Page:NIOSH Manual of Analytical Methods - 5524.pdf/6

METALWORKING FLUIDS (MWF) ALL CATEGORIES: METHOD 5524, Issue 2, dated 29 December 2014 - Page 6 of 10

fluid, from 51 µg to 189 µg for the semi-synthetic fluid, and from 102 µg to 420 µg for the synthetic fluid. For those weights of all four fluids spiked at levels ≥ 200 µg, the relative standard deviation was estimated to be 4% for the total weight procedure and 5% for the extraction procedure. If the sampling imprecision of 5% is included, these estimates become 6% and 7% respectively for the total weight and extraction procedures. Limits of quantitation, estimated from blanks carried through the entire analytical procedure, were 30 µg for the weighing technique and 60 µg for the extraction technique. No estimate of the bias was available [4]. The filters are desiccated to remove excess water from water-based MWF samples. In a more rigorous test of this method for a 79-plant survey [2], the average limits of quantitation were estimated to be 0.1 mg for both the total and extracted weight procedures. However, there was high variability in these estimates for the sites sampled. The upper 95% confidence limit for the LOQs for both the total weight and extracted weight measurements was 0.3 mg. In order to assess the effectiveness of the extraction step, a secondary extraction of the most heavily-loaded filters obtained in this survey was conducted; on average, less than 5% of the sample weight was removed during the second extraction, indicating that the majority of extractable material had been removed during the first extraction. Samples were refrigerated upon receipt at the laboratory [2,10]. During the 79-plant survey, all thoracic sampling was conducted with a BGI Mdl 2.69 Thoracic sampler. This sampler has a thoracic cut point of 10 µm at 1.6 L/min. The stability of quality assurance (QA) samples, spiked separately with a straight, a soluble, a semi-synthetic, and a synthetic fluid, indicated that the QA samples all lost weight according to simple linear decay equations. This loss in weight was likely due to evaporation of the spiking solvent and water (for soluble, semi-synthetic and synthetic MW fluids.) These decay equations were used to estimate the amounts expected to be reported for QA filters by the performing laboratory. For storage periods ranging from 17 to 26 days, the total weight of samples recovered for all QA samples were greater than or equal to 80% of those expected from the decay equations. For these QA samples, the fractions extracted of all four fluid types were greater than or equal to 90%. The binary solvent extraction step has been added to assure complete extraction of MWF components that may be incompletely removed by the ternary blend. In addition, the binary solvent extends the procedure to samples that contain ternary blend-soluble fluids co-mingled with ternary blend-insoluble fluids, e.g., Glacier (Solutia Inc.) Tests of the extraction of five MWF (including Glacier) showed that extraction efficiencies using the ternary blend in combination with the binary blend were comparable to those reported in reference 1 using the ternary blend alone (FE greater than 90 %; CV less than 0.10). The binary solvent extractant liquor obtained from the Glacier samples generally contained potassium and phosphorous at levels approximately expected for the mass spiked onto the filters. The binary solvent extracts of the four other test fluids were analyzed for sodium, potassium or boron marker elements. Sodium was present in the extract of the soluble fluid at greater than background levels. The boron marker was not detected in the extract from the semi-synthetic fluid. The potassium marker was not detected in the extract from the synthetic fluid [5]. This method was further evaluated in a six-laboratory round robin study using synthetically generated atmospheres of an aerosol of a soluble MWF at the 0.5 mg/sample level. The data were evaluated according to ASTM standard E691-99. Pooled estimates of the total coefficients of variation were 0.13 for both the total and extracted weight samples. Overall there was no significant bias in the results. LOQs were comparable to those reported above [11]. REFERENCES: [1] Health and Safety Executive (HSE), United Kingdom [2003]. MDHS 95/2, Measurement of personal exposure of metalworking machine operators to airborne water-mix metalworking fluid. [http:// www.hse.gov.uk/pubns/mdhs/pdfs/mdhs95-2.pdf ] Website accessed March 25, 2013.

NIOSH Manual of Analytical Methods (NMAM), Fifth Edition