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The aim of this work is the study of cysteine by its derivative form. Cysteine derivation is done by Edman degradation and we obtain the phenylthiohydantoin of cysteine. Edman degradation is one of the most usual procedures for sequentate proteins. From this reaction, the phenylthiohydantoin amino acid derivative (PTH‐amino acid) from the N‐terminal one is obtained, leaving the new amino terminus for the next degradation cycle. To identify the produced PTH‐derivative, a square‐wave cathodic stripping voltammetry method is developed. In this work we show the results obtained for the optimization the instrumental and chemical conditions, and we can conclude that it is an electrochemically irreversible system with adsorptive reduction phemomenon. Under the best conditions we found a new method to analyze proteins with LODof 2 μg L−1and LOQof 5 μg L−1, a RSDless than 10% and a Erminor than 9%. Results of the application of this methodology to a real protein are included.

The incidence of Type 1 (insulin-dependent) diabetes mellitus was prospectively evaluated in Catalonia, Spain in patients up to 30 years of age during the period 1987–1990. The population at risk (0–29 years) consisted of 2,690,394 inhabitants (total population of Catalonia 5,978,638). All the cases were independently identified from four sources: endocrinologists, sales of blood glucose monitors and insulin pen injectors, diabetes societies and diabetic summer camps. The degree of ascertainment was 90.1 %. The overall observed incidence rate was 10.7 per 100,000 per year, being 11.5 per 100,000 per year in the 0–14 age group. The incidence in males (12.0 per 100,000 per year) was higher than in females (9.3 per 100,000 per year), with a male/female ratio of 1.36/l. The sex differences were only present in cases over 14 years of age. Age specific incidence rates per 100,000 per year were 4.4 (confidence interval 95%: 3.2–5.7) in the age group 0–4, 9.9 (8.5–11.4) in 5–9, 17.5 (15.7–19.4) in 10–14, 11.4 (9.9–13.0) in 15–19, 11.3 (9.7–13.0) in 20–24 and 8.5 (7.2–9.9) in 25–29. There was a seasonal onset pattern, with the highest incidence in winter (December–February). We conclude that the incidence of Type 1 diabetes observed in Catalonia during the period 1987–1990 is higher than that recently reported in other Mediterranean countries. This study offers the first standardized data on Type 1 diabetes incidence in Catalonia, including cases up to 30 years, and contributes to the knowledge of the epidemiology of diabetes in South Europe.