Ira S. Krull

Electroanalytical voltammetry in flowing solutions

Abstract A review is given of the principles, key developments and representative applications of small electrodes in flow-through electrochemical (ec) detectors having very low effective dead volume (

Trace analysis and speciation for methylated organotins by HPLC-hydride generation-direct current plasma emission spectroscopy (HPLC-HY-DCP)

Total tin determinations can be accomplished at trace levels (10–25 ppb) by a continuous on-line hydride generation (HY), followed by direct current plasma (DCP) emission spectroscopy (HY-DCP). This approach is applicable for organotin compounds such as mono-, di-, and trimethyltin chloride, as well as stannous and stannic cations. HY-DCP methods of total tin analysis have been applied to a number of spiked and actual samples. Detection limits, calibration plots, sensitivities, and related analytical parameters have been evaluated. Organotin analysis and speciation can be accomplished by the interfacing of this HY-DCP step with high-performance liquid chromatography (HPLC), with the use of a polymeric PRP-1 type column with an acidic, ionic mobile phase, usually containing a suitable ion-pairing reagent. The overall speciation approach, HPLC-HY-DCP, has been evaluated with regard to separation conditions; detection limits; sensitivities; calibration plots; and applications to spiked water, clam juice, seawater, and tuna fish samples. The results suggest the suitability and reliability of this HPLC-HY-DCP approach for individual tin species. Other metal species capable of forming a hydride derivative on-line, in a continuous fashion, may also be suitable for speciation by HPLC-HY-DCP.

Speciation of Cr (III) and Cr (VI) Via Reversed Phase HPLC With Inductively Coupled Plasma Emission Spectroscopic Detection (HPLC-ICP) 24

Abstract Chromium ions, viz., chromic (Cr±3=III) and chromate (Cr±6 = VI), can be reliably, conveniently, reproducibly, and quickly separated and detected by the use of conventional paired-ion, reversed phase (RP) high performance liquid chromatography (HPLC) together with refractive index (RI) and/or inductively coupled plasma emission spectroscopic (ICP) detection. A number of novel paired-ion approaches have now been developed, using PIC A (tetrabutylammonium hydroxide) or PIC B (sodium n-alkyl sulfonate) separately in the mobile phase. This allows for the retention of each Cr species depending on the particular ion pairing reagent being used, while the remaining Cr ion elutes in the solvent front. Changing the ion pairing reagent reverses the overall situation. The total time for each HPLC analysis is about 10 mins. ICP detection provides for a complete, overall method of speciation for both Cr (III) and Cr (VI) via two separate injections, together with quantitation for both species. This method of u...

Capillary electrochromatography: An alternative to HPLC and CE

CEC is a technique that has attracted increased interest in recent years. It combines the advantages of high efficiency of electrophoretic separation methods with the greater selectivity characteristic of HPLC. In this paper we explore the use of CEC as a potential alternative to conventional HPLC, μ-HPLC, and CE. Recent developments, both theoretical and experimental, are reviewed. The practical aspects of application of CEC in various modes of separation are also discussed.

Improved detection and derivatization in capillary electrophoresis

Capillary electrophoresis is well known for its low mass detectabilities, but suffers from poor concentration detection limits. This review will discuss improvements in concentration detectability with an emphasis on derivatization methods. Sample concentration techniques and improved detector designs will also be discussed. Pre- and post-capillary derivatization methods for biofluid analytes such as amino acids, peptides, proteins, oligonucleotides, and oligosaccharides will be examined in detail.

Trace Analysis and Speciation for Arsenic Anions by HPLC-Hydride Generation Inductively Coupled Plasma Emission Spectroscopy

Abstract High performance liquid chromatography (HPLC) has already been successfully interfaced with inductively coupled plasma (ICP) emission spectroscopy for arsenic analysis and speciation. However, in many instances the overall minimum detection limits (MDLs) are inadequate for many environmental type samples. Arsine generation in a continuous, on-line fashion has been shown to provide for significantly improved MDLs by direct-ICP approaches. This hydride generation-ICP (HY-ICP) derivatization approach has now been successfully interfaced with paired-ion, reversed phase HPLC. This provides a doubly hyphenated technique, namely HPLC-HY-ICP in order to perform true metal/nonmetal speciation. Such methods of arsenic speciation have now been perfected with regard to minimum detection limits, linearity responses over several orders of magnitude, separation of various arsenic species from possible sample interferences, and related analytical matters. The final approaches have been applied both to spiked wat...

Improvements in the method developed for performing isoelectric focusing in uncoated capillaries

Abstract Capillary isoelectric focusing run times were reduced from 30 to 5 minutes through reversing the polarity and shortening the separation distance. Complete resolution was only obtained by increasing the concentration of tetramethylethylenediamine in the sample solution. Problems previously seen with acidic proteins were shown to be due to anodic drift in the ampholyte gradient, and were minimized by increasing the concentration of phosphoric acid in the anode buffer. The inability of the method to tolerate protein samples with salt is also discussed.

General strategies and selection of derivatization reactions for liquid chromatography and capillary electrophoresis.

The general strategies, reasons and the different possibilities for the derivatization of biomedically important compounds are reviewed. Different approaches apply for small versus large analyte molecules, different advantages and disadvantages are visualized with pre- and post-column arrangements. Particular interest is focused upon solid-phase derivatization reagents.

Derivatization and post-column reactions for improved detection in liquid chromatography/electrochemistry

Abstract A summary Is provided of most of Che reported derlvatizations that have been used for improved analyte detection in liquid chromatography with electrochemical detection (LCEC). These approaches include pre-column derivatizations and postcolumns chemical, photochemical or enzymatic reactions for oxidative EC detection. This review covers the literature up to early 1985, and includes information gathered from books, technical articles, previous reviews and scientific journal publications. Specific reagents, methods and instrumentation are described for those classes of compounds studied by derlvatization-LCEC, and suggestions for future experiments are included, where applicable. It is concluded that the future will likely Include the development of a great number of derivatizations which may be used in conjunction with LCEC for trace analysis.

Homogeneous fluorescent derivatization of large proteins.

A method of homogeneously derivatizing large proteins for highly sensitive analysis is described. Homogeneity of the derivative was realized by tagging all the free amino groups of proteins. With this method, alpha-chymotrypsinogen A, ovalbumin and bovine serum albumin were derivatized with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC). Prior to the derivatization, all the proteins were reduced and alkylated. After reacting the resulting unfolded proteins with excessive amounts of AQC, the samples were analyzed with matrix assisted laser desorption ionization-time of flight-mass spectrometry (MALDI-TOF-MS) to determine the derivatization degree. The results indicated that all three proteins had been, or had almost been, fully derivatized. HPLC and CE were used for characterizing these protein derivatives. Under the optimized fluorescence detection conditions, the detectability of the tagged proteins was 2400-6200 times better than that detected at UV 280 nm, 170-300 times better than detected at UV 214 nm, and 150-420 times better than measured with their native fluorescence.