diff --git a/src/gui/panels/step8_panel.py b/src/gui/panels/step8_panel.py
index b3f845a..74a084a 100644
--- a/src/gui/panels/step8_panel.py
+++ b/src/gui/panels/step8_panel.py
@@ -47,6 +47,7 @@ class Step8Panel(QWidget):
         self.builtin_formula_path = get_resource_path("waterindex.csv")
         self._formula_type_map: Dict[str, str] = {}
         self._formula_color_map: Dict[str, QColor] = {}
+        self._formula_coef_map: Dict[str, List[float]] = {}
 
         self.init_ui()
         self._auto_load_formulas()
@@ -195,6 +196,7 @@ class Step8Panel(QWidget):
                 return
 
             self._formula_type_map.clear()
+            self._formula_coef_map.clear()
             for _, row in df.iterrows():
                 name = str(row['Formula_Name']).strip()
                 if not name:
@@ -202,6 +204,17 @@ class Step8Panel(QWidget):
                 ftype = str(row.get('Formula_Type', 'ratio')).strip().lower()
                 self._formula_type_map[name] = ftype
 
+                # Parse Coefficient for concentration formulas
+                coef_str = str(row.get('Coefficient', '')).strip()
+                if coef_str:
+                    try:
+                        coeffs = [float(c.strip()) for c in coef_str.split(',') if c.strip()]
+                        self._formula_coef_map[name] = coeffs
+                    except Exception:
+                        self._formula_coef_map[name] = []
+                else:
+                    self._formula_coef_map[name] = []
+
             self.formula_list.clear()
             self.index_checkboxes.clear()
 
@@ -247,10 +260,16 @@ class Step8Panel(QWidget):
             name for name, item in self.index_checkboxes.items()
             if item.checkState() == Qt.Checked
         ]
+        # Build coefficient dict for selected formulas
+        formula_coefficients = {
+            name: self._formula_coef_map.get(name, [])
+            for name in selected
+        }
         return {
             'training_csv_path': self.training_data_widget.get_path(),
             'formula_csv_file': self.builtin_formula_path,
             'formula_names': selected,
+            'formula_coefficients': formula_coefficients,
             'enabled': self.enable_checkbox.isChecked(),
             'output_mode': self.mode_group.checkedId(),
         }