Matrix effects

50

Reagent

Well

Figure 3. Mass of white phosphorus (pg) detected by

headspace SPME vs. aqueous concentration over range

of 0.0072 to 0.144 g/L. Lines represent least squares

White Phosphorus Concentration (g/L)

Table 4. Regression coefficients for linear calibration models of

white phosphorus (pg) detected by headspace SPME vs. aqueous

concentration over range of 0.0072 to 0.144 g/L.

Zero-intercept

Model* with intercept

Model through origin

hypothesis

Water

Lack of fit

Calculated

†

F††

matrix

Slope Intercept

F ratio

Slope F ratio**

Reagent grade

226

0.0067

0.15

226

0.11

0.00014

Well

272

0.42

0.16

268

0.16

0.26

Pond

280

0.27

0.88

278

0.71

0.21

Salt marsh

230

0.41

0.24

234

0.25

0.41

* y = mx + b, where y = mass of WP (pg) and x = aqueous WP concentration

(g/L)

† Critical F0.95 (3,5) = 5.41

** Critical F0.95 (4,5) = 5.19

†† Critical F0.95 (1,8) = 5.32

(Table 4). Higher concentrations were beyond the

Table 5. White phosphorus mass (pg) de-

tected by headspace SPME for replicate

linear range of the detector. The slopes for the re-

0.144 g/L aqueous standards prepared in

gression models for the four different waters were

four water matrices and analyzed on the

not compared statistically because the data were

same day.

not generated on a single day; however, they ap-

peared to be similar.

White phosphorus mass (pg)

Rep

Reagent Well

Pond Salt marsh

Matrix effects

1

31.8

36.5

41.3

39.6

To confirm the similarity in response (mass of

2

35.8

39.1

31.5

32.1

3

37.6

32.9

36.7

33.1

white phosphorus detected by headspace SPME)

4

32.9

36.2

36.6

34.3

among the four different matrices, five replicate

5

32.3

34.1

35.6

36.8

0.144-g/L aqueous standards were prepared for

Mean

34.1

35.8

36.3

35.2

each matrix and analyzed on a single day. The

Std dev

2.5

2.4

3.5

3.0

% RSD

7.4%

6.8%

9.6%

8.6%

means of the responses obtained (Table 5) were

compared by ANOVA and were not significantly

Mass (pg)

237

249

252

244

Conc. (g/L)

different (p = 0.65) despite the fairly wide range

6