Table 4. Matrix effects.

	Plasma matrix
	K3 EDTA	K3 EDTA	K3 EDTA	K3 EDTA	K3 EDTA	Sodium heparin	Sodium heparin
Lot #	1	2	3	4	5	1	2
Ampicillin
Mean concentration	20,567	18,833	20,133	19,367	18,567	18,533	17,833
(ng/mL)
% deviation	14.26	4.63	11.85	7.59	3.15	2.96	-0.93
Piperacillin
Mean concentration	18,733	17,667	18,333	17,733	19,567	17,633	17,467
(ng/mL)
% deviation	4.07	-1.85	1.85	-1.48	8.70	-2.04	-2.96
Tazobactam
Mean concentration	18,133	18,933	18,300	19,000	17,767	17,500	18,133
(ng/mL)
% deviation	0.74	5.19	1.67	5.56	-1.30	-2.78	0.74
Meropenem
Mean concentration	6,722	5,989	7,533	6,233	6,353	5,511	5,756
(ng/mL)
% deviation	12.04	-0.19	25.56	3.89	5.89	-8.15	-4.07
Acyclovir
Mean concentration	7,289	6,089	6,756	6,189	6,927	6,444	6,056
(ng/mL)
% deviation	21.48	1.48	12.59	3.15	15.44	7.41	0.93
Metronidazole
Mean concentration	3,261	3,228	3,222	3,144	3,250	3,089	3,011
(ng/mL)
% deviation	8.70	7.59	7.41	4.81	8.33	2.96	0.37

K3 EDTA=potassium tri-phosphate ethylenediaminetetraacetic acid.