High-performance Liquid Chromatography Mobile Phase Research Articles

New RP-HPLC method for the simultaneous determination of process yield and percentage of encapsulation of Gallein in albumin nanoparticles

A study was performed for the development and validation of a method of High Performance Liquid Chromatography (HPLC) for the identification and simultaneous quantification of Gallein and Human Serum Albumin (HSA). In addition, this work presents the development and physicochemical characterization of this new pharmaceutical formulation of HSA nanoparticles loaded with Gallein for potential use in the treatment of Alzheimer’s disease.The method was developed with the purpose of determining the performance of the synthesis process of nanoparticles and the efficiency of encapsulation of the drug in the nanosystem. The HPLC mobile phase consisted of ACN:H2O:TEA:H3PO4 (50:49.8:0.1:0.1 v/v/v) pumped at a flow rate of 0.8 mL/min, isocratic mode, and the measurement were carried out at 220 nm. Chromatographic runs were performed on a C18 column (150 × 4.60 mm; 5 μm size particles). The HPLC-method was validated following the International Conference on Harmonisation (ICH) of Technical Requirements for Registration of Pharmaceuticals for Human Use guidelines and was used to simultaneously quantify the two components of the nanoformulation. Thus, the values obtained through the validated method were 43 % for drug encapsulation efficiency (% EE) and the synthesis performance (% yield) was 96 %.Moreover, the nanoformulation was characterized by DLS, the results showed that the average particle size was 217 nm, with a PDI of (0.085 ± 0.005) and a potential Z of −29.7 mV.Therefore, the developed method has proven useful in providing accurate simultaneous measurements of HSA and Gallein from albumin nanoparticles. It is advantageous since it is able to reduce the time and facilitate the determination of Gallein encapsulation efficiency and yield of albumin nanoparticles.

Determination of Long Chain Chlorinated Paraffins in Soils and Sediments by High-Performance Liquid Chromatography (HPLC) High Resolution Mass Spectrometry (HR-MS)

Long-chain chlorinated paraffins (LCCPs) have gained attention due to their bioaccumulation and toxicity. However, their determination is hindered by low vapor pressure and limited elution from gas chromatography columns. In this study, ammonium acetate (CH3COONH4) was employed as the mobile phase additive and directly applied to high-performance liquid chromatography coupled with Orbitrap high resolution mass spectrometry (HPLC-Orbitrap HRMS). Acetate adducts [M + CH3COO]– were selected for quantifying the LCCPs. The mass spectral parameters, such as the radio frequency lens percentage, vaporizer, ion transfer tube temperature, and spray voltage, were optimized. A new analytical strategy for LCCPs was established based on HPLC-Orbitrap HRMS. The accuracy, limits of detection (LOD), and limits of quantification (LOQ) were equal to 94.8% to 109.4%, 7.9 to 16.0 pg/μL, and 26.3 to 53.3 pg/μL for the LCCPs, respectively. The linear range was between 0.04 and 10.0 ng/μL with R2 values of 0.999 for the LCCPs. The relative standard deviations for intra-day and inter-day precision were from 0.5% to 3.3% and from 0.7% to 7.2%, respectively. This method was validated using 20 sediment and soil samples. For the first time, highly chlorinated (Cl>15) and longer carbon chain length (C>36) homologues of LCCPs were observed in soil. The method was suitable for determining LCCPs while avoiding modified instruments and eliminating the incompatibility of CH2Cl2 with the HPLC mobile phase. Further measurements are required of sediment, soil, and air to better characterize LCCPs in the environment.

Penetapan Kadar Kafein Pada Teh Kering Kemasan Produksi Industri Teh di Pekalongan


 
 
 
 Caffeine is one of the main alkaloid compounds in tea. The maximum limit of caffeine compounds in beverage food products based on SNI 01-7152-2006 is 50 mg / serving. Pekalongan has a packaged dry tea industry with a variety of brands, so caffeine content testing is required. This study aims to determine the differences in caffeine content in packaged dry tea produced by the tea industry in Pekalongan which is analyzed and to determine the caffeine content of all brands of tea samples that meet the maximum caffeine content requirements. The method used is the reverse phase High Performance Liquid Chromatography (HPLC) method with octadecyl silica C18 as stationary phase, methanol for HPLC mobile phase with a flow rate of 1 mL / minute and a wavelength of 274 nm. The results showed that there were differences in caffeine content in packaged dry tea produced by the tea industry in Pekalongan. The level of caffeine is 1.753 mg / g (T1), 4,870 mg / g (T2), 5,157 mg / g (T3), 2,394 mg / g (T4), 3,601 mg / g (T5), 3,275 mg / g (T6), 3,900 mg / g (T7), 3,725 mg / g (T8), 7,048 mg / g (T9) and 5,348 mg / g (T10). The ten brands of tea samples in a dose of 5 grams per serving have a caffeine content that meets the maximum limit requirements according to SNI 01-7152-2006, namely 50mg / serving with the highest caffeine content in sample T9. The ten brands of tea samples are safe for consumption
 
 
 
 

English

The purpose of the study is to develop and validate method for assay of Aceclofenac in tablet dosage forms using ultra violet spectrophotometry (UV) and high performance liquid chromatography (HPLC) techniques. A method was developed and validated for analysis of Aceclofenac using UV technique with methanol and phosphate buffer 7.4 as solvent. The HPLC analysis was conducted using two mobile phases, that is, “A” as Acetonitrile: Methanol (80:20 v/v) and “B” as Acetonitrile: methanol: NH3 solution (225:50:1 v/v/v). The method was used for assay determination for tablets dosage forms and results were found to be in compliance with official standards. Validation studies were also carried out for both methods. Linearity, LOD, single point calibration, precision and accuracy and % RSD were calculated. Aceclofenac standard was analysed with UV Spectrophotometer in the concentration ranges of 0.5-50 and 0.4-50 mg/L for each solvent and results showed good linearity with R2 = 0.9998 and 0.9999. The method was also specific that verifies the absence of interference at the max of Aceclofenac. UV analysis was precise with % RSD falling within 2% and LOD as 0.5 and 0.4 mg/L for methanol and PBS 7.4, respectively. The tablets of three brands showed assay percentages within specified limits in methanol (109.33, 103.90 and 105.61%) and PBS 7.4 (108.70, 100.69 and 106.60%). In HPLC analysis, mobile phase ‘B’ showed more sharp peaks with lesser HETP and Tf compared to mobile phase ‘A’. The method was checked for reliability and efficiency for assay and some of the parameters like height efficiency to theoretical plates (HETP), tailing factor, peak heights, peak widths along with validation studies (Linearity range 0.1-50 mg/L, specificity, precision, and limit of detection and single point calibration). The more basic mobile phase B using NH3 solution produced more sharp peaks as compared to less basic mobile phase A. Key words:  Aceclofenac, UV-Visible spectrophotometry, high performance liquid chromatography (HPLC), validation. &nbsp

Identification of Confusable Herbal Medicines by Mapping of Partial Degradation Products from Herbal Medicine Polysaccharides.

Partial degradation products (PDPs) of herbal medicine (HM) polysaccharides with precolumn derivatization using 1-phenyl-3-methy-5-pyrazolone (PMP) were mapped by high performance liquid chromatography (HPLC), and three groups of confusable HMs were differentiated using the PDP fingerprints assisted with cluster analysis (CA). Three variables of HPLC mobile phase, i.e. acetonitrile proportion, buffer concentration and pH value were optimized with PDP of β-cyclodextrin. Radix Glehniae and Radix Adenophorae; Radix Sophorae Tokinensis and Rhizoma Menispermi; Radix Achyranthis Bidentatae and Radix Cyathulae were successfully distinguished by the method, respectively. The results involving mass spectrometry analysis showed that these PDPs primarily included oligosaccharides and a few monosaccharides. The method can be used as an effective approach for the identification and quality control of HMs, and can also facilitate the in-depth study of biological activity and further development of HM polysaccharides to some extent.

Sol-gel niobia sorbent with a positively charged octadecyl ligand providing enhanced enrichment of nucleotides and organophosphorus pesticides in capillary microextraction for online HPLC analysis.

A niobia-based sol-gel organic-inorganic hybrid sorbent carrying a positively charged C18 ligand (Nb2 O5 -C18 (+ve)) was synthesized to achieve enhanced enrichment capability in capillary microextraction of organophosphorus compounds (which include organophosphorus pesticides and nucleotides) before their online analysis by high-performance liquid chromatography. The sorbent was designed to simultaneously provide three different types of molecular level interactions: electrostatic, Lewis acid-base, and van der Waals interactions. To understand relative contributions of various molecular level analyte-sorbent interactions in the extraction process, two other sol-gel niobia sorbents were also created: (a) a purely inorganic sol-gel niobia sorbent (Nb2 O5 ) and (b) an organic-inorganic hybrid sol-gel niobia sorbent carrying an electrically neutral-bonded octadecyl ligand (Nb2 O5 -C18 ). The extraction efficiency of the created sol-gel niobia sorbent (Nb2 O5 -C18 (+ve)) was compared with that of analogously designed and synthesized titania-based sol-gel sorbent (TiO2 -C18 (+ve)), taking into consideration that titania-based sorbents present state-of-the-art extraction media for organophosphorus compounds. In capillary microextraction with high-performance liquid chromatography analysis, Nb2 O5 -C18 (+ve) had shown 40-50% higher specific extraction values (a measure of extraction efficiency) over that of TiO2 -C18 (+ve). Compared to TiO2 -C18 (+ve), Nb2 O5 -C18 (+ve) also provided superior analyte desorption efficiency (96vs. 90%) during the online release of the extracted organophosphorus pesticides from the sorbent coating in the capillary microextraction capillary to the chromatographic column using reversed-phase high-performance liquid chromatography mobile phase.

Optimization of the chromatographic behaviors of quercetin using choline chloride-based deep eutectic solvents as HPLC mobile-phase additives

ABSTRACTNine types of deep eutectic solvents (DESs) were used as mobile-phase additives to improve the chromatographic behaviors of quercetin. Three variables (temperature, molar ratio and concentration) were studied. According to the ion interaction theory and the hydrogen bond, DESs components can work as ions and play an ion-pairing role with quercetin at the same time. Under the optimum condition, the number of theoretical plates was 6690.8 and the tailing factor was 1.71. Compared with acetic acid (HAc), DESs as mobile-phase additives would not damage the High Performance Liquid Chromatography (HPLC) system. The excellent properties of DESs showed their potential as additives for the determination of quercetin.

Speciation of mercury in water and fish samples by HPLC-ICP-MS after magnetic solid phase extraction

In this paper, Fe3O4@SiO2@γ-mercaptopropyltrimethoxysilane (γ-MPTS) magnetic nanoparticles was prepared and a new method of magnetic solid phase extraction (MSPE)-high performance liquid chromatography (HPLC)-inductively coupled plasma mass spectrometry (ICP-MS) was developed for the speciation of mercury including inorganic mercury (Hg2+), methylmercury (MeHg+) and phenylmercury (PhHg+) in environmental water, wastewater, tap water and fish samples. A rapid separation of three target mercury species was achieved in 8min by employing relatively high ratio of methanol in HPLC mobile phase. Various parameters affecting Fe3O4@SiO2@γ-MPTS-based MSPE of target mercury species have been investigated. Under the optimized conditions, the limits of detection for Hg2+, MeHg+ and PhHg+ were in the range of 0.49–0.74ngL−1. The intra- and inter-day relative standard deviations (n=5) were less than 9.0% and 12%, respectively. The developed MSPE-HPLC-ICP-MS method was validated by the speciation of mercury in the Certified Reference Material of DORM-2 dogfish as well as real-world samples including environmental water, wastewater, tap water and fish samples, and it has the advantages of simple operation, rapid separation, high sensitivity, high enrichment factor and is suitable for the analysis of mercury species in samples with complex matrix.

Infant Exposure to Bisphenol A Can Be Quantitatively Assessed by a Simply Improved High-Performance Liquid Chromatography-Tandem Mass-Spectrometry Method.

To quantitatively measure trace levels of bisphenol A (BPA) in infant urine, a simply improved high-performance liquid chromatography (HPLC)-tandem mass-spectrometry method was developed and validated. In the present work, a ZORBAX SB-C18 column (2.1 × 30 mm, 3.5 μm) was used for trapping and isolating BPA from the HPLC mobile phase. The result showed that the trapping column can provide effective separation from the background BPA to the sample BPA. This method has a limit of detection (LOD) of 0.048 μg/L, spiked recoveries 85.4% (0.50 - 10.0 μg/L), and relative standard deviations of 1.8 - 15.9%. By using its low-LOD advantage, we firstly reported that Chinese infants (n = 48 with age <6 months) have been ubiquitously exposed to BPA (detection frequency of 93%) with an median level of 0.13 μg/L (ranging from below LOD to 5.04 μg/L).

Overexpression and optimization of glutamate decarboxylase in Lactobacillus plantarum Taj-Apis362 for high gamma-aminobutyric acid production.

Gamma-aminobutyric acid (GABA) is an important bioactive compound biosynthesized by microorganisms through decarboxylation of glutamate by glutamate decarboxylase (GAD). In this study, a full-length GAD gene was obtained by cloning the template deoxyribonucleic acid to pTZ57R/T vector. The open reading frame of the GAD gene showed the cloned gene was composed of 1410 nucleotides and encoded a 469 amino acids protein. To improve the GABA-production, the GAD gene was cloned into pMG36e-LbGAD, and then expressed in Lactobacillus plantarum Taj-Apis362 cells. The overexpression was confirmed by SDS-PAGE and GAD activity, showing a 53 KDa protein with the enzyme activity increased by sevenfold compared with the original GAD activity. The optimal fermentation conditions for GABA production established using response surface methodology were at glutamic acid concentration of 497.973 mM, temperature 36°C, pH 5.31 and time 60 h. Under the conditions, maximum GABA concentration obtained (11.09 mM) was comparable with the predicted value by the model at 11.23 mM. To our knowledge, this is the first report of successful cloning (clone-back) and overexpression of the LbGAD gene from L. plantarum to L. plantarum cells. The recombinant Lactobacillus could be used as a starter culture for direct incorporation into a food system during fermentation for production of GABA-rich products.

Preparative enantioseparation of (RS)-baclofen: determination of molecular dissymmetry.

The present work reports preparative enantioseparation of (RS)-baclofen using thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC). Diastereomers were synthesized using a new monochloro-s-triazine-based chiral derivatizing reagent (CDR), namely, N-(4-chloro-6-piperidinyl-[1,3,5]-triazine-2-yl)-L-phenylalanine, under microwave irradiation. Acetonitrile-0.1% aq. triflouroacetic acid in gradient elution mode and CH3 OH-CH2 Cl2 (4:5; v/v) were successful as mobile phase in HPLC and TLC, respectively. The two diastereomers were isolated by preparative TLC. Molecular dissymmetry was established by developing the lowest energy optimized structures of the diastereomers based on Density Functional Theory and with the help of (1) H NMR showing anisotropic effect associated with aromatic ring of s-triazine (in the CDR). The configuration of diastereomers was established as [L-Phe-(R)-Bac] and [L-Phe-(S)-Bac], where the first notation refers to the configuration of chiral auxiliary (of the CDR) and the second to that of the analyte Bac. Limits of detection were found to be 0.056 and 0.061 ng mL(-1), respectively, for the two diastereomers. Determination of absolute configuration of the two diastereomers lent support to the elution order and separation mechanism.

Grafting the sol–gel based sorbents by diazonium salts: A novel approach toward unbreakable capillary microextraction

The present work deals with a novel approach for grafting a sol–gel based sorbent, using diazonium salts for preparation of an unbreakable capillary microextraction (CME) device in on-line combination with high performance liquid chromatography (HPLC). The use of diazonium salts modifier allowed all types of metallic and non-metallic substrates to be used without any limitation. Substrates including copper, brass, stainless steel and polytetrafluoroethylene (PTFE) were chosen to be functionalized by chemical or electrochemical reduction of 4-amino phenyl acetic acid. Then, 3-(trimethoxysilyl)propylamine (3TMSPA) was selected as the precursor and the only reagent for preparation of the desired surface chemical bonded sorbent. The presence of chemical bond between substrate, diazonium salts and 3TMSPA is more probably responsible for thermal and solvent stability and long lifetime of the prepared sorbent. Characterization of the aryl group formation on the various substrates along with the prepared sorbents was thoroughly investigated by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and thermogravimetry analysis (TGA). Typically, one of the prepared sorbents, deposited on the inner surface of the copper tube, was selected for assessing the developed method. The CME device was used for on-line extraction of atrazine, ametryn and terbutryn, as model compounds, from the aquatic media. After extraction, the HPLC mobile phase was used for on-line desorption and elution of the extracted analytes from the CME loop, containing the grafted sol–gel based sorbent, through the HPLC column. Figures of merit of the developed method were also obtained in which the linearity for the analytes was in the range of 30–1000μgL−1. The value of LOD (S/N=3) for all analytes was 10μgL−1 and the RSD% values (n=5) were all below 9.4% at the 500μgL−1 level. Applicability of the developed method was examined by analyzing some real water samples in which the relative recovery percentage ranged from 75 to 95%.

Comparison of electrospray ionisation, atmospheric pressure chemical ionisation and atmospheric pressure photoionisation for the identification of metabolites from labile artemisinin‐based anti‐malarial drugs using a QTRAP® mass spectrometer

Artemisinin-based drugs and their metabolites are prone to in-source fragmentation under atmospheric pressure ionisation mass spectrometry (API-MS) conditions. To facilitate correct and efficient identification of all possible drug metabolites using full scan MS analyzer methods, stable [M + NH(4) ](+) ions should be produced in the MS source. Using a high-performance liquid chromatography (HPLC) hybrid triple quadrupole linear ion trap MS system, electrospray ionisation (ESI), atmospheric pressure chemical ionisation (APCI) and atmospheric pressure photoionisation (APPI) methods were developed for the detection of [M + NH(4) ](+) ions of the test compounds dihydroartemisinin, artemisinin, artemether and artesunic acid. The optimised methods employed ammonium formate buffered HPLC mobile phase in combination with moderate source temperatures (100-200 °C) and showed satisfactorily reduced in-source fragmentation. With a full scan MS analyser method for the detection of the in vitro metabolites of the test compounds, the respective performance of the ESI and APCI methods was found to be comparable. ESI generally resulted in less in-source fragmentation. Incorrect assignment of metabolites resulted from strong in-source fragmentation of artemether using the APPI method. The most number of metabolites could be detected using ESI in combination with a selective MS analyser method. ESI and APCI full scan methods proved to be capable of detecting any drug metabolites present in reasonable concentrations, and are useful when employed in addition to selective scan methods that target low level expected metabolites. APPI can be a valuable alternative for detecting expected metabolites due to good signal-to-noise (S/N) ratio.

HPLC/APCI Mass Spectrometry of Saturated and Unsaturated Hydrocarbons by Using Hydrocarbon Solvents as the APCI Reagent and HPLC Mobile Phase

Saturated and unsaturated, linear, branched, and cyclic hydrocarbons, as well as polyaromatic and heteroaromatic hydrocarbons, were successfully ionized by atmospheric pressure chemical ionization (APCI) using small hydrocarbons as reagents in a linear quadrupole ion trap (LQIT) mass spectrometer. Pentane was proved to be the best reagent among the hydrocarbon reagents studied. This ionization method generated different types of abundant ions (i.e., [M + H](+), M(+•), [M - H](+) and [M - 2H](+ •)), with little or no fragmentation. The radical cations can be differentiated from the even-electron ions by using dimethyl disulfide, thus facilitating molecular weight (MW) determination. While some steroids and lignin monomer model compounds, such as androsterone and 4-hydroxy-3-methoxybenzaldehyde, also formed abundant M(+•) and [M + H](+) ions, this was not true for all of them. Analysis of two known mixtures as well as a base oil sample demonstrated that each component of the known mixtures could be observed and that a correct MW distribution was obtained for the base oil. The feasibility of using this ionization method on the chromatographic time scale was demonstrated by using high-performance liquid chromatography (HPLC) with hexane as the mobile phase (and APCI reagent) to separate an artificial mixture prior to mass spectrometric analysis.

Determination of endocrine-disrupting compounds in water by carbon nanotubes solid-phase microextraction fiber coupled online with high performance liquid chromatography

The commercial solid phase microextraction (SPME) fibers are not stable enough in organic solvent and tend to swell and strip off from the silica fiber in the high performance liquid chromatography (HPLC) mobile phase, and therefore the application of SPME coupled online with HPLC is limited. In this study, an SPME fiber coated with single walled carbon nanotubes (SWCNTs), prepared by means of electrophoretic deposition, was coupled on line to HPLC for the determination of four endocrine-disrupting compounds, i.e. bisphenol A (BPA), estrone (E1), 17α-ethynylestradiol (EE2) and octylphenol (OP), in aqueous samples. The results showed that the SWCNTs coating on the prepared fiber did not swell and strip off from the platinum fiber throughout the experiment, thus indicating a high resistance to the HPLC mobile phase, the mixture of water and acetonitrile. The SWCNTs fiber had similar (for OP) or higher (for BPA, EE2 and E1) extraction efficiencies than the commonly used polyacrylate fiber, and had a lifetime of more than 120 operation times. Under the optimized conditions, the linearity of the proposed method was 1.0–30.0μg/L for BPA and OP and 3.0–90.0μg/L for E1 and EE2. The limits of detection (LODs; S/N=3) and limits of quantification (LOQs; S/N=10) of the method were 0.32–0.52μg/L and 1.06–1.72μg/L, respectively. Repeatability for one fiber (n=3) was in the range of 1.3–7.1% and fiber-to-fiber reproducibility (n=3) was in the range of 1.6–8.4%. The proposed method was successfully applied for the analysis of spiked tap water and seawater samples with recoveries from 81.8 to 97.3%.

An unbreakable on-line approach towards sol–gel capillary microextraction

In this work a novel unbreakable sol–gel-based in-tube device for on-line solid phase microextraction (SPME) was developed. The inner surface of a copper tube, intended to be used as a high performance liquid chromatography (HPLC) loop, was electrodeposited by metallic Cu followed by the self assembled monolayers (SAM) of 3-(mercaptopropyl) trimethoxysilane (3MPTMOS). Then, poly (ethyleneglycol) (PEG) was chemically bonded to the –OH sites of the SAM already covering the inner surface of the copper loop using sol–gel technology. The homogeneity and the porous surface structure of the SAM and sol–gel coatings were examined using the scanning electron microscopy (SEM) and adsorption/desorption porosimetry (BET). The prepared loop was used for online in-tube SPME (capillary microextraction) of some selected polycyclic aromatic hydrocarbons (PAHs), as model compounds, from the aquatic media. After extraction, the HPLC mobile phase was used for on-line desorption and elution of the extracted analytes from the loop to the HPLC column. Major parameters affecting the extraction efficiency including the sample flow rate through the copper tube, loading time, desorption time and sample volume were optimized. For investigating the sorbent efficiency, four loops based on the copper tube itself, the copper tube after electrodeposition with Cu and the tubes with the SAMs and SAMs-sol–gel coating were made and compared. The SAMs-sol–gel coated loop clearly shows a prominently lead of at least 20–100 times of higher efficiency. The linearity for the analytes was in the range of 0.01–500 μg L −1. Limit of detection (LOD) was in the range of 0.005–0.5 μg L −1 and the RSD% values ( n = 5) were all below 8.3% at the 5 μg L −1 level. The developed method was successfully applied to real water samples while the relative recovery percentages obtained for the spiked water samples were from 90 to 104%. The prepared loop exhibited long life time due to its remarkable solvent and mechanical stability. Different solvents such as methanol, acetonitrile and acetone were passed through the loop for many days and it was also used for more than 100 extractions/desorption of the selected analytes and no decrease in the peak areas was observed.

Simultaneous determination of five quinoxaline-1,4-dioxides and two major metabolites in surface water by on-line solid phase extraction coupled to high-performance liquid chromatography

Veterinary antibiotics are environmental contaminants of recent concern, so this study was designed to develop an analytical method of simultaneous determination for quinoxaline-1,4-dioxides (QdNOs) and their metabolites in the aqueous environment at trace levels. The new method is based on on-line solid phase extraction (SPE) using cigarette filter (CGFR) as the sorbent coupled to high-performance liquid chromatography (HPLC). Five QdNOs (carbadox, olaquindox, cyadox, mequindox, quinocetone) and two major metabolites (quinoxaline-2-carboxylic acid and methyl-3-quinoxaline-2-carboxylic acid) were detected in the surface water. The cleaned CGFR precolumn selectively retained target analytes when untreated water samples were upload by a flow-inject pump. Then the enriched extracts were subsequently eluted by HPLC mobile phase to the analytical column for chromatographic analysis. The on-line setup was uncomplicated and automated. The on-line SPE conditions were optimized in detail including sample pH, sample loading flow rate, sample volume, eluent, elution time and sorbents. Under the optimal experimental conditions, the enrichment factors were 33.3–630.0 by preconcentrating 25.0 mL of water samples. Limits of detection (S/N = 3) ranged from 1.6 to 24.3 ng L−1. Satisfactory recoveries were obtained and ranged from 87.1 to 107.5% at two spiked levels in real water samples with high precision (RSD, 1.3–3.8%). The on-line SPE-HPLC method is simple, rapid, reliable, sensitive and could be applied for multiresidue determination of the QdNOs and their metabolites in water samples.

Improved selectivity for the analysis of maternal serum and cord serum for polyfluoroalkyl chemicals

Perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid, two of the most widely studied polyfluoroalkyl chemicals (PFCs), can cross the placenta. Therefore, data on the exposure to PFCs of the very young are needed to evaluate the potential health effects associated with such exposure. Human serum, especially serum collected from pregnant women and cord serum, may contain endogenous components that can interfere in the separation by high performance liquid chromatography (HPLC) of PFOS and another PFC of interest, perfluorohexane sulfonic acid (PFHxS), from other serum biomolecules. The presence of such interferences may prevent the adequate quantification of PFOS and PFHxS in cord serum or serum collected from pregnant women, and potentially hinder the assessment of gestational exposure to these important PFCs using biomonitoring. We have modified our on-line solid phase extraction–HPLC–isotope dilution–tandem mass spectrometry analytical method for measuring PFCs in serum and developed an approach that allows for the elimination of these potential interferences without compromising analytical sensitivity and throughput. The combination of acetonitrile as the HPLC mobile phase organic solvent and a Betasil C8 HPLC column provided the best separation of PFOS and PFHxS from interferent peaks. In addition to eliminating these interferences, the acetonitrile method has a shorter runtime and is more sensitive for most PFCs (limits of detection were 0.1 ng/mL except for PFOS (0.2 ng/mL)) than our previous method that used methanol for the HPLC separation. The present method should improve the precise and selective analysis of maternal and cord serum for PFCs.

TLC and HPLC Methods to Follow the Synthesis of Vinorelbine

The thin-layer chromatography (TLC) combined with high-performance liquid chromatography (HPLC) has been proved to be a quick and valid method to detect the intermediates and the end-product created during the chemosynthesis process of vinorelbine (VB). This paper gives a detailed investigation on the results of two determination methods when the condition of the detection changed. It shows that when TLC developer is consisted of petroleum ether, chloroform, acetone, and diethyl amine (23.5:12:2:2.5, v/v/v/v), vinblastine sulfate (VBS), anhydrovinblastine (AHVB), and VB can be separated specifically. When the mobile phase of HPLC is a mixture of methyl alcohol, acetonitrile, diethyl amine, and high purity water (420:252:3:225; v/v/v/v), adjusted with orthophosphoric acid to pH 6.5, the intermediates and the resultants of the chemosynthesis of VB can be determined effectively. It can also be used to fix quantify of the resultants. The calibration curve for VB shows good linearity in the two mass concentration ranges of 0.0100-0.0500 mg/mL (r = 0.9956) and 0.00600-0.0100 mg/mL (r = 0.9978), respectively. The limit of detection of HPLC for VB is 0.200 microg/mL.

Preparation and application of rifamycin-capped (3-(2-O-β-cyclodextrin)-2-hydroxypropoxy)-propylsilyl-appended silica particles as chiral stationary phase for high-performance liquid chromatography

Rifamycin-capped (3-(2-O-β-cyclodextrin)-2-hydroxypropoxy)-propylsilyl-appended silica particles (RCD-HPS), a new type of substituted β-cyclodextrin-bonded chiral stationary phase (CSP) for high-performance liquid chromatography (HPLC), have been synthesized by the treatment of bromoacetate-substituted-(3-(2-O-β-cyclodextrin)-2-hydroxypropoxy)-propylsilyl-appended silica particles (BACD-HPS) with rifamycin SV in anhydrous acetonitrile. The stationary phase is characterized by means of elemental analysis and Fourier-transform infrared spectroscopy. This new CSP has a chiral selector with two recognition sites: rifamycin and β-cyclodextrin (β-CD). The chromatographic behavior of RCD-HPS was studied with several disubstituted benzenes and some chiral drug compounds under reversed-phase HPLC mobile phase conditions. The results show that RCD-HPS has excellent selectivity for the separation of aromatic positional isomers and enantiomers of chiral compounds due to the cooperative functioning of rifamycin and β-CD.