Simultaneous determination of 14 oral antihyperglycaemic drugs in human urine by liquid chromatography–tandem mass spectrometry

Response surface optimization of a vortex-assisted dispersive liquid-liquid microextraction method for highly sensitive determination of repaglinide in environmental water by HPLC/UV

A vortex-assisted dispersive liquid–liquid microextraction (DLLME) method, mated to chemometrics and combined with HPLC/UV detection was optimized and validated for enrichment and determination of repaglinide in environmental samples using nateglinide as an internal standard (IS). A phosphate buffer (10 mM, pH 2.5): acetonitrile (45:55, v/v) was used as a mobile phase with a flow rate of 1 mL/min in an isocratic elution mode. Chemometrics-assisted optimization was performed using a quadratic integrated d-optimal design. The developed model assessed the statistical significance of the independent variables and their interactions to attain the optimum conditions revealing that extractant type, extractant volume and pH are the most influential factors. Optimization of the extraction procedures was performed with the aid of Design Expert 8® software, which suggested 58 different experiments. The optimal conditions were 30 µL of 1-octanol as extractant, 100 µL of acetonitrile as a disperser at pH 8. Under the optimized conditions, the method showed linearity over the range of 1–100 ng/mL with a limit of detection of 0.4 ng/mL. The accuracy, the intra- and inter-day precision were assessed, the %recoveries were found to be between 98.48 and 100.81% with %RSD lower than 1.3. Using chemometrics in method optimization helped achieve the maximum possible enrichment with the least effort, time, and reagents while considering all possible interactions between variables.

Optimized Box-Behnken experimental design based response surface methodology and Youden's robustness test to develop and validate methods to determine nateglinide using kinetic spectrophotometry

Selective and straightforward kinetic spectrophotometric methods were developed to quantify nateglinide (NTG) in pharmaceutical dosage forms. Fixed time (ΔA) and the equilibrium methods utilized the reaction of NTG with 1-chloro-2,4-dinitrobenzene (CDNB) in dimethyl sulfoxide (DMSO) with heating at 80 °C for 25 min to form a stable yellow-coloured Meisenheimer complex, which absorbs maximally at 421 nm. The optimization was achieved by utilizing the Box-Behnken experimental design (BBD) combined with response surface methodology (RSM). In which three significant factors were studied, namely, CDNB volume (A), heating temperature (B) and heating time (C) against the absorbance as a response. Method validation presented the International Conference on Harmonisation (ICH) parameters such as specificity, selectivity, linearity, precision, accuracy, limit of detection (LOD), limit of quantitation (LOQ), robustness and solution stability. The LOD and LOQ values were 0.48, 1.46, and 0.21, 0.62 µg/ml, respectively, for a fixed time (ΔA) and equilibrium methods with the linear dynamic range of 1-15 µg/ml. Furthermore, Youden's robustness test using factorial combinations of the selected analytical parameters was performed and investigated its influence with alternative conditions. All results were reproducible and quickly adopted for routine analysis of NTG in pharmaceutical formulations and laboratory preparations.

A new RP-HPLC method as an auxiliary tool for optimization of sample preparation procedures for tracing of PPCPs of different hydrophilicities

Recently, pharmaceutical and personal care products (PPCPs) have received considerable attention because of their increasing use. Analysis of PPCPs presents a significant analytical challenge, with high-performance liquid chromatography (HPLC) in reversed-phase mode, as the most widely used analytical technique. To facilitate the optimization of the procedures that are applied in the early stages of sample preparation, a simple and fast HPLC method is proposed in this work for the separation of some PPCPs with a wide range of hydrophilicity. Two columns were evaluated (Atlantis dC18 and Discovery HS F5); as for mobile phases: a formate buffer (40 mmol L-1, pH 4) and methanol were tested in a gradient mode. The fluorinated column allowed better separation in a shorter time and better resolution for all analytes (Rs > 1). The proposed method delivered good performance for the tracing of PPCPs and is a suitable alternative to traditional C18-based HPLC methods.

Characteristics of Korean patients with methamphetamine use disorder based on the quantitative analysis of methamphetamine and amphetamine in hair

Methamphetamine (MA) is a highly addictive central nervous system stimulant. MA use disorder is characterized by a chronic, relapsing brain disease that is enhanced by a dynamic process of repeated use and withdrawal. The analysis of MA and its metabolite, amphetamine (AM), in hair is routinely performed in forensic laboratories for illegal MA use determination. However, few studies regarding the clinical application of hair analysis have been conducted to monitor the treatment of MA use disorder. Herein, the characteristics of Korean patients with MA use disorder were investigated based on drug abuse screening instruments and quantitative analysis of MA and AM in hair. A HPLC-MS/MS method for the quantification of MA and AM in hair was validated and clinically applied to healthy subjects (HS, n = 30, male) as well as current (CP, n = 33, male) and former (FP, n = 22, male) MA use disorder patients. The validation results of the hair analysis method showed high selectivity, accuracy, and precision with acceptable linearity within the calibration range (0.05-5.0 ng/mg). The limit of detection (LOD) and limit of quantification for both MA and AM were 0.05 ng/mg. The concentrations of MA and AM ranged from ≤ LOD to 166 ng/mg and from not detected (ND) to 9.15 ng/mg in the CP group and from ND to 6.14 ng/mg and from ND to 0.32 ng/mg in the FP group, respectively. No correlation was observed between the hair MA concentrations and the NIDA-modified ASSIST, DUDID extended, or DAST scores in both groups. The hair MA concentrations showed advantages for differentiating the CP and FP groups compared with the scores provided by the above-mentioned drug abuse screening instruments.

Simultaneous detection of 24 oral antidiabetic drugs and their metabolites in urine by liquid chromatography-tandem mass spectrometry

Drugs are the most frequent cause of hypoglycemia. Though the drug history is usually obvious in diabetic patients, the diagnosis could be a challenge in patients without a history of such exposure. Screening for oral antidiabetic drugs has been recommended as part of the hypoglycemia workup in patients without diabetes. Many published analytical methods of oral antidiabetic agents were usually of limited coverage and restricted to parent drugs only. In the current study, a liquid chromatography-tandem mass spectrometry (LC-MS/MS) analytical system for the simultaneous detection of 24 oral antidiabetic drugs and their metabolites in urine was established and validated. The method covered both conventional as well as the newer antidiabetic drugs such as dipeptidyl peptidase-4 inhibitors and sodium-glucose cotransporter-2 inhibitors. Following sample preparation by solid phase extraction, analytes were detected by LC-MS/MS with multiple reaction monitoring triggered enhanced product ion scan. The method was successfully applied to 233 cases of unexplained hypoglycemia, with 83 oral antidiabetic drugs detected in 51 of the urine samples.