Calculate the mass of a stock solution needed to prepare a dilute solution.
Understanding and Using the Oligo Calculator
In chemistry, biology, and many scientific fields, it's common to prepare a less concentrated solution (a dilute solution) from a more concentrated stock solution. This process is fundamental for experiments, assays, and various applications where precise concentrations are crucial. The "Oligo Calculator" (short for Oligonucleotide calculator, though it applies broadly to dilutions) helps determine the exact volume of a stock solution needed to achieve a desired final concentration and volume of a dilute solution.
The Underlying Principle: Dilution Formula
The calculation is based on the principle of conservation of solute. The amount of solute in the stock solution used must be equal to the amount of solute in the final dilute solution. This is commonly expressed by the dilution formula:
C₁V₁ = C₂V₂
C₁: Concentration of the stock solution.
V₁: Volume of the stock solution needed (this is what the calculator solves for).
C₂: Concentration of the desired final (dilute) solution.
V₂: Volume of the desired final (dilute) solution.
How the Calculator Works
The calculator rearranges the formula to solve for V₁:
V₁ = (C₂ * V₂) / C₁
To use the calculator:
Stock Solution Concentration (C₁): Enter the concentration of your starting, more concentrated solution. Ensure you use the same units as for the final concentration (e.g., Molarity (M), percentage (%), mass per volume (g/mL)).
Desired Final Concentration (C₂): Enter the concentration you want your final solution to have. This MUST be in the same units as C₁.
Desired Final Volume (V₂): Enter the total volume of the final dilute solution you wish to prepare. Ensure the volume units (e.g., mL, L) are consistent.
The calculator will then output the volume (V₁) of the stock solution required. You will typically add this volume of stock solution to a suitable amount of solvent (e.g., water, buffer) to reach the final desired volume (V₂).
Units and Considerations
Consistency is Key: The most crucial aspect is ensuring that the units for concentration (C₁ and C₂) are identical, and the units for volume (V₂) are clear and the output V₁ will be in the same volume unit. For example, if C₁ is in Molar (M) and V₂ is in milliliters (mL), then C₂ must also be in Molar (M), and the calculated V₁ will be in milliliters (mL).
Percentage Concentrations: Percentage can be expressed in several ways (w/v – weight/volume, v/v – volume/volume, w/w – weight/weight). Be sure you know which type of percentage your stock solution uses and that it matches your intended final concentration. Common lab practice often implies w/v for solids dissolved in liquids or v/v for liquids mixed with liquids.
Solvent Volume: The calculated V₁ is the volume of the stock solution. The remaining volume to reach V₂ is made up of the solvent (e.g., water, buffer). Volume of solvent = V₂ – V₁.
Example Scenario
Let's say you have a 50% (w/v) stock solution of a reagent and you need to prepare 250 mL of a 5% (w/v) solution for an experiment.
C₁ = 50%
V₂ = 250 mL
C₂ = 5%
Using the formula V₁ = (C₂ * V₂) / C₁:
V₁ = (5% * 250 mL) / 50%
V₁ = (0.05 * 250 mL) / 0.50
V₁ = 12.5 mL / 0.50
V₁ = 25 mL
Therefore, you would need 25 mL of the 50% stock solution. You would then add solvent (e.g., water) to bring the total volume up to 250 mL. The volume of solvent added would be 250 mL – 25 mL = 225 mL.
Applications
This calculator is invaluable for researchers and technicians in fields such as:
Molecular Biology (e.g., preparing buffers, diluting reagents, making media)
Chemistry (e.g., titrations, creating standard solutions)
Biochemistry
Pharmacology
And any discipline requiring precise solution preparation.
function calculateOligo() {
var stockConcentrationInput = document.getElementById("stockConcentration").value;
var finalConcentrationInput = document.getElementById("finalConcentration").value;
var finalVolumeInput = document.getElementById("finalVolume").value;
var resultDiv = document.getElementById("result");
resultDiv.innerHTML = ""; // Clear previous results
// Input validation: Check if inputs are empty or non-numeric where expected
if (stockConcentrationInput === "" || finalConcentrationInput === "" || finalVolumeInput === "") {
resultDiv.innerHTML = "Please fill in all fields.";
return;
}
// Attempt to parse concentrations and volume, handling potential percentage signs and units
var C1_str = stockConcentrationInput.trim();
var C2_str = finalConcentrationInput.trim();
var V2_str = finalVolumeInput.trim();
var C1, C2, V2;
var C1_unit = ";
var C2_unit = ";
var V2_unit = ";
// — Parse C1 (Stock Concentration) —
var C1_match_percent = C1_str.match(/^(?:\d*\.?\d+)\s*(%)/i);
var C1_match_M = C1_str.match(/^(?:\d*\.?\d+)\s*(M)/i);
var C1_match_gmL = C1_str.match(/^(?:\d*\.?\d+)\s*(g\/mL)/i);
var C1_match_num = C1_str.match(/^(\d*\.?\d+)$/);
if (C1_match_percent) {
C1 = parseFloat(C1_str);
C1_unit = '%';
} else if (C1_match_M) {
C1 = parseFloat(C1_str);
C1_unit = 'M';
} else if (C1_match_gmL) {
C1 = parseFloat(C1_str);
C1_unit = 'g/mL';
} else if (C1_match_num) {
C1 = parseFloat(C1_str);
// If no unit is specified, we'll assume it's compatible with C2's unit if C2 also has no unit
} else {
resultDiv.innerHTML = "Invalid format for Stock Concentration. Use numbers with optional units like M, %, g/mL.";
return;
}
// — Parse C2 (Final Concentration) —
var C2_match_percent = C2_str.match(/^(?:\d*\.?\d+)\s*(%)/i);
var C2_match_M = C2_str.match(/^(?:\d*\.?\d+)\s*(M)/i);
var C2_match_gmL = C2_str.match(/^(?:\d*\.?\d+)\s*(g\/mL)/i);
var C2_match_num = C2_str.match(/^(\d*\.?\d+)$/);
if (C2_match_percent) {
C2 = parseFloat(C2_str);
C2_unit = '%';
} else if (C2_match_M) {
C2 = parseFloat(C2_str);
C2_unit = 'M';
} else if (C2_match_gmL) {
C2 = parseFloat(C2_str);
C2_unit = 'g/mL';
} else if (C2_match_num) {
C2 = parseFloat(C2_str);
} else {
resultDiv.innerHTML = "Invalid format for Final Concentration. Use numbers with optional units like M, %, g/mL.";
return;
}
// Unit consistency check for concentrations
if (C1_unit !== " && C2_unit !== " && C1_unit !== C2_unit) {
resultDiv.innerHTML = "Concentration units must match (e.g., both % or both M).";
return;
}
if (C1_unit === " && C2_unit !== ") {
resultDiv.innerHTML = "Stock concentration unit is missing or does not match final concentration unit.";
return;
}
if (C1_unit !== " && C2_unit === ") {
// If C1 has a unit but C2 does not, we assume C2 should match C1's unit
C2_unit = C1_unit;
}
// If both are unitless, we assume they are compatible.
// — Parse V2 (Final Volume) —
var V2_match_mL = V2_str.match(/^(?:\d*\.?\d+)\s*(mL)/i);
var V2_match_L = V2_str.match(/^(?:\d*\.?\d+)\s*(L)/i);
var V2_match_num = V2_str.match(/^(\d*\.?\d+)$/);
if (V2_match_mL) {
V2 = parseFloat(V2_str);
V2_unit = 'mL';
} else if (V2_match_L) {
V2 = parseFloat(V2_str) * 1000; // Convert L to mL for consistent calculation
V2_unit = 'L'; // Store original unit for output display
} else if (V2_match_num) {
V2 = parseFloat(V2_str);
// If no unit is specified, we default to mL for calculation and display.
// This is a common convention, but user should be aware.
V2_unit = 'mL (assumed)';
} else {
resultDiv.innerHTML = "Invalid format for Final Volume. Use numbers with optional units like mL, L.";
return;
}
// Check if parsed numbers are valid
if (isNaN(C1) || isNaN(C2) || isNaN(V2) || C1 <= 0 || C2 < 0 || V2 <= 0) {
resultDiv.innerHTML = "Please enter valid positive numbers for concentrations and volume.";
return;
}
// Ensure C1 is greater than or equal to C2 for a practical dilution
if (C1 = 1L, else mL.
if (V1 >= 1000) {
V1_result_unit = 'L';
V1 = V1 / 1000;
} else {
V1_result_unit = 'mL';
}
} else {
// If V2 was in mL (or assumed mL), keep V1 in mL.
V1_result_unit = 'mL';
}
var formattedV1 = V1.toFixed(4); // Format to a reasonable number of decimal places
resultDiv.innerHTML = "Required Stock Volume (V₁): " + formattedV1 + " " + V1_result_unit + "";
resultDiv.innerHTML += "(Add this volume of stock to solvent to reach a total final volume of " + V2_str + ")";
}