Impurity profiling of Compound Amino Acid Injection (6AA) using ion-pair high performance liquid chromatography coupled with corona-charged aerosol detection and high resolution mass spectrometry

One nanoparticle delivers two different neuroprotective amino acids into ischemic brain and protects against neuronal death in rat cerebral ischemia injury

Previous studies have proven that glycine and proline are neuroprotective but have very low permeability through the blood-brain barrier (BBB), which is a major barrier to the application of these neuroprotective amino acids in the therapy of brain injury. In this study, we aimed to develop a therapeutic strategy by which one chitosan nanoparticle could deliver two different neuroprotective amino acids, glycine and proline, into the rat ischemic brain to confer neuroprotection in a rat model of cerebral ischemia-reperfusion (I/R) injury. Using the ion cross-linking method, we developed a preparation in which one chitosan nanoparticle was simultaneously loaded with glycine and proline (AA-NPs). We evaluated the therapeutic potential of AA-NPs in both cell and animal models of cerebral ischemic stroke. We found that the levels of glycine and proline were decreased in the brain tissues of I/R rats. AA-NPs delivered both glycine and proline into the ischemic brain and reduced ischemic neuronal death in both in vitro and in vivo. These results indicated that the dual delivery of glycine and proline via AA-NPs mediated neuroprotective effects, as evidenced by the reduction of neuronal death in both cellular and animal models of ischemic stroke. AA-NPs provide an efficient and potential delivery strategy by which multiple neuroprotective amino acids can be transported into the ischemic brain simultaneously for the treatment of ischemic stroke.

An optimization strategy for charged aerosol detection to linearize the detector response in the multicomponent quantitative analysis of Qishen Yiqi dripping pills

Charged aerosol detection, increasingly recognized for quantifying pharmaceutical compounds with weak ultraviolet absorption, is a universal detection technique for high-performance liquid chromatography (HPLC). Charged aerosol detection shows a non-linear response with increasing analyte concentration over a wide range, limiting its versatility in various analytical applications. In this work, a co-optimization strategy for power function value (PFV) and power laws was proposed and applied to broaden the linear range of the standard curve of saccharides in Qishen Yiqi dripping pills using the HPLC-charged aerosol detection (HPLC-CAD) method. Power function values for all analytes were optimized based on empirical models. Subsequently, the optimum power laws were investigated based on a preferred PFV. Additionally, various regression equations were evaluated to ensure the accuracy and precision of the results. With the optimized PFV and power law, the ordinary least squares model demonstrated a satisfactory fit. The optimal PFVs and power laws expanded the standard curve's linear range by 2.7 times compared to default settings, reducing model uncertainty. This paper presents a vital method for developing a multi-component quantitative HPLC-CAD approach without external data transformation outside the provided software, especially suitable for analytical applications of traditional Chinese medicine with significant quality differences.

Optimization of HPLCCAD method for simultaneous analysis of different lipids in lipid nanoparticles with analytical QbD

Since lipid nanoparticles (LNP) have emerged as a potent drug delivery system, the objective of this study was to develop and optimize a robust high-performance liquid chromatography with charged aerosol detectors (HPLCCAD) method to simultaneously quantify different lipids in LNPs using the analytical quality by design (AQbD) approach. After defining analytical target profile (ATP), critical method attributes (CMAs) were established as a resolution between the closely eluting lipid peaks and the total analysis time. Thus, potential high-risk method parameters were identified through the initial risk assessment. These parameters were screened using Plackett-Burman design, and three critical method parameters (CMPs)-MeOH ratio, flow rate, and column temperature-were selected for further optimization. Box-Behnken design was employed to develop the quadratic models that explain the relationship between the CMPs and CMAs and to determine the optimal operating conditions. Moreover, to ensure the robustness of the developed method, a method operable design region (MODR) was established using the Monte Carlo simulation. The MODR was identified within the probability map, where the risk of failure to achieve the desired CMAs was less than 1%. The optimized method was validated according to the ICH guidelines (linearity: R2 > 0.995, accuracy: 97.15-100.48% recovery, precision: RSD < 5%) and successfully applied for the analysis of the lipid in the LNP samples. The development of the analytical method to quantify the lipids is essential for the formulation development and quality control of LNP-based drugs since the potency of LNPs is significantly dependent on the compositions and contents of the lipids in the formation.

Development and evaluation of a HILIC-MS method for the determination of amino acid and non-amino acid impurities in histidine

Developing analytical methods to assure and control the quality of amino acids has long been a challenge for food ingredient, dietary supplement, and pharmaceutical industries due to the high polarity and the absence of chromophores in many amino acids; the situation worsens further by the lack of information of impurities that could potentially be introduced during the manufacturing processes. Herein we utilize a four-step strategy including impurity identification, method development, sample analysis, and targeted impurity detection and quantitation to demystify the impurity profiles of amino acids. The effectiveness of the approach is highlighted using histidine as an example. Analysis of histidine manufacturing and degradation processes led to the identification of 12 potential impurities of histidine, including amino acids (arginine, lysine, asparagine, aspartic acid, alanine, and glycine) and non-amino acid impurities (histamine, histidinol, 4-imidazoleacrylic acid, 4-imidazoleacetic acid, β-imidazolelactic acid, and urea). A HILIC method using Poroshell 120 HILIC-Z column (2.1 × 100 mm, 2.7 µm) and a mobile phase system consisting of ammonium formate buffer at pH 3.2 in water and 0.1% formic acid in acetonitrile coupled with a single quadrupole mass spectrometer was developed for the detection and quantitation of the proposed impurities. Evaluation of 11 commercial histidine samples using the developed method revealed distinct impurity profiles, as a fingerprint for each sample; seven of the 12 proposed impurities were detected in histidine samples tested. The developed method was evaluated in terms of specificity, linearity, range, accuracy, precision, and sensitivity (LOQ: 2.5-60.6 ng/mL) for its suitability for compendial applications. Given the high degree of overlap between the proposed and the detected impurities, the approach could be utilized to strengthen USP standards for controlling the quality of histidine. Extension of the strategy to the analysis of other amino acids is currently underway.

Analytical Chemistry of Impurities in Amino Acids Used as Nutrients: Recommendations for Regulatory Risk Management

Proteinogenic amino acids are natural nutrients ingested daily from standard foods. Commercially manufactured amino acids are added to a wide range of nutritional products, including dietary supplements and regular foods. Currently, the regulatory risk management of amino acids is conducted by means of setting daily maximum limits of intake. However, there have been no reported adverse effects of amino acid overdosing, while impurities in low-quality amino acids have been identified as causative agents in several health hazard events. This paper reviews the analytical chemistry of impurities in amino acids and highlights major variations in the purity of commercial products. Furthermore, it examines the international standards and global regulatory risk assessment of amino acids utilized in dietary supplements and foods, recommending (1) further research on analytical methods that can comprehensively separate impurities in amino acids, and (2) re-focusing on the regulatory risk management of amino acids to the analytical chemistry of impurities.

Performance of ion pairing chromatography and hydrophilic interaction liquid chromatography coupled to charged aerosol detection for the analysis of underivatized amino acids

The charged aerosol detector (CAD) is frequently employed in liquid chromatography for the analysis of small polar and ionizable compounds such as amino acids and amino sugars, which provide a weak chromophore only. Separation of these compounds is achieved by means of ion pair chromatography (IPC), and, more recently, hydrophilic interaction chromatography (HILIC) techniques. However, as the CAD's response is highly dependent on the mobile phase composition, the substantial differences in the mobile phase composition of IPC and HILIC have a distinct impact on the detector's performance. This study was aimed at systematically comparing the performance of IPC and HILIC when coupled to the CAD. Therefore, the separation techniques characterized by their specific mobile phase compositions were evaluated for their influence on the CAD response and the signal-to-noise ratio (S/N) of the amino acids L-alanine, L-leucine, and L-phenylalanine applying the response surface methodology (RSM). The RSM results derived from flow injection analysis (FIA) indicated that the CAD response and thus the obtainable S/N are significantly higher in HILIC compared to IPC where the S/N decreased with the chain length of the applied ion-pairing reagent. In addition, an IPC and a HILIC method, respectively, were developed for the impurity profiling of the branched-chain amino acids (BCAAs) L-leucine, L-isoleucine, and L-valine. The beneficial effects of the HILIC conditions on the S/N observed under FIA conditions were partly offset by moderate column bleed effects when using an amide functionalized column, which facilitates the separation in the HILIC method. Satisfactory LOQs (3-10 ng on column) were obtained with both methods; however, the HILIC method was found to be slightly superior in terms of sensitivity and separation efficiency.