Cespón Romero, Rosa Mª
Department of Analytical Chemistry, Nutrition and Bromatology / Faculty of Chemistry/ University of Santiago de Compostela / Av. de las Ciencias, s/n/15782 Santiago de Compostela, Spain
34 981563100/ qncayebi@usc.es
Yebra Biurrun, Mª del Carmen
Department of Analytical Chemistry, Nutrition and Bromatology / Faculty of Chemistry/ University of Santiago de Compostela / Av. de las Ciencias, s/n/15782 Santiago de Compostela, Spain
34 981563100/ qncayebi@usc.es
ABSTRACT
The determination of nickel in workplace air involves a digestion procedure for the cellulose-ester membrane filter with concentrated acids. This is a time-consuming procedure, which also is prone to contamination or analyte loss. Besides, it has special precautions to be performed because the special care for acids handling and the health risk to the analyst caused by the vapors produced during the acid digestion. In this work a simple and rapid automatic ultrasound-assisted extraction system coupled to a flow injection manifold is presented. The method is employed for the determination of nickel in real metal fume samples from welding operations.
Key words
Nickel, workplace air, atomic absorption spectrometry
INTRODUCTION
The welding exposure is unique, there is no material from any other source directly comparable to the composition and structure of welding fumes. It was considered that welding is one of the most hazardous occupations. There are several reasons why welding is a dangerous occupation: (a) there are a multiplicity of factors that can endanger the health of a welder, such as heat, burns, radiation, noise, fumes, gases, electrocution, and even the uncomfortable postures involved in the work; (b) the high variability in chemical composition of welding fumes which differs according to the workpiece, method employed, and surrounding environment; and (c) the routes of entry through which these harmful agents access the body. Common chemical hazards include metal particulates and noxious gases [1].
The particulates and gases generated during welding are considered to be the most harmful exposure in comparison with the other byproducts of welding. The fume refers to the solid metal suspended in air, which forms when vaporized metal condenses into very small particulates. The vaporized metal becomes oxidized when it comes in contact with oxygen in air, so that the major components of the fume are oxides of metals used in the manufacture of the consumable electrode wire fed into the weld. Some metal constituents of the fumes may pose more potential hazards than others, depending on their inherent toxicity [2].
Nickel is one of the most common welding fume components because it is a component of many alloys and it is present in stainless steel. Inhaled nickel tends to accumulate in the nasal mucosa and lungs. Furthermore, this is a potentially carcinogenic metal found in fumes from the welding of nickel-plated mild steel, and stainless steel and high-strength low-alloy steel electrodes. Nickel oxide has been found to be carcinogenic in laboratory animals. Irritation of the respiratory tract has occurred in stainless steel welders. Other studies have indicated that stainless steel welding fumes containing nickel are potentially mutagenic. Epidemiological studies suggest that stainless steel welders have an increased risk for developing lung cancer due to elevations in nickel. However, this elevated risk has not been definitively shown to be associated with exposure to specific fume components and processes of welding [3-4]. Therefore, the health hazards of nickel require protection of the workers and have an appropriate analytical methodology for regular nickel monitoring in the workplace. The occupational exposure limits (VLA) for metallic nickel, for soluble nickel compounds and for insoluble nickel compounds are 1, 0.1 and 0.2 mg/m3, respectively [5].
Nickel proceeding from welding fumes has been determined by radiochemical [6] and x-ray fluorescence [7], but atomic absorption spectrometry (AAS) and inductively coupled plasma atomic emission spectrometry (ICP-AES) are the major routine analytical techniques owing to the combination of many advantages, such as high sensitivity and selectivity, good accuracy, adequate precision, etc. [8-10]. Therefore, these techniques are chosen by the Norma UNE 81-587-94 [11], by the accepted method of the Instituto Nacional de Seguridad e Higiene en el Trabajo (INSHT) [12], by the Manual of Sampling and Analytical Methods (Occupational Safety
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