The phrase "although not detected" is correct and usable in written English.
It can be used to indicate that something was expected to be found or observed but was not.
Example: "The substance was present in the sample, although not detected by the standard testing methods."
Alternatives: "even if not found" or "despite being undetected".
Although not detected here, trace levels of 212Pb and 208Tl have been reported in Swiss cigarettes [28], and 212Pb and 212Bi levels have been quantified [29] in Iraqi cigarettes at 6 9 and 9.9 17 mBq/g, respectively (Table 3).
Although not detected by immunofluorescence, cytoplasmic RHA was detected by mass spectrometry after enrichment by affinity chromatography methods that concentrate bound ligands.
Although not detected with the cp-23S-rDNA primers, the novel D206 symbiont was detected in 80% of the colonies from the D206 treatment after 3 weeks of exposure using D-specific qPCR primers and in 40% of the colonies after 5 weeks (Fig. 5B).
Although not detected by SDS-PAGE (Figure 2) due to their lower levels (100 3000 fold less) per virion, the viral polymerases (PA and PB) and non-structural proteins (NS) were detected within the spectrum of the whole vaccine digest (Figure 5).
Several heterocyclic compounds, although not detected in blood of healthy individuals [ 25], were quite abundant in blood of HD patients.
Similarly, MMP-1 levels were increased with BRAFV600E clone 21 (although not detected, with clones 7 and 8).
Up-regulation of compensatory subunits is also possible, although is not detected in all integrin-deficient cells (e.g., [69], [70]).
Although DVT was not detected on US, it is possible that the thrombus may have already embolized to the heart.
Although Vg was not detected until 8 h after E2 injection, its levels remained considerably low at around 0.03 μg/ml, even after 24 h.
Although differences were not detected (P > 0.05) for leaf chlorophyll content between the low and high VC rates, the low rate provided lower SPAD values compared to SFT.
Although histamine was not detected in any frozen samples, it accumulated rapidly in the previously frozen flying fish meat and once thawed and stored at 25°C.
