PubMed | 411 Ca Inc., GL Sciences Inc., Kyoto University, AB SCIEX and 2 more.
Type: | Journal: Journal of chromatography. A | Year: 2015
Prototype small-size (1.0mm I.D., 5cm long) columns for reversed-phase HPLC were evaluated in relation to instrument requirements. The performance of three types of columns, monolithic silica and particulate silica (2m, totally porous and 2.6m, core-shell particles) was studied in the presence of considerable or minimal extra-column effects, while the detector contribution to band broadening was minimized by employing a small size UV-detector cell (6- or 90nL). A micro-LC instrument having small system volume (<1L) provided extra-column band variance of only 0.01-0.02L(2). The three columns generated about 8500 theoretical plates for solutes with retention factor, k>1-3 (depending on the column), in acetonitrile/water mobile phase (65/35=vol/vol) at 0.05mL/min, with the instrument specified above. The column efficiency was lower by up to 30% than that observed with a 2.1mm I.D. commercial column. The small-size columns also provided 8000-8500 theoretical plates for well retained solutes with a commercial ultrahigh-pressure liquid chromatography (UHPLC) instrument when extra-column contributions were minimized. While a significant extra-column effect was observed for early eluting solutes (k<2-4, depending on column) with methanol/water (20/80=vol/vol) as weak-wash solvent, the use of methanol/water=50/50 as wash solvent affected the column efficiency for most analytes. The results suggest that the band compression effect by the weak-wash solvent associated with partial-loop injection may provide a practical means to reducing the extra-column effect for small-size columns, while the use of an instrument with minimum extra-column effect is highly desirable.
Yoshida T.,Hiroshima University |
Farone W.A.,411 Ca Inc. |
Xantheas S.S.,Pacific Northwest National Laboratory
Journal of Physical Chemistry B | Year: 2014
We report extensive conformational searches of the gas-phase neutral nicotine, nornicotine, and their protonated analogs and the pathways and barriers for the interconversion between their various isomers that are based on ab initio second-order Møller-Plesset perturbation (MP2) electronic structure calculations. Initial searches were performed with the 6-31G(d,p), and the energetics of the most important structures were further refined from geometry optimizations with the larger aug-cc-pVTZ basis set. On the basis of the calculated free energies at T = 298 K for the gas-phase molecules, neutral nicotine has two dominant trans conformers, whereas neutral nornicotine is a mixture of several conformers. For nicotine, the protonation on both the pyridine and the pyrrolidine sites is energetically competitive, whereas nornicotine prefers protonation on the pyridine nitrogen. The protonated form of nicotine is mainly a mixture of two pyridine-protonated trans conformers and two pyrrolidine-protonated trans conformers, whereas the protonated form of nornicotine is a mixture of four pyridine-protonated trans conformers. Nornicotine is conformationally more flexible than nicotine; however, it is less protonated at the biologically important pyrrolidine nitrogen site. The lowest energy isomers for each case were found to interconvert via low (<6 kcal/mol) rotational barriers around the pyridine-pyrrolidine bond. These barriers are much lower than previous estimates based on lower levels of theory obtained without relaxation of the structure along the path. Nicotine was found to bind more strongly to tryptophan (Trp) than nornicotine, a finding that is consistent with nicotine's enhanced affinity in the nicotinic acetylcholide receptor. © 2014 American Chemical Society.
Sanchez A.C.,411 Ca Inc. |
Friedlander G.,411 Ca Inc. |
Fekete S.,University of Geneva |
Anspach J.,411 Ca Inc. |
And 3 more authors.
Journal of Chromatography A | Year: 2013
Innovative columns made with very small core-shell particles (1.0-1.4 μm) were investigated over a wide experimental space using state-of-the-art ultra high performance liquid chromatography (UHPLC) instruments. Among the columns tested is one that is now commercially available and is made with 1.3 μm core-shell particles consisting of non-porous cores about 0.9 μm in size and porous shells <0.2 μm thick. This work demonstrated that exceptionally low observed minimum plate heights of 2.2 μm could be obtained using columns packed with 1.3 μm particles, corresponding to a plate count of over 450,000 plates/m. It was shown that only low volume columns allow operation under optimal conditions with current top-of-the-line UHPLC instruments. It was also demonstrated that the loss in performance caused by frictional heating effects remains negligible. Finally, the practical utility of these columns was confirmed with several real-world applications requiring extreme resolving power (i.e. peptide mapping, sample typical of metabolomic studies and crude human insulin). The performance achieved was compared to that of a reference UHPLC column packed with 1.7 μm fully porous particles. The column packed with 1.3 μm particles gave peak capacity values that were 20-40% higher than the reference column for the same analysis time. © 2013 Elsevier B.V.
Sanchez A.C.,411 Ca Inc. |
Anspach J.A.,411 Ca Inc. |
Farkas T.,411 Ca Inc.
Journal of Chromatography A | Year: 2012
The observed performance when using high efficiency, low volume (U)HPLC columns has and continues to be limited by the extra column dispersion introduced by the chromatographic system. Even with the latest UHPLC instruments the injection and detection systems are still major contributors to peak broadening, especially when using 50 mm × 2.1 mm columns. A previously described injection technique now termed Performance Optimizing Injection Sequence (POISe) was shown to reduce or eliminate the impact of the injection system on the observed chromatographic performance. The POISe technique involves injecting a defined volume of weak solvent along with the sample in order to increase retention factors during sample loading. In the present study, a newly developed equation describing the phenomena involved during sample introduction is presented and shows that analyte bands are compressed at the head of the column in proportion to their retention factor independent of the elution mode (i.e. gradient or isocratic). This phenomenon is termed isocratic focusing and is shown to be most effective with analytes having retention factors in the range of 0.4-3. Additionally, it is shown that gradient compression plays a minor role in band compression when using this technique with analytes having retention factors of 1 or higher. The POISe technique is further investigated experimentally to determine its optimum configuration. It is also demonstrated to be effective with different HPLC and UHPLC instrument platforms and different high efficiency columns, such as those packed sub-2 μm and core-shell particles. © 2012.
Layne J.,411 Ca Inc. |
Lomas S.,411 Ca Inc. |
Misa A.,411 Ca Inc.
American Laboratory | Year: 2014
Experts describe the benefits of methods using mass spectrometry detection for contaminants testing and provide some considerations for maximizing chromatographic performance via LC/MS and LC/MS/MS to improve data quality for both food contaminant screening and confirmatory methods. The goal is to provide guidance and insight to assist laboratory analysts in developing reliable and surgical analytical methods that can be used to determine the compliance of food substances with national and international regulations. A screening method is used to sift through large numbers of samples in a relatively short period of time to find potentially noncompliant samples. The goal is qualitative in nature and meant to determine whether any of these contaminants are present in this sample. MS detection has greatly improved the ability to positively identify suspected contaminants at extremely low levels in samples and this has resulted in LC/MS techniques emerging as important and reliable analytical tools.
De Paoli G.,Oak Ridge National Laboratory |
Lewis Sr. S.A.,Oak Ridge National Laboratory |
Schuette E.L.,Oak Ridge National Laboratory |
Lewis L.A.,Oak Ridge National Laboratory |
And 2 more authors.
Journal of Forensic Sciences | Year: 2010
Photo- and thermal-degradation studies on eccrine fingerprint components are presented herein. Dilute distinct solutions of urea, lactic acid, and seven amino acids were deposited on steel coupons and Teflon ® disks, exposed to artificial sunlight or heat, extracted, and analyzed. This aim of this study was to determine whether the investigated eccrine components, previously determined to be Raman active for a parallel study, experienced photo- or thermally induced degradation, and if so, to determine the rate and identify any detectable products. Neither the amino acids nor urea exhibited photo-degradation; however, when heated for a period of three minutes, the onset of thermal-degradation was initiated at 100°C for the amino acids and 100°C for urea. Lactic acid, the major polymerization initiator of superglue fuming, showed photochemical and thermal-degradation. These results could be used for future development of new latent fingerprint visualization methods, especially when lactic acid is degraded. © 2010 American Academy of Forensic Sciences.
PubMed | 411 Ca Inc.
Type: | Journal: Journal of chromatography. A | Year: 2013
Innovative columns made with very small core-shell particles (1.0-1.4m) were investigated over a wide experimental space using state-of-the-art ultra high performance liquid chromatography (UHPLC) instruments. Among the columns tested is one that is now commercially available and is made with 1.3m core-shell particles consisting of non-porous cores about 0.9m in size and porous shells <0.2m thick. This work demonstrated that exceptionally low observed minimum plate heights of 2.2m could be obtained using columns packed with 1.3m particles, corresponding to a plate count of over 450,000 plates/m. It was shown that only low volume columns allow operation under optimal conditions with current top-of-the-line UHPLC instruments. It was also demonstrated that the loss in performance caused by frictional heating effects remains negligible. Finally, the practical utility of these columns was confirmed with several real-world applications requiring extreme resolving power (i.e. peptide mapping, sample typical of metabolomic studies and crude human insulin). The performance achieved was compared to that of a reference UHPLC column packed with 1.7m fully porous particles. The column packed with 1.3m particles gave peak capacity values that were 20-40% higher than the reference column for the same analysis time.
Chen D.Z.,Verizon Wireless |
Chen Y.,411 Ca Inc. |
Wu P.-T.,411 Ca Inc. |
Gean M.,411 Ca Inc.
2016 Optical Fiber Communications Conference and Exhibition, OFC 2016 | Year: 2016
This paper presents optical and environmental test results on SC-UPC pigtails terminated with Ferrolder® and zirconia ferrules. The Ferrolder, a ferrule and holder in one solution, is an epoxy-less replacement for ceramic ferrule and holder. © 2016 OSA.
Chen Y.,411 Ca Inc. |
Chen D.Z.,Verizon Wireless |
Wu P.-T.,411 Ca Inc. |
Mengesha T.,411 Ca Inc. |
Gean M.,411 Ca Inc.
5th IEEE Photonics Society Optical Interconnects Conference, OI 2016 | Year: 2016
An epoxy-less, metallic, single-fiber ferrule, Ferrolder®, has been developed and fabricated by a breakthrough ultra-high precision stamping process. Optical and mechanical validation test results on SC/UPC pigtails terminated with Ferrolder and zirconia have been presented. © 2016 IEEE.