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The use of organ-on-a-chip (OOC) devices is a promising alternative to existing cell-based assays and animal testing in drug discovery. A rapid prototyping method with polydimethylsiloxane (PDMS) is widely used for developing OOC devices. However, because PDMS tends to absorb small hydrophobic molecules, the loss of test compounds in cell-based assays and increases in background fluorescence during observation often lead to biased results in cell-based assays. To address this issue, we have fabricated a glass-based OOC device and characterized the medium flow and molecular absorption properties in comparison with PDMS-based devices. Consequently, we revealed that the glass device generated a stable medium flow, restricted the absorption of small hydrophobic molecules, and showed enhanced cell adhesiveness. This glass device is expected to be applicable to precise cell-based assays to evaluate small hydrophobic molecules, for which PDMS devices cannot be applied because of their absorption of small hydrophobic molecules.

Coffee is one of the most popular beverages in the world, however, little information is found regarding the mineral composition of commercial roasted and ground coffees (RG) and its correlation with organic bioactive compounds. 21 commercial Brazilian RG coffee brands - 9 traditional (T) and 12 extra strong (ES) roasted ones - were analyzed for the Cu, Ca, Mn, Mg, K, Zn, and Fe minerals, caffeine, 5-caffeoylquinic acid (5-CQA) and melanoidins contents. For minerals determination by flame atomic absorption spectrometry (FAAS), the samples were decomposed by microwave-assisted wet digestion. Caffeine and 5-CQA were determined by liquid chromatography and melanoidins by molecular absorption spectrometry. The minerals and organic compounds contents association in RG coffee was observed by a principal component analysis. The thermostable compounds (minerals and caffeine) were related to dimension 1 and 2, while 5-CQA and melanoidins were related to dimension 3, allowing for the T coffees segmentation from ES ones.

For further understanding of the molecular absorption mechanisms of photothermal conversion by coordination compounds, two newly prepared xanthene-functionalized silver(I) complexes, [Ag2(X9A)2(dppm)2] (1) (where dppm = bis(diphenylphosphino)methane and X9A = 9H-xanthene-9-carboxylato(-1)) and [Ag4(X9A)4(dppm)2]·6CH3OH (2), have been isolated and structurally characterized. We report here the syntheses, crystal structures, characterizations by various spectroscopic (IR, UV–Vis, powder XRD) techniques, as well as photothermal conversion performance of 1 and 2. Their X-ray crystal structures reveal that 1 is a binuclear silver(I) coordination compound bridged by two dppm molecules with two monodentate 9H-xanthene-9-carboxylato(-1) ligands, and 2 can be described as the dimer of 1 bridged by two 9H-xanthene-9-carboxylato(-1) anions in the μ3-η1,η2 coordination mode. Their photothermal conversion experimental results give new insight into understanding the molecular mechanisms for improving the performance of photothermal conversion molecular materials.

Total fluorine concentrations in some fish species and seafood such as mussels, squid (calamary), and shrimp were determined using the molecular absorption of calcium monofluoride (CaF) gen...

Phenolic compounds, including nitro- and chlorophenols, in neutral aqueous solutions react with diazotized sulfanilic acid. The molecular absorption coefficients of azo dyes obtained from various phenols in the range 360‒380 nm are quite close, which ensures the determination of the total concentration of phenols as C6H5OH. Under optimized conditions, the systematic errors in the analysis of model mixtures did not exceed 30 rel. %. They may be due to either the difference in molar absorption coefficients, or the delayed formation or instability of some azo dyes, and also due to the influence of reducing agents and arylamines. The procedure may become a good alternative to the determination of the phenolic index of sewage waters by the reaction with 4-aminoantipyrine.

A rapid liquid chromatographic (LC) method was developed for simultaneous determination of 7 pyrethroid insecticides in beans. Residues were extracted from beans with acetone, followed by partition with ethyl acetate/cyclohexane (1+1) and clean up by gel-permeation chromatography. LC separation was performed on a LiChrospher 100 RP-18 column using acetonitrile/water (8+2) as mobile phase. The pesticides were detected by molecular absorption spectrophotometry at 212 nm. Recoveries of 7 pyrethroids fortified at 0.010; 0.10; 1.0 mg kg-1 levels were within the range 71-105 %. Advantageous features of this method are: the quantification limits, which were between 0.004 and 0.011 mg kg-1, and the simplicity in the sample treatment, which requires less clean-up if compared with the GC-ECD determination. No residues of pyrethroids were detected in 48 bean samples commercialized in São Paulo City during 2008.

The purpose of this study was to analyze and quantify spectral parameters, the absorption bands, specifically in the uv-visible region of some N-oxide ligands. From the spectra, the area under the absorption band, the molar absorptivity, the integrated absorption coefficient and the oscillator strength by the Gaussian approximation method were calculated for each of them, using the proposed evaluation by Drago and Figgs. According to the obtained results, it can be concluded that the heterocyclic compounds studied absorb very well electromagnetic radiation in the ultraviolet region. For the ligands QUI-NO and NIC-NO it was observed that there are two types of bands, primary and secondary, being transitions of type π → π * and n → π*, respectively. For DITBIS-NO, there was only one primary band (transition 1) and two additional shoulders, which had the highest observed absorbance coefficient. These ligands are expected as potential electron donors in complex systems whose purpose is to change the energy levels of the electronic system in order to promote a better utilization of the absorbed energy and therefore a better efficiency.

One of the problems for quantifying the amount of silicon available by molecular absorption is the elimination of chemical interference caused by available phosphorus. The aim of this work was to evaluate different organic acids in eliminating the interference caused by phosphorus in the quantification of available silicon by molecular absorption. The experiments were conducted in the Soil laboratory of the College of Agricultural Sciences at the Universidad de Córdoba, Colombia. For this work, different acids such as tartaric, citric, oxalic and malic were evaluated at two concentrations (0.8 and 1.33 mol L-1). Solutions containing silicon (1 mg L-1) and six concentrations of phosphorus were prepared (0.0, 0.2, 0.4, 0.6, 0.8 and 1.0 mg L-1). The quantification of silicon was conducted by molecular absorption spectrophotometry using a Perkin Elmer Lambda XLS + at 660 nm. The results were subjected to the LSD tests and contrasts using the R software (Development Core Team, version 3.2.2).The results indicated that the oxalic, citric and malic acids at both concentrations produced lower overestimation of silicon in the presence of the P concentrations 0.6, 0.8 and 1.0 mgL-1 than the tartaric acid, which is commonly used as a reference to remove the P interference. One of the problems for quantifying the amount of silicon available by molecular absorption is the elimination of chemical interference caused by available phosphorus. The aim of this work was to evaluate different organic acids in eliminating the interference caused by phosphorus in the quantification of available silicon by molecular absorption. The experiments were conducted in the Soil laboratory of the College of Agricultural Sciences at the Universidad de Córdoba, Colombia. For this work, different acids such as tartaric, citric, oxalic and malic were evaluated at two concentrations (0.8 and 1.33 mol L-1). Solutions containing silicon (1 mg L-1) and six concentrations of phosphorus were prepared (0.0, 0.2, 0.4, 0.6, 0.8 and 1.0 mg L-1). The quantification of silicon was conducted by molecular absorption spectrophotometry using a Perkin Elmer Lambda XLS + at 660 nm. The results were subjected to the LSD tests and contrasts using the R software (Development Core Team, version 3.2.2).The results indicated that the oxalic, citric and malic acids at both concentrations produced lower overestimation of silicon in the presence of the P concentrations 0.6, 0.8 and 1.0 mgL-1 than the tartaric acid, which is commonly used as a reference to remove the P interference.

Total sulfur concentrations in vinegars were determined using molecular absorption of carbon monosulfide (CS) determined with a high-resolution continuum source flame atomic absorption spectrometer. The molecular absorption of CS was measured at 258.056 nm in an air–acetylene flame. Due to non-spectral interference, as well as the different sensitivities to some sulfur compounds, all sulfur species were oxidized to sulfate using a HNO 3 and H 2 O 2 mixture and the analyte addition technique was applied for quantification. The limit of detection (LOD) and limit of quantification (LOQ) were 11.6 and 38.6 mg L −1 , respectively. The concentrations of sulfur in various vinegars ranged from ⩽LOD to 163.6 mg L −1 .

The ground-state classical path approximation is utilized to compute molecular absorption spectra in a mixed quantum-classical frame. To improve the description for high-frequency vibrational satellites, related quantum correction factors are introduced. The improved method is demonstrated for the Q(y),and Q(x)-bands of pheophorbide a. (C) 2015 Elsevier B.V. All rights reserved.

Detection and characterization of fluoride is an important part of understanding the benefits as well as the potential toxicity of fluoride in biotic and abiotic natural sources. Fluoride can have a detrimental effect on human health at high concentrations (>1.5 mg L−1), thus, it must be detected and quantitated. For this analytical methods play an important role. This review underlines the role of analytical methods in the detection and quantitation of fluoride. The review highlights a variety of analytical methods, for instance, inductively coupled plasma mass spectrometry (ICP-MS), atomic absorption spectrometry (AAS) and molecular absorption spectrometry (MAS), and electrochemical methods that have been applied in the determination of fluoride. The principles of these techniques in conjunction with their pros and cons, and their applications regarding the determination and detection of fluoride are discussed. The commonly used fluoride sensing methods, including fluorescence and colorimetric methods have also been discussed. We hope this review will promote the next generation approaches and application of innovative analytical methods for fluoride detection and quantification.

Observations of the frequencies of different rotational transitions of the methanol molecule have provided the most sensitive probe to date for changes in the proton-to-electron mass ratio, over space and time. Using methanol absorption detected in the gravitational lens system PKS B1830-211, changes in the proton-to-electron ratio over the last 7.5 billion years have been constrained to a fractional change less than 1.1e-07. Molecular absorption systems at cosmological distances present the best opportunity for constraining or measuring changes in the fundamental constants of physics over time, however, we are now at the stage where potential differences in the morphology of the absorbing systems and the background source, combined with their temporal evolution, provide the major source of uncertainty in some systems. Here we present the first milliarcsecond resolution observations of the molecular absorption system towards PKS B1830-211. We have imaged the absorption from the 12.2-GHz transition of methanol (which is redshifted to 6.45 GHz) toward the southwestern component and show that it is possibly offset from the peak of the continuum emission and partially resolved on milliarcsecond scales. Future observations of other methanol transitions with similar angular resolution offer the best prospects for reducing systematic errors in investigations of possible changes in the proton-to-electron mass ratio on cosmological scales., 8 pages, 3 figures, accepted for publication in MNRAS

The search for more suitable alternatives in analytical processes is a strategy to reduce environmental damages. The present study aimed to quantify the soil microbial biomass carbon (SMB-C), establishing a comparison between the methods involving quantification of SMB-C by titration of the samples with ferrous sulfate ammonia and molecular absorption spectrophotometry methods. This comparison was performed by two soil sample tests: (i) areas of grain crops with conventional management versus notill farming; and (ii) areas with distinct phytophysiognomies in the region southern Mato Grosso do Sul state (Cerrado and Semideciduous Forest). It was found that molecular absorption spectrophotometry was an efficient tool for the determination of soil microbial biomass carbon, allowing replacement of the titrimetric method. There were significant differences in the levels of SMB-C determined spectrophotometrically in relation to those determined by titration. However, for the levels of SMB-C determined by spectrophotometry to be compared with those determined by titration, the values must be corrected by the linear regression equation Y spectrophotometry = - 151.38 + 0.92532 * X titration . Key words : Potassium dichromate, soil quality, titration.

A high resolution spectrum of FTS sunspot umbra of NSO/Kitt Peak was used to conduct a search for the molecular absorption lines due to BeH, BeD and BeT isotopomers. Analysis led to estimates of identification of the molecular lines of bands A - X (0,0), (1,1) and (2,2) for BeH, A - X (0,0), (1,1), (2,2) and (3,3) for BeD and of A - X (0,0), (1,1) and (2,2) for BeT. Among the identified lines, those which are well resolved were selected for measurements to calculate equivalent widths. The values of effective rotational temperature T were estimated for bands A - X(1,1) and (2,2) of BeH, A - X(1,1) of BeD and A - X(2,2) of BeT to be 4228K, 4057K, 3941K and 3243K respectively.

Molecular absorption cells (5 cm-long, free-space coupled) underpin industry wavelength standards at the 0.1 pm (∼10 MHz) level. We address the challenge of fabricating very short, sealed photonic bandgap fibers with similar performance.

Photoemission results indicate that the initial adsorption of cobaltocene on Cu(1 1 1) at 150 K leads to molecular fragmentation, but with subsequent cobaltocene exposures, molecular absorption occurs. The molecularly adsorbed species is either adsorbed with only a fraction of molecules adopting a preferential orientation along the surface normal or adsorbed with the molecular axis away from the surface normal. This adsorption behavior is compared to nickelocene and ferrocene adsorption.

Nanoparticles of 1-phenyl-3-naphthyl-5-((dimethylamino)phenyl)-2-pyrazoline ranging from tens to hundreds of nanometers were prepared by the reprecipitation method. Their excitonic transitions responsible for absorption and emission, as compared with those of dilute solution, have been investigated as a function of nanoparticle size. We found that pyrazoline nanoparticles possess a special size dependence on their optical properties. As the nanoparticle size decreased, the molecular absorption peak of pyrazoline nanoparticles was observed to shift to the high-energy side due to size effect.

Based on the measurements of molecular absorption and resonance light scattering (RLS), the aggregation of Azur B (AB) was in a medium of pH ranging from 1.98 to 2.56 and ionic strength

The use of molecular absorption spectrometry for the determination of chloride in inorganic solid samples is described. The chloride is measured by monitoring the absorption of vaporised chlorine molecules. The liberation of chlorine is performed by adding concentrated sulphuric acid containing potassium permanganate. The effects of various components commonly present were studied and no serious interference was found. The accuracy was assessed by comparing the results using the proposed method with those obtained by other methods same as well as by artificial samples.

石油化学製品に含まれる有機塩素化合物は製品の安定性に悪影響を及ぼすため,その濃度管理は重要である。そこで,一塩化アルミニウム分子吸光法を用いる石油化学製品中の有機塩素化合物の定量法を検討した。アルミニウム,ストロンチウム,コバルトの硝酸塩混合物をマトリックス修飾剤として添加した。本法における塩素10μg ml-の試料の定量値の相対標準偏差(n=5)は4.1%であった。また,検出限界(空試験値の標準偏差の3倍相当)は0.1μg ml-1であった。石油化学製品として,ブテンのオリゴマー化で得られる製品について,本法を用いて塩素を定量した結果と,既存の微量塩素分析装置を用いて定量した結果は良く一致した。

The new approach for the determination of sulphur in foods was developed, and the sulphur concentrations of various fresh and dried food samples determined using a high-resolution continuum source flame atomic absorption spectrometer with an air/acetylene flame. The proposed method was optimised and the validated using standard reference materials, and certified values were found to be within the 95% confidence interval. The sulphur content of foods ranged from less than the LOD to 1.5mgg(-1). The method is accurate, fast, simple and sensitive.

Observing inversion lines of ammonia (NH3), complemented by rotational lines of NH3 and other molecular species, provides stringent constraints on potential variations of the proton-to-electron mass ratio. While a limit of one part per million is derived for a lookback time of 7 billion years, nearby dark clouds might show a statistically significant variation of order 20-30 parts per billion, possibly being related to chameleon fields. The detection of radio-loud quasars with strong molecular absorption lines at redshifts z > 1 as well as the identification of a larger sample of nearby dark clouds with exceptionally narrow lines (

A procedure for the determination of ammonium is described, based on its transformation into ammonia gas and subsequent measurement by UV-visible molecular absorption spectrometry at 194 nm. Two different procedures for generating the ammonia are proposed, using NaOH solution and solid NaOH, respectively. After generation conditions for both procedures had been optimized, better sensitivity was observed with solid NaOH. In these conditions, the method showed two ranges of linear response: from 1 to 100 μg and from 100 to 400 μg of ammonium. Finally, we determined ammonium in wine samples. Preliminary studies indicated that the only observable interfering species was ethanol, which could be eliminated by subjecting the sample to vacuum evaporation until nearly dry. This process also increased the sensitivity of the method by as much as ten times. The values obtained from three different wine samples yielded results within the range of the concentration obtained by other authors. The recovery of ammonium added to the wine samples was around 95%.

We report the detection of the ground state N,J = 1,3/2 → 1,1/2 doublet of the methylidyne radical CH at ~532 GHz and ~536 GHz with the Herschel/HIFI instrument along the sight-line to the massive star-forming regions G10.6-0.4 (W31C), W49N, and W51. While the molecular cores associated with these massive star-forming regions show emission lines, clouds in the diffuse interstellar medium are detected in absorption against the strong submillimeter background. The combination of hyperfine structure with emission and absorption results in complex profiles, with overlap of the different hyperfine components. The opacities of most of the CH absorption features are linearly correlated with those of CCH, CN, and HCO+ in the same velocity intervals. In specific narrow velocity intervals, the opacities of CN and HCO+ deviate from the mean trends, giving rise to more opaque absorption features. We propose that CCH can be used as another tracer of the molecular gas in the absence of better tracers, with [CCH]/[ H2] ~ 3.2±1.1×10-8. The observed [CN]/[CH], [CCH]/[CH] abundance ratios suggest that the bulk of the diffuse matter along the lines of sight has gas densities nH = n(H) + 2n(H2) ranging between 100 and 1000 cm-3. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.Appendices A and B (pages 6, 7) are only available in electronic form at http://www.aanda.org

Recovery of organic fluorine by direct aluminum monofluoride molecular absorption spectrophotometry, following injection of samples into the graphite furnace and use of sodium fluoride standards, varies from 0 to 100% from compound to compound depending on the compound's volatility and the mechanism of thermal decomposition. This problem has now been overcome by employing standards made from the very same fluorochemical that is present in the sample. This approach is applicable to samples containing only 1 known fluorochemical. Some industrial applications of this technique that meet the needs of quality control, industrial hygiene policies, and certain U.S. Food and Drug Administration regulations are described.

We present the first detections of the 3um water ice and 3.4um amorphous hydrocarbon (HAC) absorption features in z~2 ULIRGs. These are based on deep rest-frame 2-8um Spitzer IRS spectra of 11 sources selected for their appreciable silicate absorption. The HAC-to-silicate ratio for our z~2 sources is typically higher by a factor of 2-5 than that observed in the Milky Way. This HAC `excess' suggests compact nuclei with steep temperature gradients as opposed to predominantly host obscuration. Beside the above molecular absorption features, we detect the 3.3um PAH emission feature in one of our sources with three more individual spectra showing evidence for it. Stacking analysis suggests that water ice, hydrocarbons, and PAH are likely present in the bulk of this sample even when not individually detected. The most unexpected result of our study is the lack of clear detections of the 4.67um CO gas absorption feature. Only three of the sources show tentative signs of this feature and at significantly lower levels than has been observed in local ULIRGs. Overall, we find that the closest local analogs to our sources, in terms of 3-4um color, HAC-to-silicate and ice-to-silicate ratios, as well as low PAH equivalent widths are sources dominated by deeply obscured nuclei. Such sources form only a small fraction of ULIRGs locally and are commonly believed to be dominated by buried AGN. Our sample suggests that, in absolute number, such buried AGN are at least an order of magnitude more common at z~2 than today. The presence of PAH suggests that significant levels of star-formation are present even if the obscured AGN typically dominate the power budget., 39 pages, 14 figures, accepted for publication in ApJ

A method of simultaneous determination of inorganic As(III) and As(V) is described, which involves arsine generation, measurement of the molecular absorption of arsine in the gas phase at 190 nm and quantification of As(III) and As(V) based on different heights and areas of absorbance versus time profiles of arsine generated from both inorganic species. The limits of detection were 0.5 μg of As(III) and 3 μg of As(V) in a sample volume of 1 ml. An interference study for both species was made and the method was applied to the determination of As2O3 and As2O5 in a standard glass sample.

A waveguide carbon dioxide laser is stabilised on the Lamb-dip of a Stark-tuned molecular absorption and offset locked. Further an acousto-optic modulator is used to produce a single sideband of the CO2 laser. The infrared-infrared double-resonance signal in formic acid is observed and dipole moments of v 6 and v 8 vibrational states are determined.

Uric acid (UA) is determined using the UV–vis molecular absorption properties of peroxidase (HRP). The method as a whole involves UA oxidation in the presence of uricase (UOx), giving H2O2. The H2O2 then reacts with HRP forming the compound I species which returns to its initial form by reaction with UA and intramolecular reduction. The molecular absorption changes of HRP at 420 nm during the reaction enable the UA to be determined. A mathematical model relating the analytical signal to UA, UOx and HRP has been developed and experimentally validated. The possibility of carrying out both enzymatic reactions sequentially or simultaneously is discussed, the latter option producing better analytical performances. The method permits UA determination in the range 1.5 × 10−6–4.0 × 10−5 M, with an R.S.D. of about 3% (n = 5, 1.5 × 10−6 M UA). It has been applied to analyte determination in synthetic serum samples.

Using the VLA and NRAO 140 � telescopes we observed the λ1.3 cm (1, 1) and (2, 2) lines of NH3 in absorption and emission toward the compact extragalactic continuum sources NRAO150 (B0355+508) and 3C 111 (B0415+379). These sources are occulted by some seven local diffuse and translucent clouds showing molecular absorption in OH, CO, HCO + and C2H: for the four features having NH3 absorption, we find rotational excitation temperatures 18–24 K, suggesting kinetic temperatures of at least 25–30 K. The abundance ratio N(NH3)/N(HCO + ) is comparable to values quoted for the cyanopolyne peak in TMC-1 (i.e., 2.5) in three of four cases where NH3 was seen. For clouds with higher column density N(HCO + ) > 10 12 cm −2 ,t he NH 3 column density N(NH3) is well correlated only with N(CS) (� N(NH3)/N(CS) �≈ 1.0) and N(H2CO) (� N(NH3)/N(H2CO) �≈ 0.4). N(H2CO) is well correlated with N(NH3 )a ndN(CS) (� N(H2CO)/N(CS) �≈ 2.3) and the H2CO abundance relative to other species is like TMC-1, with (� N(H2CO)/N(HCO + ) �≈ 2.3).

Mid-infrared diode lasers (/spl lambda/=1.7-5 /spl mu/m) fabricated from GaInAsSb/AlGaAsSb heterostructures grown on GaSb substrates have been under development at Lincoln Laboratory for the past five years. Performance breakthroughs have been achieved by employing strained multiple-quantum-well active regions, and cw output power as high as 1.3 W has been obtained at room temperature near 2 /spl mu/m. These lasers, either employed as direct sources or for pumping of solid state lasers, can be used for a variety of applications exploiting the characteristics of this spectral range, which is eyesafe and includes important atmospheric transmission bands and molecular absorption lines. >

A method is described for determining sulphite by SO2 generation and UV-visible molecular absorption spectrometry with diode-array detection. The molecular absorption maximum of SO2 appears at 198 nm. The parameters affecting generation (particularly those relating to the kinetics of the process) and determination are optimized; under the optimum conditions found, only a 30 s preconcentration time is necessary. The linear response range is between 10 and 1000 μg ml−1 of SO 3 2− , the RSD is 3.5% and the detection limit is 3.2 μg ml−1. The effect of different species on the SO2 signal is also studied. The method is applied to the determination of SO2 in air samples.

In this paper, we study theoretically and experimentally the coherent control of non-resonant two-photon transition in a molecular system (Perylene dissolved in chloroform solution) by shaping the femtosecond pulses with simple phase patterns (cosinusoidal and π phase step-function shape). The control efficiency of the two-photon transition probability is correlated with both the laser field and the molecular absorption bandwidth. Our results demonstrate that, the two-photon transition probability in a molecular system can be reduced but not completely eliminated by manipulating the laser field, and the control efficiency is minimal when the molecular absorption bandwidth is larger than twice the laser spectral bandwidth.

The determination of P by means of evaluation of PO molecular absorption bands in the air–acetylene flame is an uncomplicated, reliable, and rapid analytical method, as stated by the authors in a preceding paper. However, the presence of Mg, and especially of Ca, in the sample solution causes strong suppression of the PO absorption. This is due to the formation of calcium and magnesium phosphates, which are thermally so stable that they are not decomposed in a medium temperature air–acetylene flame. Fortunately, the suppression effect can be completely eliminated by the addition of Ti to the sample, whereby titanates of Ca and Mg are formed in the flame. As these titanates are thermally more stable than the corresponding phosphates, the phosphate is released. The analytical performance of the method was verified by analyses of standard reference materials containing high concentrations of Ca. Good precision and accuracy were achieved.

Total fluoride (F) concentrations in dental plaque obtained from children aged 4-5yr and 14-15yr in F area (0.3-1.8ppm F in natural drinking water) and non F area (under 0.1ppm F) were determined by the AlF molecular absorption spectrometry. The logarithmic normal distribution was showed in F concentration of dental plapue. The geometric means of F concentration in plaque obtained from the non F area were 25.7ppm (4-5yr) and 18.1ppm (14-15yr) as dry weight. The contents of plaque in F area, contrary, were significantly higher than those in non F area (4-5yr: 54.4ppm, 14-15yr: 24.3ppm).The plapue F from 4-5yr group was significantly higher than that from 14-15yr group in both areas. A possible explanation for the different levels of F in dental plaque from two age groups might be due to the difference of plaque quality such as plapue age.The present experiments confirmed the higher levels of F in dental plaque were acquired from naturaly fluoridated drinking water.

A rapid determination of Ammonia in urine has been achieved. Gaseous ammonia is evolved by alkylifying urine with a saturated solution of K2CO3 at 80°C followed by separation of the gas phase and measurement of characteristic absorption at 197.2 nm. The linear range of the method is between 0 and 200 μg NH3/ml. The recovery of ammonia from spiked urine samples is 106.5%. Typical results obtained on five samples from healthy subjects are presented and good agreement with a reference method is shown. Automation has been achieved by the use of a mechanical sampler, a heating bath and a peristaltic pump.

The frequencies of two infrared lasers stabilized by molecular absorption lines have been measured by using a frequency-synthesis chain extending down to the caesium frequency standard. The measured values are 29,477,160,852+or-16 kHz for the R(32), 10.17 mu m transition of CO2 and 88,376,181,608+or-43 kHz for the F2(2) component of the P(7) transition in the nu 3 band of methane. These values are in good agreement with previous determinations and are obtained using the value 32,176,079,482 kHz measured previously for a stabilized CO2 laser operating on the R(12), 9.3 mu m transition.

Indirect atomic absorption spectrometric and spectrophotometric methods for the determination of tungsten have been developed based on the precipitation of lead(II) tungstate and the measurement of the excess lead(II) in the supernate. The optimum Concentration ranges are approximately 3–30 ppm of tungsten on the basis of sample solution.

Absorption by atmospheric NO3 at 6620A has been detected at night using the moon as the light source. The absorption exhibits a

Zusammenfassung Eine direkte Bestimmungsmethode von Fluoridspuren durch Messung der GaF-MA in einem Graphitrohratomisator wird beschrieben. Die apparativen Bedingungen (Kompensation der unspezifischen Absorption, Temperaturen der Veraschungsphase und der Phase der Verdampfung/Molekulbildung) wurden optimiert. Der Einfluβ der Ga 3+ - und Na + - Konzentration und der Konzentration verschiedener Sauren auf die Bestimmung wurde untersucht und diskutiert. Hohere Konzentrationen an Ga 3+ -Ionen bewirken eine hohere Konzentration der GaF-Molekule im Plasma des Graphitrohres. Hohere Na + -Konzentrationen bewirken einen geringeren Verlust an HF wahrend der Trocknungsphase. Die Nachweisgrenze (3 s) ist 1,6 ngF - /10 μl; die reziproke Empfindlichkeit ist 0,8 ng F - /10 μl bezogen auf 0,01 E. Der Einflu/GB von Cl - -, Br - -, J - -, SO 4 2- -, BO 3 3- -, SiO 3 2- -, Li + -, K + -, Be 2+ -, Mg 2+ -, Ca 2+ -, Al 3+ -, In 3+ -, Zn 2+ -, Cd 2+ - und Fe 3+ -Ionen auf die Bestimmung wurde untersucht.

Molecular absorption with electrothermal volatilization in a graphite tube. Part 3. A study of the determination of fluoride traces by A1F, GaF, InF and T1F molecular absorption . The use of the molecular absorption of thermally stable molecules such as AlF, GaF, InF and TlF, generated in a normal graphite tube, is assessed for determinations of fluoride. Optimal experimental conditions are discussed. The presence of Na + ions increases the signals. The influence of Na + ions and of other substances is discussed. The sensitivities (0.01 absorbance) are 0.4 ng F - for AlF, 0.8 ng F - for GaF, and 1.1 ng F - for InF.

A method for antimony determination is described comprising hydride generation and transport into a flow-cell placed in a UV-visible molecular absorption spectrophotometer with diode-array detection. Nitrogen is employed as carrier gas. The measurement is performed at 198 nm. The calibration curve is linear from 3 to 440 μg/ml of antimony. The method was successfully applied to the analysis of PVC.