Determination of native folates in milk and other dairy products by high-performance liquid chromatography

Folates were measured in dairy products by high-performance liquid chromatography without prior sample clean-up. Detection limits for individual folates range from 0.3 to 7.3 ng/g. The folates were extracted from the sample matrix by adjusting the pH to 4.5 with acetic acid, centrifuging to remove precipitated proteins, and treating with conjugase to remove multiple polyglutamate residues. Folates were separated from other sample components using a reversed-phase column with a methanol-phosphate buffer (pH 6.8), and ion-pairing with tetrabutylammonium ion. Fluorescence was found to be the most useful detection technique. Fluorescence detection of reduced forms of the vitamin was achieved by post-column pH adjustment of the eluent with phosphoric acid, while the parent folic acid molecule required chemical oxidation with hypochlorite in order to obtain a fluorescent response.     

Summed sensitivity of active networks

In the letter, results previously obtained for the summed sensitivity of passive networks are extended to active networks containing voltage, current, transconductance and transresistance amplifiers.     

Efficient tree-generation method suitable for computer programming

A tree and 2-tree generation method which does not suffer from most of the common restrictions, and which is ideally suitable for programming for the digital computer, is described.     

Weak-Signal DPSK Detection in Narrow-Band Impulsive Noise

The weak-signal receiver for binary differential phase-shift keying (DPSK) in additive noise is derived, and its performance in terms of the error probability in the most general narrow-band impulsive (nonGaussian) noise model, Middleton's class A noise, is analyzed.     

Relaxation time measurements in zinc alloys

Relaxation times obtained by means of de Haas-van Alphen measurements have been investigated in dilute alloys ofZnMn andZnAg. In both series of alloys measurements have been made on the needle, monster and lens sections of the Fermi surface. In theZnMn alloys, which exhibit a Kondo resistance minimum, the results analysed followingPaton andMuir [2] give a value for the s—d interaction constant,J, agreeing with this previous work. Similarly, an analysis followingNagasawa [4] givesJ values in agreement with that work. The situation posed by the existence of these two approaches, concerned as they are with opposite extreme limits, is discussed. In addition, the behaviour found in the other periods ofZnMn is discussed; here the effects seen on the needles are completely absent. A preprint of this paper was introduced during the discussion at the Conference on Electron Mean Free Paths by the Chairman of the Session, Dr.D. Shoenberg.     

2‐Amino­anilinium phosphite

The solid‐state structure of the title compound, alternatively called 2‐amino­anilinium hydrogen phosphonate, C₆H₉N₂⁺·H₂PO₃^?, shows the monoprotonated di­amine mol­ecule to be multiply hydrogen bonded to HPO₃H^? anions. There is no inter‐phosphite hydrogen bonding, contrary to previous solid‐state observations of the species.