quantification (LOQ), which are equal to 5.8 μg/spot and 17.4 μg/spot using a 2% aqueous CuSO₄×5H₂O solution as visualizing agent and also 0.32 μg/spot and 0.97 μg/spot using a 2',7'-dichlorofluorescein-aluminum chloride-iron (III) chloride system as visualizing reagent, respectively. The described analytical method can additionally be used to study the identity of valproic acid in a pharmaceutical preparation. The linearity range was found to be 20.00-80.00 μg/spot and 1.00-2.00 μg/spot for valproic acid detected on chromatographic plates using a 2% aqueous CuSO₄×5H₂O solution and the 2',7'-dichlorofluorescein-aluminum chloride-iron (III) chloride system, respectively. A coefficient of variation that was less than 3% confirms the satisfactory accuracy and precision of the proposed method. The results of the assay of valproic acid equal 96.2% and 97.0% in relation to the label claim that valproic acid fulfill pharmacopoeial requirements. The developed TLC-densitometric method can be suitable for the routine analysis of valproic acid in pharmaceutical formulations. The proposed TLC-densitometry may be an alternative method to the modern high-performance liquid chromatography and square wave voltammetry in the control of above-mentioned substances, and it can be applied when other analytical techniques is not affordable in the laboratory.

A new electrochemical DNA biosensor for determination of anti-cancer drug chlorambucil based on a polypyrrole/flower-like platinum/NiCo2O4/pencil graphite electrode

In the current study, DNA immobilization was performed on pencil graphite (PG) modified with a polypyrrole (PPy) and flower-like Pt/NiCo₂O₄ (FL-Pt/NiCo₂O₄) nanocomposite, as a new sensitive electrode to detect chlorambucil (CHB). Energy dispersive X-ray (EDX) analysis, X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques were employed to characterize the synthesized FL-Pt/NiCo₂O₄ and PPy/FL-Pt/NiCo₂O₄ nanocomposites. Moreover, differential pulse voltammetry (DPV) was selected to assess the guanine and adenine electrochemical responses on the DNA sensor. The CHB determination was performed using the maximum currents towards adenine and guanine in the acetate buffer solution (ABS). According to the results, ds-DNA/PPy/FL-Pt/NiCo₂O₄/PGE was able to detect the different concentrations of CHB in the range between 0.018 and 200 μM, with a detection limit of (LOD) of 4.0 nM. The new biosensor was also exploited for CHB determination in real samples (serum, urine and drug), the results of which revealed excellent recoveries (97.5% to 103.8%). Furthermore, the interaction between ds-DNA and CHB was studied using electrochemistry, spectrophotometry and docking whose outputs confirmed their effective interaction.

In the current study, DNA immobilization was performed on pencil graphite (PG) modified with a polypyrrole (PPy) and flower-like Pt/NiCo₂O₄ (FL-Pt/NiCo₂O₄) nanocomposite, as a new sensitive electrode to detect chlorambucil (CHB).

Analytical method validation for related substances in sodium valproate oral solution by gas chromatography

Background

Sodium Valproate is the sodium salt of valproic acid (VPA). Valproic acid is mainly used for the treatment of epilepsy. The specific aim of the study is to develop and validate an optimized method for the determination of six related substances such as N,N-dimethyl valpronamide, valeric acid, 2-methyl valeric acid, 2-ethyl valeric acid, 2-isopropyl valeric acid and 2-n-butyl valeric acid in Sodium Valproate Oral Solution by Gas Chromatography. Chromatographic separations of these six related substances were achieved on DB-FFAP fused silica capillary column (30 m × 0.53 mm) bonded with a 0.5-µm layer of macrogol 20,000 2-nitroterephthalate materials used as stationary phase. The six related impurities were extracted using heptane and monitored by Gas Chromatography coupled with flame ionization detector. The performance of the developed method was assessed by evaluating system suitability, method precision, specificity, linearity and range, ruggedness, accuracy, robustness.

Results

The correlation coefficient was within the acceptance criteria in the range of 0.9998. The evaluated concentrations for Sodium Valproate were in the ranges of 5.05–25.27 ppm. The average recovery values were in the range of 92.4–100.4%. Solution Stability experiments were performed to evaluate the degradation behavior of SVS.

Conclusion

A novel, precise and sensitive GC method was developed, validated and optimized for the determination of six related substances in sodium Valproate oral solution. The results obtained from the validation experiments demonstrated that the method is accurate, precise, linear, specific, sensitive and robust. Hence, the proposed method can be an alternative method, for the determination of related substances in sodium valproate oral solution drug substance.