USGS Scientific Investigations Report 2010–5008 Use of Continuous Monitors and Autosamplers to Predict Unmeasured Water-Quality Constituents in Tributaries of the Tualatin River, Oregon

Table 3. Results of laboratory quality-assurance tests of autosamplers.

[Results in bold indicate potential contamination or carryover. Results in italics represent statistics or values not derived from the laboratory. Abbreviations: DI, distilled, deionized water; SRS, Standard Reference Sample; <, less than; N/A, not applicable]

Test sequence	Sampling method	Purpose	Medium	Replicate No.	Total suspended solids (mg/L)	Ammonium-nitrogen (mg/L as N)	Total Kjeldahl nitrogen(mg/L as N)	Total phosphorus (mg/L as P)	Soluble reactive phosphorus (mg/L as P)	Chloride (mg/L)	Comments
1	Direct pour (no autosampler)	Test of lab cleanliness	DI	1	N/A	< 0.01	< 0.05	< 0.025	0.009	< 0.25	Tests 1-3 are analysis of source materials, for comparison with results of samples collected with the autosampler in tests 4,6,7,8.
1	Direct pour (no autosampler)	Test of lab cleanliness	DI	2		< 0.01	< 0.05	< 0.025	< 0.005	< 0.25
	Median				< 0.01	< 0.05	< 0.025	0.007	< 0.25
2	Direct pour (no autosampler)	Test of lab accuracy	SRS, low	N/A	N/A	0.608	0.292	0.073	0.038	5.6
2	Expected value	Test of lab accuracy	SRS, low		N/A	0.592	0.592	0.072	0.037	5.3
3	Direct pour (no autosampler)	Test of lab accuracy	SRS, high	N/A	N/A	1.03	0.732	0.127	0.061	6.2
3	Expected value	Test of lab accuracy	SRS, high		N/A	0.986	0.986	0.156	0.051	5.9
4	Autosampler	Test of initial cleaning	DI blank	1	N/A	< 0.01	< 0.05	< 0.025	< 0.005	< 0.25
				2		< 0.01	< 0.05	< 0.025	0.007	< 0.25
				3		< 0.01	< 0.05	< 0.025	0.007	< 0.25
	Median					< 0.01	< 0.05	< 0.025	0.007	< 0.25
	Standard Deviation					0.000	0.000	0.000	0.004	0.0
5	Autosampler	Establish dirty tubing	Water + dirt	1	61	0.299	0.837	0.306	0.139	3.6	Quantity of dirt undefined. Sampled from bucket, mixed by hand.
				2	57	0.297	0.976	0.301	0.132	3.6
				3	48	0.299	0.96	0.294	0.133	3.6
	Median				57	0.299	0.96	0.301	0.133	3.6
	Standard Deviation				6.7	0.001	0.076	0.006	0.004	0.0
6	Autosampler	Test of cross contamination	DI blank	1	< 0.2	< 0.01	0.055	< 0.025	< 0.005	< 0.25	Tests carryover from high TSS samples in Test 5.
				2	< 0.2	< 0.01	< 0.05	< 0.025	< 0.005	< 0.25
				3	N/A	< 0.01	< 0.05	< 0.025	< 0.005	< 0.25
	Median				<0.2	<0.01	< 0.05	<0.025	<0.005	<0.25
	Standard Deviation				0.0	0.000	0.032	0.000	0.000	0.0
7	Autosampler	Test of dilution	SRS, high	1	N/A	1.02	0.943	0.141	0.053	6.2	Tests high SRS and possibility of dilution when sampling low concentration sources before high concentration sources.
				2		1.02	0.947	0.138	0.054	6.2
				3		1.04	0.964	0.143	0.055	6.2
	Expected value					0.986	0.986	0.156	0.051	5.9
	Median					1.02	0.947	0.141	0.054	6.2
	Standard Deviation					0.012	0.011	0.003	0.001	0.0
8	Autosampler	Test of cross contamination	SRS, low	1	N/A	0.616	0.591	0.069	0.039	5.6	Tests low SRS and possibility of cross contamination when sampling high-concentration sources before low concentration sources.
				2		0.62	0.609	0.069	0.039	5.6
				3		0.626	0.603	0.068	0.045	5.6
	Expected value					0.592	0.592	0.072	0.037	5.3
	Median					0.62	0.603	0.069	0.039	5.6
	Standard Deviation					0.005	0.009	0.001	0.003	0.0