Intra-workday fluctuations of airborne contaminant concentration and the time-weighted average.

Air contaminant concentrations vary between and within workdays and are often measured across a workday by passing a known air volume through a collection device. Laboratory analysis determines the contaminant mass trapped, providing a time-weighted average air concentration (CTWA). This approach was driven by the best technologies available as exposure measurement processes developed and accuracy and measurement precision were sought. However, all integrated concentration•time (C•t) values determining CTWA are equally weighted in assessing exposures, intra-workday concentration variability is unknown, and results are available days later. At times inappropriately, an occupational exposure limit (OEL) expressed as a CTWA also requires equal weighting of all C•t values across an exposure period following concepts of Haber's law. Continuous monitoring (real-time detection) informs both the CTWA and the variability of C during sampling, which are needed for stressors where a ceiling or peak OEL exists, for dangerous exposures to permanent gas-type contaminants, and for immediately dangerous to life or health (IDLH) conditions. Selective and accurate real-time detection instruments are not available for all air contaminants, but exposure magnitude information may be provided. The large amounts of data from continuous monitoring and the ability to correlate exposure maxima to specific tasks are also important. An exposure assessment role exists for selective and nonselective monitors, and in some cases, similar accuracy and precision are provided compared to laboratory analyses. Continuous monitoring may be of value when the alternative is the collection of a few CTWA data points. Digitized personal monitor data can support the automation of some exposure control decisions or allow such decisions to be made by people in near real-time. The emerging Internet of Things (IoT) offers opportunities to integrate digital exposure data into decision-making to increase both efficiency and safety. The perceived and real uncertainty associated with real-time exposure assessments may be lessened with work to rule out the presence of know interferents and confirm the presence of target analytes.

Mixed-Valent Cyanoplatinates Featuring Neptunyl-Neptunyl Cation-Cation Interactions.

The tetracyanoplatinate ligand was employed in synthesizing the first neptunyl cyanoplatinate complexes. Results indicate in situ oxidation of Pt(II) by Np(V/VI) to form mixed-valent Pt-Pt stacked columnar chains linked by cation-cation interaction induced chains of Np(V) polyhedra into a two-dimensional sheet structure. The Pt-Pt stacking distances of 3.04-3.05 Å are the longest reported columnar platinophilic interactions among mixed-valent tetracyanoplatinate structures. These complexes further illustrate the marked chemical differences and structural diversity of solid-state Np(V) coordination complexes with regard to Np(VI) and U(VI).

Sensor-triggered sampling to determine instantaneous airborne vapor exposure concentrations.

It is difficult to measure transient airborne exposure peaks by means of integrated sampling for organic chemical vapors, even with very short-duration sampling. Selection of an appropriate time to measure an exposure peak through integrated sampling is problematic, and short-duration time-weighted average (TWA) values obtained with integrated sampling are not likely to accurately determine actual peak concentrations attained when concentrations fluctuate rapidly. Laboratory analysis for integrated exposure samples is preferred from a certainty standpoint over results derived in the field from a sensor, as a sensor user typically must overcome specificity issues and a number of potential interfering factors to obtain similarly reliable data. However, sensors are currently needed to measure intra-exposure period concentration variations (i.e., exposure peaks). In this article, the digitized signal from a photoionization detector (PID) sensor triggered collection of whole-air samples when toluene or trichloroethylene vapors attained pre-determined levels in a laboratory atmosphere generation system. Analysis by gas chromatography-mass spectrometry of whole-air samples (with both 37 and 80% relative humidity) collected using the triggering mechanism with rapidly increasing vapor concentrations showed good agreement with the triggering set point values. Whole-air samples (80% relative humidity) in canisters demonstrated acceptable 17-day storage recoveries, and acceptable precision and bias were obtained. The ability to determine exceedance of a ceiling or peak exposure standard by laboratory analysis of an instantaneously collected sample, and to simultaneously provide a calibration point to verify the correct operation of a sensor was demonstrated. This latter detail may increase the confidence in reliability of sensor data obtained across an entire exposure period.

Methemoglobinemia resulting from exposure in a confined space: Exothermic self-polymerization of 4,4'-methylene diphenyl diisocyanate (MDI) material.

A worker attempting to remove solidified material inside a confined space (storage tank) suffered severe methemoglobinemia and almost died. The tank contained liquid 4,4'-methylene diphenyl diisocyanate monomer that had solidified after an equipment power failure caused excessive heating. Wearing a full-face elastomeric air-purifying respirator and Tyvek® coveralls, the worker used pneumatic air hammers to break up the solid material. After two tank entries totaling slightly less than one hour, the worker complained of headache and dizziness and within two hours of exiting the tank, he was admitted to the hospital in severe respiratory distress. During his eight-week hospital course, he suffered a cardiac arrest among other complications. An investigation into the cause of the worker's illness used onsite gas chromatography-mass spectrometry which identified aniline and p-toluidine vapor within the tank, attributable to overheating that led to formation of the solid material. Both are well-known causes of methemoglobinemia, and had the initial characterization of the confined space atmosphere adequately identified the hazards present appropriate engineering controls and personal protective equipment could have allowed the tank entrant to work safely in the space.

Exposure Assessment for Carbon Dioxide Gas: Full Shift Average and Short-Term Measurement Approaches.

Carbon dioxide (CO2) makes up a relatively small percentage of atmospheric gases, yet when used or produced in large quantities as a gas, a liquid, or a solid (dry ice), substantial airborne exposures may occur. Exposure to elevated CO2 concentrations may elicit toxicity, even with oxygen concentrations that are not considered dangerous per se. Full-shift sampling approaches to measure 8-hr time weighted average (TWA) CO2 exposures are used in many facilities where CO2 gas may be present. The need to assess rapidly fluctuating CO2 levels that may approach immediately dangerous to life or health (IDLH) conditions should also be a concern, and several methods for doing so using fast responding measurement tools are discussed in this paper. Colorimetric detector tubes, a non-dispersive infrared (NDIR) detector, and a portable Fourier transform infrared (FTIR) spectroscopy instrument were evaluated in a laboratory environment using a flow-through standard generation system and were found to provide suitable accuracy and precision for assessing rapid fluctuations in CO2 concentration, with a possible effect related to humidity noted only for the detector tubes. These tools were used in the field to select locations and times for grab sampling and personal full-shift sampling, which provided laboratory analysis data to confirm IDLH conditions and 8-hr TWA exposure information. Fluctuating CO2 exposures are exemplified through field work results from several workplaces. In a brewery, brief CO2 exposures above the IDLH value occurred when large volumes of CO2-containing liquid were released for disposal, but 8-hr TWA exposures were not found to exceed the permissible level. In a frozen food production facility nearly constant exposure to CO2 concentrations above the permissible 8-hr TWA value were seen, as well as brief exposures above the IDLH concentration which were associated with specific tasks where liquid CO2 was used. In a poultry processing facility the use of dry ice to quickly freeze product produced a nearly constant CO2 concentration that caused exposures to approach the permissible 8-hr TWA exposure value.

Exposure of unsuspecting workers to deadly atmospheres in below-ground confined spaces and investigation of related whole-air sample composition using adsorption gas chromatography.

Hazardous atmospheres in confined spaces may be obvious when a source of air contamination or oxygen (O2) deficiency is recognized. Such is often the case in general industry settings, especially with work processes which create hazardous atmospheres that may be anticipated. Hazards present in active sewers are also well recognized; but the possibility that O2 deficiency or high airborne contaminant concentrations may exist in new construction sewers or storm drains has been repeatedly ignored with deadly results. Low O2 and high carbon dioxide (CO2) concentrations may exist in new construction manholes that have not yet been connected to an active sewer or drain system, and these concentrations have been shown to vary over time. A recent incident is described where workers repeatedly entered such a confined space without incident, but subsequent entry resulted in a fatality and a near-miss for a co-worker rescuer. Additional cases are discussed, with an emphasis placed on elevated CO2 concentrations as a causative factor. A description is provided for the adsorptive gas chromatography whole-air analysis methodology used to quantitatively determine atmospheric conditions present at this type of fatality site or others after an incident, and for the gas chromatography-mass spectrometry method used to provide confirmation of analyte identity with high certainty. Many types of confined spaces may be encountered in addition to the underground varieties discussed, and many possible atmospheric hazards are possible. The definitive whole-air analysis approach described here may be of use and should be considered to investigate many confined space fatality and near-miss cases, and to better understand the causes of dangerous atmosphere conditions that may arise in confined spaces.

Short duration needle trap sampling with gas chromatography analysis to determine nearly instantaneous concentrations of selected organic vapor contaminants.

Needle trap device samplers were used for rapid (60 s) quantitative sampling of short-term exposure limit (STEL) and peak exposure standard concentrations using a manually operated pump to collect small volume (10 mL) gas phase samples containing methylene chloride, benzene, toluene, and tetrachloroethylene vapors. Solventless introduction of chemical samples for gas chromatography analysis with flame ionization detection yielded linear results (R(2) > 0.99) for vapor standard mixtures of the four target analytes ranging from 10% to 200% of their respective nominal STEL or peak exposure standard concentrations. Needle trap samplers showed ≥86% recovery (as GC-FID peak area responses) following 14-day storage at room temperature compared to the same samplers analyzed immediately, with better recovery values observed with shorter storage (≥95% at room temperature for seven days, except for methylene chloride) or with storage at 4°C. Calibration for quantitation of concentrations of benzene, toluene, and tetrachloroethylene was shown to be possible with the use of an internal standard to account for injector discrimination between the solventless NTD approach and injections of target analytes in carbon disulfide. Due to the simple sampling method (no field calibration and battery-free pumping) and the avoidance of solvent dilution, a needle trap sampling approach could simplify sample collection and analysis to chromatographically determine nearly instantaneous (1 min) exposure concentrations.

Determining airborne concentrations of spatial repellent chemicals in mosquito behavior assay systems.

BACKGROUND: Mosquito behavior assays have been used to evaluate the efficacy of vector control interventions to include spatial repellents (SR). Current analytical methods are not optimized to determine short duration concentrations of SR active ingredients (AI) in air spaces during entomological evaluations. The aim of this study was to expand on our previous research to further validate a novel air sampling method to detect and quantitate airborne concentrations of a SR under laboratory and field conditions. METHODOLOGY/PRINCIPAL FINDINGS: A thermal desorption (TD) gas chromatography-mass spectrometry (GC-MS) method was used to determine the amount of dichlorodiphenyltrichloroethane (DDT) in samples of air. During laboratory experiments, 1 L volumes of air were collected over 10 min intervals from a three-chamber mosquito behavior assay system. Significantly higher levels of airborne DDT were measured in the chamber containing textiles treated with DDT compared to chambers free of AI. In the field, 57 samples of air were collected from experimental huts with and without DDT for onsite analysis. Airborne DDT was detected in samples collected from treated huts. The mean DDT air concentrations in these two huts over a period of four days with variable ambient temperature were 0.74 µg/m(3) (n = 17; SD = 0.45) and 1.42 µg/m(3) (n = 30; SD = 0.96). CONCLUSIONS/SIGNIFICANCE: The results from laboratory experiments confirmed that significantly different DDT exposure conditions existed in the three-chamber system establishing a chemical gradient to evaluate mosquito deterrency. The TD GC-MS method addresses a need to measure short-term (<1 h) SR concentrations in small volume (<100 L) samples of air and should be considered for standard evaluation of airborne AI levels in mosquito behavior assay systems. Future studies include the use of TD GC-MS to measure other semi-volatile vector control compounds.

Application of a high surface area solid-phase microextraction air sampling device: collection and analysis of chemical warfare agent surrogate and degradation compounds.

This work examines a recently improved, dynamic air sampling technique, high surface area solid-phase microextraction (HSA-SPME), developed for time-critical, high-volume sampling and analysis scenarios. The previously reported HSA-SPME sampling device, which provides 10-fold greater surface area compared to commercially available SPME fibers, allowed for an increased analyte uptake per unit time relative to exhaustive sampling through a standard sorbent tube. This sampling device has been improved with the addition of a type-K thermocouple and a custom heater control circuit for direct heating, providing precise (relative standard deviation ∼1%) temperature control of the desorption process for trapped analytes. Power requirements for the HSA-SPME desorption process were 30-fold lower than those for conventional sorbent-bed-based desorption devices, an important quality for a device that could be used for field analysis. Comparisons of the HSA-SPME device when using fixed sampling times for the chemical warfare agent (CWA) surrogate compound, diisopropyl methylphosphonate (DIMP), demonstrated that the HSA-SPME device yielded a greater chromatographic response (up to 50%) relative to a sorbent-bed method. Another HSA-SPME air sampling approach, in which two devices are joined in tandem, was also evaluated for very rapid, low-level, and representative analysis when using discrete sampling times for the compounds of interest. The results indicated that subparts per billion by volume concentration levels of DIMP were detectable with short sampling times (∼15 s). Finally, the tandem HSA-SPME device was employed for the headspace sampling of a CWA degradation compound, 2-(diisopropylaminoethyl) ethyl sulfide, present on cloth material, which demonstrated the capability to detect trace amounts of a CWA degradation product that is estimated to be less volatile than sarin. The rapid and highly sensitive detection features of this device may be beneficial in decision making for law enforcement, military, and civilian emergency organizations and responders, providing critical information in a contaminated environment scenario when time is of the essence.

Synthesis, crystal structures, and dual donor luminescence sensitization in novel terbium tetracyanoplatinates.

A series of novel terbium tetracyanoplatinate compounds all incorporating tridentate 2,2':6'2″-terpyridine (terpy) or 4'-chloro-2,2':6'2″-terpyridine (terpy-Cl) were synthesized and used to investigate the phenomenon of dual-donor sensitization of Tb(3+). Judicious choice of the Tb(3+) salt and reaction conditions results in the isolation of {Tb(terpy)(H2O)2(NO3)Pt(CN)4}·CH3CN (1A), {Tb(terpy)(H2O)2(NO3)Pt(CN)4}·3.5H2O (1B), {Tb(terpy-Cl)(H2O)2(NO3)Pt(CN)4}·2.5H2O (2), [Tb(terpy)(H2O)2(CH3COO)2]2Pt(CN)4·4H2O (3), or [Tb2(terpy)2(H2O)2(CH3COO)5]2Pt(CN)4·7H2O (4). The compounds 1A, 1B, and 2 contain one-dimensional polymeric structures with bridging of [Tb(L)(NO3)(H2O)2](2+) (L = terpy or terpy-Cl) moieties by cis-bridging tetracyanoplatinate (TCP) anions as determined via single-crystal X-ray diffraction studies. Both 3 and 4, however, contain Tb(3+) coordinated by multiple acetate ligands and terpy, but not TCP, and are classified as zero-dimensional complex salts. Platinophilic interactions that dominate tetracyanoplatinate structural chemistry are present in the form of dimeric units in the polymeric compounds, but are totally absent in 3 and 4. The structural differences result in markedly different luminescence properties for the two classes of compounds. All of the polymeric compounds display efficient donor-acceptor intramolecular energy transfer (IET) from the terpy unit to the Tb(3+) ion. Although the TCP units are also directly coordinated to the Tb(3+) ion in the three polymers, only in 1B and 2 are the Pt···Pt interactions strong enough to provide MMLCT bands of appropriate energy to result in a dual-donor effect to the Tb(3+) sensitization. Even in these cases, TCP does not efficiently sensitize the Tb(3+), rather a broad band TCP emission results. However, terpy and acetate ligands are bonded directly to the Tb(3+) ion in 3 and 4 and provide a strong dual-donor sensitization effect as evidenced by the large QY for Tb(3+).

Person-portable gas chromatography: rapid temperature program operation through resistive heating of columns with inherently low thermal mass properties.

As open tubular gas chromatography was becoming widely adopted, the potential to rapidly heat and cool the low thermal mass of an open tubular fused silica column was recognized. Numerous resistive column heating approaches were subsequently described and demonstrated, often with a common objective to focus heating efforts on the column alone, rather than on a large convection oven. Low thermal mass column bundles have been commercially available for about ten years, where insulated wires in close proximity to a coiled open tubular capillary column provide resistive heating. Before this, person-portable gas chromatographs either operated isothermally at relatively low temperatures or at ambient temperature to lessen power demands, but several person-portable gas chromatography-mass spectrometry (GC-MS) instruments capable of temperature program operation have become available in the past ten years based on this heating method. When low thermal mass heated zones are used, and with a direct GC-MS interface, analysis times of less than 5 min are possible for target compounds having a wide range of volatilities. Previous capabilities in transportable and person-portable gas chromatography instrumentation are reviewed to demonstrate the scale of advancement made possible by the adoption of open tubular columns and low power heating techniques now becoming routinely available. Microcomachined columns which are usually etched in a silicon wafer represent a radical break from the traditional fused silica open tubular column design, and increasing efforts to use this column construction approach are also examined. The developments discussed have introduced the potential to rapidly analyze compounds with a wide volatility range in the field to protect deployed military forces, the health of workers, and the health of the general public.

Dichlorodiphenyltrichloroethane determination in air by thermal desorption gas chromatography-mass spectrometry.

BACKGROUND: Current quantitative methods for airborne dichlorodiphenyltrichloroethane (DDT) require collection and extraction times of ≥ 12 h. The aim of this study was to develop a method for quantifying airborne DDT with a short (<4 h) collection and analysis time. RESULTS: Precision [relative standard deviation (RSD)] for each calibration point (0.8-9.0), linearity (R(2) = 0.99) and apparent recovery (R' = 96.5%) were determined from thermal desorption (TD) gas chromatography-mass spectrometry (GC-MS) analyses of Tenax-TA-packed sampling tubes spiked with 1-250 ng of DDT. Recovery of (13) C-labeled 4,4'-DDT from tubes spiked before and after air sampling was 97.3 and 90.3% respectively. DDT was detected and quantified in 1-3 L samples of air collected during 10-180 min sampling events. A significant difference was observed in DDT air concentration between 28 and 33 °C during microchamber studies. CONCLUSIONS: The results demonstrate that the TD GC-MS method developed in this study is precise, reproducible and linear over the span of 1-250 ng of DDT spiked onto TD tubes. By avoiding dilution of the sample, the method described allows the measurement of DDT vapor concentrations during short sampling periods (10-180 min) relevant to mosquito behavior studies.

Synthesis, structural, and photoluminescence studies of Gd(terpy)(H2O)(NO3)2M(CN)2 (M = Au, Ag) complexes: multiple emissions from intra- and intermolecular excimers and exciplexes.

The highly luminescent bimetallic cyanide materials, Gd(terpy)(H(2)O)(NO(3))(2)M(CN)(2) (M = Au, Ag; GdAu and GdAg, respectively) are quick and easy to synthesize under ambient conditions. A characteristic feature exhibited by both solid-state compounds is an intense red emission when excited with UV light. Additionally, GdAu exhibits a broad-band green emission upon excitation in the near UV region. A combination of structural and spectroscopic results for the compounds helps explain the underlying conditions responsible for their unique properties. Single-crystal X-ray diffraction experiments expose their structural features, including the fact that they are isostructural. Crystallographic data for the representative GdAu compound (Mo K(α), λ = 0.71073 Å, T = 290 K): triclinic, space group P ̅1, a = 7.5707(3) Å, b = 10.0671(4) Å, c = 15.1260(4) Å, α = 74.923(3)°, ß = 78.151(3)°, γ = 88.401(3)°, V = 1089.04(7) Å(3), and Z = 2. Although the compounds crystallize as dimers containing M···M distances smaller than the sum of their van der Waals radii, the Au···Au (3.5054(4) Å) and/or the Ag···Ag (3.6553(5) Å) interactions are relatively weak and are not responsible for the low energy red emission. Rather, the green emission in GdAu presumably originates from the [Au(CN)(2)(-)](2) dimeric excimer, while the [Ag(CN)(2)(-)](2) dimers in GdAg do not display visible emission at either 290 or 77 K. The unusual red emission exhibited by both compounds likely originates from the formation of an excited state exciplex that involves intermolecular π-stacking of 2,2':6',2"-terpyridine ligands. The room-temperature and low-temperature steady-state photoluminescent properties, along with detailed time-dependent, lifetime, and quantum yield spectroscopic data provide evidence regarding the sources of the multiple visible emissions exhibited by these complexes.

Use of a hand-portable gas chromatograph-toroidal ion trap mass spectrometer for self-chemical ionization identification of degradation products related to O-ethyl S-(2-diisopropylaminoethyl) methyl phosphonothiolate (VX).

The chemical warfare agent O-ethyl S-(2-diisopropylaminoethyl) methyl phosphonothiolate (VX) and many related degradation products produce poorly diagnostic electron ionization (EI) mass spectra by transmission quadrupole mass spectrometry. Thus, chemical ionization (CI) is often used for these analytes. In this work, pseudomolecular ([M+H](+)) ion formation from self-chemical ionization (self-CI) was examined for four VX degradation products containing the diisopropylamine functional group. A person-portable toroidal ion trap mass spectrometer with a gas chromatographic inlet was used with EI, and both fixed-duration and feedback-controlled ionization time. With feedback-controlled ionization, ion cooling (reaction) times and ion formation target values were varied. Evidence for protonation of analytes was observed under all conditions, except for the largest analyte, bis(diisopropylaminoethyl)disulfide which yielded [M+H](+) ions only with increased fixed ionization or ion cooling times. Analysis of triethylamine-d(15) provided evidence that [M+H](+) production was likely due to self-CI. Analysis of a degraded VX sample where lengthened ion storage and feedback-controlled ionization time were used resulted in detection of [M+H](+) ions for VX and several relevant degradation products. Dimer ions were also observed for two phosphonate compounds detected in this sample.

Unknown exposures: gaps in basic characterization addressed with person-portable gas chromatography-mass spectrometry instrumentation.

A newly developed person-portable gas chromatography-mass spectrometry (GC-MS) system was used to analyze several solvent standards, contact cement, paint thinner, and polychlorinated biphenyl samples. Passive solid phase microextraction sampling and fast chromatography with a resistively heated low thermal mass GC column were used. Results (combined sampling and analysis) were obtained in <2 min for solvent, contact cement, and paint thinner samples, and in <13 min for the polychlorinated biphenyl sample. Mass spectra produced by the small toroidal ion trap detector used were similar to those produced with heavily used transmission quadrupole mass spectrometers for polychlorinated biphenyl compounds, simple alkanes, and cycloalknes, while mass spectra for benzene and the ketone compounds analyzed showed evidence for ion/molecule reactions in the ion trap. For one of the contact cement samples analyzed, no evidence was found to indicate the presence of n-hexane, although the relevant material safety data sheet listed this ingredient. Specific chemical constituents corresponding to a potentially wide range of petroleum distillate compounds were identifiable from GC-MS analyses. The possibility for an improved basic characterization step in the exposure assessment process exists with the availability of fast, person-portable GC-MS, although work is needed to further refine this tool and understand the best ways it may be used.

Artifacts related to N-methyl-N-(tert-butyldimethylsilyl)trifluoroacetamide derivatization of citrulline revealed by gas chromatography-mass spectrometry using both electron and chemical ionization.

Derivatization with N-methyl-N-(tert-butyldimethylsilyl)trifluoroacetamide (MTBSTFA) was used for gas chromatography-mass spectrometry (GC-MS) analysis of citrulline and ornithine. Aqueous 50 microl aliquots at 1 and 10 mM concentrations were dried and derivatized separately, and 70 eV electron ionization or CH(4) positive chemical ionization were used. Ornithine produced a single GC peak. Physiological citrulline concentrations produced GC artifact peaks for the ornithine derivative, and a compound consistent with elimination of a water molecule from the tri-tert-butyldimethylsilyl (TBDMS) citrulline derivative. A third GC peak obtained using 10 mM citrulline concentrations gave a mass spectrum consistent with a mixture of true tri- and tetra-TBDMS citrulline. Analyses of (13)C-ureido-labeled citrulline confirmed the presence of the true TBDMS citrulline derivatives produced from 10 mM samples and provided evidence that the TBDMS ornithine artifact results from loss of TBDMS isocyanate from tetra-TBDMS citrulline. Linear-programmed temperature GC retention index data relative to n-alkanes are reported for observed GC peaks.

catena-Poly[[[diaqua-(nitrato-κO,O')(2,2':6',2''-terpyridine-κN,N',N'')ytterbium(III)]-µ-cyanido-κN:C-[dicyanido-platinum(II)]-µ-cyanido-κC:N] acetonitrile monosolvate].

The title compound, {[PtYb(CN)(4)(NO(3))(C(15)H(11)N(3))(H(2)O)(2)]·CH(3)CN}(n), was isolated from solution as a one-dimensional coordination polymer. The Yb(3+) site has ninefold coordination with a distorted tricapped trigonal-prismatic geometry, while the Pt(II) ion is coordinated by four cyanide groups in an almost regular square-planar geometry. cis-Bridging by the tetra-cyanidoplatinate(II) anions links the Yb(3+) cations, forming chains. Additionally, each Yb(3+) is coordinated by two water mol-ecules, one bidentate nitrate anion, and one tridentate 2,2':6',2''-terpyridine mol-ecule. O-H⋯N hydrogen-bonding inter-actions are found between adjacent chains and help to consolidate the crystal packing. In addition, π-π stacking inter-actions exist between the terpyridine ligand and the two corresponding terpyridine ligands along the adjacent chain (average inter-planar distance = 3.667 Å). Moderate Pt⋯Pt inter-actions [3.5033 (4) Å] are observed in the structure.

Directly heated high surface area solid phase microextraction sampler for rapid field forensic analyses.

A high-surface area solid phase microextraction (HSA-SPME) sampler is described for dynamic sampling at high air velocities (up to several hundred centimeters per second). The sampling device consists of a thin wire coated with carboxen/polydimethylsiloxane (carboxen/PDMS) material, wound in the annular space between two concentric glass tubes, providing a large trapping surface from which analytes may then be thermally desorbed with little power consumption upon resistive heating of the wire. Desorbed analytes are focused and reconcentrated on a microtrap that is subsequently resistively heated to introduce analytes for GC or GC/MS analysis. Benzene, toluene, ethylbenzene, and xylenes (BTEX) included in a 39-component toxic organics (TO-14) gas mixture were used to evaluate the efficiency of the HSA-SPME sampler. Quantitation of trace-level BTEX compounds present during weapons cleaning was completed using stepwise calibration. Detection limits of 0.2-6.9 pptr(v) were observed for these analytes using single ion monitoring GC/MS analysis, and an improvement in sensitivity of several orders of magnitude was achieved when compared to standard dynamic flow SPME with a commercially available 10 mm carboxen/PDMS fiber. The potential for rapid analyte uptake and improved sensitivity using the HSA-SPME design will make it possible to rapidly collect and analyze VOC samples in field settings using a portable hand-held pump and a small, low power GC/MS instrument. This system will be especially useful for situations involving forensics, public safety, and military defensive or intelligence needs where rapid, sensitive detection of airborne analytes is required.

Emission enhancement through dual donor sensitization: modulation of structural and spectroscopic properties in a series of europium tetracyanoplatinates.

The synthesis of three different europium tetracyanoplatinates all incorporating 2,2':6',2''-terpyridine (terpy) have been carried out in acetonitrile/water mixtures by reaction of Eu(3+) salts with terpy and potassium tetracyanoplatinate. The use of different Eu(3+) sources results in the isolation of Eu(C(15)H(11)N(3))(H(2)O)(2)(NO(3))(Pt(CN)(4)) x CH(3)CN (1), {Eu(C(15)H(11)N(3))(H(2)O)(3)}(2)(Pt(CN)(4))(3) x 2 H(2)O (2), or [Eu(C(15)H(11)N(3))(H(2)O)(2)(CH(3)COO)(2)](2)Pt(CN)(4) x 3 H(2)O (3) for the nitrate, triflate, or acetate salts, respectively. All three compounds have been prepared as colorless crystals, and single-crystal X-ray diffraction has been used to investigate their structural features. Crystallographic data (MoK alpha, lambda = 0.71073 A, T = 290 K): 1, monoclinic, space group P2(1)/c, a = 12.835(1), b = 15.239(1), c = 13.751(2) A, beta = 105.594(9) degrees, V = 2590.8(5) A(3), Z = 4; 2, triclinic, space group P1, a = 9.1802(8) A, b = 10.8008(9) A, c = 13.5437(9) A, alpha = 84.491(6) degrees, beta = 75.063(7) degrees, gamma = 79.055(7) degrees, V = 1272.4(2) A(3), Z = 1; 3, triclinic, space group P1, a = 12.110(3) A, b = 12.7273(11) A, c = 18.7054(16) A, alpha = 92.859(7) degrees, beta = 92.200(11) degrees, gamma = 118.057(10) degrees, V = 2534.8(7) A(3), Z = 2. Variation of the counteranions in these systems provides the opportunity to modify the structures and coordination environment of Eu(3+) for 1-3. Compounds 1 and 2 are both one-dimensional, polymeric compounds that contain Eu(3+) ions chelated by terpy and bridged by tetracyanoplatinate anions. 3 is a zero-dimensional complex salt in which Eu(3+) is coordinated by terpy, acetate, and water, but not tetracyanoplatinate. The structural differences result in varying sensitization phenomena for the three compounds. Compounds 1 and 2 display efficient donor-acceptor intramolecular energy transfer (IET) where dual donor species, terpyridine and tetracyanoplatinate, simultaneously enhance the acceptor Eu(3+) emission. In both compounds the donor species are directly coordinated to the acceptor ion, and hence a highly efficient dual-donor effect is exhibited for the IET mechanisms. In 3 where only the terpy ligand is directly coordinated to Eu(3+), the sensitization involves only one donor species. The Pt(CN)(4)(2-) unit in 3, which lacks direct bonding to Eu(3+), exhibits strong emission indicating the lack of cooperative enhancement of the lanthanide emission.