A procedure for the determination of lead in green vegetables at concentrations down to 1 microgram/kg.

An accurate and highly sensitive dry ashing/graphite furnace atomic absorption spectrometry (GFAAS) procedure has been developed for the measurement of lead in green vegetables. The accuracy of the method was established by analysis of standard reference materials and confirmed by isotope dilution using an inductively coupled plasma-mass spectrometer (ICP-MS). The limit of detection (wet weight) of the technique is 1-3 micrograms/kg with relative standard deviations ranging from 6% for a sample of kale containing 500 micrograms/kg to 20% for cabbage containing 3.

An investigation of apparent total N-nitroso compounds in beer.

The concentration of apparent total N-nitroso compounds (ATNC) in beer has been investigated using a group-selective procedure based on chemical denitrosation with hydrogen bromide and chemiluminescence detection of the released nitric oxide. In a survey of samples of 40 brands of beer and lager, detectable levels of ATNC were present in 17 samples at concentrations of 20-100 micrograms N-NO/kg in 11 and 100-500 micrograms N-NO/kg in six. To determine the origin of ATNC in beer the production of a commercial batch was examined in detail.

Characterization studies on insoluble total N-nitroso compounds in bacon adipose connective tissue.

Enzymic hydrolysis was employed to solubilize 35% of the total N-nitroso compounds associated with bacon adipose connective tissue. Size exclusion chromatography of the digest showed that 95% of the solubilized N-nitroso compounds had molecular weights equivalent to those of di-, tri- and tetrapeptides. The likely identity of these compounds is discussed in the light of their extractability from acidified solution into ethyl acetate and their thermal and pH stability.

N-Nitrosopyrrolidine formation in bacon.

Evidence is presented that the likely major amine precursors to N-nitrosopyrrolidine in cooked bacon are free proline in the adipose tissue and to a lesser extent, collagenous connective tissues. A model system in which animal lipid is replaced with hydrogenated vegetable oil is described and used in investigating the potential role of prolyl derivatives as precursors to N-nitrosopyrrolidine.

Comparison of trace element solubility from food items treated separately and in combination.

Solubility of trace elements from various foods (beef, soya, crab, wholemeal and white bread) is assessed with various extractants, at different pH's and after enzyme treatment. Simple extractants do not solubilise trace elements to the same degree as when they are released after digestive enzyme action. Enzymic action can change the nature of the soluble species as well as their amount.