Textiles, fibres and leather

There is interest in trace metal levels in both natural and synthetic fibres and fabrics but perhaps most interest is in synthetic fibres as these may contain residues of catalysts, treatments or stabilising agents. Reviews have been published of trace-metal analysis of rayon, polyamide, polyester and polypropylene fibres [178] and of cotton fabrics, especially for flame 

Trace metals can be leached out of some natural fibres. To determine copper in webbing, rope and cotton duck, Simonian [184] warmed, to near boiling, 2—3 g fabric with 80—90 ml of 0.5 M hydrochloric acid. The sample was filtered and made up to 200 ml before aspiration into an air/acetylene flame. 

Metal salts may be used in the treatment of wool. Flame methods for the determination of aluminium [185], barium, chromium, copper, mercury, strontium, tin, zinc [186] and zirconium [187] in wool have been published. Standard additions to wool cleaned by soaking and washing it with disodium EDTA (800 ml of 0.5 M for 30g wool with soaking for 3 days and double washing) was used as the calibration technique. This compensated for interferences from hydrochloric acid and amino-acids. The samples were equilibrated to a constant humidity for 24 h and then 0.3 g sealed with 5 ml of constant boiling point hydrochloric acid in a glass tube. The tubes were placed in an oven at 110UC for 20 h. The nitrous oxide/acetylene flame was used for the determination of aluminium and zirconium. Sulphate, phosphate, citrate and silicate have been found to interfere in the determination of titanium and zirconium in fire-proofed wool [188], These flame 

The long established use of chromium salts in the tanning of leather has been reflected in interest in the determination of chromium in leather extracts. Generally the leather is leached with acids or complexing agents such as oxine to remove the metal salts. Della Monica and McDowell [189] recommended leather strips be air dried at 80°C for 24 h and ground to pass a 10 mesh screen. The powder was vacuum dried at 70°C for 16 h and then 100 mg refluxed with 25 ml 2M hydrochloric acid. The filtered acid was aspirated into a flame. For chromium a fuel-rich air/acetylene flame or a nitrous oxide/acetylene flame is to be recommended. 

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