University of North Florida
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Stuart Chalk, Ph.D.
Department of Chemistry
University of North Florida
Phone: 1-904-620-1938
Fax: 1-904-620-3535
Email: schalk@unf.edu
Website: @unf

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Ira S. Krull

Abbrev:
Krull, I.S.
Other Names:
Address:
Department of Chemistry and the Barnett Institute, Northeastern University, Boston, MA 02115 U.S.A.
Phone:
617.373.2862
Fax:
617.373.8795

Citations 16

"Photoelectrochemical Detection In Analytical Chemistry"
Trends Anal. Chem. 1985 Volume 4, Issue 5 Pages 118-124
William R. LaCourse and Ira S. Krull

Abstract: In this review, the role of photoelectrochemical detection in, e.g., liquid chromatography, HPLC and flow injection analysis is discussed. Over the past five years, photoelectrochemical detection as an analytical technique has been increasing in importance. Contributing factors in this new popularity are the rapid and unique reactions possible with photochemistry, and the superior selectivity and sensitivity of electrochemical detection. (43 references).
HPLC Spectroelectrochemistry Review

"Derivatization And Post-column Reactions For Improved Detection In Liquid Chromatography - Electrochemistry"
J. Liq. Chromatogr. Relat. Technol. 1985 Volume 8, Issue 15 Pages 2845-2870
Ira S. Krull; Carl M. Selavka; Chester Duda; Wesley Jacobs

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.
LC Electrochemical analysis Review Post-column derivatization Pre-column derivatization

"Trace Analysis For Explosives And Related Compounds Via High Performance Liquid Chromatography - Photolysis - Electrochemical Detection"
J. Forensic Sci. 1984 Volume 29, Issue 2 Pages 449-463
Krull IS, Ding X-D, Selavka C, Bratin K, Forcier G

Abstract: The cited methods (apparatus illustrated) have been applied in the analysis of standard explosives (e.g., 2,4,6-trinitrotoluene, dinitrotoluene and N-methyl-2,4,6,N-tetranitroaniline and other organic nitro-compounds) by using single- or dual-electrode detection. The responses of the dual-electrode detector were found to be a function of applied working potentials. The dual-electrode technique, which showed greater sensitivity than the single-electrode method, was applicable in the analysis of explosives, drugs, nitrate ester compounds, nitro-aromatics, nitro-PAH and similar such derivatives. Calibration graphs and rectilinearities of detector response for various nitro-compounds are given. Flow injection analysis - photolysis - electrochemical detection and HPLC - photolysis - electrochemical detection may be of value in organic or inorganic trace analysis.
Drugs Nitro compounds 2,4,6-Trinitrotoluene 2,4-Dinitrotoluene N-methyl-N,2,4,6-tetranitroaniline HPLC Electrode Photochemistry Post-column derivatization

"Derivatization Of Alkyl Halides, Acid Chlorides And Other Electrophiles With Polymer-immobilized 8-amino-2-naphthoxide"
J. Chromatogr. Sci. 1988 Volume 26, Issue 10 Pages 501-512
Colgan, S.T.;Krull, I.S.;Dorschel, C.;Bidlingmeyer, B.A.

Abstract: Details are given for the normal- or reversed-phase HPLC determination of the cited compounds, with isocratic or gradient elution and UV, fluorimetric or amperometric detection. The 8-amino-2-naphthoxide was immobilized on AG1-X8 resin (Cl- form; Bio-Rad), which was packed into a column (3.3 cm x 3.9 mm) for use in pre- or post-analytical column derivatization. The acid chlorides react fast enough to allow online derivatization. Detection limits were in the sub-ppb range. The method was applied in the determination of cis- and trans-1,3-dichloropropene in water.
1,3-Dichloropropene Water HPLC Amperometry Fluorescence Spectrophotometry Immobilized reagent Post-column derivatization PPB

"General Strategies And Selection Of Derivatization Reactions For Liquid Chromatography And Capillary Electrophoresis"
J. Chromatogr. B 1994 Volume 659, Issue 1-2 Pages 1-17
Ira S. Krulla,*, Zdenek Deylb and Hnk Lingemanc

Abstract: 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.
LC Electrophoresis Review

"Determination Of Inorganic Anions By Flow Injection Analysis And High Performance Liquid Chromatography Combined With Photolytic-electrochemical Detection"
J. Chromatogr. A 1990 Volume 499, Issue 1 Pages 685-697
L. Dou and I. S. Krull

Abstract: Post-column, online photolytic derivatization in liquid chromatography with electrochemical detection for some inorganic anions is described. Flow injection analysis and ion-pair reversed-phase chromatography followed by photolysis and electrochemical detection were used for the determinations of anions. Several operation conditions, such as mobile phase, lamp used for the photolysis, flow-rate, and applied potential, have been optimized for the determinations. Analytical figures of merit were determined. Method validation was carried out by the analysis of single blind, spiked samples. Inherent from the advantages of electrochemical detection in liquid chromatography, the method is of high sensitivity and selectivity for anion analysis.
Anions, inorganic HPLC Electrochemical analysis Post-column derivatization Optimization Sensitivity Selectivity Photochemistry

"Trace Analysis Of Organothiophosphate Agricultural Chemicals By High Performance Liquid Chromatography-photolysis-electrochemical Detection"
J. Agric. Food Chem. 1984 Volume 32, Issue 3 Pages 622-628
Xiang Dong Ding and Ira S. Krull

Abstract: Organic thiophosphate agricultural chemicals, malathion, parathion and others, can be analyzed by the newer method of high performance liquid chromatography (HPLC) with online photolysis (hv), followed by electrochemical detection (EC) using single- or dual-electrode approaches for the species generated. This approach, HPLC-hv-EC, was applied to ~20 thiophosphates, most of which were widely used agriculturally and for which trace residue levels were routinely monitored. Dual-electrode response ratios were determined for all analytes, along with minimum detection limits (MDL) in many cases. These approaches were also used for the quality control evaluation of commercial formulations by flow injection analysis (FIA) with hv-EC and no HPLC separations. Wheat middling extracts were analyzed by the commonly used gas chromatography (GC) flame photometric detection (FPD) method of residue analysis, and by HPLC-hv-EC. These comparative studies indicate that the newer method was reproducible, accurate, precise and reliable. Standard additions were applied to wheat middling extracts, and the quantitative results were compared with the external standard method.
Malathion Parathion Wheat Electrochemical analysis UV reactor Photochemistry Standard method Method comparison Standard additions calibration

"Electrochemical Detection As An Alternative To UV In RP-HPLC Peptide Mapping"
Electroanalysis 1994 Volume 6, Issue 1 Pages 1-8
L. Chen, I. S. Krull *

Abstract: A 0.5 mL portion of cytochrome C solution, as an e.g., (2 mg/mL in 100 mM NH4HCO3 buffer, pH 8) was mixed with 0.5 mL of trypsin (0.1 mg/mL) and incubated at 37°C for 24 h. After digestion, the sample was frozen in a dry ice/acetone mixture and lyophilised at -40°C for 24 h and dissolved in water. A 20 µL portion of the solution was analyzed by HPLC on a YMC AP-303 S-5 300A ODS column (25 cm x 4.6 mm i.d.) equipped with a Supelguard LC-18 pre-column (2 cm) with gradient elution (flow rate not given) with propan-2-ol/methanol/H2O/trifluoroacetic acid/100 mM phosphate buffer of pH 2.8-4.5 (details given). Electrochemical detection was performed with a dual vitreous C working electrode, a stainless-steel auxiliary electrode and a Ag/AgCl reference electrode. Post-column derivatization was performed in a knitted open tubular reactor knitted with PTFE tubing (16 x 0.5 mm i.d.) wrapped around a Hg lamp at 254 nm. Using photoradiation some non-electroactive amino-acids and peptides can be made electroactive increasing the sensitivity and selectivity of the electrochemical detection. Sensitivity was improved by one order of magnitude over UV detection.
Peptides HPLC Electrode Post-column derivatization Knotted reactor Open tubular reactor Photochemistry

"Identification Of Photochemical Products Of Amino-acids, Peptides, And Proteins In Online, Post-column Photolytic Derivatization Detection By HPLC - Electrochemistry"
Electroanalysis 1992 Volume 4, Issue 4 Pages 381-391
Lin Dou, Ira S. Krull

Abstract: In order to facilitate the online electrochemical detection of aromatic amino acids, peptides and proteins in HPLC, a post-column photolytic derivatization technique was developed (cf. Anal. Chem., 1990, 62, 2599) to convert non-electroactive compounds into electroactive derivatives. Further experiments have been carried out on model compounds (e.g. phenylalanine, tyrosine, cystine, tyrosine-glycine, phenylalanine-glycine, insulin and ribonuclease A) in order to understand the detection mechanisms. Photolysis was carried out offline and the decomposition products were identified mainly by HPLC. Photolytic processes that occurred in proteins included disulfide bond cleavage, photolysis of side-chain amino acids, and conformational changes. In most instances the electrochemical activity of proteins can be improved by photolysis thereby providing a means of improving the electrochemical detection of such compounds.
Amino Acids Peptides Proteins Phenylalanine Tyrosine Cystine Insulin Enzyme, ribonuclease a HPLC Electrochemical analysis Post-column derivatization Photochemistry

"Characterization Of Proteins Separated By Displacement Chromatography Using Low-angle Laser-light-scattering Photometry"
Chromatographia 1994 Volume 38, Issue 5-6 Pages 349-354
R. Mhatre, R. Qian, I. S. Krull, S. Gadam, S. M. Cramer

Abstract: Displacement chromatography with low-angle laser-light-scattering (LALLS) photometric detection was used to measure the mol. wt. of β-lactoglobulin A and B. A feed solution (1 ml) containing 20 mg/ml of β-lactoglobulin in the mobile phase (75 mM Tris-HCl buffer of pH 7.5) was passed (0.1 ml/min) through a Protein-Pak Q-8HR anion-exchange column (10 cm x 5 mm i.d.); after 10 min, 7 mL of dextran sulfate displacer solution (20 mg/ml) was injected through a switching valve. A Thermo Separation Products model KMX-6 LALLS photometer and a UV detector (310 nm) were used for the online measurement of the mol. wt. Both forms of the analyte were eluted as dimers, and LALLS photometry was able to detect these and also their impurities. The mol. wt. of the proteins were 6-8% higher than the theoretical value for a dimer, and the presence of aggregates was indicated by LALLS photometry, but not by the UV signal. Comparative studies were also carried out by size-exclusion chromatography and FIA before LALLS and UV detection, and the results are reported.
β-Lactoglobulin Protein HPIC Spectrophotometry Method comparison

"Immunodetection Approaches And High Performance Immunoaffinity Chromatography For An Analogue Of Bovine Growth Hormone Releasing Factor At Trace Levels"
Biomed. Chromatogr. 1996 Volume 10, Issue 6 Pages 337-345
Richard A. Strong, Byung-Yun Cho, Daniel H. Fisher, John Nappier, Ira S. Krull

Abstract: An indirect detection method using high performance immunoaffinity chromatography (HPIAC) was used to measure low levels of an analogue of bovine Growth Hormone Releasing Factor (bGHRF). An antibody (Ab) labelled with alkaline phosphate (ALP) was incubated with the bGHRF analogue to perform a complex between the antigen (Ag) and the antibody- enzyme (Ab-En) conjugate. The complex was then injected onto a cartridge containing an immobilized Ag affinity support. Species which were not recognized by the affinity cartridge, i.e. eluted, were then directly combined, via a connecting tee, with a buffer containing a substrate. Incubation proceeded online, inside a knitted reactor coil, under conditions of constant flow. The subsequent generation of a fluorescently active substrate product was detected by conventional means. The assay described has a linear response region from 1.0 to 25 ng of the bGHRF analogue and a limit of detection of 0.60 ng (1.7 x 10(2) femtomole, 30 p.p.b.). This approach was compared against a method in the antigen/Ab-En complex was injected onto a immobilized Ab affinity cartridge to form an antibody-antigen conjugate sandwich and subsequent stop-flow incubation with substrate.
Chromatography HPLC Knotted reactor Stopped-flow

"Determination Of Online Differential Refractive Index And Molecular Weight Via Gradient HPLC Interfaced With Low-angle Laser Light Scattering, Ultraviolet, And Refractive Index Detection"
Anal. Chem. 1993 Volume 65, Issue 3 Pages 283-286
Rohin Mhatre and Ira S. Krull

Abstract: Pancreatic ribonuclease, trypsinogen and α-chymotrypsinogen were dissolved in 5 mM bis-Tris/0.2 M dextrose (buffer A), to give solution of 2.5-3.5 mg/ml and applied to a column (10 cm x 4.6 mm) of strong cation-exchange polymer-based packing operated with gradient elution (0.5 ml/min) with buffer A and 5 mM bis-Tris/0.5 M NaCl (buffer B) from 0-80% buffer B over 20 min with online detection using a low-angle laser light scattering photometer, a UV-visible detector at 280 nm and a laser-based differential refractive index detector at 670 nm connected in series with a PC for data collection and processing. The system was also used in the FIA mode to measure the molar absorptivities of the proteins. Off-line refractive index measurements were performed with a laser-based differential refractometer, at 633 nm. Online differential refractive index measurements were similar to those determined off-line and required less sample (3-4 mg as opposed to 200 mg). Molecular wt. determinations agreed with literature values to within 3% and protein recoveries ranged from 66-87%. Other biopolymers, such as DNA fragments can be characterized using the same conditions.
Ribonucleosides Nucleic acids, deoxyribo Muscle HPLC Spectrophotometry Refractive index

"Complete Online Determination Of Biopolymer Molecular Weight Via High Performance Liquid Chromatography Coupled To Low-angle Laser Light Scattering, Ultraviolet, And Differential Refractive Index Detection"
Anal. Chem. 1990 Volume 62, Issue 19 Pages 2107-2114
Hans H. Stuting and Ira S. Krull

Abstract: An optically modified high performance liquid chromatography refractive index detector was developed to allow complete online determinations for biopolymer molecular weights. Online concentration, refractive index, specific refractive index increment (dn/dc2)µ, and Rayleigh factor were determined under flow injection analysis (FIA) and size exclusion chromatography (SEC) conditions using low-angle laser light scattering, ultraviolet, and modified refractive index detection. This instrumental system is capable of determining absolute online molecular weights. The error and time requirements involved in conventional methodologies for proteins have been reduced. Sample quantities have been reduced from 150 to 200 mg, in conventional off-line methods, to less than 2 mg for online FIA and 0.5 mg for online SEC, if mass absorptivities (a) are known. Otherwise, the determination of a will be the most sample-demanding step, requiring about 3 mg of the pure protein. Online measurements of (dn/dc2)µ are in good agreement with traditional off-line values established at Donnan equilibrium (usually within 5%). In addition, this technique provides true injected mass as determined by the UV detector, after chromatographic exposure where losses may occur, which is then used in the calculation of biopolymer molecular weight.
Polymers HPLC Spectrophotometry Refractometry Refractive index Detector

"Photoelectrochemical Detector For High Performance Liquid Chromatography And Flow Injection Analysis"
Anal. Chem. 1985 Volume 57, Issue 9 Pages 1810-1814
William R. LaCourse, Ira S. Krull, and Karl Bratin

Abstract: A flow-through thin-layer amperometric cell (Bioanalytical Systems model LC-4B) modified to allow optical irradiation of the surface of the working electrode is connected to a HPLC or flow injection system. The detector (which incorporates vitreous-carbon and silver - AgCl electrodes) is responsive to alkyl and aryl ketones and aldehydes. Response is rectilinear over 3 to 4 decades of concentration, and replicate injection reproducibility is within 2%. Detection limits of conjugated carbonyl derivatives are 2 to 10 ng.
Ketones Aldehydes Amperometry HPLC Electrode Electrode Spectroelectrochemistry Detector

"Electroanalytical Voltammetry In Flowing Solutions"
Anal. Chim. Acta 1986 Volume 180, Issue 1 Pages 187-250
Dennis C. Johnson, Stephen G. Weber, Alan M. Bond, R. Mark Wightman, Ronald E. Shoup, Ira S. Krull

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 (<10 µL) for voltammetric and amperometric detection in flowing solutions. Emphasis is placed on factors contributing to high sensitivity, reliability and selectivity of ec detection as an integral part of larger analytical systems utilizing continuously flowing, unsegmented streams, e.g., flow-injection and liquid chromatographic analyzes. Solid and mercury electrodes are considered under potentiostatic and potentiodynamic control. A review is given also of auxiliary chemical and photolytic derivatizations coupled to ec detection. The majority of the literature on the subject relates to liquid chromatography with electrochemical detection (l.c./ec); however, applications to these concepts to specific examples in flow-injection systems, as well as for on-line process control, should be obvious. Details of chromatographic separations and design of total analytical systems are not reviewed.
Amperometry Voltammetry Review

"Peptide Mapping Using EOF-driven Capillary Isoelectric Focusing"
Anal. Biochem. 1993 Volume 208, Issue 2 Pages 323-329
Mazzeo J. R., Martineau J. A. and Krull I. S.

Abstract: Capillary isoelectric focusing (CIEF) in uncoated and commercially available coated capillaries was applied to the separation of tryptic peptides from bovine and chicken cytochrome c. This is the first report of peptide mapping by CIEF. Before separation, the pIs of individual peptides expected to be formed during the digest were calculated, and then the separation pattern obtained was correlated with the calculated pIs. This correlation was reasonably good for some peptides, but not as good for others. However, differentiation of the two species digests was easily achieved based on the CIEF map. The major limitation of the method is the fact that uv detection at 280 nm must be employed, meaning that only tryptophan and tyrosine containing peptides will be detected, since the ampholytes used to generate the pH gradient absorb below 280 nm. Post-column derivatization of the peptides is one solution to this problem. Migration time reproducibility was on the order of 2%, and run times were less than 20 min for the entire pH gradient range in the uncoated capillary. In the coated capillary, superior resolution was obtained at the expense of longer run times.
Peptides Spectrophotometry Isoelectric focusing Post-column derivatization pH gradient