Page:NIOSH Manual of Analytical Methods - 7908.pdf/3

 NON-VOLATILE ACIDS (Sulfuric Acid and Phosphoric Acid): METHOD 7908, Issue 1, dated 20 May 2014 - Page 3 of 5

solution (0.27 M Na2CO3  0.03 M NaHCO3), rinse material from the inside surfaces of the cassette into the vessel. Add additional extraction solution into the vessel until a final volume of 5 mL is reached. 4.	Submit at least three field blanks for each set of samples collected per day. Handle these in the same way as the field samples; i.e., place each filter into a vessel, add 5 mL of eluent solution and ship it to the lab along with the remaining samples. 5.	Refrigerate all samples that are to be stored overnight (or longer) prior to shipment to the laboratory. Ship all samples to the laboratory in accordance with established chain-of-custody procedures [11]. 6.	Refrigerate the samples (4 °C) immediately upon receipt at the lab until ready for analysis. 7.	Analyze samples within 4 weeks of receipt. SAMPLE PREPARATION: 8.	Remove sample vessels from storage and bring them to room temperature. 9.	Sonicate the samples in an ultrasonic bath for at least 15 minutes and allow to cool for at least 30 minutes. 10.	Using 5-mL syringes, filter each sample extract solution through a PTFE filter into clean plastic vessels or into autosampler vials (if autosampler used). CALIBRATION AND QUALITY CONTROL: 11.	Through dilution of the calibration stock solution in eluent solution, prepare calibration working standard solutions covering the range of approximately 0.2 to 8 mg/L of sulfate and phosphate. Store working standards in tightly sealed polyethylene bottles. Prepare fresh working standards weekly. 12.	Calibrate the ion chromatograph with at least six working standards covering the range of 0.2 to 8 mg/L of sulfate and phosphate ion per sample by preparing a calibration graph of anion peak height (mm or µS [micro siemens]) vs. concentration (mg/L). 13.	Analyze working standards together with samples, reagent blanks and field blanks at a frequency of at least 1 per 20 samples (3 minimum of each). MEASUREMENT: 14.	Set the ion chromatograph to desired eluent flow rate, e.g.,1.5 mL/min, and column pressure, e.g., 1.1 x 105 kPa, and other conditions as specified by the instrument manufacturer. 15.	Inject a sample aliquot, e.g., 50-µL, into the chromatograph, and measure the peak heights of the phosphate and sulfate peaks (at retention times of about 9 min and 11.6 min, respectively). If the peak height exceeds the linear calibration range, dilute with eluent, reanalyze and apply the appropriate dilution factor in calculations. CALCULATIONS: 16.	Calculate the mass concentration of each anion, C (mg/m3), in the air volume sampled, V (L): (C 1*V 1 * Fd ) − (C 0*V 0 ) C ={ } * Fc V where: C = mean concentration, in mg/L, of anion in the field blank test solutions; 0 C = concentration, in mg/L, of anion in the sample test solution; 1 V = volume, in liters, of the air sample; V = volume, in mL, of the field blank test solutions; 0

NIOSH Manual of Analytical Methods (NMAM), Fifth Edition