Development of an N-methyl pyrrolidone based method of analysis for lead in paint

Abstract

A method suitable for the field determination of lead-containing paint by atomic absorption was developed. N-Methyl pyrrolidone (NMP) was used as a pretreatment to soften the paint samples. No heating, mechanical grinding, or other chemical treatments were necessary prior to final sample dilution. Addition of 2% nitric acid was sufficient to dissolve the lead species in as little as 30 minutes. The total sample preparation time was 60 minutes. Using FAAS, ICP-MS, and portable ETAAS, the proposed method was found to give results equivalent to the NIOSH 7082 acid digestion method for a lead paint SRM and several laboratory samples. The proposed method used only two reagents (NMP and dilute nitric acid) to prepare the sample for analysis which makes it specifically suited for determinations performed outside of a traditional laboratory. The presence of NMP in solution required the use of an internal standard to avoid positive bias in ICP-MS analysis. FAAS showed a small negative bias from NMP in solution. Accurate ETAAS determinations required the use of a phosphate matrix modifier. Raman spectroscopy of acidic NMP solutions revealed that the NMP was not chemically degraded under the conditions used for lead determination. However, at higher acid concentrations, loss of the N-methyl was observed.