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.

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.

Development of an immunoaffinity solid phase microextraction method for the identification of penicillin binding protein 2a.

Methicillin resistant Staphylococcus aureus (MRSA) is a bacterium that is resistant to many antibiotics. Resistance to methicillin is related to production of penicillin binding protein 2a (PBP2a). The currently presented research involves the development of antibody-linked immunoaffinity solid phase microextraction (SPME) sorbents characterized from several aspects that can identify protein PBP2a. The on-sorbent binding constant Kd of monoclonal anti-PBP2a antibody for its antigen protein PBP2a was determined to be 4×10(-10) M. This value was obtained on the basis of the binding curve determined by selective extraction of its antigen PBP2a at different concentrations. The concentration of PBP2a captured by immunoaffinity sorbents was as low as 10ng/mL; lower concentrations could not be tested due to the sensitivity limitation of the LC-MS/MS system available. Surface density was estimated at 59 ng antibody/cm(2). To reduce non-specific binding, especially when the antigen is a protein, bovine serum albumin (BSA) was used to pretreat surfaces. The established immunoaffinity platform technology is expected to provide insights into the development of a practical, specific, sensitive and accurate assay for in vitro and in vivo diagnostics of MRSA.

A new strategy to eliminate sample mixing during in-tube solid phase microextraction.

During in-tube solid phase microextraction, sample mixing with mobile phase contained in the autosampler tubing during extraction may result in some amount of sample becoming entrained in the mobile phase rather than returning to the sample vial or being directed to waste after extraction. In cases where target analytes have relatively low affinity for the sorbent on the wall of the capillary, mixing can impact data quality. Where the sample contains components that may interfere with either the separation (e.g. proteins) or detection (e.g. ions with MS detection), additional difficulties can arise. In the current research, the magnitude of the sample mixing effect was illustrated by analyzing ranitidine and a series of polycyclic aromatic hydrocarbons (PAH). The sample volume equivalent of mixing was calculated as 37 µL for ranitidine and 20 µL for PAHs using the same inner diameter of capillary. To address this issue, a novel approach involving adding a switching valve located between the metering pump and the capillary was developed. Capillary flush conditions, draw/eject speed and extraction time were optimized for ranitidine with the result that in the final method, no mixing of sample with mobile phase was apparent in the detected amounts. To provide information on a compound class with intermediate polarity, two -blockers were also extracted using the optimized washing conditions respectively. The results indicated that the issue of sample mixing had been resolved for these as well. Finally, in-tube SPME calibration of these three analyte classes was shown to be highly linear, providing further indication that sample mixing was not impacting data quality. Available literature on the subject was surveyed, and a discussion on the rational selection of conditions to guide method development was also provided.

Development and evaluation of a new in vivo solid-phase microextraction sampler.

The use of solid-phase microextraction (SPME) as a nonlethal technique for in vivo sampling of pharmaceutical residue in fish tissue has been documented in the literature. However, there is need to improve its simplicity and robustness for wider applications in the laboratory and field. The objective of this research is to develop and improve the SPME device for sampling of pharmaceuticals in fish tissue. The practical application of the new device was demonstrated in the field where some wild fish (Esox masquinongy) were caught in the river and sampled by the device. The samples were analyzed using LC coupled with MS/MS (LC-MS/MS). The new in vivo SPME device with a PDMS extraction phase (sorbent) was demonstrated to a robust tool by both experts and nonexpert of the method and it is simpler than the traditional device. The detection limit of the method in gel and fish tissue was 0.01-0.26 ng/g. The interday reproducibility in gel and fish homogenized fish tissue was 8-16% RSD. This study demonstrates that the new device will provide a platform or opportunity for rapid sampling of carbamazepine, diazepam, and nordiazepam in fish muscle with acceptable precision.

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.

Theory and validation of solid-phase microextraction and needle trap devices for aerosol sample.

Previous aerosol studies utilizing solid-phase microextraction (SPME) predominantly focused on volatile and semivolatile compounds in the gaseous phase. Difficulties were associated with quantitative analysis of these compounds when they were associated with atmospheric particles. The present study combines SPME technology with that of carboxen packed needles (needle trap, NT) for analysis of gaseous and particle-bound compounds in atmospheric samples. The NT device is constructed as a micro trap by placing some small sorbents in a needle. Aerosol samples are collected by drawing air through the NT device with a pump. The trapped components contain both gaseous chemical compounds as well as particulate matter present in the sample. The total concentration of analytes in an aerosol sample can be obtained on the basis of the exhaustive sampling mode of the NT device. Direct SPME is simultaneously used to determine gaseous compound in the aerosol sample. As a result, the SPME and NT devices, when used together, can provide a complete solution to highly efficient and accurate aerosol studies. The theoretical considerations of SPME and NT devices for aerosol sampling are validated by sampling seasalt aerosol, barbecue, and cigarette smoke. The concentrations of PAHs in the different phases of the samples are few ng/L. Result analysis shows that SPME and the NT device demonstrate several important advantages such as simplicity, convenience, and low costs under laboratory and on-site field sampling conditions.

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.

Protocol for solid-phase microextraction method development.

Solid-phase microextraction (SPME) is a sample preparation method developed to solve some of the analytical challenges of sample preparation as well as sample introduction and integration of different analytical steps into one system. Since its development, the utilization of SPME has addressed the need to facilitate rapid sample preparation and integrate sampling, extraction, concentration and sample introduction to an analytical instrument into one solvent-free step. This achievement resulted in fast adoption of the technique in many fields of analytical chemistry and successful hyphenation to continuously developing sophisticated separation and detection systems. However, the facilitation of high-quality analytical methods in combination with SPME requires optimization of the parameters that affect the extraction efficiency of this sample preparation method. Therefore, the objective of the current protocol is to provide a detailed sequence of SPME optimization steps that can be applied toward development of SPME methods for a wide range of analytical applications.

Application of membrane extraction with sorbent interface for breath analysis.

The detection of volatile organic compounds (VOCs) in human breath may be useful for routine clinical diagnosis of several diseases in a non-invasive manner. Traditional methods of breath analysis have some technical limitations. Membrane extraction with a sorbent interface (MESI), however, has many advantages over current methods, including good selectivity and sensitivity, and is well suited for breath analysis.The aim of this project was to develop a simple and reproducible sampling device and method based on the MESI system for breath analysis. The feasibility and validity of the MESI system was tested with real human breath samples. The use of breath CO(2) as an internal standard for the analysis of breath VOCs is an effective method to solve the difficulties associated with variations in the target analyte concentrations in a sample, which are attributed to mass losses and different breathing patterns of different subjects. In this study, the concentration of breath acetone was successfully expressed normalized to CO(2) as in the alveolar air. Breath acetone of healthy males and females profiled at different times of the day was plotted using the MESI system, and results are consistent with literature. This technique can be used for monitoring breath acetone concentrations of diabetic patients and for applications with other biomarker monitoring.

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.

Neighborhood crime and self-care: risks for aggression and lower academic performance.

This longitudinal study evaluated associations among official rates of neighborhood crime, academic performance, and aggression in a sample of 581 children in 1st-3rd grade (6.3-10.6 years old). It was hypothesized that the influence of crime depends on children's unsupervised exposure to the neighborhood context through self-care. Average weekly hours in self-care were trichotomized into low (0-3), moderate (4-9), and high (10-15). Moderate and high amounts of self-care were linked to increased aggression and decreased academic performance for children from high-crime areas (11,230 crimes per 100,000 persons) but not average-crime areas, when the authors controlled for neighborhood, family, and child covariates. In high-crime areas, academic outcomes were more favorable when self-care occurred in combination with after-school program participation.

Determination of antibiotic drug concentrations in circulating human blood by means of solid phase micro-extraction.

BACKGROUND: Promising results in animals have shown the diagnostic potential of polypyrrole coated SPME fibres introduced directly into the blood stream. This study was intended to extend this technique to a clinically relevant antibiotic drug under close to physiological conditions in human blood. METHODS: An artificial vein system was built up from heart and lung machine components. Determination of Linezolid (0-15 mug/mL) was performed by SPME from the flowing system ("online", flow velocities 2-50 cm/s), from blood withdrawn from the system ("offline") and by means of a SPE/HPLC method. SPME was done using new fibres ("new") for each analysis, and in the way that one fibre was reused ("re") for one series of measurements. RESULTS: Drug SPME did not depend on blood flow velocities. Linear regression of data (concentration vs. amount extracted) yielded R(2)=0.998 for SPE/HPLC, R(2)=0.955 for SPME(online_new), 0.929 for SPME(online_re), 0.929 SPME(offline_new), 0.973 for SPME(offline_re), RSD were 52% (SPME(online_new)), 10% (SPME(online_re)), 47% (SPME(offline_new)), 18% (SPME(offline_re)), 8% (SPE/HPLC). CONCLUSIONS: In-vein SPME has the potential to minimize blood requirement for diagnostic purposes and to speed up analysis of clinically relevant drugs, if inter-fibre variation can be reduced through standardized manufacturing.

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.

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.

Implementation of the Child Care and Development Block Grant: a research synthesis.

The Child Care and Development Block Grant (CCDBG) is the largest source of state and federal child care assistance. Between 1996-2004, the number of reports on state implementation of the CCDBG soared. Using the matrix method, this article synthesizes 39 reports from public and private entities on how states differed in the use of CCDBG funds. We found considerable variation among states with regard to populations served, financing of child care through CCDBG and TANF (Temporary Assistance to Needy Families), administration of the CCDBG, and use of its quality set-asides. This issue is of prime importance to nurses who work with low-income families with children, especially because quality, accessibility and affordability of child care affects a child's emotional, social, cognitive, and physical development. The CCDBG reauthorization and annual appropriations are currently on the congressional agenda and warrant nurse's input for ongoing sustainability and support. Recommendations for policy and future research are included.

An ecological analysis of after-school program participation and the development of academic performance and motivational attributes for disadvantaged children.

This longitudinal study evaluated after-school program (ASP) participation and the development of academic performance (school grades, reading achievement) and teacher-rated motivational attributes (expectancy of success, effectance motivation) over a school year. Participants were 599 boys and girls (6.3 to 10.6 years) from an urban, disadvantaged city in the United States. An ecological analysis of after-school arrangements identified 4 patterns of care: ASP care, parent care, combined parent/self-sibling care, and combined other-adult/self-sibling care. Aspects of academic performance and motivational attributes were significantly higher (p<.05) at the end of the school year for children in ASP care compared with those in the 3 alternative patterns of care. Differences were marked for children rated as highly engaged in ASP activities.

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.