A porous graphitized carbon column hplc method for the quantification of paracetamol, pseudoephedrine, and chlorpheniramine in a pharmaceutical formulation

A simple, rapid, and stability-indicating HPLC method has been developed, fully validated, and applied to the quantification of paracetamol, pseudoephedrine hydrochloride, and chlorpheniramine maleate in a pharmaceutical formulation, using hydrochlorothiazide as an internal standard. Chromatographic separation was achieved isocratically on an RP porous graphitized carbon analytical column (125 × 2.1 mm id, particle size 5 μm) using 5.0 mM ammonium acetate-acetonitrile (35 + 65, v/v) mobile phase at a flow rate of 0.50 mL/min. UV spectrophotometric detection at 220 nm was used. The method had linear calibration curves over the range of 30-70 mg/mL for paracetamol, 1.8-4.2 mg/mL for pseudoephedrine hydrochloride, and 120-280 ng/mL for chlorpheniramine maleate. The intraday and interday RSD values were less than 3.2% for all compounds, while the relative error was less than 2.9%. Accelerated stability studies performed under various stress conditions proved the selectivity of the method. The developed method was applied successfully to QC and content uniformity tests of commercial tablets

Hydrophilic interaction liquid chromatography/positive ion electrospray ionization mass spectrometry method for the quantification of alprazolam and α-hydroxy-alprazolam in human plasma

A hydrophilic interaction liquid chromatography/positive ion electrospray-mass spectrometry (HILIC-ESI/MS) has been developed and fully validated for the quantification of alprazolam and its main metabolite, α-hydroxy-alprazolam, in human plasma. The assay is based on 50μL plasma samples, following liquid-liquid extraction. All analytes and the internal standard (tiamulin) were separated by hydrophilic interaction liquid chromatography using an X-Bridge-HILIC analytical column (150.0mm×2.1mm i.d., particle size 3.5μm) under isoscratic elution. The mobile phase was composed of a 7% 10mM ammonium formate water solution in acetonitrile and pumped at a flow rate of 0.20mLmin-1. Running in positive electrospray ionization and selected ion monitoring (SIM) the mass spectrometer was set to analyze the protonated molecules [M+H]+ at m/z 309, 325 and 494 for alprazolam, α-hydroxy-alprazolam and tiamulin (ISTD) respectively. The assay was linear over the concentration range of 2.5-250ngmL-1 for alprazolam and 2.5-50ngmL-1 for α-hydroxy alprazolam. Intermediate precision was less than 4.1% over the tested concentration ranges. The method is the first reported application of HILIC in the analysis benzodiazepines in human plasma. With a small sample size (50μL human plasma) and a run time less than 10.0min for each sample the method can be used to support a wide range of clinical studies concerning alprazolam quantification. © 2013 Elsevier B.V

The efficacy study of the combination of tripeptide-10-citrulline and acetyl hexapeptide-3. A prospective, randomized controlled study

Background: Bioactive peptides have beneficial effects on the skin. Objective: We investigated to evaluate the effect of acetyl hexapeptide-3 and tripeptide-10 citrulline and the possible synergism between these two peptides. Methods: Twenty-four healthy volunteers were randomized to receive combination of acetyl hexapeptide-3 with tripeptide-10 citrulline (Group G1), tripeptide-10 citrulline (Group, G2), acetyl hexapeptide-3 (Group G3), or neither peptide (Group G4) for 60 days. Skin properties evaluated included skin microtopography, parameters cR2 and cR3, and transepidermal water loss (TEWL) using a skin visioscan and a tewameter, respectively. Results: After 20 days, the measurements between G1 and G2 groups (cR2 P=.045, cR3 P=.044), G2 and G3 groups (cR2 P=.017, cR3 P=.017), G3 and G4 groups (CR2 P=.022), and G2 and G4 groups (cR3 P=.028) from baseline were significant. After 60 days, measurements between groups G1 and G3 (cR2 P=.016, cR3 P=.025), groups G2 and G3 (cR2 P=.044, cR3= P=.044), and groups G1 and G4 (cR2 P=.025) were significant. After 20 days, changes in TEWL between groups G1 and G3 (P=.03), groups G2 and G3 (P=.045), and groups G3 and G4 (P=.025) were significant. After 40 days, changes between groups G2 and G3 (P=.028) and groups G3 and G4 (P=.01) from baseline were significant. Conclusion: Our results confirm the antiwrinkle activity of acetyl hexapeptide-3. A significant decrease in TEWL with acetyl hexapeptide-3 treatment is observed. We provided clinical evidence for the antiwrinkle efficacy of tripeptide-10 citrulline and possibly TEWL. The underlying mechanism by which these two peptides can act synergistically was not clear in this study. © 2017 Wiley Periodicals, Inc

Insights into the mechanism of separation of bisphosphonates by zwitterionic hydrophilic interaction liquid chromatography: Application to the quantitation of risedronate in pharmaceuticals

Bisphosphonates are used to treat various skeletal disorders, as they modulate bone metabolism by inhibition of the osteoclast-mediated bone resorption. These compounds are both polar and ionic, and therefore, by using reversed phase liquid chromatography are eluted rapidly. Hydrophilic interaction liquid chromatography (HILIC) is an advantageous technique for the separation and analysis of polar molecules. As the elution order in HILIC is reversed to reversed phase liquid chromatography, a reasonable retention and selectivity for polar compounds is expected. In this work the retention mechanism of three bisphosponates, namely risedronate, tiludronate and zoledronate, was investigated under zwitterionic HILIC conditions. The key factors influencing the retention of the analytes on a zwitterionic ZIC®-pHILIC column (150.0 × 2.1 mm i.d., 200 Å, 3.5 µm) have been systematically investigated. It was found that apart from partition, electrostatic repulsions play an important role in the retention of bisphosphonates. Peak tailing of risedronate and zoledronate was improved by the addition of sodium pyrophosphate in the mobile phase. A zwitterionic hydrophilic interaction liquid chromatography-photodiode array (HILIC-PDA) method was further optimized and fully validated to quantitate risedronate in commercial film-coated tablets. The calibration curves for risedronate showed good linearity (r ≥ 0.9991) within the calibration range tested. The intra-and inter-day coefficient of variation (CV) values was less than 0.6%, while the relative percentage error (%Er) was less than −2.3%. Accelerated stability studies of risedronate conducted under several degradation conditions including hydrolysis, oxidation and heat demonstrated the selectivity of the procedure. A short-run analysis of not more than 6 min allowed the analysis of large samples per day. The applicability of the method for the quantitation of risedronate was demonstrated via the analysis of commercial tablets containing this compound. © 2019 by the authors. Licensee MDPI, Basel, Switzerland

Quantitation of acetyl hexapeptide-8 in cosmetics by hydrophilic interaction liquid chromatography coupled to photo diode array detection

Bioactive peptides are gaining more and more popularity in the research and development of cosmetic products with anti-aging effect. Acetyl hexapeptide-8 is a hydrophilic peptide incorporated in cosmetics to reduce the under-eye wrinkles and the forehead furrows. Hydrophilic interaction liquid chromatography (HILIC) is the separation technique of choice for analyzing pep-tides. In this work, a rapid HILIC method coupled to photodiode array detection operated at 214 nm was developed, validated and used to determine acetyl-hexapeptide-8 in cosmetics. Chromatogra-phy was performed on a Xbridge® HILIC BEH analytical column using as mobile phase a 40 mM ammonium formate water solution (pH 6.5)-acetonitrile mixture 30:70, v/v at flow rate 0.25 mL min−1 . The assay was linear over the concentration range 20 to 30 µg mL−1 for the cosmetic formulations and 0.004 to 0.007% (w/w) for the cosmetic cream. The limits of quantitation for acetyl hexapeptide-8 were 1.5 µg mL−1 and 0.002% (w/w) for the assay of cosmetic formulations and cosmetic creams, respectively. The method was applied to the analysis of cosmetic formulations and anti-wrinkle cosmetic creams. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

Acidic hydrolysis of bromazepam studied by high performance liquid chromatography. Isolation and identification of its degradation products

Division of Pharmaceutical Chemistry, Department of Pharmacy, University of Athens, Panepistimiopolis, Athens 15771, Greece A kinetic study on the acidic hydrolysis of bromazepam was carried out in 0.01 M hydrochloric acid solution at 25 and 95°C. A reversed-phase HPLC method was developed and validated for the determination of bromazepam and its degradation products. Bromazepam degraded by a consecutive reaction with a reversible first step. Two degradation products were isolated and identified by infrared, 1H and 13C nuclear magnetic resonance and mass spectroscopy. Spectroscopic data indicated that N-(4-bromo-2-(2-pyridylcarbonyl)phenyl)-2-aminoacetamide was the intermediate degradation product of this acid hydrolysis, whereas 2- amino-5-bromophenyl-2-pyridylmethanone was the final one. Therefore, the mechanism of this acid-catalysed hydrolysis involved initial cleavage of the 4,5-azomethine bond, followed by slow breakage of the 1,2-amide bond. Statistical evaluation of the HPLC method revealed its good linearity and reproducibility. Detection limits were 3.8 x 10-7 M for bromazepam, 6.25 x 10-7 M for the intermediate and 8.16 x 10-7 M for the benzophenone derivative

Direct injection liquid chromatography/electrospray ionization mass spectrometric horse urine analysis for the quantification and confirmation of threshold substances for doping control. II. Determination of theobromine

In equine sport, theobromine is prohibited with a threshold level of 2 μgmL-1 in urine, hence doping control laboratories have to establish quantitative and qualitative methods for its determination. Two simple liquid chromatography/mass spectrometry (LC/MS) methods for the identification and quantification of theobromine were developed and validated using the same sample preparation procedure but different mass spectrometric systems: ion trap mass spectrometry (ITMS) and time-of-flight mass spectrometry (TOFMS). Particle-free diluted urine samples were directly injected into the LC/MS systems, avoiding the time-consuming extraction step. 3-Propylxanthine was used as the internal standard. The tested linear range was 0.75-15 μgmL -1. Matrix effects were evaluated analyzing calibration curves in water and different fortified horse urine samples. A great variation in the signal of theobromine and the internal standard was observed in different matrices. To overcome matrix effects, a standard additions calibration method was applied. The relative standard deviations of intra-and inter-day analysis were lower than 8.6 and 7.2%, respectively, for the LC/ ITMS method and lower than 5.7 and 5.8%, respectively, for the LC/TOFMS method. The bias was less than 8.7% for both methods. The methods were applied to two case samples, demonstrating simplicity, accuracy and selectivity. Copyright © 2009 John Wiley & Sons, Ltd

Direct injection LC/ESI-MS horse urine analysis for the quantification and identification of threshold substances for doping control. I. Determination of hydrocortisone

Two simple and rapid LC/MS methods with direct injection analysis were developed and validated for the quantification and identification of hydrocortisone in equine urine using the same sample preparation but different mass spectrometric systems: ion trap mass spectrometry (IT-MS) and time-of-flight mass spectrometry (TOF-MS). The main advantage of the proposed methodology is the minimal sample preparation procedure, as particle-free diluted urine samples were directly injected into both LC/MS systems. Desonide was used as internal standard (IS). The linear range was 0.25-2.5 μg ml -1 for both methods. Matrix effects were evaluated by preparing and analyzing calibration curves in water solutions and different horse urine samples. A great variation of the signal both for hydrocortisone and the internal standard was observed in different matrices. To overcome matrix effects, the unavailability of blank matrix and the excessive cost of the isotopically labeled internal standard, standard additions calibration method was applied. This work is an exploration of the performance of the standard additions approach in a method where neither nonisotopic internal standards nor extensive sample preparation is utilized and no blank matrix is available. The relative standard deviations of intra and interday analysis of hydrocortisone in horse urine were lower than 10.2 and 5.4%, respectively, for the LC/IT-MS method and lower than 8.4 and 4.4%, respectively, for the LC/TOF-MS method. Accuracy (bias percentage) was less than 9.7% for both methods. Copyright © 2008 John Wiley & Sons, Ltd

Direct injection horse urine analysis for the quantification and identification of threshold substances for doping control. III. Determination of salicylic acid by liquid chromatography/quadrupole time-of-flight mass spectrometry

In equine sport, salicylic acid is prohibited with a threshold level of 750∈μg mL-1 in urine; hence, doping control laboratories have to establish quantitative and qualitative methods for its determination. A simple and rapid liquid chromatographic/mass spectrometric method was developed and validated for the quantification and identification of salicylic acid. Urine samples after 900-fold dilution and addition of the internal standard (4-methylsalicylic acid) were directly injected to the liquid chromatography/quadrupole time-of-flight mass spectrometry system. Electrospray ionization in negative mode with full scan acquisition mode and product ion scan mode were chosen for the quantification and identification of salicylic acid, respectively. Run time was 2.0 min. The tested linear range was 2.5-50∈μg mL-1 (after 100-fold sample dilution). The relative standard deviations of intra- and inter-assay analysis of salicylic acid in horse urine were lower than 2.5% and 2.8%, respectively. Overall accuracy (relative percentage error) was less than 3.3%. Method was applied to two real samples found to be positive for salicylic acid, demonstrating simplicity, accuracy, and selectivity. © 2009 Springer-Verlag