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Despite the fact that strong routine separation methodologies can give reliable specificity and validity at usual working pharmaceuticals concentrations, they may fail at very low concentration levels. This poses considerable challenges for researchers inves-tigating product purity and therapeutic drug monitoring. Sensitivity enhancement pro-cedures are thus required to maximize the performance of separation techniques. Large volume injection, solid phase extraction/solid phase enrichment (SPE/SPEn), pre-, post-, and in-column derivatization, as well as the use of sensitive detection devices are the simplest strategies for improving sensitivity of the separation-based analytical techniques. Large volume injection of samples with online SPE/SPEn coupled with separation techniques increased sensitivity and improved detection as well as quantification limits without affecting peak shape and system performance. Although the primary purpose of derivatization is to improve sensitivity and selectivity, greener derivatization is growing in popularity and should be considered in analytical chemistry. In general, two strategies are essential for accomplishing greener derivatization goals. The first is the search for and use of ecologically acceptable derivatizing reagents, solvents, and reaction conditions. The second is miniaturization and automation of analytical methods. This review discusses significant advances in separation-based analytical techniques, specifically enrichment approaches and detector signal improvement for pharmaceutical quantification in various matrices at very low concentration levels. As a result of improved analytical systems setup in drug assays, the possibility of high-throughput analyses was also highlighted.

A rapid back flushed (BF) direct sample injection (DSI) high-performance liquid chromatography (HPLC) with UV detection (BF-DSI-HPLC-UV) has been developed to determine terbinafine (TERB) in human serum. For online solid phase extraction step, an isocratic mobile phase of phosphate buffer saline (pH 7.4) at 1 mL/min and a short protein-coated ODS column (PC-ODS-column) were used for the purification and enrichment of TERB. Two different chromatographic modes of PC-ODS-column were simultaneously operated. Macromolecular proteins were extracted by size-exclusion liquid chromatography, while TERB trapping and enrichment were achieved through reversed-phase liquid chromatography. The clear fraction containing TERB was transferred from the PC-ODS-column by BF mode onto the quantification step through a high pressure switching valve. An analytical mobile phase consisting of 80% methanol and 1% triethylamine in distilled deionized water (pH) 6 at 1 mL/min was used for the final separation on an ODS analytical column. TERB was quantified and detected by UV-detector at 224 nm. The proposed method showed high correlation coefficient (0.999) over the concentrations range 4-1600 ng/mL with recoveries ranging from 98.48 to 93.86%. Measurement of TERB concentration in serum after administration of a single dose of 250 mg oral tablet was used to evaluate the applicability of the BF-DSI-HPLC-UV for pharmacokinetic study.

Ciprofloxacin belongs to the fluoroquinolone family, which exhibits biological activity against both gram-positive and gram-negative bacteria. The previously mentioned drug is of utmost importance due to the high incidence of resistance caused by other antibiotics. Thus, numerous research studies has been conducted to determine Ciprofloxacin as well as its metabolites owing to their contribution in the drug’s biological activity. Liquid chromatography, gas chromatography, capillary electrophoresis and other separation techniques were used to develop, adapt and implement analytical techniques for the drug analysis. Other studies has made use of the hyphenation between liquid chromatography and mass spectrometry for Ciprofloxacin assay for quality control, biological fluids, animal tissues and numerous sample types. The recent advances in the ionization methods has led to the use of direct mass spectrometry techniques to analyze various sample types. This mini review aims to focus on the various analytical techniques and recent technologies implemented for Ciprofloxacin analysis.

Graphical abstract, Introduction In recent years, analytical screening methods for simultaneous detection of multivitamins have gained substantial attention to ensure quality and public confidence in dietary supplements. Even so, few analytical methods have been proposed for simultaneous analysis of multivitamin constituents due to the large divergence in chemical characteristics. Objectives In the present study, the objective was to develop a simple and rapid direct nano-electrospray ionization-tandem mass spectrometry (DI-nano-ESI-MS/MS) method for targeted detection of water soluble vitamins, fat soluble vitamins, amino acids, royal jelly, ginkgo biloba, and ginseng in a dietary supplement. The applicability of dilute-and-shoot-based DI-nano-ESI-MS/MS to analyze the same tested compounds and their related metabolites in clinical samples was also examined. Methods Intact urine mixed with the ionization solvent was loaded (4-μL aliquot) into a nanospray (NS) capillary of 1-μm tip diameter. The NS capillary was then fitted into an off-line ion source at a distance of 5 mm from MS aperture. The sample was directly injected by applying a voltage of 1.1 kV, producing a numerous of m/z peaks for analysis in mere minutes. Results The DI-nano-ESI-MS/MS method successfully identified almost all dietary supplement components, as well as a plethora of component-related metabolites in clinical samples. In addition, a new merit of the proposed method for the detection of index marker and chemical contaminants as well as subspecies identification was investigated for further quality evaluation of the dietary supplement. Conclusions The previous findings illustrated that DI-nano-ESI-MS/MS approach can emerge as a powerful, high throughput, and promising analytical tool for screening and accurate detection of various pharmaceuticals and ingredient in dietary supplements as well as biological fluids.

Mass spectrometry is one of the most powerful techniques for detection and identification. Due to its sensitivity and selectivity, exact mass of analytes, and in effect, their relative fragments, allow for total structure information. As so, mass spectrometry has now played a major role in branches such as forensics, academic research, environmental studies, and manufacturing quality control. The most recent technological advances have not been to the body of the mass spectrometer, but rather to the first step only, the ion source. The ionization mechanism has been found to impact a plethora analytical results including, but not limited to, the target analytes to be ionized, the relation between sensitivity and ionization efficiency, and the sample inlet flux in relation to analysis time. This mini review focuses on the latest technologies in ambient ionization of mass spectrometry including desorption electrospray ionization, paper spray ionization, laser ablation electrospray ionization, and direct nano-electrospray ionization.

A rapid, reliable and precise integrated solid-phase extraction (SPE) and reversed-phase liquid chromatography method was developed and validated to determine bupivacaine in human serum using single protein-coated analytical columns. The protein-coated columns were packed with four different sorbents: TSK-ODS, LiChrosorb RP-8, LiChrosorb RP-2 and μ-Bondapak CN-bonded silica. The method involved direct injection of serum sample onto the columns for trapping of the analyte, clean-up from weakly retained serum endogenous components, as well as the final separation. The protein-coated columns operated in two different chromatographic modes. Serum proteins were extracted and cleaned up by SPE, whereas the final separation of bupivacaine was based on reversed-phase chromatography. The protein-coated TSK-ODS column resulted in more accurate peak integration and more reproducible results. A linear relationship between the concentrations of drug and peak areas was confirmed in the range of 100–2000 ng/mL. Detection and quantification limits were 24.85 and 85.36 ng/mL, respectively. The average recovery for bupivacaine ranged from 96.48% to 98.81%. The present methodology was successfully applied, with a high degree of confidence, to analyze clinical samples obtained from patient receiving 0.5% bupivacaine therapy.

A simple, cost-effective and sensitive liquid chromatography-based bio-analytical method has been developed and validated for therapeutic drug monitoring of fluconazole (FLUC) in human serum. Integration of online mixed-mode solid-phase extraction (SPE) into the analytical system was the key for direct injection of untreated serum samples. A short protein-coated (PC) µBondapak CN silica column (PC-µB-CN-column) as a SPE tool and phosphate buffer saline (PBS) (pH 7.4) as an eluent were applied in the extraction step. PC-µB-CN-column operates in two different chromatographic modes. Using PBS, proteins were extracted from serum samples by size-exclusion liquid chromatography, while FLUC trapping was reversed-phase liquid chromatography dependent. FLUC was then eluted from the PC-µB-CN-column onto the quantification position using a mixture of acetonitrile-distilled deionized water (20:80, v/v) as an eluent and ODS analytical column. FLUC was separated at ambient temperature (22±1 °C) and detected at 260 nm. The method was linear over the range of 200-10000 ng/mL. FLUC recovery in untreated serum samples ranged from 97.8 to 98.8% and showed good accuracy and precision. The reliability of the developed method was evaluated by studying the pharmacokinetic profile of FLUC in humans after an oral administration of a single 150 mg tablet.

A rapid, sensitive, selective and simple capillary zone electrophoresis (CZE) method, by integration of field amplified sample stacking (FASS) and in-capillary derivatization (in-CapD) coupled with fluorescence (FL) detection (CZE-FASS-in-CapD-FL), has been developed and validated for simultaneous determination of morphine and its metabolite, morphine-6-glucuronide (morphine-6-G)in human urine. The method was based on in-line derivatization by introducing the sample to running background electrolytes (BGE) of disodium tetraborate decahydrate and potassium ferricyanide, whereas analytes were oxidized into highly fluorescent dimer products. Various parameters influencing the sensitivity and efficiency of the proposed method were investigated, and the optimal conditions of the BGE were as follow: 60 mM disodium tetraborate decahydrate (pH 10.5), 0.25 mM potassium ferricyanide and separation voltage of 9 kV. For FASS, morphine and morphine-6-G were electrokinetically injected for 14 s at 16 kV into the capillary that was pre-injected with water plug for 4 s. The fluorescence signals were then detected at excitation and emission wavelengths of 340 and 450 nm, respectively. Analysis was performed at ambient temperature (22±1 °C). Validation of the method showed good linearity over morphine and morphine-6-G concentrations ranging from 2 to 2000 ng/mL and 2.5 to 2000 ng/mL, respectively. The mean recoveries were ranged from 97.72 to 87.26% and 97.14 to 85.43% for morphine and morphine-6-G, respectively. The validated CZE-FASS-in-CapD-FL method was effectively applied as quantitative forensic analysis of morphine and morphine-6-G in clinical urine samples.

Objective Our aim was to investigate association between OSA and radiotherapy in head and neck cancer patients. Methods On 9th of September 2018, we have searched 12 electronic databases to retrieve relevant studies. All eligible studies that assessed association between OSA and radiotherapy in head and neck cancer patients were included in our meta-analysis. Quality assessment of included studies was done using the NIH tools for cohort, cross-sectional and case series studies. Results Fourteen studies met our study selection criteria, and six studies were eligible for our meta-analysis. There was no significant association between occurrence of OSA and radiotherapy in head and neck cancer patients (Odds ratio 1.54, 95% CI [0.66–3.60]; P = 0.322). Conclusion These findings point to no significant association between OSA risk and radiotherapy in head and neck cancer patients. We suggest more studies to be conducted to investigate any confounders that may influence the effect of radiotherapy on development of OSA in head and neck cancer patients.

A rapid and sensitive method based on direct infusion-nano-electrospray ionization mass spectrometry (DI-nESI-MS) has been developed for the detection and quantification of ciprofloxacin and its metabolites in human saliva. Saliva samples were collected after the oral administration of 500 mg ciprofloxacin tablets. Internal standard (IS), tamoxifen, was added to the collected samples, and then diluted with the ionization solvent, centrifuged and filtered. An aliquot of 4 μL of the filtrate was loaded into a nanospray (NS) capillary. The NS capillary was then fitted into an off-line ion source and the instrument was operated to acquire a two-minute run by applying a voltage of 1000 V (positive-ion detection mode). Quantification of ciprofloxacin relied on the ratio of its peak intensity to the IS peak intensity. The DI-nESI-MS method was validated and provided satisfactory precision with relative standard deviation ranging from 0.39 to 7.48 % and accuracy with relative error ranging from -2.12 to 9.72 %. The calibration curve showed good linearity (r2) > 0.999 over the concentration range of 10-4000 ng/mL. These results verify the effectiveness of the DI-nESI-MS method for monitoring of ciprofloxacin and its metabolites in human saliva samples.

Cellular heterogeneity is a phenomenon that is often observed but poorly understood. Single-cell metabolomics can provide insights into the phenotypical variations between individual cells. Recent advances in microfluidics, micromanipulation, image analysis, and automation allowed for high-throughput isolation of single cells in a minimally disruptive manner as to not affect the cell metabolism. Coupled with new innovations in mass spectrometry-based analytical techniques, single cell metabolomics stands at the cusp of becoming an established field. In this review, some of the recent single cell isolation platforms that are especially suited for metabolomics will be highlighted, as well as the recent trends in mass spectrometry-based single cell platforms. Additionally, some of the limitations of single-cell metabolomics and its recent applications will be briefly discussed. (c) 2019 Elsevier B.V. All rights reserved.

A rapid, selective and sensitive direct infusion nano-electrospray ionization multi-stage mass spectrometry (DI-nano-ESI-MS3) method has been developed and validated for ciprofloxacin identification and quantification. An aliquot of 4 µl containing ciprofloxacin sample solution along with an internal standard (IS), in this case tamoxifen, was loaded into a nanospray (NS) capillary. The NS capillary was then fitted off-line into the ion source where the distance between NS capillary tip and MS aperture was set to 5 mm. The instrument was operated to acquire a two-minute run by applying a voltage of 1000 V (positive-ion detection mode). Ciprofloxacin quantification relied on the ratio of its parent peak (m/z 332) to the IS peak (m/z 372), while identification relied on MS3 of the parent peak and its fragments with m/z values of 314, 288, 268 and 245, respectively. Due to the observed ion suppression effect exerted by the IS over the analyte ion signal at lower concentration levels (

Rapid and simple micellar electrokinetic chromatography (MEKC) with in-capillary derivatization and fluorescence detection has been developed to determine morphine in human serum. The sample was introduced into a background electrolyte (BGE) containing potassium ferricyanide, whereas morphine was oxidized into highly fluorescent product, pseudomorphine. Different parameters for derivatization and subsequent separation were systematically investigated for the analysis of morphine in serum. Efficient performance of the developed MEKC system was carried out in a single run using BGE made up of 70 mM sodium tetraborate decahydrate (pH 10.5), 0.30 mM potassium ferrricyanide, 80 mM sodium dodecyl sulfate, and applied voltage of 9 kV. The combination of MEKC with in-capillary derivatization of morphine was successfully achieved with a high degree of sensitivity. The validation of the method showed good linearity between areas of morphine and the corresponding concentrations over the range of 5-5000 ng/mL. Excellent accuracy and precision were obtained at all concentration levels. The mean recoveries of morphine were ranging from 83.86 to 94.45%. The validated MEKC method successfully permitted determination of morphine in clinical samples after a single oral dose of controlled release morphine sulfate tablets.

A simple, rapid and environment-friendly direct injection HPLC method for the determination of methyldopa (MTD) in human serum has been developed and validated. The method was based on cleanup and separation of MTD from serum by mixed-mode liquid chromatography using a single protein-coated TSK gel ODS-80 TM analytical column (50 × 4.0 mm i.d., 5 µm). The protein-coated column exhibited excellent resolution, selectivity and functioned in two chromatographic modes: size-exclusion chromatography [i.e., solid-phase extraction (SPE) for serum proteins] and reversed-phase chromatography for the final separation of MTD. SPE and HPLC separation were carried out simultaneously with a green mobile phase consisting of acetate buffer (0.1 M, pH 2.4) at a flow rate of 1 mL/min and at room temperature (23 ± 1°C). The eluent was monitored at emission and excitation wavelengths of 320 and 270 nm, respectively. A calibration curve was linear over the range of 0.1-30 µg/mL with a detection limit of 0.027 µg/mL. This online SPE method was successfully applied to real samples obtained from patients receiving MTD therapy.

The UV spectrophotometric analysis of a binary mixture containing bisoprolol fumarate BS and hydrochlorothiazide HZ by using multivariate calibration methods such as principal component regression PCR and partial least squares regression PLS and a graphical spectrophotometric method such as second derivative of the ratio spectra DD was described A calibration set of reference samples was used to develop the models for PCR and PLS The calibration models optimization was achieved through the proper wavelength ranges selection and excluding any information about the interfering excipients In addition a High Performance Liquid Chromatography HPLC was developed to analyze the same mixture The chromatographic separation was achieved on a reversed phase RP column with mobile phase consisting of acetonitrile M KH PO v v and pH Quantitation was achieved with UV detection at nm based on peak area The proposed methods were validated and successfully used for the analysis of laboratory prepared mixtures and pharmaceutical formulations

The dynamics of a cell is always changing. Cells move, divide, communicate, adapt, and are always reacting to their surroundings non-synchronously. Currently, single-cell metabolomics has become the leading field in understanding the phenotypical variations between them, but sample volumes, low analyte concentrations, and validating gentle sample techniques have proven great barriers toward achieving accurate and complete metabolomics profiling. Certainly, advanced technologies such as nanodevices and microfluidic arrays are making great progress, and analytical techniques, such as matrix-assisted laser desorption ionization (MALDI), are gaining popularity with high-throughput methodology. Nevertheless, live single-cell mass spectrometry (LCSMS) values the sample quality and precision, turning once theoretical speculation into present-day applications in a variety of fields, including those of medicine, pharmaceutical, and agricultural industries. While there is still room for much improvement, it is clear that the metabolomics field is progressing toward analysis and discoveries at the single-cell level.

The dynamics of a cell is always changing. Cells move, divide, communicate, adapt, and are always reacting to their surroundings non-synchronously. Currently, single-cell metabolomics has become the leading field in understanding the phenotypical variations between them, but sample volumes, low analyte concentrations, and validating gentle sample techniques have proven great barriers toward achieving accurate and complete metabolomics profiling. Certainly, advanced technologies such as nanodevices and microfluidic arrays are making great progress, and analytical techniques, such as matrix-assisted laser desorption ionization (MALDI), are gaining popularity with high-throughput methodology. Nevertheless, live single-cell mass spectrometry (LCSMS) values the sample quality and precision, turning once theoretical speculation into present-day applications in a variety of fields, including those of medicine, pharmaceutical, and agricultural industries. While there is still room for much improvement, it is clear that the metabolomics field is progressing toward analysis and discoveries at the single-cell level.

A new rapid time-overlapping high-performance liquid chromatography method using coupled-column double-injection technique with fluorescence detection has been developed and validated to determine methyldopa (MTD) in human urine. The method was based on injecting a new sample onto the second column before finalizing the cleanup and the re-equilibration of the first column for the former sample. A combination of isocratic and gradient elution was employed according to a pre-set program. At the beginning, isocratic step of acetate buffer solution (0.1 M, pH 2.4) was set until 7 min. Subsequently, a gradient elution step using acetate buffer (0.1 M, pH 2.4) as mobile phase A and acetonitrile as mobile phase B was employed. After the end of each gradient step, the column was re-equilibrated with 4 mL of the starting isocratic elution system before the next analysis. The overall cycle time was 7 min per each sample. The calibration curve was linear over the concentration range of 0.1–40 µg/mL MTD. The overall ...

A rapid, sensitive and direct nano-electrospray ionization-tandem mass spectrometry (NS-ESI-MS/MS) method, using an offline nanospray (NS) capillary, has been developed and validated for the analysis of metronidazole (MTZ). A mixture of 2 µl MTZ sample solution prepared in an ionization solvent consisting of methanol : water : formic acid in a ratio of 80 : 20 : 0.3, together with 2 µl of an internal standard (IS), 1,3,6-polytyrosine, is loaded into the back of the NS capillary. The NS capillary was fitted into the ion source at a distance of 3 mm between the NS tip and MS orifice. The sample is then analysed and acquired a sustainable signal that allowed for data compilation across various data points for MTZ identification and quantification. The quantification relied on the ratio of the [M + H] + peaks of MTZ and IS with m/z values of 172.0717 and 182.0812, respectively, while the identification relied on the MS/MS of the precursor ions [M + H] + of both compounds and their fragments at 128.05 for MTZ and 165.1 and 136.07 for the IS. The NS-ESI-MS/MS method was accurate and precise for the quantification of MTZ over the concentration range from 2.5 to 25 000 ng ml −1 . The applicability of the method was confirmed by MTZ analysis in its pharmaceutical dosage form and detection of the analyte in clinical human urine samples without any sample treatment procedure.

e17576 Background: With the increase in survival of cancer patients, consequently, increasing their quality of life is mandatory as well. Sleep disturbances, particularly Obstructive Sleep Apnea (OSA), is one of the main complaints of cancer patients in which patients face frequent episodes of upper airway closure during sleep. Possible causes for OSA include either the specific cancer or its treatment whether sedatives, narcotics, radiotherapy, or chemotherapy, but the primary cause is still hard to prove. Our aim was to investigate the association between the occurrence of OSA and radiotherapy in cancer patients. Methods: On the 9th of September, 2018, we have searched comprehensively 12 electronic databases to retrieve relevant studies. All eligible studies that assess the association between OSA and radiotherapy in cancer patients were included in our meta-analysis. Quality assessment of included studies was done using the NIH tool for cohort and cross-sectional studies. Results: Fourteen studies met our selection criteria, eight studies were eligible for our meta-analysis. There was a positive association between the occurrence of OSA and radiotherapy in cancer patients (OR 1.16, 95% CI [0.52–2.56]; P = 0.718). OSA was noted in 103 of 181 cancer patients who received radiotherapy, yielding a remarkable overall prevalence of 63% (95% CI [0.36–0.85]; P = 0.343). A positive risk ratio for the development of OSA in cancer patients treated with radiotherapy was detected (RRs 1.27, 95% CI [0.81–2.00]; P = 0.297). The overall mean of apnea hypopnea index (AHI) for patients with OSA in six studies was 22.45. Conclusions: These findings point to a striking association between OSA risk and radiotherapy in cancer patients. Since the early recognition and management of OSA in such patients may play an important role in improving their quality of life, we recommend screening all cancer patients treated with radiation for early signs of OSA to further improve their survival.

A simple, rapid, and sensitive green high-performance liquid chromatographic (HPLC) method with automated precolumn extraction has been developed and evaluated for analysis of paracetamol (PC) in human serum. The method is performed by direct injection of serum samples onto a homemade protein-coated μ-Bondapak CN silica precolumn, where PC is preconcentrated and retained while proteins and very polar components are washed to waste using a phosphate buffer saline, pH 7.4. The trapped drug is then back-flushed from the precolumn by column-switching followed by separation on a Thermo Scientific Hypersil ODS analytical column with an environmentally friendly mobile phase consisting of ethanol and phosphate buffer (0.01 M, pH 3.5) in the ratio of 5:95 (v/v). Detection is performed at 254 nm. The chromatographic procedure yields precise results and is able to run one sample in only 6 min. The calibration curve is linear over the concentration range of 10–10000 ng mL−1 PC. The applicability of the method was suc...

A new simple, sensitive and precise green analytical procedure using an automated packed-reactor derivatization technique coupled with on-line solid-phase enrichment (SPEn) has been developed and evaluated to determine trace levels of methotrexate (MTX). The method was based on injection of MTX into a flowing stream of phosphate buffer (0.04 M, pH 3.4), carried through the packed oxidant reactor of Cerium (IV) trihydroxyhydroperoxide for oxidative cleavage of the drug into highly fluorescent product, 2,4-diaminopteridine-6-carboxylic acid, followed by SPEn on a head of short ODS column (10 mmÃ4.6 mm i.d., 5 μm particle size). The flow rate was 0.25 mL/min and packed reactor temperature was 40 °C. The trapped product was back-flush eluted from the ODS column to the detector by column-switching with an environmentally friendly mobile phase consisting of ethanol and phosphate buffer (0.04 M, pH 3.4) in the ratio of 5:95 (v/v). The eluent was monitored at emission and excitation wavelengths of 460 and 360 nm, respectively. The calibration curve was linear over the concentration range of 1.25â50 ng/mL with a detection limit of 0.08 ng/mL. The method was successfully applied to determine MTX in pharmaceutical formulations with mean percentage recovery ranging from 99.48 to 99.60. Keywords: Methotrexate, Flow injection analysis, Cerium (IV) trihydroxyhydroperoxide, On-line solid-phase enrichment, Fluorescence detection

The locations and volumes of the contents of a single HepG2 cell were visualized under three-dimensional (3D) holographic and tomographic (HT) laser microscopy, colored by refractive index, not staining. After trapping the specific area of a target cell in a nanospray tip, quantification was performed by live single-cell mass spectrometry. Comparison of the HepG2 cells' before and after 3D-HT images allowed the inference of the precise volume and original location of the trapped cell contents. The total amount of a trapped molecule was estimated. The images also revealed morphological changes in the cell structure caused by the manipulation.

A simple, sensitive, and selective online pre-column derivatization high-performance liquid chromatographic method was developed and validated for the first time to determine trace levels of folic acid (FA). An oxidant cerium (IV) trihydroxyhydroperoxide packed reactor was used for pre-column oxidation and was combined by column switching with a C18 analytical column for sample enrichment and separation. The method was based on oxidative cleavage of FA into highly fluorescence products, 2-amino-4-hydroxypteridine-6-carboxaldehyde and the corresponding 2-amino-4-hydroxypteridine-6-carboxylic acid, during the flow of 0.04 M phosphate buffer (pH 3.5) containing the analyte through packed reactor at a flow rate of 0.2 mL/min and 40°C. The fluorescent products were enriched on the head of the analytical column for the final separation. The separation was performed at room temperature using a mobile phase consisting of phosphate buffer (0.04 M, pH 3.5) and acetonitrile (90:10, v/v). The eluents were monitored at emission and excitation wavelengths of 463 and 367 nm, respectively. The method showed excellent recovery, precision and accuracy with detection limits of 0.067 ng/mL from 500 µL of sample FA. The developed method was successfully applied to the determination of FA in pharmaceutical formulations and showed a recovery of 99.31% and a relative standard deviation of 1.72%.

A high-performance liquid chromatographic method was optimized and validated for the determination of desacetyl nitazoxanide (tizoxanide), the main active metabolite of nitazoxanide in human plasma, urine and breast milk. The proposed method used a CN column with mobile phase consisting of acetonitrile-12mM ammonium acetate-diethylamine in the ratio of 30:70:0.1 (v/v/v) and buffered at pH 4.0 with acetic acid, with a flow rate of 1.5 mL/min. Quantitation was achieved with UV detection at 260 nm using nifuroxazide as internal standard. A simplified direct injection of urine samples without extraction in addition to the urinary excretion pattern were calculated using the proposed method. Also, the effectiveness of protein precipitation and a clean-up procedure were investigated for biological plasma and human breast milk samples. The validation study of the proposed method was successfully carried out in an assay range between 0.2 and 20 µg/mL.

A simple and reliable precolumn derivatization liquid chromatography method with ultraviolet detection has been developed and validated for the analysis of glucosamine (GS) in various dietary supplement formulations and raw materials. Additionally, the proposed method was used for analysis of carisoprodol (CR) found in ternary mixture with paracetamol (PR) and caffeine (CF). The linearity ranges were 1-100 μg/mL for GS, 1-150 μg/mL for CR, PR and CF. Derivatization was used with 1,2-naphthoquinone-4-sulphonic acid sodium salt in the presence of borate buffer. Chromatographic separation of GS-naphthoquinone derivative was achieved by using a mixture of acetonitrile and water (pH 7.3 adjusted with 0.1 M NaOH) in the ratio 10:90, v/v and flow-rate of 1.0 mL/min. UV detection was carried out at 280 nm. For PR, CF, and CR-naphthoquinone derivative, the chromatographic separation was achieved by using mixture of acetonitrile and 20 mM KH(2)PO(4) (pH 3.0 adjusted with phosphoric acid) in the ratio 20:80, v/v and flow-rate of 1.0 mL/min. UV detection was carried out at 275 nm. The limits of detection were 37.2, 35.9, 30.4 and 40.0 ng/mL for GS, CR, PR and CF, respectively.

A sensitive and efficient on-line clean up and pre-concentration method has been developed using column-switching technique and protein-coated µ-Bondapak CN silica pre-column for quantification of ambroxol (AM) in human serum. The method is performed by direct injection of serum sample onto a protein-coated µ-Bondapak CN silica pre-column, where AM is pre-concentrated and retained, while proteins and very polar constituents are washed to waste using a phosphate buffer saline (pH 7.4). The retained analyte on the pre-column is directed onto a C(18) analytical column for separation, with a mobile phase consisting of a mixture of methanol and distilled deionized water (containing 1% triethylamine adjusted to pH 3.5 with ortho-phosphoric acid) in the ratio of 50:50 (v/v). Detection is performed at 254 nm. The calibration curve is linear over the concentration range of 12-120 ng/mL (r(2) = 0.9995). The recovery, selectivity, linearity, precision, and accuracy of the method are convenient for pharmacokinetic studies or routine assays.

A simple, sensitive and precise green high-performance liquid chromatographic method including on-line pre-column oxidation combined by column switching with a short Hypersil ODS analytical column (100 mm × 4.0 mm i.d.) for enrichment and separation was developed and validated to determine low levels of methotrexate (MTX). The method was based on oxidative cleavage of MTX into highly fluorescence products, 2,4-diaminopteridine-6-carboxaldehyde and the corresponding 2,4-diaminopteridine-6-carboxylic acid, during the flow of phosphate buffer (0.04 M, pH 3.4) containing the analyte through the packed reactor of cerium (IV) trihydroxyhydroperoxide (CTH) at a flow-rate of 0.2 mL/min and 40℃. The fluorescent products were enriched on the head of ODS analytical column for the final separation. The separation was performed at room temperature using an environmentally friendly mobile phase consisting of ethanol and phosphate buffer (0.04 M, pH 3.4) in the ratio of 10:90 (v/v). The eluent was monitored at emission and excitation wavelengths of 463 and 367 nm, respectively. The method was successfully applied, without any interference from the excipients, for the determination of drug in tablets and vials with a detection limit of 0.06 ng/mL from 500 ?L of sample MTX.

A direct injection high-performance liquid chromatographic (HPLC) method, with column-switching, for the determination of guaiphenesin (GP) in human serum has been developed. Serum samples were directly injected onto protein-coated RP-8 silica precolumn, where GP was preconcentrated and retained while proteins and very polar components were washed to waste using phosphate buffer saline, pH 7.4. GP was back-flushed from the precolumn by a column-switching technique and separated on a ZORBAX Eclipse XDB-C18 analytical column with a mobile phase consisting of methanol-0.01 M phosphate buffer (containing 1% triethylamine adjusted to pH 3.5 with ortho-phosphoric acid) in the ratio of 45:55 (v/v). The analyte was detected by its UV absorbance at 254 nm. The calibration curve was linear over the concentration range of 25–4000 ng/mL ( r 2 = 0.9994). The method was validated for linearity, accuracy, precision, selectivity, and robustness.

This paper describes validated high-performance thin-layer chromatography and high-performance liquid chromatography methods for the simultaneous determination of pipazethate hydrochloride (PZ) and its degradant. The HPTLC separation was carried out on Merck HPTLC aluminum sheets of silica gel 60 F254 as stationary phase using chloroform:diethylamine:methanol (9.4:0.1:0.5, v/v/v) as a mobile phase. Quantification was achieved using densitometric measurements at 225 nm. The isocratic reversed phase HPLC separation was performed on 5 µm CN column (Luna, Phenomenex®, USA.). Good resolution between PZ and its degradants was achieved using a mixture of acetonitrile:12 mM ammonium acetate:diethylamine (35:65:0.1, v/v/v, pH 4.0) as a mobile phase. Quantitation was achieved with UV detection at 225 nm based on peak area. Forced degradation studies were performed on bulk sample of PZ using acid (1N hydrochloric acid), alkaline (0.1N sodium hydroxide), oxidation (0.33% hydrogen peroxide), heat (75°C), and photolyti...

Three methods were developed for the determination of two ternary mixtures containing drotaverine hydrochloride (DR) with caffeine and paracetamol (mixture 1) and DR with metronidazole and diloxanide furoate (mixture 2). The first method depends on HPLC separation on an RP C18 column at ambient temperature with the mobile phase methanolwater, pH 3.1 (50 + 50, v/v) and UV detection at 213 nm for mixture 1, and the mobile phase acetonitrile25 mM potassium dihydrogen phosphate, pH 4.6 (55 + 45, v/v) with UV detection at 235 nm for mixture 2. The other two chemometric methods applied were partial least squares (PLS-1) and principal component regression (PCR). These approaches were successfully applied to quantify the five drugs in two ternary mixtures using information included in the UV absorption spectra of appropriate solutions in the wavelength range of 210300 nm with 1 nm intervals. Calibration of PCR and PLS-1 models was evaluated by internal validation (prediction of compounds in its own designed training set of calibration), by cross-validation (obtaining statistical parameters that show the efficiency for a calibration fit model), and by external validation (using laboratory-prepared mixtures and pharmaceutical preparations). The proposed methods were successfully applied for the determination of the two ternary combinations in laboratory-prepared mixtures and commercial tablets; the results of PLS-1 and PCR methods were compared with the HPLC method, and a good agreement was found.

A stability-indicating reversed-phase high-performance liquid chromatography (RP-HPLC) method has been developed which can separate and accurately quantitate paracetamol, dantrolene, cetirizine and pseudoephedrine. The method was successfully validated for the purpose of conducting stability studies of the four analytes in quality control (QC) laboratories. The stability-indicating capability of the method was demonstrated by adequate separation of these four analytes from all the degradant peaks. A gradient mobile phase system consisting of (A) 50 mmol L(-1) sodium dihydrogen phosphate, 5 mmol L(-1) heptane sulfonic acid sodium salt, pH 4.2 and (B) acetonitrile was used with Discovery reversed-phase HS C(18) analytical column (250 mm x 4.6 mm i.d., 5 microm particle size). Quantitation was achieved with UV detection at 214 nm, based on peak area. The proposed method was validated and successfully applied for the analysis of pharmaceutical formulations and laboratory-prepared mixtures containing the two multicomponent combinations.

A simple, rapid, and sensitive isocratic reversed-phase LC method using a monolithic column has been developed and validated for simultaneous analysis of the active components of silymarin [taxifolin, silydianin, silychristin, diastereomers of silybin (silybin A and B), and diastereomers of isosilybin (isosilybin A and B)] and dimethyl-4,4′-dimethoxy-5,6,5′,6′-dimethylene dioxybiphenyl-2,2′-dicarboxylate in a commercial formulation. The mobile phase was a 45:55 (v/v) mixture of methanol and 5 mM NaH2PO4 (adjusted to pH 2.75 with phosphoric acid) at a flow rate of 1.5 mL min−1. UV detection was performed at 288 nm and quantification was based on peak area. The method was validated for linearity, accuracy, precision, selectivity, and robustness.

A high-performance liquid chromatographic (HPLC) method was developed for determination of oxyphenonium bromide (OX) and its degradation product. The method was based on the HPLC separation of OX from its degradation product, using a cyanopropyl column at ambient temperature with mobile phase of acetonitrile25 mM potassium dihydrogen phosphate, pH 3.4 (50 + 50, v/v). UV detection at 222 nm was used for quantitation based on peak area. The method was applied to the determination of OX and its degradation product in tablets. The proposed method was also used to investigate the kinetics of the acidic and alkaline degradation of OX at different temperatures, and the apparent pseudo first-order rate constant, half-life, and activation energy were calculated. The pH-rate profile of the degradation of OX in Britton-Robinson buffer solutions within the pH range 212 was studied.

A very simple liquid chromatographic technique was developed and validated for the simultaneous determination of 2 antihistaminic drugs, loratadine (LT) and terfenadine (TR), and their major active metabolites, desloratadine (DL) and fexofenadine (FX), respectively, in human serum. LT, DL, TR, and FX from directly injected serum samples were enriched on a protein-coated RP8 silica precolumn (10 4.6 mm id) while serum constituents, such as proteins and salts, were eluted to waste. Using an online column-switching system, the drugs and their metabolites were quantitatively transferred and separated on a second analytical column (Shim-pack 5 μm particle size cyanopropyl, 250 × 4.6 mm id) followed by ultraviolet detection at 243 nm for LT and DL and 220 nm for TR and FX. Very good precision, accuracy, and linearity were obtained over the range of 101000 ng/mL for LT and DL, 10500 ng/mL for TR, and 103000 ng/mL for FX in human serum. High extraction recoveries from serum ranging from 96.03 to 98.19, 95.44 to 97.26, 95.61 to 98.17, and 95.60 to 97.89 for LT, DL, TR, and FX, respectively, were obtained.

Three methods are developed for the determination of two multicomponent mixtures containing guaiphenesine (GU) with salbutamol sulfate (SL), methylparaben (MP) and propylparaben (PP) [mixture 1]; and acephylline piperazine (AC) with bromhexine hydrochloride (BX), methylparaben (MP) and propylparaben (PP) [mixture 2]. The resolution of the two multicomponent mixtures has been accomplished by using numerical spectrophotometric methods such as partial least squares (PLS-1) and principal component regression (PCR) applied to UV absorption spectra of the two mixtures. In addition HPLC method was developed using a RP 18 column at ambient temperature with mobile phase consisting of acetonitrile-0.05 M potassium dihydrogen phosphate, pH 4.3 (60:40, v/v), with UV detection at 243 nm for mixture 1, and mobile phase consisting of acetonitrile-0.05 M potassium dihydrogen phosphate, pH 3 (50:50, v/v), with UV detection at 245 nm for mixture 2. The methods were validated in terms of accuracy, specificity, precision and linearity in the range of 20-60 microg ml(-1) for GU, 1-3 microg ml(-1) for SL, 20-80 microg ml(-1) for AC, 0.2-1.8 microgml(-1) for PP and 1-5 microg ml(-1) for BX and MP. The proposed methods were successfully applied for the determination of the two multicomponent combinations in laboratory prepared mixtures and commercial syrups.

Three methods were applied for the analysis of 2 multicomponent mixtures containing dextromethorphan hydrobromide, phenylephrine hydrochloride, chlorpheniramine maleate, methylparaben, and propylparaben, together with either sodium benzoate (Mix 1) or ephedrine hydrochloride and benzoic acid (Mix 2). In the first method, liquid chromatography was used for their simultaneous determination using an ODS column with a mobile phase consisting of acetonitrile–phosphate buffer, pH 2.7 (40 + 60, v/v), containing 5mM heptanesulfonic acid sodium salt and ultraviolet (UV) detection at 214 nm. Also, 2 chemometric methods, principal component regression, and partial least squares were used. For both chemometric calibrations, a concentration set of the mixture consisting of each compound in each mixture was prepared in distilled water. The absorbance data in the UV spectra were measured for the 76 or 71 wavelength points in the spectral region 210–240 or 210–224 nm considering the intervals of Δλ = 0.4 or 0.2 nm for Mix 1 and Mix 2, respectively. The 2 chemometric methods did not require any separation step. These methods were successfully applied for the analysis of the 2 multicomponent combinations in synthetic mixtures and in commercial syrups, and the results were compared with each other.

Several spectrophotometric and HPLC methods are presented for the determination of fenofibrate, vinpocetine and their hydrolysis products. The resolution of either fenofibrate or vinpocetine and their hydrolysis products has been accomplished by using numerical spectrophotometric methods as partial least squares (PLS-1) and principal component regression (PCR) applied to UV spectra; and graphical spectrophotometric methods as first derivative of ratio spectra (1DD) or first (1D) and second (2D) derivative spectrophotometry for vinpocetine and fenofibrate, respectively. In addition HPLC methods were developed using ODS column with mobile phase consisting of acetonitrile–water (80:20, v/v, pH 4) with UV detection at 287 nm for fenofibrate and a mobile phase consisting of acetonitrile–10 mM KH2PO4, containing 0.1% diethylamine (60:40, v/v, pH 4.6) with UV detection at 270 nm for vinpocetine. The proposed methods were successfully applied for the determination of each drug and its hydrolysis product in laboratory-prepared mixture and pharmaceutical preparation. The proposed HPLC and derivative spectrophotometric methods were used to investigate the kinetics of acidic and alkaline hydrolytic processes of each drug. The pH-rate profile of hydrolysis of each drug in Britton–Robinson buffer solutions was studied.