Development of a field method for measuring manganese in welding fume A. Dale Marcyab and Pamela L. Drake*a Received 11th April 2007, Accepted 14th August 2007 First published as an Advance Article on the web 30th August 2007 DOI: 10.1039/b705252a Workers who perform routine welding tasks are potentially exposed to fume that may contain manganese. Manganese may cause respiratory problems and is implicated in causing the occurrence of Parkinson-like symptoms. In this study, a field colorimetric method for extracting and measuring manganese in welding fume was developed. The method uses ultrasonic extraction with an acidic hydrogen peroxide solution to extract welding fume collected on polyvinyl chloride filters. Commercially available pre-packaged reagents are used to produce a colored solution, created by a reaction of manganese(II) with 1-(2-pyridylazo)-2-naphthol. Absorbance measurements are then made using a portable spectrophotometer. The method detection limit and limit of quantification (LOQ) were 5.2 mg filterÀ1 and 17 mg filterÀ1, respectively, with a dynamic range up to 400 mg filterÀ1. When the results are above the LOQ for the colorimetric method, the manganese masses are equivalent to those measured by the International Organization for Standardization Method 15202-2, which employs a strong acid digestion and analysis using inductively coupled plasma-optical emission spectrometry. Introduction that chronic exposure to elevated manganese levels in the workplace results in increased respiratory problems.11–13 Welders may be exposed to a wide variety of hazardous In the United Stated, there are currently three workplace 1,2 substances while performing routine welding tasks. The exposure limits for manganese. The National Institute for fume that is generated during welding is a complex mixture Occupational Safety and Health (NIOSH) recommended of metal oxides that condense from the gas phase to form very exposure limit (REL) for manganese is 1 mg mÀ3 as an 8 h 3 small particles. The composition of the fume depends upon time-weighted average (TWA), and 3 mg mÀ3 as a short-term the type of welding process used and the chemical composition exposure limit.14 The Occupational Safety and Health Admin- of the metals being joined. A wide variety of methods are used istration (OSHA) permissible exposure limit (PEL) is to join metals together. Some of the more common types are 5mgmÀ3 (ceiling limit).14 The American Conference of shielded manual metal arc welding (SMAW), gas metal arc Governmental Industrial Hygienists (ACGIH) has established welding (GMAW), and flux-cored arc welding (FCAW). In a threshold limit value (TLV) of 0.2 mg mÀ3 for manganese.15 FCAW and SMAW, fluxes are incorporated into the consum- In the current analytical methods for determining the 1,2 able electrodes to shield against atmospheric gases. Manga- quantity of manganese in welding fume, a sample of the nese may be present in both the flux material and the metal particles in workplace air is collected on polyvinyl chloride electrodes. (PVC) filters or mixed cellulose ester (MCE) filters mounted in Welding fume may contain irritants and can be toxic to the plastic cassettes. Samples are collected using a personal sam- respiratory system, possibly causing pulmonary edema, pling pump at a flow rate of 2 L minÀ1, over a period of 8 h. chronic bronchitis, emphysema, pneumonia, asthma, welder’s The sample is sent to an accredited laboratory for an analysis 4 lung, and metal fume fever. Manganese is one of the compo- of the total manganese content using strong acid digestion and nents of welding fume that may have serious effects on measurement by inductively coupled plasma-optical emission 1,5 health. Some studies have shown that welders exposed to spectrometry (ICP-OES).16,17 The process typically requires fumes that contains manganese may have an increased risk of 4–6 weeks from the time the samples are collected until the 6–8 developing Parkinson-like symptoms, while other studies results of the analysis are reported. With this turnaround time, 9,10 have found no linkage. These symptoms include a fixed it is difficult to relate work practices to exposure levels in a gaze, bradykinesia, postural difficulties, rigidity, tremor, dys- timely fashion. The ability to measure manganese in welding tonia, and decreased mental status. Other studies have shown fume within 24 h would allow managers, supervisors, and/or safety personnel to communicate exposure levels to workers and take corrective actions to reduce exposure. a The goal of this study was to develop a rapid field method US Department of Health and Human Services, Centers for Disease s Control and Prevention, National Institute for Occupational Safety for measuring manganese in welding fume. HACH method and Health, Spokane Research Laboratory, 315 E. Montgomery 814918 is a colorimetric method for determining manganese in Ave, Spokane, WA 99207, USA. E-mail: [email protected]; Fax: water and wastewater. By adapting this method, the manga- +1-509-354-8099 b North Idaho College, 1000 W. Garden Ave, Coeur d’Alene, ID nese is extracted from the filters and converted to the soluble 83814, USA. manganese(II) form. An ultrasonic bath is used to extract the fume into an acidic solution of hydrogen peroxide. After solution (SPEX CertiPrep standard solution in 2% nitric acid, dissolution, 1-(2-pyridylazo)-2-naphthol (PAN) indicator is Metuchen, New Jersey, USA) were used to prepare spiking, added to the solution; it combines with manganese to form standard, and calibration check solutions. Iron solutions at an orange-colored complex. The absorbance is then measured 1000 mg LÀ1 were prepared by dissolving analytical grade on a spectrophotometer. In order to ensure that the new ferrous ammonium sulfate (EM Science, Cherry Hill, New extraction procedure was accurate, precise, and compatible Jersey, USA) and ferric nitrate nonahydrate (JT Baker, with the HACHs method, a series of experiments were Mallinckrodt Baker, Inc., Phillipsburg, New Jersey, USA) in conducted to evaluate analytical recovery, stability, method deionized water (18 MO, Millipore Milli-Q Plus, Molsheim, detection limit, and interferences. France). Analytical grade manganese(IV) oxide was obtained from JT Baker (Mallinckrodt Baker, Inc., Phillipsburg, New Jersey, USA). Nitric, hydrochloric, and sulfuric acids were Experimental obtained from OPTIMA (Seastar Chemicals Inc., Pittsburgh, Air sample generation and collection Pennsylvania, USA). The 50% hydrogen peroxide solution, ascorbic acid powder pillows, alkaline cyanide reagent, and Welding fume samples were collected on PVC filters (37 mm, PAN indicator solution were obtained from HACHs 5.0 mm pore size, with cellulose backup pad, SKC, Inc., Eighty (Loveland, Colorado, USA). Four, Pennsylvania, USA) using a custom-made multiport sampler. The multiport sampler was connected to a high- volume (15 L minÀ1) air sampling pump (Gilian AirCon2, West Caldwell, New Jersey, USA) and it collected eight Experimental methods samples simultaneously with a measured flow rate of 1.7 (Æ0.1) L minÀ1 for each individual port. All welding was Acidic hydrogen peroxide extraction and colorimetric analysis performed on soft steel using SMAW. Three types of electro- The field method for measuring manganese in welding fume des were used: UTP 711B ( 1% Mn; Bohler Thyssen Weld- o was evaluated by measuring the recovery of manganese that ing, Stafford, Texas, USA); E11018-M ( 5% Mn; Hobart o was added to PVC filters in one of three ways. In the first Welding Products, Appleton, Wisconsin, USA); and ArcTec procedure, the PVC filters were placed into 15 mL centrifuge 41 (16% Mn; ArcTec Alloys Ltd, Calgary, Alberta, Canada). tubes and solid manganese(IV) oxide was weighed directly onto Materials and equipment the filters. In the second method, known concentrations of manganese(II) in solution were pipetted onto the PVC filters in For some experiments, the PVC filters were placed into 15 mL the 15 mL centrifuge tubes. In the third technique, welding centrifuge tubes (Falcon, Becton-Dickinson, Franklin Lakes, fumes were collected on PVC filters in cassettes using a New Jersey, USA). The addition of reagents and deionized multiport sampler with a high-volume pump. water was performed with a mechanical pipette (Rainin In- The filters were then analyzed using the colorimetric method strument Company, Inc., Franklin Lakes, New Jersey, USA). as follows. The cassettes were opened and the filters were A vortex mixer (Barnstead International, Dubuque, Iowa, transferred to 15 mL centrifuge tubes. Two millilitres of USA) was used to mix the samples prior to extraction in the deionized water were added, followed by 0.5 mL of 6 M ultrasonic bath (117-V, 50 Hz, Crest Ultrasonics, Trenton, sulfuric acid and 3.0 mL of 3% hydrogen peroxide. The tubes New Jersey, USA). An aliquot of the extraction solution was were capped and the contents were mixed using a vortex mixer, s transferred to a HACH 25 mL sample cell (2.0 cm path ensuring that the filters were completely submerged in the length) with cap (Loveland, Colorado, USA) and diluted to extraction solution. The centrifuge tubes were placed in an s 10 mL. After the HACH reagents were added, the absor- ultrasonic bath and the filters were extracted for 30 min. In bance was measured using a DR/2400 spectrophotometer order to allow for complete dissolution of the manganese, the s (HACH Company, Loveland, Colorado, USA). samples were allowed to set in the acidic hydrogen peroxide For other experiments, the PVC filters were placed into extraction solution for a minimum of 2 h before analysis. After 25 mL beakers (Fisher Scientific, Hampton, New Hampshire, extraction, 4.5 mL of deionized water was added to the USA) and sequentially digested with concentrated nitric and centrifuge tubes and the contents were mixed using the vortex hydrochloric acids on a hot-plate (VWR International, Inc., mixer. An aliquot of the extraction solution in each of the West Chester, Pennsylvania, USA).