Quantitative Analysis of Polycyclic Aromatic Hydrocarbons at Part Per Billion Levels in Fish Oil by Headspace Solid-Phase Microextraction and Gas Chromatography-Mass Spectrometry (HS-SPME-GC-MS).

Headspace solid-phase microextraction (HS-SPME) was used in combination with gas chromatography-mass spectrometry (GC-MS) for the analysis of polycyclic aromatic hydrocarbons (PAH) at part per billion levels in fish oil samples collected from menhaden fish. The method was initially developed using fish oil from capsules spiked with a standard PAH mixture. The final HS-SPME-GC-MS method presented a linear range from 3 to 1,500 ng/g, with precision for most analytes <10% relative standard deviation. The limits of detection varied from 1 to 7 ng/g depending on the analyte. Real sample analysis was done on menhaden fish oil extracted from fish collected off the coasts of New Jersey and Louisiana. Naphthalene, fluorene, fluoranthene, pyrene, anthracene were detected at low levels of 70-180 ng/g in the real samples. The concentrations of PAHs detected in the real samples were well below established levels of concern for PAHs in finfish.

"Retention projection" enables reliable use of shared gas chromatographic retention data across laboratories, instruments, and methods.

Gas chromatography/mass spectrometry (GC/MS) is a primary tool used to identify compounds in complex samples. Both mass spectra and GC retention times are matched to those of standards; however, it is often impractical to have standards on hand for every compound of interest, so we must rely on shared databases of MS data and GC retention information. Unfortunately, retention databases (e.g., linear retention index libraries) are experimentally restrictive, notoriously unreliable, and strongly instrument dependent, relegating GC retention information to a minor, often negligible role in compound identification despite its potential power. A new methodology called "retention projection" has great potential to overcome the limitations of shared chromatographic databases. In this work, we tested the reliability of the methodology in five independent laboratories. We found that, even when each lab ran nominally the same method, the methodology was 3-fold more accurate than retention indexing because it properly accounted for unintentional differences between the GC/MS systems. When the laboratories used different methods of their own choosing, retention projections were 4- to 165-fold more accurate. More importantly, the distribution of error in the retention projections was predictable across different methods and laboratories, thus enabling automatic calculation of retention time tolerance windows. Tolerance windows at 99% confidence were generally narrower than those widely used even when physical standards are on hand to measure their retention. With its high accuracy and reliability, the new retention projection methodology makes GC retention a reliable, precise tool for compound identification, even when standards are not available to the user.

Determination of steroids, caffeine and methylparaben in water using solid phase microextraction-comprehensive two dimensional gas chromatography-time of flight mass spectrometry.

Analysis of several emerging contaminants (steroids, caffeine and methylparaben) in water using automated solid-phase microextraction with comprehensive two dimensional gas chromatography coupled to time of flight mass spectrometry (SPME-GCxGC-ToF/MS) is presented. Experimental design was used to determine the best SPME extraction conditions and the steroids were not derivatized prior to injection. SPME-GCxGC-ToF/MS provided linear ranges from 0.6 to 1200µgL(-1) and limits of detection and quantitation from 0.02 to 100µgL(-1). A series of river water samples obtained locally were subjected to analysis. SPME-GCxGC-ToF/MS is readily automated, straightforward and competitive with other methods for low level analysis of emerging contaminants.

Analysis of Salvinorin A in plants, water, and urine using solid-phase microextraction-comprehensive two-dimensional gas chromatography-time of flight mass spectrometry.

Salvinorin A, a psychoactive hallucinogen, and related compounds, were analyzed in plants, water, and urine using liquid-liquid extraction (LLE), solid-phase microextraction (SPME) and comprehensive two-dimensional gas chromatography-time of flight mass spectrometry (GC×GC-ToFMS). A semi-qualitative study of the extraction of Salvinorin A and analogs from Salvia divinorum plants by LLE showed ppb levels of Salvinorin A and several analogs in the leaves and stems of S. divinorum plants, much lower than expected. Quantitative analysis of Salvinorin A spiked into water and urine showed much better figures of merit for SPME than LLE, with limit of detection of about 5 ng/mL, linear range from 8 to 500 ng/mL and precision about ±10% for the SPME-based analyses using external standard quantitation. GC×GC-ToFMS was especially effective in separating the peaks of interest from matrix and chromatographic interferences.

Sample preparation for gas chromatography using solid-phase microextraction with derivatization.

The development of SPME over the past 20 years, and the more recent wide availability of automated SPME systems, has generated renewed interest in derivatization with gas chromatography for the analysis of highly polar or labile analytes. By using an SPME fiber as the extracting phase, the derivatization process is straightforward and readily automated. From anecdotal examination of the literature, it appears that the fiber may offer benefits over traditional liquid phase reactions in that control over the selectivity of the reaction for the desired product and fewer interfering byproducts may be more readily achieved. Nearly all authors have reported that SPME-based derivatization methods provide equivalent or superior analytical performance to their traditional counterparts. While attention to derivatization in general has waned among gas chromatographers, the advent of procedures in combination with SPME makes derivatization again attractive and worthy of consideration in analytical method development.

Stir-bar sorptive extraction and thermal desorption-ion mobility spectrometry for the determination of trinitrotoluene and l,3,5-trinitro-l,3,5-triazine in water samples.

Stir-bar sorptive extraction (SBSE) is interfaced to ion mobility spectrometry (IMS) for the rapid detection of trace analytes, with the explosives, trinitrotoluene (TNT) and l,3,5-trinitro-l,3,5-triazine (RDX) shown as examples. SBSE retains its inherent advantages as a sensitive, straightforward, solventless, and inexpensive method. Additionally, the new SBSE-IMS technique exhibits excellent sensitivity, has onsite field analysis capabilities and provides the potential to detect and quantitate analytes that are difficult to accomplish using gas chromatography (GC) or high-performance liquid chromatography (HPLC). The SBSE-IMS technique is shown to be an effective method for the low-level detection of TNT and RDX from water with method standard deviation of 8.6% for TNT and 6.6% for RDX. The short desorption time of 60 s and analysis time of less than 20 ms along with limits of detection of 0.1 ng/mL for TNT and 1.5 ng/mL for RDX and render the method potentially useful for trace analysis. Desorption profiles showing the kinetics of analyte transfer from the stir-bar into the IMS are shown and discussed; the SBSE-IMS configuration shows very rapid desorption from the stir-bar, with the analytes completely transferred in most cases, in under 1 min.

Determination of parabens in pharmaceutical formulations by solid-phase microextraction-ion mobility spectrometry.

Solid-phase microextraction (SPME) coupled with ion mobility spectrometry (IMS) was used for the detection and quantitation of 4-hydroxybenzoate preservatives, methylparaben, ethylparaben, propylparaben, and butylparaben, in commercial pharmaceutical products. For the first time, SPME-IMS is described for the simultaneous detection, separation, and quantitation of multiple analytes in complex matrixes. The parabens are extracted from the samples using SPME, and the analytes on the fiber are heated by the IMS desorber unit and vaporized into the drift tube. The four preservatives differing only by a methyl group were separated in less than 18 ms. The analytical procedure was optimized for fiber coating selection, extraction time, sample pH, sample volume, ionic strength, and IMS conditions. Separation characteristics such as resolution, theoretical plates, and drift times of the parabens were also evaluated based on the direct interfacing of SPME to IMS. The conditions were tested using six over-the-counter topical products containing various combinations of preservatives. Analysis of the samples by SPME-IMS using benzyl paraben as an internal standard yields good comparison to an HPLC method, thereby reinforcing the applicability of this technique as a method for routine analysis. Limits of detection were 10 ng/mL for methylparaben and ethylparaben and 5 ng/mL for propylparaben and butylparaben. Good linearity range and reproducibility of less than 8% were obtained.

Solid phase micro-extraction coupled with ion mobility spectrometry for the analysis of ephedrine in urine.

Quantitative solid phase micro-extraction (SPME) coupled with ion mobility spectrometry is demonstrated using the analysis of ephedrine in urine. Since its inception in the 1970's ion mobility spectrometry (IMS) has evolved into a useful technique for laboratories to detect explosives, chemical warfare agents, environment pollutants and, increasingly, for detecting drugs of abuse. Ephedrine is extracted directly from urine samples using SPME and the analyte on the fiber is heated by the IMS desorber unit and vaporized into the drift tube. The analytical procedure was optimized for fiber coating selection, extraction temperature, extraction time, sample pH, and analyte desorption temperature. The carryover effects, ion fragmentation characteristics, peak shapes, and drift times of ephedrine were also evaluated based on the direct interfacing of SPME to IMS. A limit of detection of 50 ng/mL of ephedrine in urine and a linear range of 3 orders of magnitude were obtained, showing that SPME-IMS compares well to other techniques for ephedrine and drug analysis presented in the literature.

Evaluation of the origins of the selectivity of polymers imprinted with a HIV protease inhibitor using infrared spectroscopy and high performance liquid chromatography.

This work investigates the origins of enantioselectivity of polymers imprinted with the HIV protease inhibitor, Indinavir. For the preparation of imprints of the drug, the critical interactions between the functional monomer, methacrylic acid, and Indinavir were characterized by infrared (IR) spectroscopy to explore the optimum functional monomer concentration for the polymerization. It was shown that a polymer with high selectivity and minimum non-selective binding for Indinavir was obtained when prepared with enough functional monomer to hydrogen bond with all of the functional groups of the drug without using an excess of monomer. This observation is explained in terms of a balance that is achieved in the monomer-template equilibrium during the polymerization that yields a polymer with highly selective sites and minimal non-selective sites. This paper further demonstrates that IR spectroscopy can be a valuable tool in the design and syntheses of molecular imprinted polymers.