Approximate equations for the properties of dry steam from a generalization of Callendar's equation

A generalization of Callendar's equation for dry steam is used to calculate density to ±0.5% and temperature to ±0.8°C from enthalpy and pressure over the range 50–200 bar and from saturation to 690°C. Minor rearrangement of the fundamental equation allows pressure to be calculated directly from density and enthalpy.     

Principal Components plots for exploratory investigation of reactions using ultraviolet-visible spectroscopy: application to the formation of benzophenone phenylhydrazone

The use of Principal Components plots in the exploratory investigation of reactions monitored by UV-Vis spectroscopy is described. The effects of different types of pre-processing (raw, mean-centred, and standardised) are illustrated. Four types of plot (scores versus time, loadings versus wavelength, scores versus scores, and loadings versus loadings) are considered. The approach is used to investigate the reaction between phenylhydrazine and benzophenone to give a hydrazone. Observable deviations from ideal behaviour indicate differential crystallisation of the product, and the presence of small quantities of an intermediate during the reaction. Additional information about the reaction is gained by comparing selected components from several batches. PCA is easily performed at- or on-line, and the information gained can be used to help decide upon a suitable harder model for further analysis.     

PRODUCTS OF CHLOROPHYLL PHOTODEGRADATION–1. DETECTION and SEPARATION

Abstract— The photodegradative fate of ¹⁴C-radiolabelled phaeophytin a adsorbed on hydrophobic particles in an aqueous suspension is followed. An approximate mass balance is made for the hydrophilic, hydrophobic and CO, fractions. In addition, components of the colourless hydrophilic fraction produced from photodegrading chlorophyll a, phaeophytin a, phaeophorbide a and chlorophyll b are detected and separated using reverse-phase ion-pair and ion-exclusion HPLC with UV detection. The increase in the hydrophilic molecules and the decrease in chlorophyll a are measured as the photodegradation proceeds.     

Solid-phase extraction and simultaneous spectrophotometric determination of trace amounts of Co, Ni and Cu using partial least squares regression

A novel sensitive and simple method for rapid extraction, preconcentration and determination of cobalt, nickel and copper as their 1-(2-pyridilazo)-2-naphthol (PAN) complexes using polytetrafluoroethylene filter as solid phase and multivariate calibration of spectrophotometric data is presented. The analytical wavelengths of 400-700 nm were chosen and the experimental calibration matrix for partial least squares (PLS) was designed with 21 samples of 5.90-41.25, 0.30-29.35 and 0.64-41.30 ng ml⁻¹ for cobalt, nickel and copper, respectively. The cross-validation method was used for selecting the number of components. The root-mean-square errors of predictions (RMSEPs) were between 0.48 and 1.37 ng ml⁻¹. In this work we could reach preconcentration factors of 100 or even higher by using polytetrafluoroethylene as solid phase which is cheap and can be used in a wide range of pH, flow rates and for many times. The proposed method was successfully applied to the simultaneous determination of Co, Ni and Cu in tap and pit water samples.