Determination of neopterin in urine of industrial workers by HPLC.

This study aimed to determine neopterin levels in the urine of industrial workers by the high-performance liquid chromatography method. Intra- and inter-day precision values for neopterin in urine were less than 3.14, and accuracy (relative error) was better than 3.00%. The limits of detection and quantification of neopterin were 0.3 and 1.0 ng/mL, respectively. Also, the developed method was applied to real samples to determine the neopterin levels in the urines of industrial workers, who have been exposed to various chemicals such as formaldehyde, heavy metals and thinners. Urine neopterin levels of industrial workers including auto painters, bodywork and furniture workers were statistically compared with healthy volunteers. The highest and lowest values of urinary neopterin for industrial workers were obtained 908.96 and 119.86 µmol/mol, respectively. Our investigation demonstrates that there is a meaningful difference in urinary neopterin levels between the workers and the control groups (P<0.05). Workers in the auto paint, body and furniture business may have been exposed to a toxic environmental exposure in their occupation. As a result, an increase in the concentration of neopterin in the urine may be important in the diagnosis and treatment of various diseases.

Determination and pharmacokinetic study of riociguat by UPLC-MS/MS in human plasma.

Pulmonary hypertension (PH) is frequent in the general population and is linked to an increased risk of death. Riociguat is a kind of endothelin receptor antagonist that is often used to treat PH. For pharmacokinetic studies and the determination of riociguat in PH patients, a new, quick, easy, and sensitive UPLC-MS/MS approach was designed and validated. Riociguat and irbesartan (IS) were detected using ESI in positive ion and multiple reaction monitoring mode, respectively, by monitoring the mass transitions m/z 423.0 â†’ 391.0 and 429.1 â†’ 206.9. A reverse-phase C18 column (5 µm, 4.6 × 150 mm) was used with an isocratic mobile phase of water containing 0.1 % formic acid-acetonitrile (25:75, v/v) at a flow rate of 1 ml/min for chromatographic separation. In the range of 5-400 ng/ml, the calibration curve was linear and had a good correlation coefficient (0.9972). This is the first UPLC-MS/MS technique that has been developed and validated for determining riociguat from human plasma. The developed analytical method was extensively validated for linearity, selectivity, specificity, accuracy, precision, sensitivity, stability, matrix effect and recovery, according to FDA criteria. The devised approach was successfully used for a pharmacokinetic research and riociguat determination in PH patients.

Evaluation of anticholinesterase effect of some Epilobium species and quantification of hyperoside by HPLC.

This article presents the evaluation of anticholinesterase effects of aerial parts of Epilobium angustifolium, E. stevenii and E. hirsutum and isolated flavonoids from E. angustifolium, and quantification of the flavonoids by HPLC. Besides, the highest acetylcholinesterase inhibition was seen in the EtOAc sub-extracts of E. angustifolium and E. stevenii (36.51 ± 1.88 and 39.89 ± 3.09%, respectively), whereas EtOAc sub-extract of E. angustifolium had the best butyrylcholinesterase inhibition (62.09 ± 1.98%). Hyperoside showed strong inhibition activity on both enzymes. The active EtOAc sub-extract of E. angustifolium was quantitatively analyzed for their content of hyperoside (quercetin-3-O-ß-D-galactoside) by HPLC. The content of hyperoside in EtOAc sub-extract of E. angustifolium was detected as 3.312%. The anatomical structures of the stem, leaf, sepal, petal, anther, and filament of E. angustifolium were investigated. The anatomical properties given in this study provide a description of E. angustifolium.[Formula: see text].

Evaluation of Serum Trace Element Levels and Biochemical Parameters of COVID-19 Patients According to Disease Severity.

While the COVID-19 disease progresses mildly or asymptomatically in some people, its progression is severe and symptomatic in others, and it is an issue that requires a scientific response regarding the disease. The present study includes 60 people infected with COVID-19, and the cases were divided into the following groups: asymptomatic, mild, moderate, and severe. Serum Zn, Se, and Cu levels of these groups were analyzed by ICP-MS. All measurements in the patients were compared with those of 32 healthy individuals. When the patient group is compared with the control group, the serum Zn and Se concentrations were statistically low (p < 0.001) in the patient group. Serum Zn level decreased significantly in 4 different patient groups compared to the control group. Although the serum Se level decreased in all four patient groups compared to the control group, the change in Se level was statistically significant only in the severe and mild patient groups. This study examined serum Zn, Se concentrations, and biochemical parameters in patients with different severity of COVID-19, compared them with healthy individuals, and revealed new targets for diagnosis and treatment by revealing those data that may be important.

Metabolomics approach: Interpretation of changes in rat plasma metabolites after solifenacin treatment

Abstract Changes in metabolite levels of patients using the long-term drug can be comprehensively demonstrated by pharmacometabolomic studies. In this study, biological alterations induced by the administration of solifenacin succinate were investigated with a pharmacometabolomics approach on rat metabolism. Plasma samples obtained from rats were analyzed by LC-Q- TOF/MS/MS. METLIN and HMDB databases were used to identify metabolites. Data were processed and classified with MATLAB 2017b. 53 m/z values were found to be significantly different between the drug and control groups (p ≤ 0.01 and fold analysis > 1.5) and identified by comparing METLIN and HMDB databases. According to multivariate data analysis, changes in arachidonic acid, thromboxane A2, palmitic acid, choline, calcitriol, histamine phosphate, retinyl ester, l-cysteine, l-leucine, beta-alanine, l-histidine levels were found to be statistically significant compare to the control group. Differences in the biosynthesis of phenylalanine, aminoacyl-tRNA, tyrosine, tryptophan, metabolism of glycerophospholipid, cysteine, methionine, histidine, arachidonic metabolism have been successfully demonstrated by the metabolomics approach. Our study provides important information to explain the efficacy and toxicity of chronic administration of solifenacin succinate

The serum amino acid profile in COVID-19.

The pandemic of the coronavirus disease (COVID-19) caused by SARS-CoV-2 affects millions of people worldwide. There are still many unknown aspects to this infection which affects the whole world. In addition, the potential impacts caused by this infection are still unclear. Amino acid metabolism, in particular, contains significant clues in terms of the development and prevention of many diseases. Therefore, this study aimed to compare amino acid profile of COVID-19 and healthy subject. In this study, the amino acid profiles of patients with asymptomatic, mild, moderate, and severe/critical SARS-CoV-2 infection were scanned with LC-MS/MS. The amino acid profile encompassing 30 amino acids in 142 people including 30 control and 112 COVID-19 patients was examined. 20 amino acids showed significant differences when compared to the control group in COVID-19 patient groups with different levels of severity in the statistical analyses conducted. It was detected that the branched-chain amino acids (BCAAs) changed in correlation with one another, and L-2-aminobutyric acid and L-phenylalanine had biomarker potential for COVID-19. Moreover, it was concluded that L-2-aminobutyric acid could provide prognostic information about the course of the disease. We believe that a new viewpoint will develop regarding the diagnosis, treatment, and prognosis as a result of the evaluation of the serum amino acid profiles of COVID-19 patients. Determining L-phenylalanine and L-2-aminobutyric levels can be used in laboratories as a COVID-19-biomarker. Also, supplementing COVID patients with taurine and BCAAs can be beneficial for treatment protocols.

A Sensitive UPLC-MS/MS Method for the Determination of Flurbiprofen in Rat Plasma: Application to Real Sample.

For the quantification of flurbiprofen in rat plasma, a simple UPLC-MS/MS method with high sensitivity and short retention time for flurbiprofen was developed and validated using specific parameters. Etodolac was used as internal standard. The transitions (precursor to the product) of flurbiprofen and internal standard were obtained using the electrospray ionization in the negative ion multiple reaction monitoring mode, 243.2 â†’ 199.2, 286.2 â†’ 212.1, respectively. For chromatographic separation, C18 column was used for the stationary phase and gradient elution was used for the mobile phase. This mobile phase consisted of a methanol (A) and a 5 mM ammonium formate solution (B), which varied at a flow rate of 0.4 mL/min. For flurbiprofen, LLOQ was determined as 5 ng/mL. Quantification of flurbiprofen in the rat plasma with a linear calibration curve of 5-5000 ng/mL (r > 0.9991 for plasma) is possible with a retention time of 1.89 min. The total analysis time of the method was 3 min. The proposed method was validated. The intraday and inter-day precision (RSD%) and accuracy (RE%) were within 10% in all cases for flurbiprofen. The stability of flurbiprofen was evaluated under conditions such as short-term, long-term, autosampler and freeze/thaw. After method validation, flurbiprofen was succesfully quantified in real rat plasma samples.

Differential N-glycosylation profiling of formalin-fixed paraffin-embedded (FFPE) invasive ductal carcinoma tissues using MALDI-TOF-MS.

Invasive ductal carcinoma (IDC) is the most common type of breast cancer. As dynamic changes of the glycome are closely associated with complex diseases, they have become a focal point of cancer research involving predictive and prognostic markers. Formalin-fixed paraffin-embedded (FFPE) clinical specimens are representative of the tumor environment and are thus utilized in studies on cancer related research and biomarker discovery. Further studies on differential N-glycosylation profiling of IDC cancer tissues are necessary in order to understand the biological role of glycans in cancer and to evaluate their predictive ability. In this study, matrix assisted laser desorption ionization-mass spectrometry (MALDI-MS)-based analyses were conducted for determining differential N-glycosylation patterns of IDC. Two different derivatization methods, namely, 2-aminobenzoic acid (2-AA) labeling and linkage-specific sialic acid esterification, were used for the analysis of N-glycans. Forty-seven 2-AA labeled and fifty ethyl esterified N-glycans were identified by MALDI-MS. In statistical analyses conducted for 2-AA-labeled N-glycans, the relative amounts of 32 N-glycans and prevalence of 15 N-glycan traits showed significant (p < 0.05) differences between cancer and normal tissues; and in such analyses for the ethyl-esterified N-glycans, the relative amounts of 27 N-glycans and prevalence of 17 N-glycan traits showed significant (p < 0.05) differences between them. It was found that mainly high mannose N-glycans, including H5N2, H6N2, and H7N2, and two fucosylated compositions (H3N3F1 and H5N5F1) showed strong discrimination between IDC and controls. In addition, compared with the controls, high mannose N-glycans were observed to be up-regulated in IDC whereas bisecting N-glycans were down-regulated.

Metabolomic profiling of liver tissues after acute administration of vardenafil in rats.

Erectile dysfunction (ED) diseases have almost affected 100 million men all over the world. Orally administered phosphodiesterase 5 (PDE 5) inhibitors are the most used pharmaceutical formulations for the treatment of ED. In this study, it is aimed to investigate the metabolomics feature of orally administered vardenafil in rats. To carry out the experimental procedure eight male Wistar albino rats were used. Their livers were gently removed and metabolomics profiles of each sample were determined by UPLC Q-TOF MS. Identification of metabolites was achieved by the METLIN database. Cluster analysis was also performed via Principle Component Analysis. Several metabolites were identified and results were evaluated by XCMS software. UPLC Q-TOF MS could be successfully applied to profile biomarkers and help us understand the molecular mechanisms of vardenafil usage. It was concluded that the level of some metabolites, responsible for the collagen synthesis and Kreb's cycle, has been statistically significant after the vardenafil administration.

N-glycan profiling of papillary thyroid carcinoma tissues by MALDI-TOF-MS.

Papillary thyroid carcinoma (PTC) is a type of thyroid cancer whose incidence rate has increased recently all over the world. Glycosylation is a crucial post-translational modification (PTM) for the regulation of thyroid hormone synthesis in thyroid glands. However, our knowledge regarding the N-glycosylation change in PTC is limited. To the best of our knowledge, this is the first study to profile glycans in PTC tissues by mass spectrometry. Herein, we have analyzed the N-glycans of formalin-fixed paraffin-embedded (FFPE) tissues of patients diagnosed with PTC in a matched case-control study. Using MALDI-TOF(/TOF)-MS, 35 enzymatically released N-glycan compositions were characterized. The statistical analyses showed significant differences including six N-glycan compositions (p < 0.001) between patients and controls. It was determined that four of them (H5N4E1, H5N4F1E1, H5N4F1L1E1 and H5N4F1E2, E: α2,6-linked sialic acid; L: α2,3-linked sialic acid) were up-regulated in PTC tissues, whereas two N-glycans (H8N2 and H9N2) found to be down-regulated. Besides, a significant difference was found in six different N-glycan traits. Variants of PTC (follicular, classical, hurtle cell) were also studied to define specific N-glycan change for each variant.

A novel, rapid and sensitive UPLC-MS/MS method for the determination of macitentan in patients with pulmonary arterial hypertension.

Macitentan is an endothelin receptor antagonist commonly used in the treatment of pulmonary arterial hypertension (PAH). A novel, rapid, simple and sensitive UPLC-MS/MS method was developed and validated for pharmacokinetic study and the determination of macitentan in PAH patients. Macitentan and bosentan, which are used as internal standards, were detected using atmospheric pressure chemical ionization in positive ion and multiple reaction monitoring mode by monitoring the mass transitions m/z 589.1 → 203.3 and 552.6 → 311.5, respectively. Chromatographic separation was performed on a reverse-phase C18 column (5 µm, 4.6 × 150 mm) with an isocratic mobile phase, which consisted of water containing 0.2% acetic acid-acetonitrile (90:10, v/v) at a flow rate of 1 mL/min. Retention times were 1.97 and 1.72 min for macitentan and IS, respectively. The calibration curve with high correlation coefficient (0.9996) was linear in the range 1-500 ng/mL. The lower limit of quantitation and average recovery values were determined as 1 ng/mL and 89.8%, respectively. This method is the first UPLC-MS/MS method developed and validated for the determination of macitentan from human plasma. The developed analytical method was fully validated for linearity, selectivity, specificity, accuracy, precision, sensitivity, stability, matrix effect and recovery according to US Food and Drug Administration guidelines. The developed method was applied successfully for pharmacokinetic study and the determination of macitentan in PAH patients.

Determination of olanzapine for therapeutic drug monitoring in schizophrenia patients by LC/MS method.

Olanzapine is an atypical antipsychotic drug from the thienobenzodiazepine family which displays efficacy in patients with schizophrenia and related psychoses. A novel LC/MS method was developed and validated for determination of olanzapine in schizophrenia patients' plasma. A liquid-liquid extraction procedure was carried out using 5 mL diethyl ether-diisopropyl ether mixture (1:1, v/v). Average recovery of the extraction procedure was 94.8%. Chromatographic separation was performed on reversed-phase C18 column (250 × 2.0 mm, 5 µm) using mixture of deionized water (trifluoro acetic acid 0.1%)-acetonitrile (20:80, v/v) as mobile phase at a flow rate of 1 mL/min. Irbesartan was used as internal standart and total run time was 2.5 min. Mass spectrometric analysis were carried out in selective-ion montoring mode, and detected olanzapine at m/z 313.1 and IS at m/z 429.4 in all forms of the ions. The calibration curve of olanzapine was linear in the range 2-300 ng/mL (r2 > 0.9993). The interday and intraday precisions (RSD) were <7.55%, and accuracy was >7.59% (n = 6). The proposed study was successfully validated with respect to the US Food and Drug Administration guidelines.

The effect of thiamine and its metabolites on peripheral neuropathic pain induced by cisplatin in rats.

Thiamine pyrophosphate (TPP) is the active metabolite of thiamine. This study aimed to investigate the effects of thiamine and TPP on cisplatin-induced peripheral neuropathic pain (PNP). Male albino Wistar type Rattus norvegicus were divided into six groups (n=6) that received 2 mg/kg cisplatin (CIS), 25 mg/kg thiamine (TM), 2 mg/kg cisplatin+25 mg/kg thiamine (CTM), 25 mg/kg TPP (TPP), 2 mg/kg cisplatin+25 mg/kg TPP (CTPP), or distilled water (healthy group; HG) for 8 days intraperitoneally. Analgesic effect was measured with a Basile Algesimeter. IL-1ß, malondialdehyde (MDA), total glutathione (tGSH), thiamine, and TPP were determined in blood samples. Histopathological examinations were performed on removed sciatic nerves. The percent analgesic effects of the CTM and CTPP groups were calculated to be 21.3% and 82.9%, respectively. Increased production of IL-1ß and MDA by cisplatin was inhibited by TPP, while it was not inhibited by thiamine. Conversion of thiamine to TPP significantly decreased in the CIS group. Histopathological and biochemical investigations demonstrated that hyperalgesia and sciatic nerve damage developed in the CIS and CTM groups with low TPP levels. These results indicate that cisplatin inhibits the formation of TPP from thiamine, leading to severe PNP. This finding suggests that TPP may be more beneficial than thiamine for the treatment of cisplatin-induced PNP.

Stability Indicating HPLC Method for the Determination of Fulvestrant in Pharmaceutical Formulation in Comparison with Linear Sweep Voltammetric Method.

This paper describes two rapid, sensitive and specific methods for the determination of fulvestrant in pharmaceutical preparations by high performance liquid chromatography (HPLC) and linear sweep voltammetry (LSV). HPLC method was used to study the degradation behaviour. Fulvestrant was subjected to degradation under the conditions of hydrolysis (acid and alkali), oxidation (30% H2O2). The linearity was established over the concentration range of 5-50 m g mL-1 for LSV and 0.5-20 m g mL-1 for HPLC method. The intra- and inter-day relative standard deviation (RSD) was less than 3.96 and 3.07% for LSV and HPLC, respectively. Limits of quantification were determined as 5.0 and 0.50 m g mL-1 for LSV and HPLC, respectively. No interference was found from tablet excipients at the selected assay conditions. The methods were applied for the quality control of commercial fulvestrant dosage form to quantify the drug and to check the formulation content uniformity.

A new spectrofluorimetric method for determination of losartan potassium in rabbit plasma and its application to pharmacokinetic study.

A new spectrofluorimetric method to determine losartan potassium (LP) in rabbit plasma is described. The method was based on measuring the native fluorescence of LP in acidic medium. Optimum excitation and emission wavelengths were found to be 248 nm and 410 nm, respectively, in methanol that was diluted with a sulfurous acid solution LP was extracted from rabbit plasma by methyl-tertiary-butyl-ether in acidic media and then back extracted with NaOH. The calibration curves were linear between 0.025 and 0.5 µg/mL with a lower limit of detection 0.004 µg/mL. Precision and accuracy values of the method were calculated as lower than 4.97% and ± 5.68, respectively and the recovery of LP from rabbit plasma was higher than 91.1%. In addition, stability studies of LP in rabbit plasma were carried out and demonstrated its good stability at - 20 °C and at room temperature. The developed and validated method was successfully applied for estimating the pharmacokinetic parameters of LP following oral administrations of a single 10 mg LP/kg to rabbits and it could be concluded that the method can be applied to clinical trials.

GC-FID and HPLC-DAD Methods for the Determination of Menadione Sodium Bisulphite Directly and by Converting Menadione Sodium Bisulphite to Menadione in Pharmaceutical Preparation.

was performed in both direct analysis of MSB and analysis of MN by converting MSB to MN with sodium carbonate. GC-FID method was carried out on the HP-5 capillary column GC-FID and HPLC-DAD methods were developed for determination of menadione (MN) and menadione sodium bisulphite (MSB). By means of each method, quantitative analysis of MSB in commercial pharmaceutical using nitrogen gas. HPLC-DAD method was achieved on the reversed phase C8 column by using a mobile phase consisting methanol and water. The calibration curves of GC-FID and HPLC-DAD for both analytes were linear in the same concentration range (0.5-20 µg/mL). Both methods were validated in terms of precision, accuracy, recovery and limits of detection (LOD) and quantitation (LOQ). Although LOD values of HPLC-DAD method (0.010 µg/mL for MN and 0.005 µg/mL for MSB) is lower than obtained values with GC-FID method (0.04 µg/mL for MN and 0.06 µg/mL for MSB), both methods gave similar and favorable results in terms of precision and accuracy. The Student's t-test was applied to investigate the significant of the different between the results of MSB determination with direct analysis of MSB and analysis of MN by converting MSB to MN by means of GC-FID and HPLC-DAD method in dosage form.

Development and validation of UFLC-MS/MS method for determination of bosentan in rat plasma.

A rapid, simple and sensitive UFLC-MS/MS method was developed and validated for the determination of bosentan in rat plasma using etodolac as an internal standard (IS) after liquid-liquid extraction with diethyl ether-chloroform (4:1, v/v). Bosentan and IS were detected using electrospray ionization in positive ion multiple reaction monitoring mode by monitoring the transitions m/z 551.90→201.90 and 288.20→172.00, respectively. Chromatographic separation was performed on the inertsil ODS-4 column with a gradient mobile phase, which consisted of 0.1% acetic acid with 5mM ammonium acetate in water for solvent A and 5mM ammonium acetate in acetonitrile-methanol (50:50, v/v) for solvent B at a flow rate of 0.3mL/min. The method was sensitive with 0.5ng/mL as the lower limit of quantitation (LLOQ) and the standard calibration curve for bosentan was linear (r>0.997) over the studied concentration range (0.5-2000ng/mL). The proposed method was fully validated by determining specificity, linearity, LLOQ, precision and accuracy, recovery, matrix effect and stability. The validated method was successfully applied to plasma samples obtained from rats.

Optimization of a spectrofluorimetric method based on a central composite design for the determination of potassium losartan in pharmaceutical products

Here, a spectrofluorimetric method for the determination of potassium losartan (PL) in pharmaceutical products is described. The effects of critical parameters, pH, acid molarity, and temperature, on the fluorescence intensity of PL were analyzed, and these parameters were optimized using a central composite design (CCD). The highest fluorescent intensity at excitation (λex) and emission (λem) wavelengths of 248 nm and 410 nm, respectively, was achieved using 0.01 M sulfurous acid (pH 2) at 21.6 °C. Under optimum conditions, the method was linear from 0.025-0.5 µg/mL, with a reasonably high correlation coefficient (0.9993). Furthermore, the method was very sensitive (LOQ, 0.006), accurate (RE, ≤7.06), and precise (%RSD, ≤6.51). After development and validation of the method, samples containing PL were analyzed with this method, and the obtained data were statistically compared with those obtained with a previously published reference method using a two one-sided equivalence test (TOST). According to the data, the results from the proposed and reference assays were equivalent.

Descreve-se método espectrofluorométrico para a determinação de losartana potássica (PL) em produtos farmacêuticos. Os efeitos de parâmetros críticos (pH, molaridade ácida e temperatura) na intensidade da fluorecência foram otimizados usando o planejamento de componente central (DCC). A mais alta intensidade fluorescente com λex=248 nm e λem= 410 nm foi obtida usando ácido sulfúrico 0.01 M (pH 2) e 21.6 ºC. Nas condições ideais, a linearidade do método foi estabelecida na faixa de concentração de 0.025-0.5 µg/mL com coeficiente de correlação bastante elevado (0.9993). Além disso, o método foi muito sensível com valor de LOQ 0.006, exato (RE≤7.06) e preciso (RSD%≤6.51). Depois do desenvolvimento e validação do método, amostras de medicamentos contendo PL foram analisadas com este método e os resultados obtidos foram comparados estatisticamente com método de referência, publicado anteriormente, usando o Teste de equivalência TOST (Teste de Equivalência Unilateral). De acordo com os dados estatísticos, os resultados do ensaio de referência e do método proposto foram equivalentes.

Investigation of Behavior of Forced Degradation of Lidocaine HCl by NMR Spectroscopy and GC-FID Methods: Validation of GC-FID Method for Determination of Related Substance in Pharmaceutical Formulations.

The forced degradation study of lidocaine HCl was carried out according to the ICH guideline Q1A (R2). The degradation conditions were assessed to be hydrolysis, oxidation, photolysis and dry heat during 24 h, 48 h and 72 h and then the samples were investigated by GC-FID method and nuclear magnetic resonance (NMR) spectroscopy. According to these results, the degradation products were not observed in all reaction conditions during the 72 h period. Only spectral changes in the 1H and 13C-NMR spectrum were observed in hydrogen peroxide and acid degradation. As a result of this degradation, n-oxide was formed. After acid-induced degradation with HCl, the secondary amine salt was formed. Furthermore, trifluoroacetic acid (TFA) was used as the acidic media, and the decomposition products were observed. A simple and reliable gas chromatography method with flame ionization detection (GC-FID) was developed and validated for the determination of lidocaine HCl in pharmaceutical formulations in the form of a cream and injections. The GC-FID method can be used for a routine analysis of lidocaine HCl in pharmaceutical formulations and the proposed method, together with NMR spectroscopy, can be applied in stability studies.

Determination of insulin in humans with insulin-dependent diabetes mellitus patients by HPLC with diode array detection.

A simple and reliable high-performance liquid chromatographic method with diode array detection has been developed and validated for the determination of insulin in human plasma. A good chromatographic separation was achieved on a C18 column with a mobile phase consisting of acetonitrile and 0.2M sodium sulfate (pH 2.4), 25:75 (v/v). Its flow rate was 1.2 mL/min. Calibration curve was linear within the concentration range of 0.15-25 µg/mL. Intra-day and inter-day relative standard deviations for insulin in human plasma were less than 6.3 and 8.5%, respectively. The limits of detection and quantification of insulin were 0.10 and 0.15 µg/mL, respectively. Also, this assay was applied to determine the pharmacokinetic parameters of insulin in eight insulin-dependent diabetes mellitus patients after subcutaneous injection of 25 IU of Actrapid HM.