Peak Shapes Interpretation And Troubleshooting; Refractive Index - Hach QC8500 Series 2 User Manual

Fia automated ion analyzer

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Troubleshooting

6.4 Peak shapes interpretation and troubleshooting

6.4.1.1 Common causes of refractive index

A refractive index usually shows up as a negative peak before the analyte peak. There

may be a small positive peak after the analyte peak. A refractive index is the difference in

density between the carrier and sample matrices

Figure 55 Refractive index

•

Overacidified samples: Some standard procedures recommend acidifying samples

to a pH of less than 2 for preservation. When working with flow injection analysis, this

can be interpreted as adjusting the pH just below 2 (e.g., 1.95). Most QuikChem

methods include recommendations for sample preservation.

•

Wrong carrier: Check the QuikChem method for the correct carrier for the analysis.

Make sure that the method used is intended for the matrix of the samples under

analysis. Verify the QuikChem method number in the methods list. Water methods

start with number 10, soil-extract methods start with number 12, etc.

(Figure

55).

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