Table 2. Background-corrected mean mass fractions of the elements P, S, Cl, K, Ca, Mn, Fe, Ni, Cu and Zn in the cytoplasm of 5 fibroblasts from control case ‘LR’ and FRDA case ‘SL’.
| Control patient 'LR' (n = 5 cells) | Friedreich's ataxia patient 'SL' (n = 5 cells) | Student T-test (Equality of means) |
Levene's test (Equality of variances) |
||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Mean conc. cyt. | RSD | Backgr. | Normality | Mean conc. cyt. | RSD | Backgr. | Normality | 2-tailed Sign. | Sign. | ||
| (w%, ppm or μM) | (%) | (%) | (w%, ppm or μM) | (%) | (%) | 90% conf. int. | 90% conf. int. | ||||
| Mass fraction, % | P | 3.89 | 56 | 0.9 | ++ | 6.04 | 160 | 5.3 | ++ | 0.651 | 0.085 |
| S | 1.00 | 57 | 0.8 | + | 1.17 | 124 | 3.3 | ++ | 0.810 | 0.174 | |
| Cl | 1.40 | 52 | 10.4 | ++ | 1.28 | 107 | 73.1 | + | 0.875 | 0.373 | |
| K | 1.90 | 68 | 0.3 | ++ | 0.90 | 123 | 3.0 | ++ | 0.227 | 0.745 | |
| Mass fraction, | Ca | 518 (12900) | 37 | 1.2 | + | 296 (7390) | 63 | 7.6 | +++ | 0.102 | 0.958 |
| ppm (μM) | Mn | 12.0 (219) | 48 | 9.9 | + | 9.0 (163) | 52 | 59.6 | ++ | 0.386 | 0.38 |
| Fe | 39.3 (704) | 41 | 10.5 | ++ | 37.3 (669) | 63 | 60.1 | ++ | 0.883 | 0.756 | |
| Ni | 0.21 (3.6) | 47 | 10.4 | ++ | 0.16 (2.8) | 52 | 63.4 | ++ | 0.467 | 0.481 | |
| Cu | 12.1 (190) | 50 | 11.9 | ++ | 9.93 (156) | 52 | 74.1 | ++ | 0.565 | 0.449 | |
| Zn | 39.1 (598) | 63 | 2.1 | + | 21.4 (328) | 37 | 8.3 | +++ | 0.188 | 0.018 | |
| Ice layer thickness (μm) | 6.26 | 4 | + | 7.1 | 66 | 0.698 | 0.052 | ||||
Mass fractions are expressed in % for P, S, Cl, K; in ppm for Mn, Fe, Ni, Cu and Zn and values in parentheses in mM; relative standard deviation (RSD) is expressed in %. Only XRF spectra from detector no. 5 were used for quantification. Mean ice layer thickness (in μm) for each case (‘LR’ and ‘SL’) was determined using the K-Kα/Kβ method, its associated RSD value (in %) is indicated at the bottom of the table. ‘Share background’ represents the ratio (in %) of the background mass fraction to the background corrected mass fraction of the cytoplasm for a given element. ‘Normality’ refers to the extent to which a normal distribution is present among the concentration values of the different cells (‘+++’: perfect normality for all values, ‘++’: close to normal distribution, slight asymmetry or 1 outlier, ‘+’: 2 outliers or larger asymmetry). Student T-test verifies the equality of the mean concentration values of control case ‘LR’ and FRDA case ‘SL’ with 90% confidence interval; significance (or p) values closer to 0 (indicated in bold) indicate a significant difference at a 90% confidence interval (K, Ca and Zn). Levene’s test indicates the equality of variances of mass fractions for case ‘LR’ and ‘SL’; larger values (indicated in bold) indicate equal variances. Concentration values of elements discussed in the manuscript text are indicated in bold as well.