Mass Detection Limit Research Articles

Fissile and non-fissile element separation in concrete radioactive waste drums using the SIMPHONIE method

The simultaneous photon and neutron interrogation experiment (SIMPHONIE) method, applied to radioactive waste drum characterization, has already been treated in [F. Jallu, A. Lyoussi, C. Passard, E. Payan, H. Recroix, G. Nurdin, A. Buisson, J. Allano, Nucl. Instr. and Meth. B 170 (2000) 489]. First experimental results carried out with U and Pu bare samples were presented, that showed the feasibility of quantifying fissile ( 235U, 239,241Pu, …) and non-fissile ( 234,236,238U, 238,240Pu, …) elements separately in only one measurement, using both active neutron interrogation and induced photofission interrogation techniques simultaneously. This paper presents new experimental results carried out with U samples embedded in a concrete matrix. These results have been obtained using the DGA/ETCA MiniLinatron pulsed linear electron accelerator located at Arcueil, France. Mass detection limits of less than 2 g of matter have been obtained with the preliminary setup used in these experiments.

On-line analysis of ambient air aerosols using laser-induced breakdown spectroscopy

Laser-induced breakdown spectroscopy is developed for the detection of aerosols in ambient air, including quantitative mass concentration measurements and size/composition measurements of individual aerosol particles. Data are reported for ambient air aerosols containing aluminum, calcium, magnesium and sodium for a 6-week sampling period spanning the Fourth of July holiday period. Measured mass concentrations for these four elements ranged from 1.7 parts per trillion (by mass) to 1.7 parts per billion. Ambient air concentrations of magnesium and aluminum revealed significant increases during the holiday period, which are concluded to arise from the discharge of fireworks in the lower atmosphere. Real-time conditional data analysis yielded increases in analyte spectral intensity approaching 3 orders of magnitude. Analysis of single particles yielded composition-based aerosol size distributions, with measured aerosol diameters ranging from 100 nm to 2 μm. The absolute mass detection limits for single particle analysis exceeded sub-femtogram values for calcium-containing particles, and was on the order of 2–3 femtograms for magnesium and sodium-based particles. Overall, LIBS-based analysis of ambient air aerosols is a promising technique for the challenging issues associated with the real-time collection and analysis of ambient air particulate matter data.

Determination of carbohydrates as their p-sulfophenylhydrazones by capillary zone electrophoresis

p-Hydrazinobenzenesulfonic acid was explored as an ultraviolet labeling reagent for capillary electrophoresis of mono-, di- and trisaccharides. The labeling reaction that produces p-sulfophenylhydrazines took less than 8 min, and introduced both chromphore and charged groups into the carbohydrate molecules. The derivatives of nine mono- and disaccharides were completely separated in 9 min using a 100 mM borate buffer at pH 10.24. On-column UV detection at 200 nm allowed the detection of glucose with a mass detection limit of 17.6 fmol or a concentration limit of 3.6 μM. Reproducible quantification of carbohydrates was achieved in the concentration range of 0.1–9.1 mM in reaction solution. The method was applied successfully to determine the monosaccharide composition of laminaran.

Comparison of gas chromatography detection limits and relative responses of common alternative fluorocarbons using electron capture, atomic emission, and mass spectrometry detection

Detection limits for several common alternative fluorocarbons (AFCs) using electron capture detector (ECD), mass spectrometry (MS) and atomic emission detector (AED) gas chromatography (GC) are determined and compared. Mass detection limits for chlorofluorocarbon (CFC) CFC-12, and hydrochlorofluorocarbons (HCFCs) HCFC-22, HCFC-123 and HCFC-124 are found to be in the picogram range. Those of hydrofluorocarbons (HFCs) HFC-125, HFC-134a and HFC-152a are found to be in nanograms using ECD and in the picogram range for the MS and AED. HFC-152a was not detected by the ECD. Relative ECD responses for all AFCs are at least one order of magnitude lower than that for CFC-12. The relative MS responses are found to be in the same order of magnitude of that for CFC-12. For the AED, all AFCs had somewhat higher responses than CFC-12 with the exception of HFC-152a, which showed the same response than CFC-12. The mass detection limits for 1 L sample with a signal-to-noise of 3 σ is in the low ppt (v/v) for AED and MS. ECD has a limit of detection of about one order of magnitude higher than other detectors for the HCFCs, and a limit of detection in the nanogram range for the HFCs. MS has slightly higher sensitivity than the AED, and both detector proved to be far better for the detection of the AFCs than the ECD. Preconcentration of whole-air sample is required for all tested methods to make measurements at predicted levels. An amount of 1–10 L samples are needed for AED and MS while ECD requires 10–100 L samples for HCFCs and over 100 L for the HFCs. A more sensitive detector is still needed to perform in situ analysis without preconcentration for the current atmospheric concentrations.

Evaluation of temperature programming for gradient elution in packed capillary liquid chromatography coupled to electrochemical detection

AbstractA miniaturized amperometric detector compatible with temperature‐programmed packed capillary liquid chromatography has been constructed and evaluated. Temperature programming could successfully be used as a tool for retention control, providing gradient action that did not influence the detector performance. A 7‐μm single carbon fiber was utilized as working electrode and detection was performed in a 50‐μm i.d. fused silica detection capillary which also functioned as restriction capillary. Separation of tyrosine, 3‐(3,4‐dihydroxyphenyl)alanine, 3‐chloro‐tyrosine and 3‐NO2‐tyrosine was achieved in 6 min using a temperature program from 30°C to 100°C with a ramp of 8°C/min on a 25 cm 0.32 mm i.d. column packed with 3 μm Hypersil ODS. The mobile phase consisted of 50 mM citric acid (pH 3.10)‐methanol (95+ 5, v/v), and the mass limit of detection was in the range 1–5 pg using 1.2 V vs the Ag/AgCl reference electrode. © 2001 John Wiley & Sons, Inc. J Micro Sep 13: 179–185, 2001

The determination of natural uranium in human tissues by recovery corrected kinetic phosphorescence analysis

Two typical methods used for the determination of uranium in human autopsy tissues are kinetic phosphorescence analysis (KPA) and alpha-spectrometry, both of which have significant limitations and advantages. KPA is limited because of the amount of sample used (1–10 ml for sample digestion followed by one ml KPA aliquots), no isotopic information is provided, phosphorescence degradation by salts in solution, and even more importantly, it does not provide chemical recovery information. For samples with sub ng uranium concentrations per g of inorganic material, preconcentration is necessary, which may require chemical recovery (other than simple evaporation). While alpha-spectrometry has very good radiometric detection limits for 238U, the very long half-life of 238U (4.468·109 y) restricts its mass detection limit (27 ng). KPA, on the other hand, has a detection limit three orders of magnitude lower (0.02 ng) for natural uranium. A recovery corrected method for the determination of natural uranium in human tissues was developed combining preconcentration of human tissues dissolved in 6M HCl by anion exchange with alpha-spectrometry and kinetic phosphorescence analysis, utilizing 232U as a tracer. Solution aliquots containing up to 6 g of bone ash were pre-concentrated for KPA measurement thereby allowing the use of up to 25% of the original sample solution weight for analysis by KPA. The radiochemical yield of 232U was determined by alpha-spectrometry and the uranium content was determined by KPA. The mean radiochemical yields obtained for human tissue samples range from 65% to 106% with a mean of 85%±8%.

Synchronous fluorescence and absorbance dynamic liquid drop sensor for Cr(vi) determination at the femtomole level

A novel synchronous fluorimetric and absorptiometric technique based on dynamic liquid drops coupled with flow injection is described for the determination of chromium(VI) in aqueous solutions. Drops formed continuously at the end of a quartz capillary tube serve as reactor and optical cell. The reaction between chromium(VI) and 3,3',5,5'-tetramethylbenzidine dichloride (TMB-d) results in a significant decrease in fluorescence and transmitted light intensity, proportional to the logarithm of the concentration of chromium(VI). The transmitted light and fluorescence emission are detected in counter and perpendicular positions of the excitation light by a photomultipler tube and photodiode, respectively. In HCl-NaOAc buffer solution (pH 3.29), the sensor has a wide linear calibration range of 2 x 10(-8)-1 x 10(-4) mol l(-1) chromium(VI) with an absolute mass detection limit of 12.88 fmol.

An inductively coupled plasma carbon emission detector for aqueous carbohydrate separations by liquid chromatography.

An inductively coupled plasma atomic emission spectrometer is used to detect carbon-containing compounds following separation by high-performance liquid chromatography. A calcium form ligand exchange column with distilled and deionized water as the mobile phase is used to separate carbohydrates. The eluting species are detected by monitoring the carbon atomic emission line at 193.09 nm. The mass detection limits using a photomultiplier tube for sucrose and glucose are 50 ng, while that for fructose is 60 ng. The carbon emission detector should provide the same detection limit for any compound with a similar mass percent of carbon, whether or not the compound exhibits appreciable absorption characteristics. While the carbon emission detector will universally detect any organic compound, it will discriminate against species with high molar absorptivity that may be present at low concentration. Such species may act as interferences in chromatograms generated with conventional UV-visible absorption detectors. To demonstrate the utility of the carbon emission detector, three sugars (glucose, fructose, sucrose) are determined in apple, crangrape, and orange juice.

Capillary liquid chromatographic determination of neutral phenolic compounds in apple juices

Capillary liquid chromatography (CLC) is evaluated as an alternative to conventional HPLC to analyse complex phenolics. Several neutral phenolic compounds were separated on a packed-reversed phase fused-silica capillary column, and determined with UV detection. A conventional liquid chromatographic equipment was adapted for such purposes. Application of the proposed method to the quantification of neutral phenols in apple juices is reported. Phenolics are extracted and fractionated into neutral and acidic compounds by means of a C 18 solid-phase cartridge. Typical recoveries ranging from 90 to 105% are obtained and reproducibility between extractions is <7% in all cases. Mass detection limits are at the sub-nanogram level.

Analysis of glutamate in beverages and foodstuffs by capillary electrophoresis with laser-induced fluorescence detection

A simple, sensitive, and robust method has been developed for the separation and quantification of glutamate in beverages and foodstuffs. Samples were derivatized with 5 × 10−4 M fluorescein isothiocyanate. Glutamate was separated by capillary electrophoresis and detected by laser-induced fluorescence with 488-nm radiation from an argon ion laser. Response was linearly dependent on concentration between 10−7 and 10−4 M. The limit of mass detection was 16 amol and the limit of concentration detection was 5.4×10−10 M. Intra- and interday precision were 3.3%RSD (n=11) and 4.8%RSD (n=7), respectively. The method has been applied to beverages and other foods.

Temperature-Programmed Packed Capillary Liquid Chromatography Coupled to Fourier-Transform Infrared Spectroscopy

Temperature-programmed packed capillary liquid chromatography has been coupled off-line to Fourier-transform infrared spectroscopy, utilizing a commercially available interface with a pneumatic nebulizer rebuilt to handle low flow rates at elevated temperatures. The modified interface showed excellent performance with regard to non-aqueous reversed phase separations of polymer additives, resulting in constructed Gram-Schmidt chromatograms comparable to chromatograms obtained using UV detection. The spray of the in-house constructed nebulizer was not influenced by temperature changes of the column effluent, and hence temperature-programmed gradient separations could be used successfully. The relative standard deviation of peak height was 4.4% (n = 5) and the mass limit of detection was determined to be about 40 ng, using a polymer antioxidant as model compound. The present instrumental coupling has been used for characterization of the antioxidant Irgafos P-EPQ.

Powder Microelectrodes for Capillary Electrophoresis with Amperometric Detection

In this paper, we first report the use of powder microelectrodes (PMEs) as the amperometric detector for thiols, hydrazine and hydroxylamine in capillary electrophoresis (CE). This PME, with graphite-supported metalloporphyrin powder as catalyst, offers a few advantages as an amperometric detector in CE. Concentration limit of detection and mass limit of detection obtained for L-cysteine at the PME could reach 88 nM and 230 amol, respectively. The response of thiols at the PME was very reproducible since the electrode fouling was reduced. A relative standard deviation of peak heights (n = 8) of 1.8% and a relative standard deviation of migration time (n = 8) of 1.0% can be obtained for L-cysteine. The material packed in the PME can easily be changed. Hence, it is very convenient to choose suitable catalysts to detect special analytes, and this specially designed microelectrode should be applicable to many other compounds of biological interest.

Effects of molecular oxygen on multiphoton-excited photochemical analysis of hydroxyindoles.

We have examined the effects of dissolved molecular oxygen on multiphoton-excited (MPE) photochemical derivatization of serotonin (5HT) and related cellular metabolites in various buffer systems and find that oxygen has a profound effect on the formation efficiency of visible-emitting photoproducts. Previously, end-column MPE photoderivatization provided low mass detection limits for capillary electrophoretic analysis of hydroxyindoles, but relied on the use of Good's buffers to generate high-sensitivity visible signal. In the present studies, visible emission from 5HT photoderivatized in different buffers varied by 20-fold under ambient oxygen levels but less than 2-fold in the absence of oxygen; oxygen did not significantly alter the photoproduct excited-state lifetime (approximately 0.8 ns). These results support a model in which oxygen interferes with formation of visible-emitting photoproducts by quenching a reaction intermediate, an effect that can be suppressed by buffer molecules. Deoxygenation of capillary electrophoresis separation buffers improves mass detection limits for 5-hydroxyindoles fractionated in 600-nm channels by approximately 2-fold to < or =30000 molecules and provides new flexibility in identifying separation conditions for resolving 5HT from molecules with similar electrophoretic mobilities, such as the catecholamine neurotransmitters.

Molecular Beacons for DNA Biosensors with Micrometer to Submicrometer Dimensions

Ultrasensitive molecular beacon (MB) DNA biosensors, with micrometer to submicrometer sizes, have been developed for DNA/RNA analysis. The fluorescence-based biosensors have been applied in DNA/RNA detection without the need for a dye-labeled target molecule or an intercalation reagent in the testing solution. Molecular beacons are hairpin-shaped oligonucleotides that report the presence of specific nucleic acids. We have designed a surface-immobilizable biotinylated ssDNA molecular beacon for DNA hybridization at a liquid-solid interface. The MBs have been immobilized onto ultrasmall optical fiber probes through avidin-biotin binding. The MB DNA biosensor has been used directly to detect, in real time, its target DNA molecules without the need for a competitive assay. The biosensor is stable and reproducible. The MB DNA biosensor has selectivity with single base-pair mismatch identification capability. The concentration detection limits and mass detection limits are 0.3 nM and 15 amol for a 105-μm biosensor, and 10 nM and 0.27 amol for a submicrometer biosensor, respectively. We have also prepared molecular beacon DNA biosensor arrays for simultaneous analysis of multiple DNA sequences in the same solution. The newly developed DNA biosensors have been used for the precise quantification of a specific rat γ-actin mRNA sequence amplified by the polymerase chain reaction.

Conductivity detection of polymerase chain reaction products separated by micro-reversed-phase liquid chromatography

In this paper, we describe the application of micro-reversed-phase high-performance liquid chromatography (μ-RP-HPLC) for the separation and/or purification of polymerase chain reaction (PCR) products with detection accomplished using a miniaturized conductivity detector. The conductivity detector used two Pt wires and a bipolar waveform applied to the electrode pair from which the conductivity of the bulk solution could be measured. In the mobile phase used for the μ-RP-HPLC separation of the PCR product, the mass detection limit for herring sperm DNA using conductivity was found to be 11 ng. Efficient separation of the PCR amplicon from the other reagents present in the PCR cocktail was achieved in less than 4 min with a capacity factor of 2.5 and separation efficiency of 9.1·10 3 plates. The separation was carried out using reversed-phase ion-pair chromatography with a triethylammonium acetate ion-pairing agent.

Separation of the enzyme cofactor pyrroloquinoline quinone and three isomeric analogues by capillary electrophoresis with ion-pairing media

The enzyme cofactor pyrroloquinoline quinone (PQQ) was successfully separated from three closely related isomeric analogues by capillary electrophoresis with ultraviolet detection. Rapid and efficient separation of all four negatively charged isomers with baseline resolution was achieved by the addition of low concentrations (1–5 m M) of short chain tetraalkylammonium (TAA) salts to the capillary buffer. The TAA cations act as ion-pairing agents and promote differential migration of the isomers with only a minimal reduction in the electroosmotic flow. The effects of the TAA salt concentration and the alkyl chain length were examined. Detection limits of PQQ and its isomers were in the range of 7–15 μ M with mass detection limits of 98–210 fmol.

Analysis of solids by laser ablation and resonance-enhanced laser-induced plasma spectroscopy

An analytical technique based on resonance-enhanced laser-induced plasma spectroscopy was demonstrated. Pellets of potassium iodate containing trace amounts of sodium were ablated by a 532-nm laser pulse in air. After 30 ns, the plasma plume was intercepted by a 404.4-nm laser pulse to resonantly photoionize the potassium atoms in the vapor plume. The 589-nm emissions of the sodium were found to be significantly enhanced. The enhancement was shown to depend critically on the profile of the 532-nm beam as well as the spatial overlap of the two laser pulses. Using this double-pulse scheme, the mass detection limit for sodium was estimated to be about 200 pg, which was five times better than that obtained by using the 532-nm laser pulse alone.

Purity testing of organometallic catalysts by packed capillary supercritical fluid chromatography

A packed capillary column supercritical fluid chromatography system with flame ionization detection has been used for purity testing of candidates for homogeneous catalysis such as methyl tricarbonyl pentamethylcyclopentadienyl tungsten [Cp*W(CO) 3Me], methyl tricarbonyl cyclopentadienyl tungsten [CpW(CO) 3Me], tetramethyl pentamethylcyclopentadienyl iridium (Cp*IrMe 4), trimethyl (1,4,7-trimethyl-1,4,7-triazocyclononane) rhodium (CnRhMe 3), trimethylphosphine hydride dicarbonyl cyclopentadienyl molybdenum [η 5-CpMoH(CO) 2PMe 3] and triphenylphosphine hydride dicarbonyl cyclopentadienyl molybdenum [η 5-CpMoH(CO) 2PPh 3]. A mass limit of detection of 240 pg was found for η 5-CpMoH(CO) 2PMe 3 when using a 60-nl injection volume and pure CO 2 as mobile phase on a 5 μm Kromasil C 18 column. The stability of the catalysts in solution has been examined. After 24 h more than 70% of η 5-CpMoH(CO) 2PMe 3 and 50% of η 5-CpMoH(CO) 2PPh 3 had decomposed. Due to the instability of the compounds the purity testing had to take place rapidly after sample dissolution.

Continuous electrophoretic separations in narrow channels with postchannel derivatization and laser-induced fluorescence detection

The development of a novel technique utilizing a postchannel gap reactor for derivatization with channel electrophoresis and laser-induced fluorescence detection is described. The reactor is made by creating a gap in the top channel plate. The channel is constructed using 25-μm spacers with a gap of 20–30 μm. A derivatizing reagent is added to the gap and allowed to diffuse into the channel and reacts with the analytes as they migrate past the gap. Separations of amino acids and a protein have been accomplished with naphthalene dicarboxaldehyde/2-mercaptoethanol postchannel derivatization and laser-induced fluorescence detection. A linear response is reported for detection of each analyte tested. Mass detection limits obtained for the amino acids are in the attomole range while that for the protein transferrin is 110 zmol. © 2000 John Wiley & Sons, Inc. J Micro Sep 12: 279–284, 2000

A chip-scale universal detector for electrophoresis based on backscattering interferometry.

An on-chip detector based on backscatter interferometry has been developed to perform sub-nanoliter volume refractive index measurements. The detection system consists of a simple, folded optical train based on the interaction of a laser beam and an etched channel in a silica (glass) plate. This etched channel is composed of two radii joined by a flat portion which define a curved surface in the shape of a half cylinder in a silica (glass) plate. The backscattered light from the channel takes on the form of a high contrast interference pattern that contains information related to the bulk properties of the fluid located within the probe volume. Positional changes of the interference pattern extrema (fringes) allow for the determination of refractive index changes at the 10(-6) level in a detection volume of 188 x 10(-12) L. Under capillary electrophoresis (CE) conditions, the injected mass detection limits for small molecules with little native absorption ranges from 530 fmol (0.18 ng) for sucrose to 720 fmol (0.43 nanograms) for raffinose. Fluorescein was also used to evaluate the technique for universal CE and under further optimized conditions can be quantified at the 150 microM level. Separation performance for the solutes tested ranged from about 2300 to 15,500 plates or 61,000 to 400,000 N m-1. The results presented here indicate there is potential for using the simple optical train of backscattering interferometry for on-chip universal solute analysis.