High Pressure Liquid Chromatography Technique Research Articles

Dietary Intake and Circulating Amino Acid Concentrations in Relation with Bone Metabolism Markers in Children Following Vegetarian and Omnivorous Diets.

Scientific studies reported that most vegetarians meet the total protein requirements; however, little is known about their amino acid intakes. We aimed to assess dietary intake and serum amino acid levels in relation to bone metabolism markers in prepubertal children on vegetarian and traditional diets. Data from 51 vegetarian and 25 omnivorous children aged 4-9 years were analyzed. Dietary intake of macro- and micronutrients were assessed using the nutritional program Dieta 5®. Serum amino acid analysis was performed using high-pressure liquid chromatography technique, 25-hydroxyvitamin D and parathormone-electrochemiluminescent immunoassay, and bone metabolism markers, albumin, and prealbumin levels using enzyme-linked immunosorbent assay. Vegetarian children had a significantly lower intake of protein and amino acids with median differences of about 30-50% compared to omnivores. Concentrations of four amino acids (valine, lysine, leucine, isoleucine) in serum varied significantly by diet groups and were lower by 10-15% in vegetarians than meat-eaters. Vegetarian children also had lower (p < 0.001) serum albumin levels compared to omnivores. Among bone markers, they had higher (p < 0.05) levels of C-terminal telopeptide of collagen type I (CTX-I) than omnivores. Correlation patterns between amino acids and bone metabolism markers differed in the vegetarian and omnivore groups. Out of bone markers, especially osteoprotegerin was positively correlated with several amino acids, such as tryptophan, alanine, aspartate, glutamine, and serine, and ornithine in vegetarians. Vegetarian children consumed apparently sufficient but lower protein and amino acids compared to omnivores. In circulation these differences were less marked than in the diet. Significantly lower amino acid intake and serum levels of valine, lysine, leucine, and isoleucine as well as the observed correlations between serum amino acids and biochemical bone marker levels indicated the relations between diet, protein quality, and bone metabolism.

Phenolic profile and pigment stability of Hylocereus species grown in North-East India

The current study was performed to generate a complete polyphenol and pigment profile along with the stability of color pigment extracted from the pulp and peel of two Hylocereus species H. costaricencis (HC) and H. udantus (HU) of dragon fruit. Polyphenol profiles of the pulp of both fruits at four development stages (from seven days after fruit set to fruit maturity) and the peel of mature fruits of both the species were generated using ultra high-pressure liquid chromatography technique (UHPLC). UHPLC chromatograms confirmed the presence of around 15 phenolic compounds among which the ellagic acid was found to be prominent in the pulp of both the species whereas syringic acid (in HU) and ferulic acid (in HC) dominate in the peel. Apart from the polyphenols, the peels of mature fruits of both species were found to contain a comparatively low amount of color pigment betacyanin than the pulp of red-colored matured HC fruit. Further, pigment stability analysis under various physiochemical conditions revealed the stability of color pigment in acidic pH, sugar solutions, antioxidant solutions and low temperatures.

Determination of Pesticide Residues in Sediments of River Ravi

Sediments are socioeconomic, geomorphologic, and an important environmental resource. The purpose of this study was to determine the pesticide residues in the sediments of River Ravi. For analysis 12 sediment samples were collected along with River Ravi, reaching from Ravi Siphon to BS (Balloki Suleiman) link. River Ravi is enlisted as one of the most polluted rivers of Pakistan followed by extreme flow variations, i.e. 10 – 10,000 m3/s. The concentration of pesticide residues in samples was detected by the High-pressure liquid chromatography (HPLC) technique. Noticeable concentrations of pesticides were detected in the majority of the samples which depicted high toxicity levels of pesticides in the sediments of River Ravi. High amounts of pesticides were observed in the right and left banks of Saggian (S4) i.e. 11.37 mg/kg and Khudpur (S6, S7) i.e. 12.116 mg/kg. A significant amount of Imidacloprid and Bifenthrin was detected in the majority of the sediment samples, i.e. 22.78 mg/kg and 15.82 mg/kg. Furthermore the detected concentration of pesticides in the right and left bank of Balloki head works (S10, S11) and Ravi Bridge (S3) was relatively less as compared to other sampling sites. All these sampling points receive irrigational runoff from nearby agricultural lands and urban wastewater, resulting in the accumulation of pesticides in the sediments. The following trend of pesticide contamination was observed in the sediment samples of River Ravi, Bifenthrin &gt; Imidacloprid &gt; Dimethomorph &gt; Glyphosate.

Simultaneous Estimation of Telmisartan, Chlorthalidone, Amlodipine Besylate and Atorvastatin by RP-HPLC Method for Synchronous Assay of Multiple FDC Products Using Analytical FMCEA-Based AQbD Approach.

Numerous reversed-phase high-pressure liquid chromatography (RP-HPLC) and high-performance thin-layer chromatography (HPTLC) techniques have been published for the estimation of fixed-dose combinations (FDCs) of telmisartan (TEL). No published literature has been reported to date which described the synchronous estimation of FDCs of TEL using a single chromatography condition. Hence, the RP-HPLC method has been developed and validated for synchronous analysis of FDCs of TEL using an enhanced analytical quality by design (AQbD) approach to save time, cost and solvent for analysis. The implementation of AQbD was initiated with the identification of failure modes (FMs) using the Ishikawa diagram, and their critical effect analysis was carried out by risk priority number ranking and filtering method. The identified critical FMs were optimized by design of experiments-based response surface modeling using the Box-Behnken design. The method operable design region was navigated and control strategy was framed to mitigate the risk of critical FM. The RP-HPLC method was developed using Shim-Pack octadecyl silane C18 column and acetonitrile: 1.0%v/v triethylamine (pH6.5 adjusted using perchloric acid; 42:58, %v/v). The developed method was found to be validated as per the International Council For Harmonization Q2 (R1) guideline. The method was applied for the synchronous assay of seven different FDCs of TEL and assay results were found in good compliance with the respective labeled claim.

The Contribution of High Performance Liquid Chromatography to the Incidental Discovery of Hemoglobin Variants during Glycated Hemoglobin Assay

HbA1c is assayed in the biochemistry laboratory using a high pressure liquid chromatography (HPLC) technique in ion exchange, and given the correlation between its value and the risk of complication, it is crucial to know it, advantages and it limits. This work highlights the contribution of HPLC in the detection of qualitative abnormalities of hemoglobin during the determination of HbA1c using the ADAMS HA-8180V ARKRAY® device. This descriptive prospective study, carried out at the Biochemistry-Toxicology department of the Mohammed V Military Hospital in Rabat, focused on all samples for which routine HbA1c testing is prescribed during the past year, external samples and from all departments. For each abnormality noted on the chromatogram, a complete study of hemoglobin was performed using other electrophoretic technique at alkaline and acid pH on the Capillarys 2 Flex Piercing® Sebia® and the Hydrasys 2 Scan Focusing® Sebia®. Almost 0.6% of the variants were detected during the HbA1c assay out of 12,944 blood samples.Only 0.04% were not identified by the machine. After confirmation, variant C was predominantly present (n = 30), followed by S (n = 28) then O-Arab (n = 8) and l 'Hb D (n =2). The HPLC technique, for measurement of HbA1c, represents a reliable screening tool for the most common variants of Hb, with however limitations that encourage vigilance in the analysis and interpretation of the results.

Evaluation of the role of Shodhana (Purification) process in Croton tiglium seeds for reduction of toxic content

In Ayurvedic texts, Jayapala or croton tiglium seeds are well known as khumbini for its toxicity (severe purgative action) and are used for the treatment of constipation after shodhana (detoxification) of the seed with godugdha (cow milk). The oil content of the seeds was responsible for the purgative property, and its reduction enhances its medicinal usage. The presence of Crotonoside or iso-guanosine in seed extract was identified in HPTLC and quantified using high pressure liquid chromatography technique both before and after the purification process of the seed. The phytochemicals and physicochemical parameters of seeds were analyzed to find the level of changes in the processed seeds. The other chemical constituents of the seed extracts are studied using different techniques like HPTLC, HPLC, LC-MS, and GC-MS. The study has revealed that the detoxification process, as per classical texts, has shown an effective depletion in the quantity of crotonoside in processed seeds.

Optimization of Mild Extraction Methods for the Efficient Recovery of Astaxanthin, a Strong Food Antioxidant Carotenoid from Microalgae

Microalgae represent an important source of bioactive compounds for food applications. In this study, multifunctional extracts from Haematococcus pluvialis (H. Pluvialis) microalga have been developed in order to be used as food additives. Total extracts were recovered by ultrasound assisted extraction using eco-friendly and food grade solvents. Five different ratios ranging from 1/100 to 1/5 g biomass/ mL solvent were studied in different ultrasound intensities in order to optimise the extraction of carotenoids, especially of astaxanthin. The produced extracts were analysed using High Pressure Liquid Chromatography (HPLC-DAD) and UV-Vis spectroscopy techniques. Acetone was the most efficient solvent for the extraction of carotenoids in all tested ratios. However, D-limonene and medium chain triglycerides extracts also gave a satisfying recovery of carotenoids. D-limonene was the preferred solvent since extracts with high amounts of carotenoids were recovered, permitting their direct use in food products and avoiding further condensation steps.

Unexpected Detection of Abnormal Hemoglobin Variants During Routine HbA1c Analysis by HPLC Technique: Challenges and Opportunities in HbA1c Testing

Background: Glycated Hemoglobin A1c (HbA1c) assay is most widely used in diabetic patients for assessing long-term control of glycemia. The presence of hemoglobin variants may be an incidental finding and can interfere with HbA1c measurements. The aim of the present study is to investigate the prevalence and impact of interference of different abnormal hemoglobin variants on HbA1c measurements during routine HbA1c testing. Methods: A total of 12,092 HbA1c samples were collected from January to August 2018. HbA1c quantification was carried out on a Variant II Bio-Rad’s HPLC analyzer. Abnormal chromatograms were further analyzed using the extended-run high-pressure liquid chromatography (HPLC) analysis in the A2/F mode. Results: The samples were examined for presence of abnormal variants. Samples producing abnormal chromatograms were further analyzed in A2/F mode to characterize hemoglobin variants. Abnormal variants were identified in 126 (1%) samples, and 74 (0.59%) sickle cell traits (SCT) were the most common variant in our findings. Moreover, 30 (0.24%) cases were eluted in the variant window in A1c mode, which on further analysis were found to be Hb E &amp; Hb D traits. Furthermore, 3 (0.02%) cases were eluted at a RT &lt;1 min as (unknown) and identified as Hb H. Also,19 (0.15%) samples were eluted in the P3 window at different retention times. Conclusion: Observing each chromatograph after the analysis can help us in identifying silent hemoglobin variants in routine HbA1c testing. Knowledge and awareness of common hemoglobin variants affecting measurement of HbA1c is imperative to avoid reporting of falsely low HbA1c values in diabetic population.

Dietary Geranylgeranyl Pyrophosphate Counteracts the Benefits of Statin Therapy in Experimental Pulmonary Hypertension.

The mevalonate pathway generates endogenous cholesterol and intermediates including geranylgeranyl pyrophosphate (GGPP). By reducing GGPP production, statins exert pleiotropic or cholesterol-independent effects. The potential regulation of GGPP homeostasis through dietary intake and the interaction with concomitant statin therapy is unknown. We developed a sensitive high-pressure liquid chromatography technique to quantify dietary GGPP and conducted proteomics, qualitative real-time polymerase chain reaction screening, and Western blot to determine signaling cascades, gene expression, protein-protein interaction, and protein membrane trafficking in wild-type and transgenic rats. GGPP contents were highly variable depending on food source that differentially regulated blood GGPP levels in rats. Diets containing intermediate and high GGPP reduced or abolished the effects of statins in rats with hypoxia- and monocrotaline-induced pulmonary hypertension: this was rescuable by methyl-allylthiosulfinate and methyl-allylthiosulfinate-rich garlic extracts. In human pulmonary artery smooth muscle cells treated with statins, hypoxia activated RhoA in an extracellular GGPP-dependent manner. Hypoxia-induced ROCK2 (Rho associated coiled-coil containing protein kinase 2)/Rab10 (Ras-related protein rab-10) signaling was prevented by statin and recovered by exogenous GGPP. The hypoxia-activated RhoA/ROCK2 pathway in rat and human pulmonary artery smooth muscle cells upregulated the expression of Ca2+-sensing receptor (CaSR) and HIMF (hypoxia-induced mitogenic factor), a mechanism attenuated by statin treatment and regained with exogenous GGPP. Rab10 knockdown almost abrogated hypoxia-promoted CaSR membrane trafficking, a process diminished by statin and resumed by exogenous GGPP. Hypoxia-induced pulmonary hypertension was reduced in rats with CaSR mutated at the binding motif of HIMF and the interaction between dietary GGPP and statin efficiency was abolished. In humans fed a high GGPP diet, blood GGPP levels were increased. This abolished statin-lowering effects on plasma GGPP, and also on hypoxia-enhanced RhoA activity of blood monocytes that was rescued by garlic extracts. There is important dietary regulation of GGPP levels that interferes with the effects of statin therapy in experimental pulmonary hypertension. These observations rely on a key and central role of RhoA-ROCK2 cascade activation and Rab10-faciliated CaSR membrane trafficking with subsequent overexpression and binding of HIMF to CaSR. These findings warrant clinical investigation for the treatment of pulmonary hypertension and perhaps other diseases by combining statin with garlic-derived methyl-allylthiosulfinate or garlic extracts and thus circumventing dietary GGPP variations.

Collagen isolation and characterization from Sardinella longiceps.

Objective:Collagen is a fibrous protein that is primarily used in the pharmaceutical and biomedical industries. This study isolates and characterizes type-1 collagen from Sardine longiceps (scales, skin, and muscle).Materials and Methods:Collagen was isolated from S. longiceps using two methods: acid-solubilized collagen and pepsin-solubilized collagen. Sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE) was used to estimate the molecular weight of isolated collagen. Ultraviolet (UV)-visible spectrophotometry analysis was used to confirm the collagen extracted (type-I collagen). The functional groups of isolated collagens were identified using fourier transform infrared (FTIR) analysis. The X-ray diffraction (XRD) technique was used to investigate the crystallinity of isolated collagen. The high-pressure liquid chromatography (HPLC) technique was used to study the amino acid composition.Results:SDS–PAGE of S. longiceps revealed molecular weights ranging from 116 kDa for α-2 to 97 kDa for α-1. UV-visible spectra showed an absorbance value below 300 nm, and the results confirmed type-I collagen. FTIR showed major functional groups like amide A, B, I, II, and III. XRD determined the crystallinity of isolated collagen. The HPLC results showed the presence of higher glycine content, followed by proline and hydroxyl proline in the extracted collagen.Conclusion:The overall study confirmed that fish waste materials (scales, skin, and muscles) could be used as an alternative source for collagen.

Advanced chromatographic technique for performance simulation of anti-Alzheimer agent: an ensemble machine learning approach

This work employs the application of three artificial intelligence (AI) techniques namely; support vector machine (SVM), Hammerstein-Wiener (HW) and multi-layer perceptron (MLP) for predicting the qualitative properties of an anti-Alzheimer agent using high-pressure liquid chromatography technique. The mobile phase (inform of acetonitrile and trifluoroacetic acid) and the column temperature was used as the predictors in modelling the maximum retention time (tR-max) and resolution (Resol.) as the output variables of the analyte. The measured and predicted values were checked using three performance indices including; Nash–Sutcliffe efficiency (NSE), correlation coefficient (CC) as the goodness of fits and a statistical error inform of root-mean-square error (RMSE). The results obtained demonstrated the promising ability of AI-based models in modelling the qualitative properties of the anti-Alzheimer agent. Observation of different outputs of the AI-based models at various time intervals showed the necessity of ensembling the outputs of the AI-based models. Therefore, simple average ensemble and support vector machine ensemble (SVM-E) were employed to enhance the performance skills of the simple models. The comparative performance of SVM-E inform of NSE indicated its ability in boosting and enhancing the performance skills of the single models SVM, MLP and HW models up to 5, 13 and 20% respectively in the testing stage for modelling tR-max.

Radiolabeling of lacosamide using highly purified rhenium-188 as a prospective brain theranostic agent

Rhenium-188 is prospectively effective for both diagnosis and radiotherapy as it appropriately emits gamma rays and beta particles. Lacosamide (LCM) is a newly approved antiepileptic medication for focal drug-resistant epilepsy. Rhenium-188 was separated with high elution yield and high purity using the new 188W/188Re generator based on the ZrSiW gel matrix. 188Re-LCM was prepared with high radiochemical yield and high purity. Biodistribution of 188Re-LCM in normal Swiss albino mice was investigated to determine its utility as a potential brain therapy agent. The 188W/188Re generator was used to obtain 188Re based on the ZrSi188W gel matrix, and the chemical, radiochemical, and radionuclidic purity of the obtained 188Re was determined using inductively coupled plasma optical emission spectrometry (ICP-AES), a paper chromatography technique, and high-purity germanium (HPGe) detection, respectively, to assess its validity for LCM labeling. Various factors, such as the pH, reaction time, and LCM quantity, were therefore studied in order to improve the yield and purity of 188Re-LCM, as determined by various chromatographic techniques such as electrophoresis, thin layer chromatography (TLC), and high-pressure liquid chromatography (HPLC). 188Re was obtained with a high elution yield (75 ± 3%) and a low 188W breakthrough (0.001 ± 0.0001%). The maximum radiochemical yield of 188Re-LCM (87.5 ± 1.8%) was obtained using 50 μl LCM (4 mM), 250 μl stannous chloride (4.4 mM) at pH 4, 100 μl 188Re (37 MBq), within 30 min, at room temperature (25 ± 3 °C), as determined by TLC, electrophoresis, and HPLC techniques. Biodistribution analysis showed that 188Re-LCM was primarily localized in the brain (5.1%) with a long residence time (240 min).

Validation of HPLC and Enzyme-Linked Immunosorbent Assay (ELISA) Techniques for Detection and Quantification of Aflatoxins in Different Food Samples.

Background: In Jordan as in other worldwide countries, mycotoxins are considered a serious national problem in food supplies. As a result, almost all nations are setting and adopting different regulations targeting the control of mycotoxins levels in the domestic food supply, including the problem of reliable sampling and analysis methods. Objective: It is necessary to improve and give evidence of analytical abilities of laboratories within Jordan and developing countries enabling them to monitor mycotoxins effectively in food to overcome non-tariff obstacles. Methods: We analyzed 40 samples from wheat, corn, dried fig and dried coffee beans for total aflatoxin content using High Pressure Liquid Chromatography (HPLC) and Enzyme Linked Immunesorbent Assay (ELISA) methods. Results: 40% of samples from wheat, 60% from corn, 30% from dried fig, and 50% from dried coffee beans were found positive when speaking of total aflatoxins, with average values between 1.14 and 4.12 μg/kg. Obtained results allow considering all tested food samples as fit for human consumption if compared with the labeled regulatory limit of allowed aflatoxins in the European Union. In detail, the limit of detection and the limit of quantification for methods used in this study were significantly lower than the maximum limits established by the European Union. Highlights: The procedure used in this study is suitable for detection of mycotoxins at very low concentration.

Biopharmaceutical potential, chemical profile and in silico study of the seagrass– Syringodium isoetifolium (Asch.) Dandy

Syringodium isoetifolium (Asch.) Dandy (Family: Cymodoceaceae) is a seagrass growing in the oceans across the globe except in cold waters. This study investigated into the polyphenolic content, antioxidant [2,2-diphenyl-1-picrylhydrazyl(DPPH), 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid (ABTS), cupric reducing antioxidant capacity (CUPRAC), ferric reducing antioxidant power (FRAP), metal chelating, phosphomolybdenum)]and enzymatic properties [α-amylase, α-glucosidase, tyrosinase, acetylcholinesterase (AChE), butylcholinesterase (BChE)] of S. isoetifolium. Detailed phytochemical profiling was also conducted using Ultra Performance High-Pressure Liquid Chromatography (UHPLC) technique. The methanolic extract was found to possess greater amount of phenolic than flavonoid compounds. Antioxidant results showed that the extract was a better ABTS radical scavenger (9.56±0.40mg TE/g) compared to DPPH (5.39±0.09mg TE/g and exhibited good reducing potential with CUPRAC assay (18.66±0.46mg TE/g). In terms of enzymatic inhibition, strong activities were noted against tyrosinase (25.92±0.11mg KAE/g) in contrast to α-amylase, α-glucosidase and cholinesterase. Phytochemical data revealed the presence of 14 compounds with chicoric acid and caftaric acid among them. Docking the identified compounds, namely, caftaric acid, loliolide and Iso-loliolide at the active site of the tyrosinase enzyme has elucidated the binding affinity of these inhibitors and their interactions with the active site. Based on our findings, S. isoetifolium may be considered as a good natural antioxidant and clinical enzyme inhibitors that can be exploited in pharmaceutical/or cosmeceutical industries.

Consistency evaluation between matrix components ratio and microbiological potency of tylosin major components.

BackgroundThe aim of our research work was to investigate the relative potencies of matrix components of tylosin, a multi-component antibiotic, and establishing a quantitative relationship between content and potency of each component.MethodsThe potencies of tylosin matrix components were determined by using three bioassay methods. The content of tylosin components (tylosin A, B, C, and D) in different tylosin samples were determined by using high pressure liquid chromatography (HPLC) technique and their theoretical potencies were calculated. Equivalency of theoretical and microbiological potencies for each sample was evaluated using statistical analysis.ResultsThe highest amount of tylosin B content was found in tylosin phosphate and tartrate (up to 19%). Tylosin D content in all tylosin samples varied in the range of 0.03 to 18.73%. Tylosin A, B, and C showed similar sensitivity to the Kocuria rhizophila, the test organism in agar-diffusion method, while the potency of tylosin D was 39% of A. In the turbidimetric methods by Staphylococcus aureus, tylosin D and B responses to A component were ranged from 22.5 to 22.8% and 77.3 to 79.3%, respectively, while potencies of tylosin C and A were almost equal. The biopotency conversion factors were not resulted to a single factor, due to the different antibacterial activity of tylosin components.ConclusionOur findings indicated that defining individual limit for the low active matrix components and for the total of other components with similar high activity could improve the accuracy of potency results. Graphical abstractᅟ

Long term effects of olive mill wastewaters application on soil properties and phenolic compounds migration under arid climate

The principal objective of the present study has been to investigate the long term application effects of olive mill wastewaters (OMWW) on the main properties of a Mediterranean soil under arid climate. In addition the migration dynamic and evolution of phenolic compounds in the different soil layers over time and according to the OMWW amount added have been studied.Results have showed that the irrigation of sandy soils by different doses of OMWW has influenced the soil physicochemical and microbiological characteristics. However, a slight change in the granulometric composition of soil treated with OMWW has been distinguished. The study of the phenolic compounds dynamic has showed the migration of these compounds further than 120 cm soil depth. The comparison of the different spectra obtained by the high pressure liquid chromatography (HPLC) technique has explained that the high molecular weight polyphenols which have been retained in the upper soil layers. However, the low molecular weight phenolic compounds have been detected in depth. All the results obtained have proved that the dose of 50 m3 ha−1 has been the most suitable for the soil studied.

Intrinsic Xenobiotic Metabolizing Enzyme Activities in Early Life Stages of Zebrafish (Danio rerio).

Early life stages of zebrafish (Danio rerio, zf) are gaining attention as an alternative invivo test system for drug discovery, early developmental toxicity screenings and chemical testing in ecotoxicological and toxicological testing strategies. Previous studies have demonstrated transcriptional evidence for xenobiotic metabolizing enzymes (XME) during early zf development. However, elaborate experiments on XME activities during development are incomplete. In this work, the intrinsic activities of representative phase I and II XME were monitored by transformation of putative zf model substrates analyzed using photometry and high pressure liquid chromatography techniques. Six different defined stages of zf development (between 2.5 h postfertilization (hpf) to 120 hpf) were investigated by preparing a subcellular fraction from whole organism homogenates. We demonstrated that zf embryos as early as 2.5 hpf possess intrinsic metabolic activities for esterase, Aldh, Gst, and Cyp1a above the methodological detection limit. The activities of the enzymes Cyp3a and Nat were measurable during later stages in development. Activities represent dynamic patterns during development. The role of XME activities revealed in this work is relevant for the assessing toxicity in this test system and therefore contributes to a valuable characterization of zf embryos as an alternative testing organism in toxicology.

Visible-light photocatalytic degradation of ethidium bromide using carbon- and iron-modified TiO2 photocatalyst

Nanosized TiO2 as well as carbon (C) and C, Fe co-doped TiO2 were synthesized using reverse microemulsion method. Thermal stability of precursor was studied using thermogravimetry and differential thermal analysis techniques. Heat-treated powders were characterized using Fourier transform infrared spectrophotometer, X-ray diffractometer, scanning electron microscope, transmission electron microscope and energy-dispersive X-ray spectroscope. Visible-light photocatalytic degradation of aqueous solution of ethidium bromide (EtBr) was investigated using C, Fe co-doped TiO2 photocatalyst. UV–visible spectrophotometer and high-pressure liquid chromatography techniques were used to analyze the concentration of EtBr during the degradation process. Various parameters affecting the photocatalytic activity of photocatalyst are studied. C-doped TiO2 acts as photosensitizer and helps to extend the light absorption wavelength of C-doped TiO2.·Fe co-doping introduces new energy levels of the transition metal ions between the band gap of TiO2 and further extends absorption wavelength in visible region. The synergistic effects of C- and Fe-modified TiO2 nanoparticles were responsible for improving visible-light photocatalytic activity.

Nano Sized C-doped TiO2 As A Visible-light Photocatalyst For The Degradation Of 2,4,6- Trichlorophenol

Nanosized bare and carbon (C)-doped TiO2 were prepared using reverse micro-emulsion method. Synthesized powders were characterized with the help of X-ray diffractometer (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), energy dispersive X-ray spectroscope (EDX) and UV-visible spectrophotometer. EDX study reveals that as calcination temperature increases amount of C on TiO2 decreases. SEM and TEM images show that TiO2 particles are spherical in shape and after increasing the calcination temperature size of particle increases. Particle size of TiO2 obtained from TEM data varies between 10 to 17nm. Visible light photocatalytic degradation of 2,4,6-trichlorophenol (TCP) aqueous solution was carried out using nanosized bare as well as C-doped TiO2. UV-visible spectrophotometer and high pressure liquid chromatography (HPLC) techniques were used to analyze the concentration of TCP during the degradation process. In presence of visible light C-doped TiO2 obtained after calcination of precursor at 300°C shows better photocatalytic activity. Parameters affecting the photocatalytic process such as calcination temperature, amount of catalyst and TCP concentration are investigated. TCP photocatalytic degradation process was optimized. It is observed that to get better photocatalytic activity optimum amount of photocatalyst and concentration of TCP solution required are 1.0 gL -1 and 20 mg L -1 respectively. Reusability study indicates that C doped TiO2 prepared in the present work is highly stable and reusable photo catalyst.

A new approach to δ15N compound‐specific amino acid trophic position measurements: preparative high pressure liquid chromatography technique for purifying underivatized amino acids for stable isotope analysis

Compound specific isotope analysis of amino acids (CSI‐AA) has emerged as an important new method for investigating trophic dynamics in both aquatic and terrestrial systems. Multiple studies have shown that δ15N values of glutamic acid (Glu) and phenylalanine (Phe) can be coupled to provide precise estimates of trophic position (TP), while simultaneously decoupling baseline δ15N values from the effects of trophic transfer. However, the current standard gas chromatography‐combustion‐isotope ratio mass spectrometry (GC‐C‐IRMS) approach is limited by high expense, limited availability, and relatively low precision. We present a new method for making TP estimates in biological samples by CSI‐AA (TPCSIA), based on a high‐pressure liquid chromatography (HPLC) purification of underivatized amino acids, followed by offline elemental analysis‐isotope ratio mass spectrometry (EA‐IRMS). We compare results from our new HPLC/EA‐IRMS method versus GC‐C‐IRMS in both standard and natural materials. Nitrogen isotopic values of purified Glu and Phe standards were identical within error for both methods. In five widely different marine organisms, the δ15N values of Glu and Phe were also indistinguishable within error between the two approaches; however, the δ15N values produced by the HPLC/EA‐IRMS approach had higher average precision (average SD = 0.3 ± 0.2 ‰) than the GC‐C‐IRMS measurements (average SD = 0.45 ± 0.15 ‰). The resulting TPCSIA estimates were statistically indistinguishable (t &lt; 1.2, df = 6, P &gt; 0.3) between the two methods for all organisms examined. Our HPLC/EA‐IRMS method may therefore allow significant expansion of TPCSIA applications, requiring only commonly available instrumentation to produce high precision TPCSIA values.