Page:NIOSH Manual of Analytical Methods - 8317.pdf/4

 ANILINE and @-TO LUIDIN E in urine: MET HO D 831 7, Issue 1, dated 15 M arch 200 3 - Page 4 o f 6 Calibration Solution

Volume of Stock Standard Solution (mL) 100 µg/L

Volume of M ob ile Phase

(µg/L)

100 0 µg /L

(mL)

1.

100

5.0

45.0

2.

80

4.0

46.0

3.

60

3.0

47.0

4.

40

2.0

48.0

5.

20

1.0

49.0

6.

10

5.0

45.0

7.

8

4.0

46.0

8.

6

3.0

47.0

9.

4

2.0

48.0

10.

2

1.0

49.0

The calibration solutions are stable a 4 oC for at least 2 w eeks. It is recom m ended to, prepare half of the calibration solutions fresh with each s et of sam ples. Alternate the use of duplicate primary stoc k stand ard s olutions so that every other se t of ca libration s olutions is m ade from the alternate stock standard solutions. 20. Analyze these 10 calibration solutions with each b atch of sam ples, so that every 2 field sam ples are bracketed with calibration solutions. 21. Because the calibration results are non-linear at low concentrations a quadratic curve should be prepared using data from the calibration solutions. Make the nominal mass of amine in pg injected the independent X variable and its peak height response the dependent variable of the calibration curve.

whe re a, b, and c are regress ion co efficients 22. Also, prepare quality control samples by collecting 1 L of fresh urine from unexposed non-smoking individuals, who are not taking medication. 23. To one liter of this fresh urine add 100 g of citric acid. 24. Add 25, 5, and 1 mL of stock 1000-µg/L standard solution to three 250-mL volumetric flasks, and dilute to the mark with the acidified urine. The nominal concentrations of these samples, i.e. 100, 20, and 4 µg /L, respectively, mus t be corrected for the averag e conce ntration of @-toluidine and aniline in the unfortified urine. 25. After each standard solution is added to urine, the fortified and unfortified urine is aliquoted into 10mL polypropylene scintillation vials and stored at -65 oC. 26. Analyze these quality control samples with each batch and maintain quality control charts. 27. Also, analyze at least one replicate sample from a previous batch with each new batch to assess precision with variable matrices. 28. Blind field splits are also recomm ended as a check on method precision.

MEASUREMENT: 29. Set the chromatograph according to manufacturer’s recomm endations and to the conditions given on page 1. Inject 50 :L of final solution in step 16. NIOSH Manual of Analytical Methods (NMAM), Fourth Edition