AFFF-MALS-RI for Determining the Mass and Size Distributions of Amylose and Amylopectins in Starch
February 1st 2016Integration of RI peak areas enabled calculation of the AMY:AMP ratios, in excellent agreement with the nominal values. The values for Mw and Rz fall within the generally accepted limits found in the literature. Conformational plots for the AMP component verify its branched nature.
Mechanisms of Interaction Responsible for Alternative Selectivity of Fluorinated Stationary Phases
February 1st 2016Fluorinated stationary phases, especially those including a pentafluorophenyl (PFP) moiety, have become popular alternatives to the more traditional alkyl (C8 and C18) phases. Many modern column lines have, in fact, been initially introduced with the standard C18 and a PFP phase because of their orthogonality. In this instalment, the differences between alkyl phases and PFP phases are discussed in terms of fundamental interactions. The origin of the interactions is also interpreted to better understand how analysts can use and control them to develop effective and rugged analytical methods.
Ultrahigh-Pressure Size-Exclusion Separations of Engineering Plastics: Challenges and Opportunities
January 31st 2016Ultrahigh-pressure size-exclusion chromatography (UHPSEC) can potentially offer a new direction and overcome some of the disadvantages (for example, limited resolution and long analysis time) associated with conventional SEC analysis. UHPSEC is based on using sub-3-µm silica-organic hybrid particles under elevated pressures (often above 400 bar) to improve the separation efficiency and increase analysis speed. In spite of the benefits promised by the chromatographic theory, there are some uncertainties that may limit the proliferation of UHPSEC in polymer analysis. As a result of possible issues associated with the use of a different stationary phase - including secondary interactions and polymer degradation - it is unclear whether UHPSEC will provide results comparable to those of traditional SEC methods. In this article, the advantages and challenges of UHPSEC for the analysis of different engineering thermoplastics are discussed, as well as a comparison of results obtained with UHPSEC and conventional SEC.
Detective Work, Part 3: Strong Retention and Chemical Problems with the Column
January 31st 2016This is the third “LC Troubleshooting” column in a series related to problems that we associate with liquid chromatography (LC) columns. This month is the first of several discussions looking at problems that are caused by chemical problems with the column.
Surfactant-Mediated Extractions, Part 1: Cloud-Point Extraction
January 31st 2016Cloud-point extraction (CPE) manipulates temperature and surfactant concentration to move aqueous solutes into a micelle phase for separation. Although CPE has been around for some time, it is still considered an emerging technique. Much of the development, and most applications, of CPE have dealt with extraction and preconcentration of inorganic solutes. More recently, attention has turned to the use of CPE in the isolation of organic solutes. This month, we review how CPE works and focus on applications for extracting organics.
Maximization of Selectivity in Reversed-Phase Liquid Chromatographic Method Development Strategies
January 30th 2016The selectivity of different combinations of organic modifiers, pH, and types of reversed-phase liquid chromatography (LC) materials has been characterized using Tanaka column characterization, linear solvent energy relationships (LSER), and selectivity correlations. The three characterization techniques highlighted the potential complementary selectivity of these phases and conditions as well as the type and dominancy of some of the retention mechanisms involved. Subsequently, selectivity differences were proven to be valid in the practical separation of acids, bases, and neutral analytes. This paper aims to assist chromatographers in producing highly efficiency method development strategies for reversed-phase LC separations in a relatively short time frame.
UCT A 30 Year Tradition of Excellence in Sample Preparation
January 29th 2016Since their beginnings in 1986, UCT has evolved into a major competitor in the field of silica based solid phase extraction technology. The first to pioneer commercially available ‘mixed-mode’ SPE products, 30 years later UCT is still optimizing sample analysis for forensic, pharmaceutical, clinical, environmental and agricultural laboratories. Michael J. Telepchak, founder and CEO UCT, Inc., has laid the foundation for this powerful technology and has truly served as a catalyst for its transformation from a novel technique to an industry gold standard. From fundamental chemistry to manufacturing and business development, he has bared witness to all facets of the evolution of solid phase extraction and will speak on the monumental impact it has made on the scientific community.
UCT: A 30 Year Tradition of Excellence in Sample Preparation
January 29th 2016Since their beginnings in 1986, UCT has evolved into a major competitor in the field of silica based solid phase extraction technology. The first to pioneer commercially available ‘mixed-mode’ SPE products, 30 years later UCT is still optimizing sample analysis for forensic, pharmaceutical, clinical, environmental and agricultural laboratories. Michael J. Telepchak, founder and CEO UCT, Inc., has laid the foundation for this powerful technology and has truly served as a catalyst for its transformation from a novel technique to an industry gold standard. From fundamental chemistry to manufacturing and business development, he has bared witness to all facets of the evolution of solid phase extraction and will speak on the monumental impact it has made on the scientific community.
The Effect of Microwave and Electron-Beam Treatments on Food and Packaging
January 20th 2016A team of researchers based in France has examined the consequences of microwave and electron-beam treatments on food and its packaging using high performance liquid chromatography (HPLC) and gas chromatography (GC).
Ion Exchange Sorbents for Metals Extraction- Analysis & Sorbent Use Selection Guide
January 19th 2016The use of ion-exchange sorbents for the preconcentration, separation and determination of metal ions is well established in the literature. Selection of an appropriate sorbent ensures both high efficiency in metal chelating while minimizing the mass of sorbent required for a particular analytical task. A high efficiency sorbent means that a smaller bed mass may be used thereby reducing the quantity of solvent required for elution yielding greater analytical sensitivity.
Pattern Modulation Offers Alternative to Pulse Modulation in GC×GC
January 19th 2016New research into flow modulation methods in valve-based two-dimensional gas chromatography (GC×GC) has produced an effective alternative to traditional pulse modulation.1 Described as “pattern modulation”, this new method increases effluent to the secondary column with flow rates compatible with most chromatographs and spectrometers.
Extending the Detection Limits for the Analysis of Organotin Contaminants Using Soft Ionization
January 19th 2016The inherent sensitivity and selectivity of time-of-flight mass spectrometry (TOF-MS) can be augmented by soft electron ionization (EI) to provide ultratrace-level quantitation of organotins in complex environmental extracts. These organotin species are a focus of current concern as environmental contaminants, but analysis using conventional 70 eV ionization energies is made difficult by their propensity to undergo extensive fragmentation. The use of soft EI helps to solve this problem by producing simplified spectra with enhanced diagnostic ions.
The LCGC Blog: Column Overload in Gas Chromatography with Vacuum Ultraviolet Detection
January 19th 2016Column overload is a very commonly encountered issue in gas chromatography (GC) for beginners. Changes in peak symmetry, generally observed as peak fronting, can be subtle in the sharp peaks generated by GC, but the result can be significant shifts in retention times, loss of resolution, and error in peak integration. LCGC Blogger Kevin Schug explains more.