Additional References shown below. A listing of PDF documents from ASMS (American Society of Mass Spectrometry) relating to TiO2 use for phosphopeptide enrichment can be found here.

Phosphopeptide extraction

• A. Schlosser, J. T. Vanselow, and A. Kramer,
  “ Mapping of phosphorylation sites by a multi-protease approach with specific phosphopeptide enrichment and NanoLC-MS/MS analysis ”,
  Analytical Chemistry 2005 Aug 15;77(16):5243-50.
• M. W. H. Pinkse, P. M. Uitto, M. J. Hilhorst, B. Ooms, and A. J. R. Heck,
  “ Selective isolation at the femtomole level of phosphopeptides from proteolytic digests using 2D-NanoLC-ESI-MS/MS and titanium oxide precolumns ”,
  Analytical Chemistry 2004 Jul 15;76(14):3935-43.
• I. Kuroda, Y. Shintani, M. Motokawa, S. Abe, and M, Furuno,
  “ Phosphopeptide-selective Column-switching RP-HPLC with a Titania Precolumn ”, Analytical Sciences 2004 Sep;20(9):1313-9.
  PDF Available Here
• I. Kuroda, M. Motokawa, T. Fukaya, and M, Takahashi,
  “ Selective Detection of Phosphopeptides by Using 2-dimentional Capillary HPLC/MS ”, Poster made in 2004 for external release by GL Sciences inc. PDF. file is available.

• M. R. Larsen, T. E. Thingholm, O. N. Jensen, P. Roepstorff, and T. J. D. Jorgensen,
  “ Highly selective enrichment of phosphorylated peptides from peptide mixtures using titanium dioxide microcolumns ”, Molecular & Cellular Proteomics 2005; 4: 873-886.
• Yasuhiro Hirano, Masashi Segawa, Fumiko S. Ouchi, Yoshio Yamakawa, Kazuhiro Furukawa, Kunio Takeyasu, and Tsuneyoshi Horigome1
  "Dissociation of Emerin from Barrier-to-autointegration Factor Is Regulated through Mitotic Phosphorylation of Emerin in a Xenopus Egg Cell-free System"
  J. Biol. Chem., Vol. 280, Issue 48, 39925-39933, December 2, 2005
  

Phosphosugar extraction

• Y. Sekiguchi, N. Mitsuhashi, Y. Inoue, H. Yagisawa, and T. Mimura,
  “ Analysis of sugar phosphates in plants by ion chromatography on a titanium dioxide column with pulsed amperometric detection ”, Journal of Chromatography A 2004 Jun 11;1039(1-2):71-6.
• Y. Sekiguchi, N. Mitsuhashi, and T. Mimura, “ Sugar Phosphates Changes in Arabidopsis in Response to Phosphate Nutrition Measured by Improved Ion Chromatography with Pulsed Amperometric Detection Combined with a Titanium Dioxide Column ”, Plant Biotechnology 2004 21(2):143-150.

• T. Ishiwata, K. Takai, H. Okada and K. Ohashi, “ ANALYSIS OF PHOSPHORUS-CONTAINING AMINO CID-TYPE HERBICIDES AND THEIR METABOLITES IN HUMAN BLOOD BY EXTRACTION WITH A TITANSPHERE TiO COLUMN AND CAPILLARY ELECTROPHORESIS ”, Jpn J Forensic Toxicol, Vol 22, No.1, 2004:7-12.

• Y. Kimura, S. Shibasaki, K. Morisato, N. Ishizuka, H. Minakuchi, K. Nakanishi, M. Matsuo, T. Amachi, M. Ueda, and K. Ueda, “ Microanalysis for MDR1 ATPase by high-performance liquid chromatography with a titanium dioxide column ”, Analytical Biochemistry 2004 Mar 15;326(2):262-6.