Page:NIOSH Manual of Analytical Methods - 5030.pdf/3

CYANURIC ACID: METHOD 5030, Issue 2, dated 15 August 1994 - Page 3 of 4 8. 9.

Filter the solution. If cyanuric acid is found on the PVC filter (steps 13 and 14), prepare additional sample solution by treatment of the interior surface of the front piece of the cassette filter holder with eluent. NOTE: The quantity of cyanuric acid collected on the interior surface of the front piece of the cassette filter holder may be significant (see EVALUATION OF METHOD). a. Use adhesive tape to secure in place the plug in the inlet of the front piece of the cassette filter holder. b. Add eluent (ca. 6 mL) to the front piece until about 95% of the interior surface is in contact with eluent. c. Place the front piece into an ultrasonic bath for 5 min. d. Transfer the solution from the front piece to a beaker, seal the mouth of the beaker with plastic film, and place the beaker into an ultrasonic water bath for 10 min. NOTE: Solid particles may be present in the solution after the first 5 min of ultrasonic agitation. Transfer of the solution to a beaker helps protect the solution from contamination.

CALIBRATION AND QUALITY CONTROL: 10.

11.

12.

Calibrate daily with at least six working standards over the range 0.1 to 250 mg cyanuric acid per mL of solution. a. Prepare a series of working standards in vials from calibration stock solution and eluent by serial dilution. NOTE: Working standards may be stored at -3 °C for at least 18 days without deterioration. b. Analyze together with samples and blanks (steps 13 and 14). c. Prepare calibration graph (peak area or height vs. µg of cyanuric acid). Determine recovery (R) at least once for each lot of PVC membrane filters used for sampling in the calibration range (step 10). Prepare three filters at each of five levels plus three media blanks. a. Place an aliquot of recovery stock solution onto a PVC filter which is situated in the back piece of a cassette filter holder. If the volume of the aliquot is greater than 15 µL, transfer the aliquot to the filter in portions which are about 15 µL in size. NOTE: Portions of stock solution will appear as beads on the filter. A maximum of about sixteen 15-µL portions of solution can be distributed on the filter. Thus, a maximum of about 400 mg of cyanuric acid can be applied to the filter with the recovery stock solution. A recovery stock solution which has a much higher concentration of cyanuric acid in water at room temperature can not be prepared because the limit of solubility of cyanuric acid in water at room temperature is about 2.5 mg/mL. If higher loadings are needed, allow the first portions to dry and repeat the process. b. Join the front piece of the cassette filter holder with the back piece. Remove the plug from the inlet. c. Carefully transfer the filter holder to a vacuum oven. d. Dry the filter at about 65 °C and 40 kPa (300 mm Hg). Filter will be dry in ca. 0.3 to 4.5 h. e. Prepare sample (steps 5 through 8) and analyze with working standards (steps 13 and 14). f. Prepare a graph of R vs. µg cyanuric acid recovered. Analyze three quality control blind spikes and three analyst spikes to ensure that the calibration graph is in control.

MEASUREMENT: 13.

14.

Set liquid chromatograph to manufacturer's recommendations and to conditions given on page 5030-1. Inject sample aliquot manually or with autosampler. NOTE: If peak area is above the range of the working standards, dilute with eluent, reanalyze, and apply the appropriate dilution factor in calculations. Measure peak area or peak height. NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94