A research assistant is preparing a solution for a proteomics assay. She combines 300 mL of a 0.6 M NaCl solution with 700 mL of a 0.1 M NaCl solution. What is the final concentration of the mixed solution in millimolar (mM)?

["Title: How to Calculate Final NaCl Concentration in a Mixed Proteomics Assay Solution", "Meta Description: Learn how a research assistant combines two NaCl solutions to determine the final concentration for a proteomics assay. Discover the step-by-step calculation in millimolar (mM).", "---", "Introduction\nIn proteomics workflows, precise solution preparation is critical for reliable results. A common task is mixing NaCl buffer solutions of different concentrations and volumes. Understanding how to calculate the final concentration ensures accurate protein analysis. This article explains a real-world scenario where a research assistant combines NaCl solutions and determines the final concentration in millimolar (mM).", "The Problem\nA proteomics assay requires a final NaCl solution concentration of a specific millimolar (mM) level. To achieve this, a research assistant combines:\n- 300 mL of 0.6 M NaCl\n- 700 mL of 0.1 M NaCl", "The goal is to find the final concentration of the mixed solution, which determines whether it meets assay requirements.", "Step-by-Step Calculation\nTo calculate the final concentration after mixing, use the formula for dilution:", "[\nC_f = \frac{(V_1 \ imes C_1) + (V_2 \ imes C_2)}{V_1 + V_2}\n]", "Where:\n- (C_f) = final concentration (in M)\n- (V_1 = 300\ \ ext{mL},\ C_1 = 0.6\ \ ext{M})\n- (V_2 = 700\ \ ext{mL},\ C_2 = 0.1\ \ ext{M})", "Plug in the values:\n[\nC_f = \frac{(300\ \ ext{mL} \ imes 0.6\ \ ext{M}) + (700\ \ ext{mL} \ imes 0.1\ \ ext{M})}{300\ \ ext{mL} + 700\ \ ext{mL}} = \frac{(180\ \ ext{mmol}) + (70\ \ ext{mmol})}{1000\ \ ext{mL}} = \frac{250\ \ ext{mmol}}{1000\ \ ext{mL}} = 0.25\ \ ext{M}\n]", "Convert M to millimolar (mM):\n[\n0.25\ \ ext{M} = 250\ \ ext{mM}\n]", "Result\nThe final concentration of the mixed solution is 250 mM.", "---", "Why This Matters in Proteomics\nNaCl concentration is a key buffer component in many proteomics assays, including protein digestion, chromatography, and mass spectrometry input. Ensuring the correct ionic strength prevents protein aggregation and maintains assay reproducibility. A concentration of 250 mM is typical for certain buffer formulations and supports optimal enzymatic activity in digestions.", "Conclusion\nBy carefully calculating the weighted average of compiled solutions, the research assistant successfully prepares a NaCl solution at 250 mM. This method ensures precision in proteomics workflows where consistent buffer conditions are essential.", "Keywords: NaCl concentration formula, proteomics assay, solution mixing, millimolar calculation, buffer preparation, research assistant, protein analysis", "---", "For accurate proteomics results, always verify final concentrations using molarity calculations before proceeding with sensitive experimental steps."]