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There is presently no instrumentation that can provide (near) real time information on elemental composition of atmospheric aerosols. We describe an arrangement where air is sampled through a cyclone @30L/min with a 50% cutoff @ ~250nm. The particles deposit into a cup through which deionized water is continuously flowing. High purity HNO3 is added downstream and the mixed stream optionally flows...
Chromium speciation by spectrophotometric determination of hexavalent chromium (Cr(VI)) with diphenylcarbazide (DPC) has several problems. These include: (1) the inability to directly detect trivalent chromium (Cr(III)) with DPC, (2) positive interference in Cr(VI) determination by other metal cations and (3) negative interference by any reducing agent present in the sample. These are addressed with...
Electrodialytic ion transfer was studied as a matrix isolation tool for heavy metal determinations. An ion transfer device (ITD) was used for the transfer of heavy metal cations. Under optimized flow rates applied voltage and receptor composition, heavy metal ions were quantitatively transferred at concentrations spanning µgL −1 to mgL −1 . As long as the sample pH was acidic, there...
Ion exchangers are ionic equivalents of doped semiconductors, where cations and anions are equivalents of holes and electrons as charge carriers in solid state semiconductors. We have previously demonstrated an ion exchange membrane (IEM) based electrolyte generator which behaves similar to a light-emitting diode and a charge detector (ChD) which behaves analogous to a p–i–n photodiode. The previous...
A fully automated system for the determination of trace mercury in water by cold vapor atomic absorption spectrometry (CVAAS) is reported. The system uses preconcentration on a novel sorbent followed by liberation of the mercury and focusing by a gold trap. Mercury ions were extracted from water samples by passage through a solid phase sorbent column containing 2-(3-(2-aminoethylthio)propylthio)ethanamine...
We describe a method for expanding the linear dynamic range for multiple reaction monitoring (MRM) in quantitative liquid chromatography/tandem mass spectrometry (LC–MS/MS) using additional transitions for isotopologues. In addition to the regular transition for the highest possible sensitivity, a transition corresponding to the less abundant isotopologue ions was utilized. This decreases saturation...
An open channel scrubber is proposed as a miniature fieldable gas collector. The device is 100mm in length, 26mm in width and 22mm in thickness. The channel bottom is rendered hydrophilic and liquid flows as a thin layer on the bottom. Air sample flows atop the appropriately chosen flowing liquid film and analyte molecules are absorbed into the liquid. There is no membrane at the air–liquid interface:...
An automated atmospheric elemental mercury analyzer based on the dielectric barrier discharge (DBD) atomic emission technique was developed. The instrument is based on a gold-on tungsten coiled filament preconcentrator fashioned from commercial quartz-halogen lamps, a DBD excitation source and a radiation detector. An in-house program provided system control and data collection. Several types of radiation...
Accurate quantitation of iodine in biological samples is essential for studies of nutrition and medicine, as well as for epidemiological studies for monitoring intake of this essential nutrient. Despite the importance of accurate measurement, a standardized method for iodine analysis of biological samples is yet to be established. We have evaluated the effectiveness of 72 Ge, 115 In,...
Calixarenes are interesting building blocks in supramolecular receptor design. They can be easily functionalized to give the desired guest binding and sequestration properties. We demonstrate here the use of simple alkylated calixarenes as novel NO 2 sensors. Upon reacting with gaseous NO 2 , alkylated calixarenes form stable calixarene-NO + (nitrosonium) complexes that have...
A versatile, simple, liquid core waveguide (LCW)-based fluorescence detector design is described for capillary systems. A Teflon AF coated fused silica capillary serves as the LCW. The LCW is transversely excited. The light source can be a conventional or high power (HP) light emitting diode (LED) or a laser diode (LD). The source can be coupled to the LCW directly or via an optical fiber. Fiber coupling...
A gas phase chemiluminescence (GPCL)-based method for trace measurement of arsenic has been recently described for the measurement of arsenic in water. The principle is based on the reduction of inorganic As to AsH 3 at a controlled pH (the choice of pH governs whether only As(III) or all inorganic As is converted) and the reaction of AsH 3 with O 3 to produce chemiluminescence...
A capacitance to digital converter (AD7746) is used in the same mode as noncontact conductance detectors. The detector output is linearly proportional to specific conductance (σ) at low σ values but becomes nonlinear and reaches a plateau value at σ ∼>0.75mS/cm, regardless of the nature of the electrolyte. For all applications at sub- to low-mM concentrations, the device, available as an evaluation...
The bleaching action of ozone on indigo and related compounds is well known. We describe sensitive automated instrumentation for measuring ambient ozone. Air is sampled around a porous polypropylene tube filled with a solution of indigotrisulfonate. Light transmission through the tube is measured. Light transmission increases as O 3 diffuses through the membrane and bleaches the indigo. Evaporation...
Analyte transfer from the matrix in a thin layer distillation (TLD) cell and its subsequent measurement were investigated in a flow injection configuration. We designed the cell such that the donor and acceptor streams flowed in parallel channels separated by a thin dividing wall. The matrix transfer process involved room-temperature distillation of the analyte into the headspace of the TLD cell and...
A frequency-selective absorbance detection approach and its applications are described. First, a digital signal processor–lock-in amplifier (DSP–LIA)-based absorbance detector was evaluated. Compared to a simple operational amplifier (TL082CP)-based detector, the DSP–LIA-based detector showed lower noise levels, but the relative advantage was reduced under very low photocurrent levels (down to few...
Ozone has become the oxidant of choice for water disinfection, especially in large water treatment facilities. This paper describes a fast and sensitive method for the determination of ozone content by reaction with photoactivated chromotropic acid (CA, 4,5-dihydroxynaphthalene-2,7-disulfonic acid), which results in intense chemiluminescence (CL). Freshly ozonated water from a recirculating ozonizer/reservoir...
The determination of perchlorate in complex matrices by ion chromatography (IC) with an online preconcentration and preelution technique is discussed. The method was applied to different sample types containing large concentrations of matrix anions that would otherwise interfere with analysis via conventional IC. The present approach was highly effective in removing most of the matrix anions and was...
We propose a method for the determination of acid dissociation constants based on the rapid detection of the equivalence point (EP) by feedback-based flow ratiometry and the subsequent estimation of the half equivalence point (EP 1/2 ). The titrant (e.g., NaOH) flow rate F B was varied in response to a control voltage V c from a controller, while the titrand (e.g...
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