DR5000 Accuracy Check using MR TOC

Hi All,

Need your expert opinion on the result below. Please help!

Using standard addition method, I'm perform accuracy check for Total Organic Carbon using DR5000 equipment. I finding the result is confusing. Please help me to understand the result below.

Sample use: DI water

Standard: 150 mg/L

0.1 spike reading: 5.651 mg/L

Recovery: 87.4%

0.2 spike reading: 13.046 mg/L

Recovery: 119.1%

0.3 spike reading: 18.24 mg/L

Recovery: 120.2%

Curve fit: 0.9882

I'm reading the result as my Recovery is out of place. I'm kinda confuse on the recovery of each spike. Also, basing the result to the expected output with respect to the reference below, it looks like not accurate. I did retest again and again but results are all confusing. Above is my best result and still confusing.

heres the reference: www.hach.com/fmmimghach?/CODE%3ADOC316.53.0109415635%7C1

Please advise what you guys seeing in my test results.

Thank you.

Josep