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. 2021 Aug 30;175:216–225. doi: 10.1016/j.freeradbiomed.2021.08.237

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Fig. 1 — Different serum pretreatment methods and their effect on nitrite and nitrate measurements: (A) photographs of serum samples after pretreatment: (i) NaOH/ZnSO₄ precipitation, (ii) ethanol precipitation, and (iii) untreated. (B) photographs of the purge vessel during sample measurement after pretreatment i-ii. (C) measurement of nitrite using standard solutions (0, 0.2, 0.5, 1 μM from left to right) as a function of the three pretreatment methods i-iii. (D) measurement of nitrate using standard nitrate solutions (0, 20, 40, 80 μM from left to right) as a function of pretreatment methods i-iii.