Karen A. Wolnik

Arsenic speciation by ion chromatography with inductively coupled plasma mass spectrometric detection

Four As compounds were successfully separated and detected by single-column ion chromatography with inductively coupled plasma (ICP) mass spectrometric detection. The mass spectral interferent ArCl+ was reduced by chromatographically resolving chloride from the negatively charged arsenic species. Determination of four As species was investigated in urine, club soda and wine. Detection limits of 0.16 ng of As(III), 0.26 ng of As(v), 0.073 ng of dimethylarsinic acid (DMA) and 0.18 ng of methylarsonic acid (MMA) in wine were obtained. Sensitivity was further improved by using an He-Ar mixed gas ICP as the ionization source. However, the intensity of the ArCl+ interference was also increased using this plasma. Detection limits of 0.063 ng of As(III), 0.037 ng of As(v), 0.032 ng of DMA and 0.080 ng of MMA in club soda were achieved using the He-Ar plasma source. Similar limits of detection were found in urine and wine.

Determination of ephedrine compounds in nutritional supplements by cyclodextrin-modified capillary electrophoresis

Capillary electrophoresis was utilized for the separation, identification, and quantitation of ten stereoisomers in the ephedrine family. Chiral discrimination was accomplished through the use of hydroxypropyl-beta-cyclodextrin, and separation was enhanced at pH 2 in the presence of tetramethylammonium chloride and sodium dodecyl sulfate. Calibration plots of the ephedrines were linear over the range 4-100 micrograms/ml. This method was used in the analysis of nutritional supplements that contain Ma Huang, a Chinese herbal preparation that is made from plants in the genus Ephedra.

Quantitation of gentamicin sulfate in injectable solutions by capillary electrophoresis

The results presented in this communication establish the use of capillary electrophoresis as a tool in the analysis of injectable solutions containing the antibiotic complex gentamicin sulfate. The utilization of a borate buffer leads to the separation of the individual components and their visualization by direct UV detection. This rapid and straightforward procedure yields qualitative and quantitative information simultaneously, and could be utilized as an alternative to the multiple assays required by current US Pharmacopoeia protocols.

Chemical profiling of pharmaceuticals by capillary electrophoresis in the determination of drug origin

Capillary electrophoresis has been utilized to detect trace components in bulk pharmaceutical products, with emphasis on the identification of differences among manufacturers that can be used for source verification in suspect/counterfeit cases. Micellar electrokinetic capillary chromatography with sodium dodecyl sulfate was used in the analyses of beta-lactam antibiotics. The aminoglycoside clindamycin phosphate and the macrolide erythromycin stearate were analyzed using borate buffers with direct UV detection. Methyl-beta-cyclodextrin was used as a buffer additive in the erythromycin studies. Determination of product potency using peak area ratios has been demonstrated for ampicillin and clindamycin phosphate.

Practical applications of element-specific detection by inductively coupled plasma atomic emission spectroscopy and inductively coupled plasma mass spectrometry to ion chromatography of foods

Three practical examples are presented to demonstrate the utility of element-selective detection for ion chromatography (IC). The determination of As species in a liquid health food supplement by IC with inductively coupled plasma atomic emission spectroscopy (IC-ICP-AES) is shown to confirm results obtained for total As. IC-ICP-AES is also used to investigate the identity of an unknown peak in a sample of shrimp commercially treated with tripolyphosphate. Finally, results are presented for the determination of residual bromate in baked goods by IC with inductively coupled plasma mass spectrometry detection.

Forensic investigation of gentamicin sulfates by anion-exchange ion chromatography with pulsed electrochemical detection

Many methods exist for the separation of gentamicin C complex components, C1, C1a, C2 and C2a. In an investigation of possible counterfeit suppliers of gentamicin sulfate, a new method utilized high-pH anion-exchange separation on a carbohydrate column, with pulsed electrochemical detection on a gold electrode. Component ratios and the presence and/or absence of additional peaks were used to link or dissociate forensic samples.

Simultaneous analysis of hepatotoxic pyrrolizidine alkaloids and N-oxides in comfrey root by LC-ion trap mass spectrometry

The purpose of the current study was to develop a LC-MS(n) method for the analysis of pyrrolizidine alkaloids (PAs) in comfrey. Published data presents an extensive list of PAs and their N-oxides present in comfrey. However, standards are not commercially available for any of the PAs typically present in comfrey. Those PAs that are not stereoisomers were readily resolved on a C(18) column using a water-acetonitrile gradient as the mobile phase. The use of a selective technique, LC-MS/MS, allowed us to identify groups of PAs and their N-oxides, as well as identify the number of PAs present in each group, including those that were not completely resolved chromatographically.

Detection of counterfeit and relabeled infant formulas by high-pH anion-exchange chromatography-pulsed amperometric detection for the determination of sugar profiles.

High pH anion-exchange separation with pulsed amperometric detection (HPAE-PAD) is used to characterize various milk-based, soy-based, and protein hydrolysate infant formulas based on carbohydrate profiles. Counterfeit and relabeled formulas are compared to authentics. Figures of merit are shown for glucose, fructose, lactose, sucrose, and maltose.

Characterization of a Helium/Argon Mixed-Gas Plasma for the Detection of Iodine by Inductively Coupled Plasma Optical Emission Spectroscopy

A He/Ar mixed-gas plasma has been investigated as an optical emission source for the determination of iodine at 2063 Angstroms. The effects of adding varying amounts of He to an argon plasma were studied. Optimal conditions were found with a total plasma composition of 34% helium. The auxiliary gas was 100% argon, whereas the carrier gas and the coolant gas were composed of 88% and 35% He, respectively. The mixed-gas plasma reduced the detection limit for iodine to 0.4 ppm, a sevenfold improvement over the detection limit obtained with a 100% Ar plasma. At the optimum conditions for iodine, detection limits for most other elements studied improved or stayed the same.

Metal Content of Stack Emissions, Coal and Fly Ash from Some Eastern and Western Power Plants in the U.S.A. as Obtained By ICP-AES

Abstract The metal profiles characterizing stack emissions, fly ashes and coals of three coal-fired power plants in the United States using one high-sulfur Eastern and two low-sulfur Western coals were obtained by quantitating 21 elements via inductively coupled plasma atomic emission spectroscopy. The stack emissions were collected with a modified sampling train approved by the U.S. EPA. Aluminum, calcium, iron, sodium, potassium and magnesium predominated in all the samples and the emission was greatest from the high sulfur coal. Silicon could not be accurately quantitated because of the digestion procedure used. Volatile elements were lead, zinc, beryllium and molybdenum. Chemical speciation in stack emissions was shown to be important by atypical collection for Pb, Bi, Be, Na, Cu and Zn in the three impingers of the sampling train.