Interlaboratory Comparison of Extractable Organofluorine Measurements in Groundwater and Eel (Anguilla rostrata): Recommendations for Methods Standardization.

Research on per- and polyfluoroalkyl substances (PFAS) frequently incorporates organofluorine measurements, particularly because they could support a class-based approach to regulation. However, standardized methods for organofluorine analysis in a broad suite of matrices are currently unavailable, including a method for extractable organofluorine (EOF) measured using combustion ion chromatography (CIC). Here, we report the results of an international interlaboratory comparison. Seven laboratories representing academia, government, and the private sector measured paired EOF and PFAS concentrations in groundwater and eel (Anguilla rostrata) from a site contaminated by aqueous film-forming foam. Among all laboratories, targeted PFAS could not explain all EOF in groundwater but accounted for most EOF in eel. EOF results from all laboratories for at least one replicate extract fell within one standard deviation of the interlaboratory mean for groundwater and five out of seven laboratories for eel. PFAS spike mixture recoveries for EOF measurements in groundwater and eel were close to the criterion (±30%) for standardized targeted PFAS methods. Instrumental operation of the CIC such as replicate sample injections was a major source of measurement uncertainty. Blank contamination and incomplete inorganic fluorine removal may introduce additional uncertainties. To elucidate the presence of unknown organofluorine using paired EOF and PFAS measurements, we recommend that analysts carefully consider confounding methodological uncertainties such as differences in precision between measurements, data processing steps such as blank subtraction and replicate analyses, and the relative recoveries of PFAS and other fluorine compounds.

Strategies for interfacing solid-phase microextraction with liquid chromatography.

Solid-phase microextraction (SPME) techniques are equally applicable to both volatile and non-volatile analytes, but the progress in applications to gas-phase separations has outpaced that of liquid-phase separations. The interfacing of SPME to gas chromatographic equipment has been straight-forward, requiring little modification of existing equipment. The requirement of solvent desorption for non-volatile or thermally labile analytes has, however, proven challenging for interfacing SPME with liquid-phase separations. Numerous options to achieve this have been described in the literature over the past decade, with applications in several different areas of analysis. To date, no single strategy or interface device design has proven optimal. During method development analysts must select the most appropriate interfacing technique among the options available. Out of these options three general strategies have emerged: (1) use of a manual injection interface tee; (2) in-tube SPME; and (3) off-line desorption followed by conventional liquid injection. In addition, there has been interest in coupling SPME directly to electrospray ionisation and matrix-assisted laser desorption ionisation (MALDI) for mass spectrometry. Several examples of each of these strategies are reviewed here, and an overview of their use and application is presented.

A study of the performance characteristics of immunoaffinity solid phase microextraction probes for extraction of a range of benzodiazepines.

Immunoaffinity solid phase microextraction (SPME) probes have been developed with antibodies specific for the benzodiazepine class of drugs, covalently immobilized to glass rods. This involved both purification of the polyclonal antibodies to isolate the drug-specific fraction, and optimization of the immobilization procedure. Such probes have been used previously for the extraction of 7-aminoflunitrazepam. This article presents a comprehensive study of their performance and characteristics beyond that described previously, and an evaluation of their application to additional benzodiazepines. The influence of non-specific drug binding (nsb) was determined, with the result that nsb was found to be insignificant for the probes when used in their dynamic range. Immobilized antibodies had specific affinities in the range of 10(9)-10(10)M(-1). Cross-reactivity was evaluated both for a range of benzodiazepines as well as a structurally unrelated molecule (erythromycin). For analysis of benzodiazepines individually or in the presence of erythromycin, limits of detection were 0.001-0.015 ng/mL depending on the antibody, and the dynamic range (based on 80-90% antigenic site occupancy) extended to 0.2-2 ng/mL.

Inter-laboratory validation of a thin film microextraction technique for determination of pesticides in surface water samples.

The primary goal of the present study is the inter-laboratory evaluation of a thin film microextraction (TFME) technique to be used as an alternative approach to liquid-liquid extraction (LLE). Polydimethylsiloxane/divinylbenzene (PDMS/DVB) and PDMS/DVB-carbon mesh supported membranes were used for the extraction of 23 targeted pesticides, while a thermal desorption unit (TDU) was employed to transfer these analytes to a GC/MS instrument for separation and detection. After optimization of the most critical parameters, both membranes were capable of achieving limits of detection (LOD) in the low ng L-1 range while demonstrating excellent robustness, withstanding up to 100 extractions/desorption cycles. Furthermore, limits of quantification (LOQ) between 0.025 and 0.50 µg L-1 were achieved for the 23 compounds selected from several classes of pesticides with a wide range of polarities. A wide linear range of 0.025-10.0 µg L-1 with strong correlation to response (R2 > 0.99) was attained for most of the studied analytes. Both membranes showed good accuracy and repeatability at three levels of concentration. Moreover, the method was also validated through blind split analyses of 18 surface water samples, collected within 3 months, using TFME at the University of Waterloo and LLE at Maxxam Analytics (Mississauga, ON) which is an accredited commercial analytical laboratory. Good agreement between the two methods was achieved with accuracy values ranging from 70 to 130%, for the majority of analytes in the samples collected. At the concentration levels investigated, 90% of the analytes were quantifiable by TFME, whereas only 53% of the compounds were reportable using the LLE method particularly at concentrations lower than 1 µg L-1. The comparison of TFME and LLE from several analytical aspects demonstrated that the novel TFME method gave similar accuracy to LLE, while providing additional advantages including higher sensitivity, lower sample volume, thus reduced waste production, and faster analytical throughput. Given the sensitivity, simplicity, low cost, accuracy, greenness and relatively fast procedure of TFME, it shows great potential for adoption in analytical laboratories as an alternative to LLE.

In vivo solid-phase microextraction for monitoring intravenous concentrations of drugs and metabolites.

This protocol for in vivo solid-phase microextraction (SPME) can be used to monitor and quantify intravenous concentrations of drugs and metabolites without the need to withdraw a blood sample for analysis. The SPME probe is inserted directly into a peripheral vein of a living animal through a standard medical catheter, and extraction occurs typically over 2-5 min. After extraction, the analytes are removed from the sorbent and analyzed by, for example, liquid chromatography-tandem mass spectrometry. It has been validated in comparison with conventional blood analysis, and we describe here the in vitro experiments typically conducted during method development. The new-generation biocompatible SPME probes are designed specifically for extraction of semi-volatiles and nonvolatiles directly from aqueous samples and can be steam sterilized. Sorbents are coated on fine-gauge surgical steel wire (200-µm diameter), which is more rugged and biocompatible than conventional fibers (100-µm fused silica fiber). They incorporate a binding agent that resists fouling by the biological matrix and does not cause an immune response in the experimental animal. The sorbents used (coating thickness of ∼50 µm) are selected for their affinity for the types of small molecules of interest. The procedure is illustrated by the analysis of benzodiazepines with polypyrrole-coated wires inserted into peripheral blood vessels of beagles, although it can be adapted for use in smaller animals. The in vivo sampling can require as little as 1 min, in which case the entire procedure from sampling to instrumental analysis can take as little as 30 min.

Fundamentals and applications of needle trap devices: a critical review.

The needle trap device (NTD) is an extraction trap that contains a sorbent inside a small needle, through which fluid can be actively drawn into and out of by a gas-tight syringe or pump, or analytes can be introduced passively to the trap by diffusion. The needle trap (NT) is a potentially solventless sampling technique/sample preparation and introduction device. Both fluid-borne analytes and particles can be trapped inside the needle and then adsorbed analytes are desorbed in an inlet of analytical instrument and introduced for identification and quantification. The fluid may be either gaseous or liquid. The objectives of this critical review are to summarize the theory of the sampling process for both active and passive time-average extraction modes in addition to outlining the evolution of the technology and main applications.

Determination of malondialdehyde in human plasma by fully automated solid phase analytical derivatization.

Analytical derivatization (AD) increases the sensitivity of analysis by one to three orders of magnitude, stabilizes labile analytes and converts them into readily extractable products. Using a variant of this technique, we applied solid phase analytical derivatization (SPAD) to fully automate extraction, derivatization and liquid chromatography. The resulting device (AutoSPAD) determined malonyldialdehyde (MDA) from biological fluids. This biomarker of oxidative stress is highly water-soluble (500 g/L at pH 7), chemically labile and lacks any functionality that enables detection at high sensitivity. AutoSPAD utilizes column-switching technology to load DANSYL hydrazine onto the solid phase, pass the biological sample over the resulting reactor bed for derivatization on the surface to form a hydrophobic derivative suitable for increasing sensitivity of any other LC technique including LC-MS/MS. The hydrophobic solid phase retains the derivative during washing steps, following which AutoSPAD transfers the derivatized extract to the analytical column for separation and detection by fluorescence. In plasma, however, MDA exists both in free form and covalently bound to protein. Measuring MDA from plasma, therefore, required identification of appropriate protein precipitation and hydrolysis conditions. Under these conditions, the DANSYL derivative formed at only one aldehydic position but did not cyclize as reported for other reactions between hydrazine reagents and MDA. The calibration curve using approximately 7 microL of plasma was linear (r(2)=0.999) in the physiological range (0.1-3 microg/mL) and the relative standard deviation of replicate determinations at 1 microg/mL was less than 5%.

Automated derivatization and analysis of malondialdehyde using column switching sample preparation HPLC with fluorescence detection.

Analyte derivatization is advantageous for the analysis of malondialdehyde (MDA) as a biomarker of oxidative stress in biological samples. Conventionally, however, derivatization is time consuming, error-prone and has limited options for automation. We have addressed these challenges for the solid phase analytical derivatization of MDA from small volume tissue homogenate samples. A manual derivatization method was first developed using Amberlite XAD-2 (12 mg) as the solid phase. Subsequently an automated column switching process was developed that provided simultaneous derivatization and extraction of the MDA-DH hydrazone product on a cartridge packed with XAD-2, followed by quantitative elution of the product to an analytical LC column (Waters NovoPak C18, 3.9 x 150 mm). The LOD was 0.02 microg/mL and recovery was quantitative. The method was linear (r(2) >0.999) with precision < 5% from the LOQ (0.06 microg/mL) to at least 35 microg/mL. The method was successfully applied to the analysis of small volume (30 microL) mouse tissue homogenate samples. Endogenous levels of MDA in the tissues ranged from 20 to 40 nmol/g tissue (ca. 0.1-0.2 microg/mL homogenate). Compared to conventional MDA analyses, the current method has advantages in automation, selectivity, precision and sensitivity for analysis from very small sample volumes.

In vivo study of triazine herbicides in plants by SPME.

The use of SPME for in vivo monitoring of herbicide levels in plant tissues is evaluated. Fibers are exposed to the plant tissue with the aid of buffer located at the fiber/tissue interface region. Following this extraction period the extracted amount is estimated by solvent desorption and LC-MS-MS.