Peter F. Lott

Rapid determination of trace amounts of selenium (IV), nitrite, and nitrate by high-pressure liquid chromatography using 2,3-diaminonaphthalene☆

Abstract Selenite, nitrite, and nitrate ions have been determined spectrophotometrically and fluorometrically using the reagent 2,3-diaminonaphthalene and high-pressure liquid chromatography. A fluorometric detector was constructed for the HPLC systems. The developed procedures were applied to the analysis of water and biological materials.

Gunshot residue determination by means of gunpowder stabilizers using high-performance liquid chromatography with electrochemical detection and analysis of metallic residues by graphite furnace atomic absorption spectrophotometry

Abstract A method for the determination of organic and inorganic components in gunshot residue is described. Analysis for the gunpowder stabilizers (diphenylamine, ethylcentralite, 2-nitrodiphenylamine) is performed by HPLC with oxidative electrochemical detection followed by graphite furnace atomic absorption spectrophotometry for the determination of trace metals (Sb, Ba, Pb). The coupling of these two methods yields substantial evidence as to the presence of a gunshot residue.

A rapid microdetermination of chlorine dioxide in the presence of active chlorine compounds

Abstract A titrimetric and spectrophotometric procedure has been developed for the determination of ClO2 in water samples. The procedure is rapid, accurate, and free of normal interferences present in water. It is based upon the reaction of ClO2 with substituted halophenol indicators.

Gunshot residue analysis via organic stabilizers and nitrocellulose

Abstract A high-performance liquid chromatographic (HPLC) procedure for the detection of gunshot residue by determination of the gunpowder constituents, diphenylamine and ethylcentralite, has been tested to ascertain if common substances in the environment give peaks in the chromatographic pattern at the same retention times. A number of substances produced such patterns. To provide discrimination, a method was developed for the determination of nitrocellulose during the hand swabbing after a firearm discharge. The nitrocellulose is extracted from the cotton swab with ether, evaporated to dryness, reconstituted with acetone, and dried with anhydrous sodium sulfate. The dried acetone solution is then applied and concentrated to a small portion of a heated potassium bromide IR pellet. Spectra of a nitrocellulose standard and a gunshot residue are compared and show several similar peaks. The procedure is set up so that an HPLC test for organic stabilizers and a Fourier transform infrared test for nitrocellulose can be run on one swabbing of a suspects hand. The absence of diphenylamine or ethylcentralite peaks in the HPLC chromatogram appears conclusive that under normal conditions a gunshot residue test is negative; a positive test necessitates confirmation such as the described IR procedure.

Gunshot residue analysis: An applicability study☆

Abstract Test firings were performed using 20 handguns and 20 ammunitions of various calibers and types to show the degree of reliability in the gunshot residue procedures described by D. B. Dahl and P. F. Lott (Microchem. J., 1987, 35, 347–359). The procedure entails analysis of a collected swab for gunpowder stabilizers by HPLC with electrochemical detection and analysis of the metallic content by graphite furnace atomic absorption.

An indirect atomic-absorption method for the determination of selenium.

Because of the difficulty in determining selenium directly, an indirect atomic-absorption method has been developed, based on two selective reactions that lead to the formation of the Pd(DanSe)(2)Cl(2) complex and measurement of the palladium absorption. Reaction conditions, separation techniques, effect of foreign ions, instrumental conditions and sample analysis in the sub-ppm range are described. The method is more sensitive than existing atomic-absorption methods for selenium.

2,3-Naphthotriazole as a gravimetric, spectrophotometric, and fluorimetric reagent for the determination of silver

Abstract 2,3-Naphthotriazole is suitable for the determination of macro- and muquantities of silver. The gravimetric (for 5–100 mg Ag) and spectrophotometric (e=1,000; 1–30 μg Ag ml ) methods are rapid and free of halide and foreign ion interferences; excellent selectivity is attained by means of masking agents. The fluorimetric method (0.025–0.1 μg Ag ml ) is much more sensitive than the spectrophotometric method but is more subject to interferences.

Ammonium 1-pyrrolidinedithiocarbamate as a reagent for bismuth

Abstract A spectrophotometric method and an atomic absorption procedure have been developed for the determination of bismuth in the presence of a large number of foreign ions, and in lead- and tin-containing alloys. The ammonium salt of 1-pyrrolidinecarbodithioic acid (APDC) and organic extractants were used. Masking agents and separation methods were employed to improve the selectivity; APDC reactions, extraction conditions, and distribution coefficients are described.

Naphtho[2,3-d]-2-selena-l,3-diazole as a reagent for the determination of macro to submicro quantities of palladium.

Five analytical procedures, gravimetric, spectrophotometric, radiometric, fluorometric and atomic-absorption, have been developed for the determination of macro to submicro amounts of palladium. The methods are based on the reaction of PdCl(2), with naphtho[2,3-d]-2-selena-l,3-diazole. Analytical conditions such as the reaction time, concentration ranges, effect of pH and of 68 foreign ions, and solvent extraction were studied. Information relating to the structure and formula of palladium-piazselenol reaction products is included.

Gunshot residue determination by high-performance liquid chromatography with electrochemical detection

Abstract A procedure for the detection of gunshot residue via the organic constituent diphenylamine is described. The method incorporates high-performance liquid chromatography with electrochemical detection.