@article{KurbanogluYarman2020,
  author    = {Kurbanoglu, Sevinc and Yarman, Aysu},
  title     = {Simultaneous determination of hydrochlorothiazide and irbesartan from pharmaceutical dosage forms with RP-HPLC},
  series = {Turkish journal of pharmaceutical sciences},
  volume    = {17},
  journal   = {Turkish journal of pharmaceutical sciences},
  number    = {5},
  publisher = {Turkish Pharmacists Association},
  address   = {{\c{C}}ankaya-Ankara},
  issn      = {1304-530X},
  doi       = {10.4274/tjps.galenos.2019.76094},
  pages     = {523 -- 527},
  year      = {2020},
  abstract  = {Objectives: In this work, a simple and rapid liquid chromatographic method for the simultaneous determination of irbesartan (IRBE) and hydrochlorothiazide (HCT) was developed and validated by reverse phase high performance liquid chromatography (RP-HPLC). <br /> Materials and Methods: Experimental conditions such as different buffer solutions, various pH values, temperature, composition of the mobile phase, and the effect of flow rate were optimized. <br /> Results: The developed RP-HPLC method for these antihypertensive agents was wholly validated and IRBE was detected in the linear range of 0.1-25 mu g mL(-1) and HCT was detected in the linear range of 0.25-25 mu g mL(-1). Moreover, the suggested chromatographic technique was successfully applied for the determination of the drugs in human serum and pharmaceutical dosage forms with limit of detection values of 0.008 mu g mL(-1) for IRBE and 0.012 mu g mL(-1) for HCT. <br /> Conclusion: The proposed rapid analysis method of these antihypertensive drugs can be easily used and applied by pharmaceutical companies for which the analysis time is important.},
  language  = {en}
}
@article{WatanabeTohgeBalazadehetal.2018,
  author    = {Watanabe, Mutsumi and Tohge, Takayuki and Balazadeh, Salma and Erban, Alexander and Giavalisco, Patrick and Kopka, Joachim and Mueller-Roeber, Bernd and Fernie, Alisdair R. and Hoefgen, Rainer},
  title     = {Comprehensive Metabolomics Studies of Plant Developmental Senescence},
  series = {Plant Senescence: Methods and Protocols},
  volume    = {1744},
  journal   = {Plant Senescence: Methods and Protocols},
  publisher = {Humana Press},
  address   = {Totowa},
  isbn      = {978-1-4939-7672-0},
  issn      = {1064-3745},
  doi       = {10.1007/978-1-4939-7672-0_28},
  pages     = {339 -- 358},
  year      = {2018},
  abstract  = {Leaf senescence is an essential developmental process that involves diverse metabolic changes associated with degradation of macromolecules allowing nutrient recycling and remobilization. In contrast to the significant progress in transcriptomic analysis of leaf senescence, metabolomics analyses have been relatively limited. A broad overview of metabolic changes during leaf senescence including the interactions between various metabolic pathways is required to gain a better understanding of the leaf senescence allowing to link transcriptomics with metabolomics and physiology. In this chapter, we describe how to obtain comprehensive metabolite profiles and how to dissect metabolic shifts during leaf senescence in the model plant Arabidopsis thaliana. Unlike nucleic acid analysis for transcriptomics, a comprehensive metabolite profile can only be achieved by combining a suite of analytic tools. Here, information is provided for measurements of the contents of chlorophyll, soluble proteins, and starch by spectrophotometric methods, ions by ion chromatography, thiols and amino acids by HPLC, primary metabolites by GC/TOF-MS, and secondary metabolites and lipophilic metabolites by LC/ESI-MS. These metabolite profiles provide a rich catalogue of metabolic changes during leaf senescence, which is a helpful database and blueprint to be correlated to future studies such as transcriptome and proteome analyses, forward and reverse genetic studies, or stress-induced senescence studies.},
  language  = {en}
}
@article{IslamKhalilMaenneretal.2017,
  author    = {Islam, Khan M. S. and Khalil, Mahmoud Abd Elhamid and Maenner, Klaus and Raila, Jens and Rawel, Harshadrai Manilal and Zentek, J{\"u}rgen and Schweigert, Florian J.},
  title     = {Lutein Specific Relationships among Some Spectrophotometric and Colorimetric Parameters of Chicken Egg Yolk},
  series = {The journal of poultry science},
  volume    = {54},
  journal   = {The journal of poultry science},
  publisher = {Japan Poultry Science Association},
  address   = {Tsukuba},
  issn      = {1346-7395},
  doi       = {10.2141/jpsa.0160065},
  pages     = {271 -- 277},
  year      = {2017},
  abstract  = {Lutein is an essential dietary carotenoid with health benefits and is inter alia responsible for the colouration of egg yolk. The relationship between lutein accumulation and egg yolk colouration was therefore studied in more detail. After feeding a low-luteine diet for 21 days, 14 birds (Lohmann brown hens aged 20 weeks) were fed a diet containing marigold (80 mg lutein/kg feed) and 14 other birds were fed a diet containing oleoresin (45 mg lutein/kg feed) for 21 days; for both groups of birds, this feeding period was followed by withdrawal for 21 days. The Roche Yolk Colour Fan (RYCF) score (0 to 15, where higher values denote greater colour intensity; R-2=0.87; P<0.01) and redness (R-2=0.89; P<0.01) increased with increasing lutein content of egg yolk. Total carotenoid content had a poor relationship with lightness (R-2=0.13; P>0.05) and yellowness (R-2=0.12; P>0.05) of the yolk. It may be concluded that increased lutein is potentially responsible for an increased RYCF score and redness (a*), but decreased yellowness (b*) and lightness (L*), of egg yolk.},
  language  = {en}
}
@article{ZuehlkeSassRiebeetal.2017,
  author    = {Z{\"u}hlke, Martin and Sass, Stephan and Riebe, Daniel and Beitz, Toralf and L{\"o}hmannsr{\"o}ben, Hans-Gerd},
  title     = {Real-Time Reaction Monitoring of an Organic Multistep Reaction by Electrospray Ionization-Ion Mobility Spectrometry},
  series = {ChemPlusChem},
  volume    = {82},
  journal   = {ChemPlusChem},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {2192-6506},
  doi       = {10.1002/cplu.201700296},
  pages     = {1266 -- 1273},
  year      = {2017},
  abstract  = {The capability of electrospray ionization (ESI)-ion mobility (IM) spectrometry for reaction monitoring is assessed both as a stand-alone real-time technique and in combination with HPLC. A three-step chemical reaction, consisting of a Williamson ether synthesis followed by a hydrogenation and an N-alkylation step, is chosen for demonstration. Intermediates and products are determined with a drift time to mass-per-charge correlation. Addition of an HPLC column to the setup increases the separation power and allows the determination of further species. Monitoring of the intensities of the various species over the reaction time allows the detection of the end of reaction, determination of the rate-limiting step, observation of the system response in discontinuous processes, and optimization of the mass ratios of the starting materials. However, charge competition in ESI influences the quantitative detection of substances in the reaction mixture. Therefore, two different methods are investigated, which allow the quantification and investigation of reaction kinetics. The first method is based on the pre-separation of the compounds on an HPLC column and their subsequent individual detection in the ESI-IM spectrometer. The second method involves an extended calibration procedure, which considers charge competition effects and facilitates nearly real-time quantification.},
  language  = {en}
}
@article{GhaffariBernhoeftEtheveetal.2019,
  author    = {Ghaffari, Morteza Hosseini and Bernhoeft, Katrin and Etheve, Stephane and Immig, Irmgard and Hoelker, Michael and Sauerwein, Helga and Schweigert, Florian J.},
  title     = {Technical note: Rapid field test for the quantification of vitamin E, beta-carotene, and vitamin A in whole blood and plasma of dairy cattle},
  series = {Journal of dairy science},
  volume    = {102},
  journal   = {Journal of dairy science},
  number    = {12},
  publisher = {Elsevier},
  address   = {New York},
  issn      = {0022-0302},
  doi       = {10.3168/jds.2019-16755},
  pages     = {11744 -- 11750},
  year      = {2019},
  abstract  = {Fast and easy tests for quantifying fat-soluble vitamins such as vitamin E and vitamin A, as well as beta-carotene, in whole blood without a need to preprocess blood samples could facilitate assessment of the vitamin status of dairy cattle. The objective of this study was to validate a field-portable fluorometer/spectrophotometer assay for the rapid quantification of these vitamins in whole blood and plasma of dairy cows and calves. We measured the concentrations of vitamin E and beta-carotene in whole blood and plasma from 28 dairy cows and 11 calves using the iCheck test (Bio-Analyt GmbH, Teltow, Germany) and compared the results with the current analytical standard (HPLC) in 2 independent laboratories, one at the University of Potsdam (Germany) and at one at DSM Nutritional Products Ltd. (Kaiseraugst, Switzerland). For vitamin A, the HPLC measurements were done only in the laboratory in Germany. The whole-blood concentrations of vitamin E as determined by iCheck (blood-hematocritcorrected) ranged from 1.82 to 4.99 mg/L in dairy cows and 0.34 to 3.40 mg/L in calves. These findings were moderately correlated (R-2 = 0.66) with the values assessed by HPLC in dairy cattle (cows + calves). When calves were excluded, the correlation was higher (R-2 = 0.961). The beta-carotene and vitamin A values obtained by the reference method HPLC were highly correlated with the iCheck methods in whole blood (R-2 = 0.99 and 0.88, respectively). In plasma, we observed strong correlations between the concentrations assessed by iCheck and those of HPLC for vitamin E (R-2 = 0.97), beta-carotene (R-2 = 0.98), and vitamin A (R-2 = 0.92) in dairy cattle (cows + calves). For vitamin E, beta-carotene, and vitamin A, we compared the relationship between the differences obtained by the iCheck assay and the HPLC measurements, as well as the magnitude of measurements, using Bland-Altman plots to test for systematic bias. For all 3 vitamins, the differences values were not outside the 95\% acceptability limits; we found no systematic error between the 2 methods for all 3 analytes.},
  language  = {en}
}
@article{IslamKhalilMaenneretal.2016,
  author    = {Islam, Khan Shaiful and Khalil, Mahmoud and M{\"a}nner, K. and Raila, Jens and Rawel, Harshadrai Manilal and Zentek, J. and Schweigert, Florian J.},
  title     = {Effect of dietary alpha-tocopherol on the bioavailability of lutein in laying hen},
  series = {Journal of animal physiology and animal nutrition},
  volume    = {100},
  journal   = {Journal of animal physiology and animal nutrition},
  publisher = {Wiley-Blackwell},
  address   = {Hoboken},
  issn      = {0931-2439},
  doi       = {10.1111/jpn.12464},
  pages     = {868 -- 875},
  year      = {2016},
  abstract  = {Lutein and its isomer zeaxanthin have gained considerable interest as possible nutritional ingredient in the prevention of age-related macular degeneration (AMD) in humans. Egg yolk is a rich source of these carotenoids. As an oxidative sensitive component, antioxidants such as -tocopherol (T) might contribute to an improved accumulation in egg yolk. To test this, chickens were fed lutein esters (LE) with and without -tocopherol as an antioxidant. After depletion on a wheat-soya bean-based lutein-poor diet for 21days, laying hens (n=42) were equally divided into three groups and fed the following diets for 21days: control (basal diet), a LE group (40mg LE/kg feed) and LE+T group (40mg LE plus 100mg T/kg feed). Eggs and blood were collected periodically. Carotenoids and -tocopherol in yolk and blood plasma were determined by HPLC. Egg yolk was also analysed for total carotenoids using a one-step spectrophotometric method (iCheck(())). Lutein, zeaxanthin, -tocopherol and total carotenoids in egg yolk were highest after 14days of feeding and decreased slightly afterwards. At the end of the trial, eggs of LE+T group contained higher amount of lutein (13.72), zeaxanthin (0.65), -tocopherol (297.40) and total carotenoids (21.6) compared to the LE group (10.96, 0.55, 205.20 and 18.0mg/kg, respectively, p<0.05). Blood plasma values of LE+T group contain higher lutein (1.3), zeaxanthin (0.06) and tocopherol (20.1) compared to LE group (1.02, 0.04 and 14.90mg/l, respectively, p<0.05). In conclusion, dietary -tocopherol enhances bioavailability of lutein reflecting higher content in egg yolk and blood plasma. Improved bioavailability might be due to increased absorption of lutein in the presence of tocopherol and/or a greater stability of lutein/zeaxanthin due to the presence of -tocopherol as an antioxidant.},
  language  = {en}
}
@article{VillatoroZuehlkeRiebeetal.2016,
  author    = {Villatoro, Jos{\´e} Andr{\´e}s and Z{\"u}hlke, Martin and Riebe, Daniel and Beitz, Toralf and Weber, Marcus and Riedel, Jens and L{\"o}hmannsr{\"o}ben, Hans-Gerd},
  title     = {IR-MALDI ion mobility spectrometry: physical source characterization and application as HPLC detector},
  series = {International journal for ion mobility spectrometry : official publication of the International Society for Ion Mobility Spectrometry},
  volume    = {19},
  journal   = {International journal for ion mobility spectrometry : official publication of the International Society for Ion Mobility Spectrometry},
  publisher = {Springer},
  address   = {Heidelberg},
  issn      = {1435-6163},
  doi       = {10.1007/s12127-016-0208-1},
  pages     = {197 -- 207},
  year      = {2016},
  abstract  = {Infrared matrix-assisted laser dispersion and ionization (IR-MALDI) in combination with ion mobility (IM) spectrometry enables the direct analysis of biomolecules in aqueous solution. The release of ions directly from an aqueous solution is based on a phase explosion, induced by the absorption of an IR laser pulse, which disperses the liquid as vapor, nano-and micro-droplets. The ionization process is characterized initially by a broad spatial distribution of the ions, which is a result of complex fluid dynamics and desolvation kinetics. These processes have a profound effect on the shape and width of the peaks in the IM spectra. In this work, the transport of ions by the phase explosion-induced shockwave could be studied independently from the transport by the electric field. The shockwave-induced mean velocities of the ions at different time scales were determined through IM spectrometry and shadowgraphy. The results show a deceleration of the ions from 118 m.s(-1) at a distance of 400 mu m from the liquid surface to 7.1 m.s(-1) at a distance of 10 mm, which is caused by a pile-up effect. Furthermore, the desolvation kinetics were investigated and a first-order desolvation constant of 325 +/- 50 s(-1) was obtained. In the second part, the IR-MALDI-IM spectrometer is used as an HPLC detector for the two-dimensional separation of a pesticide mixture.},
  language  = {en}
}
@article{ZuehlkeRiebeBeitzetal.2015,
  author    = {Z{\"u}hlke, Martin and Riebe, Daniel and Beitz, Toralf and L{\"o}hmannsr{\"o}ben, Hans-Gerd and Zenichowski, Karl and Diener, Marc and Linscheid, Michael W.},
  title     = {An electrospray ionization-ion mobility spectrometer as detector for high-performance liquid chromatography},
  series = {European journal of mass spectrometry},
  volume    = {21},
  journal   = {European journal of mass spectrometry},
  number    = {3},
  publisher = {WeltTrends},
  address   = {Sussex},
  issn      = {1469-0667},
  doi       = {10.1255/ejms.1367},
  pages     = {391 -- 402},
  year      = {2015},
  abstract  = {The application of electrospray ionization (ESI) ion mobility (IM) spectrometry on the detection end of a high-performance liquid chromatograph has been a subject of study for some time. So far, this method has been limited to low flow rates or has required splitting of the liquid flow. This work presents a novel concept of an ESI source facilitating the stable operation of the spectrometer at flow rates between 10 mu L min(-1) and 1500 mu L min(-1) without flow splitting, advancing the T-cylinder design developed by Kurnin and co-workers. Flow rates eight times faster than previously reported were achieved because of a more efficient dispersion of the liquid at increased electrospray voltages combined with nebulization by a sheath gas. Imaging revealed the spray operation to be in a rotationally symmetric multijet-mode. The novel ESI-IM spectrometer tolerates high water contents (<= 90\%) and electrolyte concentrations up to 10 mM, meeting another condition required of high-performance liquid chromatography (HPLC) detectors. Limits of detection of 50 nM for promazine in the positive mode and 1 mu M for 1,3-dinitrobenzene in the negative mode were established. Three mixtures of reduced complexity (five surfactants, four neuroleptics, and two isomers) were separated in the millisecond regime in stand-alone operation of the spectrometer. Separations of two more complex mixtures (five neuroleptics and 13 pesticides) demonstrate the application of the spectrometer as an HPLC detector. The examples illustrate the advantages of the spectrometer over the established diode array detector, in terms of additional IM separation of substances not fully separated in the retention time domain as well as identification of substances based on their characteristic IMs.},
  language  = {en}
}
@article{IslamSchweigert2015,
  author    = {Islam, Khan Md. Shaiful and Schweigert, Florian J.},
  title     = {Comparison of three spectrophotometric methods for analysis of egg yolk carotenoids},
  series = {Food chemistry},
  volume    = {172},
  journal   = {Food chemistry},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {0308-8146},
  doi       = {10.1016/j.foodchem.2014.09.045},
  pages     = {233 -- 237},
  year      = {2015},
  abstract  = {Carotenoids accumulated in the egg yolk are of importance for two reasons. Firstly they are important pigments influencing customer acceptance and secondly they are essential components with positive health effects either as antioxidants or as precursor of vitamin A. Different analytical methods are available to quantitatively identify carotenoids from egg yolk such as spectrophotometric methods described by AOAC (Association of Official Analytical Chemists) and HPLC (High Performance Liquid Chromatography). Both methods have in common that they are time consuming, need a laboratory environment and well trained technical operators. Recently, a rapid lab-independent spectrophotometric method (iCheck, BioAnalyt GmbH, Germany) has been introduced that claims to be less time consuming and easy to operate. The aim of the current study was therefore to compare the novel method with the two standard methods. Yolks of 80 eggs were analysed as aliquots by the three methods in parallel. While both spectrometric methods are only able measure total carotenoids as total beta-carotene, HPLC enables the determination of individual carotenoids such lutein, zeaxanthin, canthaxanthin, beta-carotene and beta-apocarotenoic ester. In general, total carotenoids levels as obtained by AOAC were in average 27\% higher than those obtained by HPLC. Carotenoid values obtained by the reference methods AOAC and HPLC are highly correlated with the iCheck method with r(2) of 0.99 and 0.94 for iCheck vs. AOAC and iCheck vs. HPLC, respectively (both p < 0.001). Bland Altman analysis showed that the novel iCheck method is comparable to the reference methods. In conclusion, the novel rapid and portable iCheck method is a valid and effective tool to determine total carotenoid of egg yolk under laboratory-independent conditions with little trained personal. (C) 2014 Elsevier Ltd. All rights reserved.},
  language  = {en}
}
@article{RailaEnjalbertMothesetal.2012,
  author    = {Raila, Jens and Enjalbert, Francis and Mothes, Ralf and Hurtienne, Andrea and Schweigert, Florian J.},
  title     = {Validation of a new point-of-care assay for determination of ss-carotene concentration in bovine whole blood and plasma},
  series = {Veterinary clinical pathology},
  volume    = {41},
  journal   = {Veterinary clinical pathology},
  number    = {1},
  publisher = {Wiley-Blackwell},
  address   = {Malden},
  issn      = {0275-6382},
  doi       = {10.1111/j.1939-165X.2012.00400.x},
  pages     = {119 -- 122},
  year      = {2012},
  abstract  = {Background: beta-Carotene is an important precursor of vitamin A, and is associated with bovine fertility. beta-Carotene concentrations in plasma are used to optimize beta-carotene supplementation in cattle, but measurement requires specialized equipment to separate plasma and extract and measure beta-carotene, either using spectrophotometry or high performance liquid chromatography (HPLC). Objective: The objective of this study was to validate a new 2-step point-of-care (POC) assay for measuring beta-carotene in whole blood and plasma. Methods: beta-carotene concentrations in plasma from 166 cows were measured using HPLC and compared with results obtained using a POC assay, the iCheck-iEx-Carotene test kit. Whole blood samples from 23 of these cattle were also evaluated using the POC assay and compared with HPLC-plasma results from the same 23 animals. The POC assay includes an extraction vial (iEx Carotene) and hand-held photometer (iCheck Carotene). Results: Concentrations of beta-carotene in plasma measured using the POC assay ranged from 0.40 to 15.84 mg/L (n = 166). No differences were observed between methods for assay of plasma (mean +/- SD; n = 166): HPLC-plasma 4.23 +/- 2.35 mg/L; POC-plasma 4.49 +/- 2.36 mg/L. Similar good agreement was found when plasma analyzed using HPLC was compared with whole blood analyzed using the POC system (n = 23): HPLC-plasma 3.46 +/- 2.12 mg/L; POC-whole blood 3.67 +/- 2.29 mg/L. Conclusions: Concentrations of beta-carotene can be measured in blood and plasma from cattle easily and rapidly using a POC assay, and results are comparable to those obtained by the highly sophisticated HPLC method. Immediate feedback regarding beta-carotene deficiency facilitates rapid and appropriate optimization of beta-carotene supplementation in feed.},
  language  = {en}
}