Comment on Determination of Glycols in Biological Specimens by Gas

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We would like to comment on the article "Determination of Glycols in Biological Specimens by Gas Chromatography-Mass. Spectrometry" (1). The authorsĀ ...
Journalof AnalyticalToxicology,Vol. 27, April 2003

I

Letter to the Editor I

Comment on Determination of Glycols in Biological Specimensby Gas Chromatography-MassSpectrometry To the Editor:

We would like to comment on the article "Determination of Glycolsin Biological Specimens by Gas Chromatography-Mass Spectrometry" (1). The authors described a new, potent, and fast method for the determination of glycols (ethylene glycol, EG; 1,2-propanediol, 1,2-PD; 1,3-propanediol, 1,3-PD; 1,2-butanediol, 1,2-BD;2,3-butanediol, 2,3-BD; and 2-methyl-2,4-pentanediol, HXG) through silylation with N,O-bis(trimethylsilyl)trifluoroacetarnide (BSTFA).BSTFAhas the advantage over the classical condensation methods with alkyl- or arylboronic acid (2,3) in that glycolic acid, an important metabolite, polyglycols(diethylene glycol, DEG; triethylene glycol, TEG), and other products with hydroxyl-groups (e.g., gamma-hydroxybutyric acid, GHB) can also be measured. Moreover,the described BSTFAprocedure is easier to handle and produces clear mass spectra (MS). Using the same method but lowering the initial column temperature to 50~ we were able to obtain a significantly better separation of these glycols on a similar column (HP-5MS-ultra low bleed, 5% diphenyl-95% dimethylpolysiloxane).This allowed us to choose for more specific and often identical ions to quantitate the different glycols. This way, the sophisticated and unclear choice of ions as presented by Gembus et al. (1) (in Table I and Figure 2) can be avoided. For example, for the quantitation of diTMS DEG, the use of a fragment with rn/z 189 was not logical as it corresponds to M+-61. In addition, our di-TMS DEG MS was also different from the one reported. For di-TMS TEG (MW294) there was an impossible ion (rn/z 275) corresponding to M+-19 (Fluor). The MS of the di-TMS 1,2-PD showed fragments with mass-to-charge ratios of 231 and 263; however,the MW is only 220. Furthermore, the ion with ra/z 175 failed in our MS. For diTMS 1,3-PD,we also obtained a different MS than the one Table I. Selected Ions (re~z) and Retention Times reported. The MS of the di-TMS 1,2-butanediol too showed a For the Glycols fragment with a mass-to-charge ratio of 272 where the MW is 234. The MS of di-TMS 2,3-BD (MW234) showed a fragment Ionst Retention Time (rn/z 173) that we could not trace back in our MS, nor in the Derivative MW* (m/z) (min) literature, corresponding to M+-61. di-TMS EG 206 191,133, 103 6.16 Using a slightly modified derivatization method that worked di-TMS DEG 250 235, 133, 103 9.09 well for all glycols (BSTFAwith a drop of dimethylformamide), di-TMSTEG 294 161,279, 103 11.02 we easily obtained the di-TMS-derivativeof HXG. However, di-TMS 1,2-PD 220 205, 133, 103 6.40 using the method of Gembus et al. (1), we obtained the rnonodi-TMS 1,3-PD 220 205, 177, 130 7.14 TMS derivative,which was slowlybut completely converted to di-TMS 1,2-BD 234 219, 177, 131 7.40 the di-TMS derivative in a 24-h span, explaining the cited and di-TMS 2,3-BD 234 219, 131,117 6.85 rather high CVsfor inter- and intrarun assays for HXG. For dimono-TMS HXG 190 119, 175, 157 6.90 TMS, GHB we used the ions as reported by McCusker et al. (4). di-TM5 HXG 262 247, 205, 157 8.49 With some of the proposed modifications, the method of di-TMS GHB 248 233, 234, 235 9.06 Gembus et al. could be used in many laboratories. The changes di-TMS GHB-cl6 254 239, 240, 241 9.10 resulted in a better chromatographic separation of the ' Molecularweight. mentioned glycolsallowing the choice of more relevant ions for t Quantitationionsare underlined. quantitative and qualitative work (Table I). P. Van hee1, M. De Doncker1, N. Vrydags1, K. Schatteman I, W. Uyttenbroeck1, W. Lambert2, and H. Neels1 1Laboratorium voor Toxicologie,ACZAcampus Stuivenberg, Lange Beeldekensstraat 267, B-2060 Antwerpen, Belgie;and 2Laboratorium Toxicologie,Universiteit Gent, Harelbekestraat 72, B-9000 Gent, Belgi~

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Journal of Analytical Toxicology,Vol. 27, April 2003

References 1. V. Gembus, J.-P. Goull~, and C. Lacroix. Determination of glycols in biological specimens by gas chromatography-mass spectrometry. J. Anal ToxicoL 26:280-285 (2002}. 2. D.W. Robinson and D.S. Reive. A gas chromatographic procedure for quantitation of ethylene glycol in postmortem blood. J. Anal. ToxicoL 5" 69-72 (1981). 3. W.H. Porter and A. Auansakul. Gas-chromatographic determination of ethylene glycol in serum. Clin. Chem. 28:75-78 (1982). 4. R.R. McCusker, H. Paget-Wilkes, C.W. Chronister, B.A. Goldberger, and M.A. EISohly. Analysis of gamma-hydroxybutyrate (GHB) in urine by gas chromatography-mass spectrometry. J. AnaL ToxicoL 23:301-305 (1999).

The Authors' Reply: In their letter, P. Van hee et al. (1) have interestingly suggested two improvements to our method (2). These modifications are lowering the chromatograph oven starting temperature to 50~ instead of 80~ and dimethylformamide addition to N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA). The 100- and 500-mg/L levels for the eight glycols have now been tested in our laboratory. We were, in fact, able to obtain a significantly better separation of the glycol derivatives and a more clear mass spectra for most derivatives, but this does not change the ions of quantitation mass (re~z) as previously described for the eight glycols (2). However, we are not in agreement with some of the ions that are proposed by Van hee et al. (1) as they belong to other peaks. Moreover, many ions are common to a number of derivatives, m/z 103, 133, 205, and 219, but as their respective proportions are different it is useful to have the order of the ion intensities (Table l) in order that the eight glycols are clearly identified. This new, potent, and fast method, for the determination of glycols as well as glycolic acid, an important metabolite, and other products like gamma-hydroxybutyric acid (GHB), could be considered improved with the modifications proposed by P. Van bee et al. (I).

Table I. Selected Ions and Retention Times

Derivative

MW'

di-TMS EG di-TMS DEG di-TMSTEG di-TMS 1,2-PD di-l"M5 1,3-PD di-TMS 1,2-BD di-TMS 2,3-BD

206 250 294 220 220 234 234

mono-TMS HXG 190 di-TMS GHB-d6* 254

Ions~ (m/z)

Retention Retention Time (min) Time (min) 80~ 50~

191,103,133 4.1 103, 133, 235 8.8 103, t61. 279 14.1 221,133, 205, 103 4.2 115, 177, 205, 103 5.1 131, ~ 205 5.4 117, 190, 191,21_.~,9 5.2 133, 131 ~ 157, 175 4.8 239, 240, 206, 133 8.5

8.0 14.4 20.1 8.1 9.5 10.0 9.7 9.0 14.0

* Molecularweight. Quantitationionsareunderlined. =Internalstandard.

Jean-th'erre Goulld Laboratoire de Toxicologie et Pharmacoc&dtique Cliniques, Groupe Hospitalier du Havre, 76083Le Havre, France

References 1. P. Van hee, M. De Doncker, N. Vrydags, K. Schatteman, W. Uyttenbroeck, W. Lambert, and H. Neels. Comment on determination of glycols in biological specimens by gas chromatography-mass spectrometry. J. Anal. Toxicol. 27" pp-pp (2003). 2. V. Gembus, J.P.Goull~, and C. Lacroix. Determination of glycols in biological specimens by gas chromatography-mass spectrometry. J. Anal. Toxicol. 26:280-285 (2002).

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