Tiebang Wang

Direct determination of metals in organics by inductively coupled plasma atomic emission spectrometry in aqueous matrices

A simple method for the simultaneous determination of up to 21 elements in organic matrices is proposed. Organic samples are simply dispersed in concentrated nitric acid by sonication, and the resulting emulsions/suspensions are directly aspirated into an inductively coupled plasma atomic emission spectrometer (ICP-AES) calibrated with aqueous standards for analysis. Proof of concept was provided by the excellent recoveries for the analysis of a 21-element metallo-organic standard. In addition, the results obtained using this method for a waste oil sample compared favorably with those from a method that utilized microwave digestion for sample preparation. Comparable results were also obtained by dilution in an organic solvent followed by ICP-AES analysis with an ultrasonic nebulizer equipped with a membrane desolvator. Furthermore, the viability and validity of this method were confirmed by the analysis of the National Institute of Standards and Technology standard reference material 1084a Wear-Metals in Lubricating Oil. Spike recoveries ranged from 83 to 105% and the limits of quantitation were 6 microg g(-1) or less for all the elements analyzed.

High-throughput metal screening in pharmaceutical samples by ICP-MS with automated flow injection using a modified HPLC configuration.

There is growing pressure in pharmaceutical research and development to increase sample throughput and turnaround time for metal analysis. This need is especially pronounced when a large number of samples must be analyzed to support rapid remediation of metal contamination problems. In this study we describe the utilization of an HPLC-ICP-MS system in automated flow injection (FI) mode for the rapid assessment of metal (palladium, rhodium, chromium, etc.) concentration. The system consists of an HPLC standard or well-plate autosampler, a novel interface (consisting of a desolvating unit, an eluent splitter and a built-in peristaltic pump) and the ICP-MS instrument. This configuration ensures a fully automatic process and is well suited for standardization. The interface can be easily switched to adapt to HPLC eluents or FI introduction for speciation or flow injection analysis. The use of the well-plate autosampler decreases sample injection cycle time and adds flexibility to the system by allowing direct analysis with little or no sample preparation. The FI-ICP-MS method provides a means for high-throughput metal screening with unprecedented speed. Other advantages of the method include automatic analysis of microliter sample volumes, fast inter-sample washout and reduced reagent consumption.

Determination of tungsten in bulk drug substance and intermediates by ICP-AES and ICP-MS.

A quick and sensitive method has been developed and validated for the determination of tungsten in bulk drug substance and intermediates using either Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES) or Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Sample preparation is by direct dissolution with a 80:20 (v/v) concentrated nitric acid:deionized water mixture and avoids labor intensive and potentially hazardous digestion techniques. Excellent agreement was found between ICP-AES and ICP-MS results and between Merck results and Microwave Induced Plasma Mass Spectrometry (MIP-MS) results provided by an independent raw material vendor.

Determination of palladium by graphite furnace atomic absorption spectroscopy without matrix matching

A graphite furnace atomic absorption spectroscopy method for the analysis of the palladium (Pd) content in bulk pharmaceutical drug substances and their intermediates prepared in aqueous solutions is extended to samples prepared in acetonitrile (ACN) and ACN-water mixtures as well to samples prepared in dimethyl sulfoxide (DMSO) and DMSO-water mixtures. The Pd content in samples solubilized in these solvents can be accurately determined with calibration established with standards prepared in aqueous solutions without matrix matching or using the method of standard additions. The validity of this method is demonstrated by spike recovery studies and by the agreement with results for the same samples prepared in these solvents, in concentrated nitric acid, and prepared by a microwave digestion system.

Isolation and analysis of trace level of silicone oil in pharmaceutical bulk drug substance by ICP-AES

In order to evaluate the extent of silicone oil contamination in a drug substance derived from processing equipment, a novel extraction method was developed which uses a mixture of polar and non-polar solvents (toluene/acetonitrile). Unlike the majority of silicone oil extraction methods in the literature that yield very low recoveries, this procedure proved able to completely recover the silicone oil from this compound. The recovered silicone oil was rediluted in isopropanol alcohol (IPA)/toluene mixture and subsequently analyzed by an inductively coupled plasma atomic emission spectrometer (ICP-AES) coupled to an ultrasonic nebulizer (USN).

Study of hypochlorite-specific enhancement in ICP-AES and ICP-MS

Severe chlorine signal enhancement in ICP-AES (by a factor of 2.6 to 3) and ICP-MS (by a factor of about 2) was found in the determination of Cl in hypochlorite (ClO−) but not in the determination of Cl in four other chlorine-containing species (Cl−, ClO2−, ClO3−, and ClO4−). A near linear correlation between the extent of the enhancement and the hypochlorite concentration was established, and the enhancement can only be removed by converting hypochlorite into other chlorine-containing species.