Matrix-isolation-FTIR spectroscopy with an integrating sphere

The use of an integrating sphere for the measurement of absorption spectra of thin films is described. The thin film (for example a rare gas matrix) is grown directly on the inside surface of the sphere. Multiple reflections inside the integrating sphere lead to significant enhancement of weak absorptions of the film, increasing the sensitivity of such measurements.     

Determination of aflatoxins in food products by chromatography.

Several chromatographic methods for the determination of aflatoxins in agricultural and food products are reviewed. During the past two decades, identification and determination of aflatoxins were done by thin-layer chromatography (TLC) because it was easy, fast and inexpensive. However, high-performance liquid chromatography (HPLC) using fluorescence detection is now the method of choice for determining aflatoxins and is also growing in popularity for their identification. The reasons for selecting HPLC over TLC can be summarized as the ability to analyze for a wide variety of compounds, including compounds that are easily degraded by heat, light or air, the ease of adaptation to confirmatory procedures, the potential for automation and the dramatic improvement in instrumentation, including the development of increasingly sensitive fluorescence and electrochemical detectors and short, high-resolution, reversed-phase columns.     

The role of kinetic energy in chemical binding

The wavefunctions and various partitions of the energy are examined for a variety of small molecules (H₂, H₃, H₄, HeH, HeH₂, He₂, LiH, and BH) in order to isolate the factors crucial for bond formation. We find that a natural partition of the energy leads to the conclusion that the crucial factor is the exchange, or nonclassical, part of the kinetic energy, T ^x. The change in T ^xupon pushing the atoms towards one another is the dominant term in the binding energy; it is negative when the resulting molecule is stable and positive when it is unstable. We show that T ^x is related to the interference kinetic energy considered by Ruedenberg.

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Zusammenfassung Die Wellenfunktionen und verschiedene Zerlegungen der Energie werden für eine Reihe kleiner Moleküle untersucht (H₂, H₃, H₄, HeH, HeH₂, He₂, LiH und BH), um die Faktoren zu finden, die für die Bindungsbildung ausschlaggebend sind. Die natürliche Zerlegung der Energie läßt die Folgerung zu, daß der bestimmende Faktor der Austauschanteil T ^x(oder nichtklassische Anteil) der kinetischen Energie ist. Die Änderung von T ^xbeim Zusammenführen der Atome ist der dominierende Term für die Bindungsenergie; er ist negativ, wenn das resultierende Molekül stabil ist, und positiv, falls es instabil ist. Es wird gezeigt, daß T ^x im Zusammenhang zum Wechselwirkungsanteil der kinetischen Energie nach Ruedenberg steht.

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Partially supported by a grant (GP-15423) from the National Science Foundation. This paper is based on a portion of the PhD thesis (California Institute of Technology, 1970) by CWW.

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National Science Foundation Predoctoral Trainee.

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Alfred P. Sloan Foundation Research Fellow.

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Contribution No. 3917.     

Quantitation of the novel anticonvulsant remacemide in rat and dog plasma and urine: application of the plasma methodology to measure the plasma protein binding of remacemide.

Sensitive and selective methods have been developed for quantitation of the novel anticonvulsant remacemide in rat and dog plasma and urine. The methods employed liquid-liquid extraction (urine) or ion-exchange solid-phase extraction (plasma), with an internal standard, followed by high-performance liquid chromatography with ultraviolet detection. The detection limit for both methods was 10 ng/ml. Overall accuracy was 0.00% for plasma and -1.4% for urine with a precision of 6.04 and 3.87% for plasma and urine, respectively. The standard curves were linear for both plasma and urine over a wide concentration range (9.96-2490 ng/ml). The plasma method was also applied to measurement of in vitro plasma protein binding of remacemide in rat, dog and human plasma.     

A SIFT ion-molecule study of some reactions in Titan's atmosphere. reactions of N(+), N(2)(+), and HCN(+) with CH(4), C(2)H(2), and C(2)H(4)

The results of a study of the ion-molecule reactions of N(+), N(2)(+), and HCN(+) with methane, acetylene, and ethylene are reported. These studies were performed using the FA-SIFT at the University of Canterbury. The reactions studied here are important to understanding the ion chemistry in Titan's atmosphere. N(+) and N(2)(+) are the primary ions formed by photo-ionization and electron impact in Titan's ionosphere and drive Titan's ion chemistry. It is therefore very important to know how these ions react with the principal trace neutral species in Titan's atmosphere: Methane, acetylene, and ethylene. While these reactions have been studied before the product channels have been difficult to define as several potential isobaric products make a definitive answer difficult. Mass overlap causes difficulties in making unambiguous species assignments in these systems. Two discriminators have been used in this study to resolve the mass overlap problem. They are deuterium labeling and also the differences in reactivities of each isobar with various neutral reactants. Several differences have been found from the products in previous work. The HCN(+) ion is important in both Titan's atmosphere and in the laboratory.     

Performance characteristics of analytical methods-IV

Sources of systematic errors in analytical results are discussed, and suggestions are made for the investigation and reporting of such errors when characterizing the performances of analytical methods. The four types of error considered arise from: (1) blank determinations, (2) calibration, (3) differences in the efficiencies with which different forms of the determinand are measured, and (4) interferences. The comparison of results with accepted values of standard samples or with the results obtained by standard methods is also discussed.     

An automatic controlled-potential coulometer

The design and operation of an automatic controlled-potential coulometer is described. It was primarily designed for use with mg quantities of uranium, neptunium and plutonium but can in principle be used on any element possessing more than one valency state in solution. It is capable of an accuracy and precision of ±0.25% and can analyse up to 20 samples on a set programme without operator attention.     

Dioxygenyl salts containing doubly charged mononuclear counterions

Evidence is presented for the existence of (O₂⁺)₂MF₆^2?(M=Ni,Mn) salts. These salts are marginally stable up to about 10°C and are characterized by an OO stretching frequency of about 1805 cm^?1.     

Conformational analysis3̄CXXIV: The conformation of ring A in the 4,4-dimethyl-3-androstanone system. The crystal structure of 4,4-dimethylandrostan-3-on-17β-yl benzoate

Molecular mechanics calculations indicate that the deformed chair and twisted-boat conformations are similar in energy for a 4,4-dimethyl-3-keto steroid. Earlier dipole moment work on such compounds is discussed. The crystal structure of 4,4-dimethylandrostan-3-on-17β-yl benzoate has been determined. The crystals are orthorhombic, P2₁2₁2₁, a = 17.096 (2), b = 22.136 (e), c = 6.217 (1) A. The structure was solved by direct methods and refined by least squares to R ? 0.039, R_XXX = 0.038, based on 2168 observed reflections. Ring A is shown to exist in a chair form, deformed as indicated by the calculations.     

THE EFFECT OF PORPHYRIN PHOTOSENSITIZERS ON THE TOXICITY OF l,3-BIS(2-CHLOROETHYL)-1- NITROSOUREA IN C57BL/6J MICE

Abstract The most widely used agents for photodynamic therapy are the porphyrin photosensitizers. It has been shown that hematoporphyrin derivative (HpD) can cause murine marrow hypercellularity and splenic hypertrophy. We have examined the effect on survival and marrow cellularity of high dose l,3-bis(2-chloroethyl)-l-nitrosourea (BCNU) after HpD or dihematoporphyrin ether (DHE) pretreatment in C57BL/6J mice.
The lethal toxicity of the LD_S0+ 10% dose of BCNU (60 mg kg⁻¹) was significantly reduced by pretreatment with HpD when the HpD was administered at least 3 days prior to the BCNU. HpD administered 1 or 2 days prior to BCNU or after BCNU had no effect. The percent death rate was reduced from 80 to 0% when HpD was administered 7 and 5 days prior to BCNU.
No alteration of the lethal toxicity rate of BCNU at doses of 80 mg kg⁻¹ were identified with DHE pretreatment although some increase in median survival was noted in two groups. Some reduction in lethal toxicity was noted when 60 mg kg⁻¹ BCNU was used and the pretreatment dose of DHE was 10 or 25 mg kg⁻¹ given twice 3 days apart. Furthermore, a significant reduction of BCNU induced marrow cell depletion was found when low doses of DHE were used as pretreatment. High doses of DHE resulted in marrow depletion. Both HpD and DHE altered the toxicity of BCNU.
Should porphyrin photosensitizers, which alone have little toxicity, prove to protect against nitrosourea toxicity then an important dose limiting factor (myelotoxicity) could be altered if not reduction in the tumouricidal activity occurs.