Formaldehyde: a comparative evaluation of four monitoring methods.

The performances of four formaldehyde monitoring devices were compared in a series of laboratory and field experiments. The devices evaluated included the DuPont C-60 formaldehyde badge, the SKC impregnated charcoal tube, an impinger/polarographic method and the MDA Lion formaldemeter. The major evaluation parameters included: concentration range, effects of humidity, sample storage, air velocity, accuracy, precision, interferences from methanol, styrene, 1,3-butadiene, sulfur dioxide and dimethylamine. Based on favorable performances in the laboratory and field, each device was useful for monitoring formaldehyde in the industrial work environment; however, these devices were not evaluated for residential exposure assessment. The impinger/polarographic method had a sensitivity of 0.06 ppm, based on a 20-liter air sample volume, and accurately determined the short-term excursion limit (STEL). It was useful for area monitoring but was not very practical for time-weighted average (TWA) personal monitoring measurements. The DuPont badge had a sensitivity of 2.8 ppm-hr and accurately and simply determined TWA exposures. It was not sensitive enough to measure STEL exposures, however, and positive interferences resulted if 1,3-butadiene was present. The SKC impregnated charcoal tube measured both TWA and STEL concentrations and had a sensitivity of 0.06 ppm based on a 25-liter air sample volume. Lightweight and simple to use, the MDA Lion formaldemeter had a sensitivity of 0.2 ppm. It had the advantage of giving an instantaneous reading in the field; however, it must be used with caution because it responded to many interferences. The method of choice depended on the type of sampling required, field conditions encountered during sampling and an understanding of the limitations of each monitoring device.

Collection and ion chromatographic determination of ammonia and methylamines in air.

A method is described for the collection of ammonia (NH3), monomethylamine (MMA), dimethylamine (DMA), and trimethylamine (TMA) from air and their subsequent determination by ion chromatography. Samples are collected with 800-mg silica gel sampling tubes at a flow rate of 1 L/min for 10 minutes or at 100 mL/min for up to 7.5 hours. Samples collected with sulfuric acid-treated tubes can be stored at room temperature for at least 21 days with no loss in recovery. Untreated samples can be stored in a refrigerator up to 32 days. The method has been validated from 2 to 50 ppm v/v when a 10 L air sample is taken. No loss in recovery was observed when sampling up to 23 L of air at 100% relative humidity. The recovery and total precision (95% confidence level) for NH3, MMA, DMA, and TMA were 91 +/- 12.5%, 93 +/- 10.3%, 92 +/- 9.6% and 84 +/- 17.6%, respectively.