Plant Reference Materials Research Articles

Determination of molybdenum in plant tissue by graphite furnace atomic absorption spectrophotometry (GFAAS)

Abstract The analysis of molybdenum in plant tissue using graphite furnace atomic absorption spectrophotometry (GFAAS) is described. The method involved wet digestion using a mixture of sulphuric, nitric and perchloric acids followed by a solvent extraction procedure. Molybdenum was extracted into di‐iso butyl ketone (DIBK) as the iron‐thiocyanate complex. The extract was then analysed for molybdenum by GFAAS. The results of analyses of the reference plant materials (orchard leaves and citrus leaves) of the National Bureau of Standards (NBS) compared very well with the certified values. Other types of plant tissue were also analysed and the results correlated well with those obtained by an alternative method.

Determination of total calcium, zinc, manganese, iron, magnesium and phosphorus in animal feeds and plant material using inductively coupled plasma emission spectrometry.

Six elements (Ca, Zn, Mn, Fe, Mg and P) were determined in diluted Kjeldahl digests of animal feeds using inductively coupled plasma emission spectrometry. The total concentrations found for each of the six elements, in a range of animal feeds, compared favourably with concentrations determined by alternative methods. There was a small but significant difference between calcium methods only. The same analytical conditions for feeds can be used in the analysis of plant materials, as results for five NBS plant reference materials were in good agreement with the assigned values. Precision estimates for a single sample assay were acceptable for a routine, first-action, regulatory method.

Distribution patterns of rare-earth elements in biological materials evaluated by radiochemical neutron activation analysis

This study deals with the quantitative determination of eight REE's viz, La, Ce, Nd, Sm, Eu, Tb, Yb, and Lu as an Integral part of a post-irradiation chemical separation scheme for the determination of 14 trace elements in biological materials. REE values are given for NBS Orchard Leaves SRM 1571, NBS Bovine Liver SRM 1577 and Bowen's Kale, as well as for some other biological (reference) materials of plant, animal and human origin.

X‐RAY FLUORESCENCE ANALYSIS OF SULFUR AND PHOSPHORUS WITH A FUNDAMENTAL MATRIX CORRECTION CALCULATION

ABSTRACTA comparison of X‐ray and chemical analyses of phosphorus and sulfur standards of KH2PO4‐ and (NH4)2SO4‐cellulose was performed to determine the range of applicability of a numerical matrix correction technique. Over the range 0.1 — 1.0%, the X‐ray technique was accurate to within 8% for phosphorus and 17% for sulfur. At 0.03%, the X‐ray values are low by 17% or more. At 3.0% and 10.0%, particle size effects caused the values to be low by more than 17%. X‐ray analysis of pure sulfur and (NH4)2SO4 was accurate to within 13% and indicates the validity of the mathematical technique. Application was made to the analysis of wheat and standard reference plant materials.

Determination of iodine in plant material by a neutron-activation method

A method for the determination of trace amounts of iodine in dry plant material is described. The method is based on the radiochemical separation of iodine-128 using alkaline fusion of the sample in the presence of an iodine carrier, followed by isolation of iodine by a solvent extraction and a precipitation step. The precision of the method is about 5% at the 0.05 p.p.m. level and 10% at the 0.005 p.p.m. level of iodine. Results for two international reference plant materials are reported.

The determination of molybdenum in plants by an automated catalytic method

Molybdenum is determined by its catalytic effect on the liberation of iodine from the reaction between potassium iodide and hydrogen peroxide. The detection limit is 0·003 µg ml–1 of molybdenum. Interference from iron and tungsten can be overcome by addition of ammonium fluoride, but for the greatest precision and accuracy a preliminary separation of molybdenum as its benzoin α-monoxime complex is recommended. Molybdenum concentrations determined by the proposed method in some reference plant materials are presented.