Быстрейший способ отделить число от букв

if (RegexPattern.IsFiltered(message))
{
    const string numbers = "0123456789.";
    var numberBuilder = new StringBuilder();
    var unitBuilder = new StringBuilder();
 
    foreach (char c in message)
    {
        if (numbers.IndexOf(c) > -1)
            numberBuilder.Append(c);
        else
            unitBuilder.Append(c);
    }
 
    double.TryParse(numberBuilder.ToString(), out double value);
    rawVoltage = value;
    Mv = unitBuilder.ToString() == "mV";
}

if (IsVoltage(s))
{
    Console.Write($"Voltage: {RegexVoltageValue().Match(s).Value}\t");
    Console.Write($"Unit: {RegexUnitValue().Match(s).Value}");
    Console.WriteLine();
}

[GeneratedRegex(@"\d+\.\d+")]
private static partial Regex RegexVoltageValue();
 
[GeneratedRegex(@"(m?V)$")]
private static partial Regex RegexUnitValue();

const string numbers = "0123456789.";
if (numbers.IndexOf(c) > -1)
            numberBuilder.Append(c);

string[] msg =
{
    "1.5224V", "1.5225mV", "1.526 mV", "1.527 V"
};
 
 
Stopwatch sw = Stopwatch.StartNew();
foreach (string s in msg)
{
    if (IsVoltage(s))
    {
        Console.Write($"{RegexVoltageValue().Match(s).Value}\t");
        Console.Write(RegexUnitValue().Match(s).Value);
        Console.WriteLine();
    }
}
 
sw.Stop();
Console.WriteLine(sw.ElapsedMilliseconds);
 
 
sw.Restart();
foreach (string s in msg)
{
    if (IsVoltage(s))
    {
        stringBuilder(s);
    }
}
sw.Stop();
Console.WriteLine(sw.ElapsedMilliseconds);

void stringBuilder(string s)
{
    const string numbers = "0123456789.";
    var numberBuilder = new StringBuilder();
    var unitBuilder = new StringBuilder();
 
    foreach (char c in s)
    {
        if (numbers.IndexOf(c) > -1)
            numberBuilder.Append(c);
        else
            unitBuilder.Append(c);
    }
 
    Console.Write(double.Parse(numberBuilder.ToString()) + "\t");
    Console.Write(unitBuilder.ToString());
    Console.WriteLine();
}

    if (IsVoltage(s))
    {
        Console.WriteLine($"{Conversion.Val(s)} {UnitValue().Match(s).Value}");
    }