Simultaneous determination of five constituents of areca nut extract in rat plasma using UPLC-MS/MS and its application in a pharmacokinetic study.

Areca nuts have been used as a traditional Chinese medicine (TCM) for thousands of years. Recent studies have shown that it exhibits good pharmacological activity and toxicity. In this study, the pharmacokinetics of five major components of areca nut extract in rats were investigated using a highly sensitive ultra-performance liquid chromatography coupled with triple quadrupole mass spectrometry (UPLC-MS/MS) method. Arecoline, arecaidine, guvacoline, guvacine, and catechin were separated and quantified accurately using gradient elution with mobile phases of (A) water containing 0.1 % formic acid-10 mM ammonium formate, and (B) methanol. The constituents were detected under a timing switch between the positive and negative ion modes using multiple reaction monitoring (MRM). Each calibration curve had a high R2 value of >0.99. The method accuracies ranged -7.09-11.05 % and precision values were less than 14.36 %. The recovery, matrix effect, selectivity, stability, and carry-over of the method were in accordance with the relevant requirements. It was successfully applied for the investigation of the pharmacokinetics of these five constituents after oral administration of areca nut extract. Pharmacokinetic results indirectly indicated a metabolic relationship between the four areca nut alkaloids in rats. For further clarification of its pharmacodynamic basis, this study provided a theoretical reference.

Development of a Two-Dimensional Liquid Chromatographic Method for Analysis of Urea Cycle Amino Acids.

The urea cycle has been found to be closely associated with certain types of cancers and other diseases such as cardiovascular disease and chronic kidney disease. An analytical method for the precise quantification of urea cycle amino acids (arginine, ornithine, citrulline, and argininosuccinate) by off-line two-dimensional liquid chromatography (2D-LC) combined with fluorescence-based detection was developed. Before analysis, the amino acids were derivatised with 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F) to obtain NBD-amino acids. The first dimension involved the reversed-phase separation, in which NBD derivatives of urea cycle amino acids were completely separated from each other and mostly separated from the 18 NBD-proteinogenic amino acids. The samples were eluted with stepwise gradient using 0.02% trifluoroacetic acid in water-acetonitrile as the mobile phase. In the second dimension, an amino column was used for the separation of NBD-ornithine, -citrulline, and -argininosuccinate, while a sulfonic acid column was used to separate NBD-arginine. The developed 2D-LC system was used to analyse human plasma samples. The fractions of NBD-urea cycle amino acids obtained in the first dimension were collected manually and introduced into the second dimension. By choosing appropriate mobile phases for the second dimension, each NBD-urea cycle amino acid eluted in the first dimension was well separated from the other proteinogenic amino acids and interference from endogenous substance. This could not be achieved in the first dimension. The urea cycle amino acids in human plasma sample were quantified, and the method was well validated. The calibration curves for each NBD-urea cycle amino acid showed good linearity from 3 (ASA) or 15 (Orn, Cit, and Arg) to 600 nM, with correlation coefficients higher than 0.9969. The intraday and interday precisions were less than 7.9% and 15%, respectively. The 2D-LC system is expected to be useful for understanding the involvement of the urea cycle in disease progression.

In vitro bloodbrain barrier permeability study of four main active ingredients from Alpiniae oxyphyllae fructus.

The fruits of Alpinia oxyphylla Miq., a broadly utilized traditional Chinese medicine, have a number of effects on the central nervous system (CNS). The main active constituents of Alpiniae oxyphyllae fructus (AOF) were nootkatone, tectochrysin, chrysin and protocatechuic acid. An immortalized human brain microvascular endothelial cell (hCMEC/D3) and astrocyte (HA1800) coculture model was used to investigate the permeability of the blood-brain barrier (BBB). The validation of ultrahigh-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) methods for the four compounds was conducted following industry guidelines. Calibration curves were generated with mean coefficients (R2) better than 0.99. The inter-day and intra-day precisions were less than 8.53% and 7.12%, respectively. The accuracies were lower than ± 11.57%, and recoveries were greater than 86.07%. The samples of the transport experiment were examined, and the apparent permeability coefficients (Papp) were calculated. The efflux ratios of the four compounds are all less than 2. The Papp values of protocatechuic acid, chrysin, nootkatone, tectochrysin were at the level of 10-5, 10-6, 10-6, and 10-7 cm/s, respectively. All four compounds crossed the BBB by passive diffusion, with protocatechuic acid having high permeability, and tectochrysin having poor permeability. This research indicated the permeability of protocatechuic acid, chrysin, nootkatone and tectochrysin through the BBB and offered a foundation for related research on AOF in the treatment of CNS illnesses.

An on-line heart-cutting two-dimensional liquid chromatography method for intracellular 2-hydroxyglutarate enantiomers.

D-2-Hydroxyglutarate (D-2-HG) is an oncometabolite that induces cancer cell survival and growth. D-2-HG is produced by mutations in isocitrate dehydrogenases 1 and 2. L-2-HG has different roles than the D-form, and chiral discrimination is important for elucidating the exact roles of the 2-HG enantiomers. In this study, an analytical method for 2-HG enantiomers was developed using on-line heart-cutting two-dimensional liquid chromatography (2D-LC) with fluorescence detection. Fluorescence derivatization of 2-HG with 4-nitro-7-piperazino-2,1,3-benzoxadiazole (NBD-PZ) was performed using 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride, a hydrophilic condensing reagent, at 70 °C for 30 min. The first dimension on the octadecylsilyl column was aimed at separating NBD-PZ-2-HG from other compounds obtained via derivatization or from biological fluids. The NBD-PZ-2-HG peak was fractionated into a sample loop and automatically injected into the second dimension. In the second dimension, a CHIRALPAK IC column separated NBD-PZ-D- and L-2-HG with a resolution of 2.14. The limits of quantification were 0.25 pmol per injection for NBD-PZ-D-2-HG and-L-2-HG. The precision values were below 6.58%, and the accuracies were 88.2-92.8%. The intracellular concentrations of D-2-HG and L-2-HG in the cancer cells were 13.5 ± 0.4 and 9.9 ± 0.3 pmol per 1.0 × 106 cells, respectively. The developed method will be useful for elucidating the role of 2-HG enantiomers in cancer cells.

Integrated untargeted fecal metabolomics and gut microbiota strategy for screening potential biomarkers associated with schizophrenia.

Schizophrenia (SZ) is a serious neurodevelopmental disorder. As the etiology of SZ is complex and the pathogenesis is not thoroughly understood, the diagnosis of different subtypes still depends on the subjective judgment of doctors. Therefore, there is an urgent need to develop early objective laboratory diagnostic biomarkers to screen different subtypes of patients as early as possible, and to implement targeted prevention and precision medicine to reduce the risk of SZ and improve patients' quality of life. In this study, untargeted metabolomics and 16S rDNA sequencing were used to analyze the differences in metabolites and gut microflora among 28 patients with two types of schizophrenia and 11 healthy subjects. The results showed that the metabolome and sequencing data could effectively discriminate among paranoid schizophrenia patients, undifferentiated schizophrenia patients and healthy controls. We obtained 65 metabolites and 76 microorganisms with significant changes, and fecal metabolite composition was significantly correlated with the differential genera (|r|>0.5), indicating that there was a regulatory relationship between the gut microbiota and the host metabolites. The gut microbiome, as an objective and measurable index, showed good diagnostic value for distinguishing schizophrenia patients from healthy people, especially with a combination of several differential microorganisms, which had the best diagnostic effect (AUC>0.9). Our results are conducive to understanding the complicated metabolic changes in SZ patients and providing valuable information for the clinical diagnosis of SZ.

Improvement of an Automated Sample Injection System for Pillar Array Columns to Increase Analytical Reproducibility.

In our previous study, we developed an automatic sample injection system for pillar array columns for quantitative analysis. An autosampler was used to maintain a constant sample injection volume. However, the sample was diluted during injection using the autosampler, thus deteriorating the analytical reproducibility. In this study, we have substituted the autosampler with a syringe pump to overcome the abovementioned problem and improve the system. Sample dilution was avoided by filling the entire capillary with the sample at a constant rate. This improved system also increased the analytical reproducibility. In the previous system, the relative standard deviation (RSD) exceeded 17% of the peak height for coumarin dyes. In contrast, the improved system decreased the RSD to the range 1.2-1.8%. The analytical reproducibility was evaluated by using five types of amino acids. The RSD of each peak height was within 3.0%, confirming good reproducibility. These results indicate that the sample injection method developed in this study can be applied to biological sample analyses as a simple quantitative analysis method for pillar array columns.

Ion-pair Reversed-phase Liquid Chromatographic Separation of Oligonucleotides.

Therapeutic oligonucleotides have recently been approved in the United States, the EU, and Japan. Hence, the analysis of oligonucleotides is an important topic in drug development. Liquid chromatographic techniques are commonly used for purity verification and the determination of oligonucleotides. In ion-pair reversed-phase separation, several parameters, such as the pore size of the stationary phase, mobile phase additives, and column temperature, were investigated using three types of oligonucleotides (18, 19, and 20 mer). All of the investigated parameters could influence the separation, and they are expected to be useful for optimizing oligonucleotide separation.

The CD44/COL17A1 pathway promotes the formation of multilayered, transformed epithelia.

At the early stage of cancer development, oncogenic mutations often cause multilayered epithelial structures. However, the underlying molecular mechanism still remains enigmatic. By performing a series of screenings targeting plasma membrane proteins, we have found that collagen XVII (COL17A1) and CD44 accumulate in RasV12-, Src-, or ErbB2-transformed epithelial cells. In addition, the expression of COL17A1 and CD44 is also regulated by cell density and upon apical cell extrusion. We further demonstrate that the expression of COL17A1 and CD44 is profoundly upregulated at the upper layers of multilayered, transformed epithelia in vitro and in vivo. The accumulated COL17A1 and CD44 suppress mitochondrial membrane potential and reactive oxygen species (ROS) production. The diminished intracellular ROS level then promotes resistance against ferroptosis-mediated cell death upon cell extrusion, thereby positively regulating the formation of multilayered structures. To further understand the functional role of COL17A1, we performed comprehensive metabolome analysis and compared intracellular metabolites between RasV12 and COL17A1-knockout RasV12 cells. The data imply that COL17A1 regulates the metabolic pathway from the GABA shunt to mitochondrial complex I through succinate, thereby suppressing the ROS production. Moreover, we demonstrate that CD44 regulates membrane accumulation of COL17A1 in multilayered structures. These results suggest that CD44 and COL17A1 are crucial regulators for the clonal expansion of transformed cells within multilayered epithelia, thus being potential targets for early diagnosis and preventive treatment for precancerous lesions.

Quantification of Intracellular Thiols by HPLC-Fluorescence Detection.

Biothiols, such as cysteine and glutathione, play important roles in various intracellular reactions represented by the redox equilibrium against oxidative stress. In this study, a method for intracellular thiol quantification using HPLC-fluorescence detection was developed. Thiols were derivatized with a thiol-specific fluorescence derivatization reagent, viz. ammonium 7-fluoro-2,1,3-benzoxadiazole-4-sulfonate (SBD-F), followed by reversed-phase separation on an InertSustain AQ-C18 column. Six different SBD-thiols (homocysteine, cysteine, cysteinylglycine, γ-glutamylcysteine, glutathione, and N-acetylcysteine as an internal standard) were separated within 30 min using a citric buffer (pH 3.0)/MeOH mobile phase. The calibration curves of all the SBD-thiols had strong linearity (R2 > 0.999). Using this developed method, the thiol concentrations of human chronic myelogenous leukemia K562 cell samples were found to be 5.5-153 pmol/1 × 106 cells. The time-dependent effect of a thiol scavenger, viz. N-ethyl maleimide, on intracellular thiol concentrations was also quantified. This method is useful for elucidating the role of intracellular sulfur metabolism.

Fast analysis using pillar array columns: Quantification of branched-chain α-keto acids in human plasma samples.

Branched-chain α-keto acids (BCKAs, namely, α-ketoisovaleric acid (KIV), α-ketoisocaproic acid (KIC), and α-keto-ß-methylvaleric acid (KMV)) are related to many diseases such as myeloid leukemia, liver cancer, and diabetes mellitus. A rapid quantitative analytical method for BCKAs using pillar array columns was developed. α-Keto acids were labeled with 1,2-diamino-4,5-methylenedioxybenzene (DMB), followed by their separation on octadecylsilane-treated pillar array columns with MeOH/H2O as the mobile phase. Five DMB-labelled α-keto acids including the internal standard were separated in 160 s. The lower limits of quantification for DMB-α-keto acids were 2-5 µM. The intra- and interday precisions were 2.9-6.6 % and 5.2-10.7 %, respectively. The developed method was applied to BCKA quantification in human plasma samples; KIV, KIC, and KMV concentrations were determined to be 13.8, 24.2, and 15.2 µM, respectively. The method realized rapid, sensitive, and precise analysis of BCKAs and can be applied for clinical diagnosis.

Liquid-Chromatographic Methods for Carboxylic Acids in Biological Samples.

Carboxyl-bearing low-molecular-weight compounds such as keto acids, fatty acids, and other organic acids are involved in a myriad of metabolic pathways owing to their high polarity and solubility in biological fluids. Various disease areas such as cancer, myeloid leukemia, heart disease, liver disease, and lifestyle diseases (obesity and diabetes) were found to be related to certain metabolic pathways and changes in the concentrations of the compounds involved in those pathways. Therefore, the quantification of such compounds provides useful information pertaining to diagnosis, pathological conditions, and disease mechanisms, spurring the development of numerous analytical methods for this purpose. This review article addresses analytical methods for the quantification of carboxylic acids, which were classified into fatty acids, tricarboxylic acid cycle and glycolysis-related compounds, amino acid metabolites, perfluorinated carboxylic acids, α-keto acids and their metabolites, thiazole-containing carboxylic acids, and miscellaneous, in biological samples from 2000 to date. Methods involving liquid chromatography coupled with ultraviolet, fluorescence, mass spectrometry, and electrochemical detection were summarized.

Synthesis of sheet-like polypyrrole nanowires for the microextraction of trace residues of pyrethroid pesticides in human plasma and molecular dynamics-aided study of adsorption mechanism.

The synthesized sheet-like polypyrrole (ppy) nanowires were used as solid phase extraction materials, followed by gas chromatography-mass spectrometry (GC-MS) for the detection of traces residues of pyrethroid pesticides in human plasma. A multiresidue method was developed and verified for the determination of trace pyrethroid residues (transfluthrin, allethrin, resmethrin, fenpropathrin, etofenprox, fenvalerate) in human plasma. In this study, using the cationic surfactant cetyltrimethylammonium bromide (CTAB) as a soft template, ppy nanowires with regular morphology were prepared by oxidative polymerization. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and other techniques were employed for characterization. Molecular dynamics analyses were used to simulate the adsorption mechanism of each pyrethroid and ppy nanowires. Based on density analysis, molecular recognition analysis, and binding energy, the van der Waals force was considered as an important driving force for the adsorption of pyrethroids and ppy nanowires. The limits of detection (LOD) of six pyrethroids were 0.008-0051 ng mL-1, and the limits of quantification (LOQ) were 0.028-0.162 ng mL-1. The relative standard deviations of ppy nanowires were 2.12-5.09%, and the recoveries of six pyrethroids ranged from 76.9 to 110.4%. The enrichment factors were within the range of 47.09-51.30. The experimental results showed that the method could be an efficient detection method for trace residue analysis of pyrethroid pesticides in complex biological samples. It would be advantageous for clinical monitoring and toxicological studies of pyrethroids.

Analysis of intracellular α-keto acids by HPLC with fluorescence detection.

Branched-chain keto acids and branched-chain amino acids are metabolites of branched-chain amino acid aminotransferases (BCATs), which catalyzes reversible transamination between them. We found that BCAT1 plays an important role in the progression of myeloid leukaemia, and a method for the analysis of intracellular α-keto acids including branched-chain keto acids was necessary to further investigate their role. In this study, we developed a method to analyze six α-keto acids (α-ketoglutaric acid (KG), pyruvic acid, α-ketobutyric acid, α-ketoisovaleric acid, α-ketoisocaproic acid, and α-keto-ß-methylvaleric acid) in K562 cells by HPLC with fluorescence detection, using 1,2-diamino-4,5-methylenedioxybenzene (DMB) as a derivatization reagent. Because split peaks of DMB-KG were observed when injection samples were too acidic, the derivatization solution was diluted with NaOH solution to obtain a single peak. Limits of detection and limits of quantification were 1.3-5.4 nM and 4.2-18 nM, respectively. Intracellular concentrations of α-keto acids were 1.55-316 pmol/1 × 106 K562 cells. The developed method realized reproducible and sensitive analysis of intracellular α-keto acids. Thus, the method could be used to elucidate the role of BCAT in myeloid leukaemia.

Amino Acid Profiling Study of Psidium guajava L. Leaves as an Effective Treatment for Type 2 Diabetic Rats.

Type 2 diabetes mellitus (T2DM) has become a major disease threatening human health worldwide. At present, the treatment of T2DM cannot cure diabetes and is prone to many side effects. Psidium guajava L. leaves have been reported to possess hypoglycemic activity, and they have been widely used in diabetes treatment in the folk. However, the antidiabetic mechanism has not been clearly explained. Also, the change in amino acid profile can reflect a metabolic disorder and provide insights into system-wide changes in response to physiological challenges or disease processes. The study found that P. guajava L. leaves can decrease fasting blood glucose and lipid levels in type 2 diabetic rats induced by streptozotocin. Through the analysis of amino acid profiling following 20 days of gavage administration, the concentration data were modeled by principal component analysis and orthogonal partial least squares discriminant analysis to find the different metabolites and related metabolic pathways (including cysteine and methionine metabolism, valine, leucine, and isoleucine biosynthesis, phenylalanine, tyrosine, and tryptophan biosynthesis) for the explanation of the hypoglycemic mechanism of P. guajava L., which provides an experimental and theoretical basis for diabetes prediction and for the development of new drugs for the treatment of diabetes.

Analysis of Total Thiols in the Urine of a Cystathionine ß-Synthase-Deficient Mouse Model of Homocystinuria Using Hydrophilic Interaction Chromatography.

Homocysteine and related thiols (cysteine, cysteinylglycine, and glutathione) in the urine of a cystathionine ß-synthase (CBS)-deficient mouse model were quantified using hydrophilic interaction chromatography with fluorescence detection. Urine samples were incubated with tris(2-carboxyethyl) phosphine to reduce disulfide bonds into thiols. After deproteinization, thiols were fluorescently derivatized with ammonium 7-fluoro-2,1,3-benzoxadiazole-4-sulfonate (SBD-F). Homocysteine, cysteine, cysteinylglycine, and glutathione in mouse urine were analyzed using an amide-type column with a mobile phase of acetonitrile/120 mM ammonium formate buffer (pH 3.0) (81:19). The developed method was well-validated. Thiol concentrations in the urine of CBS-wild type (-WT), -heterozygous (-Hetero), and -knockout (-KO) mice were quantified using the developed method. As expected, total homocysteine concentration in CBS-KO mice was significantly higher than that in CBS-WT and CBS-Hetero mice. The developed method shows promise for diagnoses in preclinical and clinical studies.

Suppression of behavioral activity and hippocampal noradrenaline caused by surgical stress in type 2 diabetes model mice.

BACKGROUND: There has been much discussion recently about the occurrence of neuropsychological complications during the perioperative period. Diabetes is known to be one of the metabolic risk factors. Although the number of patients with diabetes mellitus (DM) has been increasing, the pathophysiology of postoperative neuropsychological dysfunction in DM patients is still unclear. Recently, a deficiency of neurotransmitters, such as monoamines, was reported to be associated with mental disorders. Therefore, we investigated the effects of surgical stress on behavioral activity and hippocampal noradrenaline (NA) level in type 2 diabetes mellitus model (T2DM) mice. METHODS: Eighty-four 6-week-old male C57BL/6J mice were divided into four groups (non-diabetes, non-diabetes with surgery, T2DM, and T2DM with surgery groups). T2DM mice were established by feeding a high-fat diet (HFD) for 8 weeks. At 14 weeks of age, fifteen mice in each group underwent a series of behavioral tests including an open field (OF) test, a novel object recognition (NOR) test and a light-dark (LD) test. In the surgery groups, open abdominal surgery with manipulation of the intestine was performed 24 h before the behavioral tests as a surgical stress. Hippocampal noradrenaline (NA) concentration was examined in six mice in each group by high-performance liquid chromatography. The data were analyzed by the Mann-Whitney U test, and p values less than 0.05 were considered significant. RESULTS: The T2DM group showed significantly increased explorative activity in the NOR test (P = 0.0016) and significantly increased frequency of transition in the LD test (P = 0.043) compared with those in the non-diabetic group before surgery. In T2DM mice, surgical stress resulted in decreased total distance in the OF test, decreased explorative activity in the NOR test, and decreased frequency of transition in the LD test (OF: P = 0.015, NOR: P = 0.009, LD: P = 0.007) and decreased hippocampal NA (P = 0.015), but such differences were not observed in the non-diabetic mice. CONCLUSIONS: Mice with T2DM induced by feeding an HFD showed increased behavioral activities, and surgical stress in T2DM mice caused postoperative hypoactivity and reduction of the hippocampal NA level.

One-step ionic liquid-based ultrasound-assisted dispersive liquid-liquid microextraction coupled with high-performance liquid chromatography for the determination of pyrethroids in traditional Chinese medicine oral liquid preparations.

In this study, a simple one-step ionic liquid-based ultrasound-assisted dispersive liquid-liquid microextraction technique was coupled with high-performance liquid chromatography for the analysis of four pyrethroids in three kinds of traditional Chinese medicine oral liquid preparations: simotang oral liquid, kangbingdu oral liquid, and huaji oral liquid. The extraction parameters were examined to improve extraction efficiency. The optimum extraction conditions were 50 µL of 1-octyl-3-methylimidazolium hexafluorophosphate utilized as the extraction solvent and 800 µL of acetonitrile applied as the dispersive solvent. The extraction was assisted by ultrasonication for 8 min. The limits of detection for the four pyrethroids were within 0.007-0.024 mg L-1, and the limits of quantitation ranged between 0.023 and 0.080 mg L-1. The accuracy of the pyrethroid determination ranged from 80.1 to 106.4%. It was indicated that the proposed ionic liquid-based ultrasound-assisted dispersive liquid-liquid microextraction method had an easy operation and was accurate and environmentally friendly. This approach has potential for the analysis of pyrethroids in traditional Chinese medicine oral liquid preparations.

Investigation of the interaction between serotonin-related compounds and phenylboronate moieties in monolithic silica disk-packed spin columns.

Solid-phase extraction technologies are widely used for sample pretreatment in bioanalysis. Monolithic silica disk-packed spin columns modified with phenylboronate moieties have been developed for the selective extraction of cis-diol compounds such as catecholamines. However, in our preliminary studies, serotonin was found to also be extracted in this treatment, along with catecholamines. In this study, the interaction between serotonin-related compounds (serotonin, tryptophan, 5-hydroxy-tryptophan and 5-hydroxyindoleacetic acid) and phenylboronate moieties was investigated. We found that only serotonin was extracted with phenylboronate-modified monolithic silica, whereas tryptophan, 5-hydroxy-tryptophan and 5-hydroxyindoleacetic acid were not. Hydrophobic interactions rather than ionic interactions were the primary factor for the adsorption of serotonin to phenylboronate. Finally, the selective pretreatment procedure for catecholamines was improved: thus, the method could be applied for the pretreatment of bio-samples.

Optimization of tris(2-carboxyethyl) phosphine reduction conditions for fast analysis of total biothiols in mouse serum samples.

In this study, we investigated suitable conditions for the reduction of disulfides in mouse serum samples by tris(2-carboxyethyl) phosphine (TCEP) for fast analysis of total biothiols. Disulfides were reduced with TCEP, and then, thiols were derivatized with the fluorogenic reagent, ammonium 7-fluoro-2,1,3-benzoxadiazole-4-sulfonate (SBD-F). Interference peaks on chromatograms of mouse serum samples disappeared when the TCEP reaction was conducted on ice instead of at room temperature, which is used classically. Low-molecular-weight disulfides, such as cystine and glutathione disulfide, were nearly completely reduced by TCEP on ice. Six SBD-biothiols (homocysteine, cysteine, cysteinylglycine, glutathione, γ-glutamylcysteine, and N-acetylcysteine) were separated within 7.5 min on a sulfoalkylbetain-type column (ZIC-HILIC: 150 × 2.1 mm i.d., 3.5 µm), without interference peaks. The developed method showed good linearity and reproducibility, with inter- and intra-day precisions of less than 3%.

A Modified QuEChERS Method for Determination of Pyrethroid Residues in Traditional Chinese Medicine Oral Liquids by High-Performance Liquid Chromatography.

Pyrethroid residues in traditional Chinese medicines have been a serious threat to the health and treatment of patients. However, because of the matrix complexity of traditional Chinese medicine, the detection of pyrethroid residues remains a challenge. Therefore, we developed a QuEChERS method coupled with high-performance liquid chromatography and ultraviolet detection (HPLC-UV) for the determination of pyrethroid pesticides in three kinds of traditional Chinese medicine oral liquid preparations, and we investigated and optimized the extraction conditions. The matrix effect was estimated in the organic solvent and the actual samples by comparing the slopes of calibration curves, and the results showed that the matrix effect is not significant when using the modified QuEChERS method. The pyrethroid pesticides could be completely separated in 30 min. The linear correlation coefficients were more than 0.999, and the recoveries of all the pyrethroid pesticides ranged from 87.2% to 104.8%. The intra-day precisions (n = 5) were 2.44-4.62%, and the inter-day precisions (n = 5) were 1.06-3.02%. Moreover, the limits of detection were in the range of 0.007-0.018 ng mL-1, while the limits of quantitation were in the range of 0.022-0.057 ng mL-1. This simple, low-cost, and highly sensitive analytical method can be a potential tool for the analysis of pyrethroid residues in traditional Chinese medicine oral liquid preparations.